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Re: ptero and bat origins



I really like the new hypothesis on the origin of pterosaur wings and
pterosaur flight. If only because there has never been a detailed
alternative. :-)

> Was wondering if anyone has done anything similar with the
> "shrewy-looking placental" to bat transition?

Not that I know of, but I don't know much... well, except by Ebel (1996) who
doesn't get into any details, bats are thought to have come trees-down, and
most think there was a gliding intermediate (see below), but maybe the
(speculative) habit of catching insects with the hands was enough to evolve
into the flight stroke. Hm.

1. and 2. are very good questions.

> 3. Has any one yet figured out what the closest sister taxon to bats
> might be?

In molecular analyses, sometimes Eulipotyphla ("core insectivores") are in
that place, but that's probably a slight case of long-branch attraction.
Normal is:

Laurasiatheria (misnomer)
|--Eulipotyphla
`--Scrotifera
     |--Chiroptera
     `--Fereuungulata
          |--Cetartiodactyla
          |--Perissodactyla
          `--Ferae
               |--Carnivora
               `--Pholidota

Unfortunately this sister taxon is a bit big, and gives just about 0
revelations about the origin of bat flight. Yes, we can assume that the
first scrotiferan looked like a shrew. :-)
(Perissodactyla are either the sistergroup to Cetartiodactyla, forming
Euungulata, or to Ferae, forming Zooamata. Mammal clade names are
concept-based.)

Morphologically there are several shared characters with Dermoptera (Chiro-
+ Dermoptera = Volitantia), including the wing membrane extending between
the fingers. Great for those who like a glide-flap transition, used to be
their main argument. Other traits are shared with Dermoptera, Scandentia and
Primates, e. g. some eye features. The latter three are related to each
other in molecular trees as well, but closer to rodents than to bats. That
the name Scrotifera exists suggests that some synapomorphy exists that fits
in the molecular tree, but I don't know it.

Fossils don't help either. The oldest and basalmost bats are fully winged
and have the ears for echolocation, where preserved. There are probable
Paleocene bat teeth, but these are referred to a normal Eocene genus.