Go to Naturalis.nl

Search results

Query: keyword: "evolution"

AuthorsE. Ascarrunz, J.-C. Rage, P. Legreneur, M. Laurin
TitleTriadobatrachus massinoti, the earliest known lissamphibian (Vertebrata: Tetrapoda) re-examined by μCT scan, and the evolution of trunk length in batrachians
JournalContributions to Zoology
KeywordsAnura; caudopelvic apparatus; CT scan; Salientia; Triassic; trunk evolution
AbstractTriadobatrachus massinoti is a batrachian known from a single fossil from the Early Triassic of Madagascar that presents a combination of apomorphic salientian and plesiomorphic batrachian characters. Herein we offer a revised description of the specimen based on X-ray micro-tomography data. We report previously unknown caudal vertebrae, possible mentomeckelians, and hidden parts of other structures. We also confirm the presence of a ventrolateral ledge on the opisthotic, and we rectify some previous interpretations. There are no cervical ribs and the jaw may have had an angular. The presacral region is composed of 15 vertebrae with a unique atlas-axis complex instead of 14 vertebrae with a bipartite atlas. The configuration of the pelvic girdle is not very clear, although it is likely more plesiomorphic than the anuran-like condition previously assumed. Our re-assessment of the saltatorial performance of Triadobatrachus supports the traditional interpretation that this animal was not a specialised jumper. In order to assess the sequence of events in the early evolution of the salientian morphotype, we estimated the ancestral length of the trunk region of batrachians under different hypotheses of lissamphibian relationships and divergence times. Most of our results suggest that some trunk reduction took place before the divergence of caudates and salientians (presumably in the Permian), and that the trunk of Triadobatrachus mostly reflects this ancestral condition. Thus, trunk reduction possibly preceded the anteroposterior elongation of the ilia and the shortening of the tail seen in riadobatrachus. We also provide an updated review of the data relevant for the use of Triadobatrachus as a calibration constraint in molecular divergence age analyses that meets recently-suggested standards.
Document typearticle
Download paperspdf document http://www.repository.naturalis.nl/document/637613 
pdf document http://www.repository.naturalis.nl/document/637614 
pdf document http://www.repository.naturalis.nl/document/637615 
pdf document http://www.repository.naturalis.nl/document/637616 
xls document http://www.repository.naturalis.nl/document/637617 
zip document http://www.repository.naturalis.nl/document/637618 
xls document http://www.repository.naturalis.nl/document/637619 
bib document http://www.repository.naturalis.nl/document/637621 
tif document http://www.repository.naturalis.nl/document/637622 
stl document http://www.repository.naturalis.nl/document/639632