| Sphaerovum Temporal range: | |
|---|---|
Egg fossil classification  | |
| Basic shell type: | † Dinosauroid-spherulitic |
| Oofamily: | † Faveoloolithidae |
| Oogenus: | † Sphaerovum Mones, 1980 |
| Oospecies | |
| |
Sphaerovum is an oogenus of dinosaur egg that has only been discovered in South America.
Sphaerovum was first described, along with Tacuarembovum , in 1980 by paleontologist Álvaro Mones, following their discovery at the Asencio Formation in Uruguay. This was one of the first discoveries of fossil dinosaur eggs in South America. [1]
Fossils of Sphaerovum and Sphaerovum-like eggs are known from the Puerto Yeruá, Allen and Colorado Formations in Argentina and the Guichón and Asencio Formations of Uruguay. [2] They are always found in Campanian- or Maastrichtian-aged rocks, leading to their use as index fossils. [3]
Sphaerovum eggs are 15-20 cm in diameter, with a shell between 4.2 and 5.5 mm thick. The ornamentation is compactituberculate, i.e. the eggshell is covered with dome-like nodes formed by the tops of the shell units. [2] [1] The type specimen of Sphaerovum erbeni is too silicified to make out its microstructure, however many specimens of South American fossil eggs showing superficial similarities to Sphaerovum have been found. [4] These specimens are resemble other Faveoloolithids in their filispherulitic structure and a multicanaliculate pore system. Unlike Faveoloolithids, however, Sphaerovum has compactituberculate ornamentation more similar to Megaloolithids. [3] [5] The high density of pores on the eggshell surface suggests that these eggs were laid in a humid environment. [3]
At the Mercedes Formation, Sphaerovum-like eggs were found in large, closely packed groups indicating that they were buried in a shallow pit. [6]
Due to their poor preservation, classification of Sphaerovum has proven difficult. [4]
The holotype specimen of Sphaerovum is heavily silicified, making the eggshell structure unrecognizable and assignment to any oofamily difficult. [6] [4] However, other specimens which have strong superficial resemblance to Sphaerovum have been found in Uruguay and Argentina. These specimens show morphology similar to members of Faveoloolithidae, supporting the referral of Sphaerovum to that oofamily. [2] [3] However, it is occasionally considered to be a Megaloolithid [7] on the basis of its ornamentation. [8]
It is unknown what kind of dinosaur laid Sphaerovum eggs because embryonic remains have not been found. However, they have long been considered to be the eggs of titanosaurs. This would be consistent with the fact that titanosaurs were extremely common in the Upper Cretaceous of South America. Also, some eggshell fragments tentatively assigned to Sphaerovum were found loosely associated with the remains of a Saltasaurid titanosaur at the Guichón Formation in Uruguay. [2]
Andesaurus is a genus of basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America. Like most sauropods, belonging to one of the largest animals ever to walk the Earth, it would have had a small head on the end of a long neck and an equally long tail.
Dinosaur eggs are the organic vessels in which a dinosaur embryo develops. When the first scientifically documented remains of non-avian dinosaurs were being described in England during the 1820s, it was presumed that dinosaurs had laid eggs because they were reptiles. In 1859, the first scientifically documented dinosaur egg fossils were discovered in France by Jean-Jacques Poech, although they were mistaken for giant bird eggs.
The Asencio Formation is a geological formation in the Paraná Basin of southwestern Uruguay whose strata date back to the Late Cretaceous (Campanian-Maastrichtian). Dinosaur remains are among the fossils that have been recovered from the formation.
The Guichón Formation is a Late Cretaceous geologic formation of the Paysandú Group in Uruguay. Dinosaur remains are among the fossils that have been recovered from the formation.
The Puerto Yeruá Formation is a Late Cretaceous geologic formation in the Paraná Basin, pertaining to Entre Ríos Province, Argentina. Dinosaur remains are among the fossils that have been recovered from the formation, as well as egg fragments and fossilized wood.
The Mercedes Formation is a Late Cretaceous geologic formation of the Norte Basin in Uruguay. Fossil dinosaur eggs have been reported from the formation. The formation that reaches a thickness of about 100 metres (330 ft), overlies the Guichón Formation and is overlain by the Asencio Formation.
Dictyoolithus is an oogenus of dinosaur egg from the Cretaceous of China. It is notable for having over five superimposed layers of eggshell units. Possibly, it was laid by megalosauroid dinosaurs.
Cairanoolithus is an oogenus of dinosaur egg which is found in Southwestern Europe. The eggs are large and spherical. Their outer surface is either smooth, or covered with a subdued pattern of ridges interspersed with pits and grooves. Multiple fossil egg clutches are known but the nest structure is unclear.
Macroelongatoolithus is an oogenus of large theropod dinosaur eggs, representing the eggs of giant caenagnathid oviraptorosaurs. They are known from Asia and from North America. Historically, several oospecies have been assigned to Macroelongatoolithus, however they are all now considered to be a single oospecies: M. carlylensis.
Macroolithus is an oogenus of dinosaur egg belonging to the oofamily Elongatoolithidae. The type oospecies, M. rugustus, was originally described under the now-defunct oogenus name Oolithes. Three other oospecies are known: M. yaotunensis, M. mutabilis, and M. lashuyuanensis. They are relatively large, elongated eggs with a two-layered eggshell. Their nests consist of large, concentric rings of paired eggs. There is evidence of blue-green pigmentation in its shell, which may have helped camouflage the nests.
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.
Paraelongatoolithus is a late Cretaceous oogenus of Chinese fossil egg, classified in the oofamily Elongatoolithidae, which represents the eggs of oviraptorosaurs.
Parvoblongoolithus is an oogenus of fossil dinosaur egg whose small size and unusual shape suggest the possibility that it is a dwarf egg.
Tacuarembovum is an oogenus of fossil egg from the Late Cretaceous Asencio Formation of Uruguay. It represents an Elongatoolithid, and pending future analysis may be found to be synonymous with another oospecies.
Mycomorphoolithus is an oogenus of fossil eggs found in Spain and England. They possibly represent eggshells of non-eusuchian crocodylomorphs, and are similar to, but not part of, the Krokolithidae.
Guegoolithus is an oogenus of fossil egg from the early Cretaceous of Spain. It is classified in the oofamily Spheroolithidae, and was probably laid by an ornithopod dinosaur.
Tubercuoolithus is an oogenus of dinosaur egg from the early Campanian of Montana.
Nipponoolithus is an oogenus of fossil egg native to Japan. It is one of the smallest known dinosaur eggs, and was probably laid by some kind of non-avian maniraptor.
Faveoloolithidae is an oofamily of dinosaur eggs. It contains Faveoloolithus, Hemifaveoloolithus, Parafaveoloolithus, and probably Sphaerovum. However, unlike the other Faveoloolthids, Sphaerovum has compactituberculate ornamentation more similar to megaloolithids. Like Dictyoolithidae, the membrane and the calcareous part of the eggshell formed simultaneously instead of forming the membrane before the calcareous like modern birds.
