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Stephen M. Reilly, Ronald Altig, Cranial Ontogeny in Siren intermedia (Caudata: Sirenidae): Paedomorphic, Metamorphic, and Novel Patterns of Heterochrony, Copeia, Vol. 1996, No. 1 (Feb. 2, 1996), pp. 29-41
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Reilly et al. (1996) studied this question.
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