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Juvenile Edmontosaurus from Hell Creek Formation of Montana

From: Ben Creisler

A new paper:

Albert Prieto-Márquez (2014)
A juvenile Edmontosaurus from the late Maastrichtian (Cretaceous) of
North America: Implications for ontogeny and phylogenetic inference in
saurolophine dinosaurs.
Cretaceous Research 50: 282-303
DOI: 10.1016/j.cretres.2014.05.003

The anatomy of an articulated juvenile specimen of the saurolophine
hadrosaurid dinosaur Edmontosaurus annectens, LACM 23504, is described
in detail. This individual consists of a partial skull and nearly
complete articulated postcranium, collected from upper Maastrichtian
strata of the Hell Creek Formation of Montana, USA. This study aims to
help understand the ontogenetic morphological changes occurring in the
cranium and postcranium of saurolophine hadrosaurids using E.
annectens as a case study. Emphasis is placed on those morphological
attributes that are ontogenetically variable via comparative osteology
between the juvenile and the available adult specimens. It is observed
that much of the cranial ontogenetic variation relates to the
elongation of the skull and mandible. In the postcranium, most of the
ontogenetic variation concentrates in the pectoral and pelvic girdles
and the stylopodia. Not all the identified patterns of ontogenetic
variation may be generalized to all hadrosaurids. The impact of
ontogenetic variation on phylogenetically informative characters of
saurolophine hadrosaurids is evaluated. It is concluded that, at least
for Edmontosaurus annectens (and perhaps other saurolophine
hadrosaurids), most characters used in phylogenetic inference of these
animals are not affected by ontogeny. Thus, juvenile specimens are
still a source of substantial character data suitable for use in
phylogenetic analyses of saurolophine relationships. Nevertheless, it
is recommended that ontogenetically variable characters are left as
missing data in a character–taxon matrix when only juvenile material
is available for a given saurolophine taxon. Scoring those characters
based solely on juveniles is likely to decrease the accuracy of the
phylogenetic inference.