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WALKER AND BRETT—POST-PALEOZOIC PATTERNS IN MARINE PREDATIONmydas) eat sea grasses and algae; the hawksbills(Eretmochelys imbricata) eat sponges, and Kemp’sridley (Lepidochelys kempii) eats crustaceans. TheDermochelyidae are rather fond of jellyfish.Caretta has massive jaws with a trituratingsurface; this genus is most common in temperatewaters, and the present distribution of this sea turtledates back to the early Pliocene (Dodd and Morgan,1992; Parris et al., 2000). Caretta eats sea pens,crustaceans, and molluscs among many other preyitems (Hendrickson, 1980; Plotkin et al., 1993;Nicholls, 1997). One species, Caretta caretta, theloggerhead turtle, is known to eat a variety of prey(Mortimer, 1982; Bjorndal, 1985). Caretta off theTexas shelf feed primarily on sea pens in the spring,and benthic crabs in the summer and fall (Plotkinet al., 1993). They can also eat molluscs,anthropogenic debris (e.g., fishing line, plastic trashbags), Diopatra tube worms, barnacles, fish,seaweed, whip coral, sea pansies, sea anemones,stomatopods, shrimp, and jellyfish (Plotkin et al.,1993). The small bivalve molluscs present in theirstomachs may come from the digested tubes ofDiopatra, and perhaps may not have been directlyfed upon. Scavenging gastropods that feed on deadfish or crabs, such as Nassarius acutus, may havebeen eaten accidently as the turtle went afterdecaying fish (Plotkin et al., 1993).Caretta populations from different geographicareas feed on different types of prey. In the westernMediterranean, Caretta caretta eat fish and tunicatesalps, although they can also eat benthiccrustaceans and molluscs (Tomas et al., 2001).However, the fish may be from scavenged by-catchthat is thrown overboard by fisherman. Caretta canalso forage on jellyfish at the ocean surface (Plotkinet al., 1993). The variety of prey that theseloggerheads eat is impressive, denoting a generalist(Plotkin et al., 1993). Of all the sea turtles that existtoday, Caretta is the only generalist.Sea and Shore Birds.—The extinction ofpterosaurs and early toothed diving birds in the LateCretaceous left open another important niche formarine piscivorous predators. It seems that thisvoid was filled rapidly by the evolution ofneognathan sea birds (Fig. 11.6). Aquatic birds areincluded among the oldest fossils of the DivisionNeognathae, with Late Cretaceous records for thetransitional shore birds (Feduccia, 1995). Severalorders of marine birds have fossil records extendingat least to the early Paleogene; these includeAnseriformes (ducks), Gaviiformes (loons), andCharadriformes (shore birds).Foot-propelled loons (O. Gaviiformes; LateCretaceous(?) to Recent) and grebes (O.Podicepiformes; Miocene to Recent) appear highlyconvergent on the Cretaceous ichthyornithines andhesperornithines, but are not closely related(Chiappe, 1995). Contrastingly, gliding albatrosses(O. Procellariformes; Eocene to Recent), some withwingspans exceeding 3.5 m, gulls (O.Charadriformes; Eocene to Recent), and pelicansand cormorants (O. Pelicaniformes; Eocene toRecent) seemingly fill a guild similar to theMesozoic sea-going, piscivorous pterosaurs.Finally, the penguins (O. Sphenisciformes; Eoceneto Recent) (Fig. 11.6), including some 25 genera,have an excellent fossil record, primarily in theSouthern Hemisphere (Simpson, 1975); diversefossils are especially common in the Eocene toMiocene of New Zealand and Seymour Island.These amphibious birds have become specializedfor rapid underwater flight even as they have lostaerial flying ability. Interestingly, an extinct cladeof flightless pelicaniform birds, the Plotopteridae(Eocene to Miocene), convergently evolvedelongate paddle-like wings for underwater flight.Some of the Pacific plotopterids attained lengthsof 2 m (Olson and Hasegawa, 1979). All of thesebirds are primarily piscivores and their abundanceattests to the proliferation of small teleost fish innear-surface seawater.The diversification of diving and other coastalmarine birds also may have greatly impacted thefossil record of crustaceans and molluscs (Vermeij,1977, 1987). Although several groups originated inthe Late Cretaceous, the diversification of shorebirds and diving marine birds took place chiefly inthe Paleogene (Vermeij, 1987). Oyster catchers,however, originated in the Neogene (Olson andSteadman, 1978). Diving marine birds catch fishthat had previously preyed on molluscs; the163