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

Re: Even more concerning the Triceratops/Torosaurus deal

Jaime Headden wrote:
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0

(Just for the record: the above suddenly appeared as part of the text when I hit the "reply" button.)

A su=
bstantial amount of the paper is taken to demonstrate metaplastic transform=
ation and development of the horns and domes in *Dracorex* and *Stygimoloch=
*=2C and from this the authors conclude that they are synonyms (apart from =
rather aberrant and unique open sutures in the dome of the latter=2C which =
diverges from all other so-called incipiently domed juvenile or subadult pa=
chycephalosaurids known to date)=3B moreover=2C they then note that *Pachyc=
ephalosaurus* itself is the largest roadblock to synonymizing these taxa in=
to it=2C such that the squamosal nodes are not even spikes but large knobs =
(with a broader circumference around the base than in *STygimoloch* OR *Dra=
corex* squmaosal horns=2C are rounded or bluntly accuminate=2C and much sho=
rter than the horns of the other taxa). They invoke metaplastic shange to r=
esult in this=2C along with erosion of the horns into knobs=2C but do not d=
emonstrate a parallel to test this hypothesis.

*Triceratops*, where the epiparietals and -squamosals start as pointed (..."acuminate", if you prefer) osteoderms, then fuse to the skull and each other, and then become broader and very blunt.

Essentially=2C the paper tak=
es us on a faith-based argument that metaplasia + erosion DOES result in th=
is transformation=2C and ignore the functional concerns that contradict the=
 theory (secondary sexual seletion should result in a seeming reverse trans=
formation than they offer: knobs into spikes) for the sake of the fine hist=
ological work (which I do not have an issue with. The authors seem to push =
(from almost the first paragraph of the introduction) that the synonymy is =
real=2C and go about detailing the evidence FOR=2C but not AGAINST.

Or, alternatively, sexual selection is just a bit more complicated than we used to think.

=A0 The reason I bring this up is that I should hope the currently pending =
work on chasmosaurine ceratopsids does not also fall into this argument=2C =
for I consider this work (fine) to be lacking in replicatability. Implicit =
in the argument is that the metaplastic transformation (and erosion thereaf=
ter) of the ornamentation in ceratopsids and pachycephalosaurids is used to=
 imply that a single taxon must arise from any development=2C

Does "a single taxon must arise from any development" mean anything? Because if so, I can't figure out what. Please help me out.

 and that beca=
use of this=2C the condition precludes the existence of multiple sister tax=
a (even coevals) with the same ontogenetic trajectory or metaplasticity dur=
ing growth. We are to assume that because they may be representative of a g=
rowth series=2C they represent the _same_ growth series of a single taxon. =
It beggars the imagination to assume that taxonomic diversity is so low for=
 a highly ornamented clade=2C unlike the observed specific variation only a=
mong Bovidae.

I don't think that's a good comparison. We're talking about just one ecosystem, one long but narrow strip of forested floodplain. I don't expect high diversity of anything there.

Windows 7: It helps you do more. Explore Windows 7.

Maybe you should use Windows Mail instead of Hotmail which replaces all your commas, semicolons and colons by hexadecimal codes and breaks the lines after a fixed number of characters...