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RE: Princeton Field Guide



For those who haven't seen my review and commentary yet-
http://theropoddatabase.blogspot.com/2010/10/princeton-field-guide-to-dinosaurs.html
http://theropoddatabase.blogspot.com/2010/10/princeton-field-guide-to-dinosaurs_07.html
http://theropoddatabase.blogspot.com/2010/10/princeton-field-guide-to-dinosaurs_08.html
http://theropoddatabase.blogspot.com/2010/10/princeton-field-guide-to-dinosaurs_14.html

Gregory Paul wrote-

> It is of course not possible to provide an extensive description for each
> dinosaur species. In field guides for extant organisms the descriptions are
> entirely superficial descriptions of visually filed spottable identification
> markings and shapes (detailed technical morphology is not discussed), and
> these are consistently available for each species so the descriptions are
> similar in length for every species. The amount of information for dinosaurs
> ranges from almost as good as for living animals in those few cases in which
> feathers and their color patterns have been preserved and documented, to
> virtually nothing for many poorly known species, so the amount of information
> that can accompany the species ranges from extensive to zero. There is of
> course no need to include with each theropod species that it was bipedal, that
> was noted in the description for the entire group. Same for most of them being
> tridatcyl. Each species description includes only those features limited to
> that species that can be used to distinguish it from other species. In some
> cases there is no special features available so they are either "standard
> for the group" or "insufficient information." For example, what nontechnical
> feature/s suitable for a popular field guide distingush/es Argentinosaurus
> it from other giant titanosaurs? Suggestions, anyone?

Well, the original diagnosis (Bonaparte and Coria, 1993) was-

"Titanosaurs of great size with the following associated characters:
opisthocoelous dorsal vertebrae provided with very developed 
hyposphene-hypantra,
with extra articulations between them. Anterior dorsals with transversely wide 
and
anteroposteriorly planar neural spines, endowed with robust prespinal laminae. 
Middle
and posterior dorsals with low and wide vertebral bodies, with the ventral face 
almost
planar, and with pleurocoels located in the anterior half of the body. Sacral 
vertebral
bodies 2 to 5 very reduced. Dorsal ribs of tubular, cylindrical, and hollow 
structure.
Bony macrocells in the sacrum and presacral vertebrae. Slender tibia with short 
cnemial
crest."

Now, as with many (most?) published diagnoses, this one is full of 
symplesiomorphies and vagueness, but I suppose the former shouldn't be a 
problem for a field guide as long as they help distinguish it from other taxa.  
Field gides are also often as technical as external morphology will allow.  
Just look at the glossary of Peterson's field guide to Western Reptiles and 
amphibians- anal spur, auricular scales, axilla, costal groove, cycloid scale, 
fontanelle, etc..  It'd be simple to include a picture of each element at the 
beginning with arrows indicating what a neural spine, centrum, pleurocoel, etc. 
is, as well as the standard simplified centrum drawing to indicate what 
amphicoelous, opisthocoelous, etc. mean.  Then for Argentinosaurus' entry, its 
illustration could be a dorsal in front and side views, with numbered arrows 
pointing to numbered features in the descriptive section- well developed 
hyposphene (1); anterior dorsal neural spines flattened front-to-back (2); 
robust laminae on front of neural spine (3); middle and posterior dorsal centra 
low and wide (4); bottom face of centrum almost flat (5); pleurocoels placed in 
front half of centrum (6); etc.  Then in the comments you could give some basic 
info like "This was described as one of the largest dinosaurs known.  The 
fibula was first identified as a tibia."  That's how I'd want a dinosaur field 
guide to be at least.  I understand it would be a lot of work, but I guess 
that's why nobody's made an actual dinosaur field guide yet.

> Canis poses an interesting problem for the current use in dinosaurology of
> genus as just a few species that form a monophyletic grade. Canis is a large
> genus with many fossil and extant species that vary considerably in size,
> anatomy and lifestyles. The living species can all interbreed easily and
> produce reproductlively viable hybirds (as per the new eastern coyote, which 
> has
> considerable wolf in it so it is bigger, more social and can take down
> deer), so it is unlikely that the genus will be split up. So lets consider the
> consequences if a clade of fossil canids was found that was way too
> anatomically different to be in the genus Canis, or to have interbred with 
> Canis
> species. Also that the different genus has clearly evolved from derived Canis
> species in a way that rendered Canis paraphyletic. Would it then be required
> to split living Canis into multiple genera despite their ability to
> interbreed?

Either that or place your new clade in Canis a well.

> The chasmosaurine cladogram in the new PLos One Sampson et al paper
> illustrates the potential problem in a dinosaur group. The chart is 
> suspiciously
> progressive, with a series of chasmosaur taxa eventually leading over time to
> Anchiceratops, Arrhinoceratops and then the ultimate Triceratops clade.
> Because the chasmosaurs from Chasmosaurus to Vegaceratops appear to be
> paraphyletic they have to be split into a bevy of genera despite varying only 
> in
> cranial adornments. This may well be an artifact of the cladogram based on the
> characters that happen to be analyzed, it is quite likely that the
> Chasmosaurus to Vegaceratops chasmosaurs are their own clade with minor 
> variations in
> display organs that constitute a typical, multispecies genus. Assume that in
> the future some but not all cladograms find that Chasmosaurus belli and
> russeli are paraphyletic relative to a more derived and very distinctive
> chasmosaurine, while other chasmosaurs are monophyletic? How would that be 
> handled
> at the genus level?

Either start calling it Chasmosaurus? russelli, or give it a new genus to make 
its name congruent with either topology (ala Pantydraco).

Mickey Mortimer