The pterosaur in the egg: a new report

[david peters <davidrpeters@earthlink.net>]

The latest issue, #67, of the Prehistoric Times (www.prehistorictimes.com) has 
published new tracings of the bones within IVPP V13758, the Chinese pterosaur 
in the egg. I eagerly encourage anyone with an interest in the subject to check 
it out.

Originally the specimen was purported to be the embryo of an unidentified 
higher ornithocheirid, due in large part to the length of manual 4.1 which 
reaches the elbow when folded. And then thereâ??s the apparent lack of a tail. 
The originally identified â??mandibleâ?? is way, way too short to be that of an 
ornithocheirid, but the brevity was ascribed to its ontogenetic age.

As it turns out only two known ornithocheirids have this long first wing 
phalanx trait, Anhanguera and an unnamed istiodactylid, SMNS 1136 PAL, although 
many more, known from skulls alone and some with broken wings, probably share 
the character. It is not a primitive trait, however. Haopterus, Arthurdactylus 
and Brasileodactylus do not have such an elongated m4.1.

Two other clades share this wing finger character, Campylognathoides + 
Rhamphorhynchus and the Anurognathinae, aka the higher Anurognathids. We can 
rule out the former because a big tail would have been hard to miss. On the 
other hand, itâ??s hard to find the tail on Anurognathids, so this clade should 
not be ruled out. And anurognathids were contemporaneous.

As youâ??ll see from the tracings, the â??mandible in ventral viewâ?? 
identified by the Chinese is actually a V-shaped intersection of the ascending 
processes of the premaxilla and maxilla. Other mistakes followed. I found a 
complete skull, mandibles with teeth, palate, occiput and sclerotic ring 
followed by a complete skeleton down to the fingers and toes. I did not bother 
with trying to sort out the ribs. However, I did find a typical anurognathid 
tail.

A reconstruction shows the specimen is about the size of Dendrorhynchoides and 
Anurognathus. PAUP says it falls somewhere in between. Notably the ascending 
process of the premaxilla is at right angles to the jawline and the anterior 
premaxilla tooth is the largest inf the set. These characters are not found in 
other anurognathids. Considering the circumstances in which the little 
pterosaur was found, it seems reasonable to ascribe the modifications to the 
premaxilla as part of an egg-breaking apparatus. As an aside, but on a similar 
note, Jeholopterus, the vampire pterosaur, has the most robust limbs of any 
anurognathid and I ascribed this modification to its hypothetical habit of 
riding bucking dinosaurs to which it has adhered. On the opposite end of the 
scale, the new egg-breaking anurognathid has the smallest antebrachium and 
weakest legs and feet of all. Perhaps these can be ascribed to the sedentary 
nature of its prey, dinosaur eggs. It also seems reasonable that egg-breakers
 might descend from insect-eaters attracted to the insects that were attracted 
to broken eggs and the rich nutrients inside. Unguarded dinosaur eggs would 
make an easy meal for any flying creature if only somehow the eggshell could be 
broken. This little pterosaur apparently found a way.

The new pterosaur fits neatly into a large cladogram. Using 178 characters and 
more than 100 taxa, a single tree cladogram has 1751 steps. The new pterosaur 
adds only eight more, chiefly in the extremity ratios, for a total of 1759.

The text of the popular article and figures can be viewed on the Web at 
pterosaurinfo.com. The main page will take you there. For the original 
published and copyrighted article and photos, see Nature.com. Both Nature and 
Science were offered the anurognathid manuscript and both declined. The 
Prehistoric Times offered the most timely publishing schedule with a minimum of 
headaches. And it has a great circulation.

Of course this is only the first challenge to the pterosaur egg theory. Iâ??ve 
produced a more detailed tracing of the specimen than was previously offered. 
If anyone wants to oppose the new hypothesis, offer a defense or  specifically 
show where the drawing is in error, it would seem to be good science to produce 
another tracing of equal or better detail showing the error(s). I look forward 
to some good science.

As I have mentioned earlier on the list, there may be pterosaur eggs out there, 
but for now, this one does not seem to be one of them. If Luis Chiappe has an 
embryo Pterodaustro, it could not be mistaken for any sort of anurognathid. I 
await my first peek at it.

For the record, it would appear that all descendants of Boreopricea and 
Jesairosaurus practised viviparity. That includes drepanosaurids, 
tanystropheids and pterosaurs. Both B. and J. appear to have been subjects of a 
size squeeze following descent from something like Protorosaurus, and you all 
know what can happen following a size squeeze.

Remember to question and test all reports, including this one. 

More later,

David Peters
St. Louis