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WALKER AND BRETT—POST-PALEOZOIC PATTERNS IN MARINE PREDATIONColeoids.—Other nektonic organisms gave uparmor in exchange for more efficient swimmingduring the Mesozoic and Cenozoic (Vermeij, 1983).Soft-bodied coleoid cephalopods traded off externalarmor for increased speed and mobility and evasivedefenses, such as sepia ink for camouflage (Packard,1972; Lehmann, 1975). The majority of gastriccontents preserved in marine reptiles, however,consist of hooklets from belemnites, and few fromnaked cephalopods. While the belemnites did notsurvive the Cretaceous mass extinction, the softbodiedcoleoids did. They faced a renewed groupof predators in the Cenozoic—the marine mammals.Despite two revolutions in their predators, theirmorphology has remained remarkably static.Decapods and Ostracodes.—Little is knownabout predation on decapods during the Cretaceous.Evidence of drilling predation in Cretaceous toRecent ostracode assemblages from Texas includesdrillholes from juvenile naticid gastropods(Maddocks, 1988). It is not known if ostracodesdeveloped antipredatory armor, although theincidence of drilling appears to increase from theCretaceous into the Tertiary, but then declines inthe Holocene (Maddocks, 1988). It is thought thatsmooth shells may be preferentially drilled, or atleast may make drillholes more discernable to thepaleontologist (Maddocks, 1988). Because of theirabundance and worldwide distribution in a varietyof environments, ostracodes would provide animportant database from which to test the variousmarine revolutions; but they remain little studied.Echinoderms.—Regional large deposits ofcrinoid grainstones and packstones (encrinites) arenot present after the Jurassic (Ausich, 1997). Thepresence of regional encrinites since the Ordovicianillustrated the domination of many shallow-shelfenvironments by crinoids and other stalkedechinoderms perhaps for millions of years up tothe Jurassic (Ausich, 1997). Comatulid crinoidsevolved rapidly from the stalked forms during theLate Triassic–Early Jurassic (Meyer and Macurda,1977), but their diversity remained fairly low (fivespecies) during the Jurassic. Modern comatulidsare known to be preyed upon by reef fishes (Meyerand Ausich, 1983; Meyer, 1985). There is alsolimited information concerning predation oncrinoids during the Jurassic (Schneider, 1988). Theoffshore retreat of “primitive” groups, such asstalked crinoids, has been suggested to be a generaltrend that might be related to increased predationpressure (Jablonski et al., 1983; Vermeij, 1987;Bottjer and Jablonski, 1988; Jablonski and Bottjer,1990). For example, Meyer and Macurda (1977)documented an offshore migration of stalkedcrinoids during the Jurassic. This onshore-offshorepattern in crinoid distribution needs to be reexaminedin light of new data.Most isocrinids (except for Pentacrinitidae)lived in shallow waters until the Mid-Cretaceous,whereas in the Cenozoic these forms inhabiteddeeper water (Bottjer and Jablonski, 1988).In the Early Jurassic, the biggest evolutionaryinnovation in echinoderms appeared with the adventof irregular echinoids (Simms, 1990). The flattenedtests of these creatures are thought to have been anaptation that provided greater stability within thesubstrate. At the same time, the periproct movedaway from the apex of the test, in accord with theirsediment-eating habits. By the Middle Jurassic,endobenthic irregular echinoids had evolved andrapidly diversified. Today, their descendantscomprise nearly half of all extant echinoids (Simms,1990). The aboral spines and the anal sulcus of thesecreatures (e.g., Galeropygidae) were consistent withtheir endobenthic lifestyle (Simms, 1990). Theevolution of pencillate tube feet in these groupsallowed them to pick up finer sedimentary particlesvia mucous adhesion (Simms, 1990). A peri-oraltube foot also allowed them to expand into newtrophic realms. Was this endobenthic lifestyleprovoked by predation, or merely by the opportunityfor better feeding conditions? It should be noted thatepibenthic echinoids were also diversifying at thistime, with the Cassiduloids and their offshoots.Fish are the dominant predators of modernophiuroids (Aronson, 1988). Little is known aboutpredation on Mesozoic ophiuroids, although therate of arm regeneration appears to be low forJurassic compared to Recent ophiuroids (Aronson,1987, 1991). However, there is no clear evidencethat ophiuroids developed antipredatory armor, as151