And for cold-blooded ones at that. Said
lizard at least sometimes follows its prey for 15 days. An endotherm would get
pretty hungry and impatient in that time.
Good point - and often such prey is
lost to conspecifics
Why "supposedly"?
I believe that
the general acceptance of a terrestrial lifestyle for ziphodont
crocodilians is, at best, the product of very tenuous extrapolation,
particularly with respect to the supposedly land-lubbing plethora of
Australian mekosuchines. The only ziphodont croc for which post-cranials have
been described is the Early Tertiary Pristichampus. A terrestrial habitus was
deduced for this taxon largely based on the presence of 'hooves'. I am told by a
trusted source who has recently observed the specimen in question, that these
were most likely a preservational artefact. But, even if this taxon was
terrestrial - its relationship to Australian species is not
well-understood. Thus, the argument for a terrestrial habitus in the crocs from
Oz reduces to one based on cranial and dental evidence that goes something like
this..... mekosuchines had laterally compressed, ziphodont teeth, a deep skull
and laterally directed orbits - theropods had similar skull and tooth
morphology.... theropods were terrestrial... therefor so were mekosuchines.
I find this reasoning wholly
unsatisfactory. The cranial and tooth morphology of mekosuchines may tell us a
lot about how they killed their prey - but next to nothing about where they
killed it. As pointed out previously, the same feeding tactic is used by some
sharks. When considered alongside a number of other relevant facts, the argument
for 'terrestriality' becomes very strained. These include the fact
that almost all mekosuchines have been found in association with aquatic
species (the few that haven't were within a few kilometres of a major
watercourse); a very high level of endemism among contemporaneous Miocene
species identified by Paul Willis; and the fact that some living, but far from
fully terrestrial crocs (e.g., Paleosuchus) actually exhibit laterally flattened
teeth, deep skulls and laterally directed orbits and the argument that
mekosuchines were terrestrial becomes an eminently debatable one. This is not to
say that it is incorrect - just that we need more data before we tie the
hypothesis down as fact. I've just had a MS accepted that addresses these
issues if your interested - certainly any comment or criticism is more than
welcome.
S. Wroe
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