CATALOG OF ORIGINAL DESCRIPTIONS: Sigmoilopsis Finlay, 1947
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Original Description The genotype of Sigmoilina Schlumberger, 1887, is Planispirina sigmoidea Brady, which is a smooth, entirely calcareous shell with no apertural tooth, but a transverse plate of the style seen in Miliolinena, Biloculinella, and Nummoloculina. A large group of species, including schlumbergeri, celata Costa, orinocoensis Hedb., chapmani Cush., tenuis Czj., asperula Karr., miocenica Cush., tchokrakensis Gherke, formosana Nak., arenaria Brady, arenata Cush., latissima Chap., and flinti Cush. possess in common a calcareous basic test more or less heavily crusted with sand grains, and a round-rimmed aperture at the end of a Spiroloculine neck, with a distinct and often strong tooth at the end of an internal ridge. This is too compact and distinct a group to ally with sigmoidea merely because of a common sigmoid habit of growth. Some of the tenuis forms spread flatly on each side like Massilina or Spirosigmoilina Parr (1942, Mining and Geol. Jour., vol. 2, p. 361, for the Australian Balcombian tateana Howchin). But both these genera are entirely calcareous, and the latter has a cribrate aperture; it is available for the Massiline many-chambered species of Hauerina, such as desertorum Schw., fragilissima Brady, and speciosa Karr. It is possible that Praemassilina Lacroix, 1938 (described as an arenaceous coated Massilina), could be used for the Massiline forms of Sigmoilopsis such as oligocenica Cush., tenuis Czj., asperula Karr., miocenica Cush., tchokrakensis Gherke, foliacea Schw., and arenaria Brady, but the actual genotype (Massilina rugosa Sideb.) does not resemble them much, and until this is investigated they may all be referred to Sigmoilopsis. The status of Massilina alveoliniformis Millett is doubtful; from some of the figures it looks like an extreme form of the tenuis group, with the same aperture, but specimens I have from Mauritius show a cribrate aperture and indicate development from Schlumbergerina. Family Miliolidae. Extra details from original publication Type species, as interpreted and figured by Cushman (1946, Contr. Cushman Lab. Foram. Res., vol. 22, p. 36, pl. 6, figs. 1-4) and Brady (1884, Chall. Rept., vol. 9, pl. 8, figs. 1-2, 4 [Planispirina celata (Costa), partim]).
The nomenclatural status of this genus is questionable, because of the somewhat ambiguous designation of the genotype; it is not entirely clear whether Finlay intended to designate the species Sigmoidina schlumbergeri Silvestri, or only those specimens illustrated by Cushman and by Brady to which he refers.
References:
Finlay, H. J. (1947). New Zealand Foraminifera; Key species in stratigraphy – No. 5. New Zealand Journal of Science and Technology. 28(5 (sec B)): 259-292. gs
Sigmoilopsis compiled by the bforams@mikrotax project teamviewed: 18-6-2026
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