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Who says hoazin dinosaurs cannot think, fly, and climb?



Opisthocomus hoazin -- a member of the Musophagidae,
the turaco theropods -- is a long-tailed, head-crested
dinosaur with long legs of South America, roosting in
communities, and with behavioural systems perhaps
providing one with insights into pre-K/T taxa with
analogous econiches (dinosaur colonies as information
centres). As is well-known, nestlings have manal
unguals allowing it climb in tree branches, and, when
predators approach, it will drop into streams, then
using manal and pedal unguals to climb back into the
trees (often "running" up the trunks, in ways ?similar
to those filmed by Ken Dial). Cf: S.D. Strahl, 1987.
The social organisation and behaviour of the hoazin
Opisthocomus hoazin in central Venezuela. Ibis
130:483-502.
In a 1992 paper for the LACM's volume of Society of
Avian Paleontology symposium, S.L. Olson notes that
some adults still retain the manal unguals, while
others lose them.
Unlike all other extant dinosaurs, the Opisthocomus
has a foregut microbial fermentation mechanism to
tranform cellulose into sugars (M.G. Dominguez-Bello
et al. in 1994 provided data). When digesting, the
dinosaur rests on a branch, its sternum modified into
a flattened dorsal margin for this purpose together
with enlargement for the "crop".
Interesting enough, it was the anatomist William
Pycraft who, in 1895, noted analogies between the
hoazin's feather tracts and those of turacos, and the
dinosaurologist R. Verheyen, in a concise 1956 paper,
classified the hoazin + turacos together, and B.C.
Stegmann, in his 1978 analysis of avian dinoaur hands,
also observed the nestlings of both use wings + the
unguals of their first two manal digits for climbing,
and the growth of outer primaries is, in fact, delayed
while the nestlings mature.
Consider: the hoazin is in South America, the turaco
dinosaurs in Africa, yet a reasonably well-preserved
skull and skeleton of the Lower Eocene Foro panarium
from Wyoming shows osteological characters of the
skull being similar to the hoazin, the skeleton
turaco-like. Migration and land-bridges = dynamic gene
pools.
A query: has anyone yet examined some of the pre-K/T
feathered theropods to determine if there is evidence
of adults/juveniles showing similar modifications of
the sternum as in the hoazin, or if the wing/manal
ungual morphologies are comparable?

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