Plankton Proliferate

Source Institution: Smithsonian National Museum of Natural History

Source Exhibit: David H. Koch Hall of Fossils - Deep Time

Source Url: https://naturalhistory.si.edu/visit/virtual-tour/current-exhibits/deep-time-virtual-tour-fossil-list

Source Kind: interpretive_topic_or_panel

Use: research inspiration only; SAGE will write original interpretation

Dossier Status: scientifically_enriched_concept_room_07

Plain Language Explanation: Some of the most important Cretaceous organisms were too small to see without magnification. Microscopic plankton formed the foundation of ocean food webs and left an enormous geological record. Coccolithophores—plankton covered in tiny calcium-carbonate plates—became especially abundant and diverse. Planktonic foraminifera also diversified, leaving shells that scientists now use to date rocks and reconstruct ancient oceans.

Evidence: Coccolithophore remains make up major Cretaceous chalk deposits.; Smithsonian collections contain extensive Cretaceous planktonic foraminiferal material.; Planktonic foraminifera evolved rapidly enough that their species distributions provide powerful biostratigraphic markers.; Their shell chemistry and species composition preserve information about ancient temperature and ocean conditions.

Examples From Collection: The visible Room 7 collection contains marine reptiles, fish, ammonites and other large organisms whose ecosystems ultimately depended on microscopic primary production.; Placenticeras meeki; Xiphactinus audax; Hesperornis regalis; Tylosaurus proriger

Collection Limit Note: The curated 18-object Room 7 specimen core contains no dedicated plankton microfossil object. SAGE does not invent one.

Common Misconception: Plankton are not one type of animal. The word describes organisms that drift in the water, including photosynthetic and heterotrophic organisms from very different lineages.

What Scientists Still Debate: Scientists continue reconstructing how plankton communities responded to Cretaceous warming, ocean stratification, anoxic events, nutrient changes and acidification.

Sources: https://ocean.si.edu/through-time/ocean-through-time; https://naturalhistory.si.edu/research/paleobiology/collections-overview/cushman-foraminifera-collection; https://naturalhistory.si.edu/research/paleobiology/research/huber-lab

Enrichment Method: SAGE original interpretive concept; Cretaceous ecosystems kept geographically and chronologically distinct; direct feeding evidence separated from functional inference; bird-dinosaur relationship represented phylogenetically