Calyculus


Classification: Mesozoic -> Podorhabdales -> Calyculaceae -> Calyculus
Sister taxa: Calyculus, Carinolithus,

Distinguishing features: High, broad, flaring distal-shield composed of radial, non-imbricating elements, and a proximal-shield which is often reduced to a simple, narrow cycle of elements; central-area structures are highly variable, including numerous bars, concentric structures, nets and grills.


Daughter taxa: (blue => in age window 0-300Ma)
Central area with lozenge & cross-bars (Calyculus)
Elliptical Calyculus ; rim moderately elevated; central area with axial cross,concentric lozenge.
Small elliptical Calyculus; rim low & narrow; central area with axial cross and concentric lozenge.
Central area with radial bars (Vikosphaera)
Calyculus with central area with around 14-20 lateral bars. Rim elevation very variable, even on a single coccosphere
Central area with lozenge, cross-bars & radial bars (Catillus)
Elliptical Calyculus ; rim low; central area with axial cross; concentric lozenge and short radial bars
Elliptical Calyculus; rim moderately elevated; central area with axial cross, small lozenge and long radial bars.
Central area with grill (Incerniculum)
Elliptical Calyculus; rim moderately elevated, narrow; central area with finely perforate net and spine-base
Elliptical Calyculus ;rim moderately elevated; central area with axial cross finely perforate net and large spine-base
Large, broadly elliptical Calyculus; rim elevated, broad; central area with grill
Specimens not identified to species level

Taxonomy:

Citation: Calyculus Noël, 1973
Rank: Genus
Type species: Calyculus cribrum Noël, 1973.
Synonyms: Proculithus Medd, 1979; Incerniculum Goy, 1979; Vikosphaera Goy, 1979; Catillus Goy, 1979.
NB The genera Incerniculum, Vikosphaera and Catillus were proposed based on variations in central area structure, Bown (1987) and Crux (1987) both argued that this was impractical and such characters were better used at specific level. Nonetheless, it is useful to sort the species out into the categories proposed by Goy in order to understand the taxonomy - this is what I have done in the table [JRY]

Farinacci & Howe catalog pages: Calyculus + * Catillus * Incerniculum * Proculithus * Vikosphaera *

Distinguishing features: High, broad, flaring distal-shield composed of radial, non-imbricating elements, and a proximal-shield which is often reduced to a simple, narrow cycle of elements; central-area structures are highly variable, including numerous bars, concentric structures, nets and grills.


Morphology remarks: Species are often difficult to differentiate in LM because the distinctive central area structures may be imperceptible or missing.

Geological Range:
Last occurrence (top): within Bajocian Stage (168.28-170.30Ma, top in Bajocian stage). Data source: Total of range of species in this database
First occurrence (base): within Pliensbachian Stage (182.70-190.82Ma, base in Pliensbachian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R. & Cooper, M.K.E., (1998). Jurassic. In: Bown, P.R. (Editor), Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. Chapman & Hall, pp. 34-85.

Bown, P.R., (1987). Taxonomy, evolution, and biostratigraphy of Late Triassic-Early Jurassic calcareous nannofossils. Special Papers in Palaeontology, 38: 118 p.

Crux, J.A., (1987). Concerning dimorphism in Early Jurassic coccoliths and the origin of the genus Discorhabdus Noël 1965. Abhandlung der Geologischen Bundesanstalt, 39: 51-55.

Goy, G.; Noël, D. & Busson, G., (1979). Les conditions de sédimentation des schistes-carton (Toarcien inf.) du bassin de Paris déduites de l'étude des nannofossiles calcaires et des diagraphies. Documents de Géologie de la Faculté des Sciences de Lyon, 75: 33-57.

Medd, A.W., (1979). The Upper Jurassic coccoliths from the Haddenham and Gamlingay boreholes (Cambridgeshire, England). Eclogae Geologicae Helvetiae, 72: 19-109.

Noël, D., (1973). Nannofossiles calcaires de sédiments jurassiques finement laminés. Bulletin du Muséum National d'Histoire Naturelle, 3e serie, 75: 95-156.


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Calyculus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-7-2018

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