 | This article relies largely or entirely on a single source .(February 2017) |
| Polyclonoolithus | |
|---|---|
Egg fossil classification  | |
| Basic shell type: | † Dinosauroid-spherulitic |
| Oofamily: | † Polyclonoolithidae |
| Oogenus: | † Polyclonoolithus Xie et al., 2016 |
| Oospecies | |
| |
Polyclonoolithus is an oogenus of fossil dinosaur egg. It is from the Early Cretaceous of Gansu, China. They have distinctive, branching eggshell units, which may represent the original form of spheroolithids. [1]
Polyclonoolithus is known exclusively from Yangjiagou, a small town in Gansu. The only known fossil specimen is from the Lower Cretaceous Hekou Group, part of the larger Lanzhou-Minhe Basin. [1]
Dinosaur body fossils and ichnites are common at the Hekou Group, but fossilized eggs are rare. [1] The first fossil eggs found there were collected by Chinese Academy of Geological Sciences in Zhongpu in 2009, but were never formally described. In 2012, a team of paleontologists from the Gansu Geological Museum, the Institute of Vertebrate Paleontology and Paleoanthropology and the Institute of Geology once again discovered fossil eggs in the Lanzhou-Minhe Basin. In 2016, their discovery was described as a new oogenus and oospecies, Polyclonoolithus yangjiagouensis, by Chinese paleontologists Xie Jun-Fang, Zhang Shu-Kang, Jin Xing-Sheng, Li Da-Qing, and Zhou Ling-Qi. [1]
Polyclonoolithus is only known from one specimen: ZMNH M1849, an incomplete egg (made up of several fragments) housed in the Zhejiang Museum of Natural History. Due to the poor preservation, the size and shape of a complete egg are unknown, but Polyclonoolithus was likely less than 10 centimetres (3.9 in) in diameter. The eggshell ranges from 1.84 to 2.05 millimetres (0.072 to 0.081 in) in thickness. The cone layer has radiating structure and makes up roughly 1/7 the total width of the eggshell. [1]
Polyclonoolithus is distinctive for having branching shell units, with irregular pore canals between them. The branches of the eggshell units fuse together towards the outer surface of the shell. [1]
Polyclonoolithus is classified in its own oofamily, Polyclonoolithidae. Its branching eggshell units set it apart from all other oofamilies, except for Dendroolithidae, Dictyoolithidae, and Similifaveoloolithidae. It lacks the reticulate structure seen in dictyoolithids, and unlike similifaveoloolithids and dendroolithids, the eggshell units vary in thickness. It furthermore differs from dendroolithids in that the eggshell units are not totally fused together at the outer surface of the eggshell, however this could only be due to erosion. [1]
There is also some similarity between the branching eggshell units of Polyclonoolithus to the superimposed eggshell units found in Spheroolithidae, leading to the hypothesis by Xie et al. that the shell units of polyclonoolithids may represent a primitive form of those found in spheroolithids. [1]
Polyclonoolithus contains only a single oospecies: P. yangjiagouensis. [1]
The Hekou Group is a geological group in Gansu Province, China. It is Early Cretaceous in age. Dinosaur body fossils have also been recovered from the Hekou Group, including the iguanodont Lanzhousaurus and the titanosaurs Daxiatitan, Huanghetitan and Yongjinglong, and the nodosaur Taohelong. Fossil eggs are rare, but one oogenus, Polyclonoolithus, was discovered in the Hekou Group. The group spans the Valanginian to Albian and can be subdivided into four formations. Fossil pterosaur tracks have been recovered.
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.
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.
Shixingoolithus is an oogenus of dinosaur egg from the Cretaceous of Nanxiong, China.
Macroelongatoolithus is an oogenus of large, fossil theropod eggs. They are known from Asia and from North America.
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.
Phaceloolithus is an oogenus of dinosaur egg found in the Fenshui'ao Formation of the Dongting Basin of the Hunan Province of China. The eggs have a subspherical shape, measuring up to 168 mm on the long axis, and having a very thin shell.
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.
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.
Stalicoolithidae is an oofamily of fossil eggs.
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.
Paradictyoolithus is an oogenus of dictyoolithid dinosaur egg from the Zhejiang Province, China. They are nearly spherical eggs, measuring up to 13.9 cm (5.5 in) in diameter, and have a thin eggshell. Their shells are made up of three or four superimposed layers of eggshell units. The two known oospecies are distinguished mainly by their pore structure.
Similifaveoloolithus is an oogenus of fossil dinosaur egg from the Tiantai basin in Zhejiang Province, China. It is the sole known oospecies of the oofamily Similifaveoloolithidae.
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.
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.
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.
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.