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Re: Possible Tyrannosaurid nesting behaviour
"no go" wrote
> Is there any way to determine the possible nesting
> 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
"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
2. The number of eggs in a tyrannosaurid nest was probably
smaller than in other known dinosaur nests, with an average of a dozen
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
I hope that you found a few answers ...
Gunter Van Acker