Yuanmouraptor

{{Speciesbox

| fossil_range = Middle Jurassic, {{fossilrange|Aalenian|Bajocian|Aalenian–Bajocian}}

| image = Yuanmouraptor (cranium, LFGT-ZLJ0115).png

| image_caption = Holotype skull and mandible

| image2 = Yuanmouraptor (holotype skull reconstruction).png

| image2_caption = Reconstructed skull

| display_parents = 2

| genus = Yuanmouraptor

| parent_authority = Zou et al., 2025

| species = jinshajiangensis

| authority = Zou et al., 2025

}}

Yuanmouraptor (meaning "Yuanmou County robber") is an extinct genus of metriacanthosaurid theropod dinosaurs from the Middle Jurassic Zhanghe Formation of China. The genus contains a single species, Y. jinshajiangensis, known from a skull and several vertebrae.

Discovery and naming

File:Yuanmouraptor (type locality).png

The Yuanmouraptor holotype specimen, LFGT-ZLJ0115, was discovered in March 2006 in outcrops of the Zhanghe Formation on a farm near Xiabanjing Village of Yuanmou County in Chuxiong Yi Autonomous Prefecture, Yunnan Province, China. The specimen consists of a nearly complete skull and mandible, ten articulated {{dinogloss|cervicals|cervical vertebrae}}, and the first {{dinogloss|dorsals|dorsal vertebra}}.{{Cite journal |last1=Zou |first1=Yi |last2=Chen |first2=Li |last3=Wang |first3=Tao |last4=Wang |first4=Guo-Fu |last5=Zhang |first5=Wei-Gang |last6=Zhang |first6=Xiao-Qin |last7=Wang |first7=Zhen-Ji |last8=Wu |first8=Xiao-Chun |last9=You |first9=Hai-Lu |date=2025-04-02 |title=A new metriacanthosaurid theropod dinosaur from the Middle Jurassic of Yunnan Province, China |journal=PeerJ |language=en |volume=13 |pages=e19218 |doi=10.7717/peerj.19218 |issn=2167-8359 |doi-access=free|pmc=11971988 }}

The name "Yuanmouraptor" was first mentioned in a 2014 newsletter from the Hong Kong Science Museum.{{Cite web |last=Mortimer |first=Mickey |title=Carnosauria |url=https://theropoddatabase.github.io/Carnosauria.htm#Yuanmouraptor |archive-url=https://web.archive.org/web/20250123185028/https://theropoddatabase.github.io/Carnosauria.htm#Yuanmouraptor |archive-date=2025-01-23 |access-date=2025-04-03 |website=Theropod Database}} As of its 2025 description, the holotype was on display in the Lufeng World Dinosaur Valley Museum.

In 2025, Zou et al. described Yuanmouraptor jinshajiangensis as a new genus and species of metriacanthosaurid dinosaurs based on these fossil remains. The generic name, Yuanmouraptor, combines a reference to the discovery of the holotype in Yuanmou County with the Latin word raptor, meaning "robber". The specific name, jinshajiangensis, references the Jinsha River, as the type locality is on the river's north bank.

Description

File:Yuanmouraptor jinshajiangensis.png]]

File:Yuanmouraptor (postaxial vertebrae, LFGT-ZLJ0115).png

Zou et al. described Yuanmouraptor as a "medium-sized" metriacanthosaurid. In all of the holotype vertebrae, the {{dinogloss|neural arch}} is fused to the respective {{dinogloss|centrum}}, with the {{dinogloss|neurocentral suture}} only somewhat visible on the eighth and ninth cervical vertebrae. As these sutures are open in juvenile animals, the prominent fusion is indicative of a subadult or nearly mature ontogenetic stage for this individual. As preserved, the holotype skull is {{convert|53.9|cm|in}} long. When reconstructed, its full length is around {{convert|60|cm|in}}. In comparison, the holotype skull of Yangchuanosaurus shangyouensis is {{convert|78|cm|in}} long, belonging to an animal around {{convert|8|m|ft}} long.{{cite journal |last1=Dong |first1=Zhiming |last2=Zhang |first2=Yihong |last3=Li |first3=Xuanmin |last4=Zhou |first4=Shiwu |title=A new carnosaur from Yongchuan County, Sichuan Province |journal=Ke Xue Tong Bao |volume=23 |issue=5 |year=1978 |pages=302–04 |url=https://naturalhistory.si.edu/sites/default/files/media/translated_publications/Dong%26amp%3B%25201975.pdf}}

Several autapomorphies (unique derived traits) of Yuanmouraptor are observable in the {{dinogloss|postorbital}} (skull bone forming the back of the orbit) and {{dinogloss|cervicals|cervical vertebrae}}. These include an anterior (toward the front) process of the postorbital that is sheet-shaped with a consistent depth, a ventral (toward the bottom) ramus of the postorbital with a laterally twisted trough going over the outer surface, strongly posteriorly elongated epipophyses (projections above the back articular process) on the anterior cervical vertebrae, and a strongly ventromedially (down and toward the midline) excavated pneumatic foramen (air sac) on the third cervical vertebra.

Classification

Prior to its scientific naming and description, Hendrickx et al. (2019) mentioned the Yuanmouraptor holotype as belonging to an indeterminate member of the allosauroid family Metriacanthosauridae.{{Cite journal |last1=Hendrickx |first1=Christophe |last2=Mateus |first2=Octávio |last3=Araújo |first3=Ricardo |last4=Choiniere |first4=Jonah |date=2019 |title=The distribution of dental features in non-avian theropod dinosaurs: Taxonomic potential, degree of homoplasy, and major evolutionary trends |url=https://palaeo-electronica.org/content/2019/2806-dental-features-in-theropods |journal=Palaeontologia Electronica |doi=10.26879/820 |doi-access=free|hdl=10362/98436 |hdl-access=free }} In their phylogenetic analyses when describing Yuanmouraptor, Zou et al. (2025) recovered this taxon—as well as the slightly younger Xuanhanosaurus—as the most basal members of the Metriacanthosauridae. These results are displayed in the cladogram below:

{{clade|style=font-size:90%;line-height:90%

|{{clade

|1=Monolophosaurus

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|2=Chuandongocoelurus

|3={{clade

|label1=Megalosauroidea

|1={{clade