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 Hydro-damalinae 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 of zoogeography, functional anatomy and paleoecology, in addition to phylogeny, are coming into their own and promise an exciting series of discoveries in the coming years.