Sinotyrannus

Sinotyrannus
Temporal range: Early Cretaceous, 120 Ma
↓
Diagram of known fossil remains in grey
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Clade:Dinosauria
Order:Saurischia
Suborder:Theropoda
Family:†Proceratosauridae
Genus:†Sinotyrannus
Ji et al., 2009
Species: †S. kazuoensis
Binomial name
Sinotyrannus kazuoensis
Ji et al., 2009

Sinotyrannus (meaning "Chinese tyrant") is a genus of large basal proceratosaurid[1] dinosaur, a relative of tyrannosaurids which flourished in North America and Asia during the Jurassic and early Cretaceous periods. Sinotyrannus is known from a single incomplete fossil specimen including a partial skull, from the Early Cretaceous Jiufotang Formation of Liaoning, China. Though it is not much younger than primitive tyrannosauroids such as Dilong, it is similar in size to later forms such as Tyrannosaurus. It was much larger than contemporary tyrannosauroids; reaching a total estimated length of 9–10 m (30–33 ft), it is the largest known theropod from the Jiufotang Formation. The type species is S. kazuoensis, described by Ji et al., in 2009.[2]

Description

Life restoration with size compared to a human

The holotype of Sinotyrannus is KZV-001, a disarticulated partial skeleton including the front portion of the skull, three dorsal vertebrae, the incomplete ilia, three articulated manual phalanges (including an ungual), and other fragmentary bones.[2]

The preserved cranial elements include the premaxillae, dentary, and anterior portions of the maxillae and nasals. The dorsal margin of the maxilla is unusually concave unlike the convex condition in tyrannosaurids. The nares are large and elliptical, supporting its relation to proceratosauridae. The dentary gradually curves upwards as it approaches its front edge. Many teeth are preserved attached to the maxillae, with a roughly equal number of denticles on each side, similarly to those of tyrannosaurids. Sinotyrannus could perceivably have had a tall nasal crest like other proceratosaurids, although not enough of its nasals are preserved to be certain.

The three preserved vertebrae have very tall neural spines. The proportions of the preserved manual phalanges support the idea that they belong to the second finger, and the ungual has a deep groove on each side. The ilia are mainly present as molds, with the mold of the external side of the left ilium being the most complete. The preacetabular blade is short and wide, with a massive pubic peduncle, while the postacetabular blade is longer and thinner, with a triangular ischial peduncle. These traits of the ilia differentiate it from more advanced tyrannosauroids such as the tyrannosaurids.

Sinotyrannus was among the largest basal tyrannosauroids known, repudiating the previously presumed trend that tyrannosauroids gradually increased in size throughout the Cretaceous period from small basal forms like Dilong to advanced apex predators such as Tyrannosaurus.

Classification

The original description of Sinotyrannus proposed that it could have been the earliest tyrannosaurid due to its large size,[2] but subsequent analyses place it as a proceratosaurid tyrannosauroid. It is considered to be part of a clade containing Juratyrant and Stokesosaurus, as they all reputedly share a narrow preacetabular notch.[3] A 2016 analysis instead placed Juratyrant and Stokesosaurus outside of proceratosauridae and proposed that Sinotyrannus is a sister taxon of Yutyrannus within proceratosauridae.[4]

Below is a cladogram by Loewen et al. in 2013.[3]

Estimated size of Sinotyrannus, compared to a human.

Tyrannosauroidea

Proceratosauridae

 

 

Proceratosaurus bradleyi

 
 

Kileskus aristotocus

 
 

Guanlong wucaii

 
 
 

 

Sinotyrannus kazuoensis

 
 

 

Juratyrant langhami

 
 

Stokesosaurus clevelandi

 
 
 
 
 

 

Dilong paradoxus

 
 

 

Eotyrannus lengi

 
 

 

Bagaraatan ostromi

 
 

 

Raptorex kriegsteini

 
 

 

Dryptosaurus aquilunguis

 
 

 

 

Alectrosaurus olseni

 
 

Xiongguanlong baimoensis

 
 
 

 

Appalachiosaurus montgomeriensis

 
 

 

 

Alioramus altai

 
 

Alioramus remotus

 
 
 

Tyrannosauridae

 
 
 
 
 
 
 
 
 
 

See also

References

  1. ↑ Brusatte, S. L.; Norell, M. A.; Carr, T. D.; Erickson, G. M.; Hutchinson, J. R.; Balanoff, A. M.; Bever, G. S.; Choiniere, J. N.; et al. (2010). "Tyrannosaur paleobiology: new research on ancient exemplar organisms". Science. 329 (5998): 1481–1485. doi:10.1126/science.1193304. PMID 20847260.
  2. 1 2 3 Ji, Q.; Ji, S.-A.; Zhang, L.-J. (2009). "First large tyrannosauroid theropod from the Early Cretaceous Jehol Biota in northeastern China" (PDF). Geological Bulletin of China. 28 (10): 1369–1374.
  3. 1 2 Loewen, M.A.; Irmis, R.B.; Sertich, J.J.W.; Currie, P. J.; Sampson, S. D. (2013). Evans, David C, ed. "Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans". PLoS ONE. 8 (11): e79420. doi:10.1371/journal.pone.0079420. PMC 3819173. PMID 24223179.
  4. ↑ Brusatte, Stephen L.; Carr, Thomas D. (2016-02-02). "The phylogeny and evolutionary history of tyrannosauroid dinosaurs". Scientific Reports. 6 (1). doi:10.1038/srep20252. ISSN 2045-2322.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.