卷 50, 编号 3 (2016)

The latest representative of the family Ptychocaulidae, Medfracaulus sinelnikovae sp. nov., is described from the Moscovian Stage of the Moscow Basin. Morphology of Ptychocaulidae, their taxonomy and distribution are discussed, and the species composition of the genus Medfracaulus is considered.

The shell microstructure of the Lower Cretaceous Suiaella weberi Moisseev, 1949 (superfamily Norelloidea) from the Lower Barremian of Crimea is studied for the first time. The fibers of Suiaella are shown to differ strongly in size and outline of cross section from the fibers of the superfamily Rhynchonelloidea. Suiaella is shown to differ from rhynchonellids of the superfamily Basilioloidea in the presence of straight or slightly curved fibers and absence of twisted fibers and overlapping adjacent fibers within one and the same bundle, it also differs in the presence of capillation and fine ribbing. Numerous cell imprints of the mantle outer epithelium have been found in fossil Norelloidea for the first time.

Species attributed to Scoliocystis Jaekel, 1899, including the type species S. pumila (Eichwald, 1860) and S. thersites Jaekel, 1899 from the Ordovician of the Leningrad Region, are reviewed. Scoliocystis sp. from the Upper Ordovician of Estonia, figured by Hecker (1964), is redescribed as Maennilocystis heckeri gen. et sp. nov. and it is attributed to the family Callocystitidae Bernard, 1895. The genus Scoliocystis is intermediate between the families Cheirocrinidae and Echinoencrinitidae in having five periproct border plates (as in cheirocrinids), but lacking plate R5 and having a reduced oral area, as in echinoencrinitids, but is retained in the Echinoencrinitidae. The similarity of Scoliocystis to the unusual North American cheirocrinid genus Sprinkleocystis is convergent. The genus Gonocrinites Eichwald, 1840, with two species, is restored among echinoencrinitids, as having four periproct border plates, whereas Echinoencrinites sensu stricto has three. The families Echinoencrinitidae and Callocystitidae arose from cheirocrinids with closed plate circlets by the loss of plate R5 and substitution of radial:lateral for radial:radial pectinirhombs. In addition, echinoencrinitids are characterized by a reduced oral area, whereas in callocystitids, the recumbent ambulacra are extensive. Scoliocystis is a stem-group genus to Echinoencrinitidae plus Callocystitidae. Several glyptocystitoid genera independently developed advanced pectinirhombs.

Fossil remains of beetles are described from two Lower Triassic localities: Entala (Induan) and Tikhvinskoe (Olenekian). Only one beetle fossil was previously known from the Lower Triassic of Tikhvinskoe. The fossils are rather few and poorly preserved, but they are worth describing as finds rare for the Lower Triassic. Five fossils from Entala most probably belong to beetles of the same species of the formal genus Pseudochrysomelites. Beetles of this genus are especially abundant in deposits close to the Permian–Triassic boundary and can be considered “disaster taxa.” There are no known cases, either in the Permian or in the Middle–Upper Triassic, of a random sample of five specimens belonging to a single species. This suggests that in the Entala oryctocenosis the species diversity of beetles is extremely low. All three beetle fossils found in Tikhvinskoe belong to beetles of different species, showing that diversity had already started to increase. However, it remained low, and all fossils belong to the formal family Schizocoleidae, and two of the three belong to the same genus, Pseudochrysomelites. The Khei-Yaga locality, which immediately follows Tikhvinskoe in time (topmost Olenekian or early Anisian), already contains beetles of the families Asiocoleidae and Permosynidae. In the Lower Anisian of the Buntsandstein, such typical Mesozoic beetles as Cupedidae and Coptoclavidae have been recorded. The appearance of such advanced beetles as early as the Lower Anisian suggests that the famous Permian–Triassic crisis was not as deep as it is usually believed, and many beetles survived it, disappearing, however, from the fossil record in the Early Triassic.

Two new genera (monotypic Samarabatrachus gen. nov. (S. bjerringi sp. nov.) and Syrtosuchus gen. nov. (including S. samarensis (Sennikov, 1981) and S. morkovini sp. nov) and a new species of the genus Selenocara Bjerring (S. rossica sp. nov.) are described based on revision of the original material of the form previously known as Wetlugasaurus samarensis. The genera Selenocara and Samarabatrachus gen. nov. positioned at the base of radiation of Triassic capitosaurids are combined into a new subfamily, Selenocarinae subfam. nov. The genus Syrtosuchus gen. nov., which is undoubtedly a derivative of early capitosaurids (Selenocara or a closely related genus), shows some typical benthosuchid features and is assigned to a separate benthosuchid subfamily, Syrtosuchinae subfam. nov. The diagnoses of the genera Wetlugasaurus Riabinin and Selenocara are amended. For the territory of the Obschii Syrt Highland, the genera Selenocara, Samarabatrachus gen. nov., and Syrtosuchus gen. nov. are regarded as key members of a separate Early Triassic tetrapod assemblage (Selenocara–Syrtosuchus Fauna), which is intermediate between the Tupilakosaurus and Benthosuchus faunas and dated Late Induan (Dienerian).