Tetrapod Migration in Pangaea

Earth-Science Reviews 273 (2026) 105344
Contents lists available at ScienceDirect
Earth-Science Reviews
journal homepage: www.elsevier.com/locate/earscirev
Review Article
Late Paleozoic tetrapods in eastern Pangaea: when and how did they
get there?
Vladimir I. Davydov a,* , Spencer G. Lucas b, Eugeny V. Karasev c , Yunus Mamadzhanov d,
Mark D. Schmitz a
a
Boise State University, Dept. of Geosciences, Boise, ID 83725, USA
New Mexico Museum of Natural History, 1801 Mountain Road N. W., Albuquerque, NM 87104, USA
Borissiak Paleontological Institute of Russian Academy of Science, 123 Profsoyuznaya, Moscow 117647, Russia
d
Institute of Geology, Earthquake Engineering and Seismology, Dushanbe, Sadriddin Ayni Street, 299/2, Tajik Academy of Sciences, Dushanbe, Tajikistan
b
c
A R T I C L E I N F O
A B S T R A C T
Keywords:
Late Paleozoic
Tetrapods
Pangaea amalgamation
Paleogeography
Paleoclimate
Migration
CA-IDTIMS radioisotopic dates
The distribution and dispersal patterns of Late Paleozoic tetrapods remain poorly constrained. Diverse assemblages of Carboniferous and Permian tetrapods are well documented across western Pangaea, whereas in eastern
Pangaea (east of the Ural seaway), tetrapods only become abundant from the mid-Permian onwards. It is unclear
whether this discrepancy reflects imprecise chronostratigraphy or a genuine absence of Carboniferous–Early
Permian tetrapods in eastern Pangaea. Recently proposed vicariance models of tetrapod evolution incorporate
several questionable datasets, and existing palaeogeographic reconstructions of western–eastern Pangaean
connections remain controversial, requiring improved constraints and documentation. We report a CA–IDTIMS
radioisotopic age of 292.14 ± 0.14 Ma (Sakmarian) from one of the earliest tetrapods (discosauriscid) in the East
Pangaea localities in Tajikistan, that closely resembles discosauriscid assemblages from Kazakhstan. This age
supports the recently proposed model for the development of the Precaspian Isthmus during the Asselian–Sakmarian transition, interpreted as the first terrestrial corridor enabling tetrapod dispersal from western to
eastern Pangaea. Integrated analyses of regional paleogeography, tectonics, palaeoclimate, palaeobiogeography,
palaeofacies, and heavy-mineral provenance indicate that tetrapod migration pathways evolved through time:
the initial eastward dispersal occurred via the Precaspian Isthmus during the Asselian–Sakmarian transition,
whereas subsequent migrations (late Kungurian, late Roadian, Wuchiapingian, and Changhsingian) proceeded
both directly eastward from the East European Platform and through recurrent connections across the Precaspian
corridor.
Contents
1.
2.
3.
4.
5.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Late Paleozoic tetrapod footprints in North China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Cisuralian Tetrapod localities in Eastern Pangaea (east of the Uralian Seaway) and their chronostratigraphic constraints . . . . . . . . . . . . . . . . . . . . . . . . . 2
3.1.
Tadzhikistan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3.2.
Kazakhstan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3.3.
Russia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3.4.
North China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pangaea paleogeography and paleoclimate around the Urals seaway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Declaration of competing interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Supplementary data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
* Corresponding author.
E-mail address: vdavydov@boisestate.edu (V.I. Davydov).
https://doi.org/10.1016/j.earscirev.2025.105344
Received 5 June 2025; Received in revised form 9 November 2025; Accepted 24 November 2025
Available online 27 November 2025
0012-8252/© 2025 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Data availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
Xiashihezi Formation of the Roadian age (Liu et al., 2020).
The other footprints from the top of the Taiyuan Formation are those
of an amphibian (Limnopus sp.) and an amniote (likely Tambachichnium)
that were recently found and collected in a road cut near a suburb of
Beijing (Chen and Liu, 2024). It is now generally accepted that the
Taiyuan Formation exhibits diachronous boundaries across its distribution, reflecting a prolonged marine transgression lasting approximately 3.5 million years, progressing from east to west and from south to
northwest (Shen et al., 2022). In the type area of the Taiyuan Formation,
the fossil assemblage from the uppermost beds—including fusulinids
(Sphaeroschwagerina, Paraschwagerina) and the conodont Streptognathodus isolatus—indicates an early to middle Asselian age (Kong et al., 1996;
Shen et al., 2022). This biostratigraphic assignment is consistent with
CA-IDTIMS radioisotopic ages of 298.18 ± 0.32 Ma and 298.34 ± 0.09
Ma obtained near the top of the formation at the Wuda Coal Mine
(Schmitz et al., 2021; Wu et al., 2020). Conodonts from the upper part of
the Taiyuan Formation in the Yuhui and Yongcheng basins have been
interpreted as Artinskian in age based on the first appearance of
Sweetognathus whitei (Gao et al., 2005). The taxonomy and stratigraphic
range of this species remain debated among conodont specialists. Some
researchers assign S. whitei to the Artinskian (Chernykh et al., 2020;
Davydov, 2024; Kohn et al., 2019; Ritter et al., 2022), whereas others
place its first occurrence in the late Asselian to early Sakmarian (Shen
et al., 2022). In China, the latter interpretation is supported by a CAIDTIMS U–Pb age of 295.65 ± 0.08 Ma obtained near the top of the
Taiyuan Formation in the Yongcheng Basin, southeastern North China
(Yang et al., 2020). The footprints from the upper Taiyuan Formation in
the vicinity of Beijing, located approximately 300 km east of the Wuda
Coal Mine. Notably, the Beijing area lies on a similar longitude to the
Yongcheng Basin. Late Paleozoic paleogeographic reconstructions of
North China suggest that the Taiyuan Formation is more completely
developed in the Beijing area than at Wuda (Duan et al. 2021; Shao et al.
2024). Consequently, the chronostratigraphy of the tetrapod-bearing
horizons and associated footprints near Beijing requires further
improvement.
The Late Paleozoic is a critical time in the evolution of tetrapods as
well as their dispersal and migration patterns (Ahlberg and Milner,
1994; Bernardi et al., 2018; Brikiatis, 2020; Brocklehurst et al., 2018;
Pyron, 2011). These events were controlled by tectonics, paleogeography, and climate. The most extensive and complete record of Carboniferous—Permian tetrapods is in what was Euramerican Pangaea
(Fig. 1). In eastern Pangaea, a few localities of Devonian, Carboniferous
and Early Permian tetrapods are known in China and Australia (Lucas,
2022, 2005; Young, 2024; Zhu et al., 2002). However, the Devonian
tetrapods were either fish or terrestrial amphibians and were distributed
only in aquatic environments (Guo et al., 2023). Tetrapod fossils are
quite rare in the upper Paleozoic of eastern Pangaea (Central Asia,
Siberia, and North China).
It has been hypothesized that Carboniferous-early Permian tetrapods
are just undiscovered in this region (Efremov, 1951; Li and Reisz, 2019;
Lucas, 2005) and that they might have been there, because of the
occurrence of the tetrapod footprints in the upper Taiyuan Formation in
North China (Chen and Liu, 2024; Lucas and Ataabadi, 2010). However,
the geologic and stratigraphic information about these footprints requires improvement, Because of the diachronism of both lower and
upper boundaries of the Taiyuan Formation, the geologic and stratigraphic information about these footprints requires improvement (Li
et al., 2025; Shen et al., 2022; Yang et al., 2020).
Several early tetrapod localities have been documented in the
western part of eastern Pangaea (Ivakhnenko, 1981; Kuznetsov and
Ivakhnenko, 1981; Ryabinin, 1932). However, their age is uncertain and
suggested to be in the range from late Carboniferous through the late
Permian (Lopingian). The Permian tetrapods in North China are more
common, and their ages are mostly better constrained with some exceptions (Lucas, 2018; Lucas, 2005). The main question regarding the
late Paleozoic tetrapods of eastern Pangaea is when and how did they get
there? Are they still undiscovered, or was that part of Pangaea isolated
from the main center of tetrapod origination, which was located in
western Pangaea (North America, Central Europe, and the EastEuropean Platform) during the late Carboniferous and early Permian?
Is there an independent and polyphyletic origin of the tetrapods or did
they just disperse to eastern Pangaea from the west?
A recently proposed hypothesis suggested frequent pulses of tetrapod
migration from western Pangaea (East-European Platform and surrounding areas) because of periodic isolation (vicariance) due to global
sea-level fluctuation (Brikiatis, 2020). It was suggested that synapsid
evolution in eastern Pangaea was controlled by these climatic pulses,
and tetrapod diversifications coincided with global sea-level lowstands
(Brikiatis, 2020). We aim to scrutinize comprehensive data encompassing paleogeography, paleotectonics, stratigraphy, paleoclimate, and
ecology about late Paleozoic tetrapods to address these ideas. The
incorporation of recently obtained high-precision radioisotopic ages
from the tetrapod locality in Tadzhikistan significantly enhances our
understanding of these issues, providing distinct insights into the
emergence of the first Late Paleozoic tetrapods in eastern Pangaea.
3. Cisuralian Tetrapod localities in Eastern Pangaea (east of the
Uralian Seaway) and their chronostratigraphic constraints
No tetrapods are known in the Carboniferous and undoubtedly
earliest Permian in the entire area of eastern Pangaea, except the
tetrapod tracks in North China, the age of which is uncertain and
somewhat controversial. This tetrapod-free gap seems to appear due to
the existence of the Uralian seaway and the complete isolation of eastern
Pangaea from the rest of the supercontinent during this time. Also, only
rare tetrapod fossil localities of Guadalupian age are known in eastern
Pangaea. In the Late Permian the terapods in the region are abundant
(Fig. 1).
3.1. Tadzhikistan
Adrasman, Kurama Ridge 1. Ariekanerpeton sigalovi (Ivakhnenko,
2. Late Paleozoic tetrapod footprints in North China
Late Paleozoic tetrapod footprints are known from two localities in
North China. In Shanxi, a slab with the footprints of a large amniote,
which were considered Carboniferous, were collected in an abandoned
mine with no specific age data or stratigraphy, (Lucas and Ataabadi,
2010). Recently, however, these footprints were regarded as from the
2
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 1. Distribution of different ages of Paleozoic tetrapods within the recent geography. Data from PaleoDB https://paleobiodb.org/ (April 2023).
1981) found in the Sarytaipan Formation in Northern Tadzhikistan,
Sarytaipan hill. The Sarytaipan Formation conformably overlies the
Tavak Formation and comprises three units (see description below)
(Kolchin, 2004). The age of this formation was controversial and suggested to range from Late Cisuralian (Kungurian) to Lopingian
(Masumov et al., 1978). The new radioisotopic date (see below) suggests
a Sterlitamakian, Sakmarian (sensu stricto) age.1
Adrasman, Kurama Ridge 2, Discosauriscids and Lepospondyli
(Ivakhnenko, 1981) were found in Northern Tadzhikistan, Kiziltau, 10
km east from Sarytipan hill. The age of this locality is the same as the
Sarytaipan Fm. [40.659026◦ N 69.961828◦ E]
sandstone of the Krasnoyarsk Fm on the right slope of the Tom’ River,
across from Sheveli village (Ryabinin, 1932). At the same locality an
ulna of Dinocephalia has also been found [55.091886◦ N 86.338941◦ E].
The second locality with the bone of the reptile in the conglomerate
occur stratigraphically slightly lower than the Inostrancevia tooth, but
still in the Krasnoyarsk Fm (Ryabinin, 1932) [55.091886◦ N
86.338941◦ E]. The suggested age of the Krasnoyarsk Sandstone, a coal
free analogue of the Il’in Formation of the Kolchugin Series, is Kazanian
(Roadian) (Budnikov, 1996; Ryabinin, 1932; Vyushkov, 1953).
Tunguska Basin, Siberia.
Podkamennaya Tunguska River. The remains of Amphibia, possibly
Tungussogyrinus, have been reported from the Krivlyaki locality
(Efremov and V’yushkov, 1955) 35 km downstream from Oskoba
village, on the right slope of the river. The stratigraphic position and the
age are not precise. According to the geologic map, it might be either the
upper Pelyatkin Formation of Late Permian or Gagaryostrovsky Formation of latest Permian to earliest Triassic age [60.339365◦ N
100.014114◦ E] ((Kutumov et al., 1976).
Korbuchana River, left tributary of Nizhnyaya Tunguska River, 3.5
km from the mouth. Two meters above the coal-bearing Upper Permian
Degali Fm, within the lower Tutonchana Fm were found vertebrae, the
distal head of a tibia, a metacarpal bone, and rib fragments of Dicynodontia that compared with similar tetrapods from the upper Tatarian of
the Russian Platform. These fossils might belong to Lystrosaurus (?)
(Vyushkov and Emel’yanova, 1959). The age of the lower Tutonchana
Formation is latest Permian-earliest Triassic (Mogucheva, 2016)
[64.002370◦ N 95.428662◦ E].
