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Re: Dinosaurs Eating Mammals! Oh No!



<<This identification follows specimens of the latter which are known to
bear an os calcaris and a calcareous spur, as in living monotremes, thus
showing that *Sinosauropteryx* ate possibly poisonous mammals.>>

I find the 'venom' aspect of the Hurum et al, 2006 paper far from
convincing, Jaime.  Perhaps I'm missing something, but that part of the case
is built entirely on the venom of the male platypus, which is delivered via
tarsal spurs.  Having identified those in a number of fossil mammals is one
thing: some multituberculates, some eutriconodonts, all the Yixian
'symmetrodont' genera and an unpublished docodont.  Suggesting those spurs
are possible delivery systems for venom in all those cases strikes me as
going over the top, as no evidence of specialisations for delivering poison
was presented.

On the first page, they mention tarsal spur-like structures are known from a
number of tetrapods.  Various placentals, marsupials, some kind of chemeleon
and a toad all get cited.  They also point out none of those are venomous.
For example, the structure in bats is connected with the base of the wings.

While tarsal spurs could perhaps maybe possibly indicate huge swathes of
small Mesozoic insectivores and herbivore-omnivores were venomous, it might
be a sign they all had wings; perhaps venom delivering wings.  As one
/Zhangeheotherium/ appears to lack the spur, the possible venom delivering
wings may have been restricted to adult males.

I can't help thinking that huge swathes of living Mammalia have lifestyles,
which give them much the same challenges as their Mesozoic counterparts.  If
venom were useful for defence 125 million years ago, then it still should
be.  That would explain the vast numbers of venomous rodents, excepting for
the detail that there aren't any.

It's an intriguing and interesting study, but I wish they'd selected a
different title.  "Were mammals originally venomous?"  As I can't see any
particular reason for thinking so, the parsimonious answer appears to be:
probably not.  Of course, that's the unqualified opinion of an amateur.

What's certain is that the /Sinosauropteryx/ involved was very naughty
indeed.  Taking two /Zhangheotherium/ and a /Sinobaatar/ was disgraceful
behaviour, and isn't the sort of thing to be encouraged.
Cheers
Trevor

Mesozoic Eucynodonts
http://home.arcor.de/ktdykes/meseucaz.htm
The Mesozoic, more than just the dinosaur.