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| Diaphorocetus poucheti (Moreno, 1892)
in Paolucci, Buono, Fernández, et al., 2019.
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Abstract
Sperm whales (Physeteroidea) are the basal-most surviving lineage of odontocetes, represented today by just three highly specialized, deep-diving suction feeders. By contrast, extinct sperm whales were relatively diverse, reflecting a major Miocene diversification into various suction feeding and macroraptorial forms. The beginnings of this diversification, however, remain poorly understood. The Atlantic coast of South America provides a crucial window into early physeteroid evolution and has yielded some of the oldest species known from cranial material, Idiorophus patagonicus and Diaphorocetus poucheti – both of which are in need of re-description and phylogenetic reappraisal. Here, we re-examine Diaphorocetus in detail and, in light of its complex taxonomic history, declare it a nomen protectum. Phylogenetically, the species forms part of a polytomy including ‘Aulophyseter’ rionegresis and the two crown lineages (Physeteridae and Kogiidae) and demonstrates that facial asymmetry and a clearly defined supracranial basin have characterized this lineage for at least 20 Ma. With a total body length of 3.5–4 m, Diaphorocetus is one of the smallest physeteroids yet known. Its cranial morphology hints at an intermediate raptorial/suction feeding strategy and it has a moderately developed spermaceti organ and junk.
Keywords: Physeteroidea, Gaiman Formation, phylogeny, anatomy, body size, Miocene
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| Figure 10. Schematic reconstruction of Diaphorocetus poucheti. A, head in lateral view showing the nasal complex and proposed outline of spermaceti organ and junk, based on Zygophyseter varolai Bianucci & Landini, 2006; B, full body reconstruction. Drawing by Florencia Paolucci. |
Systematic palaeontology
Cetacea Brisson, 1762
Neoceti Fordyce & de Muizon, 2001
Odontoceti Flower, 1867
Physeteroidea Gray, 1821
Diaphorocetus Ameghino, 1894 nomen protectum
Diaphorocetus poucheti (Moreno, 1892)
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Florencia Paolucci, Mónica R. Buono, Marta S. Fernández, Felix G. Marx and José I. Cuitiño. 2019. Diaphorocetus poucheti (Cetacea, Odontoceti, Physeteroidea) from Patagonia, Argentina: One of the Earliest Sperm Whales. Journal of Systematic Palaeontology. DOI: 10.1080/14772019.2019.1605544
