Xuanhanosaurus

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Xuanhanosaurus
Temporal range:
Ma
↓
[1]
An artist's restoration of Xuanhanosaurus qilixiaensis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Genus: †Xuanhanosaurus
Dong, 1984
Species:
†X. qilixiaensis
Binomial name
†Xuanhanosaurus qilixiaensis
Dong, 1984

Xuanhanosaurus (meaning "

metacarpal
.

Discovery

Xuanhanosaurus reconstructed in a quadrupedal position[3] which is now considered outdated.[4]

The

Lower Shaximiao Formation. It consists of a partial skeleton without a skull, namely a scapula missing the posterior end, coracoid, a possible sternum humerus, radius, ulna, manus, as well a few fragmentary dorsal vertebrae.[3]

Description

An X. qilixiaensis specimen compared to an average human male

Xuanhanosaurus, originally thought to be around 6 m long, was approximately 4.8 meters (16 ft) in length, with a weight of 265 

pronation of the lower arm being impossible. The strong arms could instead have been useful in catching prey.[7] The retention of the 4th metarcarpal is the most notorious feature of this taxon, yet the presence of a convex proximal surface on the distal carpal 2 has been used to arge it represents a second stage in the evolution of the "semilunate" carpal.[8] Some recent work have notified that beyond the 4th metarcarpal, Xuanhanosaurus also retains ceratosaurian-like short phalanges II-1, similar in length to the ones recovered on Saltriovenator.[9] The scapula was found to be bulkier than in Allosaurus. The distal humerus is enlarged laterally, forming a one-inch step.[3] The vertebrae are posteriorly concave and anteriorly protruding, with cervical centra having flat anterior articular surfaces, also seen in Condorraptor, Piatnitzkysaurus and "Szechuanosaurus" zigongensis, yet lacking posterior pneumatic foramen or fossa, which is seen on the first 2 genera.[10]

Phylogeny

Originally, Xuanhanosaurus was assigned by Dong to the Megalosauridae, when this group was meant to include a larger amount of taxa, and was argued to be in the middle stage of the evolution of the Tetanurae due to its vestigial fourth metacarpals.[3] Latter it was found by Roger Benson in 2009 to belong to a primitive lineage of the Megalosauroidea.[11] A more recent study by Benson and colleagues in 2010 found that it was more likely to be the most primitive known member of the Metriacanthosauridae family.[4] In 2018, based on several conditions such as the length and retention of the vestigial 4th metacarpal, it was argued that this taxon and "Szechuanosaurus" zigongensis belong to early-diverging branches of the ceratosaurian-tetanuran node.[9] In 2019, Rauhut and Pol recovered Xuanhanosaurus outside of Metriacanthosauridae, as the basalmost member of Allosauroidea.[7]

Carnosauria


References

  1. S2CID 247000432
    .
  2. ^ Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.
  3. ^ a b c d e f g Dong, Z. (1984). "A new theropod dinosaur from the Middle Jurassic of Sichuan Basin". Vertebrata PalAsiatica. 22 (3): 213–218. Retrieved 10 July 2023.
  4. ^
    S2CID 22646156. Supporting Information
  5. ISBN 9780691137209
    .
  6. ISBN 978-0-691-18031-1
    .
  7. ^
    PMID 31827108
    .
  8. PMID 25116378
    .
  9. ^
    PMID 30588396
    .
  10. PMID 31924836
    .
  11. doi:10.1111/j.1096-3642.2009.00569.x
    .
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