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Camarasaurus pedal pathologies from digging with claws

Ben Creisler

A new advance online paper in open access Acta Palaeontologica Polonica:

Emanuel Tschopp, Oliver Wings, Thomas Frauenfelder, and Bruce M.
Rothschild (2014)
Pathological phalanges in a camarasaurid sauropod dinosaur and
implications on behaviour.
Acta Palaeontologica Polonica (in press)

Several types of pathological bony overgrowth are known from various
dinosaur taxa but, except for stress fractures, are rarely reported
from appendicular elements. Herein we describe pathological manual and
pedal phalanges of a camarasaurid sauropod (SMA 0002), which show
features rarely recognised in non-avian dinosaurs. They include
lateral osteophytes and smoothing of phalangeal articular surfaces, a
deep pit, proximal enthesophytes in pedal unguals, distal overgrowth
associated with a fracture, and a knob-like overgrowth lateral to the
distal condyles of a pedal phalanx. Their causes were assessed by
means of visual examination, CT scans, and bone histology, where
possible. The lateral osteophytes are interpreted as symptoms of
osteoarthritis. The ossified tendon insertions in the unguals are most
probably the result of prolonged, heavy use of the pedal claws,
possibly for scratchdigging. The distal overgrowth is interpreted to
have developed due to changed stress regimes, and to be the cause for
the fracture. The deep pit represents most likely a case of
osteochondrosis, whereas the knob-like overgrowth likely represents a
post-traumatic phenomenon not previously reported in dinosaurs. The
study confirms that a rigorous assessment of pathologies can yield
information about behaviour in long-extinct animals.