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Macroevolutionary integration underlies limb modularity in the origin of avian flight
Sergio M Nebreda1,2, Manuel Hernández Fernández3,4, Jesús Marugán-Lobón1,5
1Centre for the Integration in Palaeobiology, Universidad Autónoma de Madrid, Madrid, 28049, Spain.
Biology Letters
|May 6, 2025
Summary
Limb evolution in maniraptoran dinosaurs and birds was shaped by developmental constraints, not just flight specialization. This study reveals integrated limb development influenced their evolutionary path.
Area of Science:
- Paleontology
- Developmental Biology
- Evolutionary Biology
Background:
- The evolution of avian flight is debated, with hypotheses focusing on specialized locomotor modules versus shared developmental constraints on limb evolution.
- Understanding limb covariation in non-avian maniraptoran theropods and modern birds is key to resolving this debate.
Purpose of the Study:
- To statistically analyze limb morphological covariation in a broad phylogenetic context.
- To assess whether limb evolution was driven by functional specialization for flight or by developmental integration.
Main Methods:
- Utilized an alternative morphometric approach.
- Compared and statistically analyzed limb morphological covariation across non-avian maniraptoran theropods and modern birds.
Main Results:
- The maniraptoran lineage exhibits strong covariation between limb proportions, indicating significant morphological integration.
- Distinct, weaker covariation patterns were observed in different evolutionary grades within Maniraptora (volant and non-volant).
- These findings suggest the emergence of independent evolutionary trends within an integrated developmental framework.
Conclusions:
- Limb evolution in maniraptoran dinosaurs was influenced by serial homology and shared developmental programs.
- Developmental constraints played a significant role, challenging the idea that limb evolution was solely driven by modular specialization for flight.
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