| Dictyoolithus | |
|---|---|
Egg fossil classification  | |
| Basic shell type: | † Dinosauroid-spherulitic |
| Oofamily: | † Dictyoolithidae |
| Oogenus: | † Dictyoolithus Zhao, 1994 |
| Type oospecies | |
| †Dictyoolithus hongpoensis Zhao, 1994 | |
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.
Dictyoolithus is known from Hongpo, a town in Xixia County, Henan. This is in the Lower Cretaceous Sigou Formation. [1] It has also been discovered in Lishui, Zhejiang, in the Upper Cretaceous Chichengshan Formation. [2]
Dictyoolithus was first discovered and described in 1994 by Chinese paleontologist and pioneer of fossil eggshell classification, Zhao Zikui. He named two oopsecies: D. hongpoensis and D. neixiangensis (now Protodictyoolithus neixiangensis ). However, since excavations were still going on at the time, his description was brief. [1] In 2004, a third oospecies was named, D. jiangi, [3] followed by a fourth, D. gonzhulingensis in 2006. [4] However, in 2013 Chinese paleontologists Wang Qiang, Zhao Zikui, Wang Xiaolin, Zhang Shukang, and Jiang Yan'gen did a reanalysis of the entire oofamily Dictyoolithidae, and split the oogenus Dictyoolithus into two, classifying "D." neixiangensis and "D." jiangi within a new oogenus: Protodictyoolithus . Furthermore, they moved "D." gonzhulingensis into an entirely different oofamily and oogenus, reclassifying it as a member of Similifaveoloolithus . [5]
Dictyoolithus eggs are roughly spherical and measure from 12–16 centimetres (4.7–6.3 in) in diameter. [2] Their eggshell is between 2.5 and 2.8 mm thick. The surface ornamentation is smooth with a grainy texture, or has very low rounded nodes. The eggshell is notable for being composed of more than five superimposed layers of eggshell units. [5] In some specimens, found at Lishui, no superimposed layers of eggshells were found. [2] However, it is not certain that these specimens in fact represent Dictyoolithus. [5] The eggshell units have a reticulate organization. [1]
Since no embryos or adult remains have been found with Dictyoolithus eggs, it is uncertain what kind of dinosaur laid them. [6] A cladistic analysis in 2010 by Jin et al. found Dictyoolithus to be basal theropod eggs. [2] Similarly, Sellés and Galobart in 2015 found Dictyoolithus to be basal theropods, and considered it to be the eggs of megalosauroids. [7]
Unlike many dinosaur eggs, the calcareous and membranous parts of Dictyoolithus eggshells probably formed simultaneously in the oviduct, as in the modern tuatara. [1]
Dictyoolithus is classified in the oofamily Dictyoolithidae, alongside Protodictyoolithus and Paradictyoolithus . It contains only a single oospecies: D. hongpoensis. [5] Mikhailov (1997) suggested that it may actually be a dendroolithid. [8]
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.
Dendroolithus is an oogenus of Dendroolithid dinosaur egg found in the late Cenomanian Chichengshan Formation, in the Gong-An-Zhai and Santonian Majiacun Formations of China and the Maastrichtian Nemegt and Campanian Barun Goyot Formation of Mongolia. They can be up to 162 mm long and 130 mm wide. These eggs may have been laid by a Therizinosaur, Sauropod, or Ornithopod. The oospecies "D." shangtangensis was originally classified as Dendroolithus, however, it has since been moved to its own distinct oogenus, Similifaveoloolithus. This oogenus is related with embryos of the theropod Torvosaurus
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.
Ovaloolithus is an oogenus of dinosaur egg. Eggs of the genus have been found in China, Mongolia and Utah.
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.
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.
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.
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.
Parafaveoloolithus is an oogenus of Faveoloolithid fossil egg, known from the Cretaceous of China.
Mosaicoolithus is an oogenus of fossil egg from the Cenomanian Chichengshan Formation and Albian to Cenomanian Laijia Formation of Tiantai County, Zhejiang Province in China. Its classification is uncertain. The eggs are spherical, and 8.8 cm in diameter. It is distinctive for having irregular pore canals, sometimes filled by secondary shell units. Originally, it was classified as two separate oospecies of Spheroolithus: S. zhangtoucaoensis and S. jincunensis. However, these oospecies were synonymized and placed into a new oogenus by Wang et al. (2011).
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.
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.
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.
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.