radiolaria - rads_cenozoic - Plectacantha oikiskos

Citation: Plectacantha oikiskos Jørgensen 1905

Synonyms:
1899 Peridium (?) intricatum - Cleve pl. 2, fig. 8
1900 Periplecta intricata - Jørgensen p. 73
1905 Plectacantha oikiskos - Jørgensen p. 131-132; pl. 13, figs. 50-58
1976 Plectacantha oikiskos - Bjørklund pl. 6, figs. 8-10
1998 Plectacantha oikiskos - Bjørklund et al. pl. 2, figs. 28-29
2003 Plectacantha oikiskos - Bjørklund and Kruglikova pl. 4, figs. 18-29
2003 Plectacantha oikiskos - Cortese et al. p. 69-70 (not figured)

From Suzuki Paleotax db:

1905 Plectacantha oikiskos n. sp. Jörgensen p. 131-132, pl. 13, figs. 50-57
1931 Plectacantha oikiskos Jorgensen (?) Bernstein p. 7-8, 22, pl. 2, figs. 5, 6
1932 Plectacantha oiskiskos Jorgensen Bernstein pl. 3, figs. 2, 3
1934 Plectacantha oikiskos Jorgensen Bernstein p. 17
1937 Plectacantha oikiskos Joergensen Wailes p. 12, fig. 23
1963 Plectacantha oikiskos Jorgensen Huelsemann p. 22
1971 Plectacantha oikiskos Jorgensen Petrushevskaya pl. 71, fig. 2
1976 Plectacantha oikiskos Jorgensen Bjørklund pl. 6, fig. 8-10
1979 Plectacantha oikiskos Jorgensen Kozlova & Petrushevskaya fig. 347
1983 Plectacantha oikiskos Jorgensen Benson p. 506, pl. 7, figs. 13, 14
1989 Plectacantha oikiskos Jorgensen Kruglikova p. 472, pl. 19.2, fig. 1
2017 Plectacantha oikiskos Jörgensen Chen et al. p. 165, pl. 52, figs 17, 18 (only)
2017 Plectacantha oikiskos Jörgensen Chen et al. p. 165, pl. 52, figs 19-21

Original description: The primary verticil of branches of the apical spine has (generally?) only two branches, pointing upwards and outwards in the angle between the dorsal, basal spine and the lateral ones. These two branches together with the protruding middle stem form three undivided spikes, about equal in length. The left, lateral spine, Ll, has the primary verticil complete. Of these three branches, however, the inside one (lli in fig. V, p. 121) is - as previously mentioned - transformed into a short, strong arch, pointing downwards, at the end of which the left, lateral arch and. the primary, ventral one meet. The two other branches form with the protruding middle stem, three, diverging, long, single spikes, pointing obliquely outwards and to the sides. By these three long, protruding spikes, the left, lateral spine may always be easily recognized. The right, lateral spine has only retained one branch of the verticil in its original form, the other two being branches for the two corresponding, primary arches, one belonging to the ventral arch, the other to the right, lateral one. There are consequently here two long, simple spikes, about equal in length, the outer branch in the primary verticil and the protruding, middle stem. The dorsal, basal spine has only one simple branch of the verticil, pointing outwards and upwards (dd in fig. V, p. 124), the two others being strong, arched branches, diverging nearly at right angle on both sides. One of these branches forms the right, the other the left lateral arch. The middle stem of the basal spine is here branched, there being one or two similar, secondary arches outside the primary, lateral ones. The dorsal, basal spine, therefore, only shows one simple, protruding spike. A similar, smaller byspine is generally to be found farther out. The dorsal spine is the longest and strongest, the apical one is shortest and weakest.
Outside the primary meshes, secondary ones are developed more or less richly, varying considerably in size. These unite to form a ,,network” which is generally rather imperfect, but would seem, on older individuals, to be made more complete by the addition of connecting beams across the large, secondary meshes, so that these meshes finally are smaller in size and more in number. Generally speaking, the network is conically expanded downwards, and seems, in the case of older individuals, finally to be imperfectly closed beneath by the development of a few, fine, long, transverse beams. In the material examined specimens with such nearly closed network were always rare. Of the more important byspines and secondary meshes, I will only mention the following which seem always to be present, and may serve to help in identifying the species. Under the protruding right lateral spine a large, secondary, pentagonal mesh will be found. The left, lateral arch has a strong byspine in the middle,. pointing outwards and upwards, and under it, there is a large, secondary mesh. On both sides of the dorsal spine, outside the primary, lateral arches, on the left side will be found two secondary meshes, and on the right side one; the latter being the largest, but it is perhaps later on divided into two. Moreover, on all the stronger arches, there is a more or less. rich development of byspines, pointing outwards and upwards, some times twins, directed upwards-outwards and downwards-outwards. The beams are thin in young individuals, especially at the outer secondary meshes; they are much stronger on older individuals.

The length of the basal, dorsal spine is ± 55µm.
Not rare, but always in small number.
Remarks on original description: I considered this species first to belong to the genus Periplecta Haeckel; but as I later on found that what with Haeckel characterises this genus is also characteristic of all closely related genera, as I am acquainted with them from plankton samples (not drawings), I have been obliged to change the name of the genus.
I at first considered this species to be Cleve’s Peridium intricatum, and this may be correct, but it cannot be proved to be so from Cleve's illustration nor from his description. As it is, moreover, quite as probable that Cleve's Peridium (?) laxum also belongs to this species, I consider it best to retaiu the manuscript name I originally had given the species befom Cleve's work was published.

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

Geological Range:
Last occurrence (top): Extant. Data source: Lazarus et al. 2015 - "R age group"
First occurrence (base): within Quaternary Period (0.00-2.59Ma, base in Gelasian stage). Data source: Lazarus et al. 2015 - "R age group"

References:

Bjørklund, K. R. & Kruglikova, S. B. (2003). Polycystine radiolarians in surface sediments in the Arctic Ocean basins and marginal seas. Marine Micropaleontology. 49(3): 231-273. gs

Bjørklund, K. R. (1976). Radiolaria from the Norwegian Sea, Leg 38 of the Deep Sea Drilling Project. Initial Reports of the Deep Sea Drilling Project. 38: 1101-1168. gs

Bjørklund, K. R., Cortese, G., Swanberg, N. & Schrader, H. J. (1998). Radiolarian faunal provinces in surface sediments of the Greenland, Iceland and Norwegian (GIN) Seas. Marine Micropaleontology. 35(1-2): 105-140. gs

Cortese, G., Bjørklund, K. R. & Dolven, J. K. (2003). Polycystine radiolarians in the Greenland-Iceland-Norwegian Seas: species and assemblage distribution. Sarsia. 88(1): 65-88. gs

Jørgensen, E (1900). Protophyten und Protozoen im Plankton aus der norwegischen Westkuste. Bergens Museums Aarbog. 1899(6): 51-95. gs O

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 O

Missing or ambiguous references: Cleve 1899;

Plectacantha oikiskos

Taxonomy

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

References:

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