The right bank of the Nizhnyaya Tunguska River near the Anakit
River, 113 km upstream from Tura city, 14 m above the base of the
upper Korvuchana Fm, in 10 cm thick yellowish dolomites with abundant fossils, including fishes and the tetrapod Tungussogyrinus (Efremov,
1939; Levitan, 1985), that belongs to the family Branchiosauridae
(Shishkin, 1998; Werneburg, 2009). The age of this fossil most probably
is earliest Triassic, but it also could be latest Permian (Orlova and
Sadovnikov, 2006) [64.111890◦ N 101.870660◦ E].
3.2. Kazakhstan
Tengiz basin, Kazakhstan, Tersakkan River. Tetrapods Labyrintodontia, Batrachosauria, Seymourimorpha, Cotylosauria, Diadectomorpha, Pelycosauria, and Gnorhimosuchus satpaevi (Efremov,
1951) were found in the lake deposits of the Keyma Formation; conchostracans and non-marine ostracods indicate a Kungurian-Ufimian
(Kungurian sensu lato) age (Litvinovich et al., 1977) [51.22322◦ N
67.48290 E◦ ].
Ili mega-synclinorium, South Kazakhstan, Kurty River basin (left
tributary of Ili River), Utegenia shpinari (Kuznetsov and Ivakhnenko,
1981) has been found in lake deposits of the Kugalin Formation with
flora suggests a Late Carboniferous-early Permian age (Salmenova and
Koshkin, 1990), but the phylogenetic proximity of Utegenia to other
discosauriscids (Klembara and Ruta, 2004) restrict it to an early Permian
age only [43.87276◦ N 75.97989◦ E].
3.3. Russia
Kuznetsk Basin, Siberia. One locality with a tooth fragment of (?)
Inostrancevia, Theriodontia (4.5 cm long) found in greenish-grey
1
The duration of the newly established Sakmarian stage (Chernykh et al.,
2020) reduced by 1.5 Myrs, and most of the former lower Sakmarian (Tastubian
Regional Stage) is now included in the Asselian (Davydov, 2024). To avoid the
confusion with the meaning of the two lower Cisuralian Stages in the International Geologic Time Scale, we suggest using these terms as Asselian sensu lato
and Sakmarian sensu stricto).
3.4. North China
The oldest Permian vertebrate of the Junggur basin of Xinjiang,
Urumqia, is known in the Lucaogou Fm and is thought to be middle
3
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Permian (Lucas, 2005). But, recently, it was considered to be Sakmarian
or Artinskian (Liu et al., 2022) This fauna is evolutionarily connected
with the earliest East Pangaean seymouriamorphs from Tajikistan and
Kazakhstan and may represent a link to the tetrapods whose footprints
were recently discovered in the upper Taiyuan Formation near Beijing.
(Chen and Liu, 2024).
Diverse tetrapods were collected from the Naobaogou Fm including
Daqingshanodon limbus, Turfanodon jiufengensis, the captorhinid Gansurhinus qingtoushanensis, the pareiasaur Elginia wuyongae, and three
therocephalians Shiguaignathus wangi, Jiufengia jiai, Caodeyao liuyufengi
of Lopingin age (Liu, 2021). The Naobaogou Formation is conformably
overlain by the andesite of the Dahongshan Formation, where the obtained U–Pb age is 277.3 ± 1.4 Ma (Li et al., 2018), that could suggest a
late Kungurian age of these tetrapods. We prefer Lopingian age of the
Naobaogou Fm because the tetrapod biostratigraphy is more reliable
than radioisotopic LA ICP-MS method that can produce discrepancies up
2–3 % (~10 Myrs in this case).
Roadian and post-Roadian tetrapods in China are thoroughly documented by (Liu et al., 2020). The data from China suggest an active
connection of middle-late Permian tetrapods between Europe, South
Africa, and China (e. g., (Duhamel et al., 2021; Liu et al., 2020; Suchkova
and Bakaev, 2024).
150 m thick (Kolchin, 2004). The Sarytaipan Member is interpreted as
lake sediments (Ivakhnenko, 1981). It was deposited in the lake of the
central part of the Adrasman caldera, which is ~5 km in diameter
(Tananaeva and Kochieva, 1983). Fifteen meters above the base of the
lower unit and about 3 m above the tetrapod- bearing horizon, a sample
of grey, fine-grained volcanic ash was collected. The sample was processed and studied in the Isotope Geology Laboratory (IGL) of Boise
State University https://www.boisestate.edu/earth-isotope (See Supplemental 18VD06_U-Pb). The sample 18VD-06, is a volcanic tuff:
Moderately abundant zircon crystals were extracted from sample 18VD06, comprising a homogeneous population of equant, prismatic zircon
crystals (aspects up to ≤2:1; ≤100 μm in long dimension). Crystals were
colorless and transparent, and in cathodoluminescence consistently
exhibited sector zoning superimposed upon weak oscillatory zoning (See
Supplemental 18VD06_U-Pb). Five chemically abraded grains yielded
concordant and equivalent U–Pb isotope ratios, with a weighted mean
206
Pb/238U date of 292.14 ± 0.14 (0.17) [0.35] Ma (MSWD = 0.31) (See
Supplemental 18VD06_U-Pb). This date is interpreted as the best estimate of the eruption and emplacement age of this volcanic tuff. This is a
correlative to the Sterlitamakian Regional Stage (i.e. Sakmarian sensu
stricto) of the Urals (Schmitz and Davydov, 2012). This means that
tetrapods had already appeared in Central Asia during the AsselianSakmarian transition.
4. U–Pb radioisotopic age of the tetrapod locality at Sarytaipan
hill, Karamazar, North Tadzhikistan
5. Pangaea paleogeography and paleoclimate around the Urals
seaway
The dated sample 18VD06 was collected at Sarytaipan hill
[40.672740◦ N 69.877083◦ E] within the lower unit of the Sarytaipan
Member (Kolchin, 2004) (Fig. 2). The member conformably overlies the
lavas of the Tavak Fm and consists of three units. The lower unit is thinly
bedded multicolored sandstone and siltstone with flora and tetrapod
remains. It starts with coarse-grained sandstone with gravel conglomerate at the bottom with a total thickness of 2.8 m. The rest of the succession is cyclic with 1–2 m rhythms of greenish-grey and grey fine
sandy to silty tuffites in 2–3 cm to 0.2 m scale beds. The horizon with the
skeleton occurs approximately 12 m above the base of the unit and is
enriched with ooids of swamp iron ore, and has a total thickness of 0–40
m. The middle unit is composed of acidic whitish and greyish tuffs and
lava 5–35 m thick, and the upper unit is reddish lava of rhyolites up to
69°49'48”
69°51’
69°53’24”
69°52'12”
40°41'16”
Sarytaipan Hills
18VD6
0
Pg
Cr2
1
2
3
4
5
6
7
8
9
10
11
500m
Sartash-sai
tsu
ai
Cha
Gu
s
ali
Paleogeography is one of the main controls on the distribution of
tetrapods. Terrestrial tetrapods follow favorable environments and climates (Benton, 2015). The sub-meridional Uralian seaway that connected the Paleo-Arctic and Paleo-Tethys basins was one of the most
important paleogeographic attributes of the landscape and paleoclimate
of Late Paleozoic Pangaea (Scotese, 2015)). The seaway that connected
the shelves along the East-European Craton, the Ural, and the PaleoTethys was the major oceanic gateway between the Paleo-Tethys and
Paleo-Arctic oceans (Fig. 3). The final collision of the Kazakhstania and
Siberian continents with sutured Laurentia and Gondwana is usually
considered to have caused the closure of the Uralian foredeep. Some
models suggest that the closing of the Uralian-Paleo-Tethys connection
40°40'30”
40°39'54”
12
Fig. 2. Geologic map of the Sarytaipan Hills area (from Kolchin, 2004). 1, Paleogene; 2, Upper Cretaceous; 3–5, Sarytaipan Formation, 3, lower unit - silisiclastics
and tuffs with tetrapods skeletons and flora; 4, middle unit - acidic tuffs and breccia; 5, upper unit - potassium trachirhyolite; 6, rhyolitic ignimbrites and tuffs of
Tavak Fm; 7, Carboniferous dacite tuffs; 8, Ordovician-Silurian slate; 9, granitoids; 10, faults; 11, rivers; 12 - sample collected for radioisotopic study.
4
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 3. Moscovian-Sakmarian paleogeography of the area of the continental bridge development between western and eastern Pangaea (modified from Davydov,
2018). The oceanic connection and lack of the continental bridge between Paleotethys and Paleo-Arctic during Moscovian-Asselian is demonstrated by the distribution dynamics of the Tethyan and Boreal fauna into the Precaspian, Urals, and Donets Basin. At the Asselian-Sakmarian transition and the emergence of the
Precaspian Isthmus, the Boreal and Tethyan faunal domains became completely isolated (Davydov, 2018). The Isthmus provided the first and permanent access for
tetrapods to disperse from western Pangaea to the east.
happened in the Moscovian (Lawver et al., 2011) or sometime within the
Bashkirian-Kasimovian (Cavazza et al., 2004; Stampfli et al., 2013).
Golonka (2011) proposed that the seaway was closed in the AsselianArtinskian and reopened in the Guadalupian. Most tectonic models of
the development of the Urals and in surrounding areas during PaleozoicMesozoic time imply the existence of the Uralian seaway until the end of
the Kungurian because of the early Permian marine fossils in the Precaspian and the Southern Ural regions. According to these models, the
end of the marine sedimentation and the accumulation of thick sabkha
evaporites in the Precaspian and along the Ural regions during the
Kungurian denote the complete closure of the Urals-Tethyan connection
(Brown et al., 1997; Cocks and Torsvik, 2007; Golonka, 2007; Nikishin
5
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
et al., 1996; Puchkov, 2010; Snyder et al., 1994; Ziegler, 1989; Zonenshain et al., 1990). Moreover, some paleogeographic models suggest the
existence of the seaway between the Paleo-Arctic and the Paleo-Tethys
until the Triassic (Blakey, 2011; Chumakov and Zharkov, 2002; Domeier and Torsvik, 2014; Scotese, 2015). The presence of the Uralian
seaway through the entire Permian and the appearance of the early
Permian tetrapods in the nearby areas to the east have been invoked to
support a vicariance model (geographical separation) in synapsid evolution (Brikiatis, 2020). However, the paleotectonics, paleogeography,
and paleoclimate in the region run counter to this model.
The analyses of the paleogeography of the entire East-European
Platform, Urals, Kazakhstan, and surrounding areas (Bykadorov et al.,
2003; Ignatiev, 1976; Kaz’min and Natapov, 1998; Miletenko and
Fedorenko, 2002; Nikishin, 2005; Pisarenko and Goncharenko, 2010;
Tikhomirov, 1984; Vinogradov, 1975) suggest the following. The
Kazakhstania and Siberia plates were completely merged during the
Middle Pennsylvanian. Marine sedimentation on the eastern margin of
Western Siberia ended during the early Bashkirian (Bogush et al., 1974)
and in the eastern margin of the Kazakhstania plate during the early
Moscovian (Bogush et al., 1976; Zhaimina, 2000). No post-late Moscovian marine sediments have been reported or are known in Western
Siberia and Kazakhstan (Fig. 3) (Yuferev, 1973).
Paleoclimate is the other major factor that directly controlled the
migration process. The paleogeography during the Permian was
reviewed in the previous chapter, so here we are briefly reviewing the
Permian global and regional paleoclimate. The knowledge of the global
late Paleozoic climatic pattern significantly improved in the last decade
thanks to high-precision CA-IDTIMS dating of and new studies in high
latitudes (Davydov et al., 2022) (Fielding et al., 2023; Griffis et al., 2023;
Isbell et al., 2021; Montanez and Poulsen, 2013; Montañez, 2022). The
late Paleozoic is known to be associated with one of the longest and
strongest of Earth’s ice ages, which strongly controlled the global and
regional climate (Montanez and Poulsen, 2013). The Permian is associated with several global glaciation-deglaciation cycles, most of which
are recognized in Gondwana (Fig. 4).
During the Pennsylvanian and Asselian the Ural paleo-basin was
directly connected with the Paleo-Tethyan ocean without any restrictions (Bykadorov et al., 2003; Miletenko and Fedorenko, 2002;
Nikishin, 2005). The best indicator of the free connection – the warmwater Large Benthic Foraminifers (LBF), i.e., fusulinids in the Southern Urals and Donets Basin – at species level are taxonomically the same
as in the Carnic Alps, Turkey, Iran, and Central Asia (Davydov, 2009,
1992; Davydov and Popov, 1986; Krainer and Davydov, 1998; Leven
and Davydov, 2001; Leven and Ozkan, 2004) (Fig. 3). The Northern
Caspian basin since the Shikhanian-Tastubian transition (latest Asselian
s. l.) (Chernykh et al., 2020; Davydov, 2024) was bounded in the south
by the trans-Eurasian tectonic belt, i.e., the Karpinsky Swell, that
extended from the Pripyat trough (Belorussia) to the MangyshlakTuarkyr system over several thousand kilometers, with its width varying from 150 to 250 km (Nikishin, 2005) (Fig. 5). Throughout the
Sakmarian (s.s.)-Artinskian the consolidated massif of the positive tectonic units (mountains) in the south in the Precaspian depression,
including the Karpinsky Swell, Scythian Orogen, Evksinian Orogen, and
Great Caucasus Orogen, exceeded a width of more than 600 km and an
overall 2–3 km height during the early-middle Permian (Stephenson and
Stovba, 2012) (Figs. 5B, 6). The Ural Mountains until Wordian time were
relatively low, and the main source of the siliciclastic input in the EastEuropean Platform until that time was from the Baltic (Arefiev, 2011;
Mizens, 1997). The ocean-continent subduction in the south continued
during almost the entire Permian (Nikishin, 2005).
