Mesozoic Survivors


Ancestry: Coccolithophores -> Mesozoic Survivors
Sister taxa: advancedsearch.php, Isochrysidales, Coccolithales, Zygodiscales, Syracosphaerales, Coccolith families inc sed, Mesozoic Survivors, Holococcoliths, Braarudosphaerales, Discoasterales, Nannolith families inc sed, hidden,

Short diagnosis: Mesozoic taxa which occur in low abundances in the early Palaeogene.


Daughter taxa (blue => in age window 0-300Ma) Granddaughter taxa
Placoliths with two broad shields; central area narrow; distal shield formed from V-units; proximal shield and tube formed from R-units.

Loxolith coccoliths with variably-developed proximal/inner-cycles and a central-area spanned by axial, non-axial or diagonal crossbars or a single transverse bar. LM image includes both unicyclic and bicyclic types. Outer rim clockwise-imbricate.

Circular placoliths with moderately birefringent shields, bright inner tube cycle and narrow or closed central areas.

Placoliths or modified placoliths with R-unit well developed, forming proximal and distal shield elements with opposite senses of imbrication; the V-unit typically forms a narrow distal cycle near the inner edge of the shield. Central-area structures are typically disjunct. Birefringent LM image, in which the V-unit cycle appears only as a thin, dark line.

Taxonomy:

Citation: Mesozoic Survivors sensu Young & Bown, 1997
Rank: informal group
Notes & discussion: Mesozoic survivors are nannoplankton that survived the K-Pg mass extinction event 65.5 Ma. Many of these taxa are discussed in more depth in the Mesozoic section. Other survivor taxa include Calciosolenia and Braarudosphaera.

Farinacci & Howe catalog pages: Mesozoic Survivors [no catalog entry yet]

Short diagnosis: Mesozoic taxa which occur in low abundances in the early Palaeogene.


Evolution & Phylogeny: Useful discussion of the K/Pg extinctions effect on nannoplankton include: Bramlette & Martini (1964); MacLeod et al. (1997); Mai et al. (1997); Burnett (1998); Pospichal (1996); Bown (2005);Medlin et al. (2008);Jiang et al. (2010); Schulte et al. (2010);

Search data:
TagsLITHS: murolith, placolith, H: cavate,
MetricsLith size: 3->13.5µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

See also: Braarudosphaera bigelowii ;Calciosolenia ;Cruciplacolithus primus - other Cretaceous survivors, in major groups;

Geological Range:
Notes: Most of these taxa only occur in the Palaeocene, however, the Watznaueriacean cocolith Tergestiella adriatica is now known to still be extant (Hagino et al. 2015).
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): within Bajocian Stage (168.28-170.30Ma, base in Bajocian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R., (2005). Selective calcareous nannoplankton survivorship at the Cretaceous-Tertiary boundary. Geology, 33(8): 653-656.

Bramlette, M.N. & Martini, E., (1964). The great change in calcareous nannoplankton fossils between the Maestrichtian and Danian. Micropaleontology, 10(2): 291-322.

Burnett, J.A., (1998). Upper Cretaceous. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 132-199.

Hagino, K.; Young, J.R.; Bown, P.R.; Godrijan, J.; Kulhanek, D.K.; Kogane, K. & Horiguchi, T., (2015). Re-discovery of a “living fossil” coccolithophore from the coastal waters of Japan and Croatia. Marine Micropaleontology, 116(1): 28-37.

Jiang, S.; Bralower, T.J.; Patzkowsky, M.E.; Kump, L.R. & Schueth, J.D., (2010). Geographic controls on nannoplankton extinction across the Cretaceous/Palaeogene boundary. Nature Geoscience, 3(4).

MacLeod, N. & others, (1997). The Cretaceous-Tertiary biotic transition. Journal of the Geological Society of London, 1254(265-293).

Mai, H.; von Salis, K.; Willems, H. & Romein, A.J.T., (1997). Fossil coccospheres from the K/T boundary section from Geulhemmerberg, The Netherlands. Micropaleontology, 43(281-302).

Medlin, L.K.; Sáez, A.G. & Young, J.R., (2008). A molecular clock for coccolithophores and implications for selectivity of phytoplankton extinctions across the K/T boundary. Marine Micropaleontology, 67(1-2): 69-86.

Pospichal, J.J., (1996). Calcareous nannoplankton mass extinction at the Cretaceous/Tertiary boundary: An update, in Ryder, G., et al., eds., The Cretaceous-Tertiary event and other catastrophes in Earth history. Geological Society of America Special Paper, 307: 335-360.

Schulte, P. & others, (2010). The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary. Science, 327: 1214-1218.

Young, J.R. & Bown, P.R., (1997). Cenozoic calcareous nannoplankton classification. Journal of Nannoplankton Research, 19(1): 36-47.


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Mesozoic Survivors compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 23-10-2017

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