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Aetosauria clade review and other new Triassic archosaur papers

From: Ben Creisler

A number of recent papers about Triassic archosaurs not yet mentioned
on the DML:

Julia B. Desojo, Andrew B. Heckert, Jeffrey W. Martz, William G.
Parker, Rainer R. Schoch, Bryan J. Small, and Tomasz Sulej (2013)
Aetosauria: a clade of armoured pseudosuchians from the Upper Triassic
continental beds.
Geological Society Special Publication 379: Anatomy, Phylogeny and
Palaeobiology of Early Archosaurs and their Kin (advance online

Aetosauria is a clade of obligately quadrupedal, heavily armoured
pseudosuchians known from Upper Triassic (late Carnian–Rhaetian)
strata on every modern continent except Australia and Antarctica. As
many as 22 genera and 26 species ranging from 1 to 6 m in length, and
with a body mass ranging from less than 10 to more than 500 kg, are
known. Aetosauroides scagliai was recently recovered as the most basal
aetosaur, placed outside of Stagonolepididae (the last common ancestor
of Desmatosuchus and Aetosaurus). Interrelationships among the basal
aetosaurs are not well understood but two clades with relatively
apomorphic armour – the spinose Desmatosuchinae and the generally
wide-bodied Typothoracisinae – are consistently recognized. Paramedian
and lateral osteoderms are often distinctive at the generic level but
variation within the carapace is not well understood in many taxa,
warranting caution in assigning isolated osteoderms to specific taxa.
The aetosaur skull and dentition varies across taxa, and there is
increasing evidence that at least some aetosaurs relied on
invertebrates and/or small vertebrates as a food source. Histological
evidence indicates that, after an initial period of rapid growth,
lines of arrested growth (LAGs) are common and later growth was
relatively slow. The common and widespread Late Triassic ichnogenus
Brachychirotherium probably represents the track of an aetosaur.


Alexandre Liparini and Cesar L. Schultz (2013)
A reconstruction of the thigh musculature of the extinct pseudosuchian
Prestosuchus chiniquensis from the Dinodontosaurus Assemblage Zone
(Middle Triassic Epoch), Santa Maria 1 Sequence, southern Brazil
Geological Society Special Publication 379 :Anatomy, Phylogeny and
Palaeobiology of Early Archosaurs and their Kin (advance online

Prestosuchus chiniquensis is an extinct species of terrestrial
archosaur from the Middle Triassic Epoch restricted to southern
Brazil. In this paper the thigh musculature of P. chiniquensis is
reconstructed based on a well-preserved specimen and on myological
descriptions of extant birds and crocodylians. Among the 16 analysed
muscular groups, 13 were recognized as present and homologous to both
extant groups of archosaurs, and two only to the crocodylian line of
archosaurs, so that 15 muscular groups were reconstructed in the
fossil specimen. Morphological particularities of the pelvic girdle
and the hindlimbs of P. chiniquensis gave a distinct arrangement for
the muscular origin and insertion sites, leading to different lines of
action and functions when compared with extant archosaurs. The
comparison between extinct and extant archosaurs showed a basal
condition sustained in some aspects, such as the morphology of the
femur and the flexion of the knee, although other aspects were
considered as derived, such as the morphology of the pubis and
ischium, and their associated muscle origin locations.


Tiago Raugust, Marcel Lacerda, and Cesar Leandro Schultz (2013)
The first occurrence of Chanaresuchus bonapartei Romer 1971
(archosauriformes, proterochampsia) of the Middle Triassic of Brazil
from the Santacruzodon Assemblage Zone, Santa Maria Formation (Paraná
Geological Society Special Publication 379: Anatomy, Phylogeny and
Palaeobiology of Early Archosaurs and their Kin (advance online

Proterochampsians are basal archosauriforms whose record is restricted
to the Middle and Upper Triassic in Argentina and Brazil. They are
quadruped forms that present characteristics consistent with a
semi-aquatic lifestyle, such as an anteroposteriorly elongated skull
that is flattened dorsoventrally with dorsally located orbits. In
2003, specimen UFRGS-PV-0877-T was discovered at the Schoenstadt site,
in the city of Santa Cruz do Sul (Santacruzodon Assemblage Zone, Santa
Maria Formation). This specimen, consisting of disarticulated cranial
elements (such as nasals, frontals, parietals, postorbitals, a left
squamosal, a left pterygoid and a fragment of a right mandibular ramus
that bears teeth) and postcranial elements (such as femora, the left
tibia, one vertebral centrum and two rib fragments), is assigned to
the ‘proterochampsian’ Chanaresuchus bonapartei Romer (1971). This
assignment is based on the shared V-shaped frontal-parietal suture of
the new specimen and Chanaresuchus bonapartei, which differs from the
transversely aligned and zigzagged pattern of C. ischigualastensis.