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Updated: Dec 31, 2025
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Author Spotlight: Comparing Alveolar and Long Bone Remodeling to Explore OTM Model Potential
Published on: July 21, 2023
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Identifying medullary bone in extinct avemetatarsalians: challenges, implications and perspectives
Aurore Canoville1,2, Mary H Schweitzer1,2,3,4, Lindsay Zanno1,2
1Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA.
Summary
Medullary bone (MB), a tissue in female birds, shows more diversity than previously known. This study refines criteria for identifying MB in fossils, improving our understanding of extinct avemetatarsalians.
Area of Science:
- Paleontology
- Comparative Anatomy
- Histology
Background:
- Medullary bone (MB) is a temporary, sex-specific skeletal tissue unique to female birds during egg-laying.
- Its evolutionary origin is debated, with hypotheses suggesting it arose within Avemetatarsalia, potentially outside the Avialae lineage.
- Current diagnostic criteria for identifying fossilized MB may not fully encompass the variability observed in extant species.
Purpose of the Study:
- To investigate the phylogenetic breadth and structural diversity of medullary bone in extant birds.
- To reevaluate and refine existing criteria for identifying fossilized medullary bone.
- To reconsider previous identifications of MB-like tissues in fossil specimens based on new data.
Main Methods:
- Analysis of medullary bone distribution and structure in extant birds.
- Utilizing computed tomography (CT) and histochemistry for detailed microstructural and chemical analysis.
- Review and refinement of diagnostic criteria for fossil MB identification.
Main Results:
- New insights into the wide phylogenetic distribution and diverse microstructures of MB in modern birds (Neornithes).
- A refined set of criteria for confidently identifying MB in the fossil record.
- Reevaluation of prior MB identifications in fossil specimens, considering newly acquired data on variability.
Conclusions:
- The variability of MB in extant birds is greater than previously understood, necessitating updated diagnostic approaches.
- Refined criteria enhance the accuracy of identifying MB in extinct avemetatarsalians.
- This research advances the understanding of vertebrate palaeophysiology and avian skeletal evolution.
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