''Dispersituberoolithus'' is an oogenus of

fossil egg Egg fossils are the fossilized remains of eggs laid by ancient animals. As evidence of the physiological processes of an animal, egg fossils are considered a type of trace fossil. Under rare circumstances a fossil egg may preserve the remains of t ...

, which may have been laid by a bird or non-avian theropod.D. K. Zelenitsky, L. V. Hills, and P. J. Currie. (1996). Parataxonomic classification of ornithoid eggshell fragments from the Oldman Formation (Judith River Group; Upper Cretaceous), southern Alberta. Canadian Journal of Earth Sciences 33:1655-1667

Discovery

The eggshell fragments now classified as ''Dispersituberoolithus'' were collected between 1987 and 1995 by field crews working for the

Royal Tyrrell Museum of Palaeontology The Royal Tyrrell Museum of Palaeontology (RTMP, and often referred to as the Royal Tyrrell Museum) is a palaeontology museum and research facility in Drumheller, Alberta, Canada. The museum was named in honour of Joseph Burr Tyrrell, and is situ ...

. They were first described in 1996 by D.K. Zelenitsky and L.V. Hills, two paleontologists in Department of Geology and Geophysics at the University of Calgary, together with P.J. Currie from the Royal Tyrrell Museum.

Distribution

''Dispersituberoolithus exilis'' is known from several eggshell fragments collected at Little Diablo's Hill at Devil's Coulee, southern Alberta. This is part of Oldman Formation, which is dated to the late Campanian.

Description

''Dispersituberoolithus'' is one of the few fossil eggs of the ornithoid-prismatic morphotype. The outer surface of its eggshell exhibits what is called dispersituberculate ornamentation, i.e. the shell is covered with randomly distributed nodes. ''Dispersituberoolithus'' was named for this pattern. Its shell is 0.26 to 0.28 mm thick, and is made up of three structural layers. The innermost layer, called the mammillary layer, is half the thickness of the continuous layer and twice the thickness of the external zone. The boundary between the continuous and the mammillary layers exhibits a squamatic ultrastructure. It has an angusticanaliculate pore system, which means that its pores are long, narrow, and straight.

Parataxonomy

''Dispersituberoolithus'' is classified in the ornithoid-prismatic morphotype (also called the neognathous morphotype). It has not been assigned to any known oofamily. Only one oospecies has been named: ''D. exilis''.

Parentage

Since no embryos of ''D. exilis'' are known, it is impossible to determine with certainty whether it was laid by a bird or a non-avian theropod. Zelenitsky '' et al.'' (1996) believed it to be the eggs of a bird because its eggshell has an external zone. However the sculpted outer surface of ''Dispersituberoolithus'' shell is unlike bird eggs, and since some non-avian dinosaurs are known to have a three-layered eggshell, the presence or absence of the external zone cannot be reliably used to distinguish avian eggs from non-avian.

References

{{Taxonbar, from=Q5282587 Dinosaur reproduction Fossil parataxa described in 1996