Xenovenator

Rivera-Sylva et al., 2026 ZEE-no-VEN-uh-tuh

From Greek xenos ('strange') and Latin venator ('hunter'), meaning 'strange hunter'

83.6–72.2 million years ago Campanian, Late Cretaceous

Late Cretaceous stages

Xenovenator is an extinct genus of troodontid theropod dinosaurs known from the Late Cretaceous (Campanian age) of North America. The type species of the genus, Xenovenator espinosai, is known from fragmentary skull bones found in the Cerro del Pueblo Formation of Mexico. It is characterized by an unusually expanded and rugose skull roof, somewhat comparable to that seen in pachycephalosaurs. This may imply Xenovenator individuals engaged in combat with other members of their species, a behavior for which adaptations had not been previously observed in non-avian paravians.

Under dispute

Xenovenator espinosai, a thick-skulled Mexican troodontid, was recovered within Troodontinae by its describers (Rivera-Sylva and colleagues, 2026), who placed it in a new tribe Troodontini (with Albertavenator and the North American Troodon complex). The tribe is not adopted as a node (single analysis); the genus is placed in Troodontinae.

Diagnosis

Frontals extensively fused with strongly interdigitating sutures
Strong doming of frontals projecting above orbital margins
Frontals and parietals massively thickened (up to 12 mm posteriorly) with variable thickness
Dorsal surface of frontals and parietals rugose and striated with transverse ridge texture
Nasal processes broad and transversely arched between lacrimals forming broad midline ridge
Orbital fossae widely separated ventrally with orbital margins expanded laterally
Triangular parietal table just behind frontoparietal suture, not seen in other troodontids
Laterosphenoids and orbitosphenoids strongly expanded anteriorly to enclose braincase ventrally
Supratemporal fossae extend strongly anterolaterally with frontoparietal suture projecting posteriorly
L-shaped frontal-lacrimal contact with complex posterior and medial facets

Species

Xenovenator espinosai Rivera-Sylva et al., 2026

Type species

Named for Luis Espinosa, a Mexican paleontologist and researcher.

Holotype: CPC 2973 , Colección Paleontológica de Coahuila, Museo del Desierto (MUDE)
Material: Braincase including frontals, parietals, orbitosphenoids, laterosphenoids, exoccipitals, prootics, and parts of parabasisphenoid and basioccipital.
Horizon: Cerro del Pueblo Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality: La Parrita, Coahuila, Mexico

References

Rivera-Sylva, H. E.; Aguillón-Martínez, M. C.; Flores-Ventura, J.; Sánchez-Uribe, I. E.; Guzmán-Gutiérrez, J. R.; Longrich, N. R. (2026). A Thick-Skulled Troodontid Theropod from the Late Cretaceous of Mexico. Diversity 18(1). MDPI AG. doi:10.3390/d18010038 rivera-sylva2026a