[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Perching, climbing, roosting was Re: 11th specimen of Archaeopteryx

Thank you for clarifying this.  This is very much appreciated.

> Date: Sun, 13 Nov 2011 20:53:29 -0800
> From: keesey@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Perching, climbing, roosting was Re: 11th specimen of 
> Archaeopteryx
> On Sun, Nov 13, 2011 at 7:20 PM, Anthony Docimo <keenir@hotmail.com> wrote:
> >
> > Weren't stem-mammals traditionally regarded as reptiles?
> >
> > Odd, strange reptiles, but still reptiles.
> Yes, under the traditional usage of "reptile" to mean all amniotes
> except avians and mammals. But traditional Reptilia is a wastebasket
> taxon, and many have moved away from that usage (or, indeed, against
> using "Reptilia" in a formal sense at all).
> It should be noted, though, that traditionally stem-mammals were not
> considered phylogenetically closer to living "Reptilia" (lepidosaurs,
> testudines, crocodylians) than to mammals. As now, they were thought
> to share more ancestry with mammals than with other amniotes, but they
> were still relegated to the "Reptilia" wastebasket.
> You could almost see the traditional system as "merit-based". To
> escape a class, you have to evolve "enough". Thus, reptiles "escaped"
> Amphibia by evolving amniotic eggs and dry skin. Birds "escaped"
> Reptilia by evolving feathers, flight, and endothermy. Mammals also
> "escaped" Reptilia, by evolving hair, mammary glands, and endothermy.
> Needless to say, this is a very subjective system. A more scientific,
> phylogeny-based system has been gaining acceptance in recent decades.
> The only formal higher taxa recognized under this system are clades:
> taxa consisting of an ancestor and all descendants.
> Some workers use "Reptilia" to refer to the least inclusive clade
> containing the extant animals traditionally considered reptiles, i.e.,
> lepidosaurs, testudines, and crocodylians. This usage includes birds
> as a type of reptile, and excludes Synapsida (mammals and
> stem-mammals). Others just don't use the term "Reptilia". (I've also
> seen a proposal to limit "Reptilia" to just the lepidosaurs, but this
> has not been followed.)
> "Sauropsida" is an old name for the clade stemming from the earliest
> ancestor of lepidosaurs, testudines, crocodylians, and avians which
> was not also ancestral to mammals. It has seen a resurgence in use
> more recently. (It was coined along with "Theropsida", which was meant
> for the clade stemming from the earliest ancestor of mammals which was
> not also ancestral to lepidosaurs, testudines, crocodylians, and
> avians. "Synapsida" is generally used for that clade nowadays,
> though.)
> --
> T. Michael Keesey
> http://tmkeesey.net/