Parvoblongoolithus

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Parvoblongoolithus
Temporal range: Maastrichtian
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Egg fossil classification Red Pencil Icon.png
Oofamily: incertae sedis
Oogenus:†Parvoblongoolithus
Oospecies
  • †P. jinguoensis Zhang et al. 2015 (type)

Parvoblongoolithus is an oogenus of fossil dinosaur egg whose small size and unusual shape suggest the possibility that it is a dwarf egg. [1]

Dinosaur egg

Dinosaur eggs are the organic vessels in which a dinosaur embryo develops. When the first scientifically documented remains of dinosaurs were being described in England during the 1820s, it was presumed that dinosaurs had laid eggs because they were reptiles. In 1859, the first scientifically documented dinosaur egg fossils were discovered in France by Jean-Jacques Poech, although they were mistaken for giant bird eggs. The first scientifically recognized dinosaur egg fossils were discovered in 1923 by an American Museum of Natural History crew in Mongolia. Since then many new nesting sites have been found all over the world and a system of classification based on the structure of eggshell was developed in China before gradually diffusing into the West. Dinosaur eggshell can be studied in thin section and viewed under a microscope. The interior of a dinosaur egg can be studied using CAT scans or by gradually dissolving away the shell with acid. Sometimes the egg preserves the remains of the developing embryo inside. The oldest known dinosaur eggs and embryos are from Massospondylus, which lived during the Early Jurassic, about 190 million years ago.

A cock egg, cock's egg, dwarf egg, or witch egg is a small usually yolkless egg. Such eggs are sometimes also called wind eggs, but this term more often refers to eggs without a shell or with a soft shell and less often to eggs that are rotten or unimpregnated.

Contents

Distribution

The sole known Parvoblongoolithus jinguoensis specimen was found in the Upper Cretaceous Chichengshan Formation in Tiantai County, Zhejiang. [1]

Tiantai County County in Zhejiang, Peoples Republic of China

Tiantai County is located in Taizhou, Zhejiang Province, People's Republic of China.

Zhejiang Province

Zhejiang is an eastern coastal province of China. Zhejiang is bordered by Jiangsu and Shanghai to the north, Anhui to the northwest, Jiangxi to the west, and Fujian to the south. To the east is the East China Sea, beyond which lie the Ryukyu Islands of Japan.

Description

Parvoblongoolithus known from only a single specimen. It is relatively small (measuring 45.5 mm (1.79 in) long by 34.4 mm (1.35 in) wide) with an asymmetrical shape, similar to modern bird eggs. The eggshell is 1.12 mm thick, with the barrel-shaped cones of the mammillary layer making up one-fifth of the total eggshell thickness. The pore system is prolatocanaliculate, meaning the pores vary in width along their length. The pore canals are thick and irregularly shaped. The outer surface of the eggshell is smooth. [1]

Despite having a bird-like shape and size, the P. jinguoensis has a very different microstructure, which bears a closer resemblance to non-avian dinosaur eggs than bird eggs. [2] Most significantly, all known Cretaceous bird eggs have a three-layered eggshell, whereas the eggshell of Parvoblongoolithus is two-layered. Additionally, its pore system is prolatocanaliculate, unlike the angusticanaliculate pores of bird eggs (such as Laevisoolithidae or Gobioolithidae) and its microstructures are much more similar to those of stalicoolithids, Mosaicoolithus , and Paraspheroolithus . [1]

Laevisoolithidae is an oofamily of fossil egg belonging to the Ornithoid-ratite Morphotype. Their eggshells are smooth and very thin, typically less than a millimeter thick. Laevisoolithids may be the eggs of Enantiornithid birds.

Stalicoolithidae is an oofamily of fossil eggs.

Mosaicoolithus is an oogenus of fossil egg from Tiantai County, Zhejiang Province in China. Its classification is uncertain. The eggs are spherical, and 8.8 cm in diameter. It is distinctive for having irregular pore canals, sometimes filled by secondary shell units. Originally, it was classified as two separate oospecies of Spheroolithus: S. zhangtoucaoensis and S. jincunensis. However, these oospecies were synonymized and placed into a new oogenus by Wang et al. (2011).

Palaeobiology

Since no skeletal remains were associated with its remains, the parentage of Parvoblongoolithus is unknown. However, its microstructure suggests it was laid by some kind of non-avian dinosaur, related to the parents of Stalicoolithidae, Paraspheroolithus, or Mosaicoolithus. [1]

Bird Warm-blooded, egg-laying vertebrates with wings, feathers and beaks

Birds, also known as Aves or avian dinosaurs, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich. They rank as the world's most numerically-successful class of tetrapods, with approximately ten thousand living species, more than half of these being passerines, sometimes known as perching birds. Birds have wings which are more or less developed depending on the species; the only known groups without wings are the extinct moa and elephant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in flightless birds, including ratites, penguins, and diverse endemic island species of birds. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming.

Parvoblongoolithus is remarkable for having an extremely thick shell (as thick as the shell of titanosaur eggs) despite being significantly smaller than its close relatives. This would have made it much more difficult for a baby dinosaur to break out of the egg without parental assistance. It is possible that Parvoblongoolithus actually represents a fossil dwarf egg, a type of deformity occasionally observed in modern birds when a disturbance of the oviducts causes them to form a small, deformed egg. This would explain both the thick eggshell and unique shape of P. jinguoensis. [1]

Parataxonomy

Parvoblongoolithus has not been classified into any oofamily. The eggshell resembles the spherulitic type, but it lacks the radial-tabular ultrastructure. [1] It is closely related to Paraspheroolithus, Mosaicoolithus, and stalicoolithids. [1]

Related Research Articles

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References

  1. 1 2 3 4 5 6 7 8 Zhang, Shuakang; Jin, Xingsheng; O'Conner, Jingmai K.; Wang, Min; Xie, Junfang (2015). "A new egg with avian egg shape from the Upper Cretaceous of Zhejiang Province, China". Historical Biology . 27 (5): 595–602. doi:10.1080/08912963.2014.902451.
  2. ↑ "New dinosaur egg with avian egg shape discovered from the Upper Cretaceous of Zhejiang Province, China". phys.org. 28 May 2014. Retrieved 27 March 2016.
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