Nanhsiungoolithus

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Nanhsiungoolithus
Temporal range: Late Cretaceous
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Egg fossil classification Red Pencil Icon.png
Basic shell type: Ornithoid
Morphotype: Ornithoid-ratite
Oofamily:† Elongatoolithidae
Oogenus:†Nanhsiungoolithus
Zhao, 1975
Oospecies
  • N. chuetienensisZhao, 1975

Nanhsiungoolithus is an oogenus (fossil-egg genus) of dinosaur egg from the late Cretaceous of China. It belongs to the oofamily Elongatoolithidae, which means that it was probably laid by an oviraptorosaur, though so far no skeletal remains have been discovered in association with Nanhsiungoolithus. 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.

Contents

Description

The type specimen of Nanhsiungoolithus is 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. Nanhsiungoolithus is distinctive for the smooth texture of its shell, contrasting the rough texture of other types of elongatoolithids. [2]

The eggshell of Nanhsiungoolithus is 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, in Nanhsiungoolithus, the units are not fully fused and can still be seen as distinct columns. [2]

Since the embryo must breathe, eggshells such as Nanhsiungoolithus have pores to allow for gas exchange. [4] In Nanhsiungoolithus, 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

While no fossils of Nanhsiungoolithus have been found associated with a parent, multiple fossils confirm that elongatoolithid eggs were laid by oviraptorosaurian dinosaurs, who sat on their nests to incubate the eggs. Unlike some other dinosaurs, oviraptorosaurian parents did not bury their eggs. [5]

Classification

Fossilized eggs are classified by a parataxonomic system similar to Linnaean taxonomy. According to this system, Nanhsiungoolithus is an oogenus in the oofamily Elongatoolithidae. Along with Macroolithus and Elongatoolithus , it was the first oogenus ever given a formal parataxonomic name; it is a monotypic oogenus, with the single oospecies N. chuetienensis. [2]

History

Nanhsiungoolithus eggs were first discovered in Southern China by the pioneering Chinese paleontologist Yang Zhongjian. In 1965, he described several types of eggs from Nanxiong (Nanhsiung) in Guangdong, including two partial nests that would later be classified in Nanhsiungoolithus. 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 as O. elongatus were classified as Elongatoolithus, 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 epiphet chuetienensis meaning "from Chuetien", after the town nearest where the fossils were discovered. [2] Nanhsiungoolithus eggs 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 of Henan. These eggs were not classified until 1998, when Zhao and his colleague Zhao Hong identified the fossils, identifying 8 eggshell fragments from the Majiacun Formation as Nanhsiungoolithus chuetienensis. [6]

Distribution and paleoecology

Nanhsiungoolithus is fairly rare, and has only been found in Guangdong and Henan, China. The fossils in Guangdong are found in the Nanxiong Basin, which is ancient river basin famously rich in fossil eggs. Here Nanhsiungoolithus eggshells are found in the very latest Cretaceous, alongside Macroolithus, Elongatoolithus, Apheloolithus, Prismatoolithus , Stromatoolithus , Ovaloolithus , and Shixingoolithus . [7] The fossils in Henan are found at the Majiacun Formation, which is slightly older, dating from the Coniacian to the Santonian, and represents the depositions of a meandering stream system. [8]

See also

Related Research Articles

<i>Elongatoolithus</i> Fossil dinosaur eggs

Elongatoolithus is an oogenus of dinosaur eggs found in the Late Cretaceous formations of China and Mongolia. Like other elongatoolithids, they were laid by small theropods, and were cared for and incubated by their parents until hatching. They are often found in nests arranged in multiple layers of concentric rings. As its name suggests, Elongatoolithus was a highly elongated form of egg. It is historically significant for being among the first fossil eggs given a parataxonomic name.

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.

<i>Youngoolithus</i> oogenus of fossil egg

Youngoolithus is an oogenus of dinosaur egg. It is the sole member of the oofamily Youngoolithidae, and consists of a single oospecies: Youngoolithus xiaguanensis. It consists of a single fossil nest of 16 eggs with an associated dinosaur footprint that was first discovered in 1975 near Houzhuang Village, Henan Province, in the Cretaceous Xiaguan Basin. The eggs are smooth, olive-shaped, and arranged in five rows. It was originally described as being a Faveoloolithid egg, however the nest is arranged quite differently than other members of that family, so it has been moved to its own oofamily, Youngoolithidae.

Shixingoolithus is an oogenus of dinosaur egg from the Cretaceous of Nanxiong, China.

<i>Macroelongatoolithus</i> oogenus of fossil egg

Macroelongatoolithus is an oogenus of large, fossil theropod eggs. They are known from Asia and from North America.

<i>Macroolithus</i> oogenus of fossil egg

Macroolithus is an oogenus of dinosaur egg belonging to the oofamily Elongatoolithidae. The type oospecies, M. rugustus, was originally described under the now-defunct oogenus name Oolithes. Three other oospecies are known: M. yaotunensis, M. mutabilis, and M. lashuyuanensis. They are relatively large, elongated eggs with a two-layered eggshell. Their nests consist of large, concentric rings of paired eggs. There is evidence of blue-green pigmentation in its shell, which may have helped camouflage the nests.

