The deep-sea microfossil record of macroevolutionary change in plankton and its study

Abstract

The deep-sea planktonic microfossil record (foraminifera, coccolithophores, diatoms, radiolaria and dinoflagellates) provides a unique resource for palaeobiology. Despite some geographical gaps due to poor regional preservation, and intermittant time intervals lost to erosion, most time periods for each Cenozoic planktonic biogeographical province are preserved. Vast numbers of specimens and numerous deep-sea cores provide abundant material and the opportunity to tightly integrate macroevolutionary and palaeoenvironmental data. Current documentation of this record is mixed. Catalogues for foraminifera and coccolithophores offer nearly complete species-level clade histories, but taxonomy for siliceous microfossils is incomplete. Published occurrence data is primarily stratigraphic and covers only a fraction of the total preserved diversity. Age models for some sections are excellent (accuracy c. 100 kya) but for many other sections are still poor. Taxonomic errors, age model errors and reworking displace fossil occurrences in time, complicating palaeobiological analysis. With additional taxonomic work, careful collection of whole fauna/floral assemblage occurrence data, improved age models, and the development of better data filtering and analysis tools to deal with data outliers the deep-sea microfossil record can deliver its promise of providing the most complete, detailed record of macroevolutionary change available to science.

The Paleocene record of marine diatoms in deep-sea sediments

“…The discrepancy between previous estimates of Paleocene planktonic diatom diversity and the one computed here highlights once again the systematic underreporting of taxa in the literature and the need to report biodiversity for the sake of biodiversity, and not as a by-product of stratigraphic analyses (Lazarus, 2011) in order to study macroevolutionary patterns.…”

Origin of the Eocene planktonic foraminifer Hantkenina by gradual evolution

“…The stratigraphic ordering provided by these studies gives us constraints on the pathway taken by evolution, its timescale and geographical range. The presence of ‘transitional’ Hantkenina in both Europe and East Africa suggests that the evolution did not occur in a peripheral isolate but rather across a broad area, as is perhaps to be expected in populations of oceanic plankton (Lazarus ). The current lack of evidence of transitional hantkeninids from the Pacific Ocean cannot be regarded as good evidence of absence because the relatively few sites that might yield such forms have not so far been sampled in sufficient detail (although we note in passing that our own detailed sampling of equatorial Pacific ODP Site 865 failed to yield transitional forms, possibly because of a small hiatus at the expected level).…”

Morphospaces and Databases: Diatom Diversification through Time

“…Marshall 1990), but the record of marine microfossils is so unusually rich that the opposite has been suggested for the Neptune database. Marine microfossils can appear outside of their true range due to "RATs", that is, because of the physical reworking of sediments (erosion and redeposition in a stratigraphically younger position), errors in the age model assigning a fossil occurrence to the wrong time bin, or taxonomic error (Lazarus 2011). For the curve that has become the canonical depiction of diatom diversity, these problems were addressed by manually excluding occurrences in Neptune considered unreliable, including occurrences near depositional hiatuses (Spencer-Cervato 1999).…”