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Re: Sky Monsters - Nat. Geo. channel
T. Michael Keesey wrote:
CMIIW, but don't both the ornithodiran archosaur and the
prolacertiform hypotheses advocate _Sharovipteryx mirabilis_ as a
pterosaur sister taxon?
You know, I'm not sure. I don't even know if _Sharovipteryx_ is an
As I recall, there was a talk at SVP this year showing that the
mutation for yielding long fingers is relatively simple, so bats may
have evolved practically overnight (in geological terms, of course).
Another factor may be that the Chiroptera might have been among the first
mammal 'orders' to evolve after the K/T extinction, when placental
diversification was proceeding at a rapid tempo.
Of course, you'd still expect there to be some gliding outgroups,
Bats probably evolved from a mammal that at least looked like a colugo,
given that colugos already have a patagium between the fingers and toes (see
below). Gliding marsupials and rodents do not have these patagial
'mittens'. You can see why the idea that bats and colugos share a unique
ancestry was so attractive. There are some researchers who still support a
colugo-bat link, and fie to the molecular evidence.
and we haven't found those, but small, arboreal animals (particularly
tropical rainforest dwellers) are notoriously rare in the fossil
Also, if we found these proto- or para-chiropterans, would we necessarily
recognize them as gliders? This is notoriously difficult for fossil
mammals. For example, this issue has come up for certain extinct arboreal
placentals known as paromomyids (which, as members of the 'order'
Plesiadapiformes, are thought to be related to colugos and primates).
Paromomyids have been restored as gliders in the manner of modern colugos,
which have a patagial membrane between the fingers and toes ('mittens').
This hypothesis was based on the similar structure of the hand skeleton
between colugos and fossil paromomyids, suggesting that the latter were also
'mitten-gliders' (Beard, 1990, 1993). However, this interpretation was
criticized by other researchers (Hamrick et al., 1999), who claimed that the
phalangeal proportions of paromomyids did not support the hypothesis that an
interdigital patagium was present. Instead, the phalangeal proportions
shared by colugos and paromomyids appear to be associated with vertical
climbing and clinging, not 'mitten-gliding'. (This does not actually prove
that paromomyids were not gliders, merely that there is no evidence for a
colugo-style interdigital patagium, nor for any other specializations for
gliding in the skeleton, in paromomyids.)
There's also the case of the fossil Eomyidae, which were not thought to have
included gliders until one specimen showed up preserved with a patagium
(Storch et al, 1996).
I missed that talk, unfortunately, but perhaps someone else can say more.
Didn't see it either, but I know the researcher in question is Karen Sears.
I think _New Scientist_ had an article on her SVP presentation.