Marine mammals are key components of aquatic ecosystems. Feeding strategies identified in extant cetaceans, pinnipeds, sirenians, marine otters, and polar bears are associated with anatomical specializations of the head (rostrum, palate, temporomandibular joint, teeth/baleen, mandible). Genetic and ontogenetic evidence of skull and tooth morphology provide the mechanisms that underlie patterns of feeding diversity.

Based on a comprehensive diversity data set derived from the Paleobiology Database, we considered feeding strategies (suction, biting, filter feeding, grazing), prey type (squid, fish, benthic invertebrates, zooplankton, tetrapods, sea grasses), tooth pattern and cusp shape (homodont, heterodont, pointed, rounded, edentulous), and habitat (marine, riverine, estuarine) in fossil and extant marine mammals. These variables were then tested for correlation and their changes through time examined in relation to productivity and climate variables.

We provide an integrated analysis of the evolution of feeding and trophic structure in marine mammals and explore the origin and timing of particular feeding strategies over the last 50 million years. In agreement with earlier reports, updated generic counts reveal that the greatest diversity of pinnipedimorphs and cetaceans occurred during the late Miocene (Tortonian), following the Mid-Miocene Climatic Optimum. These historical data are used as a framework to inform past and present structure and trophic interactions and enable predictions about future marine ecosystems.

The drivers of diet and feeding patterns are both environmental (sea level fluctuations, climate change) and biotic (anatomical specializations, competition, predator-prey). The influence of these processes on paleodiversity varies depending on taxonomic group, timing, and geographic scale.

Generic and ecological diversity through time
Raw taxon counts for 61 extant and 374 fossil marine mammal genera recorded at the level of geological stage were downloaded from the Paleobiology Database (PBDB, www.paleobiodb.org). The search was performed separately for the following groups: “Archaeoceti, Cetacea”, “Pinnipedomorpha”, “Sirenia”, “Desmostylia”, “Thalassocnus”, “Ursus maritimus, Kolponomos”, “Aonychini, Aonyxini, Enhydra, Enhydrini, Enhydriodontini, Lontra, Lutra, Pteronura, Siamogale” (sea otters). Occurrences for each group were downloaded for each time bin (geological stage), starting from the Ypresian (early Eocene), using the “major (default)” time rule. Only occurrences with certain generic assignment were considered (“genus_certain”). The data include all occurrences entered up to 12/31/2017. Since geological stages in the Pleistocene and Holocene result in time bins that are of much shorter duration than any of the other stages, creating few occurrences in each of these time intervals, we followed Peredo and Uhen (2016) in binning the Pleistocene stages along with the Holocene series in the Quaternary, which at 2.6 Ma, is comparable in length to earlier time bins. Accessory data were also downloaded for these records, such as depositional environment and published sources, to allow verification of each occurrence individually and to be able to use the published references as a starting point to assign genera to the different categories. Diversity plots were obtained by counting the valid genera for each time bin in each group or family after the categorization was completed.

To quantify changes in ecological parameters and niche occupation through time, categories for each of the following ecological parametrs were assigned to each taxon: habitat preference, prey type, prey catupr strategy, tooth pattern and cusps shape. References are provided for each taxon to justify assignment. Additional details on categorization can be found in the Materials and Methods section of the paper.

Statistical Analyses for Environmental Drivers
Data for climatic variables  (δ¹⁸O, δ¹³C, sea level changes) was collected from publications (Prokoph et al., 2008 - Miller et al., 2005). Data for diatom diversity at species level was downloaded from the Neptune database on 03/05/2018. Processing of these data is explained in the Materials and Methods section of the paper.

Ancestral state reconstruction
Full matrices used for ancestral state reconstruction of each ecological parameter are provided for Pinnipedimorpha and Cetacea. Details on these analyses and on the topology used can be found in the Materials and Methods section and in the Appendices of the paper.

This dataset can be reused as-is. For more details on the ecological parameters and category assignment can be found in the main publication.