Sinosaurus

*Sinosaurus triassicus*

***Sinosaurus*** (meaning "Chinese lizard") was a tetanuran theropod dinosaur, which is 5.6 meters long dilophosaurid from Early Jurassic China, 199 to 196 mya. It lived in China along another possible dilophosaurid, *Lukosaurus*.

## Diet

Sinosaurus is thought be a generalist, that ate wide variety of prey items, such as fish as well as meat, much like Dilophosaurus itself. Sinosaurus is interpreted to be more of a predator. It may possibly preyed upon the possible ankylosaur *Bienosaurus*, the scutellosaurid *Tatisaurus*, the prosauropods *Lufengosaurus* and the sauropods *Kunmingosaurus* and therapsids.

The skull of *Sinosaurus* has a deep notch between the premaxilla and maxilla. Dong (2003) proposed that the notch was used to house jaw muscles, giving *Sinosaurus* a powerful bite. Based on the estimated power of its jaws, *Sinosaurus* might have either been a carnivore or a scavenger. Dong suspected that the premaxilla was covered in a narrow, hooked beak, that was used to rip open skin and abdominal flesh. He also thought that the crest would have been used to hold open the abdominal cavity while feeding. Dong studied the feet of *Sinosaurus* as well, finding a resemblance with the feet of modern vultures. The feet of *Sinosaurus* were probably adapted to help it feed on large-bodied animals, such as prosauropods.

A study by Xing et al. (2013) examined the effect of the traumatic loss of teeth on the dental alveolus (the socket in the jaw where the roots of teeth are held) in dinosaurs. *Sinosaurus* is the first dinosaur where remodeling of the alveolus in the jaw was observed. The authors concluded that this finding "contributes to mounting evidence suggesting theropods were highly resilient to a broad spectrum of traumas and diseases.

## Description

The composite term *Sinosaurus* comes from Sinae, the Latin word for the Chinese, and the Greek word sauros (σαυρος) meaning "lizard"; thus "Chinese lizard". The specific name, *triassicus*, refers to the Triassic, the period that the fossils were originally thought to date from. *Sinosaurus* was described and named by Chung Chien Young, who is known as the 'Father of Chinese Vertebrate Paleontology', in 1940.

According to Carrano et al. (2012) *D. sinensis*, now considered to be at least congeneric with *Sinosaurus triassicus*, can be distinguished based on the fact that a vertical groove is present on the lateral premaxilla adjacent to contact with the maxilla.  *Sinosaurus* is the only "dilophosaurid" known from a complete braincase. *Cryolophosaurus*, *Dilophosaurus*, *Zupaysaurus*, and *Coelophysis kayentakatae* are all known from partial braincases.

Two partial braincases were found before 2012, and are probably mostly complete, except that large sections are obscured by sediments. In 2011, an exceptionally well-preserved braincase was found, only missing the frontal bones and orbitosphenoid.

Originally thought to be a coelophysoid related to *Dilophosaurus* and *Cryolophosaurus*, Oliver Rauhut in 2003 showed *Sinosaurus* to be a more advanced theropod, related to *Cryolophosaurus* and "*Dilophosaurus" sinensis*. In 2013, in an unpublished work, Carano agreed that *Sinosaurus* is a theropod. *Sinosaurus* has been considered a nomen dubium in a few works, although now that "*Dilophosaurus" sinensis* is referred to it, it is considered valid.

## Discovery and naming

KMV 8701 was originally discovered in 1987. The specimen was identified as a new species, and was named *Dilophosaurus sinensis*. Then in 1994, during a field expedition, a more complete specimen was found, and was assigned to the same species. In 2003, Dong Zhiming studied the material of *Sinosaurus*, finding it to be quite similar to *Dilophosaurus sinensis*. As *Sinosaurus* was named earlier, by Young in 1948, *"Dilophosaurus" sinensis* became its junior synonym.

Over the years, paleontologists referred additional specimens to *D. sinensis* which are now assigned to *Sinosaurus*. Dong (2003) referred specimen LDM-LCA10 which consists of a skull and an incomplete skeleton.[1] In 2012, Xing referred two individuals, ZLJ0003 which consists of a partial skull and an incomplete skeleton, and ZLJT01 which is a juvenile individual that consists of a premaxillary fragment, an incomplete maxilla, a maxillary fragment, a lacrimal, both frontals, both parietals, an incomplete braincase, an incomplete dentary, an atlantal intercentrum, two dorsal rib fragments, and a partial proximal caudal neural arch, to *Sinosaurus*.

The holotype, IVPP V34, was found in the Lower Lufeng Formation, and consists of two maxillary (upper jaw) fragments, four maxillary teeth, and a lower jaw fragment with three teeth. The teeth are laterally compressed, and feature fine serrations both at their anterior and posterior edges. The teeth are also variable in size and are curved backwards. This material is too fragmentary to determine the length and weight of this dinosaur. Over the years, other fossils were referred to *Sinosaurus*, some of which were material that was shown to belong to two prosauropods. The fossils include a postcrania,[6] with a sacrum with three preserved sacral vertebrae. The material assigned to *"Sinosaurus postcrania"* includes a mix of plateosaurid and melanorosaurid elements. All the material from the Red Beds block has now been reassigned to *Jingshanosaurus*.

