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Pantydraco anatomy described (free pdf)



From: Ben Creisler
bh480@scn.org

This paper has been out for at least a week but has not been mentioned on
the DML that I recall. The pdf is free at:

http://www.ville-ge.ch/mhng/paleo/paleo-pdf/29-2/pal_29_2_04.pdf

Galton, Peter & Kermack, Diane, 2010.
The anatomy of Pantydraco caducus, a very basal sauropodomorph dinosaur 
from the Rhaetian (Upper Triassic) of South Wales, UK.
Revue de Paléobiologie 29 (2) : 341--404 (décembre 2010) 

Abstract
Apart from characters of the dentary (proportional shortness, also 
Saturnalia tupiniquim) and vertebrae of proximal third of tail (posterior
position of antero-posteriorly short neural spine on arch, absence of
ventral furrowing on centra  ; both also Efraasia minor), the bones of very
basal sauropodomorphs from the Rhaetian (Upper Triassic) fssure fll in
Clifton near Bristol (including holotypes of Thecodontosaurus antiquus,
Asylosaurus yalensis  ; taxon with robust humerus) share no diagnostic
characters with those of Pantydraco caducus from the rhaetian of South
Wales. this taxon is diagnosed by four autapomorphies  : median fusion of
the nasals, prominent medial tubercle from posterior part of surangular,
epipophyses of cervical vertebrae 3-5 form fat plates that overhang  the
posterior margins of the postzygapophyseal facets but do not form raised
ridges on the dorsal surface of the postzygapophysis, and the fossae,
possibly pneumatic, prominent on the neurocentral suture of cervical
vertebrae 6-8 and shallow on the lateral part of centrum 9. the dentary is
deep and short, with maximum height of more than 20 % of length (also
Saturnalia tupiniquim, Thecodontosaurus antiquus), occupying less than 40 %
of total mandibular length (also Saturnalia tupiniquim). the ilium is tall
with a long anterior process (also 
Anchisaurus polyzelus) and a short postacetabular process with the
plesiomorphic absence of a brevis shelf. other plesiomorphic characters
include the lack of a buccal emargination on the dentary (also Saturnalia
tupiniquim)  ; teeth all recurved in lateral view  ; neck short with
mid-cervical centra less than three times as long as wide (also Riojasaurus
incertus, ?Gyposaurus? sinensis)  ; and humerus with a uniquely small
tubercle medial to head and an antero-posteriorly low (also Asylosaurus
yalensis) asymmetrical deltopectoral crest with the apex at 40 % of humeral
length. At least three different sized individuals are preserved and the
new skeletal reconstruction, with the posterior region scaled up to match
the larger holotype, indicates a more bipedal animal than the more
quadrupedal pose based on the incorrect premise that the two main blocks
represent one individual. the specimens represent juveniles as indicated by
the proportionally large skull with large orbits and short, high snout,
slender postorbital bone, separation of most of bones of braincase, large
metotic fssure and fenestra ovalis, low maxillary and dentary tooth counts,
open neurocentral sutures of cervical vertebrae, and incomplete ossifcation
of distal ends of  the  femur and metatarsals. The diversity of basal 
auropodomorphs  from  the Rhaetian of Wales and England adjacent to the
Severn Estuary is high with fve taxa (Pantydraco caducus, three from
clifton, large basal sauropod Camelotia borealis from Somerset).


Keywords
Upper triassic, UK, Dinosauria, Sauropodomorpha, Pantydraco,
Thecodontosaurus, Asylosaurus, Anatomy, taxonomy.

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