Gartnerago


Classification: Mesozoic -> Arkhangelskiales -> Kamptneriaceae -> Gartnerago
Sister taxa: Crucicribrum, Gartnerago, Kamptnerius, Senilatus,

Distinguishing features: Tiered coccoliths with distinctive LM images consisting of a narrow to moderately-broad rim with a narrow, dark outer-cycle; a diagnostic, bright median-cycle; and a dark, inner-cycle. Central-area structures variable but generally dark in LM.


Daughter taxa: (blue => in age window 0-800Ma) Granddaughter taxa
Species with plate in central area
Gartnerago with a narrow rim and a broad central area, filled with a plate pierced by numerous pores (~>10 in each quadrant); the plate is crossed by sutures, the transverse of which is slightly oblique.

Similar to G. obliquum but rim broader, central area smaller.

Similar to G. obliquum but pores larger and with cross-bars within them

Gartnerago with protruding axial bars; perforations small, with a double row of perforations on each side of the cross-bars, with others randomly distributed

Small to large coccoliths characterized under LM XPL by a conspicuous, narrow, bright rim cycle and wide central area spanned by a plate. The plate is usually crossed by four radial extinction lines (two in the major axes of the coccolith ellipse and two diagonally orientated) and narrow, bright, bar-like structures, which are longitudinal and near transverse (rotated by ~10°), and birefringent when the coccolith is at 45° to the polarizing directions.

Four equal size plates in the central area separated by axial sutures, no axial cross

Species with cross in centre
Gartnerago with diagonal cross bars.



Gartnerago with wide central area spanned by broad axial cross bars that have arrowhead-shaped ends and median suture lines.

Species with transverse bar
Central area, wide, open and spanned by a complex transverse bar, which bifurcates where it joins the rim.

Medium-sized Gartnerago with a loxolith-type rim and a narrow, perforate central area plate, which has differentiated axial bars, although the longitudinal bar may be subordinate or poorly defined.

Small- to medium-sized (usually <7.0 µm) Gartnerago species with an open central area spanned by a transverse, conjunct bar.

Gartnerago with a wide central area spanned by a narrow transverse bar which delimits two, large D-shaped openings; a finely perforate proximal net is seen in good preservation (Black, 1975, Pl. 34, figs 6-8).

Specimens not identified to species level

Taxonomy:

Citation: Gartnerago Bukry, 1969
Rank: Genus
Type species: Arkhangelskiella concava Gartner, 1968; this is almost certainly a junior synonym of Gartnerago segmentatum (Stover, 1966), which therefore, by priority, becomes the type species.
Synonyms: Cribricatillus Black, 1973; Laffittius Noël, 1969

Farinacci & Howe catalog pages: Gartnerago * , Cribricatillus * , Laffittius *

Distinguishing features: Tiered coccoliths with distinctive LM images consisting of a narrow to moderately-broad rim with a narrow, dark outer-cycle; a diagnostic, bright median-cycle; and a dark, inner-cycle. Central-area structures variable but generally dark in LM.


Morphology remarks: Central-area structures include transverse bars, axial or diagonal cross bars (proximally-situated fine nets may be seen when preservation is good), or plates that are usually perforate, with axial or near axial sutures.

Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Maastrichtian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Aptian Stage (25% up, 123Ma, in Aptian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Black, M. (1973). British Lower Cretaceous Coccoliths. I-Gault Clay (Part 2). Palaeontographical Society Monograph. 127: 49-112. gs

Bukry, D. (1969). Upper Cretaceous coccoliths from Texas and Europe. The University of Kansas Paleontological Contributions. Article 51 (Protista 2): 1-79. gs

Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 132-199. gs

Gartner, S. (1968). Coccoliths and related calcareous nannofossils from Upper Cretaceous deposits of Texas and Arkansas. The University of Kansas Paleontological Contributions. Article 48 (Protista 1): 1-56. gs

Noël, D. (1969). Arkhangelskiella (coccolithes Crétacés) et formes affines du Bassin de Paris. Revue de Micropaléontologie. 11: 191-204. gs

Stover, L. E. (1966). Cretaceous coccoliths and associated nannofossils from France and the Netherlands. Micropaleontology. 12: 133-167. gs


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Gartnerago compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 18-9-2019

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