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Sickle-claws, theropod infanticide and Valerian



Graydon wrote: 

> > Otherwise, no 
> >other data can be used to support the idea that dromies were 
> >specialized to large prey. 
> 
>What do you call the big sickle claws?  They're way overkill for 
>comparably sized critters. 

I agree.  The enormous sickle-claw of _Deinonychus_ is a big thing to lug
around all day, especially if all it's used for is to evicerate Cretaceous
frogs and mammals.  I suspect it targeted much larger prey.

> > It seems plausible 
> > to suggest more ambushing-like attacks for the dromaeosaurs based on 
> > limb design.... 
>
> I do wonder if the metatarsus is short as an asstance to power 
> transmission in using the sickle claws; it wouldn't apply to 
> oviraptorids, though. 

John Ostrom has a word or two to say on this in his 1969 YPM paper on
_Deinonychus antirrhopus_.  (Haven't got the exact ref handy).


Stephan Pickering wrote:

> Using the remarkable Coelophysis Ghost Ranch specimens as a fulcrum, one
> can advance possible ideas about the taxon. Undoubtedly, there was
> pressure on dominant females (egg production, parental care = stronger,
> more adaptable biochemistry than males, plus larger size than males for
> nest protections) to form colonies directly linked to their selections
> of hunting habitats. 

This is a very interesting topic indeed, although I think in restoring the
personal life of _Coelophysis_ in too much detail we may be overreaching the
available evidence.  A few things to note (some mentioned already by Jaime):

(1) There is no published quantitative morphometric study that I know of
that has unequivocally established that adult _Coelophysis bauri_ specimens
are subdivisible into two discrete morphs.

(2) If two _C. bauri_ morphs ("gracile" vs "robust") are indeed
identifiable, then reasoning which is the male and which is the female may
not be cut and dry.  (Notwithstanding the variation in the crocodile-like
morphology of the proximal caudals, which I've only seen described in a
popular science article for _T. rex_).  The preservation of ova in the body
cavity (a la _Sinosauropteryx_) will help on this score.  Relative body size
or proportions alone may not solve the problem (particular since subadults
may be difficult to distinguish from the adult gracile morph).  True, many
modern bird species feature larger females than males; but others do not.
As it happens, male dodos for example were much larger than females; and the
size disparity was even greater for the solitaire.

(3) The relative positions of the adult (the alleged eater) and the juvenile
(the alleged "eatee") need to be established as ecological rather than
taphonomic.  In other words, the latter has to be shown to be *inside* the
former's ribcage, not underneath - as mentioned on several occasions by Rob
Gay.

(4) In order to propose that _C. bauri_ is the "only theropod found in
sufficient numbers to qualify as a colony, in one location" you have to
establish that the mass assemblage of _C. bauri_ is the result of a single,
sudden catastrophe rather than a gradual cumulation over time.

On the gruesome topic of vertebrate infanticide...

> males/females killing offspring to alleviate pressure for
> scarce food supplies (fewer young = less pressure on hunting)

Many dinosaurs show a degree of polymorphism between adults and juveniles -
a result of non-proportional growth trajectories during ontogeny (in other
words the young are not merely scaled-down versions of their parents, but
have different proportions).  In theropods, young tyrannosaurs have longer
legs, as do archaeopterygids in which the young also have more recurved
teeth (if _Jurapteryx_ is indeed a young _A. lithographica_ - there are
contrary opinions on this).  Such polymorphism may have been designed to
minimize competition between adults and young.  Insects and many other
arthropods take this to the extreme, and excel in it.  (The drawback is that
the species has to succeed in more than one niche.)


David Marjanovic wrote:

> BTW, I have mentioned this onlist some months ago; I haven't found out >
yet, neither looked up, who exactly those emperors Valerius and 
> Valentinianus were. 

The Emperor Valerian ruled 253¨C260 A.D. and met a sticky end after being
captured by the Persians.  

There were several emperors named Valentinian.  Valentinian I (Roman emperor
of the West, 364¨C75), was one of the unsung heroes of antiquity, holding
the empire together in the face of impossible odds.  His son and successor,
Valentinian II (ruled 375¨C92) had trouble even holding onto power, and was
assassinated at a young age.  Emperor Valentinian III ("ruled" 419¨C55) was
even more of a disaster; though by this time there wasn't much left of the
Roman empire in the West to defend.

By the way, officianados of the entire "w" vs "v" vs
diphthong-before-vowel-sound thing might be interested to know that the
ancient city of Ilium (Troy) was called "Wilusa" by its overlords in the
Hittite Empire. 

Phew - my fingers are tired.  Back to my gel.



Tim


------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163