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Egg-eating in mammals



Betty Cunningham wrote:

<This instect eater [*Jeholodens*] was not eating eggs
or ganging up to eat eggs, at least. What mammals from
Mongolia or China are you referring to? Dr Luo
suggests all early mammals that we've found are
insectivourous.>

  Typically, the selenodont condition in mammals
(elongate cusps) is retroactive to egg-eating, and has
been used to qualify a multifunctional
tearing/puncturing function which, when coupled with
the mammalian talonid basin, a pistle/mortar crushing
function for pulverizing little bits without applying
too much stress to the teeth. No extant egg-eater has
this. It is perfect for most artiodactyls as varied
phytophages (plant-eaters). (See Janis et al. (eds.),
1994)

  In fact, egg-eating requires a few features: a
crushing surface, and a sagittal or parasagittal
piercing apparatus. The crushing surface can be
anywhere along the alimentary canal in front of the
stomach, and in desypeltids occurs about in the
middle; Placodonts have incisiform "choppers" that can
serve to pierce, and locate the crushing apparatus in
the jaws, as may also oviraptorosaurs, with a
double-vaulted palate in oviraptorids, and a
single-vaulted palate in caenagnathids, and the former
possess functionally singular piercing structures in
the jaws as well. (See Gans, 1954; Grzimek et al.
(ed.), 1956; Barsbold, 1977)

  Typical conchophages must crack or pry the shell
open, as in sea otters, some vulturids, and many
carnivoran mammals such as *Canis aureus* [jackal] or
*Otocyon*, which do not use their jaws, but will crack
the shell with a stone or drop it to break it open. A
lack of functional shell-cracking anatomy makes them
less speciallized in this regard, and as far as I can
see, no mammal has these anatomical adaptations, nor
birds, and that may be why we see a lack of specialist
egg-eaters in these groups. (See Gans, 1954; Grzimek
et al. (eds.), 1956)

  Oviraptorids and placodonts are conchophages by all
corroboratory evidence, and some dicynodonts may also
be, and several unique adaptations of the jaws seen in
not only these extinct groups, but also dasypeltids
and some viperids, and in the throat of the latter,
may pertain to conchophagy as a specialization. (See
Gans, 1954; Romer, 1966; Barsbold, 1977; Sues and
Reid, 1997) Thus the evidence does not suggest mammals
were conchophages by anatomy, but only partially so by
behavior.

  I can also additionally say that, though anatomy may
not indicate it, unobserved behavior in extinct
animals could have been present in some taxa that
would indicate faculative conchophagy.

=====
Jaime "James" A. Headden

"Come the path that leads us to our fortune."

Qilong---is temporarily out of service.
Check back soon.

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