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The extinct family Squalodontidae consists of heterodont, medium-sized odontocetes, featuring a long rostrum that houses large, procumbent incisors and heavily ornamented postcanine teeth carrying accessory denticles, hence their vernacular name, "shark-toothed dolphins". These longirostrine toothed whales are often seen as bridging the anatomical gap between archaic Oligocene odontocetes and their late Miocene to Holocene relatives. Possibly among the major marine predators of their time, the shark-toothed dolphins are important components of several lower Miocene marine-mammal assemblages from the North Atlantic and Mediterranean/Paratethysian realms. In the present work, a partial skull of Squalodontidae is described from the strata of the Bolognano Formation cropping out in the northeastern sector of the Montagna della Majella massif (Abruzzo, central Italy), which has previously yielded a rich lower Miocene marine-vertebrate assemblage, including eleven taxa of elasmobranchs as well as subordinate teleosts and very fragmentary remains of marine reptiles and mammals. The specimen consists of the anterodorsal portion of a rostrum, preserving parts of both premaxillae and left maxilla, and the anteriormost seven upper left teeth. This partial skull is here identified as belonging to the genus Squalodon, whose presence in the Montagna della Majella vertebrate assemblage had already been tentatively proposed on the basis of two fragmentary teeth. The paleontological significance of this find is discussed in the broader framework of the Euromediterranean record of Squalodon.

The early Miocene of Patagonia (Argentina) provides one of the best-known records of odontocetes for an age interval with scarce fossils. Most of these taxa are historically old and briefly described, which has contributed, in part, to their controversial taxonomic position. The shark-toothed dolphin Phoberodon arctirostris was described almost 100 years ago and suggested as a member of Platanistoidea and Squalodontidae. However, it has not been analysed recently and has never been included in a phylogenetic analysis. Recent fieldwork in the early Miocene sediments in Patagonia yielded a new specimen referred to this species, allowing for its modern and detailed description and the first phylogenetic analyses. Analyses recovered P. arctirostris as a stem Odontoceti or an early-diverging platanistoid, more closely related to an unnamed Oligocene specimen from New Zealand and not in a clade with Squalodon calvertensis (i.e. Squalodontidae). The reconstructed body length of P. arctirostris indicates that it is one of the largest stem Odontoceti. Our results suggest that during the early Miocene of Patagonia, archaic odontocete forms (i.e. P. arctirostris) cohabited with archaic and more crownward platanistoids (i.e. Aondelphis talen and Notocetus vanbenedeni), helping to characterize the early Miocene cetacean communities of Patagonia. Fil: Viglino, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Fordyce, Robert Ewan. University Of Otago; Canadá Fil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Fitzgerald, Erich M.G.. Museums Victoria; Australia

Summary The term “river dolphins” or platanistoids has been traditionally used to include four recent odontocetes ( Platanista , Lipotes , Inia , and Pontoporia ) that live in freshwater and coastal environments and are not members of the other clades of odontocetes: Delphinoids, ziphiids, and physeteroids. Although it was previously assumed that Platanistoidea were monophyletic, since 30 years morphological and molecular studies have established a consensus on the para- or polyphyly of this superfamily. The modern genus Platanista now appears to be the only survivor of an early diverging group of odontocetes, the Platanistoidea, which was diversified and widely distributed during the Oligocene and the Miocene. Whereas this clade is generally thought to include the modern and fossil Platanistidae, and the fossil families Allodelphinidae, Squalodelphinidae, and Waipatiidae, the phylogenetic relationships of other presumable platanistoids, namely, Prosqualodontidae and Squalodontidae, are more debated. The three other extant genera of “river dolphins” ( Inia , Lipotes , and Pontoporia ) are now unambiguously included in the Delphinida, branching before the Delphinoidea.

Most extant odontocetes appear to be anosmatic. However, some Miocene odontocetes, including a broken skull attributed to Squalodon sp. (Calvert Formation, Calvert Cliffs, Maryland, USA) preserve the osteological components associated with a well-developed sense of smell: dorsal nasal meatuses, ethmoturbinates within olfactory recesses, a perforate cribriform plate, and an olfactory bulb chamber. In Squalodon sp., the area within the olfactory recesses (i.e., covered in life by olfactory sensory epithelia) is 5367 mm 2 and the area occupied by the olfactory bulbs (i.e., the ethmoid area) is 769.8 mm 2 . In most mammals, the area of the olfactory epithelium is typically circa 16 times larger than the ethmoid area. The area covered by olfactory epithelium in CMM-V-2287 is only about seven times larger than its ethmoid area, less than half the area in typical mammals. During the Miocene, most odontocetes variously lost the osteological proxies indicative of osmatic ability. Perhaps biosonar surpassed the efficiency of olfactory cues during predation and social/parental/sexual interactions rendering the latter redundant/obsolete in odontocete analysis of, and interactions with and within their aquatic environments.

The two odontocete taxa Squalodon grateloupii and Patriocetus ehrlichii, both the type species of their respective genera, have been at the centre of a great deal of taxonomic confusion. Originally regarded to be conspecific, these two taxa have been the subject of a bewildering taxonomic debate lasting for more than a century, which recently led to the suggestion to abandon these widely used names and replace S. grateloupii with the similar, yet independently and later proposed name S. gratelupi as the type species of Squalodon. Here, we attempt to summarise the events leading to the current confused situation in the hope of resolving this issue once and for all and argue that the name Squalodon grateloupii, as originally proposed, should be reinstated.

