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Bone-eating (was RE: T.rex was a "chicken")




Jaime Headden wrote:


> We assume that carnivores are in fact biting herbivores;
> this is a given. Bite marks on other bones show this to be
> the case (as in *Sinraptor* agonistic behavior, a
> *Triceratops* ilium and sacrum with tooth gouges and holes,
> etc. What we do not assume here is the particularly
> intentional habit of taking whole, defleshed bone and
> processing it orally for the purpose of doing so, which is
> done by some animals like hyenas and vultures, and some
> jackals at least. These animals have oral anatomy or
> behaviors that are specialized to processing the bone or by
> processing what it within them (like marrow). Hyenas are
> marrow-eaters, but they aren't particularly delicate about
> it, and simply crack the bones in their jaws and swallow
> portions thereof. Few animals are primarily or even obligate
> osteophages, including deep-sea carcass scavengers like
> hagfish. When it does occur, it is ordinarily a nutritional
> issue, and most bone-processing occurs to aquire marrow, not
> bone.


Yep, it helps to remember that there are many different behaviors that can lead 
to getting access to bone marrow.  Among extant mammals, specialized osteophagy 
is apparently quite rare.  Hyenas (Hyaenidae) and the Tasmanian devil 
(_Sarcophilus harrisii_) both have the ability to crack open bones with their 
jaws, and this behavior requires not only strong dentition, but the ability to 
resist high stresses at the point of contact between the jaws and the bone.  
(See: Wroe et al., 2005; Proc. R. Soc. B 272: 619-625).


As for vultures, I know that the lammergeier (_Gypaetus barbatus_) will crack 
open bones by dropping them from a great height on to rocks.  Their own jaws 
and feet aren't nearly strong enough to crack open large bones.  I don't know 
how common specialized osteophagy is among vultures (Old and New World).  The 
jaws and feet of many vulture species are even too weak to breach the hides of 
carcasses; so they either have to wait for a stronger predator to rip into the 
carcass, or plunge their head deep into an existing orifice.  Any orifice will 
do.  Yes, epecially THAT one.  It allows read access to the viscera.


I wouldn't have called hagfish osteophagous (at least not specialized), given 
that their mouthparts are adapted to feeding upon soft tissue.  Hagfishes 
(Myxini) have been known to enter the bodies of dead or incapacitated 
vertebrates and devour them from the inside out, either by making use of 
existing openings (including orifices, in a vulture-like fashion), or by making 
their own openings.


And since we're sliding down the animal scale, there is a genus of deep-sea 
worm called _Osedax_ (also known as a 'zombie worm') that specializes in boring 
into the bones of whale carcasses.  As with specialist bone-eating vertebrates, 
the aim is to get at the yummy stuff inside the bone.



Cheers

Tim