Liaoningosaurus

Liaoningosaurus is an unusual genus of ankylosaurian dinosaurs from the Early Cretaceous period of China. It contains a single species, Liaoningosaurus paradoxus, and is represented by two fossil specimens collected from the Yixian Formation (Aptian age) of Liaoning Province. L. paradoxus was unusual among advanced ornithischian dinosaurs in that it is speculated to have hunted or scavenged, with preserved gut contents showing that it may have eaten fish. Additionally, some features of its skeleton may suggest that it was partially aquatic.[1]

The type species L. paradoxus was named by Xu Xing, Wang Xiaolin and You Hailu in 2001. The generic name refers to Liaoning. The specific name refers to the confusing mix of nodosaurid and ankylosaurid features shown by the specimen.

Liaoningosaurus
Temporal range: Early Aptian, 122 Ma
Liaoningosaurus-Beijing Museum of Natural History
Liaoningosaurus holotype
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ankylosauria
Family: Ankylosauridae
Genus: Liaoningosaurus
Xu et al. 2001
Species:
L. paradoxus
Binomial name
Liaoningosaurus paradoxus
Xu et al. 2001

Description

The holotype IVPP V12560 is an articulated skeleton measuring approximately 34 centimetres (13 in) in length. The specimen is unique among all known ankylosaur fossils in the retention of the external mandibular fenestra. Antorbital fenestrae may also be present. It has relatively large teeth, including teeth in the praemaxilla ( primitive or possibly juvenile trait). The points on the tooth crown were unusually long and sharp, giving each tooth a fork-like shape. It had long feet, long lower legs, and long, sharp claws on the hands and feet, unlike the blunt claws of other ankylosaurians. All of these were initially interpreted as juvenile features, given the specimen's small size and lack of fusion between the spine and hip bones.[2] However, information from a second specimen has led some scientists to conclude that the lack of hip fusion and long limbs and toes are in fact adaptations to a semiaquatic lifestyle. The large, fork-like teeth and sharp claws may have been adapted to catch fish and other small animals. Stomach contents recovered with the second L. paradoxus specimen show that fish may have formed part of the animal's diet.[1] This indicates that Liaoningosaurus could have been either carnivorous or at least omnivorous, making it the first ornithischian thought to have adapted to such a lifestyle, though this is also suspected in more basal ornithischians like heterodontosaurs[3] and now in pachycephalosaurids [4]

Another supposedly unique feature originally identified from the type specimen was the presence of armor plating on the belly. A large segment of what appeared to be the bone from a flat osteoderm covered the underside of the abdomen. This had a surface structure covered with small hexagonal and rhombic bumps. Such plates had never been found with other ankylosaurians, and it has been suggested that, if L. paradoxus was indeed semiaquatic, the belly plates may have protected it from predators attacking from below, as in modern turtles.[1] Smaller triangular osteoderms were found on the shoulder, including a small shoulder spike.[2] However, closer examination of the bumps seemed to suggest that they were not sculpted onto a single piece of bone, but instead resembled normal dinosaurian scales. The broken edges of the supposed plates, when studied in 2013 by paleontologist Victoria Arbour and colleagues, did not reveal any internal structure as would be expected from a piece of bone. Arbour and colleagues concluded that the "belly plates" were likely to be pieces of preserved skin.[5]

Relationships

Determining the relations of Liaoningosaurus is difficult because of the young age of the individual specimen and the presence of traits both typical of ankylosaurids and nodosaurids. Xu et al. published a cladistic analysis in 2001, placing Liaoningosaurus as an early branch within the Nodosauridae,[2] while Vickaryous et al. provisionally assigned it to the Ankylosauria incertae sedis in 2004.[6] A second cladistic analysis performed by Thompson et al. in 2011 suggested that Liaoningosaurus is a very basal ankylosaurid.[7]

