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Re: Dromaeosaur questions (long, I think)



Now that I'm back in my dorm with references, time to answer a few posts...

Matías Soto wrote-

> I can confirm now that here in Uruguay we have teeth from a Late
> Jurassic-Early Cretaceous dromaeosaur (and a big one, height = 28 mm.).
The
> teeth, besides bieng laterally compresed and apically recurved, shares a
lot
> of characters with those from _Dromaeosaurus albertensis_ including low
> DSDI, torsionated anterior carina, chisel-shaped denticles...
> It cannot be a convergence. I know that there are some teeth worlwide that
> have this features too, which can be included (I suppose) in the
> Dromaeosaurinae.

Perhaps.  Low DSDI's are found in almost all theropods (except some
dromaeosaurs, Richardoestesia, Dryptosaurus, Eotyrannus and Gojirasaurus)
though, as are chisel-shaped denticles (as opposed to pointed denticles).

> 1) How distinctive is the twisted anterior carina?  Although Currie (1990,
> 1994, 1995) says it is diagnostic for _D. albertensis_, it appears other
> non-avian theropods shares this feature too: some _Saurnornitholestes_
> teeth, tyrannosaurids (Sankey et al., 2002), _Acrocanthosaurus_ and
> allosaurids (Currie & Carpenter, 2000) and even all carnosaurs (Feduccia,
> 2002, thanks Mickey!). It seems to me it doesn't have any diagnostic value
> by itself. What do you think?

I'd trust nothing Feduccia says about non-avian dinosaurs (and very little
he says about any Mesozoic dinosaur), but note Paronychodon and
Archaeopteryx are also supposed to have this character (Rauhut, 2002).

> 3) Do you know any other dromaeosaurid from South America (or even
Gondwana)
> from Late Jurassic-Early Cretaceous times? I think there aren't (of course
> there are possible dromaeosaurs from Late Cretaceous of Sudan, Brazil,
> Argentina, Madagascar), so, due to biogeographical and chronological
> reasons, besides the great relative size of the teeth, do you think it is
> convenient to create a new taxon?

undescribed dromaeosaur (Goodwin, Clemens, Hutchison, Wood, Zavada, Kemp,
Duffin and Schaff 1999)
Tithonian, Late Jurassic
Mugher Mudstone, Ethiopia
Material- (JN-96-2B/UCMP 170803) tooth
Reference- Goodwin, M. B., Clemens, W. A., Hutchinson, J. H., Wood, C. B.,
Zavada, M. S., Kemp, A., Duffin, C. J., and Schaff, C. R., 1999, Mesozoic
continental vertebrates with associated palynostratigraphic dates from the
northwestern Ethiopian Plateau: Journal of Vertebrate Paleontology, v. 19,
n. 4, p. 728-741.

undescribed possible dromaeosaur (Currie, Rich and Rich 1996)
Early Aptian, Early Cretaceous
Wontohoggi Formation of the Strzelecki Group, Victoria, Australia
Material- (NMV P186343) tooth (Currie, Rich and Rich 1996)
Description- serrations only present on posterior edge.
Comments- This character is also known in troodontids and some basal
coelurosaurs.
Reference- Currie, P.J., Vickers-Rich, P., and Rich, T.H. (1996). "Possible
oviraptorosaur (Theropoda, Dinosauria) specimens from the Early Cretaceous
Otway Group of Dinosaur Cove, Australia." Alcheringa 20(1-2): 73-79.

undescribed 'velociraptorine' (Long 1998)
Early Albian, Early Cretaceous
Eumerella Formation of Otway Group, Victoria, Australia
Material- teeth
Description- teeth moderatly recurved with coarse posterior serrations and
no anterior serrations.
Comments- These characters are also found in troodontids and Microraptor.
Currie, Rich and Rich are studying these teeth.
Reference- Long, 1998. Dinosaurs of Australia and New Zealand and other
animals of the Mesozoic Era.

Only create a new taxon if you can distinguish your tooth from all other
named teeth.  I don't think size doesn't count as a distinguishing feature.
Besides, there are other large dromaeosaurs with 'dromaeosaurine' teeth,
like Achillobator.  It might be a good subject for a publication anyway, due
to its potential biostratigraphic importance.

> 4) Is it possible to estimate the total lenght of the animal?
> _D. bornholmensis_ lenght was estimated, for a 21 mm. high tooth, in more
> than 3 metres.

It's about twice the size of teeth in the Dromaeosaurus holotype, so may
have been 3-4 meters long.

Mickey Mortimer