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Re: Caudipteryx suffered from osteoarthritis
>From Ben Creisler
Here are a few passages from the Discussion section of the article:
Our study shows that Early Cretaceous birds from the Liaoning fauna in China
(with the exception of Caudipteryx) seldom manifest osteoarthritis (Table 1).
The rarity of osteoarthritis in Early Cretaceous birds mirrors that in
Cretaceous dinosaurs. The frequency in the oviraptosaur Caudipteryx is
signiﬁcantly greater. In modern birds, osteoarthritis shows a species speciﬁc
variability in prevalence (Rothschild and Panza, 2005, 2006). There is also an
inverse relationship to body mass in recent birds (Rothschild and Panza, 2008).
In contrast, the Mesozoic sample shows a positive correlation with body size
(Table 1) with the highest incident in the comparatively large Caudipteryx.
Caudipteryx is classiﬁed as an oviraptorsaur (Lü et al., 2002), but were
oviraptorsaurs feathered dinosaurs or birds (Dyke and Norell, 2005; Hwang et
The next largest form, Microraptor, with its feathered feet, is unlikely to
have been a ground bird (Alexander et al., 2010). It is not surprising that it
avoided osteoarthritis (less than 1%). Landing on tree trunks apparently did
not overstress its ankle joint, and an inherent sprawling posture distributed
the stresses, in spite of the geocentric nature of the ankle. A geocentric
joint rotates as well as ﬂexes and extends and is subject to greater stresses
than a hinge joint.
Why then isn’t Caudipteryx as well protected from osteoarthritis as are the
modern ratites that it resembles? Its reduced wing parallels that seen in
ﬂightless birds and suggests that Caudipteryx also had a ﬂighted ancestor, at
least as capable as the gliding dromaeosaur Microraptor (Alexander et al.,
2010). This means that the adaptation for terrestrial locomotion seen in
Caudipteryx developed de novo in that genus and may not have been perfected to
a point that prevented development of osteoarthritis. We have not yet had an
rs including forms that are more cursorially adapted, but such a study might
help illuminate the reasons for osteoarthritis in these animals.