Beak Shapes and Evolution in Theropods, Common Developmental Origins (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

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Free pdf:

Kathleen L.S. Garland, Eleanor M. Hay, Daniel J. Field, Alistair R. Evans (2025)
Common Developmental Origins of Beak Shapes and Evolution in Theropods
iScience 112246
doi: https://doi.org/10.1016/j.isci.2025.112246
https://www.sciencedirect.com/science/article/pii/S2589004225005073

Highlights

The power cascade is a conserved growth model for theropod beak and snout shape
The power cascade generates the primordial shape of the vertebrate rostrum
Beaks of most species follow the power cascade to fill many adaptive functions
The power cascade has shaped the face of theropods for 200 million years

Summary

Vertebrate beaks show a remarkable diversity of forms, epitomised by birds and non-avian theropods. Few studies have investigated how underlying developmental processes influence beak shape. The power cascade is a model of growth describing the log-log linear relationship of the beak radius with distance from the tip. We measured beak and toothed snout shapes in 127 species across 120 families of extant birds and extinct non-avian theropods and found that 95% followed the power cascade model. Ancestral state estimation suggests that the power cascade constitutes a fundamental growth pattern of the theropod rostrum, and perhaps all vertebrate rostra. The morphospace defined by the power cascade shows how bird beak shape explores the geometries associated with ecological specialisations while adhering to the growth model. We show that the power cascade influences the macroevolutionary exploration of rostrum morphospace, enabling extant birds to inhabit all components of Earth’s biosphere.

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