Phaceloolithus is an oogenus of dinosaur egg found in the Dongting basin of the Hunan Province of China. The eggs have a subspherical shape, measuring up to 168 mm on the long axis, and having a very thin shell.

Continuoolithus is an oogenus of dinosaur egg found in the late Cretaceous of North America. It is most commonly known from the late Campanian of Alberta and Montana, but specimens have also been found dating to the older Santonian and the younger Maastrichtian. It was laid by an unknown type of theropod. These small eggs are similar to the eggs of oviraptorid dinosaurs, but have a distinctive type of ornamentation.

Porituberoolithus is an oogenus of dinosaur egg found in the late Campanian of Alberta. It was originally described as distinct from the Elongatoolithids on the basis of its ornamentation, but it was listed as a member of that oofamily by Wang et al. 2010. It is very similar to Subtiliolithus, but has a thicker shell.

Egg fossil fossilized remains of eggs laid by ancient animals

Egg fossils are the fossilized remains of eggs laid by ancient animals. As evidence of the physiological processes of an animal, egg fossils are considered a type of trace fossil. Under rare circumstances a fossil egg may preserve the remains of the once-developing embryo inside, in which case it also contains body fossils. A wide variety of different animal groups laid eggs that are now preserved in the fossil record beginning in the Paleozoic era. Examples include invertebrates like ammonoids as well as vertebrates like fishes, possible amphibians, and reptiles. The latter group includes the many dinosaur eggs that have been recovered from Mesozoic strata. Since the organism responsible for laying any given egg fossil is frequently unknown, scientists classify eggs using a parallel system of taxonomy separate from but modeled after the Linnaean system. This "parataxonomy" is called veterovata.

Paraelongatoolithus is a late Cretaceous oogenus of Chinese fossil egg, classified in the oofamily Elongatoolithidae, which represents the eggs of oviraptorosaurs.

Coralloidoolithus is an oogenus of dinosaur egg from the Tiantai Basin in Zhejiang Province, containing a single known oospecies C. shizuiwanensis. Formerly, it was classified in the oogenus Paraspheroolithus; however, it was considered sufficiently different to be classified in its own genus. C. shizuiwanensis is similar to Stalicoolithus, leading to their classification in the same family, Stalicoolithidae.

Paradictyoolithus is an oogenus of dictyoolithid dinosaur egg from the Zhejiang Province, China. They are nearly spherical eggs, measuring up to 13.9 cm (5.5 in) in diameter, and have a thin eggshell. Their shells are made up of three or four superimposed layers of eggshell units. The two known oospecies are distinguished mainly by their pore structure.

Similifaveoloolithus is an oogenus of fossil dinosaur egg from the Tiantai basin in Zhejiang Province, China. It is the sole known oospecies of the oofamily Similifaveoloolithidae.

Hemifaveoloolithus is an oogenus of fossil dinosaur egg from the Tiantai basin in Zhejiang Province, China. It is a faveoloolithid, having spherical eggs roughly 13 cm in diameter. The shell is distinctive for being composed of four or five superimposed layers of shell units, and the honeycomb-like arrangement of pore canals.

Parafaveoloolithus is an oogenus of Faveoloolithid fossil egg, known from the Cretaceous of China.

Heishanoolithus is an oogenus of Elongatoolithid fossil egg from the Shahai Formation in Liaoning. It is known only from seven eggshell fragments. It is most notable for having a very thin eggshell, the dense covering of nodes on the eggshell surface, and for its relatively thin mammilary layer. While no remains of Heishanoolithus have been associated with skeletal remains, strong evidence links Elongatoolithid eggs to Oviraptorosaurs.

Elongatoolithidae oofamily of fossil egg

Elongatoolithidae is an oofamily of fossil eggs, representing the eggs of oviraptorosaurs. They are known for their highly elongated shape. Elongatoolithids have been found in Europe, Asia, and both North and South America.

Undulatoolithus is an oogenus of Chinese fossil dinosaur egg belonging to Elongatoolithidae. It is very similar to Macroolithus, but has different ornamentation. Like other elongatoolithids, it was probably laid by oviraptorosaurs.

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.

References

  1. 1 2 Young, Chung-chien (1965). "Fossil eggs from Nanhsiung, Kwangtun and Kanchou, Kiangsi" (PDF). Vertebrata PalAsiatica. 9 (2): 141–170.
  2. 1 2 3 4 5 Zhao, 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.
  3. ↑ Mikhailov, Konstantin E. (1991). "Classification of fossil eggshells of amniotic vertebrates". Acta Palaeontologica Polonica. 36 (2): 193–238.
  4. ↑ 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. Retrieved 18 May 2019.
  5. ↑ 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. PMC   6012691 . PMID   29769301.
  6. ↑ Zhao, Hong; Zhao, Zikui (1998). "Dinosaur eggs from Xichuan Basin, Henan Province" (PDF). Vertebrata PalAsiatica. 36 (4): 292–296.
  7. ↑ Zhao, Zikui; Mao, Xueying; Chai, Zhifang; Yang, Gaochuang; 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. doi: 10.1007/s11434-008-0565-1 .
  8. ↑ 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 .
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