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Dino dimorphism (Was More tyrant Q & A's)



At 10:28 PM 12/9/98 -0800, Stan Friesen wrote:

>Yeah, as always, interpreting the fossil record is a tightrope.  There is
>lots of information there, but there is lots of noise, and lots of missing
>data as well.  Finding the pattern through the murk is often difficult.
>But then, I always did enjoy a challenge. (If it were *easy* it would be
>boring :-)

Agreed!

>[Ecological factors are one reason I suspect the old species level taxonomy
>of ceratopsians is massively oversplit].

Doubly agreed!!


Dwight Stewart wrote:
>So, if Tyrannosaurus rex males were smaller (& I think
>the evidence supports this) the "lion strategy"

Yikes!!  Please be careful of what the dimorphism evidence suggests.  The
data suggest that one morphotype, interpreted by some as the male, is more
gracile (i.e., for the same body size, it had more slender bones).  That's
it.  We do not yet at present have sufficient sample size to establish
which, if either, sex grew to the largest size.  Just because the specimen
FMNH PR2081 ("Sue") is a robust form, and is currently the largest known
specimen, doesn't really count for much: the next two biggest specimens are
gracile morphs.  Beware of small sample sizes!!

(It could be that male _T. rex_ individuals, although more gracile, reached
larger size.  Or not.  We can't tell.)

Dwight also wrote:
>For that matter, ALL modern humans are one species: Homo Sapien &

EEEeeekkk!!  Pet peeve alert!!

A) The trivial nomen (the second part of a species name) should ALWAYS be in
lower case!!

B) There ain't no such name as "sapien": it 'tain't grammatical.  The proper
trivial nomen for the human species is "sapiens".  The word "sapiens" is not
a plural of some word "sapien"; it is Latin for "thinking". (sapio, I think;
sapiere, to think; sapiens, thinking).

(Don't worry, though, you are FAR from the only person to make this mistake.)

I was going to add to take a look at the Chapman et al. review of sexual
dimorphism in dinos in the recent DinoFest volume, but others have already
beat me to it.  Really good stuff.

Later, folks.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661