Open Paleo

Siamraptor

Chokchaloemwong et al., 2019 SY-am-RAP-tor

From 'Siam', the former name of Thailand, combined with Latin 'raptor' (thief, plunderer), meaning 'Siamese plunderer' or 'thief from Siam'.

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

Siamraptor is an extinct genus of carcharodontosaurian dinosaur, containing the single species S. suwati, known from the Khok Kruat Formation of Thailand. It is the first definitive named carcharodontosaurian species known from Southeast Asia.

Under dispute

Siamraptor suwati is recovered as a basal member of Carcharodontosauria, often as sister to Concavenator (Chokchaloemwong and colleagues, 2019; Kellermann and colleagues, 2025); in analyses that do not recover a monophyletic Carcharodontosauria it falls instead within Metriacanthosauridae. It is placed at Carcharodontosauria incertae sedis.

Diagnosis

  1. Jugal with straight ventral margin and dorsoventrally deep anterior process below orbit
  2. Surangular with deep oval concavity at posterior end of lateral shelf and four posterior surangular foramina
  3. Long and narrow groove along suture between surangular and prearticular
  4. Articular with foramen at notch of suture with prearticular
  5. Anterior cervical vertebra with additional pneumatic foramen excavating parapophysis
  6. Cervical and posterior dorsal vertebra penetrated by pair of small foramina bilaterally at base of neural spine

Species

Siamraptor suwati Chokchaloemwong et al., 2019

Type species

Named for Suwat Liptapanlop, who supported the Northeastern Research Institute of Petrified Wood and Mineral Resources.

Holotype
NRRU-F01020008 , Nakhon Ratchasima Rajabhat University
Material
Articulated posterior half of right mandible comprising surangular, prearticular, and articular
Horizon
Khok Kruat Formation, Aptian, Early Cretaceous , 121.4–113.2 million years ago
Locality
Ban Saphan Hin, Nakhon Ratchasima, Thailand

References

  1. Chokchaloemwong, D.; Hattori, S.; Cuesta, E.; Jintasakul, P.; Shibata, M.; Azuma, Y. (2019). A new carcharodontosaurian theropod (Dinosauria: Saurischia) from the Lower Cretaceous of Thailand. PLOS ONE 14(10): e0222489. Public Library of Science (PLoS). doi:10.1371/journal.pone.0222489 chokchaloemwong2019a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the body length, mass, and hip height estimates.

    jones2026c
  3. Kellermann, M.; Cuesta, E.; Rauhut, O. W. M. (2025). Re-evaluation of the Bahariya Formation carcharodontosaurid (Dinosauria: Theropoda) and its implications for allosauroid phylogeny. PLOS ONE 20(1): e0311096. Public Library of Science (PLoS). doi:10.1371/journal.pone.0311096

    Reanalysis places Siamraptor within Metriacanthosauridae absent monophyletic Carcharodontosauria.

    kellermann2025a