SLOTHS-SEGNOSAURS-TERMITES

["Darren Naish" <dwn194@soton.ac.uk>]

> >With regard to speculation on the diet of these dinosaurs, ascribing an
> >insectivorous diet when the animals have edentate-type claws is probably
> >missing the point when edentates that hang around trees (the sloths - NPI)
> >are herbivorous.
>
> Sloths are not the only arboreal "edentates" (the proper term is
> Xenarthrans).                                          (Ronald Orenstein)

Some folks have an Edentata within the Xenarthra. Anyone know exactly what the
'Gravigrada' is though?

> The Tamandua and Silky Anteater, both insectivorous, also qualify.

Forgive me, I was having a bad day. For what it's worth though, xenarthrans
(possibly together with pangolins as an outgroup to the Epitheria) seemingly
diverged from other placentals as early as the Lower Cret. Pangolins (_Eomanis_)
and anteaters (_Eurotamandua_) make their debut in the Messel fauna of the
Eocene. It looks like _Eurotamandua_ was arboreal, and if so, the terrestrial
habit of some recent forms (esp. _Myrmecophaga_) is derived. They've retained
the big claws that their arboreal ancestors presumably evolved both to climb
with and to deal with insect nests (useful in combat too of course), a complex
scenario seeing as such exapted structures have co-evolved with their tubular,
fused, edentulous skulls. Tree sloths have no fossil record ASAIK, which isn't
too surprising really. They have teeth.

_Eomanis_ is, from what I've seen, thought to be something of a generalist, but
more terrestrial than some of the modern pangolins. I've gone on before about
how it is thought to be a herbivore on its way to insectivory (via leaf-cutter
ants!).

> I assume the claws of megatheres may have served to "hook" branches of trees
> to bring them within reach, not to dig up termitaria (a "burrowing" function
> that keeps the animal well above ground).

I have never seen anyone suggest that megatheres were insectivorous, and there's
no reason to suspect that they were. Their big guts, large body size and deep-
rooted, constantly-growing molars are very suggestive of herbivory - coprolites
prove that they were.

TERMITES

Someone asked about the fossil record of termites. While I believe this to be
pretty much irrelevant to the evolution of segnosaurs, termites were certainly
around in the Cretaceous: this has been known for a while but a partial nest
reported from Triassic strata last year showed that some were essentially modern
in habits and architecture. If this was the state of play in the Triassic, I
would expect Cretaceous tropical parkland environs to sport large termitaria of
an essentially modern appearance. Bees and wasps are well known from the
Cretaceous at least - many of these bugs would be making papery tree-nests
similar or very similar to those we can see today.

"Can I keep you?"

DARREN NAISH