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New abelisaurid remains (Theropoda) from Late Cretaceous of Brazil



Ben Creisler
bcreisler@gmail.com

A new paper:

Arthur Souza Brum, Elaine Batista Machado, Diogenes de Almeida Campos
& Alexander Wilhelm Armin Kellner (2016)
Morphology and internal structure of two new abelisaurid remains
(Theropoda, Dinosauria) from the Adamantina Formation (Turonian –
Maastrichtian), Bauru Group, Paraná Basin, Brazil.
Cretaceous Research 60: 287-296
doi:10.1016/j.cretres.2015.11.013
http://www.sciencedirect.com/science/article/pii/S019566711530121X


Highlights

Two rare theropod bones from Adamantina Formation are described and CT-scanned.
They can be identified as an ilium and a femur referable to the Abelisauridae.
The ilium reveals pneumatization, first time reported to this group.
The femur reveals an anisotropic trabecular system, suggesting muscle
strain trends.

Abstract

The knowledge on the Brazilian theropod fauna is hampered by the
limited number of specimens unearthed so far. The most potential
deposits for the finding of those dinosaurs are the layers of Bauru
Group, which comprises several different formations of Late Cretaceous
age. Most of those remains are referred to Abelisauroidea, a clade
that is particularly well represented in Gondwana. Here we report two
new abelisaurid specimens comprising a left ilium (DGM 927-R) and the
distal articulation of a right femur (MCT 1857-R) unearthed from the
outcrops of Adamantina Formation (Turonian – Maastrichtian) in the
locality known as Santo Anastácio, that comprises an abandoned quarry
located in the outskirts of the homonymous city in São Paulo State.
The ilium has a preacetabular process horizontally oriented and
ventrally deflected, as well as an acute angle between this process
and the pubic peduncle. The femur shows a well-developed anteromedial
crest, but not to the same degree as in noasaurids, and ossified
ridges between condyles and tibiofibular crest. Those features allow
us to assign both specimens to Abelisauridae. CT-scans of those
specimens shows that the ilium has pneumaticities similar to the
camellate pattern previously recorded in neosauropods and reveals the
diverticula invasion of abdominal air-sacs. The femur presents a
developed anisotropic trabecular system, which suggests that the main
muscular strain is located at the distal portion of this bone. These
features have not been previously reported in Abelisauridae,
indicating that the internal organization of the postcranial skeleton
in the group is rather complex and quite variable.