Nanhsiungoolithusis anoogenus(fossil-egg genus) ofdinosaur eggfrom thelate CretaceousofChina.It belongs to the oofamilyElongatoolithidae,which means that it was probably laid by anoviraptorosaur,though so far no skeletal remains have been discovered in association withNanhsiungoolithus.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.
| Nanhsiungoolithus Temporal range:Late Cretaceous
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Egg fossil classification
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| Basic shell type: | Ornithoid |
| Morphotype: | Ornithoid-ratite |
| Oofamily: | †Elongatoolithidae |
| Oogenus: | †Nanhsiungoolithus Zhao, 1975 |
| Oospecies | |
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Description
editThetype specimenofNanhsiungoolithusis a partial nest containing three mostly complete eggs and impressions. Another partial nest preserves two whole eggs, two incomplete eggs, and two impressions.[1]Like other elongatoolithids, the eggs are found arranged in a circular pattern. The eggs are long and narrow, with an average length of 139.4 mm (5.49 in) and width of 68.4 mm (2.69 in). They are slightly asymmetrical, with one end slightly pointier than the other.Nanhsiungoolithusis distinctive for the smooth texture of its shell, contrasting the rough texture of other types of elongatoolithids.[2]
The eggshell ofNanhsiungoolithusis on average just under 1 mm (0.039 in) thick. Like other members of its oofamily, its shell is divided into two structural layers: The inner layer, known as the mammillary layer, is composed of cone-shaped mammilla which are the bases of the crystalline units making up the eggshell. The outer layer is often called the continuous layer, because in most elongatoolithids the shell units in this layer are fused together.[3]However, inNanhsiungoolithus,the units are not fully fused and can still be seen as distinct columns.[2]
Since the embryo must breathe, eggshells such asNanhsiungoolithushave pores to allow for gas exchange.[4]InNanhsiungoolithus,the pores are sparsely spaced on most of the eggshell, but are much denser on the blunt end. The pores have more irregular-shaped openings than many related types of eggs.[2]
Parenting behavior
editWhile no fossils ofNanhsiungoolithushave been found associated with a parent, multiple fossils confirm that elongatoolithid eggs were laid byoviraptorosauriandinosaurs, who sat on their nests to incubate the eggs. Unlike some other dinosaurs, oviraptorosaurian parents did not bury their eggs.[5]
Classification
editFossilized eggs are classified by a parataxonomic system similar toLinnaean taxonomy.According to this system,Nanhsiungoolithusis an oogenus in the oofamily Elongatoolithidae. Along withMacroolithusandElongatoolithus,it was the first oogenus ever given a formal parataxonomic name; it is amonotypicoogenus, with the single oospeciesN. chuetienensis.[2]
History
editNanhsiungoolithuseggs were first discovered in Southern China by the pioneering Chinese paleontologistYang Zhong gian.In 1965, he described several types of eggs fromNanxiong(Nanhsiung) in Guangdong, including two partial nests that would later be classified inNanhsiungoolithus.He described them as members of the type"Oolithes" elongatus.[1]In 1975, Chinese paleontologist Zhao Zikui created an early version of the modern parataxonomic system, with a hierarchical system of oofamilies, oogenera, and oospecies. Most of the specimens Yang classified asO. elongatuswere classified asElongatoolithus,but two of the partial nests were considered different enough to be placed in their own oogenus,Nanhsiungoolithus.Zhao chose the oogenus name to honor Nanxiong county, with the specific epithetchuetienensismeaning "from Chuetien", after the town nearest where the fossils were discovered.[2]Nanhsiungoolithuseggs were first discovered outside of Guangdong only two years later, when China's Twelfth Geological Brigade discovered many new fossil egg sites in the Xichuan Basin in the Southwest ofHenan.These eggs were not classified until 1998, when Zhao and his colleague Zhao Hong identified the fossils, identifying 8 eggshell fragments from theMajiacun FormationasNanhsiungoolithus chuetienensis.[6]
Distribution and paleoecology
editNanhsiungoolithusis fairly rare, and has only been found inGuangdongandHenan,China. The fossils in Guangdong are found in theNanxiong Basin,which is ancient river basin famously rich in fossil eggs. HereNanhsiungoolithuseggshells are found in the very latestCretaceous,alongsideMacroolithus,Elongatoolithus,Apheloolithus,Prismatoolithus,Stromatoolithus,Ovaloolithus,andShi xing oolithus.[7]The fossils inHenanare found at theMajiacun Formation,which is slightly older, dating from theConiacianto theSantonian,and represents the depositions of a meandering stream system.[8]
See also
editReferences
edit- ^abYoung, Chung-chien (1965)."Fossil eggs from Nanhsiung, Kwangtun and Kanchou, Kiangsi"(PDF).Vertebrata PalAsiatica.9(2): 141–170.
- ^abcdeZhao, Zikui (1975)."The microstructure of the dinosaurian eggshells of Nanxiong, Guangdong Province—on the classification of dinosaur eggs"(PDF).Vertebrata PalAsiatica.13(2): 105–117.
- ^Mikhailov, Konstantin E. (1991)."Classification of fossil eggshells of amniotic vertebrates".Acta Palaeontologica Polonica.36(2): 193–238.
- ^Wilson, Laura E.; Chin, Karen; Jackson, Frankie D.; Bray, Emily S."II. Eggshell morphology and structure".UCMP Online Exhibits: Fossil Eggshell.University of California Berkeley.Retrieved18 May2019.
- ^Tanaka, Kohei; Zelenitsky, Darla K.; Lü, Junchang; DeBuhr, Christopher L.; Yi, Laiping; Jia, Songhai; Ding, Fang; Xia, Mengli; Liu, Di; Shen, Caizhi; Chen, Rongjun (2018)."Incubation behaviors of oviraptorosaur dinosaurs in relation to body size".Biology Letters.14(5): 30280135.doi:10.1098/rsbl.2018.0135.PMC6012691.PMID29769301.
- ^Zhao, Hong; Zhao, Zikui (1998)."Dinosaur eggs from Xichuan Basin, Henan Province"(PDF).Vertebrata PalAsiatica.36(4): 292–296.
- ^Zhao, Zikui; Mao, Xueying; Chai, Zhifang; Yang, Gao giường; Zhang, Fucheng; Yan, Zheng (2009). "Geochemical environmental changes and dinosaur extinction during the Cretaceous-Paleogene (K/T) transition in the Nanxiong Basin, South China: Evidence from dinosaur eggshells".Chinese Science Bulletin.54(5): 806.Bibcode:2009SciBu..54..806Z.doi:10.1007/s11434-008-0565-1.
- ^Liang, Xinquan; Wan, Shunü; Yang, Dongsheng; Zhou, Shiquan; Wu, Shichong (2009)."Dinosaur eggs and dinosaur egg-bearing deposits (Upper Cretaceous) of Henan Province, China: Occurrences, palaeoenvironments, taphonomy and preservation".Progress in Natural Science.19(11): 1587–1601.doi:10.1016/j.pnsc.2009.06.012.