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Re: *Fruitafossor*

David Marjanovic (david.marjanovic@gmx.at) wrote:

<As for myrmecophagy being unknown in K mammals... I'm not so sure. The 
Zalambdalestidae have the postcanines of an insectivore -- but what are those
ever-growing near-horizonal lower incisors doing in the same jaw? It's clear
that those animals were terrestrial hoppers, not tree-climbers like an aye-aye,
which likewise has gnawing incisors but postcanines suitable for insectivory.
Perhaps they gnawed holes into termite mounds???>

  I have a big reply to David to get to but for now, secondary comments. The
postcrania of *Zalambdalestes* at least is not consistent with a bounder, and
the large complex postcanines of the skull are more consistent with general
insectivory and microcarnivory (eating small vertebrates) than for eating
termites, which are largely processed by crushing into the palate or simple
swallowing and gut digestion, thus myrmecophages have typically smaller, weak
teeth, or none at all. This is true for tachyglossids, myrmecophagids, the
"simpler-toothed" dasypodids, and pholidotes. Myrmecophagous primates tend not
to be specialists in just mound-building insects, but in burrowers, and do not
dig into the homes of these insects to get at them. They also chew, so teeth
remain complex, and their diet is more general.

  On the other hand, the teeth of general insectivores are complex and retain
blade-like and piercing premolars, complex molars, large canines, and
incisiform to conodont precanine dentition, as in most insectivorans _sensu
lato_ (some of which have WHOPPING huge bladed premolars), and so forth.
Animals that use their teeth to process earth, such as mole rats, have
extremely developed masseteric, pterygoidal, and buccal musculature and the
zygoid arch and temporal fossae reflect this as well as a large caudoventral
process of the mandible for the massteric (the teeth are dominated by incisors,
whereas the remainder of the teeth are reduced to more peg-like molars).

  Thus it seems that *Zalambdalestes,* with a jaw elongated and with a full
arrangement of teeth, was not a likely burrower or feeder upon termites and
ants. As for the issue of a Cretaceous myrmecophagous mammal ... if there was
one in the Jurassic, it's just as possible for one to exist in the Cretaceous.
We have an early half of the Period dominated by tooth-based insectivore-like
taxa, so it's easy to skip over any others, not to mention preservation being
best known in a few places on earth, as opposed to well-sampled Triassic, Late
Jurassic and Late Cretaceous sediments all over the world.


Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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