[OANNES Foro] Macroraptorial sperm whales (Cetacea, Odontoceti, Physeteroidea) from the Miocene of Peru

[Mario Cabrejos]

Zoological Journal of the Linnean Society


.         First published: 7 September 2016 

.         DOI: 10.1111/zoj.12456 


 


Macroraptorial sperm whales (Cetacea, Odontoceti, Physeteroidea) from the
Miocene of Peru


.         Olivier Lambert, Giovanni Bianucci, Christian De Muizon


0.      


Abstract


The three extant sperm whale species, the giant Physeter macrocephalus and
the diminutiveKogia species, are relict members of the superfamily
Physeteroidea, whose evolutionary history is traced back to the late
Oligocene. Although well-preserved and diagnostic cranial remains are
relatively scarce, the physeteroid fossil record reveals a considerable
degree of morphological disparity (especially during the Miocene),
suggesting that sperm whales occupied a broader range of ecological niches
in the past. Here, we provide detailed descriptions and a (re)analysis of
several new and established middle-late Miocene stem physeteroids from the
Pisco Formation of southern Peru. In particular, we (1) further describe the
holotype of Acrophyseter deinodon from the latest Tortonian-Messinian of
Sud-Sacaco, with new information on previously unpublished portions of the
skull (including the ear bones) and a discussion of its masticatory
musculature; (2) diagnose a new species of Acrophyseter, A. robustus sp.
nov., based on a finely preserved skull with some associated cranial remains
from the late Serravallian-Tortonian (> 9.2 Ma) of Cerro la Bruja; (3)
provisionally refer a skull from Cerro los Quesos, which has been
radiometrically dated to the Messinian (6.9-6.7 Ma), to Acrophyseter sp.;
and (4) further describe the skull of the giant raptorial sperm whale
Livyatan melvillei from Cerro Colorado, recently re-dated to the Tortonian
(9.9-8.9 Ma) based on the associated diatom fauna and Ar/Ar dating. A
phylogenetic analysis based on 53 characters and 21 physeteroid species
confirms the monophyly of Acrophyseter and groups this genus with the
larger, middle to late Miocene macroraptorial stem physeteroids
Brygmophyseter and Zygophyseter. With its unique supracranial basin
morphology, Livyatan forms a separate, more crownward stem physeteroid
lineage. Combined with biostratigraphic information, our cladistic
hypothesis allows us to discuss the time of origin of the main physeteroid
clades, as well as trends in the evolution of their body size, dentition,
temporal fossa and supracranial basin.

 



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