Falconnet, J., Andriamihaja, M., Läng, É., and J.-S. Steyer. 2012. First procolophonid (Reptilia, Parareptilia) from the Lower Triassic of Madagascar. Comptes Rendus Palevol (advance online publication) http://dx.doi.org/10.1016/j.crpv.2012.04.001
Abstract - Lasasaurus beltanae nov. gen. nov. sp., a new procolophonid (Reptilia, Parareptilia) from the Lower Triassic of Madagascar, is represented by a single partial skeleton preserved in a ferro-calcareous nodule from the Middle Sakamena Formation, in the North of the island. This new taxon is unique in possessing peculiar, fine and dendritic crests running along the posterolateral side of the squamosal, widely spaced maxillary teeth, subparallel mesiodistal ridges connecting maxillary teeth to the tooth row, and a strongly acute anterior margin of the copula (hyoid bone). This well-preserved specimen belongs to a juvenile individual. The inclusion of L. beltanae nov. gen. nov. sp. in a phylogenetic analysis suggests that it is close to Theledectinae, Procolophoninae, and Leptopleurinae, though their respective relationships are uncertain. This specimen is the first procolophonid described from Madagascar and represents a minor terrestrial component of a coastal vertebrate assemblage dominated by amphibious to fully-aquatic taxa.
Showing posts with label Parareptilia. Show all posts
Showing posts with label Parareptilia. Show all posts
2010 Paper on the Osteology of the Procolophonid Leptopleuron lacertinum Owen
Thanks to Ian Corfe for bringing this to my attention:
Säilä, L. K. 2010. Osteology of Leptopleuron lacertinum Owen, a procolophonoid parareptile from the Upper Triassic of Scotland, with remarks on ontogeny, ecology and affinities. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 101, 1–25.
Abstract - The Late Triassic reptile Leptopleuron lacertinum Owen, 1851 is described for the first time in full anatomical detail, based on newly produced silicone and plastic casts of the numerous specimens preserved as natural moulds. Previously, only the braincase has been described from these detailed casts. Leptopleuron is reconstructed as a 270-mm-long reptile with a long tail, although it is possible that even the largest known specimens were still sub-adults. Within Procolophonoidea, Leptopleuron is distinguished by the following non-braincase autapomorphies: two flattened, triangular spines of equal size on the quadratojugal; V-shaped groove on the jugal; the anterior tip of the jugal in contact with the posterolateral extension of the nasal; minimal contact between the jugal and the postorbital; frontals narrow anterior to the orbitotemporal openings; the vomerine dentition consisting of a tall and a short pair of fangs; broad medial ridge of pleurocentra of the dorsal vertebrae divided into three separate ridges by two deep grooves on each pleurocentrum; distinct three-fold depression pattern on the ventral side of ischium; and the first phalanx on the fifth pedal digit being long and slim. Leptopleuron shares some features with living sand lizards and might have lived a burrowing lifestyle. The dentition and body shape of Leptopleuron imply it ate a diet of fibrous plant material or hard-shelled invertebrates.
Säilä, L. K. 2010. Osteology of Leptopleuron lacertinum Owen, a procolophonoid parareptile from the Upper Triassic of Scotland, with remarks on ontogeny, ecology and affinities. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 101, 1–25.
Abstract - The Late Triassic reptile Leptopleuron lacertinum Owen, 1851 is described for the first time in full anatomical detail, based on newly produced silicone and plastic casts of the numerous specimens preserved as natural moulds. Previously, only the braincase has been described from these detailed casts. Leptopleuron is reconstructed as a 270-mm-long reptile with a long tail, although it is possible that even the largest known specimens were still sub-adults. Within Procolophonoidea, Leptopleuron is distinguished by the following non-braincase autapomorphies: two flattened, triangular spines of equal size on the quadratojugal; V-shaped groove on the jugal; the anterior tip of the jugal in contact with the posterolateral extension of the nasal; minimal contact between the jugal and the postorbital; frontals narrow anterior to the orbitotemporal openings; the vomerine dentition consisting of a tall and a short pair of fangs; broad medial ridge of pleurocentra of the dorsal vertebrae divided into three separate ridges by two deep grooves on each pleurocentrum; distinct three-fold depression pattern on the ventral side of ischium; and the first phalanx on the fifth pedal digit being long and slim. Leptopleuron shares some features with living sand lizards and might have lived a burrowing lifestyle. The dentition and body shape of Leptopleuron imply it ate a diet of fibrous plant material or hard-shelled invertebrates.
Morphological Diversity and Biogeography of Procolophonids
Cisneros, J. C., and M. Ruta. 2010. Morphological diversity and biogeography of procolophonids (Amniota: Parareptilia). Journal of Systematic Paleontology 8:607-625. DOI: 10.1080/14772019.2010.491986.
Abstract - A recent phylogenetic analysis of procolophonid parareptiles is used as the basis for a study of morphological diversity (disparity) in these amniotes. Disparity values are compared in three groups of procolophonids (a paraphyletic series of basal taxa and two monophyletic sister groups: procolophonines and leptopleuronines), two ecophenotypic assemblages (one based upon inferred diet - non high-fibre versus high-fibre species; the other based upon cranial sculpture - non horned versus horned species), and two temporal assemblages (Lower Triassic versus Middle and Upper Triassic). The mean disparity values are comparable in the case of temporal and ecophenotypic assemblages. High-fibre species are marginally less disparate than non high-fibre species. The combined Middle and Upper Triassic species are slightly less disparate than Lower Triassic species. Finally, horned species are only slightly more disparate than non-horned species. The paraphyletic series of basal taxa and the leptopleuronines show similar disparity values, marginally higher than those for procolophonines. Phylogenetic analysis is also used to reconstruct the biogeographical history of procolophonids. Both ancestral area analysis and dispersal-vicariance analysis show that South Africa was the most likely ancestral area for procolophonids as a whole. North China - either as a single area or in combination with Russia or South Africa - was the most likely ancestral area for the leptopleuronine-procolophonine clade.
Abstract - A recent phylogenetic analysis of procolophonid parareptiles is used as the basis for a study of morphological diversity (disparity) in these amniotes. Disparity values are compared in three groups of procolophonids (a paraphyletic series of basal taxa and two monophyletic sister groups: procolophonines and leptopleuronines), two ecophenotypic assemblages (one based upon inferred diet - non high-fibre versus high-fibre species; the other based upon cranial sculpture - non horned versus horned species), and two temporal assemblages (Lower Triassic versus Middle and Upper Triassic). The mean disparity values are comparable in the case of temporal and ecophenotypic assemblages. High-fibre species are marginally less disparate than non high-fibre species. The combined Middle and Upper Triassic species are slightly less disparate than Lower Triassic species. Finally, horned species are only slightly more disparate than non-horned species. The paraphyletic series of basal taxa and the leptopleuronines show similar disparity values, marginally higher than those for procolophonines. Phylogenetic analysis is also used to reconstruct the biogeographical history of procolophonids. Both ancestral area analysis and dispersal-vicariance analysis show that South Africa was the most likely ancestral area for procolophonids as a whole. North China - either as a single area or in combination with Russia or South Africa - was the most likely ancestral area for the leptopleuronine-procolophonine clade.
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.
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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