Dictyoolithusis anoogenusofdinosaur eggfrom theCretaceousofChina.It is notable for having over five superimposed layers of eggshell units. Possibly, it was laid bymegalosauroiddinosaurs.
| Dictyoolithus Temporal range:
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|---|---|
Egg fossil classification
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| Basic shell type: | †Dinosauroid-spherulitic |
| Oofamily: | †Dictyoolithidae |
| Oogenus: | †Dictyoolithus Zhao,1994 |
| Type oospecies | |
| †Dictyoolithus hongpoensis Zhao, 1994
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Distribution
editDictyoolithusis known from Hongpo, a town inXixia County,Henan.This is in theLower CretaceousSigou Formation.[1]It has also been discovered inLishui,Zhejiang,in theUpper CretaceousChichengshan Formation.[2]
History
editDictyoolithuswas first discovered and described in1994by Chinese paleontologist and pioneer of fossil eggshell classification,Zhao Zikui.He named two oospecies:D. hongpoensisandD. neixiangensis(nowProtodictyoolithus neixiangensis). However, since excavations were still going on at the time, his description was brief.[1]In2004,a third oospecies was named,D. jiangi,[3]followed by a fourth,D. gonzhulingensisin 2006.[4]However, in2013Chinese paleontologists Wang Qiang, Zhao Zikui, Wang Xiaolin, Zhang Shukang, and Jiang Yan'gen did a reanalysis of the entire oofamily Dictyoolithidae, and split the oogenusDictyoolithusinto two, classifying"D." neixiangensisand"D." jiangiwithin a new oogenus:Protodictyoolithus.Furthermore, they moved"D." gonzhulingensisinto an entirely different oofamily and oogenus, reclassifying it as a member ofSimilifaveoloolithus.[5]
Description
editDictyoolithuseggs 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 representDictyoolithus.[5]The eggshell units have a reticulate organization.[1]
Paleobiology
editSince no embryos or adult remains have been found withDictyoolithuseggs, it is uncertain what kind of dinosaur laid them.[6]Acladistic analysisin 2010 by Jinet al.foundDictyoolithusto be basal theropod eggs.[2]Similarly, Sellés and Galobart in2015foundDictyoolithusto be basal theropods, and considered it to be the eggs ofmegalosauroids.[7]
Unlike many dinosaur eggs, the calcareous and membranous parts ofDictyoolithuseggshells probably formed simultaneously in the oviduct, as in the moderntuatara.[1]
Parataxonomy
editDictyoolithusis classified in the oofamily Dictyoolithidae, alongsideProtodictyoolithusandParadictyoolithus.Itcontains only a single oospecies:D. hongpoensis.[5]Mikhailov (1997) suggested that it may actually be adendroolithid.[8]
References
edit- ^abcdZ.-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.
- ^abcdJin 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.
- ^abcdWang 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 PalAsiatica51:43–54.
- ^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.56.London: The Palaeontological Association: 1–77.