Open Paleo

Sinornithoides

Russell & Dong, 1993 sie-NOR-ni-THOI-deez

From Latin Sinae, "Chinese", Greek ornis, "bird", and Greek -oides, "form/resembling" — means "Chinese bird form"

121.4–100.5 million years ago Aptian–Albian, Early Cretaceous
Early Cretaceous stages

Sinornithoides is a genus of troodontid theropod dinosaurs that lived during the Early Cretaceous (Aptian or Albian stage, around 113 million years ago) of Inner Mongolia, China. It contains only a single species, S. youngi. Sinornithoides measured approximately 1 meter (3.3 ft) long, and probably ate invertebrates and other small prey.

Under dispute

Sinornithoides is recovered near the base of the troodontine radiation but outside a stably defined Troodontinae — as an outgroup to the derived Saurornithoides-Zanabazar-Troodon clade (Norell and colleagues, 2009), just stemward of Troodontinae when that subfamily was erected (van der Reest and Currie, 2017), or in a basal polytomy (Yin and colleagues, 2018). It is placed at Troodontidae incertae sedis.

Diagnosis

  1. Skull shorter than Saurornithoides by factor of 0.7, relative to proximal caudal and pedal length
  2. Nasomaxillary suture angled 20° to alveolar margin (vs steeper in relatives)
  3. Temporal region narrower than orbit
  4. Orbital rim frontal directed laterally at 20° to midsagittal plane
  5. Tibia exceeds femur by factor of 1.4
  6. Third metatarsal lacks well-developed posteroventral tongue-like extension
  7. Lacks Borogovia pedal specializations (short fourth digit, unrecurved unguals)

Species

Sinornithoides youngi Russell & Dong, 1993

Type species

Named for Yang Zhongjian (also romanized as C.C. Young), the pioneering Chinese paleontologist known as the 'Father of Chinese Vertebrate Paleontology'.

Holotype
IVPP V9612 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Articulated skeleton, approximately 1.1 m long, nearly complete except for eroded dorsal elements and right skull half.
Horizon
Ejinhoro Formation, Aptian–Albian, Early Cretaceous , 121.4–100.5 million years ago
Locality
0.7 km west of Huamuxiao Village, Inner Mongolia, China

References

  1. Russell, D. A.; Dong, Z. M. (1993). A nearly complete skeleton of a new troodontid dinosaur from the Early Cretaceous of the Ordos Basin, Inner Mongolia, People's Republic of China. Canadian Journal of Earth Sciences 30(10): 2163-2173. Canadian Science Publishing. doi:10.1139/e93-187 russell1993a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c
  3. Norell, M. A.; Makovicky, P. J.; Bever, G. S.; Balanoff, A. M.; Clark, J. M.; Barsbold, R.; Rowe, T. (2009). A Review of the Mongolian Cretaceous Dinosaur Saurornithoides (Troodontidae: Theropoda). American Museum Novitates 3654: 1-63. American Museum of Natural History (BioOne sponsored). doi:10.1206/648.1

    Reviewed troodontids, placing Sinornithoides basal to the derived Saurornithoides-Zanabazar-Troodon clade.

    norell2009a
  4. Yin, Y.; Pei, R.; Zhou, C. (2018). Cranial morphology of Sinovenator changii (Theropoda: Troodontidae) on the new material from the Yixian Formation of western Liaoning, China. PeerJ 6: e4977. doi:10.7717/peerj.4977

    Recovers Sinornithoides in a polytomy with Troodon, Zanabazar, and Byronosaurus

    yin2018a
  5. van der Reest, A. J.; Currie, P. J. (2017). Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America. Canadian Journal of Earth Sciences 54(9): 919-935. doi:10.1139/cjes-2017-0031

    Placed Sinornithoides stemward of Troodontinae when that subfamily was erected

    vanderreest2017a