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WALKER AND BRETT—POST-PALEOZOIC PATTERNS IN MARINE PREDATIONFIGURE 1—Ranges of various taxa of Mesozoic and Cenozoic durophagous (hard-shell crushing)predators. Thin lines: present, but of limited abundance; thick lines: abundant; broken lines: possiblypresent but rare as fossils.ammonoids, the ceratites are assumed to have beenpredaceous, although data are very sparse. Stomachor crop contents of ammonoids are very rare, butwhen they are found provide important evidencefor trophic relationships. One specimen of an EarlyTriassic ammonoid (Svalbardiceras) hadostracodes and foraminiferans among its gastriccontents and may have been a predatory nektoniccarnivore (Westermann, 1996, p. 675).Crustacea and Ostracodes.—The mostimportant post-Paleozoic groups of decapod,isopod, and amphipod crustaceans appeared in theLate Paleozoic, but they did not diversifysignificantly until the Jurassic (Briggs and Clarkson,1990). Four out of 27 Paleozoic families survivedinto the Mesozoic, and only a few groups are knownfrom the Triassic (Briggs and Clarkson, 1990).Various lobster groups evolved in the Triassic(Table 1). Their appendages indicate that they weredurophagous, but modern lobsters feed on a widevariety of prey and are not specialists on molluscanprey. Ostracodes are known to be predators on121