Pavel P. Skutschas

Mesozoic salamanders and albanerpetontids of Middle Asia, Kazakhstan, and Siberia

Mesozoic terrestrial deposits containing diverse vertebrate assemblages are widely distributed in Siberia (central and eastern part of Russia), Middle Asia (Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan), and Kazakhstan. Twelve formations of Middle Jurassic (Bathonian) to Late Cretaceous (Campanian) age in the region contain salamanders (six in Middle Asia, two in Siberia and four in Kazakhstan). In contrast to the situation in Euramerica, albanerpetontids are extremely rare in the Mesozoic of Asia, where their fossil record is limited to the Khodzhakul (Cenomanian) and Bissekty (Turonian) formations, both in Uzbekistan. Salamanders in Siberia are known from the Bathonian Itat Formation in the Krasnoyarsk Region (the stem salamander Urupia monstrosa and two undescribed taxa—a new stem salamander and a possible crown-group salamander) and from the Aptian–Albian Ilek Formation in Kemerovo Province and the Krasnoyarsk Region (the crown-group salamander Kiyatriton leshchinskiyi and Caudata indet.). In the Jurassic of Middle Asia, the stem salamanders Kokartus honorarius and Karauridae indet. are known from the Bathonian–Callovian Balabansai Formation in Kyrgyzstan. Younger records in Middle Asia are restricted to only two Late Cretaceous genera of crown-group salamanders: the possible cryptobranchoid Nesovtriton in the Bissekty Formation (Turonian) and the cryptobranchid Eoscapherpeton in the Khodzhakul, Dzharakuduk, Bissekty, and Aitym formations (collectively Cenomanian–Campanian) in Uzbekistan and the Yalovach Formation (Santonian) in Tajikistan. In Kazakhstan, salamanders are known from the Kimmeridgian Karabastau Formation (the stem salamander Karaurus sharovi), the Turonian Zhirkindek Formation (Caudata indet.), the Santonian–Campanian Bostobe Formation (the cryptobranchid Eoscapherpeton, the possible proteid “Bishara backa” and Caudata indet.) and the Campanian Darbasa Formation (the cryptobranchid Eoscapherpeton). Cenomanian–Campanian vertebrate assemblages in Middle Asia and Kazakhstan are characterised by dominance of the cryptobranchid Eoscapherpeton.

A eutherian mammal from the Early Cretaceous of Russia and biostratigraphy of the Asian Early Cretaceous vertebrate assemblages

Prokennalestes abramovi n.sp. is described based on M2 from the upper Barremian-middle Aptian (Early Cretaceous) Mogoito locality in Transbaikalia, Russia. It differs from the Mongolian species of Prokennalestes (Khoboor, early Albian) by a combination of one primitive character (steeper and shorter lingual slopes of the paracone and metacone), one more derived character (larger size), and some characters of uncertain polarity (small preparastyle, lack of labial cuspules along the ectoflexus). P. abramovi n.sp. is the oldest eutherian mammal so far described, and its discovery extends the known geological range of Eutheria by 10–15 Ma. The Tsagantsabian land-vertebrate biochron can be defined by a dominance of sinemyid turtles; the Khukhtekian by a dominance of macrobaenids.

The first ‘true’ Adocus (Testudines, Adocidae) from the Paleogene of Asia

ABSTRACT This paper describes a new species of the genus Adocus (A. inexpectatus, sp. nov.), based on an almost complete shell from the upper Eocene Youganwo (= Youkanwo) Formation of the Maoming Basin, China. The inclusion of A. inexpectatus in a phylogenetic analysis of Adocusia resulted in a polytomy with Adocus aksary and A. amtgai (both from the Upper Cretaceous of Asia). This clade formed a polytomy with the North American species of Adocus. Like other ‘true’ Adocus, A. inexpectatus has overlapping of the marginals onto the costals in the middle and posterior parts of the carapace and sculpturing of the shell surface with small grooves and pits. Thus, A. inexpectatus represents the first ‘true’ Adocus from the Paleogene of Asia. Other specimens from the Paleogene of Asia that have been referred to Adocus, characterized by shell sculpturing with small dots and unknown condition of the marginal/costal overlapping, are distinct from ‘true’ Adocus and herein referred to as ‘Adocus’ spp. Here we also report the presence of ‘Adocus’ from the Paleocene of North America. Our study indicates that the evolutionary and biogeographic history of the Adocidae was more complicated than considered previously, including previously unrecognized dispersal events between Asia and North America. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Re-Evaluation of Mynbulakia Nesov, 1981 (Lissamphibia: Caudata) and Description of a New Salamander Genus from the Late Cretaceous of Uzbekistan

