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Diaphorocetus poucheti
Diaphorocetus poucheti

[Image: 640px-Diaphorocetus_poucheti.jpg]
Mesocetus poucheti = Diaphorocetus poucheti by Moreno in 1892

Temporal range: Early Miocene (Deseadan-Colhuehuapian) ~23.03–20.43 Ma 

Scientific classification
Kingdom:  Animalia
Phylum:  Chordata
Class:  Mammalia
Order:  Artiodactyla
Infraorder:  Cetacea
Superfamily:  Physeteroidea
Family:  incertae sedis
Genus:  †Diaphorocetus  Ameghino, 1894
Species:  Diaphorocetus poucheti (type)

Diaphorocetus is an extinct genus of odontocete cetacean belonging to Physeteroidea. Its remains were found in the Monte León Formation of Argentina, dating to the Early Miocene.

Diaphorocetus was originally named Mesocetus by Moreno (1892). Lydekker (1893) found that Mesocetus was already in use for an extinct mysticete, so he renamed the sperm whale Hypocetus. Ameghino (1894) too recognized Moreno's name as preoccupied, but unaware of Lydekker's paper, coined his own replacement name Diaphorocetus for Mesocetus. 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.

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.

Journal Reference:
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

[Image: Diaphorocetus_poucheti-%2528Moreno_1892%...nWhale.jpg]
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.


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.
[Image: wildcat10-CougarHuntingDeer.jpg]
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