A new titanosaur specimen with highly derived skull from the Santonian of northern Patagonia, Argentina
Publicado por Leonardo Filippi en 12:35
Filippi, L., Juárez Valieri, R., Gallina, P., Méndez, A., Gianechini, F. y Garrido, A.
Paleontological fieldworks carried out
on upper section of the Bajo de la Carpa Formation (Santonian, Upper Cretaceous)
at La Invernada area, near Rincón de los
Sauces city (northeast Neuquén Province), result in the discovery of several
specimens of derived titanosaurs, belonging to multiple
taxa. One of them, consists of an articulated modest-sized
individual with a nearly complete skull, the axial sequence from the atlas to
the last sacral vertebrae with their respective ribs, and both ilia.This
sequence is composed by thirteen cervical, ten dorsal and six sacral vertebrae.
The skull displays a spatulate snout morphology, with a straight anterior
margin, similar to the morphology previously recognized in other titanosaurs
such as Antarctosaurus, Bonitasaura and Brasilotitan. The neurocranial morphology is highly derived
compared with other titanosaur taxa with well-known skulls such as Sarmientosaurus, Nemegtosaurus, Tapuiasaurus
and Rapetosaurus, with displaced
frontals located behind the orbits, resulting in an opposite position to the
anterior margin of the snout. The occipital condyle is not preserved, but the
location of the neurocranial elements and the atlas-axis complex (found in anatomical
position) allow to infer a nearly perpendicular position for the tooth row
respect to the cervical sequence. This particular condition, confirmed for
first time in a derived titanosaur, is morphologically convergent with derived
rebbachisaurids such as Nigersaurus.
Besides, their respective biochrons are in agreement with the paleoecological
niche replacement of the rebbachisaurids by the spatulate snouted titanosaurs
in South America, as previously suggested in the post Turonian faunal turnover.
11º Congreso de la Asociación Argentina de Paleontología, Gral. Roca, Río Negro, Argentina 2016.
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