View - Kowalewski, M. - Virginia Tech

PALEONTOLOGICAL SOCIETY PAPERS, V. 8, 2002through the duration of the Cenozoic.Today, predatory and grazing reef fish in theIndo-Pacific alone comprise over 4000 species offish, representing 18% of all living fishes (Choateand Bellwood, 1991). The triggerfish(Tetraodontidae, Balistidae) are known to crushprey in their jaws. Triggerfish durophagousspecializations include the loss of jaw protrusion,enlarged jaw adductor muscles, and stout teeth.Sparidae (parrot fish) also crush corals and otherhard prey.Fish other than tropical reef fish can fragmentshell material (Cadée, 1968; Cate and Evans, 1994;Norton, 1995); although they may be responsiblefor a majority of fragmented shelly remains in thefossil record, direct evidence linking them to thescene of the crime is lacking. Alternatively, fishthat puncture shelly hardparts are known (Norton,1988), and it would be possible to trace this specifictype of shell damage in the fossil record, althoughthis has not been attempted.Sea snakes.—Sea snakes evolved from varanidancestors (as did mosasaurs) in the mid-to-LateCretaceous, and diversified greatly in the Cenozoic(Caldwell and Lee, 1997; Lee and Caldwell, 2000).From the Late Cretaceous to Eocene, there wereseveral genera of marine snakes representative ofthe booidean family Palaeophidae (Hecht et al.,1974; Heatwole, 1987). Early Tertiary fossils ofsea snakes are very abundant and globallywidespread. However, the Palaeophidae are not thedirect ancestors of modern sea snakes; rather, theFamily Elapideae (terrestrial, venomous snakes ofthe cobra family) is thought to have given rise tothe extant sea snake fauna between 35 and 25million years ago, in the Oligocene to Miocene.However, the modern genera are not well knownas fossils (Heatwole, 1987). The modern fauna ofsea snakes, Laticaudinae and Hydrophiinae, arecomprised of 12 genera and approximately 48species (Hecht et al., 1974) distributed chiefly insubtropical to tropical oceans. A few saltmarsh andestuarine snakes also occur in temperate NorthAmerica. Most sea snakes are nearshore creatures(within the 100 m isobath; Hecht et al., 1974).Although they not particularly well studied, it isthought that most sea snakes are piscivorous, with afew species that are “generalists”—that is, that feedon both fish and invertebrates such as crustaceansand molluscs (McCosker, 1975; Glodek and Voris,1982; Voris and Voris, 1983; Heatwole, 1987).Saltmarsh snakes (natricines) eat small fish andfiddler crabs; the granulated file snake (Acrochordusgranulatus) eats fish, crustaceans, and snails(Heatwole, 1987). Sea snakes swallow their preywhole, but it would be very useful to know what thetaphonomic quality of the invertebrates are once theypass through the gut of the sea snake. That is, whatsize fragments? Is there any indication of gastricacids on the fragments? How much do they eat ofvarying prey items?Sea turtles.—Cenozoic fossil turtles are knownfrom a number of localities dating from thePaleocene (Weems, 1988). The Chelonoidea firstappeared in the late Early Cretaceous and theCenozoic fauna includes the survivors of theCretaceous-Tertiary mass extinction: Dermochelyidaeand Cheloniidea (Hirayama, 1997). Ofthese, the Dermochelyidae, with their thin shellsand fontanellization, are poorly preserved;chelonids are better preserved, and are slightly betterknown (Weems, 1988). Despite this taphonomicproblem, no catastrophic terminal Cretaceous eventis evident in the record of sea turtles (Weems, 1988).Sea turtles had declined in diversity by the lateCampanian, and were low in diversity during theMaastrichtian and Danian, but recovered in theThanetian and Ypresian stages of the early Cenozoic(Weems, 1988). The cheloniids underwent a majordiversification in the late Paleocene (Weems, 1988).This pattern of diversity matches the global patternof oceanic cooling and warming in Late Cretaceousto early Tertiary time (Weems, 1988, p. 143, hisfig. 27). The later Tertiary sea turtles are too poorlyknown to allow us to extrapolate diversity at thistime, but in general, diversity declined from theEocene to the five cosmopolitan species remainigtoday (Weems, 1988).Although modern turtles are morphologicallysimilar, their feeding preferences differ: theCheloniidae are omnivorous, and herbivorous(Hirayama, 1997) adult green turtles (Chelonia162