Abelisaurid orbit shape evolution

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

Enzo Emanuel Seculi Pereyra (2025)
Orbit Shape Evolution in Abelisauridae: Macroevolutionary Trends and Functional Implications
Cretaceous Research 106272
doi: https://doi.org/10.1016/j.cretres.2025.106272
https://www.sciencedirect.com/science/article/abs/pii/S0195667125001958

Highlights

The abelisaurid orbit shape was evolutionary integrated with significantly higher rate of evolution in Cretaceous abelisaurids, suggesting a stronger ecological pressure shaping orbital morphology.

The orbit shape in Cretaceous abelisaurids may have primarily driven by ecological pressures with secondary traits related with socio-sexual displays

The phenotype of keyhold-shaped and eight-shape orbits became canalized in Late Cretaceous abelisaurids.

Abelisaurid orbit shape evolution supports that the specialized feeding innovation in Abelisauridae emerged during the Lower Cretaceous.

Abstract

Large carnivorous theropods evolved diverse orbital morphologies, including eight-shaped, keyhole-shaped, and elliptical orbits, which have been linked to feeding performance and biomechanical adaptations. In Abelisauridae, the most abundant and best-known clades of Gondwanan theropods, the orbit underwent significant morphological changes, with Cretaceous taxa exhibiting keyhole-shaped and eight-shaped orbits. However, a rigorous phylogenetic comparative approach and multivariate quantification of orbit shape are necessary to further investigate macroevolutionary trends in Abelisauridae orbital evolution. To address this, I applied 2D geometric morphometrics and phylogenetic comparative methods to analyze macroevolutionary trends of orbit shape in Abelisauridae. The results indicate that the abelisaurid orbit shape evolved as an integrated morphological module undergoing accelerated evolution in Cretaceous taxa, likely driven by intensified ecological and functional pressures on orbital shape design. Additionally, phylogenetic signal was not detected, supporting the hypothesis that orbit evolution was primarily driven by selective pressures rather than phylogenetic constraints. Disparity through time analysis revealed a decline in morphological variation during the Late Cretaceous, coinciding with the canalization of specialized orbit morphologies. The results are consistent with previous studies on abelisaurid feeding strategies and suggest that specialized predation may have influenced orbit evolution since at least the Early Cretaceous. These findings provide new insights into the evolutionary history of Abelisauridae, emphasizing the role of ecological and functional factors in shaping their orbital diversity.

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