Latest Literature

Some new papers, one on the phylogeny of the Parareptilia and two on the Permian branchisaurid Apateon. I know that the last two are not Triassic but they are close enough! Plus, more papers on temnospondyls.

Tsuji L. A. and J. Muller. 2009. Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade. Fossil Record 12:71-81. DOI 10.1002/mmng.200800011

ABSTRACT - In the present study, the historical development of Parareptilia as a phylogenetically valid clade is summarized, and for the first time a modern phylogenetic definition of both Parareptilia as well as Eureptilia is presented, which will facilitate the study of problems of early amniote classification. Furthermore, a preliminary study of the rates of diversification in parareptiles is performed on the basis of topological information on species diversity. While acknowledging that the bias of the fossil record also needs to be considered for a more definitive statement on parareptile diversification, our results show that a significant increase in diversification rate could be recorded only among Triassic procolophonoids, making it difficult to interpret evolutionary novelties such as herbivory or impedance-matching hearing as being key innovations that might have driven diversification.

Witzmann, F. 2009. Cannibalism in a small growth stage of the Early Permian branchiosaurid Apateon gracilis (Credner, 1881) from Saxony. Fossil Record 12:7-11. DOI 10.1002/mmng.200800006

ABSTRACT - An almost complete specimen of the branchiosaurid temnospondyl Apateon gracilis (Credner, 1881) with a skull length of approximately 7 mm from the Early Permian Dohlen Basin in Saxony is described that possesses a nearly complete conspecific specimen of approximately 4 mm skull length in its digestive tract. This is the first evidence of cannibalistic behaviour in small growth stages of branchiosaurids, whose dentition and hyobranchial morphology suggest adaptations to the capture of small invertebrates and feeding on small phyto- and zooplankton by filtering from the water. Therefore, cannibalism in small branchiosaurids certainly represents an exceptional case, possibly triggered by unfavourable environmental conditions.

Frobisch, N.B., and R.R. Schoch. 2009. The largest specimen of Apateon and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae. Fossil Record 12:83-90. DOI 10.1002/mmng.200800012

ABSTRACT - Two distinct developmental trajectories, metamorphosis and neoteny (the retention of larval somatic features in adult animals), have been reported for the small gill-bearing branchiosaurids of the Late Carboniferous and Early Permian of central Europe. Based on a very large specimen of the species Apateon caducus (Ammon, 1889), anatomical features characteristic for the neotenic phenotype of branchiosaurids are described. Large neotenes lack changes that occur during a short phase of transformation into terrestrial adults (metamorphosis), such as ossification of the braincase and palatoquadrate and intercentra, further ossification of the girdles and formation of muscle attachment scars and processes on the limb bones. They also lack a distinct sculpturing of the dermal skull roofing elements with deep polygonal ridges and grooves. Instead, larval somatic features are retained including ossified branchial denticles indicative of open gill slits and accentuated larval-type sculpturing of the dermal skull roof. Large size, high degree of ossification as compared to the larvae, and the presence of uncinate processes on the ribs clearly demonstrate an adult ontogenetic stage. Neotenes remained in the aquatic environment throughout their life and were most likely not capable of effective terrestrial locomotion. The frequency distribution of the two phenotypes in modern salamander populations and the environmental cues that influence the development of them provide a comparative framework for the discussion of the evolution of the two life history pathways in branchiosaurids.

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