Xenovenator, new troodontid from Late Cretaceous of Mexico (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

Free pdf:

Xenovenator espinosai gen. et sp. nov.

Hector E. Rivera-Sylva, Martha C. Aguillón-Martinez, Jose Flores-Ventura, Ivan E. Sánchez-Uribe, Jose Ruben Guzman-Gutierrez and Nicholas R. Long (2026)
A Thick-Skulled Troodontid Theropod from the Late Cretaceous of Mexico
Diversity 18(1): 38
doi: https://doi.org/10.3390/d18010038
https://www.mdpi.com/1424-2818/18/1/38


Dinosaurs repeatedly evolved adaptations for sexual selection over their 150-million year history, including adaptations for display and intraspecific combat. Adaptations for intraspecific combat have not previously been described in non-avian maniraptorans. We report a troodontid from the Campanian Cerro del Pueblo Formation of Coahuila, Mexico, showing a thickened and domed skull roof. The cranium is domed and bones are extremely thick, a morphology convergent on that of Pachycephalosauridae. Referred specimens show less thickening or doming, suggesting ontogenetic changes or perhaps sexual dimorphism. The holotype shows fusion of the frontal midline suture and tightly interdigitating sutures between skull bones, and a rugose skull roof. The specializations seen here suggest adaptation for intraspecific combat, specifically head-butting as hypothesized for pachycephalosaurids and pachyrhinosaurin ceratopsids. Repeated evolution of elaborate weapons and display features in the Cretaceous suggests that sexual selection became increasingly important in dinosaur evolution during the Cretaceous.

[Tim Williams]

This new troodontid reminds me of _Yaverlandia_, the erstwhile pachycephalosaur now regarded (provisionally) as a maniraptoran.

(Note that the name of the last author is Longrich not Long.)

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[Jaime Headden]

The doming is similar, even, albeit not like the implied double dome in Yaverlandia. The authors support some form of agonistic behavior and cranial ornamentation convergent with helmeted ducks and pachycephalosaurs, referencing the thickened frontal bones, although the doming itself is not that radically different from Saurornithoides/"Troodon" frontals already described. Rather, they lean into the surface texture of the bone. CT and photos of the skull do not show any particularly pachy-like or "engraved" surface textures relating to such implied keratinous covering; rather than similar to the incised vascular grooves of some pachy domes, or the compared helmeted birds, it's really rough and suggests at least a more glabrous or at least cornified but thickened dermal tissue, but not keratinized sheathes.

The thickened domed frontals are still peculiar, presenting elaboration of the troodontid interfrontal fusion, resembling Avimimus portentosus, which itself is an hitherto unrecognized "domed" theropod, but without the peripheral fusion or obliteration of sutures present in more agonistic animals, suggesting if they were used agonistically, it was probably far less aggressive than "fly[ing] at each other at high speed and ram their casques together head-on." (This is referring to the nearly solid "casque" of Rhinoplax vigil, which is quite distinct from other hornbills, which are hollow with fragile and extraordinarily thin bone.)

Cheers,

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Jaime A. Headden

The Bite Stuff: http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth" - P. B. Medawar (1969)

[Ben Creisler]

A new video and correcting a missed copy-paste chop on Longrich in the  authors citation:

Xenovenator, a thick-headed troodontid from the Late Cretaceous of Coahuila, Mexico
Nick Longrich Evolution and Paleontology (video)
42 min.

https://www.youtube.com/watch?v=eMSJM_oBcrI&t=295s

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Hector E. Rivera-Sylva, Martha C. Aguillón-Martinez, Jose Flores-Ventura, Ivan E. Sánchez-Uribe, Jose Ruben Guzman-Gutierrez and Nicholas R. Longrich (2026)

A Thick-Skulled Troodontid Theropod from the Late Cretaceous of Mexico
Diversity 18(1): 38
doi: https://doi.org/10.3390/d18010038
https://www.mdpi.com/1424-2818/18/1/38

On Fri, Jan 9, 2026 at 9:37 AM Ben Creisler <bcre...@gmail.com> wrote:

Ben Creisler

bcre...@gmail.com

A new paper:

Free pdf:

Xenovenator espinosai gen. et sp. nov.

Hector E. Rivera-Sylva, Martha C. Aguillón-Martinez, Jose Flores-Ventura, Ivan E. Sánchez-Uribe, Jose Ruben Guzman-Gutierrez and Nicholas R. Longrich (2026)