''Nanhsiungoolithus'' is an

oogenus 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 ...

(fossil-egg genus) of

dinosaur egg Dinosaur eggs are the organic vessels in which a dinosaur embryo develops. When the first scientifically documented remains of non-avian dinosaurs were being described in England during the 1820s, it was presumed that dinosaurs had laid eggs bec ...

from the

late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. It belongs to the oofamily

Elongatoolithidae Elongatoolithidae is an oofamily of fossil eggs, representing the eggs of oviraptorosaurs (with the exception of the avian '' Ornitholithus''). They are known for their highly elongated shape. Elongatoolithids have been found in Europe, Asia, and ...

, which means that it was probably laid by an

oviraptorosaur Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period (geology), Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like s ...

, 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.

Description

The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

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. Like other elongatoolithids, the eggs are found arranged in a circular pattern. The eggs are long and narrow, with an average length of and width of . 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. The eggshell of ''Nanhsiungoolithus'' is on average just under 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. However, in ''Nanhsiungoolithus'', the units are not fully fused and can still be seen as distinct columns. Since the embryo must breathe, eggshells such as ''Nanhsiungoolithus'' have pores to allow for gas exchange. 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.

Parenting behavior

While no fossils of ''Nanhsiungoolithus'' have been found associated with a parent, multiple fossils confirm that elongatoolithid eggs were laid by

oviraptorosaurian Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or wi ...

dinosaurs, who sat on their nests to incubate the eggs. Unlike some other dinosaurs, oviraptorosaurian parents did not bury their eggs.

Classification

Fossilized eggs are classified by a parataxonomic system similar to

Linnaean taxonomy Linnaean taxonomy can mean either of two related concepts: # The particular form of biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his ''Systema Naturae'' (1735) and subsequent works. In the taxonomy of Linnaeus t ...

. According to this system, ''Nanhsiungoolithus'' is an oogenus in the oofamily Elongatoolithidae. Along with ''

Macroolithus ''Macroolithus'' is an oogenus (fossil-egg genus) 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 ...

'' and ''

Elongatoolithus ''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 thei ...

'', it was the first oogenus ever given a formal parataxonomic name; it is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

oogenus, with the single oospecies ''N. chuetienensis''.

History

''Nanhsiungoolithus'' eggs were first discovered in Southern China by the pioneering Chinese paleontologist

Yang Zhongjian Yang Zhongjian, also Yang Chung-chien (; 1 June 1897 – 15 January 1979), courtesy name Keqiang (), also known as C.C. (Chung Chien) Young, was a Chinese paleontologist and zoologist. He was one of China's foremost vertebrate paleontologists. H ...

. In 1965, he described several types of eggs from

Nanxiong Nanxiong (), historically Namyung, Namhung, and Nanhsiung, is a county-level city of northern Guangdong province, People's Republic of China, bordering Jiangxi to the north, east and southeast. It is under the administration of Guangdong Gua ...

(Nanhsiung) in Guangdong, including two partial nests that would later be classified in ''Nanhsiungoolithus''. He described them as members of the type ''"Oolithes" elongatus''. 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. ''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 Henan (; or ; ; alternatively Honan) is a landlocked province of China, in the central part of the country. Henan is often referred to as Zhongyuan or Zhongzhou (), which literally means "central plain" or "midland", although the name is al ...

. 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 The Majiacun Formation is a Santonian to Coniacian geologic Formation (geology), formation in China. * ''Zhanghenglong, Zhanghenglong yangchengensis''Xing et al., 2014 * Baryonychinae, Baryonychinae indet.? (possibly an indeterminate theropod due ...

as ''Nanhsiungoolithus chuetienensis''.

Distribution and paleoecology

''Nanhsiungoolithus'' is fairly rare, and has only been found in

Guangdong Guangdong (, ), alternatively romanized as Canton or Kwangtung, is a coastal province in South China on the north shore of the South China Sea. The capital of the province is Guangzhou. With a population of 126.01 million (as of 2020) ...

and

, 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 The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

, alongside ''Macroolithus'', ''Elongatoolithus'', ''Apheloolithus'', ''

Prismatoolithus ''Prismatoolithus'' is an oogenus of dinosaur egg from the Cretaceous (Hauterivian-Maastrichtian) and possibly also the earliest Paleocene. They likely belonged to troodontids Troodontidae is a clade of bird-like theropod dinosaurs. During m ...

'', '' Stromatoolithus'', ''

Ovaloolithus ''Ovaloolithus'' is an oogenus of dinosaur egg. Eggs of the genus have been found in China, Mongolia and Utah. Species Oospecies attributed to this genus include:Shixingoolithus''. The fossils in

are found at the

, which is slightly older, dating from the

Coniacian The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by t ...

to the

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. The ...

, and represents the depositions of a meandering stream system.

References

{{Taxonbar, from=Q6964245 Elongatoolithids Cretaceous China Fossils of China Fossil parataxa described in 1975