Karauridae

Abstract: 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.

Abstract: Larval and metamorphosed Ferganobatrachus riabinini (Temnospondyli, Brachyopoidea), metamorphosed Kokartus honorarius (Caudata, Karauridae), an indeterminated karaurid (Karauridae indet.) and, presumably, anurans (?Anura indet.) are represented by isolated cranial and postcranial skeletal elements in the Middle Jurassic (Bathonian–Callovian) Balabansai Svita of the Fergana Depression, Kyrgyzstan. The Balabansai vertebrate assemblage is one of the few faunas in which non-lissamphibian temnospondyls, stem caudates and anurans occur together. The presence of a supraglenoid foramen and a complex strap-like glenoid on the scapulocoracoid in Kokartus supports its basal phylogenetic position within the Caudata.

Abstract: 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 Katschenko's 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.