The latest Gzhelian and earliest Asselian coincide with the climatic
optimum (warming), and a large transgression took place globally
(Davydov, 2014; Davydov et al., 2013; Griffis et al., 2021; Griffis et al.,
2019). The range and extent of the Early Permian glaciation(s) (P1 of
Eastern Australia) are somewhat controversial. In Eastern Australia, it is
considered to extend from the beginning of Asselian to the end of the
Sakmarian (Fielding et al., 2023), although the chronostratigraphic
constraints are provincial biota and imprecise SHRIMP U–Pb dates (the
best precision for the latter ±1–2 % i.e., 3–6 Myrs at this time). The new
high-precision CA-IDTIMS dates in SW Gondwana (Parana, Brazil and
Karoo, S. Africa basins) constrain two different glacial events within the
Asselian-Sakmarian: middle Asselian (298–297 Ma) and latest Asselian
s. l. (including early-middle Tastubian). A small glacial event was also
recognized in the early Artinskian of the Brazilian Parana Basin
(290–289 Ma) (Griffis et al., 2019), which is confirmed by the warmwater foraminiferan diversity drop in both the Boreal and Tethyan
provinces (Davydov, 2014; Davydov et al., 2003; Ueno et al., 2015).
Consequently, the climatic optima (global warming events) occurred in
the late Asselian (Shikhanian), late Sakmarian s. str. (Sterlitamakian),
and late Artinskian (Sarginian in the Preurals) (Davydov, 2014; Griffis
et al., 2021; Haig et al., 2014). Therefore, we might provisionally divide
the P1 glacial episode of Australia into two, constraining the P1A as
middle Asselian and P1B as the latest Asselian s. l. (= early-middle
Tastubian) (Fig. 4). The latest Gzhelian to earliest Asselian interval coincides with a pronounced climatic optimum (warming) and a major
global transgression (Davydov, 2014; Davydov et al., 2013; Griffis et al.,
2021; Griffis et al., 2019). The range and extent of Early Permian
glaciation (P1 of eastern Australia) remain debated. In eastern Australia,
glacial deposits are generally considered to span from the base of the
Asselian to the end of the Sakmarian (Fielding et al., 2023), although
these estimates rely on provincial biostratigraphy and imprecise
SHRIMP U–Pb ages (±1–2 %, or 3–6 Myr uncertainty). High-precision
CA–IDTIMS data from southwestern Gondwana (Paraná Basin, Brazil,
and Karoo Basin, South Africa) instead identify two discrete glacial
events within the Asselian–Sakmarian: a middle Asselian phase
(298–297 Ma) and a latest Asselian s.l. phase (including the early–middle Tastubian). A smaller glacial episode in the early Artinskian
(290–289 Ma) of the Paraná Basin (Griffis et al., 2019) is corroborated
by a synchronous decline in warm-water foraminiferal diversity in both
Boreal and Tethyan provinces (Davydov, 2014; Davydov et al., 2003;
Ueno et al., 2015). Accordingly, global climatic optima (warming intervals) occurred in the late Asselian (Shikhanian), late Sakmarian s.str.
(Sterlitamakian), and late Artinskian (Sarginian in the Pre-Urals)
(Davydov, 2014; Griffis et al., 2021; Haig et al., 2014). The P1 glacial
episode of Australia can thus be provisionally subdivided into P1A
(middle Asselian) and P1B (latest Asselian s.l., equivalent to the early–middle Tastubian) (Fig. 4).
These climatic and eustatic oscillations had profound paleogeographic implications. The chronostratigraphic framework of the
tetrapod footprints near Beijing is particularly critical for reconstructing
patterns of tetrapod dispersal and evolution in eastern Pangaea.
Throughout much of the Late Paleozoic, this region was isolated from
western Pangaea by the Uralian seaway, which linked the Paleo-Arctic
and Paleo-Tethyan oceans (Figs. 3–4). Marine sedimentation across
the East European Platform, Donets Basin, and Turan Platform, coupled
with the persistence of Tethyan fusulinid faunas until the Shikhanian–earliest Tastubian (late Asselian, ~295 Ma), indicate a persistent
marine barrier that restricted eastward tetrapod migration (Davydov,
2018). A major palaeogeographic reorganization during the early–middle Tastubian (latest Asselian)—involving the Turan Platform,
Karpinsky Swell, and Precaspian Basin—led to the emergence of the
relatively narrow Precaspian Isthmus, the first probable terrestrial
corridor between western and eastern Pangaea (Davydov, 2018)
(Fig. 3).
The hypothesis that amniotes (parareptiles or eureptiles) and temnospondyls entered eastern Pangaea in the late Gzhelian–early Asselian
(Chen and Liu, 2024) would require a remarkably rapid dispersal from
eastern Europe to northern China, spanning several thousand kilometers
across contrasting palaeogeographic and climatic provinces—including
uplands and extensive alluvial–lacustrine lowlands—without leaving
any intermediate fossil record. The earliest confirmed occurrences of the
seymouriamorph Ariekanerpeton sigalovi and possibly Lepospondyli date
6
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 4. Temporal distribution of the Late Paleozoic global warming and cooling events, suggested by the diversity of the warm-water benthic foraminiferins
(Davydov, 2014), sea-water surface temperature (oxygen δ18O ‰ VSWOM conodont data), and the records of the glaciations from Southern and Northern high
latitudes (Griffis et al., 2021; Davydov et al., 2022; Fielding et al., 2023). Global cooling events are associated with the decrease in the diversity of the foraminiferans,
intensive sea-level oscillations, and low atmospheric carbon dioxide values. The P2 glacial event in Australia is divided into two glacial episodes that are not yet
recognized as separate. The late Artinskian warming spike is according to the fusulinid data from Timor and Thailand (Haig et al., 2014; Ueno et al., 2015). Oxygen
δ18O (‰ VSWOM) data are from Chen et al. (2016). The question mark in the sea-surface temperature curve represents the potential break in sedimentation at the
Naqing section in South China, which is recognized from fusulinids (Anonymous, 1994). Black arrows on the right show the migration events documented in the
tetrapod record; red dots are theoretical migration events of tetrapods proposed by Brikiatis (2020). (For interpretation of the references to colour in this figure
legend, the reader is referred to the web version of this article.)
7
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 5. Paleogeographic map of Pangaea (Kocsis and Scotese, 2021). A, general view of Pangaea and distribution of tetrapods (table S1); B, Sakmarian-Artinskian
paleogeography of the southern part of East European Platform and surrounding regions (modified from Nikishin, 2005). The land masses in the south from the
Precaspian depression are solid, and no connection between the Tethyan and Urals-Arctic oceans existed. In the early Sakmarian, the discosauriscid tetrapods first
migrated to eastern Pangaea (Kurama, Tajikistan, southern Kazakhstan and North China [?]). Tetrapod localities, their numbers, and other attributes can be seen
in Table S1.
only to the earliest Sakmarian, ~6–7 Myr younger than the inferred age
of the footprint-bearing strata of the upper Taiyuan Formation. Another
seymouriamorph has been reported from the Sakmarian–Artinskian
Lucaogou Formation, Xinjiang (Liu et al., 2020).
We suggest that the northern Chinese tetrapod footprints are somewhat younger than currently assumed (Chen and Liu, 2024). Alternatively, an earlier dispersal into northern China cannot be entirely
excluded, though such a scenario contradicts the established Sakmarian–Artinskian age of the seymouriamorph-bearing deposits and appears
improbable. The causes of this apparent temporal and biogeographic
discrepancy remain unresolved and require further high-resolution
stratigraphic, geochronologic, and palaeontological investigation.
Chronostratigraphic constraints on the Kungurian glaciationdeglaciation cycles are not so well established, and in Australia a large
P2 glacial event was proposed in the late Artinskian through early
Kungurian (Fielding et al., 2023). The late Artinskian climatic optimum
has been recognized in several regions globally (Davydov, 2014; Haig
et al., 2017; Marchetti et al., 2022; Ueno et al., 2015). For this reason,
the P2 event of Australia was divided into the P2A early Artinskian
(Burtsevian) and P2B early Kungurian (Saranian) (Davydov et al.,
2016).
The Middle-Late Permian glaciation events were recognized in the
alpine setting of Eastern Australia only (Isbell et al., 2021), but were also
recently found in the Northern Hemisphere (Davydov et al., 2022). The
event P3 in Australia is precisely constrained by CA-IDTIMS (Metcalfe
et al., 2015) and it corresponds to the late Roadian-early Wordian
(Davydov et al., 2016; Henderson and Shen, 2020) and does not extend
into the Capitanian as recently proposed (Fielding et al., 2023; Isbell
et al., 2021). The P4 event is constrained as lower Wuchiapingian
(Metcalfe et al., 2015), but, for some reason, the P4 event in Australia is
shown to extend through the entire Wuchiapingian and Changhsingian
((Fielding et al., 2023), whereas in Southern Siberia, it corresponds to
the Wuchiapingian only (Davydov et al., 2022). In the latter region, an
additional and ephemeral cooling event is recognized in the latest
Changhsingian.
The regional paleoclimate in the East-European Platform (EEP),
Urals, and Precaspian during Pennsylvanian and Asselian time was
warm and moderately humid. The connection of the Uralian Seaway
with the Tethyan basins was well established with no evidence of the
isolation of the Urals-Precaspian and Donets Basin from the Tethyan
basins, as LBF in all these regions are the same (Davydov, 2018). The
Asselian sequences in the Donets Basin appeared as mixed marinecontinental sediments, but in the Pre-Donets trough in the northern
margin of the basin, the marine succession extended throughout the
entire Asselian (Alekseeva et al., 1983; Davydov, 1992). Within the late
and latest Asselian s.l. (i.e., between the Shikhanian and Tastubian
Regional stages of the East-European Platform) due to the P1B glacial
event, the Precaspian Isthmus appeared and existed throughout the
entire Late Paleozoic and Triassic (Davydov, 2018). The discosauriscid
tetrapods (Ariekanerpeton and Utegenia), for the first time in the Late
Paleozoic, migrated to eastern Pangaea (Fig. 5) (Ivakhnenko, 1981;
Kuznetsov and Ivakhnenko, 1981). At the Asselian-Sakmarian transition, the species taxonomic composition of the LBF between the Tethys
and Precaspian-Urals drastically changed and shared very few species
only at the beginning of the onset (Shikhanian-Tastubian transition) of
separation of these two basins (Davydov, 2018). The fusulinid species
composition between the Tethys and Precaspian-Urals during Sterlitamakian time (Sakmarian s.s.) was completely different (Davydov, 2018,
Fig. 6) The Sakmarian-Artinskian fusulinids and other fauna in the
Precaspian-Urals basins belong to the mid-latitudinal (cool-water)
biogeographic province (Davydov, 2018; Fedorowski et al., 2007). The
Precaspian Isthmus was solid and stable throughout the entire Late
8
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 6. Paleogeography and distribution of tetrapods in the Artinskian. The tetrapods are dominantly in western Pangaea, west of the Uralian mountains. The Uralian
seaway is becoming narrow, and the Northern Precaspian depression is relatively deep and large. Only the single occurrence of Utegenia (=Urumqia?), the close
relative of discosauriscids, in eastern Pangaea is known from the Junggur basin of Xinjiang, and nearby in Kurama and Kazakhstan are Sakmarian discosauriscids.
Tetrapod localities, their numbers, and other attributes can be seen in Table S2.
Fig. 7. Paleogeography and distribution of tetrapods in the early Kungurian. The Northern Precaspian depression is relatively shallow, undergoing sabkha evaporite
sedimentation. No definitely Kungurian tetrapods are found in eastern Panagea. Tetrapod localities, their numbers, and other attributes can be seen in Table S3.
9
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Paleozoic and Early Mesozoic. Shallow-water Changhsingian and Lower
Triassic marine sediments appear only in the Great Caucasus (Nikishin,
2005). During the Sakmarian and Artinskian the Uralian sea was still
wide and extended several thousand kilometers from the Precaspian
northwards, where it is connected to the Paleo-Arctic ocean.
The massive reefs along the eastern and southern edges of the EEP
first appeared in the Gzhelian-Asselian transition and as a second phase
in the late Asselian (Shikhanian) (Chuvashov, 1983; Gorozhanina et al.,
2018; Lukin and Galitsky, 1974). During the latest Asselian s.l. (Tastubian) the Uralian foredeep lacked reefs, but in the Sterlitamakian
(most of the Sakmarian s. str.) massive and common reefs extended
along the edge of the EEP once more (Chuvashov, 1983; Rauser-Chernousova et al., 1977). The appearance of the massive reefs in the Urals is
consistent with the global climatic optima (warming) and transgressions
recognized in the Gzhelian-Asselian transition, late Asselian and late
Sakmarian (Sterlitamakian) (Fig. 4) (Davydov, 2014; Davydov et al.,
2003).
