FISSIPEDS & PINNIPEDS

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

> Cladists - descendants of last common ancestor of Tom and Andre the 
> Seal?  Or did felids and canids radiate before the fissiped/pinniped 
> branch?  Of course, these aren't archosaurs, but any thoughts on the 
> subject would intrigue me.  Thanks.
> John McLoughlin

Cladistics be damned (???), these two terms are defunct however you like your
organisms ranked. Pinnipeds are polyphyletic - phocoids ('true' seals) are
related to mustelids while otaroids (fur seals, sealions and walrus) are related
to ursids. So the Pinnipedia is no more, best analogy I can think of is the
?Gryphosauria, a taxon created in the last century for ichthyosaurs and
sauropterygians (admittedly, pterosaurs were in there too, so this was a _real_
mixed bag). Lacking as they were the knowledge we have nowadays of
palaeontology, anatomy and molecular systematics, the first zoologists created
some truly wonderful artificial groupings. My favourite is the Bruta, created
by Carl von Linne for elephants, pangolins, anteaters and basically all other
mammals he didn't know where to put. Incidentally, 'Primates' as envisioned by
Linnaeus included the bats! However, I digress...

Back to pinnipeds - as you might have guessed - some geneticists now think that
pinnipeds *are* monophyletic. This is at odds with the morphological evidence
and, last I heard, the controversy goes on.

Fissipedia (it means 'split feet') is the old term used back in the days when
the Carnivora was split into 3 suborders: Pinnipedia (see above), Fissipedia and
Creodonta. Creodonts probably share a late Cret/early Palaeocene ancestor with
carnivorans (so together they form the Ferae), but are different enough for
their own Order. And with 'pinnipeds' (whether polyphyletic or not) nested
within carnivorans, fissipeds are paraphyletic. To answer John's query, the 'cat
branch' and 'dog branch' diverged at the end of the Eocene (from miacoids, who's
taxonomy is a real nasty bit of work), and true cats seemingly evolved in the
mid Oligocene, a little earlier than any of the 'pinnipeds' evolved from members
of the 'dog branch'. At least, that's how I remember it. Really needs checking
up on... I'm just creating taxonomic hell aren't I....

"Keep firing at the saucers!"
(It starts Mr. Isles!)

DARREN NAISH