Shaojin Hu (1993) assigned specimen KMV 8701 to *Dilophosaurus sinensis*. In 2013, a study by Currie et al., confirmed that *D. sinensis* was the same animal as *Sinosaurus triassicus*. Specimen KMV 8701 consists of a skull (measuring 525 mm), and is nearly complete. The specimen KMV 8701 is about 5.6 m (18 ft) long, meaning *Sinosaurus* was about that length. KMV 8701 has been assigned now to *Sinosaurus*, but the specimen still lacks sufficient description and preparation. In 2012, a new specimen of *Sinosaurus* was described, and was found to represent a new species.

## Classification

Originally thought to be a coelophysoid related to *Dilophosaurus* and *Cryolophosaurus*, Oliver Rauhut in 2003 showed *Sinosaurus* to be a more advanced theropod, related to *Cryolophosaurus* and "Dilophosaurus" *sinensis*. In 2013, in an unpublished work, Carano agreed that *Sinosaurus* is a theropod. *Sinosaurus* has been considered a *nomen dubium* in a few works, although now that "Dilophosaurus" *sinensis* is referred to it, it is considered valid.

*Dilophosaurus sinensis* was shown to be a junior synonym of *Sinosaurus* in 2003. It is possibly closer to the Antarctic theropod *Cryolophosaurus*, based on the fact that the anterior end of the jugal does not participate in the internal antorbital fenestra and that the maxillary tooth row is completely in front of the eye socket. *D. sinensis* was exhibited in 1998 at Dinofest in Philadelphia. Although the skull of *D. sinensis* sports large nasolacrimal crests superficially like those reconstructed in *D. wetherilli*, features elsewhere in the skeleton suggest it is closer to tetanuran theropods. Rauhut (2003) regarded *D. sinensis* as a basal tetanuran most closely related to *Sinosaurus* and *Cryolophosaurus*. Lamanna *et al.* (1998b) examined the material ascribed to *D. sinensis* and found it to be synonymous with *Sinosaurus triassicus*. This cladistic finding was confirmed in 2003 by Dong.

The Lufeng Dinosaurian Museum discovered a new specimen of *Sinosaurus* (ZLJT01) in 2007 from the Lufeng Basin. It consists of an incomplete skull and other postcranial fragments. Phylogenetic analysis of this specimen, demonstrates that *Sinosaurus* is a more derived theropod, and is not the most basal dilophosaurid, as held by Smith et al. A cladogram was identified by Christophe Hendrickx and Octávio Mateus. It placed *Sinosaurus* and *Cryolophosaurus* in a polytomy at the base of Tetanurae.

Recent studies placed *Sinosaurus* outside the Ceratosauria+Tetanurae clade, while Wang *et al*. (2016) considered it the basalmost ceratosaur.

## Paleobiology

A deep notch between the maxilla and premaxilla was suggested by Dong (2003) to hold jaw muscles in life that would have produced a powerful bite. Some suggest it could have been either a predator or a scavenger. Some have suggested that "dilophosaurid" jaws were adapted to piscivory and also to generalism. There is not yet a concrete answer. Dong had suspected the premaxilla was sheathed in a narrow, hooked beak that could tear open skin, and thought the crest was used to hold the abdominal walls open during feeding. Dong also saw similarity in the feet to vultures, finding they were likely adapted to feeding on large prey such as prosauropods. Xing et al. (2013) examined traumatic teeth loss in dental alveoli, where remodeling and disease resilience was documented. The dental alveolus is the first dental pathology recorded in dinosaurs.

## JPInstitute.com Description

Sinosaurus was a very large meat-eater that lived in China at the beginning of the Jurassic period. Since the only parts of this dinosaur ever discovered are teeth and a small piece of its upper jaw, it is hard to know exactly what it looked like. It was probably one of the first large meat-eaters to live in Asia.

There is a great deal of uncertainty regarding the material associated with this genus. Some material originally discovered with the teeth has since been regarded as belonging to a prosauropod. Teeth assigned to Vulcanodon seem to be almost identical to the Sinosaurus teeth. It has even been suggested that the teeth belong to a non-dinosaur, possibly a large thecodont.

## Links

https://web.archive.org/web/20031008004053/http://www.jpinstitute.com/dinopedia/dinocards/dc\_sino.html

## References

1. ↑ 1.0 1.1 Template:Cite journal
2. ↑ M. T. Carrano. 2013. Taxonomic opinions on the Dinosauria.
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7. ↑ 7.0 7.1 7.2 Template:Cite journal
8. ↑ Glut, D. F. (1999). Dinosaurs, the Encyclopedia, Supplement 1: McFarland & Company, Inc., 442pp.
9. ↑ Template:Cite book
10. ↑ Lamanna, M. C., Holtz, T. R. Jr, and Dodson, P., 1998, A reassessment of the Chinese Theropod Dinosaur Dilophosaurus sinensis: Journal of Vertebrate Paleontology, Volume 18, Supplement to Number 3. Abstracts of papers. Fifty-eighth annual meeting, Society of Vertebrate Paleontology, Snowbird Ski and Summer Resort, Snowbird, Utah, September 30 – October 3, 1998, p. 57a.
11. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `currie13`
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