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Dinosaur Genera List corrections #67



Nino Perez-Moreno's communication prompts this DGL correction. With
_Neovenator salerii_ published in

Hutt, S., Martill, D. M. & Barker, M. J., 1996. "The first European
allosaurid dinosaur (Lower Cretaceous, Wealden Group, England)," Neues
Jahrbuch fuer Geologie und Palaeontologie, Monatsheften 1996(10): 635-644.

the listing for _Neovenator_ must be changed to

Neovenator Hutt, Martill & Barker, 1996

It is no longer a nomen nudum attributed to our own Darren Naish.

Another change is occasioned by publication of the following:

Novas, F. E. & Molnar, R. E., eds., _Proceedings of the Gondwana Dinosaur
Symposium_, _Memoirs of the Queensland Museum 39_(3): [iii] + 490-731
[December 20, 1996; Novas is listed as F. A. Novas in the title page and
introduction to the volume, but the correct middle initial is E.].

wherein we have the paper

Novas, F. E., 1996. "Alvarezsauridae, Cretaceous basal birds from Patagonia
and Mongolia," in Novas, F. E. & Molnar, R. E., eds., 1996: 675-702.

Here Novas formally describes the dinosaur _Patagonykus puertai_, so we must
revise the listing for that genus to

Patagonykus Novas, 1996

It is no longer a nomen nudum.

Novas classifies _Patagonykus_ in Alvarezsauridae and in turn classifies
Alvarezsauridae in Avialae as a "metornithine" bird higher up the cladogram
than _Archaeopteryx_. Unfortunately, his character matrix contains so many
reversals and unknowns as to make the analysis dubious. But based on his
description, I would agree that _Mononykus_ and _Patagonykus_ are related
(they're just not particularly closely related to _Alvarezsaurus_), though I
don't see the relationship as being particularly close.

In the same volume, the following paper

Chiappe, L. M., Norell, M. A. & Clark, J. M., 1996. "Phylogenetic position of
_Mononykus_ (Aves: Alvarezsauridae) from the Late Cretaceous of the Gobi
Desert," in Novas, F. E. & Molnar, R. E., eds., 1996: 557-582

defends the classification of _Mononykus_ in Alvarezsauridae and
Alvarezsauridae as an avialan taxon above _Archaeopteryx_. The authors state
in their conclusion, "In using a cladogram to determine evolutionary
relationships, one need only assume that the hierarchical distribution of
characters reflects the evolutionary relationships of taxa. The possible
function of a particular structure, or a scenario about how a particular
structure or function arose are not relevant. Instead, the relationships
identified by cladistic analysis are the ones that provide the framework for
testing functional or adaptational hypotheses...and to use these scenarios as
evidence for or against a phylogenetic hypothesis confuses the phenomenon to
be explained with the explanation for the phenomenon..."

Well, first of all, the assumption noted in the first quoted sentence has
>never< been tested, indeed, likely >cannot< be tested. There is no way to
verify that a cladogram reflects the evolution of a taxon, because there is
no way to go back in time to actually follow the evolution of the taxon. We
>must< allow for the possibility that in certain circumstances, homoplasy
will overwhelm the analysis and generate an incorrect cladogram. Of 20
cladograms with a 95% confidence level, we may expect one to be incorrect;
95%, even 99.99%, confidence is >a long way away< from 100% confidence! The
question is, when can we begin to doubt the cladogram?

In their statement, the authors of the paper effectively inform us that
unless someone else creates a more detailed cladogram that shows a different
set of relationships among the taxa, their cladogram must stand. Thus, it is
up to the functional analysts to explain how, for example, _Mononykus_
redeveloped a dinosaur-like tail with elongate haemal arches from an avialan
tail like that of _Archaeopteryx_, evolved an arctometatarsalian pes nearly
identical in shape to those of certain coelurians and ornithomimosaurs but
unlike any [other] avialan pes, reacquired a fourth trochanter on the femur
(Novas: p. 688), and so forth, in order to fit the evolutionary pattern
implied by the cladogram. After a while, there are just too many reversals
and too many anomalies to be explained, and it becomes time to reexamine the
cladogram to see whether or not it might just be one of those cases outside
the 95% confidence level, without necessarily having to go to the trouble of
gleaning the fossils of ever more characters. Perhaps there are too many
question marks among the 0's and 1's of the character matrix? Perhaps the
authors have enumerated too many characters associated with reduction and
vestigialization (reduced forelimb and manus, reduced keel on sternum,
reduced fibula, etc.), which might be expected to occur repeatedly as
homoplasies in different clades, as adaptations to a particular lifestyle? I
agree that, logically, we must proceed from character analysis to
evolutionary scenario, not vice versa. But there is no reason why, under
certain circumstances, the process should stop after a single iteration and
forbid the scenarios some input back into the character analysis.

In putting forth the concept of infallibility of cladograms and cladistic
analysis, it seems as if the authors themselves make a statement that, in
their concluding words, lies "outside the lines of modern systematics and
comparative biology."

Genera count remains stable at 801.