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Hadrosaur forearm orientation



From: Ben Creisler
bcreisler@gmail.com


A new online open-access paper:



Phil Senter (2012)
Forearm orientation in Hadrosauridae (Dinosauria: Ornithopoda) and
implications for museum mounts.
Palaeontologica Electronica
Article number: 15.3.30A
http://palaeo-electronica.org/content/2012-issue-3-articles/324-hadrosaurid-forearm


Skeletons of hadrosaurids ("duck-billed dinosaurs") are usually
mounted with palms facing caudally (posteriorly). To achieve this, the
radius is articulated with the medial (ulnar) condyle of the humerus
instead of the lateral (radial) condyle, which would be unique among
vertebrates if it were correct. However, articulated specimens reveal
that in hadrosaurids the radius articulates with the lateral condyle
of the humerus, as in other vertebrates, and the palms face
caudomedially, though more medially than caudally. Active pronation is
prevented by the shapes of the radial and ulnar shafts and by the lack
of rolling articulations between radius and ulna. This makes the
caudomedial orientation of the palm permanent. This finding
contradicts many museum mounts but agrees with trackway evidence.