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Re: Platypuses may be older than we think...

Tim Williams writes:

Nevertheless, monotremes (both living and extinct) can be broadly divided into two categories: 'diggers' and 'swimmers'.

Unfortunately, platypus are also excellent diggers (since they nest in extensive burrow systems), thus demonstrating that a forearm adapted for digging isn't necessarily incapable of swimming (or vice versa).

I'm not sure exactly how we'd extrapolate a swimming lifestyle for fossil monotremes known mainly from skull fragments, unless we assume that advanced electrosensors in the jaw are only of use to an aquatic animal (the electrosensing abilities of echidnas appear to be almost vestigial compared to those of the platypus). On the whole that may not be such a bad assumption - of course, just because most extant species that rely heavily on electrosensors seem to be aquatic doesn't mean that there weren't some extinct terrestrial species that also relied heavily on it.

I wonder if a burrowing animal with poor eyesight would benefit from such a system?


Dann Pigdon
GIS / Archaeologist              geo cities.com/dannsdinosaurs
Melbourne, Australia             heretichides.soffiles.com