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

Astrophocaudia, new titanosauriform sauropod from Early Cretaceous of North America

From: Ben Creisler

A new sauropod in an advance online paper:

Michael D. D’Emic (2012)
Revision of the sauropod dinosaurs of the Lower Cretaceous Trinity
Group, southern USA, with the description of a new genus.
Journal of Systematic Palaeontology (advance online publication)

Early Cretaceous sauropods were among the first dinosaurs discovered
in North America, but several aspects of their taxonomy and evolution
remain poorly understood. Much of this ambiguity stems from lack of
anatomical overlap among taxa and the 125-year-long taxonomic
confusion surrounding the sauropods Astrodon and Pleurocoelus. New
discoveries have begun to remedy the first problem, but a lack of
autapomorphies in their holotypes and skeletal associations among
their hypodigms renders Astrodon johnstoni, Pleurocoelus altus and
Pleurocoelus nanus nomina dubia. Herein I examine the affinities of
sauropods from the Trinity Group of Texas and Oklahoma previously
referred to as ‘Pleurocoelus’ or ‘Astrodon’. Some of this material
currently comprises the genera Paluxysaurus and Sauroposeidon from
laterally equivalent strata in Texas and Oklahoma, respectively.
Although representative individuals of Paluxysaurus are only
two-thirds the size of Sauroposeidon, bone histology of Paluxysaurus
indicates that the individuals from the type locality were not near
adult size. The similar provenance, lack of morphological differences,
and shared unique features support referral of Paluxysaurus to
Sauroposeidon. Other sauropod remains from the Trinity Group are not
referable to ‘Pleurocoelus’, ‘Astrodon’ or Sauroposeidon. Some of
these remains comprise the holotype of Astrophocaudia slaughteri gen.
et sp. nov., a basal titanosauriform diagnosed by a
hyposphene–hypantrum system in the caudal vertebrae. A sauropod hind
limb previously referred to ‘Pleurocoelus’ is instead referable to
Cedarosaurus weiskopfae based on shared features of the pes. Cladistic
analysis indicates that Astrophocaudia and Sauroposeidon are members
of Somphospondyli, whereas Cedarosaurus is a brachiosaurid. The
Trinity Group of Texas and laterally equivalent Antlers Formation of
Oklahoma exhibit similar dinosaur faunas at the generic and specific
levels to the Cloverly Formation of Wyoming. This homogeneity with
respect to latitude stands in marked contrast to the latitudinal
variation in dinosaur communities that developed later in the