Didymocyrtis penultima


Classification: rads_cenozoic -> Coccodiscidae -> Didymocyrtis -> Didymocyrtis penultima
Sister taxa: D. antepenultima, D. avita, D. bassanii, D. didymus, D. laticonus, D. mammifera, D. penultima, D. prismatica, D. tetrathalamus, D. tubaria, D. violina, D. sp.

Taxonomy

Citation: Didymocyrtis penultima (Riedel) Sanfilippo and Riedel 1980
Rank: species
Basionym: Panarium penultima
Taxonomic discussion: (Riedel)1957 p.76 pl.1 fig.1 as Panarium; Sanfilippo&Riedel 1980 p.1010;Sanfilip; Alexandrovich 1989 (ODP 111 SR) p.255 pl.4 fig.3 (synonymy)

Catalog entries: Panarium penultimum

Original description: Cortical twin-shell shell constricted equatorially, with circular to irregularly rounded pores: its surface hearing prominent, obtuse protuberances. Distal chambers hemispherical, as caps on either end of cortical twin-shell, their length usually 0.2-0.3 that of twin-shell, somewhat narrower than twin-shell. Each cap surmounted by a spongy tube or tongue-shaped column, of which the width is approximately half that of the maximum breadth of twin-shell, or less. Outer medullary shell lenticular, inner one spherical.

Length of cortical twin-shell usually 100-12µm, its maximum breadth 80-105µm. Length of polar caps 25 - 40µm, of spongy polar columns 25-25-80µm. Distinguishing characters (rw): This species differs from other described members of the genus in the heavy protuberances of the cortical twin-shell. The polar terminations of the species here described are spongy columns rather than "hollow fenestrated tubes", but it seems undesirable to erect a separate genus based on this character. The definition of the genus Panarium should therefore be somewhat broadened to include forms in which the polar columns are spongy, and not hollow. Phylogeny (rw): There are indications that it was developed from a form having less conspicuous polar caps, and wider terminal spongy columns.

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

Geological Range:
Last occurrence (top): within Neogene Period (2.59-23.03Ma, top in Piacenzian stage). Data source: Lazarus et al. 2015 - "N age group"
First occurrence (base): within Neogene Period (2.59-23.03Ma, base in Aquitanian stage). Data source: Lazarus et al. 2015 - "N age group"

Plot of occurrence data:

References:

Alexandrovich, J. M. (1989). Radiolarian biostratigraphy of ODP Leg 111, Site 677, eastern equatorial Pacific, late Miocene through Pleistocene. Proceedings of the Ocean Drilling Program, Scientific Results. 111: 245-262. gs V O

Riedel, W. R. (1957b). Radiolaria: a preliminary stratigraphy. Reports of the Swedish Deep-Sea Expedition, 1947-1948. 6(3): 59-96. gs

Sanfilippo, A. & Riedel, W. R. (1980). A revised generic and suprageneric classification of the Artiscins (Radiolaria). Journal of Paleontology. 54(5): 1008-1011. gs


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Didymocyrtis penultima compiled by the radiolaria@mikrotax project team viewed: 25-11-2020

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