| Incognitoolithus Temporal range: | |
|---|---|
Egg fossil classification  | |
| Basic shell type: | Ornithoid |
| Morphotype: | Ornithoid-ratite |
| Oofamily: | † Medioolithidae |
| Oogenus: | † Incognitoolithus Hirsch, Kihm & Zelenitsky, 1997 |
| Oospecies | |
| |
Incognitoolithus is an oogenus of medioolithid fossil bird egg. It is notable for bearing evidence of predation, possibly from a bird pecking the eggshell. [1]
Incognitoolithus fragments are found at two localities in the DeBeque Formation in Garfield County, Colorado. Both localities are dated to the Early Eocene. [1]
Eggshell fragments of Incognitoolithus were discovered in 1977 and 1979 during two separate field seasons. The oospecies I. ramotubulus was first described in 1997 by Karl Hirsch, Allen Kihm and Darla Zelenitsky. [1]
I. ramotubulus is known from over 200 eggshell fragments which may represent a single disintegrated egg. When complete, the egg is estimated to have been 10–12 cm (3.9–4.7 in) long and 7.5–9 cm (3.0–3.5 in), making it significantly larger than the next largest known Eocene bird egg in North America, which measured only 6.4 x 8.9 cm. The eggshell is 1.27–1.43 mm thick and consists of two structural layers, unlike most modern ratite eggs (which have a third layer, the external layer). The outer layer, called the continuous layer, is three times the thickness of the inner layer (the mammillary layer). [1] It is one of the few fossil eggs to have only two layers and a smooth eggshell. [2]
Incognitoolithus has a distinctive pore system. It has both branching and unbranching pores. The openings of these pores on the surface of the eggshell matches the "aepyornithid" type: Pores open in small pits or in grooves which may accommodate multiple pore openings. [1]
The pore arrangement and structure of Incognitoolithus is similar to that of Aepyornis . [3] The microstructure and lack of ornamentation are similar to modern ratite eggs. However, since no embryonic remains or parental remains were found with Incognitoolithus, it is impossible to infer what kind of bird laid the eggs. [1]
Multiple fragments of Incognitoolithus have been found with holes interpreted as peck marks. While it is possible that these were made by a parent assisting the hatching, this behavior is very rare in modern birds. More likely, they are the result of predation. Experiments on modern chicken eggs by Hirsch et al. in 1997 found that Incognitoolithus's holes are most consistent with those from a bird's peck. However, the dynamics of a thick eggshell like I. ramotubulus differ from those of chicken eggs, so the possibility that the holes are tooth marks of a mammal or reptile cannot be ruled out. [1]
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.
Dinosaur reproduction shows correlation with archosaur physiology, with newborns hatching from eggs that were laid in nests. Dinosaurs did not nurture their offspring as mammals typically do, and because dinosaurs did not nurse, it is likely that most dinosaurs were capable of surviving on their own after hatching. Although, parental care may have been required for some dinosaur species, as shown by fossil evidence. Dinosaur reproduction also required a mate; evidence of sexual dimorphism and courting displays have been found from fossil scrapings in sandstone and feathers on dinosaurs that lacked flight.
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.
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.
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.
Continuoolithus is an oogenus of dinosaur egg found in the late Cretaceous of North America. It is most commonly known from the late Campanian of Alberta and Montana, but specimens have also been found dating to the older Santonian and the younger Maastrichtian. It was laid by an unknown type of theropod. These small eggs are similar to the eggs of oviraptorid dinosaurs, but have a distinctive type of ornamentation.
Ageroolithus is an oogenus of dinosaur egg. It may have been laid by a theropod.
Dispersituberoolithus is an oogenus of fossil egg, which may have been laid by a bird or non-avian theropod.
Megaloolithidae is an oofamily of fossil egg of the Dinosauroid-spherulitic morphotype. They probably are the eggs of sauropods.
Egg paleopathology is the study of evidence for illness, injury, and deformity in fossilized eggs. A variety of pathological conditions afflicting eggs have been documented in the fossil record. Examples include eggshell of abnormal thickness and fossil eggs with multiple layers of eggshell. The identification of egg paleopathologies is complicated by the fact that even healthy eggs can be modified during or after fossilization. Paleontologists can use techniques like cathodoluminescence or thin sectioning to identify true paleopathologies in fossil eggs. Despite the diversity of paleopathologies known from fossil eggs, the vast majority of conditions known to afflict modern eggs have not yet been seen among fossils.
The DeBeque Formation is a geologic formation in Colorado's Piceance Basin, preserving fossils which date back to the Late Paleocene to Early Eocene period (Clarkforkian to Wasatchian in the NALMA classification. Examples of these fossils are held in the University of Colorado Museum of Natural History.
Coralloidoolithus is an oogenus of dinosaur egg from the Tiantai Basin in Zhejiang Province, containing a single known oospecies C. shizuiwanensis. Formerly, it was classified in the oogenus Paraspheroolithus; however, it was considered sufficiently different to be classified in its own genus. C. shizuiwanensis is similar to Stalicoolithus, leading to their classification in the same family, Stalicoolithidae.
Hemifaveoloolithus is an oogenus of fossil dinosaur egg from the Tiantai basin in Zhejiang Province, China. It is a faveoloolithid, having spherical eggs roughly 13 cm in diameter. The shell is distinctive for being composed of four or five superimposed layers of shell units, and the honeycomb-like arrangement of pore canals.
Tipoolithus is an oogenus of fossil egg native to the Irbzer Formation in Morocco. Its classification is uncertain, but it most closely resembles Laevisoolithids, and like members of that oofamily, it was laid by an enantiornithine bird or small theropod.
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.
Medioolithus is an oogenus of fossil egg laid by a paleognath.
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.
Trigonoolithus is an oogenus of dinosaur egg, representing a basal prismatoolithid. Its eggshell, like avian eggs, is composed of three structural layers, but cladistic analysis suggests that its parent was a non-avian theropod.
Gobioolithus is an oogenus of fossil bird egg native to Mongolia. They are small, smooth-shelled, and elongated eggs that were first discovered in the 1960s and early 70s during a series of fossil-hunting expeditions in the Gobi desert. Two oospecies have been described: Gobioolithus minor and G. major. The eggs were probably laid in colonial nesting sites on the banks of rivers and lakes.
Nanhsiungoolithus is an oogenus of dinosaur egg from the late Cretaceous of China. It belongs to the oofamily Elongatoolithidae, which means that it was probably laid by an oviraptorosaur, though so far no skeletal remains have been discovered in association with Nanhsiungoolithus. The oogenus contains only a single described oospecies, N. chuetienensis. It is fairly rare, only being know from two partially preserved nests and a few eggshell fragments.
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