title: The rise of ocean giants: maximum body size in Cenozoic marine mammals as an indicator for productivity in the Pacific and Atlantic Oceans.
abstract: Large consumers have ecological influence disproportionate to their abundance, although this influence in food webs depends directly on productivity. Evolutionary patterns at geologic timescales inform expectations about the relationship between consumers and productivity, but it is very difficult to track productivity through time with direct, quantitative measures. Based on previous work that used the maximum body size of Cenozoic marine invertebrate assemblages as a proxy for benthic productivity, we investigated how the maximum body size of Cenozoic marine mammals, in two feeding guilds, evolved over comparable temporal and geographical scales. First, maximal size in marine herbivores remains mostly stable and occupied by two different groups (desmostylians and sirenians) over separate timeframes in the North Pacific Ocean, while sirenians exclusively dominated this ecological mode in the North Atlantic. Second, mysticete whales, which are the largest Cenozoic consumers in the filter-feeding guild, remained in the same size range until a Mio-Pliocene onset of cetacean gigantism. Both vertebrate guilds achieved very large size only recently, suggesting that different trophic mechanisms promoting gigantism in the oceans have operated in the Cenozoic than in previous eras.
authors.affiliation: Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, PO Box 37012, Washington, DC 20013-7013, USA Department of Paleontology, Burke Museum of Natural History and Culture, Seattle, WA 98195, USA pyensonn@si.edu.
authors.forename: Nicholas D
authors.identifier: 0000-0003-4678-5782
authors.initials: ND
authors.lastname: Pyenson
authors.affiliation: Department of Earth and Planetary Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Geerat J
authors.initials: GJ
authors.lastname: Vermeij
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D005075:Biological Evolution; D049628:Body Size; D020387:Food Chain; D005580:Fossils; D008322:Mammals / Q000033:anatomy & histology* / Q000502:physiology; D010140:Pacific Ocean
keywords: escalation; fossil record; gigantism; marine mammals; predators