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Early Evolution of Rhynchosaurs (free pdf)



Ben Creisler
bcreisler@gmail.com

A new paper in open access:

Martín D. Ezcurra, Felipe Montefeltro  and Richard J. Butler (2016)
The Early Evolution of Rhynchosaurs.
Frontiers in Ecology and Evolution 3:142  (23 pgs)
doi: 10.3389/fevo.2015.00142
http://dx.doi.org/10.3389/fevo.2015.00142
http://journal.frontiersin.org/article/10.3389/fevo.2015.00142/full



The rhynchosaurian archosauromorphs are an important and diverse group
of fossil tetrapods that first appeared during the Early Triassic and
probably became extinct during the early Late Triassic (early Norian).
Here, the early evolution of rhynchosaurs during the Early and early
Middle Triassic (Induan-Anisian: 252.2-242 Mya) is reviewed based on
new anatomical observations and their implications for the taxonomy,
phylogenetic relationships and macroevolutionary history of the group.
A quantitative phylogenetic analysis recovered a paraphyletic genus
Rhynchosaurus, with “Rhynchosaurus” brodiei more closely related to
hyperodapedontines than to Rhynchosaurus articeps. Therefore, a new
genus is erected, resulting in the new combination Langeronyx brodiei.
A body size analysis found two independent increases in size in the
evolutionary history of rhynchosaurs, one among stenaulorhynchines and
the other in the hyperodapedontine lineage. Maximum likelihood fitting
of phenotypic evolution models to body size data found ambiguous
results, with body size evolution potentially interpreted as fitting
either a non-directional Brownian motion model or a stasis model. A
Dispersal-Extinction-Cladogenesis analysis reconstructed the areas
that are now South Africa and Europe as the ancestral areas of
Rhynchosauria and Rhynchosauridae, respectively. The reconstruction of
dispersal events between geographic areas that are broadly separated
paleolatitudinally implies that barriers to the dispersal of
rhynchosaurs from either side of the paleo-Equator during the Middle
Triassic were either absent or permeable.