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Analysis of a fossil suggests Kryoryctes may represent early monotreme evolution, indicating complex lineage relationships.
A partial humerus of Kryoryctes cadburyi Pridmore et al. 2005 characterised as "tachyglossid-like" but 100 million years older than the oldest known tachyglossid (echidna) fossil, is likely to be a stem monotreme. However, there are a few features of the fossil more reminiscent of a therian than a monotreme.
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RICH et al. (2026) studied this question.
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