A relict stem salamander: Evidence from the Early Cretaceous of Siberia

The early evolution of salamanders, which are one of the three living groups of lissamphibians, is not well known. Both stem- and crown-group salamanders first appeared in the Middle Jurassic (Bathonian), but subsequently had different evolutionary histories: stem salamanders were thought to have gone extinct in the Late Jurassic, while crown salamanders persist to the present day. Here, I report the discovery of an indeterminate stem salamander in the Lower Cretaceous (Aptian–Albian) Ilek Formation of Western Siberia. This is new evidence that the most basal salamanders survived beyond the Jurassic–Cretaceous boundary and co-existed with crown-group salamanders during approximately the first 40 million years of the known history of salamanders. The recognition of stem salamanders in the Early Cretaceous of Western Siberia adds to the inventory of taxa that suggest this area was a refugium for various groups of vertebrates with Jurassic affinities

On a record of Choristoderes (Diapsida, Choristodera) from the Lower Cretaceous of Western Siberia

Fossil remains (fragmentary dentaries and vertebrae) of Choristodera indet. from the Lower Cretaceous Shestakovo 1 locality (Kemerovo Region, Russia) are described. The taxon from Shestakovo is characterized by primitive vertebral features (fused neural arches and centra of the cervical vertebrae, elongated dorsal vertebrae) combined with the presence of dentin folds at the tooth bases (advanced character typical of neochoristoderes). Phylogenetic relationships of the form from Shestakovo and other Choristodera are uncertain

The first dinosaur egg from the Lower Cretaceous of Western Siberia, Russia

© 2017 Informa UK Limited, trading as Taylor & Francis Group The Lower Cretaceous Ilek Formation in Western Siberia (Russia) has yielded various vertebrate fossils, including skeletal remains of dinosaurs. Here we report on a fragmentary theropod egg from the vertebrate locality Shestakovo 3 of the Ilek Formation in Kemerovo Province. We assign the specimen to the oogenus Prismatoolithus (oofamily Prismatoolithidae) as Prismatoolithus ilekensis oosp. nov., on the basis of the following unique combination of characters: ovoid-shaped egg; thin eggshell 300–330 μm thick; angustiprismatic morphotype; eggshell with three different layers; gradual transition between mammillary layer and prismatic layer; abrupt contact between prismatic layer and external layer; mammillary layer to prismatic layer to external layer thickness ratio is 1:3:0.6; prismatic layer with ill-defined squamatic texture; angusticanaliculate pore system; and smooth outer surface. Like other Early Creataceous Prismatoolithus, the egg of Prismatoolithus ilekensis oosp. nov. was laid by a small bodied theropod dinosaur (troodontid or primitive bird) and this taxonomic attribution is supported by results of our phylogenetic analysis. Prismatoolithus ilekensis oosp. nov. is the first Early Cretaceous ootaxon from Russia. urn:lsid:zoobank.org:act:734EAD40-86C3-488B-A61E-B5FF7378BC0

A tritylodontid synapsid from the Middle Jurassic of Siberia and the taxonomy of derived tritylodontids

