Face of the Titanosaur (was Fossil Dinosaur Eggs Discovered/ was Titanosaur Eggs)

["Ralph Miller III" <gbabcock@best.com>]

William Monteleone <wmonte@concentric.net> writes:
> So we've seen the face of the titanosaur, maybe. The scaly skin
> impressions look a lot like other dinosaur skin impressions we've seen,
> a field of small regular beads. But on one of the specimens that's shown
> in most of the articles, there's also a row of larger scales which look
> suspiciously like snake lips. Many dinosaur artists have shown this row
> of larger scales on the lips of their critters, but is that what we're
> looking at here? Could this be a dorsal ridge, a ventral ridge, a
> nostril, or something else? Any ideas?

Let's consider what the authors of the _Nature_ paper have to say.  Chiappe
et al. state:
"Because these skin casts do not overlie bones, it is impossible to
establish their precise anatomical location.  However, the stripe probably
ran along the embryo's back."  (end of quote).

Because the rows of scales interlock but do not overlap or separate along
their length, they cannot represent a set of lips (i.e. upper and lower
lips).  If you are supposing that we have one lip on view in the
photograph, perhaps the upper lip, terminating along the right edge of the
scale rows, then these are multiple rows of enlarged lip scales (unlike the
single row of enlarged scales present on the lips of snakes and other
living reptiles) and the lower lip would either have only small bumpy
tubercles ( for this is the skin texture directly adjacent to the enlarged
scale rows) or the enlarged lower lip scales must be hidden from view
underneath the enlarged scales of specimen PVPH-126.

I am not endorsing your interpretation, but, as the authors say, we don't
really know what part of the body we are seeing.  Chiappe et al. do point
out that -- assuming the authors' hypothetical placement of these scales is
correct -- these titanosaurs would not have sported the keratinous dorsal
spikes found associated with a diplodocid specimen (see _Skin_ in Currie
and Padian's _Encyclopedia of Dinosaurs_). 

Dann Pigdon <dannj@alphalink.com.au> writes:
"If the embryos are those of titanosaurs, can the elusive shape of an
adult's skull be inferred from them, perhaps by looking at the growth
patterns of better known sauropods and extrapolating the growth of the
skull?  I am under the impression that there are no titanosaur skulls known
(which in itself may not be correct on my part)."

Until recently, titanosaur skulls were known from only fragmentary remains.
 In 1997, Chatterjee and Rudra reported finding a _Titanosaurus indricus_
braincase.  In 1996, Dr. Rudolfo Coria and Dr. David Gillette recovered a
nearly complete titanosaur skeleton which included a skull from Rincon de
los Sauces, Argentina.  The specimen was first discovered by Ruben
Martinez.  

Quoting Thom Holmes' account in Dino Times, January 1997, Volume 7, Number
1:
"The skull itself was still in preparation at the time of this writing. 
Coria described it for _Dino Times_ readers as being "pyramidal in shape,
with a wide skull back, narrow snout and fragile jaws.  It is really very
small when compared with the whole body.  I mean, _surprisingly_ small!" 
The skull is only about 12 inches (30 centimeters) long, compared to a body
length of about 48 feet(14.5 meters)!"

Holmes goes on to say:
"A 1996 expedition to Madagascar led by David Krause and including Peter
Dodson, Cathy Forster, and Scott Sampson also discovered a remarkably
complete titanosaur skull.  Our once paltry knowledge of titanosaurs is
about to grow immensely because of these two discoveries."

Luckily, you can see a nice photograph of the Patagonian titanosaur skull
on page 130 of the following article:
Shreeve, James, _Uncovering Patagonia's Lost World_, _National Geographic_,
December 1997, pp. 120-137.

The _Nature_ article (Volume 396, 258-261: _Sauropod dinosaur embryos from
the Late Cretaceous of Patagonia_) describes the fossilized remains of the
titanosaur embryos, which are still in preparation.  Only shafts of
postcranial elements have been recovered thus far (and these have been
described as flakes of bone), and "few cranial elements are easily
identifiable from a mass of diagenetically fused bone."  None-the-less,
there are 32 teeth associated with one specimen, which are described as 2.0
mm long, "pencil-like," and bearing the distinctive chisel-like morphology
of titanosaur teeth.  One tooth shows a wear facet.  A postorbital,
portions of the skull roof, and an interorbital bar are mentioned. 
Luckily, (as the previous paragraphs make obvious) we need not rely on
these few cranial embryo bits to establish the look of adult titanosaur
skulls!      

-- Ralph Miller III     gbabcock@best.com