Bohaskaia monodontoides, a new monodontid (Cetacea, Odontoceti, Delphinoidea) from the Pliocene of the western North Atlantic Ocean

Two new extinct basal phocoenids (Cetacea, Odontoceti, Delphinoidea), from the upper Miocene Koetoi Formation of Japan and their phylogenetic significance

“…If the sister relationship between Phocoenidae and Monodontidae is correct, we would have to interpret many of the unequivocal morphological synapomorphies shared by Phocoenidae and the Delphinidae to be convergent or that they are lost secondarily in Monodontidae. As compared with Delphinidae and Phocoenidae, the cranial morphology of Monodontidae is more specialized and their fossil record is poor (only two valid taxa are known; Denebola brachycephala Barnes, 1984, andBohaskaia monodontoides Vélez-Juarbe andPyenson, 2012). Future discoveries of more basal monodontids may resolve the contradiction between morphological and molecular phylogenetic analyses on Delphinoidea.…”

First monodontid cetacean (Odontoceti, Delphinoidea) from the early Pliocene of the north‐western Pacific Ocean

“…It is not certain how taxonomically diverse monodontids were in the past because of their meagre fossil record. To date, the firmly established pre‐Pleistocene monodontid records have been known from four localities in the world: the late Miocene of Mexico (Baja California), the early Pliocene of Belgium (North Sea basin), and the Pliocene Yorktown Formation of North Carolina and Virginia (USA) (Barnes ; Lambert & Gigase ; Whitmore & Kaltenbach ; Vélez‐Juarbe & Pyenson ). There is a single periotic from the early Pliocene of Peru (Sacaco basin) (Muizon & Devries ), putatively assigned to a monodontid (Vélez‐Juarbe & Pyenson ).…”

“…Discoveries of fossils from the mid to low latitudinal areas indicate that the ancestral species of monodontids, now cold‐water‐adapted species in the north polar region (confined to Arctic and subarctic waters), may have preferred warmer waters (Vélez‐Juarbe & Pyenson ) but the idea may need a revision. Here, we describe a new species of monodontids from the early Pliocene of Hokkaido, the northernmost island of Japan (Fig.…”

“…SMAC1390 can be confidently identified as a member of the family Monodontidae based on the following characters: exposure of the maxilla along the medial wall of the osseous nasal opening (Muizon ); opening of the posterior accessory foramen at the posterior end of the premaxilla ( sensu Vélez‐Juarbe & Pyenson ); large zygomatic process relative to the skull (Barnes ); existence of the groove margined with sharp ridges on the ventral surface of the frontal, which is a lateral continuation from the frontal groove of the orbitosphenoid; transversely wide and weakly ventrally protruded posterior portion of the palate consisting of the palatine, the pterygoid, and the posterior part of the maxilla; the palatine widely separating the right and left pterygoid hamuli; the orbit situated well anterior to the osseous nasal opening; and the orbitotemporal crest extending gently posterodorsally from the posterior end of the postorbital process of the frontal, with no abrupt change of direction of the ascending process of the maxilla and the underlying frontal at the level of the postorbital process of the frontal in the facial portion, resulting in the anteroposteriorly elongated temporal fossa.…”

Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae)

“…The fossil record of monodontids is limited, but individuals have been found in lower latitudes, suggesting that extant species’ cold‐water adaptations and restrictions may have evolved relatively recently. The two described extinct species, Denebola brachycephala Barnes, and Bohaskaia monodontoides Vélez‐Juarbe & Pyenson, ; are from the Miocene Almejas Formation of Baja California, Mexico, and the Pliocene Yorktown Formation of Virginia, USA, respectively, indicating that monodontids were present at least by the late Miocene. Molecular divergence times suggest monodontids and phocoenids diverged 10.82–20.12 Ma, and D. leucas and M. monoceros diverged from each other 2.73–10.23 Ma, in agreement with the fossil evidence.…”