ABSTRACT Isolated skull and postcranial bones previously assigned to the monotypic batrachosauroidid salamander genus Mynbulakia Nesov, 1981 (Uzbekistan, Byssekty Formation, Turonian) are re-interpreted as a mixture of two salamander taxa. The holotype maxilla of Mynbulakia surgayi Nesov, 1981, and dentaries, parietals, and femora previously referred to that species belong to smaller and, presumably, younger individuals of the cryptobranchid Eoscapherpeton asiaticum Nesov, 1981. Atlantes and trunk vertebrae previously referred to M. surgayi, along with additional vertebrae collected more recently from the Byssekty Formation, belong to Nesovtriton mynbulakensis gen. et sp. nov.. The structure of the atlas, the absence of spinal nerve foramina in the trunk and anterior caudal vertebrae, and the presence of unicipital transverse processes on the trunk vertebrae suggest that N. mynbulakensis may be a member of the Cryptobranchoidea. Two salamander taxa (E. asiaticum and N. mynbulakensis) are currently known from the Bissekty Formation and no salamander families are shared between the Late Cretaceous tetrapod assemblages of Asia and Euramerica.

A New Salamander from the Late Paleocene—Early Eocene of Ukraine

A new neotenic salamander, Seminobatrachus boltyschkensis gen. et sp. nov., is described based on 14 skeletons of late Paleocene—early Eocene age preserved on drill core slabs from the Cherkassy Region, central Ukraine. The new taxon is diagnosed by the following unique combination of characters: dorsal process of premaxilla posteriorly elongate and overlaps frontal; maxilla greatly reduced in size; parietal—squamosal contact absent; vomerine tooth row long and parallel to maxillary arcade; pterygoid has long anterior process; quadrate ossified; marginal and palatal teeth pedicellate; trunk vertebrae amphicoelous, each having a subcentral keel, anterior basapophysis, and spinal nerve foramina; ribs bicipital; carpals and tarsals unossified; and phalangeal formulae of 2-2-3-2 and 2-2-3-4-2 for manus and pes, respectively. Phylogenetic analysis nests S. boltyschkensis within Urodela (i.e., crown-clade salamanders), but its exact phylogenetic position is equivocal, resolving in one of three ways: (1) in an unresolved trichotomy with Salamandra and (Ambystomatidae + (Dicamptodon + Rhyacotriton)) (results obtained in NONA v. 2.0, with the WINCLADA v. 1.00.08 interface; the parsimony ratchet (island hopper) algorithm), (2) as a sister taxon of (Salamandra + (Ambystomatidae + (Dicamptodon + Rhyacotriton))) clade (results obtained in TNT v. 1.1; the implicit enumeration search algorithm) or (3) as a sister taxon of Ambystomatidae (results obtained in PAUP v. 4.0b10; the branch-and-bound search algorithm).

The First Discovery of an Alligatorid (Crocodylia, Alligatoroidea, Alligatoridae) in the Eocene of China

SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

The paleoenvironments of azhdarchid pterosaurs localities in the Late Cretaceous of Kazakhstan

Abstract Five pterosaur localities are currently known from the Late Cretaceous in the northeastern Aral Sea region of Kazakhstan. Of these, one is Turonian-Coniacian in age, the Zhirkindek Formation (Tyulkili), and four are Santonian in age, all from the early Campanian Bostobe Formation (Baibishe, Akkurgan, Buroinak, and Shakh Shakh). All so far collected and identifiable Late Cretaceous pterosaur bones from Kazakhstan likely belong to Azhdarchidae: Azhdarcho sp. (Tyulkili); Aralazhdarcho bostobensis (Shakh Shakh); and Samrukia nessovi (Akkurgan). These latter two taxa, both from the Bostobe Formation might be synonyms. Azhdarcho sp. from the Zhirkindek Formation lived in a tropical-to-subtropical relatively humid climate on the shore of an estuarine basin connected to the Turgai Sea. Known fossils were collected in association with brackish-water bivalves and so the overall paleoenvironment of this pterosaur was likely an estuarine marsh as indicated by the dominance of conifers and low relative counts of ferns and angiosperms. Aralazhdarcho bostobensis, from the Bostobe Formation, lived on a coastal fluvial plain along the Turgai Sea. This paleoenvironment was either floodplain (Akkurgan, Buroinak, and Shakh Shakh) or estuarine (Baibishe). In the Santonian – early Campanian, shallow waters near this coastal plain were sites for the intensive accumulation of phosphates under upwelling conditions caused by strong winds from the ancient Asian landmass. These winds also caused significant aridization of the climate during this time. We speculate that pterosaurs may have been attracted to this area by the abundant resources in the bio-productive estuaries and nearshore upwelling waters.