The Evksinian orogeny is the eastern extension of the Variscan
orogenic belt and includes several Gondwanan terranes (Abetov and
Niyazova, 2020; Nikishin, 2005; Stampfli et al., 2013). Both Variscan
and Evksinian orogenic belts and the Turan Platform completely isolated
the Precaspian-Urals basins from the Paleo-Tethys through the Early
Triassic. A short Olenekian marine ingression brought shallow-water
marine sediments and fauna only in the south-western most part of
the Precaspian (Astrakhan-Volgograd areas) but did not extend farther
to the north and east (Kukhtinov and Crasquin-Soleau, 1999).
During the Artinskian, the Uralian seaway became an isolated and
narrow sea that extended from the Precaspian Isthmus northward to the
Timan-Pechora area (Fig. 6). The Uralian mountains were rising, and
siliciclastic input from the Uralian mountains increased, especially towards the end of the Artinskian. The climate in the early Artinskian was
cooler than in the Sterlitamakian, which is expressed in the biota as a
lower diversity of the LBF (Davydov, 2014) and the early Artinskian
flora (Naugolnykh and Linkevich, 2020; Naugol’nykh, 2007). Reefs
were lacking in the Early Artinskian of the Preurals (Chuvashov, 1983).
The Late Artinskian (Sargian) climate was much warmer than in the
early Artinskian with more diverse LBF and flora (Naugolnykh and
Linkevich, 2020). The reefs in the late Artinskian were common again,
but they were smaller in size (up to 200–350 m) and occur only in the
Central Urals and Timan-Pechora (Chuvashov, 1983). These reefs
extended into the earliest Kungurian (Saranian). Swamps and lakes
became common in the Artinskian of the Kuznetsk and Minusa basins, as
well as in Tunguska (Bogomazov, 1987; Cherepovskiy, 2003, 2000;
Davydov, 2021), suggesting a wet climate in those regions.
The paleogeography and climate changed in the early Kungurian.
Only a very narrow channel (up to 60–70 km wide) along the Uralian
mountains in the eastern foredeep existed at that time (Fig. 7), and some
parts of this channel potentially could be sometimes isolated from each
other (Naugolnykh, 2020). Aridisation of the climate was accompanied
by the development of thick gypsum and salt sediments in the Uralian
foredeep and western Kazakhstan and sabkha evaporites in the surrounding regions (Gusev et al., 1968; Ignatiev, 1976). The climate in the
Pechora, Kuznetsk, and Tunguska Basins persisted as wet and warm with
abundant lakes and swamps (Bogomazov, 1987; Cherepovskiy, 2003,
2002, 2000). In the late Kungurian, marine sedimentation occurred only
in the northernmost part of the Uralian foredeep and surrounding areas
(Northern Timan, Novaya Zemlya, and Barents Sea). Massive gypsum
and salt formation persisted only in the Precaspian basin, and in the rest
of the territory of the EEP and Urals clastic evaporites are accumulated
(Fig. 8). In the east of the Urals, the climate was still wet with abundant
lakes and swamps, except in the northern Tunguska Basin (Cherepovskiy, 2002; Gurevich, 1987). The absence of the seaway and lack of
high mountains again opened the opportunity for the terrestrial tetrapod
biota (Inostrancevia?) to migrate directly from the Moscow Basin eastward to Kazakhstan and Siberia (Fig. 8).
In the early Kungurian, the Precaspian-Preurals basins were filled
with thick evaporitic (salt) sediments. Only a very narrow marine
channel extended along the Uralian mountains (eastern margin of the
Urals foredeep) down to the Aktobe area of western Kazakhstan in the
early Kungurian (Fig. 7). In the late Kungurian (early Ufimian) the
Fig. 8. Paleogeography and distribution of tetrapods in the late Kungurian-early Roadian. The Northern Precaspian basin is filled with sabkha evaporates. The
Preuralian foredeep disappeared, and the Ural Mountains are nearly eroded, with the lowland corridor crossing the Urals towards Northern Kazakhstan and the
Kuznetsk Basin that brought tetrapods to western Pangaea. Tetrapod localities, their numbers, and other attributes can be seen in Table S3.
10
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 9. Paleogeography and distribution of tetrapods in the early Roadian (Kazanian). The early Kazanian transgression from the north extended from the PaleoArctic
to the North Caspian and the eastern part of the East-European Platform. This sea and the high mountains south of the Precaspian prevented any migration of
tetrapods to the east. Tetrapod localities, their numbers, and other attributes can be seen in Table S4.
evaporative basin was restricted to the Precaspian area only, whereas
most of the Urals were covered with lakes, swamps, and fluvial sediments (Fig. 8). The marine sedimentation at that time appears only in
the Polar Urals, Novaya Zemlya, and farther east and west at this latitude (35–40◦ N).
The early-middle Kazanian (Roadian) transgression brought the
Fig. 10. Paleogeography and distribution of tetrapods in the late Roadian-Wordian (late Kazanian-Urzhumian). The Northern Precaspian basin is filled with sabkha
evaporites. The Preuralian foredeep disappeared, and the Ural Mountains were nearly eroded with the lowland corridor crossing the Urals towards Northern
Kazakhstan and the Kuznetsk Basin that brought tetrapods from the East-European Platform to eastern Pangaea. Tetrapod localities, their numbers, and other attributes can be seen in Tables S4–5.
11
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
shallow marine environments from the north to the Precaspian-Preurals
basins once again. But the sea shifted westwards over the eastern part of
the East-European platform as a narrow sea extending to the central part
of the Precaspian Basin (Fig. 9). This sea, however, was open only to the
Paleo-Arctic in the north. The transgression associated with the global
warming event is documented in the latest Kungurian-early Roadian
(Fig. 4) (Davydov, 2014). In the EEP and the Preurals, this event manifested as a significant increase in the flora, insect, and fish diversity
(Esaulova, 1986; Rasnitsyn et al., 2015; Romano et al., 2016). The
ammonoids (Sverdrupites) went to the Kazanian Sea from the Boreal
Province (Barskov et al., 2014). The occurrence of locally developed
coal deposits in the eastern margin of the EEP (Kazan area)
(Cherepovskiy, 2000) suggests a somewhat wet climate. However, in the
second half of the early Kazanian, the climate became more arid, and, in
the late Kazanian, the regression drove sabkha-evaporite sedimentation
over most of the EEP (Fig. 10). At this transition, tetrapods again
migrated to the east, which is confirmed by the occurrence of the
dinocephalian genus Sinophoneus in the East-European Platform and
North China (Suchkova and Bakaev, 2024).The marine regime remained
only in the Pechora, Novaya Zemlya, and the southern Barents Sea
(Esaulova and Lozovsky, 1996; Nikonov et al., 2000) (Fig.10).
The Kazanian basin geographically occurs within the subtropics, but
belongs to the cool-water Boreal biogeographic province (Boltaeva,
2010; Muromtseva, 1984; Sukhov, 2003). No LBF or warm-water colonial corals occur in the early Kazanian sea, which does not have any
connections in the south with the warm-water Tethyan biota. The major
late Kazanian (late Roadian) regression in the region was caused by the
onset of the global climate cooling, which was recognized in both of
Earth’s Hemispheres and expressed as the P3 glaciation in Eastern
Australia and Southeast Siberian (Davydov et al., 2022; Fielding et al.,
2023). The marine sedimentation occurred only in the very north of the
Preuralian basin (Fig. 10). Thick redbeds formed along the Uralian
Mountains and sabkha evaporites along the eastern margin of the EastEuropean Platform (EEP). The Precaspian Basin was filled with salt and
sabkha evaporite sediments (Fig. 10). Because of the onset of the global
cooling event, it is associated with the global sea-level drop and
appearance of the low-land corridor between the East-European Platform, Siberia and China (Fig. 10).
During the early Roadian swamps and lakes were well developed
over the territory of the Tunguska and Kuznetsk Basins (Bogomazov,
1987; Cherepovskiy, 2003, 2002; Gurevich, 1987) as well as in TimanPechora (Nikonov et al., 2000), but the onset of the glacial phase (P3
event in the Eastern Australia and southern Siberia) during the late
Roadian and climate aridization strongly reduced the number of swamps
and lakes there (Figs. 9–10). Once the glacial phase extended into the
early Wordian, the climate during this time in the Timan-Pechora,
Tunguska, and Kuznetsk Basins areas was generally the same as in the
late Roadian (Cherepovskiy, 2002, 2000). Consequently, lakes and
swamps were poorly developed over the EEP, Preurals, and Siberia.
However, in the late Wordian (= late Urzhumian) the climate became
wetter, and the number and size of the lakes and swamps slightly
increased, especially over the EEP (Fig. 10) (Ignatiev, 1987; Strok, 1987;
Tverdokhlebov et al., 2005). The late Roadian was the time for the
second stage of tetrapod migration from the East European Platform to
the Kuznetsk Basin and to North China (Fig. 10).
The Urzhumian (Wordian) in the region possessed many traits of the
Kazanian paleogeography except the climate was quite wet with many
fluvial and lake deposits distributed over the Precaspian-Preurals and
the eastern part of the East-European Platform [EEP] Fig. 10). The distribution of heavy minerals (Arefiev, 2011) suggests that at the WordianCapitanian transition (Urzhumian-early Severodvinian) low mountains
appeared on the western margin of the Kazakhstania plate. The distribution of the tetrapods eastwards was lacking because of the predominantly cold climate and appearance of the mountains on the western
margin of the Kazakhstania Plate (Miletenko and Fedorenko, 2002) and
between Siberia and North China blocks due to the accretion and
Mongolian-Okhotsk belt development (Ganbat et al., 2022).
The Capitanian (= early Severodvinian) climate was generally the
same as the late Wordian with a fair number of lakes in the central part
and swamps in the northern part of the EEP (Timan-Pechora). In Siberia,
swamps were abundant, especially in the east (Norilsk and Taymyr regions), where Capitanian sediments are quite thick (Cherepovskiy,
2002). In the Kuznetsk Basin, the number of swamps increased
(Cherepovskiy, 2003). The Capitanian was a time when the sources of
siliciclastic input changed, and the source from the Baltic Shield progressively reduced, whereas the source from the Urals increased
(Arefiev, 2011). At the same time, the Uralian mountains in the late
Wordian and early Capitanian were eroded, and fluvial conglomerates
and coarser rocks are quite rare in the Capitanian and WuchiapingianChanghsingian sediments (Arefiev et al., 2015; Esaulova and Lozovsky, 1996; Ignatiev, 1976; Tverdokhlebov et al., 2006). In the earlylate Capitanian, lakes were still common all over the EEP and Preurals
(Strok, 1987; Tverdokhlebov et al., 2006).
Paleogeography changed slightly during the Capitanian (early Severodvinian) time. The onset of the global climate warming at that time
expressed in the East-European Platform, Kazakhstania, and Siberia as a
dry climate with fewer lakes and rivers (Tikhomirov, 1984; Tverdokhlebov et al., 2006). The mountains on the western margin of the
Kazakhstania plate continuously rose. Beginning in Capitanian time, the
heavy mineral source completely switched from the Baltic to Urals
provinces (Arefiev, 2011) (Fig. 11).
The Wuchiapingian Age was associated with the last global cooling
event, e.i., glacial event P4, and minor glacial deposits in Eastern
Australia and in south-east Siberia (Davydov et al., 2022; Fielding et al.,
2023) as well as massive coal accumulation in many middle-high latitude regions (Fig. 12). In contrast to the arid climate during the P3
glacial event (late Roadian-early Wordian), the climate in the EEP and
Siberia was quite wet with extensive forest and swamp development
(Fig. 12). Even in the Minusa Basin in S. Siberia, where coal formation
disappeared in the late Kungurian (Cherepovskiy, 2002), the Wuchiapingian coals appeared as well (Davydov, unpublished geochronologic
data). The landscape in the EEP and Preurals was hilly with numerous
large lakes distributed from south to north (Fig. 12) (Ignatiev, 1987;
Strok, 1987; Tverdokhlebov et al., 2006). Within the EEP, mature
swamps developed only in Timan-Pechora (Cherepovskiy, 2000)
(Fig. 12). The Wuchiapingian is the time of lake development in the
areas of the EEP and Preurals, and a time of biodiversity reduction of
tetrapods and flora in middle latitudes (Davydov and Karasev, 2021;
Day and Rubidge, 2021; Nowak et al., 2019). Lakes in the East-European
Platform were small but well-developed in the southern part of the EastEuropean Platform (Tverdokhlebov et al., 2006). The cyclic character of
occurrences of the heavy minerals from the eastern source suggests
periodical development of the mountains at the western margin of the
Kazakhstania plate and the appearance of a probable low land corridor
within the eroded mountains and the migration of tetrapods from the
East-European/Preurals area to North and South China (Liu et al., 2020)
(Fig. 12).
The Changhsingian climate and landscape in the regions under discussion generally remained the same as in the Wuchiapingian, with
numerous lakes developed over the EEP territory, and swamps in TimanPechora and over Siberia (Fig. 13). However, the climate progressively
became drier. The tectonic activity of the Urals towards the end of the
Changhsingian is accompanied by coarse material, including conglomerates and boulders, fossils and plant debris, and lake reduction
(Tverdokhlebov et al., 2007). Swamps in Timan-Pechora and Siberia
reduced in size and production (Cherepovskiy, 2003, 2002, 2001, 2000).
