Re: Possible Tyrannosaurid nesting behaviour

["Gunter" <guntervanacker.mesozoic@pi.be>]

 

"no go" wrote

 

> Is there any way to determine the possible nesting behaviour of
> Tyrannosaurids like Tyrannosaurus? Have we found any evidence of their eggs
> (I have heard there has been fragmentary and ambigious finds on
> Tyrannosaurid eggs, namely from one eposide of Discovery's Ultimate T.rex
> where one paleontologist holds up two rather large but badly crushed
> dinosaur eggs from the late KT with supposed Tyrannosaurus fossils within.).

First this; there is no published evidence that links a known dinosaur egg type to a known tyrannosaurid genus.

 

The eggs mentioned above, probably belong to the oogenus Macroelongatoolithus, this oogenus includes the largest known dinosaur eggs (average length up to 45cm/18inch), the best known oospecies being Macroelongatoolithus xixiaensis (Li et al., 1995). M. xixiaensis was discovered in Henan province, China. Their age can only be estimated as being "Cretaceous", so there remains a possibility that they are recent enough to belong to a large tyrannosaurid like Tarbosaurus (Campanian-Maastrichtian, some 73 to 68 MYA). However, M. xixiaensis is most likely considerably older, possibly even late Early Cretaceous (Albian, some 105 MYA). The case for an Early Cretaceous age is strengthened by following paper;

 

"First Record of Elongatoolithid Theropod Eggshell from North America: The Asian Oogenus Macroelongatoolithus from the Lower Cretaceous of Utah"; Zelenitsky, Carpenter & Currie; Journal of Vertebrate Paleontology 20, p.130-138, March 2000

 

In this paper, the authors describe dinosaur eggshell from (North American) Early Cretaceous localities incl. the Cedar Mountain Formation (Utah); the eggshell is identical to M. xixiaensis from China, they even refer the fossils to this oogenus. Since the names of dinosaur eggshell have their own parataxonomy, this referal is fine, but it's safe to assume that the North American and Chinese Macroelongatoolithus eggs were not produced by dinosaurian forms that fit into the same genus (genus here being traditional dinosaur taxonomy, based on skeletal evidence).

 

All this only tells us that there were theropods from the late Early Cretaceous to (possibly) Late Cretaceous (105 to ?70 MYA) that were large enough to produce these Macroelongatoolithid eggs.

These large theropods were rather derived, and probably even coelurosaurian; oviraptorids and dromaeosaurids also produced (smaller) eggs that fit into the same oofamily. We also know that more basal theropods (like allosaurs) produced a different egg type (Preprismatoolithus sp. for the Portuguese allosauroid Lourinhanosaurus, and probably Allosaurus fragilis with P. coloradensis).

We don't have evidence that the large Asian Macroelongatoolithus eggs were produced by tyrannosaurids, since there are no associated embryonic remains (the "Baby Louie" specimen featured by National Geographic doesn't give us answers). The North American Macroelongatoolithus eggshell makes a referal of this eggshell to Tyrannosauridae even more problematic, the North American eggshell probably belongs to a large deinonychosaur (Utahraptor-grade) or even an oviraptorosaur (large Microvenator type), it's unlikely that there were (large) tyrannosaurids in the Cedar Mountain predator fauna, that was dominated by the allosaurid Acrocanthosaurus and deinonychosaurs like Utahraptor and the smaller Deinonychus.

 

So, since we don't have definite tyrannosaurid eggs or embryos, there is also no evidence of their nesting behaviour.

 

My guess is (for what it's worth);

1. If and when we find associated tyrannosaurid eggshell and embryos, it will (yes) probably closely resemble the macroelongatoolithid oogenus

2. The number of eggs in a tyrannosaurid nest was probably smaller than in other known dinosaur nests, with an average of a dozen eggs

3. We can be rather certain that tyrannosaurids did show parental care; we have evidence for several (distantly related) other dinosaur clades, and tyrannosaurid hatchlings would have needed parental protection from all those dromaeosaurids and troodontids that were present in tyrannosaurid-dominated fauna's.

 

 

I hope that you found a few answers ...

 

 

Gunter Van Acker