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Re: Cladistic definitions of Dinosauria, Saurischia, Sauropodomorpha



2005/9/16, Mike Taylor <mike@miketaylor.org.uk>:
> Are there "generally accepted" cladistic definitions of Dinosauria,
> Saurischia and Sauropodomorpha that seem to be winning out?  As an
> example, within Sauropoda, it seems clear that Wilson and Sereno's
> 1998 definition of Diplodocoidea as (_Diplodocus_ not _Saltasaurus_)
> is now used more or less universally.  But I know that there are
> various competing candidate anchors for Dinosauria (e.g. _Triceratops_
> and _Passer_, _Megalosaurus_ and _Iguanodon_) and I wondered which way
> the wind is now blowing.

Well, it seems that most widely used definition is Dinosauria =
Saurischia + Ornithischia. : )

(I've listed some of those definitions in:
http://www.geocities.com/rmtakata/dinosauria/dinosauria.html)

The PhyloCode draft recommends not to use extant birds as anchor
(internal specifiers) for Dinosauria:

Recommendation 11A:
"[...]
Example 1. The name Dinosauria was coined by Owen for the taxa
Megalosaurus, Iguanodon, and Hylaeosaurus, and traditionally the taxon
designated by that name has included these and certain other
non-volant reptiles. It has not traditionally included birds. Although
birds are now considered part of the dinosaur clade, the name
Dinosauria should not be defined using any bird species as internal
specifiers. Such a definition would force birds to be dinosaurs, thus
trivializing the question of whether birds are dinosaurs. Instead,
internal specifiers should be chosen from among taxa that have
traditionally been considered dinosaurs; e.g., Megalosaurus bucklandi
von Meyer 1832, Iguanodon bernissartensis Boulenger in Beneden 1881,
and Hylaeosaurus armatus Mantell 1833."
http://www.ohiou.edu/phylocode/art11.html

My feeling says that, despite the recommendation above, the
clade(_Triceratops horridus_ + _Passer domesticus_) is more commonly
used (influential authors such: Padian, Sereno, Weishampel use it - or
a variation). IIRC, that was the first phylogenetical definition for
Dinosauria.

[]s,

Roberto Takata