View - Kowalewski, M. - Virginia Tech

PALEONTOLOGICAL SOCIETY PAPERS, V. 8, 2002The methods part of this volume shows thatthe methodological dimension of research on thefossil record of predation is a rapidly growing fieldof study, with many promising future researchdirections—particularly through laboratoryexperiments, observations in present-dayecosystems, and numerical modeling. Clearly, weneed to continue improving our statistical tools andanalytical strategies and to work together onerecting some general methodological guidelinesfor studying the fossil record of predation.PATTERNSThe chapters included in the second part of thisvolume impressively document the range ofevidence related to predator-prey interactions thathas been amassed by paleontologists. However,these studies also point to the numerous temporaland taxonomic gaps in our current knowledge.The fossil record of microorganisms providesinsights into primary producers and secondaryconsumers in marine ecosystems over the last 3.8+billion years, and points to a long-term increasein the complexity of trophic structures of marineecosystems through the history of life (Lipps andCulver). In particular, the trophic strategy ofendosymbiosis between animals and microbes,especially photosynthesizing algal eukaryotes,seems to have long played an important role inmarine ecosystem development and the evolutionof organisms (Lipps and Culver).The marine invertebrate fossil record offers aspectacular wealth of evidence relating to predatorpreyinteractions, including trace fossils, coprolites,and functional morphology of prey and predators(Brett and Walker; Walker and Brett). Thesepredatory records suggest that long-termevolutionary changes in predation pressure arelinked to episodes of abrupt biotic reorganizationduring and after mass extinctions, punctuatinglonger interludes of relative stability (Brett andWalker; Walker and Brett). Moreover, the evolutionof predation in the pelagic realm may have beenlargely decoupled from its evolution in benthicecosystems. The data from the marine fossil recordmake a strong case for the existence of predatoryattack on shelled organisms as early as the latestPrecambrian and the early Cambrian—with afurther intensification of predation during themiddle Paleozoic paralleled by increases inspinosity and other potentially defensive traits ofthe prey skeleton (Brett and Walker). In contrast,late Paleozoic forms may have taken refuge insmaller size and resistant, thicker-walled skeletons(Brett and Walker). Following the end-Permianmass extinction, the data suggest episodic, butgenerally increasing, predation pressure on marineorganisms through the Mesozoic-Cenozoicinterval. Predation in benthic communities mayhave intensified substantially in the LateCretaceous–Early Cenozoic with the evolution ofneogastropods, varied crustaceans, anddurophagous fish. In the early to mid-Mesozoic,large-predator guilds were filled predominantly byvaried marine reptiles; whereas neoselachiansharks, teleosts, and marine mammals dominatedin similar roles throughout the Late Cretaceous toCenozoic (Walker and Brett).The marine invertebrate record also suppliesevidence relating to parasite-host interactions,with a nearly even distribution of reported casesthrough the post-Cambrian Phanerozoic(Baumiller and Gahn). However, in few of thereported examples can we explicitly distinguishparasitism from predation, commensalism, ormutualism; and only in exceptional cases (suchas interactions involving platyceratids andcrinoids) is the evidence for parasitic interactionssufficiently compelling (Baumiller and Gahn).Terrestrial and freshwater invertebrates alsoprovide a diverse fossil record of predation,parasitoidism, and parasitism—with evidence forcarnivory (i.e., taxonomic affiliation, fossilstructural and functional attributes, organismicdamage, gut contents, coprolites, and mechanismsindicating predator avoidance) occurring from themid-Paleozoic to the Recent (Labandeira).However, only 12 invertebrate phyla have becomecarnivorous in the continental realm and only thetwo most diverse groups (nematodes andarthropods) left behind a comparatively goodfossil record (Labandeira).396