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Abathomphalus mayaroensis


Classification: pf_mesozoic -> Globotruncanidae -> Abathomphalus -> Abathomphalus mayaroensis
Sister taxa: A. intermedius, A. mayaroensis,

Taxonomy

Citation: Abathomphalus mayaroensis (Bolli, 1951)
Rank: Species
Basionym: Globotruncana mayaroensis
Synonyms: Globotruncana (Globotruncana) planata
Taxonomic discussion: Generally, forms that are smaller than 0.5 mm have an umbilical system composed of portici coalescing to a variable extent rather than tegilla. [copied from Chronos database]
Similar species: Differs from A. intermedius in the presence of 2 keels on all chambers and flatter spiral side. [copied from Chronos database]

Type images:

Original description: Globotruncana mayaroensis Bolli 1951: The test has a lobate periphery and is flat or slightly convex on the dorsal side. The last chambers in many cases become slightly inflated dorsally, giving to the upper side of the test a somewhat uneven appearance. The side wall, which is limited by the marginal dorsal and ventral keels, also, in some specimens, appears slightly convex in the last chambers. The ventral side of the test is concave, but the last chambers are, as on the dorsal side, in many specimens more or less inflated. Chambers of the last whorl do not always follow one another uniformly, some being arranged more or less obliquely with respect to one another. The suture lines on the dorsal side are strongly curved, the initial parts clearly beaded and later very strongly developed. They are radial on the ventral side. The last whorl is usually formed by five chambers, but four are also common. Six chambers have been noted only in one specimen. The preservation of the specimens so far examined has not allowed detailed study of the aperture or apertures, which probably open into the umbilicus. A coverplate over the umbilicus with several apertures seems to be present, however, in some of the better preserved specimens.

Entries in the Catalog of original descriptions: Globotruncana (Globotruncana) planata;
Globotruncana mayaroensis;

Geological Range:
Last occurrence (top): at top of P. hariaensis zone (100% up, 66.4Ma, in Maastrichtian stage). Data source: zonal marker (from Timescale Creator)
First occurrence (base): within A. mayaroensis zone (67.30-69.18Ma, base in Maastrichtian stage). Data source: [copied from Chronos database]

Plot of occurrence data:

NB Plotting of Neptune data has been disabled on the Mesozoic pages because the dataset is both small and badly affected by a few sites with erroneous age models (our obs Huber, Petrizzo, Young, Nov 2016). The data can still be viewed via the range plottertool - tools menu.

Character matrix

test outline:Subcircularcoiling axis:Lowchamber arrangement:Trochospiralumbilicus:Narrow
edge view:Planoconvexumbilical or test sutures:Moderately depressedspiral sutures:Raised beadedshell porosity:Finely Perforate: 1-2.5
wall texture:Smoothaperture:Umb.-extraumbilicalaperture border:Tegillaaccessory apertures:None
periphery:Double keelumb chamber shape:Inflatedsp chbr shape:Inflatedperiph margin shape:Subangular
umb depth:Shallowdiameter mm:0.4 to 0.8width mm:breadth mm:0.16 to 0.3
final-whorl chambers:4.0-5.0

References:

Bolli, H.M., (1951). The genus Globotruncana in Trinidad. Journal of Paleontology, 25(2): 187-199.


Abathomphalus mayaroensis compiled by the pforams@mikrotax project team viewed: 29-5-2017

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