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Juvenile phytosaur mandibles and other Triassic papers (free pdfs)



From: Ben Creisler
bcreisler@gmail.com


A number of papers about the Triassic from last year that have not
been mentioned on the DML:

Andrew B. Heckert, Hillary S. Jenkins, Spencer G. Lucas and Adrian P.
Hunt (2013)
Mandibles of juvenile phytosaurs (Archosauria:  Crurotarsi) from the
Upper Triassic Chinle Group of Texas and New Mexico, USA.
in Tanner, L.H., Spielmann, J.A. and Lucas, S.G., eds., 2013, The
Triassic System.
New Mexico Museum of Natural History and Science, Bulletin 61 : 228- 236
pdf:
http://www.academia.edu/3665246/Mandibles_of_juvenile_phytosaurs_Archosauria_Crurotarsi_from_the_Upper_Triassic_Chinle_Group_of_Texas_and_New_Mexico_USA


Here we describe five specimens of juvenile phytosaurs from several
localities in the Upper Triassic Chinle Group of Texas and New Mexico.
These include three specimens from localities in the Tecovas Formation
(Texas) of Adamanian age and one each from the Revueltian-age Bull
Canyon Formation and Apachean-age Travesser Formation of New Mexico.
Although all of the specimens are incompletely preserved mandibles,
they are unquestionably phytosaurian based on their elongate mandibles
with an extensive symphyseal region that is of essentially constant
height and has at least some contribution from the splenial. We use
the length (in mm) per preserved tooth socket as a proxy for
ontogenetic stage, ranking the specimens from very young (~4-6
mm/socket) to juvenile (~9 mm/socket). There are distinct differences
in tooth spacing, contribution of the splenial to the symphysis, angle
of tooth eruption, and other features that vary in these specimens
independent of age. This suggests that taxonomic information is
available from the mandible pending further description and
characterization of adult specimens of known taxa.

==

Fabio M. Petti, Massimo Bernardi, Evelyn Kustatscher, Silvio Renesto
and Marco Avanzini (2013)
Diversity of Continental tetrapods and plants in the Triassic of the
Southern Alps: ichnological, paleozoological and palaeobotanical
evidences.
in Tanner, L.H., Spielmann, J.A. and Lucas, S.G., eds., 2013, The
Triassic System.
New Mexico Museum of Natural History and Science, Bulletin 61 : 458-484
pdf:
http://www.researchgate.net/publication/236870132_Diversity_of_Continental_tetrapods_and_plants_in_the_Triassic_of_the_Southern_Alps_ichnological_paleozoological_and_palaeobotanical_evidences

We review the Triassic record of terrestrial plants and animals from
the Southern Alps at more than 60 sites. The Triassic tetrapod track
record seems to mirror the global body fossil record of diapsids (with
the exception of the Olenekian record), but is almost completely
devoid of synapsids and amphibians. During the Bithynian-Pelsonian
interval (early-late Anisian, Middle Triassic) the ichnoassociation
documents a diverse tetrapod fauna composed of lepidosauromorphs,
basal amniotes, archosauriformes (“rauisuchians”) and possible
dinosauromorphs, whereas the body fossil fauna is represented only by
small lepidosauromorphs and archosauriformes (“rauisuchians”). The
rich flora is one of the best examples of early recovery of ecosystems
after the Permo-Triassic event. The Illyrian (late Anisian, Middle
Triassic) ichnoassociation reflects a faunal composition of
lepidosauromorphs, archosauriformes and dinosauromorphs, while the
body fossil assemblage is only represented by a few remains of
archosauromorphs. Tetrapod footprints are missing from the Fassanian
(early Ladinian, Middle Triassic), while scattered skeletal remains
document the presence of large and small archosauromorphs. Fassanian
plant fossils record a flora dominated by conifers and seed ferns. The
Longobardian body fossil record (late Ladinian, Middle Triassic)
documents the presence of archosauromorphs and mammallike-reptiles,
whereas tracks are completely absent. During this period, floras still
show some typical Early-Middle Triassic elements and are dominated by
conifers. The Longobardian fossil record is biased by taphonomic
selection, as these specimens are found only in basinal successions.
Middle and early Late Triassic rich plant fossil associations record
some interesting evolutionary trends, such as the radiation of modern
fern families and the appearance of entire new groups (e.g., the
bennettitaleans).
During the Carnian (Late Triassic) the flora reaches its highest
diversity and shows the first occurrence of unequivocal
bennettitaleans and the first putative cheirolepidiacean conifers.
>From the latest Carnian to the end of the Norian (Late Triassic),
faunal associations are dominated by dinosaurs, while
archosauriformes, drepanosaurids, protorosaurs, pterosaurs,
lepidosauromorphs, “rauisuchians” and dinosauromorphs are only minor
components of the fauna. Norian floras are poorly known but seem to be
dominated by conifers, with rare fragments of Bennettitales.
The numerous tetrapod track associations provide a series of snapshots
trough time that show a huge increase in variability reflecting the
morphological diversity spanning from a stem-amphibian to a
crurotarsan to a dinosaur foot. The nearly-complete absence of
non-diapsid tetrapods appears to be possibly correlated with the
paucity of fluvial-lacustrine environments, while the dominance of
dinosaurs in the Norian has to be understood in the context of a
monotonous, harsh, carbonate-platform environment. The Norian sites
document the presence of a variety of archosaurs, prolacertiforms and
lepidosauromorphs whose diversification may have been the result of
strong evolutionary pressures triggered by the unstable environment.


==

Massimo Bernardi, Fabio Massimo Petti, Simone D'Orazi Porchetti and
Marco Avanzini (2013)
Large tridactyl footprints associated with a diverse ichnofauna from
the Carnian of the Southern Alps.
in Tanner, L.H., Spielmann, J.A. and Lucas, S.G., eds., 2013, The
Triassic System.
New Mexico Museum of Natural History and Science, Bulletin 61 : 48-53
pdf:
http://www.researchgate.net/publication/236785084_Large_tridactyl_footprints_associated_with_a_diverse_ichnofauna_from_the_Carnian_of_the_Southern_Alps


We report the discovery of two large tridactyl footprints from the
late Carnian (Tuvalian) of the Southern Alps (NE Italy). The tracks
can be confidently attributed to a dinosaur trackmaker with an
estimated body length of about 5 meters. These specimens are part of a
diverse ichnofauna testifying to the coexistence of large and small
dinosaurs, dinosauriforms and crurotarsans. The track-bearing layers
are well time-constrained, and provide one of the earliest reliable
evidence of dinosaurs in northern Pangea.