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Re: tiny-armed theropods



On Fri, Oct 21, 2011 at 9:10 PM, Jaime Headden <qi_leong@hotmail.com> wrote:
>
>   Although coordinating the type species as specifiers for the clade 
> definition, one could claim it could have anywhere from two to three type 
> specimens.

Although similar in function, specifiers (for a clade definition) are
not really the same thing as types (for a rank-based definition). Both
serve a similar purpose (anchoring the name to reality, either
directly or indirectly), but they do so in different ways. (Specifiers
are basically constants in a definitional formula which unambiguously
indicates a set given a phylogenetic context; types are, at least
ostensibly, standards which indicate more inclusive sets, the sizes of
which are specified by the taxonomist rather than the code.)

Furthermore, a rank-based name can only have one type (although in
some cases that type could be a series), but phylogenetic names
usually have multiple specifiers. (The only exception I know of is
Wagner's "Panbiota", defined as "the first ancestor of _Homo sapiens_
and all descendants thereof".)

On Sat, Oct 22, 2011 at 8:06 AM, Robert Schenck <schenck.rob@gmail.com> wrote:
> What /would/ the type specimins be for dinosauria? Megalosaurus and
> Iguanodon (old name /and/ representative, at least as saur and ornith
> ischians?) Or would it be /passer domesticus/, as a living
> representative? Again, pretending that it was necessary or feasible?

_Passer domesticus_ would not be recommended as an internal specifier
for Dinosauria under the PhyloCode.

"Recommendation 11A. Definitions of converted clade names should be
stated in a way that attempts to capture the spirit of traditional use
to the degree that it is consistent with the contemporary concept of
monophyly. Consequently, they should not necessitate, though they may
allow, the inclusion of subtaxa that have traditionally been excluded
from the taxon, as well as the exclusion of subtaxa that have
traditionally been included in the taxon. To accomplish this goal,
internal specifiers of converted clade names should be chosen from
among the set of taxa that have been considered to form part of a
taxon under traditional ideas about the composition of that taxon, and
they should not include members of subtaxa that have traditionally
been considered not to be part of the taxon.

"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 bucklandii
Mantell 1827, Iguanodon bernissartensis Boulenger in Beneden 1881, and
Hylaeosaurus armatus Mantell 1833."

-- 
T. Michael Keesey
http://tmkeesey.net/