| Ashorocetus/sandbox/Dendroolithidae Temporal range:
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|---|---|
Egg fossil classification 
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| Basic shell type: | †Dinosauroid-spherulitic |
| Oofamily: | †Dendroolithidae |
| Oogenera | |
Description
editDendroolithids are medium-sized eggs ranging from 6 to 20 cm (2.4 to 7.9 in) in diameter. They range in shape from spherical to slightly elongated. In Paradendroolithus, they are distinctive for being pointed on one end.[1] The eggshell has an irregularly patterned rough outer surface. Like other dinosaur eggs, the shell is made up of crystaline units, which are distinct in dendroolithids for their irregularly branching, tree-like shapes, from whence the oofamily derives its name (from the root "dendros" meaning tree). The branched shell units interlock and may be fused near the surface. The pores in the eggshell are also irregular, with variable width and forming networks and canals throughout the shell. The pores cut through the shell units instead of merely being gaps between them. In general, dendroolithids resemble dictyoolithids, but with less branching of the pore canals. Since the eggshell microstructure can be highly variable even in a single specimen, they can be difficult to classify, and divisions of oospecies are generally based on general size and shape of the eggs.[2][3]
Paleobiology
editEmbryonic remains are rare in general, but some crushed dendroolithid eggshells have been found in association with a theropod embryo, probably referable to Torvosaurus. These eggs were almost certainly buried by their parent, which can be deduced not only from the lack of taphonomic disturbance of the clutch, but also because of the high porosity of the eggshell, at trait associated with egg burial. The high porosity of eggshells allows for greater gas and water exchange between the embryo and the external environment, which is necessary to prevent the embryo from suffocating when it is buried in substrate.[4]
History
editDendroolithidae was first named in 1988, when the Chinese paleontologists Zhao Zikui and Li Zuocong described the oospecies Dendroolithus wangdianensis, which they noted was different enough from elongatoolithids, spheroolithids, and faveoloolithids to warrant a new oofamily.[5] In 1991, the Russian paleontologist Konstantin Mikhailov reported the discovery of dendroolithid eggs in the Gobi desert in Mongolia,[6] which he described more in depth in 1994 as two oospecies, D. verrucarius and D. microporosus.[7] In 1997, Mikhailov suggested that perhaps, pending further study, Dictyoolithus could be in fact a dendroolithid.[3]
In 1998, Zhou Xiugao, Ren Youfu, Xu Shiqiu, and Guan Kangnian, a team of Chinese paleontologists from the China University of Geoscience in Wuhan, described several newly discovered dendroolithids in the Qinglong mountain region of Hubei.[1]
In 2013, a team of scientists working in Portugal discovered a fossil eggs with embryonic remains in Portugal, which represented the first discovery of dendroolithids in the Jurassic and the first discovery of the oofamily outside of Asia.[4]
Distribution and Paleoecology
editDendroolithids are known primarily from late Cretaceous formations China and Mongolia,[3] but there are also eggshells referable to Dendroolithidae found in the late Jurassic of Portugal, in the Lourinhã Formation.[4]
References
edit- ^ a b Zhou, Xiugao; ren, Youfu; Xu, Shiqiu; Guan, Kangnian (1998). "Dinosaur eggs of the Late Cretaceous from Qinglongshan region, Yunxian County, Hubei Province". Hubei Geology & Mineral Resources. 12 (3): 1–8.
- ^ Appendix II in Carpenter, K. 1999. Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past). Indiana University Press, Bloomington, Indiana.
- ^ a b c 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.
- ^ a b c Araújo, Ricardo; Castanhinha, Rui; Martins, Rui M.S.; Mateus, Octávio; Hendrickx, Christophe; Beckmann, F.; Schell, N.; Alves, L.C. (2013). "Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal". Scientific Reports. 3: srep01924. doi:10.1038/srep01924.
- ^ Zhao, Zikui; Li, Zuocong (1988). "A new structural type of dinosaur eggs from Anlu County, Hubei Province" (PDF). Vertebrata PalAsiatica. 26 (2): 107–115.
- ^ Mikhailov, Konstantin (1991). "Classification of Fossil Eggshills of Amniotic Vertebrates". Acta Paleontologica Polonica. 36 (2): 193–238.
- ^ Mikhailov, Konstantin (1994). "Eggs of sauropod and ornithopod dinosaurs from the Cretaceous deposits of Mongolia". Paleontological Journal. 28 (3): 141–159.