| Guegoolithus Temporal range: | |
|---|---|
Egg fossil classification  | |
| Basic shell type: | † Dinosauroid-spherulitic |
| Oofamily: | † Spheroolithidae |
| Oogenus: | † Guegoolithus Moreno-Azanza et al., 2014 |
| Oospecies | |
| |
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.
Guegoolithus is known from the Early Cretaceous of Spain. It is common in the Maestrazgo Basin, dating to the lower Barremian. Fossils have been found in the Blesa, El Castellar, Camarillas, and Mirambel Formations. [1] It has also been found at the slightly older El Hocajo, a part of the Cameros Basin which dates to the Valanginian or Hauterivian ages, up to 7 million years older than the Maestrazgo specimens. [2]
Guegoolithus is known from over 400 fossil eggshell fragments, but no complete eggs have been found. They are very thin for spheroolithids, ranging from 0.42 to 1.5 mm in thickness. [1] The wide range of eggshell thickness is partially due to erosion on the inner and outer surfaces of the fragments. [3] The size and shape of the complete egg is unknown. [1]
Like other types of dinosaur eggs, the shell of Guegoolithus is made up of tightly packed crystalline units. The shell is single-layered, but the shell units appear to have two distinct layers because they exhibit a radiating acicular crystal structure near the base (the inner edge of the eggshell), but form a tabular ultrastructure on the upper third of the eggshell. [2] The surface of the eggshell exhibits sagenotuberculate ornamentation (nodes and ridges forming a net-like pattern, with pits and grooves in between [4] ). It has a prolatocanaliculate pore system, similar to Spheroolithus , which means that the pores are irregularly shaped and vary in width along their length. Also like Spheroolithus, it has a prolatospherulitic morphotype, with eggshell units fused together and horizontal growth lines on the lower portion of the eggshell. Guegoolithus has much more prominent ornamentation that Spheroolithus, and a thinner eggshell than most Spheroolithus species. [1]
Guegoolithus was first discovered in 2000 by Spanish paleontologists Olga Amo-Sanjuán, José Ignacio Canudo, and Gloria Cuenca-Bescós, though it was described as an oospecies of Macroolithus . In 2008, a paper suggested that "M." turolensis be used as an index fossil for fossil sites in the Sistema Ibérico, because they are easily identifiable and always found in rocks of Hauterivian-Barremian age. [5] An analysis in 2014 by Miguel Moreno-Azanza, José Ignacio Canudo, and José Manuel Gasca found that in fact, "M." turolensis is not an elongatoolithid, but instead belongs in Spheroolithidae, and named a new oogenus for it: Guegoolithus. [1] In 2016, Moreno-Azanza and several of his colleagues reported the discovery of a new fossil site in La Rioja, Spain, which included eggs assigned to Guegoolithus. Since this site is somewhat older than the Barremian age of the previously reported Guegoolithus fossils, Moreno et al. rejected the idea of using them as index fossils. [2]
While it was previously considered an oospecies of Macroolithus in the oofamily Elongatoolithidae, Guegoolithus is now considered a spheroolithid because of the similarities of microstructure, ultrastructure, and ornamentation. It contains a single oospecies: G. turolensis. Unfortunately, relationships within Spheroolithidae are not well known because of the unclear definitions of Spheroolithus and Speroolithidae. [1]
Guegoolithus is classified as a spheroolithid, which would indicate it was laid by an ornithopod dinosaur. It is very similar to the eggs of Maiasaura peeblesorum and other hadrosaurs, but these were not common in Europe during the Early Cretaceous. G. turolensis is most likely laid by a closely related ornithopods. [1] Styracosterns (a clade of ornithopods that includes hadrosaurs and their close relatives) are, like G. turolensis, incredibly common in the lower Cretaceous of Spain. Given that fossils of Guegoolithus span a larger time period than is likely for a single species, the fossils probably represent many different styracostern species with structurally indistinguishable eggshells. Because Guegoolithus remained unchanged for upwards of 5 million years and it is very similar to the late Cretaceous spheroolithids, Moreno-Azanza et al. (2017) concluded that the nesting behavior of hadrosaurs and their close relatives remained unchanged for 80 million years. The eggshell structure is apparently designed to be easily broken from the inside, indicating that these dinosaurs were altricial. [6]
Its reclassification outside of Elongatoolithidae implies that no elongatoolithids are known from the early Cretaceous of Europe. However, elongatoolithids have been reported from the Late Cretaceous of France. [1]
The Camarillas Formation is a geological formation in the Teruel Province of Aragón, Spain whose strata date back to the Early Cretaceous. The sandstones, mudstones and conglomerates of the formation, that due to syn-sedimentary faulting varies greatly in thickness from 300 to 800 metres, were deposited in fluvial, deltaic and lacustrine environments.
The Blesa Formation is a geological formation in Teruel and La Rioja, Spain whose strata date back to the Barremian of the Early Cretaceous. Dinosaur remains as well as eggs are among the fossils that have been recovered from the formation. Along with the fragmentary anhanguerian pterosaur Iberodactylus. While the lower and upper parts of the formation were deposited in a continental setting, the middle portion of the formation is largely nearshore marine, with remains of plesiosaurs.
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.
Shixingoolithus is an oogenus of dinosaur egg from the Cretaceous of Nanxiong, China.
Protoceratopsidovum is an oogenus of dinosaur egg from Mongolia. Despite its name, it does not represent the eggs of a protoceratopsid, but rather the eggs of maniraptoran theropods.
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.
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.
Gideonmantellia is an extinct genus of basal ornithopod dinosaur known from the Early Cretaceous Camarillas Formation of Galve, Province of Teruel, Spain. It contains a single species, Gideonmantellia amosanjuanae.
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.
Prismatoolithidae is an oofamily of fossil eggs. They may have been laid by ornithopods or theropods.
Krokolithidae is an oofamily of fossil crocodylomorph eggs. The oogenus Mycomorphoolithus is closely related to the family, but not included in it.
Stalicoolithidae is an oofamily of fossil eggs.
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.
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.
Dictyoolithidae is an oofamily of dinosaur eggs which have a distinctive reticulate organization of their eggshell units. They are so far known only from Cretaceous formations in China.
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.
Spheroolithidae is an oofamily of dinosaur eggs. It contains Guegoolithus, Spheroolithus, and Paraspheroolithus. Like modern birds, the eggshell membrane formed before the calcareous part of the shell.
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