During the Permian-Triassic transition (~ 800 Kys before the Triassic)
the climate drastically became very dry (Davydov et al., 2021) This
climate extended into the Early Triassic.
During the Changhsingian, the paleogeography of the regions did not
change, but a significant climate warming in the second part of the
Changhsingian (Davydov et al., 2021) diversified the overall biota and
12
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 11. Paleogeography and distribution of tetrapods during Capitanian (early Severodvinian) time. Lakes in the East-European Platform became smaller, but
mountains at the western margin of the Kazakhstania plate still rose, as suggested by the heavy minerals provinciality and source of erosive material from the East
(Urals/Western Kazakhstania plate). Tetrapod localities, their numbers and other attributes can be seen in Table S6. (For interpretation of the references to colour in
this figure legend, the reader is referred to the web version of this article.)
Fig. 12. Paleogeography and distribution of tetrapods during Wuchiapingian time (late Severodvinian-early Vyatkian). Lakes in the East-European Platform were
small, but still well developed in the southern part of the East-European Platform. Pulses of heavy mineral occurrences from the eastern (Urals) source suggest
periodical development of the mountains at the western margin of the Kazakhstania plate. At the same time, the appearance of a probable lowland corridor within the
eroded mountains provided the opportunity for migration of tetrapods from the East-European-Preuralian area to North and South China. Tetrapod localities, their
numbers and other attributes can be seen in Table S7.
13
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Fig. 13. Paleogeography and distribution of tetrapods during Changhsingian (late Vyatkian) time. The collapse of the orogenic system along the Preurals and
Kazakhstanian plates at the Permian-Triassic transition, accompanied by significant climate warming in the second half of the Changhsingian, opened opportunities
for the occupation of the vast Siberian Platform and surrounding areas. Lakes in the East European Platform became smaller. Swamps in south Siberia and the TimanPechora regions existed until nearly the end of the Changhsingian. The onset of the Tunguska Trap’s volcanic activity near the end of the Changhsingian coincided
with large lakes and swamps appearing in the Tunguska and Taymyr Basins. The marine transgression in the Turgai basin (part of the Turan Platform), the southern
part of the Precaspian, and along the North Caucasus occurred during the late Lopingian and Triassic. Tetrapod localities, their numbers, and other attributes can be
seen in Table S8.
opened opportunities for the occupation of the new and giant territory of
the Siberian Platform and surrounding areas (Fig. 13). The swamps still
existed until nearly the end of the Changhsingian in the huge territory
from the Kuznetsk Basin (Davydov et al., 2021) to Tunguska, Taymyr
and Timan. The onset of the Tunguska Trap’s volcanic activity near the
end of the Changhsingian coincided with the lake’s appearance in the
Tunguska Basin of Siberia (Fig. 13). Short-term marine ingression in the
Turgai basin (part of the Turan Platform) and in Central Kizilkum
potentially could have occurred during the Guadalupain-Lopingian
(Fig. 13) (Chuvashov et al., 1984; Smirnov, 2020; Volozh et al., 2016).
Craton sometime within the Bashkirian (Miletenko and Fedorenko,
2002), it did not affect the tetrapod’s distribution as the Ural Seaway
still existed and completely blocked the dispersal of tetrapods to the
Eastern Pangaea continent until late Asselian s. l. (Shikhanian) time
(Davydov, 2018). The Carboniferous-earliest Permian (Asselian)
tetrapod-free gap seems to have been caused by the existence of the
Uralian seaway and the complete isolation of Eastern Pangaea from the
rest of the supercontinent (Fig. 3).
The oldest tetrapods in Eastern Pangaea are known from Kazakhstan
and Tadzhikistan in the Sakmarian s. str. (Figs. 3–4). In the early
Roadian they appear in the Kuznetsk Basin, Central Kazakhstan, and
become more common in North China (see Chapter 2 above). The
quantitative biostratigraphic and radioisotopic calibration of the Pennsylvanian–early Permian global time scale, detailed paleogeography and
paleoclimate, and quantitative model of distribution of LBF, which is an
excellent and sensitive indicator of paleogeography, signify the
appearance of a permanent continental bridge – the Precaspian Isthmus
since latest Asselian s. l. (Tastubian) time This became a dispersal route
for tetrapods to reach eastern Pangaea, a promised land with minimum
or no competition in the nearly open lands (Davydov, 2018).
The proposed recent junction-disjunction model suggests that
tetrapod migration from Western to Eastern Pangaea is controlled by
eustatic sea-level fluctuation and started as early as the beginning of the
Pennsylvanian (Brikiatis, 2020). As advocated by this model, several
ephemeral and hypothetical connections between Western and Eastern
Pangaea took place via the Precaspian Isthmus and could have occurred
at the eustatic global lowstand around 321 Ma (early Bashkirian) and in
the latter time all over until the Kungurian. These “ephemeral” connections could result in the potential terrestrial biota migration to
6. Discussion
The distribution of tetrapods across Pangaea during the late Paleozoic is quite intriguing, but still unclear. They possess relatively
continuous sequences and evolution from the Devonian to Triassic in
Western Pangaea, but are not known for certain in the Carboniferous in
the Eastern part of the supercontinent. Their occurrence over the region
in the early Permian is uncertain Their distribution is controlled by the
Pangaea formation phases. However, this process is quite controversial
(see introduction) and may not provide a clear history of tetrapod distribution. The question remains as to why the tetrapods do not appear in
eastern Pangaea until the earliest Permian (Li and Reisz, 2019; Lucas,
2005). The mode of movement and locomotion of tetrapods is feasible
only on a hard surface. Western Pangaea completely consolidated
(Gondwana-Laurussia collision) around mid-Carboniferous time
(Davydov and Cózar, 2019) and was the scene of late Paleozoic tetrapod
evolution, whereas in Eastern Pangaea, the tetrapods appeared only in
the post-Asselian. While the Kazakhstania plate joined the Siberian
14
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Appendix A. Supplementary data
Eastern Pangaea during the Cheremshanian (318 Ma), Podolskian (309
Ma), Krevyakian (306.7 Ma), Khamovnikian (305.2 Ma), Sterlitamakian
(293.2) (early Sakmarian s. s. [293.2], and Burtsevian (287.3) (Fig. 4).
However, this is an oversimplified model that does not consider the
entire sets of real data and facts.
First, the warm-water benthic foraminiferans demonstrated the existence of the permanent oceanic seaway between Uralian, Boreal, and
Tethyan assemblages. No endemism that could potentially have resulted
from the presence of a Precaspian Isthmus is observed and/or documented in Pennsylvanian-late Asselian s. l. time. In contrast, since the
latest Asselian s. l. (Tastubian) the taxonomy of the warm-water benthic
foraminiferan fauna at the species level in the Precaspian-Urals became
completely different from that in the Tethyan basins (Davydov, 2018)
because of the appearance of the Precaspian Isthmus and the complete
isolation of the Ural-PaleoArctic from the Paleo Tethys.
The attractive junction-disjunction model suggests the strong
concordance of tetrapod evolution with sea-level fluctuations and that
… “the temporal development of the vicariant topology seems to fit
closely with the emergence rhythm of the recovered synapsid taxa,
suggesting vicariance due to Pangaean separation as the cause of early
supported by the existing data on the tetrapod occurrence and distribution.” (Brikiatis, 2020, p.1). But, the tetrapods could not migrate
eastwards from western Pangaea until the appearance of a permanent
Precaspian Isthmus at the Asselian-Sakmarian transition (Fig. 4), as
documented by the CA-IDTIMS radioisotopic data from Tadzhikistan.
The weakest part of the junction-disjunction model is the lack of
regional/local data on tectonics, paleogeography, landscaping, and
paleoclimate. It has also not been described or discussed how the cladograms of the Late Paleozoic synapsids have been numerically
calibrated.
The chronostratigraphy of the continental successions is always
vague, and their constraints are quite broad and at best established with
flora, insects, and non-marine fauna. Very few late Paleozoic tetrapod
localities are precisely constrained by radioisotopic dates. Similarly, the
global sea-level model (Haq and Schutter, 2008) is very generalized and
quite variable from region to region. The Late Paleozoic sequence
stratigraphic model has been recently precisely constrained with
radioisotopic calibration in the Urals, Texas and South China (Davydov
et al., 2018; Schmitz and Davydov, 2012; Shen et al., 2020; Wu et al.,
2020) and the model of the migration of tetrapods proposed in this paper
(black arrows in Fig. 4) developed from the occurrences of the tetrapods
in eastern Pangaea and it contradicts the junction-disjunction model
(Brikiatis, 2020). We must admit that the global sea-level fluctuation
might play a critical role in the distribution of tetrapods; however, other
factors, such as regional tectonics (mountains), paleogeographic features (seaway and bridge), landscaping (lakes, swamps, relief etc.),
provenance and especially climate are important factors that critically
controlled the distribution of terrestrial communities.
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.earscirev.2025.105344.
Data availability
Data will be made available on request.
References
Abetov, A.E., Niyazova, A.T., 2020. The hystory of the geologic development of northern
Ustyurt region during Paleozoic time. Curr. Scientific Res. Modern World 59, 41–50
(In Russian).
Ahlberg, P.E., Milner, A.R., 1994. The origin and early diversification of tetrapods.
Nature 368, 507–514. https://doi.org/10.1038/368507a0.
Alekseeva, I.A., Glushenko, N.V., Ivanov, V.K., Inosova, K.I., Kalmykova, M.A., Kashik, D.
S., Kozirskaya, R.I., Kruzina, A.K., Movshovich, E.V., Redichkin, N.A.,
Schwartsman, E.G., 1983. Key-Section of the Canroniferous-Permian Boundary Beds
in the South of the East-European Platform(Gzhelian and Asselian Stages,
Skosyrskaya Borehole N 4199). Nedra Publishing House (In Russian), Leningrad.
Arefiev, M.P., 2011. The influence of the Baltic and Urals terrigenous supply provinces
on sedimentation at the Permian-Triassic boundaries in the northeastern part of
Moscow Syneclise. In: Yapaskurt, O.V., Khasanov, R.R., Sungatullin, R.K. (Eds.),
Conceptual Problems of Lithological Research in Russia. Kazan Federal University,
Kazan, pp. 63–67 (In Russian).
Arefiev, M.P., Golubev, V.K., Kuleshov, V.N., Pokrovsky, B.G., 2015. Paleogeographical
reorganization of the Moscow Syneclise during the Severodvinian
(Capitanian–Wuchiapingian) time based on isotopic (δ13C and δ18O) and
paleontological data, Permian Period, east European Platform. Paleontol. J. 49,
1206–1227. https://doi.org/10.1134/S0031030115110027.
Barskov, I.S., Leonova, T.B., Shilovsky, O.P., 2014. Middle Permian cephalopods of the
Volga-Ural Region. Paleontol. J. 48, 1331–1414. https://doi.org/10.1134/
S0031030114130012.
Benton, M.J., 2015. Vertebrate palaeontology, xi. Wiley Blackwell, Chichester West
Sussex, Hoboken NJ, 468 pages.
Bernardi, M., Petti, F.M., Benton, M.J., 2018. Tetrapod distribution and temperature rise
during the Permian-Triassic mass extinction. Proc. R. Soc. B 285, 1–8. https://doi.
org/10.1098/rspb.2017.2331.
Blakey, R., 2011. Global Paleogeography. NAU Geology.
Bogomazov, Y.M., 1987. Late Paleozoic lakes of Ural-Mongolian tectonic belt. In:
Martinson, G.G., Neustrueva, I.I. (Eds.), The History of the Late Paleozoic and
Mesozoic Lakes. Nauka Publishing House, Leningrad, pp. 96–113 (In Russian).
Bogush, O.I., Bochkarev, V.S., Yuferev, O.V., 1974. The Paleozoic of the South of the
West Siberia. Nauka Publishing House (In Russian), Novosibirsk.
Bogush, O.I., Starostin, V.A., Yuferev, O.V., 1976. Biostratigraphy of BaskirianMoscovian deposits of north-eastern Prebalkhashie. In: Dubatolov, V.N. (Ed.),
Prebalkhashie - the Transitional Zone of the Biogeographic Belts of Late
Carboniferous (Pennsylvanian). Nauka Publishing House, Novosibirsk, pp. 6–25 (In
Russian).
Boltaeva, V.P., 2010. Brachiopods of Kazanian Stage of Volgo-Kama Region and their
Stratigraphic Significance. Kazan State Unviresity (In Russian), Kazan.
Brikiatis, L., 2020. An early Pangaean vicariance model for synapsid evolution. Sci. Rep.
10, 13091. https://doi.org/10.1038/s41598-020-70117-8.
Brocklehurst, N., Dunne, E.M., Cashmore, D.D., Frӧbisch, J., 2018. Physical and
environmental drivers of Paleozoic tetrapod dispersal across Pangaea. Nat. Commun.
9, 5216. https://doi.org/10.1038/s41467-018-07623-x.
Brown, D., Alvarez-Marrón, J., Pérez-Estaún, A., Gorozhanina, Y., Baryshev, V.,
Puchkov, V., 1997. Geometric and kinematic evolution of the foreland thrust and
fold belt in the southern Urals. Tectonics 16, 551–562. https://doi.org/10.1029/
97TC00815.
