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This study investigates the developmental origins of skull shape differences between waterfowl (Anseriformes) and landfowl (Galliformes) by analyzing post-hatching cranial development across diverse species in both groups. The researchers found that waterfowl skulls develop through extended growth periods (hypermorphosis) and follow more varied developmental pathways compared to landfowl, whose skulls remain more constrained and retain ancestral characteristics. Analysis incorporating fossil evidence reveals that modern waterfowl have diverged more dramatically from the ancestral skull form, while landfowl have retained a more primitive morphology.
Why it matters
Understanding how developmental timing shifts (heterochrony) generate major morphological differences between closely related animal groups provides insights into the mechanisms driving evolutionary diversification. This research demonstrates how changes in post-hatching development can produce the dramatic differences in skull shape that distinguish two of the most economically and ecologically important bird groups.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Anseriformes (waterfowl) and Galliformes (landfowl) are among the world most recognisable groups of birds, together comprising the clade Galloanserae. Despite their close evolutionary relationship, the skulls of adult anseriforms and galliforms exhibit strikingly distinct morphologies, the developmental basis and evolutionary history of which is poorly understood. To illuminate the developmental and evolutionary underpinnings of cranial disparity between and within these major extant bird clades, we quantitatively investigated ontogenetic changes in cranial morphology across galloanseran phylogenetic diversity, focusing on the previously unexplored post-hatching interval during which adult morphology takes shape. Our results reveal the combined effects of multiple heterochronic shifts early in galloanseran evolutionary history including anseriform hypermorphosis, along with influential nonheterochronic changes leading to substantially more disparate ontogenetic trajectories, and greater cranial variability, in anseriforms than galliforms. Key galloanseran fossils help clarify the polarity of evolutionary shifts in cranial development through galloanseran phylogenetic history and demonstrate that extant galliform cranial morphology is more constrained and retains a more plesiomorphic morphology than that of anseriforms. Our work helps illuminate the developmental basis of the iconic differences in cranial form between waterfowl and landfowl and illustrates the importance of broad phylogenetic and ontogenetic sampling for clarifying patterns of post-hatching developmental divergence among major vertebrate clades.