A recent contribution published in this journal (Dias−daSilva and Ilha 2009) reported a dermal skull fragment indicating the presence of a putative plagiosauroid temnospondyl in the Lower Triassic Sanga do Cabral Formation of the Paraná Basin, Southern Brazil. The taxonomic assignation of this specimen was necessarily tentative as it was based on circumstantial evidence, specifically the presence of a dense pustular ornamentation over four partial dermal skull bones, consideration of the described taxa known to bear such ornamentation, and the stratigraphic and paleobiogeographic range of such taxa. Therefore, Diasda−Silva and Ilha (2009) could not be totally certain about the plagiosauroid affinities of the new specimen and ascribed it to ?Plagiosauridae. It was particularly difficult to make a precise osteological identification of the specimen and six alternative osteological interpretations were made in comparison to both Gerrothorax and Peltobatrachus (see Dias−da−Silva and Ilha 2009: fig. 2). In spite of the poor taxonomic resolution, the new specimen raised interesting questions regarding the presence of plagiosauroid stereospondyls in western Gondwana, as well as their evolutionary patterns, biostratigraphic and paleobiogeographic implications. After Dias−da−Silva and Ilha's (2009) contribution was published, new data from Damiani et al. (2009) raised the possibility of narrowing down the taxonomic identity of the plagiosauroid from Brazil. Accordingly, this brief report provides a more precise taxonomic assignation for this material.
The Late Carboniferous amphibian genus Limnerpeton Fritsch, 1881 is revised on the basis of the type specimens of the eight original species described by Fritsch using material from Nýřany, Třemošná and Kounov, now in the Czech Republic. The type species Limnerpeton modestum is a nomen dubium restricted to a mandible that almost certainly belongs to an amphibamid temnospondyl but is not critically diagnostic. “Limnerpeton” laticeps and “Limnerpeton” macrolepis lectotypes are both small individuals of the same taxon as the later described Mordex calliprepes Steen, 1938 and thus form part of the hypodigm of Mordex laticeps comb. nov. “Limnerpeton” elegans is now Limnogyrinus elegans and is a member of the temnospondyl family Micromelerpetontidae. “Limnerpeton” obtusatum is a specimen of the microsaur Microbrachis pelikani. “Limnerpeton” dubium is an indeterminate tetrapod, probably either a temnospondyl or a pelycosaur. “Limnerpeton” difficile is a nomen dubium but the type is probably a small specimen of the tuditanomorph microsaur Crinodon limnophyes. “Limnerpeton” caducum is almost certainly a specimen of the ophiderpetontid aïstopod Oestocephalus granulosus. Several other described small temnospondyls from Nýřany are discussed and shown to be specimens of either Limnogyrinus elegans, Mordex laticeps or Amphibamidae incertae sedis. The tetrapod fauna at Nýřany includes four dissorophoid temnospondyls as proposed by Milner (1986) but with two changes in nomenclature. They comprise the branchiosaurid Branchiosaurus salamandroides, the micromelerpetontid Limnogyrinus elegans, the amphibamid Platyrhinops cf. lyelli and the primitive trematopid Mordex laticeps. These represent four of the five major dissorophoid families and demonstrate that the group had already diversified by the late Westphalian.
Limnogyrinus elegans (Fritsch) is the most primitive micromelerpetontid temnospondyl from the Upper Carboniferous of Nýřany, Czech Republic. Arecent revision of the taxon by Werneburg (1994) attributed to this species a skull in dorsal aspect which was significantly larger than any previously reported and showed evidence of snout elongation. Restudy of this specimen demonstrates it to be a skull, visible in ventral aspect, of a juvenile of Cochleosaurus bohemicus, a more primitive edopoid temnospondyl, which is frequent in the Nýřany assemblage. Werneburg’s diagnosis of Limnogyrinusis revised and the problems of constructing ontogenetic series are discussed.
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