Budnikov, I.V. (Ed.), 1996. Kuzbass - a Key Region for the Upper Paleozoic Stratigraphy
in Angarida. Intergeo, 122 p. (In Russian), Novosibirsk).
Bykadorov, V.A., Bush, V.A., Fedorenko, O.A., Filippova, I.V., Miletenko, N.V.,
Puchkov, V.N., Smirnov, A.V., Uzhkenov, B.S., Volozh, Y.A., 2003. Ordovician —
Permian palaeogeography of Central Eurasia: development of Paleozoic petroleumbearing basins. J. Pet. Geol. 26, 325–350 (In Russian).
Cavazza, W., Roure, F., Spakman, W., Stampfli, G.M., Ziegler, P.A., 2004. The
TRANSMED Atlas the Mediterranean Region from Crust to Mantle. SPRINGER, Berlin
Heidelberg.
Chen, J., Liu, J., 2024. Journey to the east: the oldest tetrapod fauna of east Pangea in
early Permian. Natl. Sci. Rev. 11, nwae249. https://doi.org/10.1093/nsr/nwae249.
Cherepovskiy, V.F. (Ed.), 2000. Coal Reservoirs of Russia. Volume 1. Coal Basins of
European part of the Russia. Geoinformmark (In Russian), Moscow, 498 p.
Cherepovskiy, V.F. (Ed.), 2001. Coal Reservoirs of Russia. Volume 4. Coal Basins of East
Siberia. Geoinformmark (In Russian), Moscow, 500 p.
Cherepovskiy, V.F. (Ed.), 2002. Coal Reservoirs of Russia. Volume 3. Coal Basins of East
Siberia, southern part. Geoinformmark (in Russian), Moscow, 507 p.
Coal Reservoirs of Russia. In: Cherepovskiy, V.F. (Ed.), 2003. Coal Basins of West Siberia.
Geoinformmark (In Russian), Moscow, vol. 2, 604 p.
Chernykh, V.V., Chuvashov, B.I., Shen, S., Henderson, C.M., Yuan, D.-X., Stephenson, M.
H., 2020. The Global Stratotype Section and Point (GSSP) for the base- Sakmarian
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgments
We are thankful to all individuals in Adrasman, Tadzhikistan who
helped us with logistics and other support in the field work. This material is based upon work supported by the National Science Foundation
under Grant No. EAR-1337887, EAR-1735889, and EAR-1920336 to MS.
Valery K. Golubev provided the original description of the locality in the
Sarytaipan hills. The first author thanks his wife Dina for her patience
with his crazy projects. The careful review of Dr. Jianye Chen IVPP,
Chinese Academy of Sciences and an anonymous reviewer improved the
manuscript in many respects.
15
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Stage (Cisuralian, lower Permian). Int. Union Geol. Sci. 43, 961–979. https://doi.
org/10.18814/epiiugs/2020/020059.
Chumakov, N.M., Zharkov, M.A., 2002. Climates during Permian-Triassic Changes in the
Biosphere; Paper 1. Early Permian climate. Stratigraphy, Geological Correlation 10
(6), 62–81.
Chuvashov, B.I., 1983. Permian Reefs of the Urals. Facies 8, 191–212.
Chuvashov, B.I., Ivanova, R.M., Kolchina, A.N., 1984. Upper Paleozoic of the east slope
of the Urals. In: Stratigraphy and Geologic History: 1984. Uralian Scientific Center of
the Academy of Science of USSR, Sverdlovsk, p. 230 (In Russian).
Cocks, L.R.M., Torsvik, T.H., 2007. Siberia, the wandering northern terrane, and its
changing geography through the Palaeozoic. Earth Sci. Rev. 82, 29–74. https://doi.
org/10.1016/j.earscirev.2007.02.001.
Davydov, V.I., 1992. Subdivision and correlation of Upper Carboniferous and lower
Permian deposits in Donets Basin according to fusulinid data. Soviet Geol. 53–61 (In
Russian.).
Davydov, V.I., 2009. Bashkirian-Moscovian Transition in Donets Basin: The Key for
Tethyan-Boreal Correlation. In: Puchkov, V.N. editor "Carboniferous Type Sections
in Russia and Potential Global Stratotypes". Proceedings of the International Field
Meeting “The historical type sections, proposed and potential GSSP of the
Carboniferous in Russia”. Southern Urals Session. Ufa – Sibai, 13–18 August, 2009.
Ufa: DesignPolygraphService Ltd., 2009, Ufa, 188-192.
Davydov, V.I., 2014. Warm water benthic foraminifera document the
Pennsylvanian–Permian warming and cooling events — The record from the
Western Pangea tropical shelves. Palaeogeogr. Palaeocimatol. Palaeogeogr. 414,
284–295.
Davydov, V.I., 2018. Precaspian Isthmus emergence triggered the early Sakmarian
glaciation: evidence from the lower Permian of the Urals, Russia. Palaeogeogr.
Palaeocimatol. Palaeogeogr. 511, 403–418. https://doi.org/10.1016/j.
palaeo.2018.09.007.
Davydov, V.I., 2021. Tunguska coals, Siberian sills and the Permian-Triassic extinction.
Earth Sci. Rev. 212, 103438. https://doi.org/10.1016/j.earscirev.2020.103438.
Davydov, V.I., 2024. The crises in the global Permian correlation - Canadian Arctic-Urals
case: Permophiles issue #76 January 2024. Permophiles 35–41.
Davydov, V.I., Cózar, P., 2019. The formation of the Alleghenian Isthmus triggered the
Bashkirian glaciation: Constraints from warm-water benthic foraminifera.
Palaeogeogr. Palaeocimatol. Palaeogeogr. 531, 108403. https://doi.org/10.1016/j.
palaeo.2017.08.012.
Davydov, V.I., Karasev, E.V., 2021. The Influence of the Permian-Triassic Magmatism in
the Tunguska Basin, Siberia on the Regional Floristic Biota of the Permian-Triassic
transition in the Region. Front. Earth Sci. 9 (635179), 1–12. https://doi.org/
10.3389/feart.2021.635179.
Davydov, V.I., Popov, A.V., 1986. Upper Carboniferous and lower Permian sections of
the southern Urals. In: Chuvashov, B.I., Leven, E.Y.A., Davydov, V.I. (Eds.),
Carboniferous/Permian Boundary Beds of the Urals, Pre-Urals Area and Central Asia.
Nauka Publishing House, Moscow, pp. 29–33 (In Russian).
Davydov, V.I., Schiappa, T.A., Snyder, W.S., 2003. Testing the sequence stratigraphy
model: response of fusulinacean fauna to sea-level fluctuations (examples from
pennsylvanian and Cisuralian of the Precaspian–southern Urals region). In: Olson, H.
C., Leckie, M.R. (Eds.), Micropaleontologic Proxies for Sea-level Change and
Stratigraphic Discontinuities, pp. 361–378.
Davydov, V.I., Haig, D.W., Mccartain, E., 2013. A latest Carboniferous warming spike
recorded by a fusulinid-rich bioherm in Timor Leste: Implications for East Gondwana
deglaciation. Palaeogeogr. Palaeocimatol. Palaeogeogr. 376, 22–38. https://doi.org/
10.1016/j.palaeo.2013.01.022.
Davydov, V.I., Biakov, A.S., Isbell, J.L., Crowley, J.L., Schmitz, M.D., Vedernikov, I.L.,
2016. Middle Permian U–Pb zircon ages of the “glacial” deposits of the Atkan
Formation, Ayan-Yuryakh anticlinorium, Magadan province, NE Russia: Their
significance for global climatic interpretations. Gondwana Res. 38, 74–85. https://
doi.org/10.1016/j.gr.2015.10.014.
Davydov, V.I., Biakov, A.S., Schmitz, M.D., Silantiev, V.V., 2018. Radioisotopic
calibration of the Guadalupian (middle Permian) series: Review and updates. Earth
Sci. Rev. 176, 222–240. https://doi.org/10.1016/j.earscirev.2017.10.011.
Davydov, V.I., Karasev, E.V., Nurgalieva, N.G., Schmitz, M.D., Budnikov, I.V., Biakov, A.
S., Kuzina, D.M., Silantiev, V.V., Urazaeva, M.N., Zharinova, V.V., Zorina, S.O.,
Gareev, B., Vasilenko, D.V., 2021. Climate and biotic evolution during the PermianTriassic transition in the temperate Northern Hemisphere, Kuznetsk Basin, Siberia,
Russia. Palaeogeogr. Palaeocimatol. Palaeogeogr. 110432, 1–26. https://doi.org/
10.1016/j.palaeo.2021.110432.
Davydov, V.I., Budnikov, I.V., Kutygin, R.V., Nurgalieva, N.G., Biakov, A.S., Karasev, E.
V., Kilyasov, A.N., Makoshin, V.I., 2022. Possible bipolar global expression of the P3
and P4 glacial events of eastern Australia in the Northern Hemisphere: Marine
diamictites and glendonites from the middle to upper Permian in southern
Verkhoyanie, Siberia. Geology 50, 874–879. https://doi.org/10.1130/G50165.1.
Day, M.O., Rubidge, B.S., 2021. The late Capitanian Mass Extinction of Terrestrial
Vertebrates in the Karoo Basin of South Africa. Front. Earth Sci. 9, 631198. https://
doi.org/10.3389/feart.2021.631198.
Domeier, M., Torsvik, T.H., 2014. Plate tectonics in the late Paleozoic. Geosci. Front. 5,
303–350. https://doi.org/10.1016/j.gsf.2014.01.002.
Duhamel, A., Benoit, J., Rubidge, B.S., Liu, J., 2021. A re-assessment of the oldest
therapsid Raranimus confirms its status as a basal member of the clade and fills
Olson’s gap. Naturwissenschaften 108, 1–12. https://doi.org/10.1007/s00114-02101736-y.
Efremov, I.A., 1939. First representative of Siberian early tetrapods. Comptes Rendus
(Doklady) de I’ Academie des Sciences de l’URSS 23, 106–109.
Efremov, I.A., 1951. Discovery of the lower Permian tetrapods in the Northerm
Kazakhstan. Doklady Acad. Sci. USSR 77, 721–724 (In Russian).
Efremov, I.A., V’yushkov, B.P., 1955. Catalogue of localities of Permian and Triassic
terrestrial vertebrates in the territories of the U.S.S.R.: Transactions of the
Paleontological Institute, vol. 44 Moscow (In Russian), pp. 1–185.
Esaulova, N.K., 1986. Flora of Kazanian Stage of the Prikamia (Volgo-Urals). Kazan State
Unviresity, Kazan.
Esaulova, N.K., Lozovsky, V.P. (Eds.), 1996. Stratotypes and Key-Sections of the Upper
Permian of Povolzhie and Prekamie Regions. Ecocenter, Kazan, p. 176 (In Russian).
Fedorowski, J., Bamber, E.W., Stevens, C.H., 2007. In: Lower Permian Colonial Rugose
Corals, Western and Northwestern Pangaea: Taxonomy and Distribution. NRC
Research Press, Ottawa, Ontario, Canada, 231 pp. NRC Research Press, Ottawa.
Fielding, C.R., Frank, T.D., Birgenheier, L.P., 2023. A revised, late Palaeozoic glacial
time-space framework for eastern Australia, and comparisons with other regions and
events. Earth Sci. Rev. 236, 104263. https://doi.org/10.1016/j.
earscirev.2022.104263.
Ganbat, A., Tsujimori, T., Miao, L., Safonova, I., Pastor-Galán, D., Anaad, C., Aoki, S.,
Aoki, K., Chimedsuren, M., 2022. Age, petrogenesis, and tectonic implications of the
late Permian magmatic rocks in the Middle Gobi volcanoplutonic Belt. Mongolia.
Island Arc 31, e12457. https://doi.org/10.1111/iar.12457.
Gao, L.F., Ding, H., Wan, X.Q., 2005. Taxonomic revision of conodont (Sweetognathus)
species in the uppermost Taiyuan formation, Yuhuai Basin and its significance. Acta
Micropaleontologica Sinica 22, 370–382 (In Chinese).
Golonka, J., 2007. Phanerozoic paleoenvironment and paleolithofacies maps: Mesozoic.
Geologia (Krakow) 33, 211–264 (In Polish.
Golonka, J., 2011. Phanerozoic palaeoenvironment and palaeolithofacies maps of the
Arctic region. In: Spencer, A.M., Embry, A.F., Gauthier, D. ДюЖ, Stoupakova, A.V.,
Sorensen, K. (Eds.), Arctic Petroleum Geology. Geological Society of London,
London, pp. 79–129.
Gorozhanina, E.N., Gorozhanin, V.M., Isakova, T.N., 2018. The Carbonate Massif of
Voskresenka Mount in the Southern Pre-Urals: Age and Development of the
Submerged Carbonate Platform. Stratigr. Geol. Correl. 26, 139–156.
Griffis, N.P., Montañez, I.P., Mundil, R., Richey, J., Isbell, J., Fedorchuk, N., Linol, B.,
Iannuzzi, R., Vesely, F., Mottin, T., da Rosa, E., Keller, B., Yin, Q.-Z., 2019. Coupled
stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-togreenhouse turnover in south-Central Gondwana. Geology 47, 1146–1150. https://
doi.org/10.1130/G46740.1.