Records of Tertiary fossil cetacea from New Zealand are revised. Probable proto‐squalodontid teeth from the McDonald Limestone Formation (Whaingaroan Stage, Lower Oligocene), Oamaru, are described, and represent the oldest cetacean remains found in New Zealand. This record demonstrates the probable extension of the Squalodontidae into the Lower Oligocene.

A new genus and species of squalodont cetacean, based upon a pair of incomplete mandibles, are described from Duntroonian (Upper Oligocene) sediments from Fossil Point, N.W. Nelson. The mandibles indicate a genus allied to Squalodon Grateloup but differing in the presence of a small median third root on the molariform teeth.

Barnes, Lawrence G. (Section of Vertebrate Paleontology, Natural History Museum of Los Angeles County, Los Angeles, California 90007) 1976. Outline of eastern North Pacific fossil cetacean assemblages. Syst. Zool. 25:321-343.-Geologic formations on the west coast of North America from Baja California, Mexico to central California, U.S.A., provide fossil evidence for a succession of Tertiary cetacean assemblages. Formations representing time periods of stage magnitude from early Miocene to Pleistocene age produce diverse aggregates of Cetacea containing fewer species than can now be found in latitudes corresponding to the Californian Province in the Pacific Ocean. Most fossil assemblages include a sperm whale, several dolphin-like taxa, and 3 or 4 baleen whales, although taxonomy is unstable, and many specimens cannot be assigned to named genera and species. New records of the earliest North Pacific occurrence of the families Balaenidae, Ziphiidae, Monodontidae, Phocoenidae, and Delphinidae (sensu stricto) date from the Miocene, and of the Eschrichtiidae from the Pleistocene. Squalodontidae are notable by their rarity. Early Miocene assemblages are dominated by Eurhinodelphidae, and late Tertiary ones by Stenodelphininae and primitive Balaenopteridae. On the generic level, there is a high degree of endemism among small Odontoceti, and a low degree among Physeteridae and Mysticeti. Collecting biases and deficiencies prevent recognition of antitropical distributions of fossil taxa, and paleoclimatology can not yet be inferred from the fossils. The status of the knowledge of fossil Cetacea in marine sedimentary deposits along the western border of North America is such that a summary and prospectus can now be formulated. A variety of Cenozoic fossil cetaceans are documented in the existing paleontologic literature, but these in no way reflect the real abundance of taxa or of specimens in the field or in museum collections. This article is in part, therefore, a summary of previously unrecorded specimens under study by the author (Barnes, 1972b). Mitchell (1966b) presented an earlier, more popularized overview of marine mammal evolution in the North Pacific Ocean. More fossil species are now represented by skulls and skeletons than previously, and some new interpretations of taxonomy and morphology are forthcoming in more detailed studies. These more complete specimens provide, in some cases, an opportunity for more precise determinations of phylogenetic and taxonomic relationships than was possible in the past for taxa founded upon fragmentary specimens. Kellogg (1923:38) has pointed out that comparisons among many fossil Cetacea have been hampered because of the lack of directly comparable parts of skeletons. Additionally, some taxa are described from skeletal parts having dubious taxonomic value. Cope (1868a, 1868b), Leidy (1851, 1869), and Deraniyagala (1969) have used isolated vertebrae and teeth, and Kellogg (1931) has used isolated periotics. In reality, both convergence and evolutionary conservativism may cause vertebrae and even teeth to be non-diagnostic in cetaceans. Even the isolated periotic has been proven, among Recent Cetacea, to sometimes be only generically and not specifically identifiable (Kasuya, 1973:72). This is particularly true for species of Kogia Gray, 1846 and for Delphinus bairdi Dall, 1873 and Stenella attenuata Gray, 1846 (see Kasuya, 1973:figs. 71-72). Recently, Ginsburg and Janvier (1971); and Hatai, Hayasaka, and Masuda (1963), have used isolated teeth and auditory bullae as holotypes. In light of such recent digressions in the quality of fossil cetacean systematics, I recommend that all subsequent cetacean holotypes include at least skull parts

Whitmore, F. C., Jr., and Sanders, A. E. (U.S. Geological Survey, National Museum of Natural History, Washington, D.C. 20244 and The Charleston Museum, 121 Rutledge Avenue, Charleston, South Carolina 29401). 1976. Review of the Oligocene Cetacea. Syst. Zool. 25:304-320.-Early in the Oligocene Epoch, Cetacea of the primitive suborder Archaeoceti had already declined sharply from their apparent abundance in Eocene seas. By the beginning of the Miocene, archaeocetes are known to have survived only in the northeast Atlantic and southwest Pacific Oceans. Concurrently with this decline, the first members of the suborders Odontoceti and Mysticeti appeared. They are known from only a few specimens, mostly in upper Oligocene deposits, on both coasts of North America, in Cermany, Austria, Italy, the Caucasus, Azerbaijan, Australia, and New Zealand. Two important odontocete genera, Agorophius and Xenorophus, come from beds that are probably no older than late Oligocene and that are certainly not as old as Eocene, where these genera have previously been placed. The wide distribution of known Oligocene Cetacea, especially their presence in Australia and New Zealand, indicates the probable existence of a cosmopolitan cetacean fauna by the end of Oligocene time. The Oligocene Odontoceti are represented by Agorophius and related forms and by the Squalodontidae. Several types of skull telescoping are shown by contemporary members of these groups. Recently collected squalodont skulls from the Oligocene of South Carolina show differences in the pattern of cranial bones that may be ontogenetic. Some toothed whales have morphologic features that have led to their being assigned variously to Archaeoceti and Mysticeti because they are regarded as representing a transitional stage between the two suborders. These forms are all of late Oligocene age; they cannot be mysticete ancestors because true Mysticeti are known from middle Oligocene deposits.