© 2017, © by the Society of Vertebrate Paleontology. Upper and lower tritylodontid postcanine teeth from the Middle Jurassic (Bathonian) Itat Formation of the Berezovsk coal mine, Krasnoyarsk Territory, Russia, are referred to Stereognathus sp. The genus Stereognathus Charlesworth, 1855 (Polistodon He and Cai, 1984, Xenocretosuchus Tatarinov and Mashenko, 1999, and Montirictus Matsuoka et al., 2016, are new synonyms), is similar to Bocatherium and differs from all other tritylodontids in having an upper postcanine cusp formula of 2:2:2. It differs from Bocatherium in the quadrangular shape of the upper postcanine teeth. Stereognathus also differs from all other tritylodontids in having a more elaborate interlocking system in the upper postcanine teeth, each of which bears a mesial cingulum connecting cups B0, M0, and L0. Stereognathus shares with Bienotheroides single-rooted lower postcanine teeth, and these two genera are closely related. Discovery of Stereognathus in the Itat Formation underlines the similarity of the vertebrate assemblage from this stratigraphic unit to the British Bathonian vertebrate assemblages and the Early Cretaceous vertebrate fauna from the Ilek Formation in Siberia. The presence of Stereognathus during an ∼40 Ma time interval in Siberia suggests a long stasis in the evolution of the vertebrate faunas of this region. Citation for this article: Averianov, A. O., T. Martin, A. V. Lopatin, J. A. Schultz, P. P. Skutschas, R. Schellhorn, and S. A. Krasnolutskii. 2017. A tritylodontid synapsid from the Middle Jurassic of Siberia and the taxonomy of derived tritylodontids. Journal of Vertebrate Paleontology DOI: 10.1080/02724634.2017.1363767

3D bite modeling and feeding mechanics of the largest living amphibian, the Chinese Giant Salamander Andrias davidianus (Amphibia:Urodela)

Biting is an integral feature of the feeding mechanism for aquatic and terrestrial salamanders to capture, fix or immobilize elusive or struggling prey. However, little information is available on how it works and the functional implications of this biting system in amphibians although such approaches might be essential to understand feeding systems performed by early tetrapods. Herein, the skull biomechanics of the Chinese giant salamander, Andrias davidianus is investigated using 3D finite element analysis. The results reveal that the prey contact position is crucial for the structural performance of the skull, which is probably related to the lack of a bony bridge between the posterior end of the maxilla and the anterior quadrato-squamosal region. Giant salamanders perform asymmetrical strikes. These strikes are unusual and specialized behavior but might indeed be beneficial in such sit-and-wait or ambush-predators to capture laterally approaching prey. However, once captured by an asymmetrical strike, large, elusive and struggling prey have to be brought to the anterior jaw region to be subdued by a strong bite. Given their basal position within extant salamanders and theirPeer ReviewedPostprint (published version

A relict stem salamander: Evidence from the Early Cretaceous of Siberia

The early evolution of salamanders, which are one of the three living groups of lissamphibians, is not well known. Both stem- and crown-group salamanders first appeared in the Middle Jurassic (Bathonian), but subsequently had different evolutionary histories: stem salamanders were thought to have gone extinct in the Late Jurassic, while crown salamanders persist to the present day. Here, I report the discovery of an indeterminate stem salamander in the Lower Cretaceous (Aptian–Albian) Ilek Formation of Western Siberia. This is new evidence that the most basal salamanders survived beyond the Jurassic–Cretaceous boundary and co-existed with crown-group salamanders during approximately the first 40 million years of the known history of salamanders. The recognition of stem salamanders in the Early Cretaceous of Western Siberia adds to the inventory of taxa that suggest this area was a refugium for various groups of vertebrates with Jurassic affinities

Une salamandre géante « préglaciaire » d’Europe : nouveau signalement du Pliocène supérieur du Caucase

Des os crâniens et post-crâniens désarticulés d’une salamandre géante (Cryptobranchidae : Andrias sp.) ont été trouvés dans les dépôts du Pliocène supérieur de la localité de Belorechensk dans le Caucase du Nord. Ces restes appartenaient probablement à un individu décédé au cours de la phase de croissance rapide et d’une longueur totale d’environ 90 à 100 cm. La salamandre géante de Belorechensk est l’une des plus récentes et des plus connues d’Europe.Disarticulated cranial and postcranial bones of a giant salamander (Cryptobranchidae: Andrias sp.) were found in the Upper Pliocene deposits of the Belorechensk locality in the Northern Caucasus. These remains probably belonged to one individual that died during a stage of rapid growth and had a total length of about 90-100 cm. The giant salamander from Belorechensk is among the geologically youngest and the easternmost known in Europe.</p