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Meet baby Parasaurolophus "Joe" (free pdf + web info)

From: Ben Creisler

Lots of material out about a baby Parasaurolophus specimen:

Andrew A. Farke, Derek J. Chok, Annisa Herrero, Brandon Scolieri &
Sarah Werning (2013)
Ontogeny in the tube-crested dinosaur Parasaurolophus (Hadrosauridae)
and heterochrony in hadrosaurids.
PeerJ 1:e182
doi: http://dx.doi.org/10.7717/peerj.182

The tube-crested hadrosaurid dinosaur Parasaurolophus is remarkable
for its unusual cranial ornamentation, but little is known about its
growth and development, particularly relative to well-documented
ontogenetic series for lambeosaurin hadrosaurids (such as
Corythosaurus, Lambeosaurus, and Hypacrosaurus). The skull and
skeleton of a juvenile Parasaurolophus from the late Campanian-aged
(∼75.5 Ma) Kaiparowits Formation of southern Utah, USA, represents the
smallest and most complete specimen yet described for this taxon. The
individual was approximately 2.5 m in body length (∼25% maximum adult
body length) at death, with a skull measuring 246 mm long and a femur
329 mm long. A histological section of the tibia shows
well-vascularized, woven and parallel-fibered primary cortical bone
typical of juvenile ornithopods. The histological section revealed no
lines of arrested growth or annuli, suggesting the animal may have
still been in its first year at the time of death. Impressions of the
upper rhamphotheca are preserved in association with the skull,
showing that the soft tissue component for the beak extended for some
distance beyond the limits of the oral margin of the premaxilla. In
marked contrast with the lengthy tube-like crest in adult
Parasaurolophus, the crest of the juvenile specimen is low and
hemicircular in profile, with an open premaxilla-nasal fontanelle.
Unlike juvenile lambeosaurins, the nasal passages occupy nearly the
entirety of the crest in juvenile Parasaurolophus. Furthermore,
Parasaurolophus initiated development of the crest at less than 25%
maximum skull size, contrasting with 50% of maximum skull size in
hadrosaurs such as Corythosaurus. This early development may
correspond with the larger and more derived form of the crest in
Parasaurolophus, as well as the close relationship between the crest
and the respiratory system. In general, ornithischian dinosaurs formed
bony cranial ornamentation at a relatively younger age and smaller
size than seen in extant birds. This may reflect, at least in part,
that ornithischians probably reached sexual maturity prior to somatic
maturity, whereas birds become reproductively mature after reaching
adult size.

Website for dinosaur "Joe":




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