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Lambert O.,CNRS Institute of Earth Sciences | Bianucci G.,University of Pisa | Urbina M.,Museo de Historia Natural UNMSM
Journal of Vertebrate Paleontology | Year: 2014

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. © 2014 by the Society of Vertebrate Paleontology.

Bianucci G.,University of Pisa | Urbina M.,Museo de Historia Natural UNMSM | Lambert O.,CNRS Institute of Earth Sciences
Comptes Rendus - Palevol | Year: 2015

An almost complete skull with associated periotics and one cervical vertebra from the Early Miocene strata of the Chilcatay Formation (Pisco Basin, Peru) is described here and referred to Notocetus vanbenedeni, a species previously recorded from Argentina, belonging to the extinct odontocete family Squalodelphinidae (Platanistoidea). The fossil was collected in the same locality and approximately the same stratigraphical horizon as Huaridelphis raimondii, suggesting the sympatric coexistence of two squalodelphinids during the Early Miocene along the Pacific coast of South America. Considering the new record here described, N.vanbenedeni lived both along the Atlantic and Pacific coasts of South America, two marine areas in wide contact during the Late Oligocene and Early Miocene. Despite the relative commonness of squalodelphinids in the Chilcatay Fm., the worldwide record of this family remains globally rather scarce and significant specimens were only found in Italy, France, along the East Coast of USA, Argentina, Peru, and possibly New Zealand. © 2014 Académie des sciences.

Valenzuela-Toro A.M.,University of Chile | Gutstein C.S.,University of Chile | Gutstein C.S.,Smithsonian Institution | Varas-Malca R.M.,Museo de Historia Natural UNMSM | And 2 more authors.
Journal of Vertebrate Paleontology | Year: 2013

Modern pinnipeds distributed along the coasts of continental South America consist almost entirely of otariids (sea lions and fur seals). In contrast, phocids (true seals) are present only on the southernmost extreme of Chile. This recent biogeographic pattern is consistent with the zooarchaeological record (∼8-2 ka), but it is incompatible with the pinniped fossil record during the Neogene. From the middle Miocene to the Pliocene, true seals exclusively dominated pinniped assemblages, and they were only replaced by the fur seals and sea lions sometime after the early Pliocene. Here, we describe pinniped material collected from two new localities in the Atacama Desert, northern Chile, that clarifies this marine mammal faunal turnover. Specifically, these finds provide records of the first occurrence of Otariidae (late Pleistocene) and the last occurrence of Phocidae (early Pliocene) in Chile, which in turn constrain the timing of this turnover to between the early Pliocene and late Pleistocene. The stratigraphic context of these findings provides new insights into hypotheses that explain this faunal turnover in South America, and we briefly discuss them in the context of turnover events involving other marine vertebrates throughout the Southern Hemisphere. © 2013 by the Society of Vertebrate Paleontology.

Lambert O.,CNRS Institute of Earth Sciences | Collareta A.,University of Pisa | Landini W.,University of Pisa | Post K.,Natuurhistorisch Museum Rotterdam | And 4 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2015

Although modern beaked whales (Ziphiidae) are known to be highly specialized toothed whales that predominantly feed at great depths upon benthic and benthopelagic prey, only limited palaeontological data document this major ecological shift.We report on a ziphiid–fish assemblage fromthe Late Miocene of Peru thatwe interpret as the first direct evidence of a predator–prey relationship between a ziphiid and epipelagic fish. Preserved in a dolomite concretion, a skeleton of the stem ziphiid Messapicetus gregarius was discovered together with numerous skeletons of a clupeiform fish closely related to the epipelagic extant Pacific sardine (Sardinops sagax). Based on the position of fish individuals along the head and chest regions of the ziphiid, the lack of digestion marks on fish remains and the homogeneous size of individuals, we propose that this assemblage results fromthe death of thewhale (possibly via toxin poisoning) shortly after the capture of prey from a single school. Together with morphological data and the frequent discovery of fossil crown ziphiids in deep-sea deposits, this exceptional record supports the hypothesis that only more derived ziphiids were regular deep divers and that the extinction of epipelagic forms may coincide with the radiation of true dolphins. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Gariboldi K.,University of Pisa | Gioncada A.,University of Pisa | Bosio G.,University of Milan Bicocca | Malinverno E.,University of Milan Bicocca | And 6 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2015

The Mio-Pliocene Pisco Formation (Peru) is a world-famous marine vertebrate Lagerstätte. Several fossil specimens are wrapped up in dolomitic nodules. Some others lie in the sediment displaying dolomite only in bone cavities (e.g., mesorostral canal and endocranium). With the aim to understand whether the precipitation of the dolomitic nodules influenced the formation of the Lagerstätte, we collected field data on a high number of fossil vertebrates and conducted petrographic and mineralogical analyses on samples representative of the variable development of concretions. Our results revealed positive relationships between size, completeness and articulation of skeletons and the presence of an external nodule. Clear evidence of chemoautotrophic communities that thrived on the carcasses is scarce. Microborings are often found in the cortical bone tissues together with iron oxides; the former are left by microorganisms feeding on the carcass, the latter are traces of former Fe sulphides, a product of organic matter degradation. We suggest that an early burial of the skeletons was a determinant factor in the development of dolomite concretions, since it allowed methanogenesis and anaerobic sulphate reduction exploiting the lipids in the bones and the organic matter dispersed in the sediments. Dolomite precipitation was driven by the same bacteria operating during the suphophilic stage of whale-fall communities. Textural observations imply that dolomite precipitated shortly after the burial of carcasses. The increase of alkalinity generated by sulphate reduction and methanogenesis caused a rapid precipitation of the dolomite within skeletal cavities and prevented the degradation of the bones and diagenetic compression of skeletons; the nodules themselves prevented erosion of fossils after exhumation. Therefore, nodule formation had a crucial role in the development of the Pisco Lagerstätte. © 2015.

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