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Andesaurus redescribed

From: Ben Creisler

A new advance online paper in the Zoological Journal of the Linnean Society:

Anatomy of the basal titanosaur (Dinosauria, Sauropoda) Andesaurus delgadoi
from the mid-Cretaceous (Albian?early Cenomanian) Río Limay Formation,
Neuquén Province, Argentina: implications for titanosaur systematics.
Zoological Journal of the Linnean Society
Early View (Articles online in advance of print)
DOI: 10.1111/j.1096-3642.2011.00699.x

Titanosauria is a taxonomically and morphologically diverse clade of
sauropod dinosaurs that appeared in the Middle Jurassic and radiated in the
mid?Late Cretaceous; however, its intrarelationships are poorly understood.
The mid-Cretaceous Argentinean sauropod Andesaurus delgadoi has repeatedly
been recovered at the base of Titanosauria, and thus represents a crucial
taxon for determining the evolutionary history of this clade; yet it has
only received a brief description. Here, we re-describe the holotype,
comprising dorsal, sacral, and caudal vertebrae, as well as limb and pelvic
elements. Detailed comparisons are made with a global array of
titanosauriforms. Andesaurus is a valid genus and can be diagnosed by five
autapomorphies: (1) posterior dorsal neural spine height greater than twice
centrum height (autapomorphic within Macronaria); (2) square-shaped
anterior?middle caudal centra in lateral view; (3) anteroposteriorly
elongate fossa present on the anterodorsal corner of the lateral surface of
middle?posterior caudal centra; (4) ridge along the midshaft of the ventral
surface of metacarpal I, close to the ventromedial margin; (5) prominent
ventromedial ridge along the distal half of metacarpal V. Other remains
previously attributed to Andesaurus cannot be referred to this genus.
Sixteen putative titanosaur synapomorphies can be recognized in Andesaurus,
including: (1) lateral pneumatic foramina in dorsal vertebrae situated
within fossae; (2) anterior?middle caudal vertebrae with ventrolateral
ridges either side of a ventral midline hollow; and (3) lateral bowing of
metacarpal I. This revision provides an important foundation for future
phylogenetic analyses of titanosaurs, and adds to our growing understanding
of this enigmatic clade. Lastly, we recommend the disuse of the coordinated
suprageneric rank taxa of Andesaurus (Andesaurinae, Andesauridae, and
Andesauroidea), at least until titanosaur intrarelationships are better

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