Elongatoolithus

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Elongatoolithus
Temporal range: Late Cretaceous
Elongatoolithusbcn.JPG
Elongatoolithus excellens nest in CosmoCaixa Barcelona.
Egg fossil classification OOjs UI icon edit-ltr.svg
Basic shell type: Ornithoid
Morphotype: Ornithoid-ratite
Oofamily:† Elongatoolithidae
Oogenus:† Elongatoolithus
Zhao, 1975
Type oospecies
†Elongatoolithus andrewsi
Zhao, 1975
Oospecies

See text

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 (probably oviraptorosaurs), 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.

Contents

Description

Elongatoolithus eggs are small to midsized eggs, with a maximum size of about 17 cm (6.7 in). The eggs are highly elongated, typically being 2 to 2.2 times longer than they are wide, and slightly asymmetric (with one end pointier than the other). The outer surface of their shells is ornamented with a fine pattern of nodes and ridges, either aligned parallel to the egg's long axis (lineartuberculate ornamentation) or in irregular chains (ramotuberculare ornamentation). At the ends of the egg, the ornamentation may become randomly dispersed nodes (dispersituberculate ornamentation). [1] [2] : 8–10  This ornamentation is less pronounced than that of the closely related Macroolithus . [3]

In general, the shell of elongatoolithids is made up of two structural layers: the inner layer, called the mammillary (or cone) layer, is made up of cone-shaped structures called mammillae, and the outer layer, called the continuous layer, is made up of shell units fused together into a continuum with a scale-like, or squamatic, structure. [2] Elongatoolithus has an abrupt boundary between these two layers, and the continuous layer is two to six times thicker than the mammillary layer. Wavy growth lines can be observed in the continuous layer parallel to the egg's surface. [4] They have an angusticanalicute pore system, meaning that the eggshells have narrow, straight pores. [1]

Oospecies

Pair of E. elongatus eggs, Paleozoological Museum of China ElongatoolithusElongatus-PaleozoologicalMuseumOfChina-May23-08.jpg
Pair of E. elongatus eggs, Paleozoological Museum of China

Several oospecies of Elongatoolithus are known. They can be broadly divided into two classes based on ornamentation: most oospecies have linear ridges parallel to the long axis of the egg, but some (notably E. sigillarius and E. excellens) a rippled pattern of reoriented ridges transverse to the egg's long axis. [1] Within these two groups, oospecies vary primarily by eggshell thickness, ratio of continuous to mammillary layer, and overall size of the eggs. [2] Identification of oospecies based on fragments (not whole eggs) can be problematic. [1]

Paleobiology and parenting

Parenting

Fossil of Citipati parent sitting on its nest Citipati IGM 100 979.jpg
Fossil of Citipati parent sitting on its nest

Elongatoolithus were most likely laid by oviraptorosaurs. While most eggs are preserved without any trace of embryo or parent, several elongatoolithid nests have been found in association with skeletons of adult oviraptorosaurs. The parents apparently brooded on the nest to incubate the eggs. [2] An adult Citipati skeleton was discovered in the Upper Cretaceous of Mongolia associated with a nest of eggs most likely referable to E. frustrabilis. [8] Like many types of modern birds, Elongatoolithus nests would have been cared for by the father of a communal nest, which would contain eggs of several females. [12]

Nests

Several nests of Elongatoolithus eggs are known. [4] [5] [10] They follow the typical elongatoolithid pattern of arranging eggs in multi-layered circular nests. [2] The type specimen of E. andrewsi consists of a well preserved nest, containing eleven eggs arranged in at least two circular layers. [6] [5] The type specimen of E. elongatus is a similarly structured, well preserved nest of 13 eggs. These eggs are broken, apparently because they had hatched before fossilizing. [13] Like other elongatoolithids, the eggs are found paired because the parents would lay two eggs at a time. Unlike modern birds, dinosaurs had two functioning oviducts, so they could produce two eggs simultaneously, as shown by a fossil oviraptorosaur discovered in China with a pair of elongatoolithid eggs preserved in its pelvis. [14]

Most, if not all, elongatoolithid nests would not have been buried by their parents. [15] However, according to a statistical analysis of eggshell pore density by Tanaka et al. (2015), it is possible that E. elongatus eggs were buried. [15]