See also

References

  1. ^ a b c Ji Q., Wu X., Cheng Y., Ten F., Wang X., and Ji Y. 2016. Fish-hunting ankylosaurs (Dinosauria, Ornithischia) from the Cretaceous of China. Journal of Geology, 40(2).
  2. ^ a b c Xu X., Wang X.-L., and You H.-L. (2001). "A juvenile ankylosaur from China". Naturwissenschaften, 88(7): 297-300.
  3. ^ "Armored dinosaur was a fish-eating turtle-mimic".
  4. ^ Pickrell, John (2018-08-24). "Vegetarian dinosaur may have actually eaten meat, skull suggests". National Geographic. Retrieved 2018-09-08.
  5. ^ Arbour, V. M., Burns, M. E., Bell, P. R., & Currie, P. J. (2014). Epidermal and dermal integumentary structures of ankylosaurian dinosaurs. Journal of Morphology, 275(1): 39-50. doi:10.1002/jmor.20194
  6. ^ Vickaryous, Maryanska, and Weishampel (2004). "Ankylosauria". in The Dinosauria (2nd edition), Weishampel, D. B., Dodson, P., and Osmólska, H., editors. University of California Press.
  7. ^ Richard S. Thompson; Jolyon C. Parish; Susannah C. R. Maidment; Paul M. Barrett (2011). "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology. 10 (2): 301–312. doi:10.1080/14772019.2011.569091.
Acantholipan

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Ankylosauridae

Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. Ankylosaurids appeared 122 million years ago and went extinct 66 million years ago during the Cretaceous–Paleogene extinction event. These animals were mainly herbivorous and were obligate quadrupeds, with leaf-shaped teeth and robust, scute-covered bodies. Ankylosaurids possess a distinctly domed and short snout, wedge-shaped osteoderms on their skull, scutes along their torso, and a tail club.Ankylosauridae is exclusively known from the northern hemisphere, with specimens found in western North America, Europe, and East Asia. The first discoveries within this family were of the genus Ankylosaurus, by Peter Kaiser and Barnum Brown in Montana in 1906. Brown went on to name Ankylosauridae and the subfamily Ankylosaurinae in 1908.

Ankylosaurinae

Ankylosaurinae is a subfamily of ankylosaurid dinosaurs, existing from the Early Cretaceous about 105 million years ago until the end of the Late Cretaceous, about 66 mya. Many genera are included in the clade, such as Ankylosaurus, Pinacosaurus, Euoplocephalus, and Saichania.

Aptian

The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.The Aptian partly overlaps the upper part of the regionally used (in Western Europe) stage Urgonian.

The Selli Event, also known as OAE1a, was one of two oceanic Anoxic events in the Cretaceous period, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years. The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma.

Barremian

The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch (or Lower Cretaceous series). It is preceded by the Hauterivian and followed by the Aptian stage.

Bienosaurus

Bienosaurus (meaning "Bien's lizard") is a genus of thyreophoran dinosaur from the Lower Jurassic (probably Sinemurian) Lower Lufeng Formation in Yunnan Province in China.

Bissektipelta

Bissektipelta is a genus of herbivorous ankylosaurid dinosaur from the Upper Cretaceous of Uzbekistan. Bissektipelta is monospecific, containing only the species B. archibaldi.

Craterosaurus

Craterosaurus (meaning krater reptile or bowl reptile) was a genus of stegosaurid dinosaur. It lived during the Early Cretaceous (Valanginian to Barremian stages) around 145-136 million years ago. Its fossils were found in the Woburn Sands Formation of England. Craterosaurus may actually be a junior synonym of Regnosaurus, but only one fossil, a partial vertebra, was recovered.

The type (and only known) species is Craterosaurus pottonensis, described in 1874 by Harry Seeley. The specific name refers to the Potton bonebed. Seeley mistook the fossil, holotype SMC B.28814, for the base of a cranium. Franz Nopcsa in 1912 correctly identified it as the front part of a neural arch. Craterosaurus was placed in Stegosauria by Galton, although subsequent authors did not recognize Craterosaurus as a distinct, valid taxon.

