Distinguishing features: Parent taxon (Nannoliths inc sedis): Nannofossils not obviously homologous with heterococcoliths, holococcoliths, or braarudosphaeralids This taxon: Hemispherical to tall cylindrical nannoliths, with narrow walls constructed from one to several cycles of thin elements, enclosing a hollow central space; the nannolith tapers distally, and may have apical spines or processes.
Daughter taxa (time control age-window is: 0-800Ma)
Granddaughter taxa
Lapideacassis Large hemispherical to tall cylindrical nannoliths with narrow walls constructed from one to several cycles of thin elements, enclosing a hollow central space; the nannolith tapers distally, and may have apical spines or processes. Protruding ledges often mark the junction of different cycles in the wall.
Distinguishing features: Parent taxon (Nannoliths inc sedis): Nannofossils not obviously homologous with heterococcoliths, holococcoliths, or braarudosphaeralids This taxon: Hemispherical to tall cylindrical nannoliths, with narrow walls constructed from one to several cycles of thin elements, enclosing a hollow central space; the nannolith tapers distally, and may have apical spines or processes.
Morphology: Rare and sporadic stratigraphical distribution, but a K/T boundary survivor.
Crystallographic orientations: The entire nannolith is formed of R-units, in side view the c-axes are inclined upward slightly (so with gypsum plate when vertical the left hand side is blue and the right hand side yellow). In apical view the c-axes are slightly oblique from radial. [JRY 2017 my obs, and interpretation of published micrographs]
Phylogenetic relationsForchheimer & Stradner (1973) suggested L. cornuta might be a holococcolith based on TEM images of their paratype specimen which showed a rhombohedral ultrastructure. However, this has not been supported by any other observations and they show much better developed cycles of plates than s normal in holococcoliths. Re-examination of their micrographs shows that the rhombohedra are more variable in size than is normal in holococcoliths, so they may be a diagenetic fabric [my interpretation - JRY 2015]. So, they appear more likely to be heterococcoliths.
The group does not seem to have ben affected by the K/Pg extinctions, with most species also occurring the Paleogene.
The morphological data given here can be used on the advanced search page. See also these notes
Geological Range: Notes: The groups is always rare. Last occurrence (top): at top of Eocene Epoch (100% up, 33.9Ma, in Priabonian stage). Data source: Total of ranges of the species in this database First occurrence (base): within Early Aptian Substage (118.70-121.40Ma, base in Aptian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: this is a higher taxon page so Neptune data is not plotted. For the customisable plot option go to a genus page Parent: Nannoliths inc sedis
References:
Black, M. (1971b). Problematical Microfossils from the Gault Clay. Geological Magazine. 108(4): 325-327. gs
Bown, P. R. & Young, J. R. (1997). Mesozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 21-36. gs
Forchheimer, S. & Stradner, H. (1973). Scampanella, eine neue Gattung kretazischer Nannofossilien. Verhandlungen der Geologischen Bundesanstalt (Wien). 1973(2): 286-289. gs
Lapideacassaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 14-12-2024
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