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Eucnemesaurus entaxonis, new species of Late Triassic sauropodomorph



Ben Creisler
bcreisler@gmail.com


A new online paper:

Blair W. McPhee, Jonah N. Choiniere, Adam M. Yates & Pia A. Viglietti (2015)
A second species of Eucnemesaurus Van Hoepen, 1920 (Dinosauria,
Sauropodomorpha): new information on the diversity and evolution of
the sauropodomorph fauna of South Africa's lower Elliot Formation
(latest Triassic).
Journal of Vertebrate Paleontology (advance online publication)
DOI:10.1080/02724634.2015.980504
http://www.tandfonline.com/doi/full/10.1080/02724634.2015.980504#abstract



The Late Triassic–Early Jurassic Elliot Formation of South Africa is
one of the most important geological formations worldwide for
understanding the early evolution of sauropodomorph dinosaurs.
However, many of the taxa currently recognized as valid within its
lower strata remain either poorly understood, vaguely diagnosed, or
both. The recent discovery of an articulated partial skeleton of a
single individual of the enigmatic lower Elliot genus Eucnemesaurus
provides an important opportunity to expand our understanding of the
anatomy and phylogeny of this poorly known taxon. A comprehensive
investigation of the morphological relationships of this new specimen
identified key features, pertaining primarily to the femoral shaft and
distal tibia, which distinguish it from the only other previously
named species of Eucnemesaurus—E. fortis. A new species, E. entaxonis,
is erected within which to accommodate it. A cladistic analysis
confirms the monophyly of Eucnemesaurus, as well as its continued
inclusion within the low-diversity ‘Riojasauridae.’ Nonetheless, this
result highlights continued uncertainties regarding the constituency
of the Riojasaurus hypodigm. The relatively robust pedal architecture
of E. entaxonis suggests an unexpectedly early experiment in a slower,
subgraviportal form of locomotion within Late Triassic basal
Massopoda, whereas the intriguing mosaic of plesiomorphic and derived
characters evident in E. entaxonis raises questions regarding the
hypothesized population dynamics of the basal-most sauropodomorph taxa
of the lower Elliot Formation. This latter concern has particular
bearing on newly observed inconsistencies in the prevailing hypodigms
of other lower Elliot basal sauropodomorph taxa such as
Melanorosaurus.

http://zoobank.org/urn:lsid:zoobank.org:pub:68A7F233-2424-469E-A008-442C4E04B02F