Classification

Fossilized eggs are classified in their own, parataxonomic system parallel to Linnaean taxonomy. Elongatoolithus and the closely related oogenera Macroolithus and Nanhsiungoolithus were the first oogenera described in this system. These oogenera are all classified in the oofamily Elongatoolithidae. [5]

Elongatoolithus contains eight oospecies. The type oospecies was designated by Zhao 1975 as E. andrewsi, [5] but some later publications list E. elongatus as the type. [3] [1] Five oospecies originally described as Elongatoolithus in fact belong to Prismatoolithidae: "E." chichengshanensis, "E." chimeiensis, "E." jiangchangensis, and "E." laijiaensis, and "E." tiantaiensis (which has been recombined as Prismatoolithus tiantaiensis). [7] [16]

History

In 1954, Chinese paleontologist Yang Zhongjian described several fossil eggs from Laiyang, including an elongated type which he named "Oolithes" elongatus. He noted their similarity to Mongolian fossil eggs supposedly laid by Protoceratops , and therefore conjectured "O" elongatus was laid by a similar type of dinosaur. [13] Later, in 1965, Yang discovered a comparable type of egg in Nanxiong. [6] In 1975, the Chinese paleontologist Zhao Zikui published the prototype of the modern parataxonomic system for eggshell classification, dividing fossil eggs into oospecies, oogenera, and oofamilies. He named the oogenus Elongatoolithus to contain the majority Yang's "O." elongatus specimens, splitting it into two separate oospecies: E. andrewsi, based on a well-preserved nest described by Yang (1965), and E. elongatus for most of the rest of the "O." elongatus specimens. Two partially preserved "O." elongatus nests were reclassified into their own oogenus, Nanhsiungoolithus . He also noted that several types of fossil eggs from Mongolia and North America were also probably attributable to Elongatoolithus. [5]

In 1979 another oospecies, E. magnus, was discovered and named by the Chinese paleontologists Zeng Demin and Zhang Jinjian, based on a nest of nine eggs uncovered in Hunan. They also described other Elongatoolithus specimens of an indeterminate oospecies. [10]

In 1991, the Russian paleontologist Konstantin Mikhailov created the modern, formal classification scheme for fossil eggs. He used Zhao's naming conventions, keeping Elongatoolithus, Macroolithus, and Nanhsiungoolithus in Elongatoolithidae. He mentioned that several Mongolian eggs were referable to Elongatoolithidae or Elongatoolithus. He also recognized elongatoolithids to be theropod eggs, demonstrating their numerous structural differences from the supposed Protoceratops eggs. [17] In 1994, when Mikhailov described and reviewed the fossil elongated eggs from Mongolia, he named four new oospecies of Elongatoolithus (E. excellens, E. frustrabilis, E. subtitectorius, and E. sigillarius) as well as mentioning two other unnamed forms. [3] Also in 1994, the theropod parentage of Elongatoolithus was confirmed when an oviraptorid embryo was discovered preserved inside an elongatoolithid egg, [18] which Mikhailov (1997) tentatively referred to Elongatoolithus. [1]

The Chinese paleontologist Yu Xinqi named E. taipinghuensis, based on newly discovered remains from Anhui, in 1998. [11]

In 2000, the Chinese paleontologists Fang Xiaosi, Wang Yaozhong, and Jiang Yan'gen described several ootaxa from the egg-rich Tiantai Basin, including the oospecies E. tiantaiensis. [19] In 2003, Fang and his colleagues also described E. chichengshanensis and E. laijiaensis. [20] However, Wang et al. 2010 questioned the referral of these oospecies to Elongatoolithus. They argued that E. chichengshanensis should belong to a new group, E. laijiaensis required further study to determine its affinities, and E. tiantaiensis should be moved to Prismatoolithidae. [21] In 2011, Wang et al. formally recombined E. tiantaiensis as Prismatoolithus tiantaiensis. [16] In 2016, Tanaka et al. also moved E. chichengensis and E. laijiaensis, as well as E. chimeiensis and E. jianchangensis (which had been named by Fang et al. in 2007 [22] ) to Prismatoolithidae. [7]

