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Re: Morpho v molecular (was Re: Tinamous: living dinosaurs)
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- Subject: Re: Morpho v molecular (was Re: Tinamous: living dinosaurs)
- From: David Marjanovic <email@example.com>
- Date: Wed, 29 Jun 2011 10:58:36 +0200
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Just to clarify, I didn't mean to give the impression that all (or
even most) paleontologists dismissing the hypothesis of any kind of
hippo-whale clade (Cetancodonta or Whippomorpha). Sorry about that.
What I was saying is that those phylogenies based purely on
morphological/fossil data have not always upheld the derived
position of the Whippomorpha clade as recovered by molecular-based
phylogenies. As noted by Tom, the morphological/fossil phylogenies
usually recover some configuration of Cetancodonta/Whippomorpha; but
a link between cetancodonts and ruminants (Cetruminantia), as
proposed by molecular-based phylogenies, is usually not supported by
morphological/fossil data. The importance (or not) of the
anthracotheres in hippo and/or whale evolution is also the subject
of different viewpoints. Having a hippo-whale clade as derived
artiodactyls, closest to ruminants, is the essence of the
Whippomorpha hypothesis (Gatesy et al., 1996; Waddell et al., 1999),
and it's this aspect that I'm skeptical about. But I'm happy to be
proved wrong... by more fossils, not more molecular analyses.
But what you're actually talking about isn't the position of the whales
anymore. It's the position of the ruminants -- as I first said on this
list a couple of years ago.
Morphology traditionally puts the ruminants next to the camels (together
Selenodontia), molecules put them next to the whippomorphs.
My impression is that recent morphological analyses that contain halfway
serious numbers of fossils do not find any strongly supported position
for Ruminantia. There are lots and lots of Paleogene artiodactyls that
could be stem-ruminants or not, and apparently nobody has tried to sort
most of them out yet.
*Indohyus* has been compared to the tragulids (the extant sister-group
of all other extant ruminants) a lot. What if some of the similarities
are actually symplesiomorphic...?
Someone please sit down with the Paleogene artiodactyls and make a data
matrix with all of them. And order your potentially continuous
characters (Wiens 2001, Syst. Biol.).