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CASSOWARY CRESTS AGAIN
Taking a break from his endless rant on oviraptorosaurs (note use of
the the name oviraptosaurs [sic] in Tom Holtz's _Dinosaur World_
article.. not Tom's fault I'm sure), Jaime Headden wrote...
> Speaking of cassowaries, it has recently come to my attention that
> cassowaries do have a bony core to their casque, though not as
> prominent as the casque itself, and I am unaware that when the
> casque breaks if the bone is unaffected.
We covered this here on a list earlier this year Jaime. But here we
go again anyway. Cassowary casques are true bony crests composed of
vaulted skull bones over which a keratinous casque grows. The keratin
increases the crest's height by anywhere between 30 and 100% in
adults. In this respect, cassowary crests are probably like
oviraptorid ones. Probably unlike oviraptorids, cassowaries use their
crests as tools when foraging in soil and leaf litter. Their crests
are pretty much always lopsided, with the apex tilting to the left I
think - this implies handedness, but I'm speculating here because I
know nothing about handedness in ratites.
Cassowaries must occasionally use their crests in a very dynamic or
vigorous fashion (such behaviours are unobserved) - as foliage
deflectors perhaps - as sometimes they are broken. Some unfortunate
birds have been described where the bony crest, as well as the
keratin extension, was broken - presumably this is painful but the
entire structure did heal and regrow. Some references state that
broken/regrown cassowary crests are common, but I've examined about
100 of the things (all growth stages, all 3 species), and I didn't
see one broken crest.
Like the crests of hornbills and tapejarid pterosaurs, cassowary
crests are very hollow with a moderately spaced network of bracing
trabeculae. Another interesting observation - cassowary lower jaws
have (rostrally) serrated beaks. Obviously we wouldn't know this if
we only had fossil cassowaries.
John Jackson - if you are there, please email me.
"Somebody call a goddam paramedic!!!"