Related Research Articles

<i>Dendroolithus</i> Oogenus of dinosaur egg

Dendroolithus is an oogenus of Dendroolithid dinosaur egg found in the late Cenomanian Chichengshan Formation, in the Gong-An-Zhai and Santonian Majiacun Formations of China and the Maastrichtian Nemegt and Campanian Barun Goyot Formation of Mongolia. They can be up to 162 mm long and 130 mm wide. These eggs may have been laid by a Therizinosaur, Sauropod, or Ornithopod. The oospecies "D." shangtangensis was originally classified as Dendroolithus, however, it has since been moved to its own distinct oogenus, Similifaveoloolithus. This oogenus is related with embryos of the theropod Torvosaurus

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>Macroelongatoolithus</i> Oogenus of dinosaur egg

Macroelongatoolithus is an oogenus of large theropod dinosaur eggs, representing the eggs of giant caenagnathid oviraptorosaurs. They are known from Asia and from North America. Historically, several oospecies have been assigned to Macroelongatoolithus, however they are all now considered to be a single oospecies: M. carlylensis.

<i>Macroolithus</i> Oogenus of dinosaur 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 Fenshui'ao Formation of 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.

Ageroolithus is an oogenus of dinosaur egg. It may have been laid by a theropod.

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.

<i>Styloolithus</i> Oogenus of fossil egg

Styloolithus is an oogenus of highly distinctive fossil egg from the Upper Cretaceous Djadokhta Formation and the Barun Goyot Formation in Mongolia.

<span class="mw-page-title-main">Elongatoolithidae</span> Oofamily of dinosaur eggs

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.

Guegoolithus is an oogenus of fossil egg from the early Cretaceous of Spain. It is classified in the oofamily Spheroolithidae, and was probably laid by an ornithopod dinosaur.

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.

Tubercuoolithus is an oogenus of dinosaur egg from the early Campanian of Montana.

Nipponoolithus is an oogenus of fossil egg native to Japan. It is one of the smallest known dinosaur eggs, and was probably laid by some kind of non-avian maniraptor.

<i>Gobioolithus</i> Fossil bird egg native to Mongolia

Gobioolithus is an oogenus of fossil bird egg native to Mongolia. They are small, smooth-shelled, and elongated eggs that were first discovered in the 1960s and early 70s during a series of fossil-hunting expeditions in the Gobi desert. Two oospecies have been described: Gobioolithus minor and G. major. The eggs were probably laid in colonial nesting sites on the banks of rivers and lakes.

Nanhsiungoolithus is an oogenus 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.

