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PALEONTOLOGICAL SOCIETY PAPERS, V. 8, 2002premaxillary tusks, a deep-vaulted palette withoutteeth, and strong muscle scars on the premaxillae,which indicate durophagy (Muizon, 1993). Itsmorphology is similar to the Beluga and narwhalwhales (Monodontidae).The Suborder Mysticeti (baleen whales)originated in the Oligocene (Whitmore and Sanders,1976) and developed sheets of horn- or hair-likebaleen for sieving water to collect pelagic organisms,especially krill—a form of predation previouslyevolved by certain bony fish (e.g., Mesozoicpachycormids, and whale sharks) and perhaps by aTriassic marine reptile, the placodont Henodus. Allof these organisms attained large size, and mysticetewhales include the largest known organisms.While a number of cetaceans may eat somebenthic fauna, it is only the gray whale (Mysteceti,Eschrichtiidae, Eschrichtius robustus) thatconsistently raids the benthos in search ofinvertebrates (e.g., tubiculous amphipods andcallianassid shrimp) to complement its fare ofpelagic prey such as squids, mysid shrimp, and fish(Norris et al., 1983; Nerini, 1984). Gray whales arealso known to skim eelgrass mats for bothcrustaceans and sea grass/algae, and sandy muddyhabitats for gastropods, bivalves, and tube-buildingpolychaetes (e.g., Diopatra and Onuphis; Nerini,1984, her table 2). Buccinids, neptunids, thaids, andnaticids are just a few of the gastropods that havebeen found among gray whale stomach contents;Macoma, Mya, and Mytilus are some of the ingestedbivalves. The gray whale is able to sieve sedimentsthrough its thick baleen plates, which have coarserhairs than other baleen whales (Nemoto, 1970).Gray whales leave very large feeding pits inshallow, nearshore to intertidal mudflats that areoften the only record of their feeding behavior(Nerini, 1984, her fig. 1). On one benthic foragingdive, it is possible for one whale to make a series ofshallow pits that are usually arrayed in a slight curveand range from 1 to 3 m long and from 0.5 to 1.5 mwide. Gray whales are known to commonly feedin Baja California lagoons, along their migratoryrange from the Bering Sea to Baja California (a6000-km range), and in the northern Bering,Chukchi, and Beaufort Seas (Nerini, 1984). An entirepopulation of gray whales (estimated in 1984 at15,500 whales) could turn over 3,565 km 2 /yr of seabottom while feeding, considerably impacting thebenthic communities where they feed (Nerini, 1984).Gray whale fossils, however, are only knownfrom the late Pleistocene, although several closelyrelated groups are known from the Miocene of NorthAmerica (Barnes and McLeod, 1984). The obligatebarnacle parasite of gray whales, Cryptolepas, is alsoonly known from the late Pleistocene (Barnes andMcLeod, 1984). It is known that there were twoallopatric populations of the gray whale in the earlyHolocene, one in the North Pacific and one in theNorth Atlantic, which is now extinct.Order Sirenia (sea cows).—Sea cows date fromthe Eocene, and are a very small group of mammalsthat feed chiefly on sea grasses, algae, or waterhyacinths (Domning, 1976; Savage, 1976). Oneparticular fossil Sirenian, however, may have fedon benthic molluscs. Miosiren from the lateMiocene of Belgium displays thickened toothenamel and cusp modifications, which indicate thatit may have fed on molluscs (Savage, 1976).Other mammals that forage for marineinvertebrates.—Raccoons (Procyon) forage forcrustaceans in temperate to subtropical tidepoolsand salt marshes (Ricketts et al., 1985; Walker, pers.obs., 1997). The first known Procyon is from theupper Pliocene; there are several Pleistocene fossilspecies as well (Arata and Hutchison, 1964).Fossils of Procyon are known from all over thecontinental United States, as well as Baja Californiaand Canada (Arata and Hutchison, 1964). Coyotesand other mammals also can feed in the intertidalzone of temperate regions (Ricketts et al., 1985).Rats, in particular, can prey on over 40 differenttypes of intertidal organisms, especially key holelimpets, porcellanid crabs, and cancrid crabs(Navarrete and Castilla, 1993).Humans.—Lastly, the origination of humansin the late Pleistocene added to the potential forcoastal foraging and selection of particularinvertebrate food items as evidenced by abundantkitchen midden sites around the world, as well astools embedded in late Pleistocene coral reefs (seeWalter et al., 2000). Humans have been using sea166