Biology:Dictyoolithus
| Dictyoolithus | |
|---|---|
Egg fossil classification 
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| 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.
Distribution
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]
History
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]
Description
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]
Paleobiology
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]
Parataxonomy
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]
References
- ↑ 1.0 1.1 1.2 1.3 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.
- ↑ 2.0 2.1 2.2 2.3 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
- ↑ Liu, J., & Zhao, Z. (2004). A new oospecies of the dinosaur eggs (Dictyoolithus) from Laiyang, Shandong Province. Vertebrata Pal Asiatica, 42(2), 166–170.
- ↑ Wang Qiang, Zan Shu-Qin, Jin Li-Yong, Chen Jun (2006). A New Oospecies, Dictyoolithus Gongzhulingensis, from the Early Cretaceous Quantou Formation in the Central Jilin Province. Journal of Jilin University (Earth Science Edition), 36(2): 153–157.
- ↑ 5.0 5.1 5.2 5.3 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.
- ↑ Varricchio, D. J. (2011). A distinct dinosaur life history?. Historical Biology, 23(01), 91–107. Chicago
- ↑ Sellés, A. G., & Galobart, À. (2015). "Reassessing the endemic European Upper Cretaceous dinosaur egg Cairanoolithus." Historical Biology, (ahead-of-print), 1–14.
- ↑ Mikhailov, Konstantin (1997). "Fossil and recent eggshell in amniotic vertebrates: fine structure, comparative morphology, and classification". Special Papers in Palaeontology (London: The Palaeontological Association) 56: 1–77.
Wikidata ☰ Q5274009 entry
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