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 China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

Distribution

All known dictyoolithids are known from the Cretaceous of

; they have been found in Henan, Zhejiang, and

Shandong Shandong ( , ; ; alternately romanized as Shantung) is a coastal province of the People's Republic of China and is part of the East China region. Shandong has played a major role in Chinese history since the beginning of Chinese civilizati ...

, from the Liuyemiao Formation, the

Zhaoying Formation The Zhaoying Formation is a Coniacian geologic formation in Henan Province, China.Chichengshan Formation, and the Wangshi Group.

History

Dictyoolithidae was first described in

1994 File:1994 Events Collage.png, From left, clockwise: The 1994 Winter Olympics are held in Lillehammer, Norway; The Kaiser Permanente building after the 1994 Northridge earthquake; A model of the MS Estonia, which Sinking of the MS Estonia, sank in ...

by the Chinese paleontologist

Zhao Zikui Zhao may refer to: * Zhao (surname) (赵), a Chinese surname ** commonly spelled Chao in Taiwan or up until the early 20th century in other regions ** Chiu, from the Cantonese pronunciation ** Cho (Korean surname), represent the Hanja 趙 (Chine ...

; he named only a single oogenus, '' Dictyoolithus'', with two oospecies: ''D. neixiangensis'' and ''D. hongpoensis''. Because excavations were still going on at the time, however, Zhao did not provide a detailed description. After that, dictyoolithids received little attention in the scientific literature because of the rarity of their fossils. However, in

2013 File:2013 Events Collage V2.png, From left, clockwise: Edward Snowden becomes internationally famous for leaking classified NSA wiretapping information; Typhoon Haiyan kills over 6,000 in the Philippines and Southeast Asia; The Dhaka garment fact ...

Chinese paleontologists Wang Qiang, Zhao Zikui, Wang Xiaolin, Zhang Shukang, and Jiang Yan'gen discovered new remains and did a comprehensive reanalysis of the oofamily. The split ''Dictyoolithus'' into two oogenera: ''Dictyoolithus'' and ''Protodictyoolithus'', as well as adding a new oogenus, ''Paradictyoolithus'', based on newly discovered remains. One oospecies, ''"D." gongzhulingensis'', was moved to an entirely different oofamily and reclassified as an oospecies of '' Similifaveoloolithus''.Wang Qiang, Zhao Zikui, Wang Xiaolin, Zhang Shukang, and Jiang Yan'gen. (2013)
New forms of dictyoolithids from the Tiantai Basin, Zhejiang Province of China and a parataxonomic revision of the dictyoolithids.
''Vertebrata PalAsiatica'' 51:43–54.

Description

Dictyoolithid eggs are spherical or oval in shape. The outer surface is smooth or covered with low nodes. The eggshell units and pore canals are irregularly shaped.Z.-K. Zhao. (1994) "Dinosaur eggs in China:On the structure and evolution of eggshells." In K. Carpenter, K. F. Hirsch, and J. R. Horner (eds.), ''Dinosaur Eggs and Babies,'' Cambridge University Press, Cambridge. Cambridge. pp. 184–203. Dictyoolithids are unique for having a reticulate-like organization of eggshell units, which resembles the honeycomb-like structure of faveoloolithids. The eggshell units are branching,Xie, J.-F., Zhang, S.-K., Jin, X.-S., Li, D.-Q., and Zhou, L.-Q. (2016)
A new type of dinosaur eggs from Early Cretaceous of Gansu Province, China.
" ''Vertebrata PalAsiatica'', 54(1):1–10. and superimposed in multiple layers throughout the eggshell. However, in

2010 File:2010 Events Collage New.png, From top left, clockwise: The 2010 Chile earthquake was one of the strongest recorded in history; The Eruption of Eyjafjallajökull in Iceland disrupts air travel in Europe; A scene from the opening ceremony of ...

