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PALEONTOLOGICAL SOCIETY PAPERS, V. 8, 2002Stalk shedding is also a common occurrencein isocrinoids, and may be a deterrent to predators.Baumiller et al. (1999) hypothesize that crinoidshave evolved various antipredatory strategies sincethe Devonian: a planktonic (e.g., Uintacrinus) orpseudoplanktonic (e.g., Seirocrinus) lifestyle, stalksheddingabilities (e.g., in isocrinids, comatulids),short-bursts of swimming (e.g., comatulids), andlife in cryptic habitats (e.g., comatulids).Kier (1977) plotted global diversity ofechinoids through the Cenozoic, and showedlimited diversity in the Paleocene and OligoceneEpochs, with peaks in echinoid diversity in theEocene and Miocene–Pliocene Epochs; the recordof regular echinoids was not as good as that ofirregular echinoids. Regular echinoids arecommonly fragmented, and their fragments usuallyare not studied by taxonomists (Greenstein, 1993)or are not collected (Oyen and Portell, 2001).Clypeasteroids evolved in the Paleocene anddiversified rapidly, aided by the evolutionaryinnovation of numerous small tube feet and spinefreebranching food grooves. Flattening of the testmeant that only the top fraction of the sedimentcould be sieved for food particles (Kier, 1982).Records of predation on Cenozoic echinoidsare rare, even though in modern seas predation onechinoids is well documented (Nebelsick, 1995,1999). Drilled echinoid tests are known from theEocene Upper Ocala Formation in North CentralFlorida (Gibson and Watson, 1989). Some of thesedrillholes were predatory; others were parasitic.Parasitic eulimids are known to drill the aboralsides of echinoids; commonly an echinoid displaysmultiple drillholes made by parasitic gastropods(Berry, 1956). Cassid drillings on irregularechinoids are known from the Eocene of theAtlantic Coastal Plain (Woodcock and Kelley,2001) and elsewhere (see Cassid review, thispaper). Sand dollars (Parascutella hobarthi) fromthe lower Miocene of the Austrian Molasse Zonedisplayed repaired scallop-shaped areas on theirtests resulting from predation, possibly by regularechinoids (Nebelsick, 1999). Lethal predation wasindicated by large round holes cutting through theechinoid test or by bite marks penetrating the oralsurface (Nebelsick, 1999). Fish bite marks onclypeasteroid echinoids are also reported from theupper Miocene of Argentina (Zinsmeister, 1980).In the modern Atlantic and Gulf region, thereare 95 asteroid species in 56 genera, with adepauperate (because of lack of work) record inthe Cenozoic Caribbean region dating to the earlyPaleocene (Donovan, 2001). Asteroids are knownfrom the Eocene to Pleistocene in Florida, and insome horizons their fragments are very abundant(Oyen and Portell, 2001). Amazing preservation ofcomplete specimens of Heliaster microbranchius isknown from the Pliocene of Florida (Oyen andPortell, 2001).Ophiuroids are one of the most diverse extantechinoderm groups in the Caribbean region, buthave a “poor” fossil record because of their easilydisarticulated skeletons and a lack of work on thesecreatures (Donovan, 2001; Oyen and Portell, 2001).Nonetheless, a number of dense stalked crinoidophiuroidassociations are known from before theJurassic; a near absence of these dense assemblagesafter the Jurassic was postulated to be due topredation pressure (Aronson, 1987, 1991).Intriguingly, however, the Tertiary La MesetaFormation, Antarctic Peninsula, contains localizeddense assemblages of autochthonous ophiuroidsand crinoids representing shallow-water facies(Aronson et al., 1997). The incidence of sublethalarm injuries was low in this assemblage, suggestingthat predation was rare; possibly in high latitudecool-water areas predation is suppressed.Molluscs.—Molluscs provide the mostimportant Cenozoic database for examiningevolutionary questions regarding the fossil recordof predation because they are globally widespread,very abundant, well preserved, and present in manydifferent facies. Therefore, most studies havefocused primarily on escalation in marine molluscs.Shell repair and shell drilling in molluscs haveprovided the database by which to examinePhanerozoic predatory trends. Shell repair data hasnot been applied with as much success as drillingpredation, most likely because shell repair can bea consequence of a variety of physical andbiological destructive factors. Shell repair may168