Status of Studies on Fossil Marine Mammals

Abstract

A 30-year renaissance in research on fossil marine mammals has brought advances on several fronts and suggests potential directions for future study. Gingerich and Russell have described Pakicetus, the most primitive archaeocete cetacean. Mchedlidze has described a diverse assemblage of late Oligocene/early Miocene cetaceans from the Caucasus and Georgia, S.S.R. Barnes and Fordyce, respectively, have outlined sequences of fossil cetacean assemblages in the northeast and southwest Pacific. Much remains to be done on origin and definition of cetacean suborders, diversification and systematics of families, and relationships among infra-familial taxa.New material has been recovered of the most primitive desmostylians, and other new specimens, especially ones from Japan studied by Inuzuka and others, give a relatively complete picture of their anatomy. Material now exists for phylogenetic analysis.Domning has proposed a phyletic lineage of the sirenian subfamily Hydrodamalinae and has outlined patterns of Late Cenozoic manatee evolution. With Morgan and Ray he reviewed Eocene sirenians in the northwest Atlantic. Numerous new specimens are being actively studied in attempts to reassess relationships within the Sirenia.Mitchell and Tedford described the most primitive otariid, Enaliarctos. Repenning and Tedford reviewed the otarioids. The primitive taxa and their origin near or in the amphicynodontine ursids have been identified. The zoogeography of true seals, the phocids, has been analyzed recently by Repenning, Ray and Grigorescu, and by de Muizon. Most taxa are based on a few fragmentary specimens, and much work needs to be done on basic descriptions, interspecific comparisons and phyletic analysis. However, major progress has been made in the southern hemisphere through description of extensive new materials from Peru and South Africa.Many important phylogenetic gaps in the fossil record of marine mammals have been filled recently, and further advances continue at a rapid rate. Studies lnvited plenary session paper presented at Fifth Biennial Conference on the Biology ofMarine Mammals, November 2 7-December 2, 198.3,

Morfologia do sincrânio do boto-cinza, Sotalia guianensis (P.J. van Bénéden) (Cetacea, Delphinidae)

“…Os gêneros Sotalia, Sousa e Steno Gray, 1846 já foram agrupados na família Stenidae, tendo por base a anatomia dos seios aéreos (FRASER & PURVES 1960), ou mais freqüentemente na subfamília Steninae, dentro da família Delphinidae, de acordo com caracteres do esqueleto (BARNES et al 1985). No entanto, a análise cladística das sequências de citocromo b indica um agrupamento diferente, onde Sousa aparece claramente separado dos outros dois gêneros (LEDUC et al 1999).…”

Behaviour and energetics of ice-breeding, North Atlantic phocid seals during the lactation period

“…Currently, a monophyletic origin, from an early seal-like animal, Enaliarctos mealsi, appears to be favoured (Berta et al 1989), although this view is far from universal (see Barnes et al 1985, Bonner 1989. Regardless of the precise affinities among the pinnipeds, it is clear that the earliest phocid fossils are from the mid-to late Miocene (12 to 15 million yr ago) and were found in the North Atlantic (True 1906, Lipps & Mitchell 1976, Barnes et al 1985.…”

New Sirenian Findings From Crete Island

“…The order Sirenia (Illiger 1811) is closely related with the group Tethytheria (a group of ungulate, hoofed mammals) that includes the extinct orders Desmostylia and Embrithopoda. The genus Paleoparadoxia is considered to be the ancestral line to all of them.The Sirenians probably were separated from their ancestral group during the Palaeocene (65-54 Ma) and very soon they entered the water fully adapting to aquatic life and dispersed to the New World (Barnes et al, 1985, Domning, 1978, 1999 (Domning, 1988(Domning, , 1997.…”