, Jin ''et al.'' argued that superimposed shell units were not universal to the oofamily because they had discovered three fossil

egg clutch __NOTOC__ A clutch of eggs is the group of eggs produced by birds, amphibians, or reptiles, often at a single time, particularly those laid in a nest. In birds, destruction of a clutch by predators (or removal by humans, for example the Califor ...

es, referred to ''D. hongpoensis'', in

Lishui Lishui (; Lishuinese: ''li⁶ syu³'' ) is a prefecture-level city in the southwest of Zhejiang province, People's Republic of China. It borders Quzhou, Jinhua and Taizhou to the north, Wenzhou to the southeast, and the province of Fujian to ...

, Zhejiang which lacked this characteristic. However, the identification of these eggs as dictyoolithids is disputed; they may in fact represent Faveoloolithidae, an oofamily which is similar in microstructure to Dictyoolithidae.

Paleobiology

It is unknown what kind of dinosaur laid dictyoolithid eggs, because they have not been associated with embryos or skeletal remains.Varricchio, D. J. (2011). A distinct dinosaur life history?. Historical Biology, 23(01), 91–107. Chicago A phylogenetic analysis in 2010, based on the remains from Lishui that possibly belong to ''Dictyoolithus hongpoensis'', found it to be the eggs of theropods. Similarly, a cladistic analysis by Sellés and Galobart in

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found ''Dictyoolithus'' to be a theropod egg more basal than Prismatoolithidae,

Elongatoolithidae Elongatoolithidae is an oofamily of fossil eggs, representing the eggs of oviraptorosaurs (with the exception of the avian '' Ornitholithus''). They are known for their highly elongated shape. Elongatoolithids have been found in Europe, Asia, and ...

, and

avian Avian may refer to: *Birds or Aves, winged animals *Avian (given name) (russian: Авиа́н, link=no), a male forename Aviation *Avro Avian, a series of light aircraft made by Avro in the 1920s and 1930s *Avian Limited, a hang glider manufacture ...

eggs, so they considered it to be the eggs of a megalosauroid.Sellés, A. G., & Galobart, À. (2015). "Reassessing the endemic European Upper Cretaceous dinosaur egg Cairanoolithus." ''Historical Biology,'' (ahead-of-print), 1–14.

Eggshell formation

Dinosaur eggshells formed in two different ways:

Spheroolithidae 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.Z.-K. Zhao. (1994) "Dinosaur egg ...

, Dendroolithidae, and

had eggs forming similar to those of

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

, with the membrane forming before the hard, calcareous part of the shell. On the other hand, in Dictyoolithidae and Faveoloolithidae, the membrane and calcareous parts of the eggshell formed simultaneously.

Parataxonomy

Under the basic type and morphotype system of classification for fossil eggs, dictyoolithids are classified in an unnamed morphotype in the dinosauroid-spherulitic basic type. However, morphotypes and basic types are not normally used in modern research as they are often redundant and uninformative.Zelenitsky, D. K., and Therrien, F. (2008). "Phylogenetic analysis of reproductive traits of maniraptoran theropods and its implications for egg parataxonomy." ''

Palaeontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

'', 51(4): 807–816.Grellet-Tinner, G., and Norell, M. (2002). "An avian egg from the Campanian of Bayn Dzak, Mongolia." '' Journal of Vertebrate Paleontology'', 22(3): 719–721. Dictyoolithidae contains three oogenera: ''Dictyoolithus'', ''Paradictyoolithus'', and ''Protodictyoolithus''. ''

Stromatoolithus ''Stromatoolithus'' is an oogenus of dinosaur egg. The oogenus contains one oospecies, ''S. pinglingensis''. ''Stromatoolithus''at Fossilworks.org See also * List of dinosaur oogenera Egg fossils are the fossilized remains of eggs laid by ...

'' has also been classified as a dictyoolithid, but due to its very brief description comparison is difficult.Jin X.S., Jackson F.D., Varricchio D.J., Y. Azuma, and He T. (2010) "The first Dictyoolithus egg clutches from the Lishui Basin, Zhejiang Province, China." '' Journal of Vertebrate Paleontology'', 30(1): 188–195

References

{{Taxonbar, from=Q22286862 Egg fossils Cretaceous dinosaurs of Asia