Open Paleo

Sinotyrannus

Ji et al., 2009 SIGH-no-tie-RAN-us

From Latin 'Sinae' (a classical name for the Chinese) and Greek 'tyrannos' (tyrant); meaning 'Chinese tyrant'.

121.4–113.2 million years ago Aptian, Early Cretaceous
Early Cretaceous stages

Sinotyrannus is an extinct genus of large proceratosaurid tyrannosauroid theropod from the Aptian (Early Cretaceous) lower Jiufotang Formation of Kazuo County, western Liaoning Province, China — part of the Jehol Biota. The single species, Sinotyrannus kazuoensis, is known from a disarticulated skeleton (KZV-001) including the anterior skull and mandibles, three articulated dorsal vertebrae, ribs, partial ilia, and manual phalanges. Originally placed within Tyrannosauroidea (and tentatively Tyrannosauridae) by Ji and colleagues (2009), subsequent phylogenetic analyses (Loewen and colleagues 2013, and others) recovered Sinotyrannus as a basal proceratosaurid. With an estimated body length of ~9-10 m, it is one of the largest known Early Cretaceous tyrannosauroids.

Under dispute

Cau and Paterna (2025) proposed Sinotyrannus as the adult morphotype of the coeval compsognathid Huaxiagnathus, which would make Sinotyrannus a junior synonym of the older name, but that hypothesis is single-paper-recent and not yet a community consensus; the genus is treated as valid.

Diagnosis

  1. Proportionally large external naris, long-oval in shape with a long axis of 212 mm.
  2. Anterior portion of the dorsal margin of the maxilla slightly concave.
  3. Maxillary fenestra reaches past the rostral margin of the antorbital fossa but stays separated from its ventral margin.
  4. Preacetabular blade of the ilium short and lacking a ventrally expanded anterior hook.

Species

Sinotyrannus kazuoensis Ji et al., 2009

Type species

From 'Kazuo', referring to Kazuo County in western Liaoning Province, China, where the type specimen was found.

Holotype
KZV-001 , Bureau of Land and Resources of Kazuo County
Material
Disarticulated skeleton: anterior portions of skull and mandibles, three articulated dorsal vertebrae, several dorsal ribs, incomplete ilia, partial manual phalanges, and fragmentary bones.
Horizon
lower Jiufotang Formation, Aptian, Early Cretaceous , 121.4–113.2 million years ago
Locality
Dachengzi town, Liaoning, China

References

  1. Ji, Q.; Ji, S. A.; Zhang, L. J. (2009). First large tyrannosauroid theropod from the Early Cretaceous Jehol Biota in northeastern China. Geological Bulletin of China 28(10): 1369-1374. Geological Publishing House.

    Erects Sinotyrannus kazuoensis as a large early-diverging tyrannosauroid; later analyses moved it to Proceratosauridae.

    ji2009a
  2. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the mass estimate.

    paul2024a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026c
  4. Cau, A.; Paterna, A. (2025). Beyond the Stromer's Riddle: the impact of lumping and splitting hypotheses on the systematics of the giant predatory dinosaurs from northern Africa. Italian Journal of Geosciences 144(2): 162-185. doi:10.3301/IJG.2025.10

    Proposed Sinotyrannus as the adult morphotype of the compsognathid Huaxiagnathus.

    cau2025a
  5. Loewen, M. A.; Irmis, R. B.; Sertich, J. J. W.; Currie, P. J.; Sampson, S. D. (2013). Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans. PLoS ONE 8(11): e79420. Public Library of Science (PLoS). doi:10.1371/journal.pone.0079420

    Recovered Sinotyrannus as a basal proceratosaurid.

    loewen2013a