Diaphorocetus

Diaphorocetus was originally named Mesocetus by Moreno (1892).^[2] Lydekker (1893) found that Mesocetus was already in use for an extinct mysticete, so he renamed the sperm whale Hypocetus.^[3] Ameghino (1894) too recognized Moreno's name as preoccupied, but unaware of Lydekker's paper, coined his own replacement name Diaphorocetus for Mesocetus.^[4] Diaphorocetus was declared a nomen protectum (protected name) by Paolucci et al. (2019) because Hypocetus and Paracetus have not been used as valid since 1899 under Article 23.9 of the Code.^[5]

With a total body length of 3.5–4 m, Diaphorocetus is one of the smallest physeteroids yet known.^[6] The small teeth of Diaphorocetus and the bottleneck-like nature of the rostrum suggest that Diaphorocetus employed a feeding strategy intermediate between that of raptorial sperm whales like Acrophyseter and Livyatan and extant sperm whales.^[5]