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Re: Re: DEFENSIVE RINGS AGAIN
>Again, I speak with less certainty than Darren, there, for certainty
>(especially about animals long extinct) is not a strong point of mine.
>But the presence in many topsies of "cheek" horns argues for a very
>effective defense against small fast carnivora, in that standing
>side-to-side, the adults even defend whatever gaps may be between them.
>
>Too, in the presence of small fast carnivora like those of the upper
>Mesozoic, undefended hatchling ceratopsians would have been topsy
>mcnuggets if their parents simply ran away every time something Ogly
>showed up.
CARNIVORA?!?!? Since when did any ceratopsian have to deal with the
Carnivora? These johnny-come-lately theropod wannabes weren't much of a
threat in the Mesozoic...
Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD 20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084
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dinosaur@lepomis.psych.upenn.edu Mon Jan 22 10:15:04 1996
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Subject: Re: Re: The Two Principal Dinosaur Clades Defined
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rowe@lepomis.psych.upenn.edu
>In a message dated 96-01-21 04:19:33 EST, pharrinj@PLU.edu writes:
>
>>I don't know. BADD seems like a straw man to me that no one believes
>>literally. Most authors I've read are pretty noncommittal about the
>>structure and habits of hypothetical stem groups.
>>
>>
>>> > If that is true, then BADD and BCF are not that far apart.
>>
>>Well, BADD and BCF are pretty far apart, but BCF and what most scientists
>>actually believe aren't!
>
>
>As an example of "what most scientists actually believe," allow me to insert
>the following excerpt from page 33 of the forthcoming _Mesozoic Meanderings_
>#2 third printing:
>
><<I have noticed an unfortunate evangelistic streak of arrogance and
>dogmatism among cladists, as if cladistic methodology is the "best" or "only"
>way to do taxonomy. Consider the following quotation from an article on
>dinosaur cladistics from the June 1995 issue of Natural History (p. 35 cols.
>12):
>
>"Although [cladistics] is not a perfect method (all scientific probing is
>subject to criticism and testing), cladistics is more reliable and objective
>than using the age of fossils, or their occurrence in particular layers of
>rock, to determine relationships. For example, cladistic analyses show that
>birds evolved from a small, carnivorous dinosaur, probably very like
>Deinonychus or Velociraptor. These dinosaurs, which belong to a group called
>dromaeosaurs, lived in the Cretaceous, between 107 million and 72 million
>years ago. Yet the oldest-known bird, Archaeopteryx, lived in the late
>Jurassic, about 140 million years ago. If we relied on relative geological
>age, we might conclude that the earliest birds gave rise to animals like
>Deinonychus and Velociraptor, rather than the other way around. Cladistic
>analysis indicates that the fossil record is probably not complete and that
>an animal very similar to Deinonychus gave rise to both the birds and later
>to the dromaeosaurs, including Deinonychus and Velociraptor. However, we have
>yet to find fossils of this creature. By using characters in cladistic
>analyses, we can test hypotheses about phylogenies, or family trees, but we
>do not seek to specify ancestors and descendants. We only hypothesize which
>animals are most closely related to each other. While using the geological
>age of fossils does not result in the most reliable phylogenies, it does
>provide an important context in which phylogenies can be placed. With
>cladistics, we thus have a much more realistic and objective view of where
>evolutionary lineages fit within geological time and where gaps exist in the
>fossil record." [Gaffney, Dingus & Smith, 1995]
>
>How many things can you find wrong in the above paragraph? (1) Nobody uses
>"the age of fossils, or their occurrence in particular layers of rock, to
>determine relationships." It is elementary paleontology to construct
>phylogenies and taxonomies from the anatomical features of fossils, not their
>position in the fossil record. And it misleads the reading public to give
>cladistics this straw man to knock down.
Well, in the best of pre-Hennig systematics this was true, but far too many
of the older literature was a connect-the-dot-up-the-column tree of
triolobites, radiolaria, hominids, etc.
(2) It is misleading to state that
>"cladistic analysis indicates that the fossil record is probably not
>complete." This fact was known since the time the true nature of fossils
>became understood, centuries before the rise of cladistics as a methodology.
Agreed!
> (3) It is false that "cladistic analyses show that birds evolved from a
>small, carnivorous dinosaur, probably very like Deinonychus or Velociraptor."
>No cladistic analysis is anywhere detailed enough to tell us anything more
>than pure generalities about the physical appearance of the common ancestor
>of birds and dromaeosaurs. Such analyses have presently described only a few
>of the characters that might have been present in the ancestral species.
>Indeed, in this work [Mesozioc Meanderings #2], I provide compelling reasons
>to think that the common ancestor of birds, Deinonychus, and Velociraptor
>resembled Archaeopteryx much more closely than it resembled those two
>cursorial dromaeosaurs.
I agree with that last sentence very much. However, a cladistic analysis
can give an hypothesis of the common ancestor of two linneages, that
hypothesis being characterized by the character states at the joining node.
> (4) "If we relied on relative geological age, we
>might conclude that the earliest birds gave rise to animals like Deinonychus
>and Velociraptor, rather than the other way around." Indeed, considering the
>quoted disparity in ages between the dromaeosaurs and Archaeopteryx, I often
>wonder why the cladists haven't gone back to their drawing boards to give
>their analyses some more thought. One of the features supporting BCF theory
>is its full agreement with this aspect of the fossil record; the authors of
>that paragraph really should read this bookwith an open mind. Incidentally,
>(5) the statement that dromaeosaurs "lived in the Cretaceous, between 107
>million and 72 million years ago" is incorrect in both bounds. The genus
>Palaeopteryx from Dry Mesa Quarry (Jensen, 1981; Jensen & Padian, 1989)
>provides evidence of a dromaeosaur-like form (I consider it a potential
>dino-bird) in the Late Jurassic Morrison Formation, while large dromaeosaur
>teeth are found in western North America as late as the Lance Formation and
>its equivalents, 65 million years ago (Derstler, 1994), and indeterminate
>species of both Dromaeosaurus and Velociraptor are listed among Lance
>dinosaurs by Breithaupt (1994b). Finally, (6) any statements about the
>reliability and objectivity of cladistic analysis relative to other forms of
>phyletic analysis must be considered groundless, because there is no way to
>confirm that any phylogeny generated by any method whatsover is the True
>Phylogeny. (This caveat applies to the BCF phylogeny as well.) At best, we
>can only state that some of the cladistic phylogenies seem to converge toward
>a phylogeny that, with some degree of confidence (calculated by certain
>greatly suspicious statistical methods), may be the one True Phylogeny.
>Whether such convergence is toward the one True Phylogeny or toward an
>artifactual phylogeny resulting from hidden problems in the analytical method
>is presently anyone's guess.>>
Good observations indeed.
Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD 20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084