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Aetobarbakinoides, new aetosaur from Brazil



From: Ben Creisler
bcreisler@gmail.com


A new paper in Zootaxa, already mentioned on some blogs today:

Desojo, J. B., Ezcurra, M. D., and Kischlat, E. E.  (2012)
A new aetosaur genus (Archosauria: Pseudosuchia) from the early Late
Triassic of southern Brazil.
Zootaxa 3166:1-33.
Preview of first page:
http://www.mapress.com/zootaxa/2012/f/z03166p033f.pdf



Abstract -
We describe the new aetosaur Aetobarbakinoides brasiliensis gen. et
sp. nov. from the early Late Triassic (late Carnian early Norian)
Brazilian Santa Maria Formation. The holotype is composed of a partial
postcranium including several cervical and dorsal vertebrae and ribs,
one anterior caudal vertebra, right scapula, right humerus, right
tibia, partial right pes, and anterior and mid-dorsal paramedian
osteoderms. Aetobarbakinoides is differentiated from other aetosaurs
by the presence of cervical vertebrae with widely laterally extended
prezygapophyses, mid-cervical vertebrae with anterior articular facet
width more than 1.2 times wider than the posterior one, anterior
caudal vertebrae with extremely anteroposteriorly short
prezygapophyses, elongated humerus and tibia in relation to the axial
skeleton, and paramedian osteoderms with a weakly raised anterior bar.
A cladistic analysis recovered the new species as more derived than
the South American genera Aetosauroides (late Carnian-early Norian)
and Neoaetosauroides (late Norian-Rhaetian), and it is nested as the
sister-taxon of an unnamed clade, composed of Typothoracisinae and
Desmatosuchinae, due to the absence of a ventral keel in the cervical
vertebrae. Aetobarbakinoides presents a skeletal anatomy previously
unknown among South American aetosaurs, with the combination of
presacral vertebrae with hyposphene, anteroposteriorly short and
unkeeled cervical vertebrae, gracile limbs, and paramedian osteoderms
with a weakly raised anterior bar. Aetobarbakinoides is among the
oldest known aetosaurs together with Aetosauroides from Argentina and
Brazil and Stagonolepis robertsoni from Scotland, indicating
Aetobarbakinoides, which is one of the oldest known aetosaurs, is in
agreement with an older origin for the group, as it is expected by the
extensive ghost lineages at the base of the main pseudosuchian clades.