| Montanoolithus Temporal range: | |
|---|---|
Egg fossil classification  | |
| Basic shell type: | Ornithoid |
| Morphotype: | Ornithoid-ratite |
| Oofamily: | † Montanoolithidae Zelenitsky and Therrien, 2008 |
| Oogenus: | † Montanoolithus Zelenitsky and Therrien, 2008 |
| Oospecies | |
Montanoolithus is an oogenus of fossil egg found in Montana and Alberta. They were probably laid by a dromaeosaur or a caenagnathid. [1]
The type specimen of Montanoolithus was found in the Two Medicine Formation on the Blackfeet Reservation. Other specimens are known from the Oldman Formation in Alberta. All Montanoolithus fossils yet discovered date to the Late Cretaceous. [1]
Montanoolithus strongorum is known from several eggshell fragments and a partial egg clutch (with five preserved eggs). When complete, this clutch likely had at least twelve eggs, arrayed in pairs in a ring, similar to the Asian oviraptorid clutches. The most complete egg is elongated, measuring 125 mm (4.9 in) long by 60 mm (2.4 in) wide, and slightly asymmetrical. The outer surface of its shell is ornamented with anastomosing ridges. [1]
Montanoolithus's eggshell ranges from 0.70 to 0.85 mm thick, and is composed of two layers. The outer layer, called the columnar layer (or squamatic zone, so named because of the peculiar texture of the layer), [2] is twice as thick as the inner mammillary layer. [1] The two layers are divided by a gradual boundary. The mammillae (the cone-shaped structures in the mammillary layer which make up the base of each eggshell unit) are formed by wedge-shaped crystals. [1]
Cladistic analysis shows Montanoolithus to be maniraptoran eggs, more basal than troodontids, but more derived than oviraptorids. [1] [3] Maniraptorans are only represented at the Two Medicine formation by Troodon (whose eggs are already known), dromaeosaurs, and caenagnathids. Therefore, the parent of Montanoolithus was probably a dromaeosaur or a caenagnathid. [1]
The mother of the Montanoolithus eggs made a mound-shaped nest out of sand, and laid the eggs in a ring around the top. The nest was made from freshly deposited sand (perhaps near to a river), or in a poorly vegetated area. Even though no parent was found with the eggs, it is likely based on its identification as a maniraptoran that the eggs were incubated, since this behavior has been observed in both troodontids and oviraptorids. [1] The pairing of the eggs suggests that, like other maniraptorans, the egg-layer of Montanoolithus had two functioning oviducts which would each form an egg simultaneously. [1]
Montanoolithus is classified in its own oofamily, Montanoolithidae, which is related to the eggs of oviraptorids, troodontids, and birds. It contains a single oospecies: M. strongorum. [1]
Oviraptor is a genus of oviraptorid dinosaur that lived in Asia during the Late Cretaceous period. The first remains were collected from the Djadokhta Formation of Mongolia in 1923 during a paleontological expedition led by Roy Chapman Andrews, and in the following year the genus and type species Oviraptor philoceratops were named by Henry Fairfield Osborn. The genus name refers to the initial thought of egg-stealing habits, and the specific name was intended to reinforce this view indicating a preference over ceratopsian eggs. Despite the fact that numerous specimens have been referred to the genus, Oviraptor is only known from a single partial skeleton regarded as the holotype, as well as a nest of about fifteen eggs and several small fragments from a juvenile.
Byronosaurus is a genus of troodontid dinosaur from the Late Cretaceous Period of Mongolia.
Nemegtomaia is a genus of oviraptorid dinosaur from what is now Mongolia that lived in the Late Cretaceous Period, about 70 million years ago. The first specimen was found in 1996, and became the basis of the new genus and species N. barsboldi in 2004. The original genus name was Nemegtia, but this was changed to Nemegtomaia in 2005, as the former name was preoccupied. The first part of the generic name refers to the Nemegt Basin, where the animal was found, and the second part means "good mother", in reference to the fact that oviraptorids are known to have brooded their eggs. The specific name honours the palaeontologist Rinchen Barsbold. Two more specimens were found in 2007, one of which was found on top of a nest with eggs, but the dinosaur had received its genus name before it was found associated with eggs.
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Elongatoolithus is an oogenus of dinosaur eggs found in the Late Cretaceous formations of China and Mongolia. Like other elongatoolithids, they were laid by small theropods, and were cared for and incubated by their parents until hatching. They are often found in nests arranged in multiple layers of concentric rings. As its name suggests, Elongatoolithus was a highly elongated form of egg. It is historically significant for being among the first fossil eggs given a parataxonomic name.
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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 the once-developing embryo inside, in which case it also contains body fossils. A wide variety of different animal groups laid eggs that are now preserved in the fossil record beginning in the Paleozoic. Examples include invertebrates like ammonoids as well as vertebrates like fishes, possible amphibians, and reptiles. The latter group includes the many dinosaur eggs that have been recovered from Mesozoic strata. Since the organism responsible for laying any given egg fossil is frequently unknown, scientists classify eggs using a parallel system of taxonomy separate from but modeled after the Linnaean system. This "parataxonomy" is called veterovata.
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This timeline of oviraptorosaur research is a chronological listing of events in the history of paleontology focused on the oviraptorosaurs, a group of beaked, bird-like theropod dinosaurs. The early history of oviraptorosaur paleontology is characterized by taxonomic confusion due to the unusual characteristics of these dinosaurs. When initially described in 1924 Oviraptor itself was thought to be a member of the Ornithomimidae, popularly known as the "ostrich" dinosaurs, because both taxa share toothless beaks. Early caenagnathid oviraptorosaur discoveries like Caenagnathus itself were also incorrectly classified at the time, having been misidentified as birds.
Elongatoolithidae is an oofamily of fossil eggs, representing the eggs of oviraptorosaurs. They are known for their highly elongated shape. Elongatoolithids have been found in Europe, Asia, and both North and South America.
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