''Sphaerovum'' is an

oogenus 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 ...

dinosaur egg 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 bec ...

that has only been discovered in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

History

''Sphaerovum'' was first described, along with '' Tacuarembovum'', in

1980 Events January * January 4 – U.S. President Jimmy Carter proclaims a grain embargo against the USSR with the support of the European Commission. * January 6 – Global Positioning System time epoch begins at 00:00 UTC. * January 9 – ...

by paleontologist Alvaro Mones, following their discovery at the Asencio Formation in

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

. This was one of the first discoveries of fossil dinosaur eggs in South America.Mones, A. (1980) "Nuevos elementos de la paleoherpetofauna del Uruguay (Crocodilia y Dinosauria)." ''Actas II Congreso Argentino de Paleontologia y Bioestratigrafia y I Congreso Latinoamericano, Buenos Aires'' 1:265-277 (in Spanish)

Distribution

Fossils of ''Sphaerovum'' and ''Sphaerovum''-like eggs are known from the Puerto Yeruá,

Allen Allen, Allen's or Allens may refer to: Buildings * Allen Arena, an indoor arena at Lipscomb University in Nashville, Tennessee * Allen Center, a skyscraper complex in downtown Houston, Texas * Allen Fieldhouse, an indoor sports arena on the Univer ...

and Colorado Formations in Argentina and the

Guichón Guichón is a small city in the Paysandú Department of western Uruguay. Geography It is located on Route 90, west of its intersection with Route 4 and east of its intersection with Route 25. History On 15 June 1907, it was declared "Pueblo" ( ...

and Asencio Formations of Uruguay. They are always found in

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

- or

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

-aged rocks, leading to their use as

index fossil Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock Stratum, strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictiona ...

Description

''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. The type specimen of ''Sphaerovum erbeni'' is too

silicified In geology, petrifaction or petrification () is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. Petrified wood typifies this proce ...

to make out its microstructure, however many specimens of South American fossil eggs showing superficial similarities to ''Sphaerovum'' have been found. 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.Carpenter, K. (1999) Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past). Indiana University Press, Bloomington, Indiana. p. 144 The high density of pores on the eggshell surface suggests that these eggs were laid in a humid environment. At the Mercedes Formation, ''Sphaerovum''-like eggs were found in large, closely packed groups indicating that they were buried in a shallow pit.

Classification

Due to their poor preservation, classification of ''Sphaerovum'' has proven difficult.Simón, M.E., (2006) "Cáscaras de huevos de dinosaurios de la Formación Allen (Campaniano e Maastrichtiano), en Salitral Moreno, provincia de Río Negro, Argentina." ''

Ameghiniana ''Ameghiniana'' is a peer-reviewed scientific journal covering palaeontology published by the Asociación Paleontológica Argentina. It is named after the 19th century Italian Argentine palaeontologist Florentino Ameghino. The discovery of many di ...

'' 43: 513e528

/ref>

Parataxonomy

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

specimen of ''Sphaerovum'' is heavily

, making the eggshell structure unrecognizable and assignment to any

oofamily 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 ...

difficult.Faccio, G. (1994). "Dinosaurian eggs from the Upper Cretaceous of Uruguay." in ''Dinosaur eggs and babies,'' Edited by Kenneth Carpenter, Karl F. Hirsch, John R. Cambridge University Press. pp. 47-55. 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 Faveoloolithidae is an oofamily of dinosaur eggs. It contains '' Faveoloolithus'', '' Hemifaveoloolithus'', ''Parafaveoloolithus'', and probably '' Sphaerovum''. However, unlike the other Faveoloolthids, ''Sphaerovum'' has compactituberculate or ...

, supporting the referral of ''Sphaerovum'' to that oofamily.Soto, M., Perea, D., and Cambiaso, A.V. (2012)
First sauropod (Dinosauria: Saurischia) remains from the Guichón Formation, Late Cretaceous of Uruguay
''Journal of South American Earth Sciences'' 33(1):68-79. DOI: 10.1016/j.jsames.2011.08.003Casadío, S., Manera, T., Parras, A., & Montalvo, C. I. (2002). "Dinosaur eggs (Faveloolithidae) from the Upper Cretaceous of the Colorado Basin, La Pampa Province, Argentina". ''Ameghiniana,'' 39(3), 285-293. However, it is occasionally considered to be a MegaloolithidCarpenter, K. (1999) ''Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past).'' Indiana University Press, Bloomington, Indiana. p. 272 on the basis of its ornamentation.Batista, A. (2012).
Análisis morfológico y sistemático de Tacuarembovum oblongum Mones 1980 y otras ooformas similares (Dinosauria), cretácico tardío? de Uruguay: implicancias.
Graduate Thesis for Universidad de la República (Uruguay).

Parentage

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

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still th ...

s. This would be consistent with the fact that titanosaurs were extremely common in the

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

of South America. Also, some eggshell fragments tentatively assigned to ''Sphaerovum'' were found loosely associated with the remains of a

Saltasaurid Saltasauridae (named after the Salta region of Argentina where they were first found) is a family of armored herbivorous sauropods from the Upper Cretaceous. They are known from fossils found in South America, Asia, North America, and Europe. Th ...

titanosaur at the

Guichón 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.Weishampel et al., 2004, pp.517-607 Description The Guichón F ...

in Uruguay.

References

{{Reflist, 2 Dinosaur reproduction Egg fossils Cretaceous Uruguay Fossils of Uruguay Fossil parataxa described in 1980