First nimravid skull from Asia.

Maofelis cantonensis gen. and sp. nov. is described based on a complete cranium from the middle-upper Eocene Youganwo Formation of Maoming Basin, Guangdong Province, China. The new taxon has characters diagnostic for Nimravidae such as a short cat-like skull, short palate, ventral surface of petrosal dorsal to that of basioccipital, serrations on the distal carina of canine, reduced anterior premolars, and absence of posterior molars (M2-3). It is plesiomorphic nimravid taxon similar to Nimravidae indet. from Quercy (France) in having the glenoid pedicle and mastoid process without ventral projections, a planar basicranium in which the lateral rim is not ventrally buttressed, and P1 present. The upper canine is less flattened than in other Nimravidae. Maofelis cantonensis gen. and sp. nov. exemplifies the earliest stage of development of sabertooth specialization characteristic of Nimravidae. This taxon, together with other middle-late Eocene nimravid records in South Asia, suggests origin and initial diversification of Nimravidae in Asia. We propose that this group dispersed to North America in the late Eocene and to Europe in the early Oligocene. The subsequent Oligocene diversification of Nimravidae took place in North America and Europe, while in Asia this group declined in the Oligocene, likely because of the earlier development of open habitats on that continent.

A new crown-group salamander from the Middle Jurassic of Western Siberia, Russia

A new crown-group salamander, Kiyatriton krasnolutskii sp. nov., from the Middle Jurassic (Bathonian) Itat Formation of the Berezovsk Quarry locality in Western Siberia, Russia, is described on the basis of new material and a dentary fragment previously referred to the undescribed salamander taxon “Berezovsk salamander B” (sensu Skutschas2013). Kiyatriton krasnolutskii sp. nov. differs from K. leshchinskiyi (type species of the genus Kiyatriton) in that the ventrolateral ridges on the atlas are sharper anteriorly, more ventrally oriented and reach the anterior cotylar rims and that the dentary has a relatively taller dental parapet. Kiyatriton krasnolutskii sp. nov. is one of the oldest salamanders in the fossil record. The finding of Kiyatriton krasnolutskii sp. nov. in Berezovsk Quarry is significant for: (1) clarifying that the previously reported “Berezovsk salamander B” is a crown-group salamander of the genus Kiyatriton; (2) extending the stratigraphic range of the genus Kiyatriton backward some 40 million years into the Bathonian, from the previously youngest record in the Aptian–Albian; (3) indicating that K. leshchinskiyi from the Aptian–Albian Shestakovo locality in Western Siberia, Russia, survived as a relic into the Early Cretaceous of present-day Western Siberia; (4) supporting the hypothesis that Bathonian vertebrate faunas of Europe and Western Siberia were homogeneous; and (5) suggesting that all Bathonian crown-group salamanders in Asia could be members of one cryptobranchoid clade and could represent the first radiation of Cryptobranchoidea.

Long bone histology of the stem salamander Kokartus honorarius (Amphibia: Caudata) from the Middle Jurassic of Kyrgyzstan

Kokartus honorarius from the Middle Jurassic (Bathonian) of Kyrgyzstan is one of the oldest salamanders in the fossil record, characterized by a mixture of plesiomorphic morphological features and characters shared with crown‐group salamanders. Here we present a detailed histological analysis of its long bones. The analysis of a growth series demonstrates a significant histological maturation during ontogeny, expressed by the progressive appearance of longitudinally oriented primary vascular canals, primary osteons, growth marks, remodelling features in primary bone tissues, as well as progressive resorption of the calcified cartilage, formation of endochondral bone and development of cartilaginous to bony trabeculae in the epiphyses. Apart from the presence of secondary osteons, the long bone histology of Kokartus is very similar to that of miniaturized temnospondyls, other Jurassic stem salamanders, miniaturized seymouriamorphs and modern crown‐group salamanders. We propose that the presence of secondary osteons in Kokartus honorarius is a plesiomorphic feature, and the loss of secondary osteons in the long bones of crown‐group salamanders as well as in those of miniaturized temnospondyls is the result of miniaturization processes. Hitherto, all stem salamander long bong histology (Kokartus, Marmorerpeton and ‘salamander A’) has been generally described as having paedomorphic features (i.e. the presence of Katschenkos Line and a layer of calcified cartilage), these taxa were thus most likely neotenic forms. The absence of clear lines of arrested growth and annuli in long bones of Kokartus honorarius suggests that the animals lived in an environment with stable local conditions.