Wednesday, September 10, 2014

[PaleoMammalogy • 2014] Huaridelphis raimondii • A New early Miocene Squalodelphinidae (Cetacea, Odontoceti) from the Chilcatay Formation, Peru


 skull and partial mandible of the new squalodelphinid species Huaridelphis raimondii, with an outline of the head and potential fish prey.
photo: G. Bianucci | DOI: 10.1080/02724634.2014.858050

ABSTRACT
The fossil record of odontocetes (toothed cetaceans) is relatively scarce during the Oligocene and early Miocene compared with later in the Miocene and Pliocene; most of the odontocete families from these epochs are known by a limited number of species and specimens. Among those, Squalodelphinidae is a family of small- to medium-sized platanistoids with single-rooted teeth, which until now has included only four genera based on diagnostic material, from the early Miocene of Europe, Argentina, and North America. Recent field work in the Pisco-Ica desert, southern coast of Peru, has resulted in the discovery of several marine vertebrate-rich localities in various levels of the late Oligocene–early Miocene Chilcatay Formation. Based on three specimens from Ullujaya and Zamaca, including two well-preserved skulls with periotics, we describe a new squalodelphinid genus and species, Huaridelphis raimondii. This new species increases the early Miocene diversity of the family and is also its smallest known member. It further differs from other squalodelphinids by its thin antorbital process of the frontal, abruptly tapering rostrum, and higher tooth count. A more fragmentary skull, from Zamaca, is referred to Squalodelphinidae aff. H. raimondii. This skull provides information on the morphology of the tympanic, malleus, and incus, currently unknown in H. raimondii. Focusing on platanistoids with single-rooted teeth, our phylogenetic analysis suggests that Squalodelphinidae are monophyletic and confirms the sister-group relationship between the latter and Platanistidae. The relationships within Squalodelphinidae are not fully resolved, but H. raimondii might be one of the earliest diverging taxa.


 the skull of the new squalodelphinid species Huaridelphis raimondii in dorsal and lateral view.
photo: G. Bianucci 

Etymology— From ‘Huari,’ ancient culture of the south-central Andes and coastal area of Peru (500–1000 AD), and from ‘delphis,’ the Latin word for dolphin. Gender masculine. The species name honors Antonio Raimondi (1826–1890), an Italian scientist who first documented fossil whales from Peru (Bianucci, 2010).


The examination of fossil cetacean remains in the locality of Ullujaya, Pisco Basin, Peru.
photo: G. Bianucci 



CONCLUSIONS
Based on three specimens, including two well-preserved skulls, from early Miocene localities of the Chilcatay Formation (Ullujaya and Zamaca), Pisco-Ica desert, southern coast of Peru, we describe a new genus and species of Squalodelphinidae, Huaridelphis raimondii. In addition to periotic characters, H. raimondii differs from other known squalodelphinids in, among others, its smaller size, the thin antorbital process of the frontal, the more abrupt tapering of the rostrum, and the higher tooth count. Another fragmentary skull from the Chilcatay Formation in Zamaca is referred to Squalodelphinidae aff. Huaridelphis raimondii. It brings additional information on the morphology of the tympanic, malleus, and incus, not yet known in H. raimondii. Our phylogenetic analysis of platanistoids with single-rooted teeth suggests that the family Squalodelphinidae is monophyletic; the analysis also confirms the sister-group relationship between the latter and Platanistidae. The relationships within Squalodelphinidae are not fully resolved, but H. raimondii might be one of the first diverging taxa of the family.


Olivier Lambert, Giovanni Bianucci & Mario Urbina. 2014. Huaridelphis raimondii, A New early Miocene Squalodelphinidae (Cetacea, Odontoceti) from the Chilcatay Formation, Peru
 Journal of Vertebrate Paleontology. 34(5); 987-1004.
DOI: 10.1080/02724634.2014.858050 

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