The foraminiferal genera Pararotalia, Neorotalia, and Calcarina: taxonomic revision

Abstract

Scanning electron microscopy of the architecture of Rotalina inermis Terquem, 1882, the type-species of the genus Pararotalia Le Calvez, 1949, and of Rotalia mexicana Nuttall, 1928, the type-species of the genus Neorotalia Bermudez, 1952, reveals that both taxa have in common: 1) an umbilical bowl closed by either a single or a compound umbilical plug; 2) an interiomarginal extraumbilical aperture, restricted by a toothplate that protrudes with a free edge into the aperture and forms an umbilical spiral canal; and 3) a septal flap and intraseptal interlocular spaces. Rotalia mexicana, however, also possesses an enveloping canal-system, similar to that found in the Calcarinidae. For this reason Neorotalia must be regarded as a valid distinct genus, not synonymous with Pararotalia, as proposed by some authors. Calcarina calcar d'Orbigny, 1839, variously placed by authors in Rotalia Lamarck, 1804, in Pararotalia Le Calvez, 1949, and lately again in Calcarina d'Orbigny, 1826, is shown to possess the same basic architecture as Neorotalia and is placed, consequently, into this latter genus. Irregular supplementary apertures occurring in N. calcar are not considered of generic value and neither are they regarded as indicating a relationship with Nautilus spengleri Gmelin, 1788, the type-species of Calcarina. The latter, although characterized by a complex enveloping canal-system, possesses primary multiple interioareal main apertures, surrounded by thick rims, as well as a small umbilical plate, but lacks a toothplate with a free edge. For comparison, Pararotalia spinigera (Le Calvez, 1949) and Neorotalia viennoti (Greig, 1935) were also studied. The subfamily Pararotaliinae Reiss, 1963, is emended to include the canal-system as a characteristic feature. A glossary of selected terms is appended.

Larger Foraminifera From the Upper Oligocene of the Venetian Area, North‐east Italy

“…Remarks. Neorotalia and Pararotalia Le Calvez, 1949, although closely related and considered to be synonyms by Loeblich and Tappan (1987), were separated again by Hottinger et al . (1991): Pararotalia has an open spiral umbilical furrow, whereas in Neorotalia , this furrow is closed by a cover extending the ventral, adaxial chamber wall to the heavy ornament filling the umbilicus.…”

Evolution and Geological Significance of Larger Benthic Foraminifera

“…However, the supplemental skeleton at the pellatispirid shell margin is not a marginal cord, as seen in nummulitids: it lacks the sulcus, and its canal system is radial and enveloping, not a tangential, polygonal network (Hottinger , 2001). The work of Hottinger et al (1991) clearly shows on the other hand, a close relationship between Pellatispira and Biplanispira, as emphasised by the adult of the former often forming the juvenile stage of the latter. He desribed the thickened shell margin produced by the marginal canal sytem in Pellatispira (Fig.…”

“…They describe the aperture as interiomarginal, extending obliquely into the apertural face, and the intercameral foramen as areal, due to the attachment of an imperforate tooth plate that extends to the distal margin of the aperture. Hottinger et al (1991) emended the description of the Pararotaliinae to include the canal system. It is also distinguished from van Gorsel (1975van Gorsel ( , 1978.…”

“…The trochospiral chambers of Pararotalia are arranged to expose the umbilical region that creates direct access to the ambient environment. The test possesses a spiral umbilical canal, formed by interconnected toothplates, with a free edge (Hottinger et al 1991). BouDagher-Fadel and Price (2014) suggested that the Nummulitidae may have evolved from a simple rotaliid test through forms which developed a moderately thick marginal cord and a rapidly widening coil leading to, in the Late Paleocene (P4a), the long-ranging completely planispiral evolute Operculina (see Fig.…”

Evolution and Geological Significance of Larger Benthic Foraminifera

“…Neorotalia (see Chapter 6) by the lack of the closed interlocular spaces ("enveloping canal system", Hottinger et al, 1991 fig. 13).…”