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Pappochelys, new stem-turtle from the Middle Triassic of Germany + Gaffneylania, new horned turtle from Argentina

Ben Creisler

New papers that may be of interest:

Rainer R. Schoch & Hans-Dieter Sues (2015)
A Middle Triassic stem-turtle and the evolution of the turtle body plan.
Nature  (advance online publication)

The origin and early evolution of turtles have long been major
contentious issues in vertebrate zoology. This is due to conflicting
character evidence from molecules and morphology and a lack of
transitional fossils from the critical time interval. The
~220-million-year-old stem-turtle Odontochelys from China has a partly
formed shell and many turtle-like features in its postcranial
skeleton. Unlike the 214-million-year-old Proganochelys from Germany
and Thailand, it retains marginal teeth and lacks a carapace.
Odontochelys is separated by a large temporal gap from the
~260-million-year-old Eunotosaurus from South Africa, which has been
hypothesized as the earliest stem-turtle. Here we report a new
reptile, Pappochelys, that is structurally and chronologically
intermediate between Eunotosaurus and Odontochelys and dates from the
Middle Triassic period (~240 million years ago). The three taxa share
anteroposteriorly broad trunk ribs that are T-shaped in cross-section
and bear sculpturing, elongate dorsal vertebrae, and modified limb
girdles. Pappochelys closely resembles Odontochelys in various
features of the limb girdles. Unlike Odontochelys, it has a cuirass of
robust paired gastralia in place of a plastron. Pappochelys provides
new evidence that the plastron partly formed through serial fusion of
gastralia. Its skull has small upper and ventrally open lower temporal
fenestrae, supporting the hypothesis of diapsid affinities of turtles.



In German:




Juliana Sterli, Marcelo S. de la Fuente and J. Marcelo Krause (2015)
A new turtle from the Palaeogene of Patagonia (Argentina) sheds new
light on the diversity and evolution of the bizarre clade of horned
turtles (Meiolaniidae, Testudinata).
Zoological Journal of the Linnean Society 174(3): 519–548
DOI: 10.1111/zoj.12252

In this contribution we present a new species of horned turtle,
Gaffneylania auricularis gen. et sp. nov., from the Paleogene of
Patagonia. The specimens come from the lower section of the Sarmiento
Formation (Middle Eocene) at Cerro Verde (Cañadón Hondo area, Province
of Chubut, Argentina). The level containing turtles and
crocodyliforrmes is located at the base of the section and it consists
of laminated, fine tuffs interpreted as shallow pond sediments. It
underlies another fossiliferous level comprising lenticular, massive
sandstones bearing skeletal remains of mammals, referred by previous
authors to the Casamayoran SALMA. Gaffneylania auricularis represents
one of the most complete meiolaniids from South America found to date
and it is distinguished from other meiolaniids by the presence of a
peculiar half-moon-shaped, thick rim surrounding the cavum tympani,
the presence of three cranial scutes K and an unenclosed canalis
chorda tympani mandibularis, among others. This new species sheds new
light on the evolution and palaeobiogeographical history of the clade
Meiolaniidae in Australasia and South America during the Cainozoic.
The break up of southern Gondwana provoked major global climatic
changes during the Cainozoic that probably influenced the evolution of
meiolaniid turtles. The co-evolution of meiolaniids with other
amniotes (e.g. chelid turtles, mammals) suggests a common
palaeobiogeographical history of those clades in southern Gondwana.