Dongyangopelta

Dongyangopelta is an extinct genus of nodosaurid ankylosaurian dinosaur known from the "middle" Cretaceous Chaochuan Formation (Albian or Cenomanian stage) of Dongyang, Zhejiang Province, China. Dongyangopelta was first named by Rongjun Chen, Wenjie Zheng, Yoichi Azuma, Masateru Shibata, Tianliang Lou, Qiang Jin and Xingsheng Jin in 2013 and the type species is Dongyangopelta yangyanensis. It differs from Zhejiangosaurus, the second nodosaurid from southeast China, in the characters of presacral rod, ilium, and femur. Donyangopelta is distinguishable from Zhejiangosaurus only on the basis of the morphology of its pelvic shield.

Invictarx

Invictarx is a genus of herbivorous nodosaurid dinosaur from New Mexico dating from the early Campanian epoch of the Late Cretaceous.

Loricatosaurus

Loricatosaurus (meaning "armored lizard") is a dinosaur of Stegosauridae family from Callovian-age (Middle Jurassic) rocks of England and France.

Mongolostegus

Mongolostegus is a genus of stegosaur from the Early Cretaceous (Aptian-Albian) of Mongolia. The type and only species is M. exspectabilis, known from a single specimen previously under the nomen nudum Wuerhosaurus mongoliensis.

Nodosaurus

Nodosaurus (meaning "knobbed lizard") is a genus of herbivorous ankylosaurian dinosaur from the Late Cretaceous, the fossils of which are found in North America.

Silvisaurus

Silvisaurus, from the Latin silva "woodland" and Greek sauros "lizard", is a nodosaurid ankylosaur from the middle Cretaceous period.

Tatisaurus

Tatisaurus is a genus of ornithischian dinosaur from the Early Jurassic from the Lower Lufeng Formation in Yunnan Province in China. Little is known as the remains are fragmentary.

Texasetes

Texasetes (meaning "Texas resident") is a genus of ankylosaurian dinosaurs from the late Lower Cretaceous of North America. This poorly known genus has been recovered from the Paw Paw Formation (late Albian) near Haslet, Tarrant County, Texas, which has also produced the nodosaurid ankylosaur Pawpawsaurus. Texasetes is estimated to have been 2.5–3 m (8–10 ft) in length. It was named by Coombs in 1995.

Tianzhenosaurus

Tianzhenosaurus (Tianzhen + Greek sauros="lizard") is a genus of ankylosaurid dinosaurs discovered in Tianzhen County, at Kangdailiang near Zhaojiagou Village, in Shanxi Province, China, in the Late Cretaceous Huiquanpu Formation. Thus far, a virtually complete skull and postcranial skeleton have been assigned to the genus, which is monotypic (T. youngi Pang & Cheng, 1998).

This was a medium-sized ankylosaurian, the skull measuring 28 cm (11 in) in length, with a total body length around 4 m (13 ft).

Vickaryous et al. (2004) placed Tianzhenosaurus within the Ankylosauridae, nested as the sister group to Pinacosaurus. Some authors have suggested that Tianzhenosaurus is actually a junior synonym of Saichania chulsanensis.

Tsagantegia

Tsagantegia (; meaning "of Tsagan-Teg"; Tumanova, 1993) is a genus of medium-sized ankylosaurid dinosaur from the Late Cretaceous of Mongolia, during the Cenomanian stage.

The holotype specimen (GI SPS N 700/17), a complete skull, was recovered from the Bayan Shireh Formation (Cenomanian-Santonian), at the Tsagan-Teg ("White Mountain") locality, Dzun-Bayan, in the southeastern Gobi Desert, Mongolia. The genus is monotypic, including only the type species, T. longicranialis.

Yingshanosaurus

Yingshanosaurus (meaning "Yingshan or Golden Hills reptile") is a genus of stegosaurian dinosaur from the Late Jurassic, around 155 million years ago. It was a herbivore that lived in what is now China. The type species is Yingshanosaurus jichuanensis.

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