Griffis, N., Montañez, I., Mundil, R., Le Heron, D., Dietrich, P., Kettler, C., Linol, B.,
Mottin, T., Vesely, F., Iannuzzi, R., Huyskens, M., Yin, Q.-Z., 2021. High-latitude ice
and climate control on sediment supply across SW Gondwana during the late
Carboniferous and early Permian. Bull. Geol. Soc. Am. 133, 2113–2124. https://doi.
org/10.1130/B35852.1.
Griffis, N., Mundil, R., Montañez, I., Le Heron, D., Dietrich, P., Iannuzzi, R., 2023.
A Carboniferous apex for the late Paleozoic icehouse. SP 535, 117–129. https://doi.
org/10.1144/SP535-2022-256.
Guo, X., Retallack, G.J., Liu, J., 2023. Paleoenvironments of late Devonian tetrapods in
China. Sci. Rep. 13, 20378. https://doi.org/10.1038/s41598-023-47728-y.
Gurevich, A.Y., 1987. Late Paleozoic lakes in Tunguska coal-basin territory. In:
Martinson, G.G., Neustrueva, I.I. (ds.), eThe History of the Late Paleozoic and
Mesozoic Lakes. Nauka Publishing House, Leningrad, pp. 114–127 (In Russian).
Gusev, A.K., Bogatyrev, V.V., Igonin, V.M., Solodukho, M.G., 1968. Stratigraphy of the
Upper Paleozoic Deposits of Aktobe Preurals. Kazan State Unviresity, Kazan (In
Russian), p. 220.
Haig, D.W., McCartain, E., Mory, A.J., Borges, G., Davydov, V.I., Dixon, M., Ernst, A.,
Groflin, S., Håkansson, E., Keep, M., Santos, Z.D., Shi, G.R., Soares, J., 2014.
Postglacial early Permian (late Sakmarian–early Artinskian) shallow-marine
carbonate deposition along a 2000km transect from Timor to West Australia.
Palaeogeogr. Palaeocimatol. Palaeogeogr. 409, 180–204. https://doi.org/10.1016/j.
palaeo.2014.05.009.
Haig, D.W., Mory, A.J., McCartain, E., Backhouse, J., Håkansson, E., Ernst, A., Nicoll, R.
S., Shi, G.R., Bevan, J.C., Davydov, V.I., Hunter, A.W., Keep, M., Martin, S.K.,
Peyrot, D., Kossavaya, O., Santos, Z.D., 2017. Late Artinskian–Early Kungurian
(Early Permian) warming and maximum marine flooding in the East Gondwana
interior rift, Timor and Western Australia, and comparisons across East Gondwana.
Palaeogeogr. Palaeocimatol. Palaeogeogr. 468, 88–121. https://doi.org/10.1016/j.
palaeo.2016.11.051.
Henderson, C.H., Shen, S.Z., 2020. The Permian Period. In: Gradstein, F.M., Ogg, J.G.,
Schmitz, M.D., Ogg, G.M. (Eds.), Geologic Time Scale 2020, vol. 2. Elsevier,
Amsterdam, Netherlands, pp. 875–902.
Ignatiev, V.I., 1976. The Formation of the Volga-Urals Anteclyse during Permian Period.
Kazan State Unviresity (In Russian), Kazan, p. 256.
Ignatiev, Y.Y., 1987. Late Permian lakes of Volgo-Urals anteclise. In: Martinson, G.G.,
Neustrueva, I.I. (Eds.), The History of the Late Paleozoic and Mesozoic Lakes,
140–148 (in Russian). Nauka Publishing House, Leningrad.
Isbell, J.L., Vesely, F.F., Rosa, E.L.M., Pauls, K.N., Fedorchuk, N.D., Ives, L.R.W.,
McNall, N.B., Litwin, S.A., Borucki, M.K., Malone, J.E., Kusick, A.R., 2021.
Evaluation of physical and chemical proxies used to interpret past glaciations with a
focus on the late Paleozoic Ice Age. Earth Sci. Rev. 221, 103756. https://doi.org/
10.1016/j.earscirev.2021.103756.
Ivakhnenko, M.F., 1981. Discosauriscians from the Permian of Tadzhikistan. Paleontol.
Zh. 114–128 (In Russian).
Kaz’min, M.G., Natapov, L.M. (Eds.), 1998. The Paleogeographic Atlas of Northern
Eurasia. Institute of Tectonics of Lithospheric Plates, Moscow.
Klembara, J., Ruta, M., 2004. The seymouriamorph tetrapod Utegenia shpinari from
the ?Upper Carboniferous-lower Permian of Kazakhstan. Part II: Postcranial anatomy
and relationships. Transact. R. Soc. Edinburgh 94, 75–93.
Kohn, J., Barrick, J.E., Wahlman, G.P., Baumgardner, R., 2019. Late Pennsylvanian
(Virgilian) to Early Permian (Leonardian) Conodont Biostratigraphy of the
16
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
"Wolfcamp Shale", Northern Midland Basin, Texas. In: Denne, R.A., Kahn, A.C.M.
(Eds.), Geologic problem solving with microfossils IV. SEPM (Society for
Sedimentary Geology), Broken Arrow, Oklahoma, pp. 245–261.
Kolchin, A.N., 2004. Geologic position of lower Permian flora of Sarytaipan hill, Kuramin
tectionic zone, Central Karamazar. In: Transactions of the Institute of Geology of
Tadzhikistan, New Series, pp. 63–73. Issue 3, (In Russian).
Kong, X.Y., Xu, H.L., Li, R.L., Chang, J.L., Liu, L.J., Zhao, X.G., Zhang, L.X., Liao, Z.T.,
Zhu, H.C., 1996. Late Paleozoic Coal-Bearing Strata and Biota in Shanxi. Shanxi
Science and Technology Press (In Chinese), Taiyuan, China.
Krainer, K., Davydov, V.I., 1998. Faciès and biostratigraphy of the late Carboniferous/
early Permian sedimentary séquence in the Carnic Alps (Austria/ltaly). Geodiversitas
20, 643–662.
Kukhtinov, D.A., Crasquin-Soleau, S., 1999. Upper Permian and Triassic of the
Precaspian Depression: stratigraphy and palaeogeography: 325346. Geodiversitas
21, 325–346.
Kutumov, Y.D., Karpov, G.P., Goncharov, Y.I., 1976. Geological map of USSR. Tunguska
Series, Sheet P-47_XXXV (1:200000 scale). Explanatory notes. Moscow (In Russian),
1–83 p.
Kuznetsov, V.V., Ivakhnenko, M.F., 1981. Discosauriscids from the Upper Paleozoic of
Southern Kazakhstan. Paleontol. Zh. 3, 102–110 (In Russian).
Lawver, L.A., Gahagan, L.M., Norton, I., 2011. Palaeogeographic and tectonic evolution
of the Arctic region during the Palaeozoic. Mem. Geol. Soc. Lond. 35, 61–77.
Leven, E.J., Davydov, V.I., 2001. Stratigraphy and fusulinids of the Kasimovian and
lower Gzhelian (upper Carboniferous) in the Southwestern Darvaz. Revista Italiana
di Paleontologia e Stratigrafia 107, 3–46.
Leven, E.Y., Ozkan, R., 2004. New Permian fusulinids from Turkey and some problems of
their biogeography. Stratigr. Geol. Correl. 12, 336–346.
Levitan, M.M., 1985. Geological map of the USSR, scale 1:200.000, series Tunguska, Q47-XXXV-XXXVI. Explanatory Notes (Moscow (In Russian).
Li, X., Reisz, R.R., 2019. A Paleobiogeographic Problem of the late PaleozoicTetrapods in
East Eurasia. Geologica Sinica 93, 263–264.
Li, J., Zhou, Z., He, Y., Wang, G., Wu, C., Liu, C., Yao, G., Xu, W., Zhao, X., Dai, P., 2018.
Geochronological and sedimentological evidences of Panyangshan foreland basin for
tectonic control on the late Paleozoic plate marginal orogenic belt along the northern
margin of the North China Craton. Int. J. Earth Sci. (Geol Rundsch) 107, 1193–1213.
https://doi.org/10.1007/s00531-017-1528-z.
Li, X., Li, Z., Wang, D., Chang, X., Li, Y., Zheng, X., Feng, K., Zhao, H., 2025. Impact of
astronomical forcing on sea-level changes and peat-swamp development in the late
Paleozoic of North China. Palaeogeogr. Palaeocimatol. Palaeogeogr. 678, 113232.
https://doi.org/10.1016/j.palaeo.2025.113232.
Litvinovich, N.V., Golubovskaya, T.N., Golubovsky, V.A., Chumakova, N.F., 1977. The
main results of study of the Carboniferous and Permian deposits of Central
Kazakhstan. In: Zatsev, Yu.A., 1977. The Geology and mineral resources of Central
Kazakhstan. 151–166 (In Russian).
Liu, J., 2021. The tetrapod fauna of the upper Permian Naobaogou Formation of China:
6. Turfanodon jiufengensis sp. nov. (Dicynodontia). PeerJ 9, e10854. https://doi.
org/10.7717/peerj.10854.
Liu, J., Yi, J., Chen, J.-Y., 2020. Constraining assembly time of some blocks on eastern
margin of Pangea using Permo-Triassic non-marine tetrapod records. Earth Sci. Rev.
207, 103215. https://doi.org/10.1016/j.earscirev.2020.103215.
Liu, D., Fan, Q., Zhang, C., Gao, Y., Du, W., Song, Y., Zhang, Z., Luo, Q., Jiang, Z.,
Huang, Z., 2022. Paleoenvironment evolution of the Permian Lucaogou Formation in
the southern Junggar Basin, NW China. Palaeogeogr. Palaeocimatol. Palaeogeogr.
603, 111198. https://doi.org/10.1016/j.palaeo.2022.111198.
Lucas, S.G., 2005. Age and correlation of Permian tetrapod assemblages from China. In:
Lucas, S.G., Ziegler, K.E. (Eds.), The Nonmarine Permian. New Mexico Museum of
Natural History, Albuquerque, pp. 187–191.
Lucas, S.G., 2018. Permian tetrapod biochronology, correlation and evolutionary events.
SP 450, 405–444. https://doi.org/10.1144/SP450.12.
Lucas, S.G., 2022. Carboniferous tetrapod biostratigraphy, biochronology and
evolutionary events. SP 512, 965–1001. https://doi.org/10.1144/SP512-2021-5.
Lucas, S.G., Ataabadi, M.M., 2010. Tetrapod Footprints from the Upper Carboniferous of
China. Ichnos 17, 163–165. https://doi.org/10.1080/10420940.2010.502497.
Lukin, A.E., Galitsky, I.V., 1974. Bioherms in the lower Permian of Dniepr-Donets Basin.
Doklady Acad. Sci. USSR 215, 170–173 (In Russian).
Marchetti, L., Forte, G., Kustatscher, E., DiMichele, W.A., Lucas, S.G., Roghi, G.,
Juncal, M.A., Hartkopf-Fröder, C., Krainer, K., Morelli, C., Ronchi, A., 2022. The
Artinskian Warming Event: an Euramerican change in climate and the terrestrial
biota during the early Permian. Earth Sci. Rev. 226, 103922. https://doi.org/
10.1016/j.earscirev.2022.103922.
Masumov, A.S., Borisov, O.M., Bensh, F.R., 1978. Verkhniy paleozoy Sredinnogo i
Yuzhnogo Tyan’-Shanya. The upper Paleozoic of the central and southern Tien Shan.
Fan Publishing House, Tashkent, p. 176 (In Russian).
Metcalfe, I., Crowley, J.L., Nicoll, R.S., Schmitz, M., 2015. High-precision U-Pb CA-TIMS
calibration of Middle Permian to lower Triassic sequences, mass extinction and
extreme climate-change in eastern Australian Gondwana. Gondwana Res. 28, 61–81.
https://doi.org/10.1016/j.gr.2014.09.002.
Miletenko, N.V., Fedorenko, O.A., 2002. Atlas of the Lithology-Paleogeographical,
Structural, Palinspastic and Geoenvironmental Maps of Central Eurasia. Scientific
Research Institute of Natural Resources YUGGEO, Almaty, Kazakhstan.
Mizens, G.A., 1997. Upper Paleozoic Flysh of Western Urals, p. 230 (In Russian).
Mogucheva, N.K., 2016. Flora from the Induan Stage (lower Triassic) of Middle Siberia.
Stratigr. Geol. Correl. 24, 252–266.
Montañez, I.P., 2022. Current synthesis of the penultimate icehouse and its imprint on
the Upper Devonian through Permian stratigraphic record. SP 512, 213–245.
https://doi.org/10.1144/SP512-2021-124.
Montanez, I.P., Poulsen, C.J., 2013. The late Paleozoic ice age; an evolving paradigm.
Annu. Rev. Earth Planet. Sci. 41, 629–656. https://doi.org/10.1146/annurev.
earth.031208.100118.
Muromtseva, V.A., 1984. Permian marine deposits and bivalves of Soviet Arctic. Nedra
Publishing House, Leningrad, p. 115 (In Russian).
Naugolnykh, S.V., 2020. Main biotic and climatic events in early Permian of the Western
Urals, Russia, as exemplified by the shallow-water biota of the early Kungurian
lagoons. Palaeoworld 29, 391–404. https://doi.org/10.1016/j.palwor.2018.10.002.
