[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

New Cretaceous turtles: Leyvachelys from Colombia + Neurankylus species from Utah

Ben Creisler

New papers about turtles:


Edwin Cadena (2015)
The first South American sandownid turtle from the Lower Cretaceous of Colombia.
PeerJ 3:e1431
doi: https://doi.org/10.7717/peerj.1431

Sandownids are a group of Early Cretaceous-Paleocene turtles that for
several decades have been only known by cranial and very fragmentary
postcranial elements. Here I report and describe the most complete
sandownid turtle known so far, including articulated skull, lower jaw
and postcranial elements, from the Early Cretaceous (upper
Barremian-lower Aptian, >120 Ma), Paja Formation, Villa de Leyva town,
Colombia. The new Colombian sandownid is defined here as Leyvachelys
cipadi new genus, new species and because of its almost identical
skull morphology with a previously reported turtle from the Glen Rose
Formation, Texas, USA, both are grouped in a single and officially
(ICNZ rules) defined taxon. Phylogenetic analysis including L. cipadi
supports once again the monophyly of Sandownidae, as belonging to the
large and recently redefined Pan-Chelonioidea clade. The morphology of
L. cipadi indicates that sandownids were not open marine turtles, but
instead littoral to shallow marine durophagous dwellers. Leyvachelys
cipadi not only constitutes the first record of sandowinds in South
America, but also the earliest global record for the group.


Neurankylus hutchisoni and Neurankylus utahensis

Joshua R. Lively (2015)
Baenid turtles of the Kaiparowits Formation (Upper Cretaceous:
Campanian) of southern Utah, USA.
Journal of  Systematic Palaeontology (advance online publication)

I describe the assemblage of baenid turtles found in the Campanian
Kaiparowits Formation of southern Utah and compare it with baenids
from other basins across Laramidia. Baenids were one of the most
diverse and abundant freshwater turtle clades during the Late
Cretaceous. They were restricted to North America, with all except the
basal-most taxon (Arundelemys) restricted to Laramidia. During the
Campanian, baenids were conspicuous parts of the turtle assemblages of
Alberta, Montana and New Mexico. The baenids of the Kaiparowits
Formation are critical in that they provide an assemblage from
southern Laramidia that is correlative with those from northern
Laramidia, allowing for more accurate testing of Campanian
palaeobiogeographical hypotheses. In this paper, two new baenid
species, Neurankylus hutchisoni sp. nov. and Neurankylus utahensis sp.
nov., are described. Additionally, the first description of cranial
material from Denazinemys nodosa is provided. A comprehensive survey
of collected material indicates that at least six baenid taxa are
present in the formation, including Neurankylus hutchisoni,
Neurankylus utahensis, Thescelus sp., Arvinachelys goldeni,
Denazinemys nodosa and Boremys grandis. Arvinachelys, Neurankylus
hutchisoni and Neurankylus utahensis have not been identified outside
of the Kaiparowits Basin, but Denazinemys nodosa and Boremys grandis
both are known from younger sediments of the San Juan Basin of New
Mexico. Members of the genus Thescelus are known from the Campanian of
New Mexico and the Maastrichtian of Wyoming, Montana and Saskatchewan,
but are conspicuously absent in the Campanian of Alberta and Montana.
The baenid assemblage in the Kaiparowits Formation provides support
for both basin-scale endemism and north–south provincialism across
Laramidia during the Campanian. There is also evidence for a
latitudinal gradient in diversity, as only three baenid species have
been reported from the temporally correlated Dinosaur Park Formation
in Alberta.