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Re: Ceratonykus braincase described



On 01.05.2011 08:34, Tim Williams wrote:

 I should have specified *large* myrmecophagous birds (i.e., larger
 than 1 kg). Small mammals (under 1 kg) that specialize in eating
 ants or termites can have comparatively high body temperatures and
 high basal rates of metabolism (McNab, 1984) - such as those species
 of elephant shrew (Macroscelidea) in which the diet is mostly made up
 of termites.

I thought "myrmecophagy" was not so much used literally ("ant-eating") as for ecological niches that involve eating comparatively tiny insects en masse instead of attacking them individually, sort of like how a grazing herbivore doesn't eat individual grass blades. This would exclude animals for which such insects are not "comparatively tiny" (much smaller than the head); they would just be ordinary insectivores with an unusual prey spectrum. As far as I know, this latter category includes all birds that eat mostly ants and/or termites. Unlike myrmecophages, they lack special adaptations for eating insects en masse (long tongue, tubular head, huge claws...).

While I am at it, I have long wondered if xenarthrans are plesiomorphically myrmecophagous, with reversals in the herbivorous sloths, various omnivorous armadillos, and by extension the herbivorous glyptodonts and pampatheres. This would in particular explain their peculiarly simplified teeth, which -- like those of *Fruitafossor* -- lack enamel* and have such simple shapes that the experts do not try to homologize them to the premolars and molars of other mammals.

Myrmecophages need not be exclusive myrmecophages. The giant armadillo with its 100 teeth is a good example: http://en.wikipedia.org/wiki/Giant_Armadillo

* Except in a Paleocene animal that is usually thought to be the oldest armadillo but has been suggested to be a stem-xenarthran.