An Eocene Jamaican sirenian retaining four substantial limbs and a strong sacroiliac connection alongside aquatic specializations. It informs the terrestrial-to-aquatic transition without being demonstrated to be a direct ancestor. [ref]
The earliest known fully quadrupedal sirenian by Daryl P. Domning. Nature 413, pp. 625–627; Pezosiren locomotor and aquatic character mosaic
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