Naugol’nykh, S.V., 2007. Permian flora of the Urals. GEOS, Moscow in Russian.
Naugolnykh, S.V., Linkevich, V.V., 2020. Artinskian flora (lower Permian) of the
stratotypic area (the Middle Cis-Urals). SET 10, 133–150. https://doi.org/10.31862/
2500-2961-2020-10-2-133-150.
Nikishin, A.M. (Ed.), 2005. 400 Million Years of Geological History of the Southern Part
of Eastern Europe. Geos, Moscow (In Russian).
Nikishin, A.M., Ziegler, P.A., Stephenson, R.A., Cloetingh, S.A.P.L., Furne, A.V., Fokin, P.
A., Ershov, A.V., Bolotov, S.N., Korotaev, M.V., Alekseev, A.S., Gorbachev, V.I.,
Shipilov, E.V., Lankreijer, A., Bembinova, E.Y., Shalimov, I.V., 1996. Late
Precambrian to Triassic history of the east European Craton: dynamics of
sedimentary basin evolution. Tectonophysics 268, 23–63. https://doi.org/10.1016/
S0040-1951(96)00228-4.
Nikonov, I.I., Bogatsky, V.I., Martynov, A.V., Larionova, Z.V., Laskin, V.M., Galkina, L.V.,
Dovzhikova, E.G., Ermakova, O., Kostygova, P.K., Kuranova, T.N., Moskalenko, K.A.,
Pankratov, Y.A., Petrenko, E.L., Popova, E.V., Surina, A.I., Shabanova, G.A., 2000.
Timan-Pechora Sedimentary Basin. Atlas of Geological. Paleogeographic Maps.
Rgional Publishing House, Ukhta (In Russian).
Nowak, H., Schneebeli-Hermann, E., Kustatscher, E., 2019. No mass extinction for land
plants at the Permian–Triassic transition. Nat. Commun. 10, 384. https://doi.org/
10.1038/s41467-018-07945-w.
Orlova, E.F., Sadovnikov, G.N., 2006. Microornamentation of Lioestheria, Mimoleaia,
and Echinolimnadia (conchostraca) from the terminal Permian of Siberia. Paleontol.
J. 40, 45–52. https://doi.org/10.1134/S0031030106030075.
Pisarenko, Y.A., Goncharenko, O.P., 2010. Paleogeographical and tectonical traits of
lower Permian halogene formation of South-East margin of Russian Plate. In:
Izvestiya Saratov State University, Section Earth Sciences, 10, pp. 49–58 (In
Russian).
Puchkov, V.N., 2010. Geology of the Urals and Cis-Urals (the Actual Problems of
Stratigraphy, Tectonics, Geodynamics and Metallogeny). UFA, Bashkortostan (In
Russian).
Pyron, R.A., 2011. Divergence Time Estimation using Fossils as Terminal Taxa and the
Origins of Lissamphibia. Syst. Biol. 60, 466–481. https://doi.org/10.1093/sysbio/
syr047.
Rasnitsyn, A.P., Aristov, D.S., Rasnitsyn, D.A., 2015. Dynamics of insect diversity during
the early and Middle Permian. Paleontol. J. 49, 1282–1309. https://doi.org/
10.1134/S0031030115120102.
Rauser-Chernousova, D.M., Ivanova, E.A., Korolyuk, I.K., Morozova, I.P., Fotieva, I.I.,
1977. Characteristic of the stratotype section of Sterlitamak Regional stage (lower
Permian, Shakhtau Massif, Bashkiria). Bull. Moscow Soc. Nat. Studi. Ser. Geol. 52,
24–37 (In Russian).
Ritter, S.M., Meibos, J.K., Robinson, T.S., 2022. Sequence Biostratigraphy of
Carboniferous–Permian Boundary Strata in Western Utah: Deciphering Eustatic and
Tectonic Controls on Sedimentation in the Antler–Sonoma Distal Foreland Basin. In:
Henderson, C.H., Snyder, W.S., Ritter, S.M. (Eds.), Late Paleozoic and Early Mesozoic
Tectonostratigraphy and Biostratigraphy of Western Pangea. SEPM, Society for
Sedimentary Geology, Broken Arrow, Oklahoma, pp. 149–171.
Romano, C., Koot, M.B., Kogan, I., Brayard, A., Minikh, A.V., Brinkmann, W., Bucher, H.,
Kriwet, J., 2016. Permian-Triassic Osteichthyes (bony fishes): diversity dynamics
and body size evolution. Biol. Rev. Camb. Philos. Soc. 91, 106–147. https://doi.org/
10.1111/brv.12161.
Ryabinin, A.N., 1932. The discovery of Theriodontia in the coal-bearing sediments of
Kuznetsk coal Basin. In: News of All-Union Geological-exploration Institute, 50,
pp. 1237–1238 (In Russian).
Schmitz, M.D., Davydov, V.I., 2012. Quantitative radiometric and biostratigraphic
calibration of the Pennsylvanian-early Permian (Cisuralian) time scale and panEuramerican chronostratigraphic correlation. Bull. Geol. Soc. Am. 124, 549–577.
https://doi.org/10.1130/B30385.1.
Schmitz, M.D., Pfefferkorn, H.W., Shen, S.-Z., Wang, J., 2021. A volcanic tuff near the
Carboniferous–Permian boundary, Taiyuan Formation, North China: Radioisotopic
dating and global correlation. Rev. Palaeobot. Palynol. 294, 104244. https://doi.
org/10.1016/j.revpalbo.2020.104244.
Scotese, C.R., 2015. Atlas of Plate Tectonic Reconstructions. Technical Report.
Shen, S.Z., Yuan, D.X., Henderson, C.M., Wu, Q., Zhang, Y.C., Zhang, H., Mu, L.,
Ramezani, J., Wang, X.D., Lambert, L.L., Erwin, D.H., Hearst, J.M., Xiang, L.,
Chen, B., Fan, J., Wang, Y., Wang, W., Qi, Y., Chen, J., Qie, W., Wang, T., 2020.
Progress, problems and prospects: an overview of the Guadalupian Series of South
China and North America. Earth Sci. Rev. 211, 103412. https://doi.org/10.1016/j.
earscirev.2020.103412.
Shen, B., Shen, S., Wu, Q., Zhang, S., Zhang, B., Wang, X., Hou, Z., Yuan, D., Zhang, Y.,
Liu, F., Liu, J., Zhang, H., Shi, Y., Wang, J., Feng, Z., 2022. Carboniferous and
Permian integrative stratigraphy and timescale of North China Block. Sci. China
Earth Sci. 65, 983–1011. https://doi.org/10.1007/s11430-021-9909-9.
Shishkin, M.A., 1998. Tungussogyrinus: a relict neotenic dissorophoid (Amphibia,
Temnospondyli) from the Permo-Triassic of Siberia. Paleontol. J. 32, 521–531 (In
Russian).
Smirnov, A.N., 2020. Reef Formations of the Uchkulach Ore Field. Geology and mineral
resources, No 4, Tashkent, pp. 37–40 (In Russian).
17
V.I. Davydov et al.
Earth-Science Reviews 273 (2026) 105344
Volozh, Y.A., Bykadorov, V.A., Antipov, M.P., Sapozhnikov, R.B., 2016. Paleozoic
sections of Turgai-Syrdarya and Ustyurt region - structural features (related to the
petroleum potential of the cover’s deep layers). NGTP 11, 1–46 (In Russian). 10.17
353/2070-5379/41_2016.
Vyushkov, B.P., 1953. The discovery of terrestrial tetrapods in Krasnoyarsk Formation of
Kuznetsk Basin. Doklady Acad. Sci. USSR 91, 939–941 (In Russian).
Vyushkov, B.P., Emel’yanova, A.I., 1959. The first discovery of the fossil reptile in
Tunguska Bassin, Siberia. Izvestiya Academii Nauk SSSR. Geol. Ser. 111–112 (In
Russian).
Werneburg, R., 2009. The Permotriassic branchiosaurid Tungussogyrinus Efremov, 1939
(Temnospondyli, Dissorophoidea) from Siberia restudied. Fossil Record (Weinheim)
12, 105–120.
Wu, Q., Ramezani, J., Zhang, H., Yuan, D.-X., Erwin, D.H., Henderson, C.M., Lambert, L.
L., Zhang, Y.-c., Shen, S.-z., 2020. High-precision U-Pb zircon age constraints on the
Guadalupian in West Texas, USA. Palaeogeogr. Palaeocimatol. Palaeogeogr. 548,
109668. doi: https://doi.org/10.1016/j.palaeo.2020.109668.
Yang, J., Cawood, P.A., Montañez, I.P., Condon, D.J., Du, Y., Yan, J.-X., Yan, S., Yuan, D.,
2020. Enhanced continental weathering and large igneous province induced climate
warming at the Permo-Carboniferous transition. Earth Planet. Sci. Lett. 534, 116074.
https://doi.org/10.1016/j.epsl.2020.116074.
Young, G.C., 2024. Relative age of the Devonian tetrapod Metaxygnathus, based on the
associated fossil fish assemblage at Jemalong, New South Wales. Alcheringa 45,
278–297.
Yuferev, O.V., 1973. The Carboniferous of the Siberian Biogeographic Realm. Nauka
Publishing House, Novosibirsk.
Zhaimina, V.Y., 2000. Foraminifera and Stratigraphy of Marine Middle Carboniferous
Deposits of North-Eastern Prebalkhashie and Zhungar Alatau. Alma-Ata (In Russian).
Zhu, M., Ahlberg, P.E., Zhao, W., Jia, L., 2002. First Devonian tetrapod from Asia. Nature
420, 760–761. https://doi.org/10.1038/420760a.
Ziegler, P.A., 1989. Evolution of Laurussia: A Study in Late Palaeozoic Plate Tectonics.
Kluwer Academic Publishers, Dordrecht.
Zonenshain, L.P., Kuzmin, M.I., Natapov, L.M., 1990. Geology of the USSR; a platetectonic synthesis.: Geology of the USSR; a plate-tectonic synthesis. Geodynamics 21,
242.
Snyder, W.S., Spinosa, C., Davydov, V.I., Belasky, P., 1994. Petroleum geology of the
southern Pre-Uralian Foredeep with reference to the northeastern Pre-Caspian Basin.
Int. Geol. Rev. 36, 452–472.
Stampfli, G.M., Hochard, C., Vérard, C., Wilhem, C., Raumer, J., 2013. The formation of
Pangea. Tectonophysics 593, 1–19. https://doi.org/10.1016/j.tecto.2013.02.037.
Strok, Y.Y., 1987. Late Permian lakes of Moscow syneclise. In: Martinson, G.G.,
Neustrueva, I.I. (Eds.), The History of the Late Paleozoic and Mesozoic Lakes. Nauka
Publishing House, Leningrad, pp. 128–139 (In Russian).
Suchkova, Y.A., Bakaev, A.S., 2024. The discovery of Chinese Siniphoneus in the middle
Permian of the European Russia. Paleostrat 71–72 (In Russian).
Sukhov, E.E., 2003. Permian Smaller Foraminifera of Biarmian Biogeographic Realm.
Kazan State Unviresity (In Russian), Kazan.
Tananaeva, G.A., Kochieva, N.T., 1983. Structure and metallogeny of Adrasman Caldera,
Western Tian-Shan. Izvestiya Academii Nauk SSSR. Geol. Ser. 86–96 (In Russian).
Upper Permian and lower Triassic sediments of Moscow Syneclise. In: Tikhomirov, S.V.
(Ed.), 1984. Nedra Publishing House (in Russian), Moscow.
Tverdokhlebov, V.P., Tverdokhlebova, G.I., Minikh, A.V., Surkov, M.V., Benton, M.J.,
2005. Upper Permian vertebrates and their sedimentological context in the South
Urals, Russia. Earth Sci. Rev. 69, 27–77. https://doi.org/10.1016/j.
earscirev.2004.07.003.
Tverdokhlebov, V.P., Tverdokhlebova, G.I., Surkov, M.V., 2006. Continental
paleoecosystems of Paleozoic-Mesozoic mark. Paper 2. Late Tatarian (Severodvinian
and Vytakian) time in the south-east of the East-European Platform. News of Higher
Education. Geology and Exploration, pp. 3–12 (In Russian).
Tverdokhlebov, V.P., Tverdokhlebova, G.I., Surkov, M.V., 2007. Continental
paleoecosystems of Paleozoic-Mesozoic mark. In: Paper 3. Late Vyazniki-early Kopan
time in the south-east of the East-European Platform. News of Higher Education.
Geology and exploration, pp. 1–8 (In Russian).
Ueno, K., Arita, M., Meno, S., Sardsud, A., Saesaengseerung, D., 2015. An early Permian
fusuline fauna from southernmost Peninsular Thailand: Discovery of early Permian
warming spikes in the peri-Gondwanan Sibumasu Block. J. Asian Earth Sci. 104,
185–196. https://doi.org/10.1016/j.jseaes.2014.10.030.
Vinogradov, A.P. (Ed.), 1975. Paleogeography of USSR. Volume 2: Devonian,
Carboniferous and Permian Periods. Nedra Publishing House (in Russian), Moscow.
18