The theropod furcula
Open accessAbstract
The furcula is a structure formed by the midline fusion of the clavicles. This is the element which is unique to theropods and is important for understanding the link between birds and other theropods. New specimens from basal theropods suggest that the furcula appeared very early in theropod history. We review furcula development, function, and morphology, as well as the anatomical terminology applied to it. Furcular morphology is highly variable in crown‐group avians but is rather conserved among nonavian theropods. Here we review, or describe for the first time, the furculae in many nonavian theropods. Furculae occur in nearly all major clades of theropods, as shown by new theropod specimens from the Early Cretaceous of China and a close inspection of previously collected specimens. Informative phylogenetic characters pertaining to the furcula occur throughout Theropoda, though care should betake to consider taphonomic effects when describing furcular morphology. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc.
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Archaeopteryx was warm-blooded.
“The phylogenetic position of Archaeopteryx indicates that it was warm-blooded but it can be inferred to have had a lower metabolic rate than crown birds based on the slower deposition of bone tissue in Archaeopteryx and other early-diverging Cretaceous birds compared to a subset of ornithuromorphs that includes Neornithes with uninterrupted growth [37, 106].”
From The ecology of Archaeopteryx (2026) · cites this paper as [37]
The Avialae section describes Archaeopteryx’s furcula but does not address whether it was warm-blooded. Searches for endothermy, metabolic rate, and bone-tissue deposition found no passage in our copy supporting that inference. (LLM, conf=0.76)
Experimental — accuracy not yet measuredArchaeopteryx had a lower metabolic rate than crown birds.
“The phylogenetic position of Archaeopteryx indicates that it was warm-blooded but it can be inferred to have had a lower metabolic rate than crown birds based on the slower deposition of bone tissue in Archaeopteryx and other early-diverging Cretaceous birds compared to a subset of ornithuromorphs that includes Neornithes with uninterrupted growth [37, 106].”
From The ecology of Archaeopteryx (2026) · cites this paper as [37]
The Avialae section describes the shape of Archaeopteryx’s furcula, not its metabolism. Searches for metabolic rate, bone-tissue deposition, growth, and warm-bloodedness found no passage comparing Archaeopteryx with crown birds. (LLM, conf=0.76)
Experimental — accuracy not yet measuredThe Archaeopteryx preserved in the marine Solnhofen Limestones likely represent immature and inexperienced individuals caught during storm events and blown out to sea by strong winds acting on their large feathered airfoils.
“The fact all specimens were actively growing at the time of death [37] suggests the Archaeopteryx preserved in the marine Solnhofen Limestones likely represent immature and inexperienced individuals caught during storm events and blown out to sea by strong winds acting on their large feathered airfoils [1].”
From The ecology of Archaeopteryx (2026) · cites this paper as [37]
The Avialae section describes the furculae of two Archaeopteryx specimens, not their maturity or how they reached the Solnhofen deposits. Searches for storms, winds, transport out to sea, immaturity, and feathered airfoils found no passage addressing that explanation (page unavailable in our copy). (LLM, conf=0.76)
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References 118 · Cited by 78
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- Authors
- Nesbitt, S. J., Turner, A. H., Spaulding, M., Conrad, J. L., & Norell, M. A.
- Affiliations
- American Museum of Natural History (US)
- Corresponding author
- Nesbitt, Sterling J.
- Venue
- Journal of Morphology
- Publisher
- Wiley
- Published
- 2009-06-08
- Volume
- 270
- Issue
- 7
- Pages
- 856-879
- ISSN
- 0362-2525 (ISSN-L)
- 1097-4687
- OpenAlex
- W2063794697
- Cited by
- 78
- References
- 118
- Citations by year
- 2026: 3 · 2025: 6 · 2024: 4 · 2023: 1 · 2022: 2 · 2021: 1 · 2020: 5 · 2019: 5 · 2018: 7 · 2017: 11 · 2016: 6 · 2015: 5 · 2014: 6 · 2013: 1 · 2012: 7
- FWCI
- 0.52
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of Morphology (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Science Foundation (0608003, 0228693)
- Minnesota Pollution Control Agency
- American Museum of Natural History
- Field Museum
- Topics
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Evolutionary Biology
- Health Sciences › Medicine › Urology › Comparative Animal Anatomy Studies
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
- Keywords
- avian origin, phylogenetic characters, anatomical terminology
- MeSH terms
- Animals, Birds, Clavicle, Biological Evolution, Fossils, Paleontology, Phylogeny, Dinosaurs
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