Amphimelissa


Classification: rads_cenozoic -> Cannobotryidae -> Botryocyrtidae -> Amphimelissa
Sister taxa: Acrobotrissa, Amphimelissa, Botryocampe, Botryocella, Botryocyrtis, Botryometra, Centrobotrys, Lithobotrys, Neobotrys
Daughter taxa (time control age-window is: 0-800Ma)
Amphimelissa setosa

neptune records: 3
Amphimelissa sp.

neptune records:

Taxonomy

Citation: Amphimelissa Jørgensen 1905
Rank: genus
Basionym: Amphimelissa

Catalog entries: Amphimelissa

Original description: This genus in outward appearance is similar to Lithomelissa, but its structure is principally different. It has the most important spines of the Campylacantha- type, namely the four primary spines, V, D, Lr and Ll, one ventral, sagittal spine, and two strong lateral, dorsal ones, rising from the base of the spine D, which here, as in Lithomelissa, appears as a protruding, apical spine. The primary arches too are strongly developed, the ventral arch, namely, as well as the right and left lateral arches (cfr. Plectacantha) all as arches inside the cephalis. To these come a couple of strong arches from the dorsal, lateral spines to the primary, lateral arches, also situated inside the cephalis, near its sides.

These strong inner arches are all connected outwards with the lattice shell, by means of strong, supporting beams which, for the most part, protrude on the exterior, as fine, long spikes.

This peculiar form is only distantly related to the others in my material. In structure it is unmistakably similar to Phormacantha hystrix: but there are, nevertheless, as far as I have hitherto been able to see, important differences in the structural type. The distinctly enclosed columella (the spine D) is characteristic; it shows, from the dorsal side, two basal, obliquely downwards pointing side branches, the dorsal, lateral spines, and higher up two obliquely upwards pointing ones, the usual primary branches of the spine D. Probably the two strong arches from the dorsal, lateral spines to the right and left, primary, lateral arches correspond to the comparatively strong apical arches, which in Phormacantha hystrix extend from the primary branches of the apical spine A to the lateral arches. In this case, the dorsal, lateral spines might be considered to be, centrally displaced, primary branches of the spine A, and this answers to their direction.

The genus Amphimelissa then has an inner, incompletely latticed cephalis, surrounded by a lattice shell, which immediately continues downwards as a thorax.

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at base of Gelasian Stage (0% up, 2.6Ma, in Gelasian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Jørgensen, E (1905). The protist plankton and diatoms in bottom samples: Radiolaria. In, Nordgaard (ed.) Hydrographical and biological investigation in Norwegian Fjord. 49-151. gs


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Amphimelissa compiled by the radiolaria@mikrotax project team viewed: 21-4-2021

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