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Peer-reviewedCC BYScience Advances

Embryos resolve the enigmatic origin of the theropod wishbone

  • Sebastian Jiménez-Villalón1,2
  • Felipe Guajardo-Pezo1,2
  • Mackarenna Narváez3
  • Daniel Smith-Paredes4
  • Tiana Kohlsdorf5
  • Joao F. Botelho2,6
  • Alexander O. Vargas1,6
6 affiliations
  1. 1Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.
  2. 2Laboratorio de Evolución y Desarrollo, Escuela de Medicina Veterinaria, Pontificia Universidad Católica de Chile, Santiago, Chile.
  3. 3Laboratorio de Histopatología. Escuela de Medicina Veterinaria, Pontificia Universidad Católica de Chile, Santiago, Chile.
  4. 4Centre for Interdisciplinary Research in Biology, Collège de France, CNRS, Paris, France.
  5. 5Department of Biology, FFCLRP, University of São Paulo. Avenida Bandeirantes, 3900, Bairro Monte Alegre. Ribeirão Preto, São Paulo, Brazil.
  6. 6Núcleo Milenio Transiciones Evolutivas Tempranas de Mamíferos, Santiago, Chile.
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Abstract

The origin of the avian wishbone (furcula)—present since theropod dinosaurs—remains unsolved. Its homology is still debated, with competing hypotheses proposing derivation from the clavicles, the interclavicle, or both. To obtain comparative developmental evidence, we studied ossification and pre-ossification mesenchymal condensations in a broad sample of birds and non-avian reptiles. Relative positions of paired condensations and their ossification centers support homology between the lateral arms of the furcula and reptilian clavicles. However, in the palaeognathous bird Nothoprocta perdicaria , we observed a separate interclavicle-like medial condensation. It quickly fuses with the clavicular condensations but then develops its own ossification center. The phylogenetic distribution of this developmental pattern across reptiles and birds supports a composite origin of the furcula from clavicles and the interclavicle. Early fusion of condensations leads to seamless integration, which may explain why fossil evidence of this composite origin has remained elusive.

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Cite

BibTeXRIS
BibTeX
@article{jimenezvillalon2026embryos,
  title = {{Embryos resolve the enigmatic origin of the theropod wishbone}},
  author = {Sebastian Jiménez-Villalón and Felipe Guajardo-Pezo and Mackarenna Narváez and Daniel Smith-Paredes and Tiana Kohlsdorf and Joao F. Botelho and Alexander O. Vargas},
  journal = {Science Advances},
  year = {2026},
  month = oct,
  doi = {10.1126/sciadv.aeh7555},
  url = {https://www.science.org/doi/10.1126/sciadv.aeh7555},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Embryos resolve the enigmatic origin of the theropod wishbone
AU  - Sebastian Jiménez-Villalón
AU  - Felipe Guajardo-Pezo
AU  - Mackarenna Narváez
AU  - Daniel Smith-Paredes
AU  - Tiana Kohlsdorf
AU  - Joao F. Botelho
AU  - Alexander O. Vargas
PY  - 2026
DA  - 2026/10/09
JO  - Science Advances
DO  - 10.1126/sciadv.aeh7555
UR  - https://www.science.org/doi/10.1126/sciadv.aeh7555
AB  - The origin of the avian wishbone (furcula)—present since theropod dinosaurs—remains unsolved. Its homology is still debated, with competing hypotheses proposing derivation from the clavicles, the interclavicle, or both. To obtain comparative developmental evidence, we studied ossification and pre-ossification mesenchymal condensations in a broad sample of birds and non-avian reptiles. Relative positions of paired condensations and their ossification centers support homology between the lateral arms of the furcula and reptilian clavicles. However, in the palaeognathous bird Nothoprocta perdicaria , we observed a separate interclavicle-like medial condensation. It quickly fuses with the clavicular condensations but then develops its own ossification center. The phylogenetic distribution of this developmental pattern across reptiles and birds supports a composite origin of the furcula from clavicles and the interclavicle. Early fusion of condensations leads to seamless integration, which may explain why fossil evidence of this composite origin has remained elusive.
SN  - 2375-2548
ER  -