References

  1. 1 2 3 4 5 6 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: 5–80.
  2. 1 2 3 4 5 Simon, D. J. (2014). "Giant Dinosaur (theropod) Eggs of the Oogenus Macroelongatoolithus (Elongatoolithidae) from Southeastern Idaho: Taxonomic, Paleobiogeographic, and Reproductive Implications." (Doctoral dissertation, Montana State University, Bozeman).
  3. 1 2 3 4 5 6 7 8 Mikhailov, Konstantin K.E. (1994). "Theropod and protoceratopsian dinosaur eggs from the Cretaceous of Mongolia and Kazakhstan". Paleontological Journal. 28 (2): 101–120.
  4. 1 2 3 4 5 Carpenter, Kenneth (1999). Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past), Indiana University Press; ISBN   0-253-33497-7.
  5. 1 2 3 4 5 6 7 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.
  6. 1 2 3 Yang, Zhongjian (1965). "Fossil eggs from Nanhsiung, Kwangtun and Kanchou, Kiangsi" (PDF). Vertebrata PalAsiatica. 9 (2): 141–170.
  7. 1 2 3 Tanaka, Kohei; Zelenitsky, Darla; Saegusa, Haruo; Ikeda, Tadahiro; DeBuhr, Christopher; Therrien, François (2016). "Dinosaur eggshell assemblage from Japan reveals unknown diversity of small theropods". Cretaceous Research. 57: 350–363. Bibcode:2016CrRes..57..350T. doi:10.1016/j.cretres.2015.06.002.
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  9. ↑ Zhao, Zikui (1979). "Progress in the Research of Dinosaur Eggs" (PDF). Mesozoic and Cenozoic Red Beds of South China. Selected Papers from the "Cretaceous-Tertiary Workshop," Nanxiong, Guangdong Province. Institute of Vertebrate Paleontology, Paleoanthropology & Nanjing Institute of Paleontology Science Press: 330–340.
  10. 1 2 3 Zeng, Demin; Zhang, Jinjian (1979). "On the dinosaurian eggs from the western Dongting Basin, Hunan" (PDF). Vertebrata PalAsiatica. 17 (2): 131–136.
  11. 1 2 Yu, Xinqi (1998). "Characteristics of Dinosaur Fossil from Southern Anhui and their significance for stratigraphic division". Regional Geology of China (in Chinese). 17 (3): 278–284.
  12. ↑ Varricchio, David; Moore, Jason; Erickson, Gregory; Norell, Mark; Jackson, Frankie; Borkowski, John (2008). "Avian Paternal Care Had Dinosaur Origin". Science. 322 (5909): 1826–1828. Bibcode:2008Sci...322.1826V. doi: 10.1126/science.1163245 . PMID   19095938. S2CID   8718747.
  13. 1 2 Yang, Zhongjian (1954). "Fossil Reptilian Eggs from Laiyang, Shantung, China". Acta Scientia Sinica. 3: 505–522. doi:10.1360/ya1954-3-4-505 (inactive 31 January 2024).{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link)
  14. ↑ Sato, Tamaki; Cheng, Yen-nien; Wu, Xiao-chun; Zelenitsky, Darla; Hsiao, Yu-fu (2005). "A Pair of Shelled Eggs Inside A Female Dinosaur" (PDF). Science. 308 (5720): 375. doi:10.1126/science.1110578. PMID   15831749. S2CID   19470371.
  15. 1 2 Tanaka, Kohei; Zelenitsky, Darla K.; Therrien, François (2015). "Eggshell Porosity Provides Insight on Evolution of Nesting in Dinosaurs". PLOS ONE. 10 (11): e0142829. Bibcode:2015PLoSO..1042829T. doi: 10.1371/journal.pone.0142829 . PMC   4659668 . PMID   26605799.
  16. 1 2 Wang, Qiang; Zhao, Zikui; Wang, Xiaolin; Jiang, Yan'gen (2011). "New ootypes of dinosaur eggs from the Late Cretaceous in Tiantai Basin, Zhejiang Province, China" (PDF). Vertebrata PalAsiatica. 49 (4): 446–449.
  17. ↑ Mikhailov, Konstantin (1991). "Classification of fossil eggshells of amniotic vertebrates" (PDF). Acta Palaeontologica Polonica. 36 (2): 193–238.
  18. ↑ Norell, Mark A.; Clark, James M.; Demberelyin, Dashzeveg; Rhinchen, Barsbold; Chiappe, Luis M.; Davidson, Amy R.; McKenna, Malcolm C.; Altangerel, Perle; Novacek, Michael J. (1994). "A Theropod Dinosaur Embryo and the Affinities of the Flaming Cliffs Dinosaur Eggs". Science. 266 (5186): 779–782. Bibcode:1994Sci...266..779N. doi:10.1126/science.266.5186.779. JSTOR   2885545. PMID   17730398. S2CID   22333224.
  19. ↑ Fang, Xiaosi; Wang, Yaozhong; Jiang, Yang'en (2000). "On the Late Cretaceous Fossil Eggs of Tiantai, Zhejiang". Geological Review. 46 (1): 105–112.
  20. ↑ Fang, Xiaosi; Lu, Liwu; Jiang, Yan'gen; Yang, Liangfeng (2003). "Cretaceous fossil eggs from the Tiantai basin of Zhejiang, with a discussion on the extinction of dinosaurs". Geological Bulletin of China. 22 (7): 512–520.
  21. ↑ Wang, Qiang; Wang, Xiaolin; Zhao, Zikui; Jiang, Yan'gen (2010). "A new oogenus of Elongatoolithidae from the Upper Cretaceous Chichengshan Formation of Tiantai Basin, Zhejiang Province" (PDF). Vertebrata PalAsiatica. 48 (2): 111–118.
  22. ↑ Fang, Xiaosi; Zhang, Zhijun; Pang, Qiqing; Li, Peixian; Han, Yingjian; Xie, Honliang; Yan, Ronghao; Pang, Fengjiu; Lu, J; Cheng, Zhengwu (2007). "Cretaceous strata and egg fossils in Xixia, Henan Province". Acta Geoscientia Sinica. 28 (2): 123–142.
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