Reissella ramonensis Hamaoui, 1963

SIMMONS, MICHAEL & BIDGOOD, MICHAEL, 2023, “ Larger ” Benthic Foraminifera Of The Cenomanian. A Review Of The Identity And The Stratigraphic And Palaeogeographic Distribution Of Non-Fusiform Planispiral (Or Near-Planispiral) Forms, Acta Palaeontologica Romaniae 19 (2), pp. 39-169 : 88-90

Reissella ramonensis Hamaoui, 1963

Reference Illustration & Description

Hamaoui (1963), p. 62-64, pl. 1 (1-13), fig. 1.

This is a small but internally complex species with a taxonomically uncertain status. It is planispiral becoming flaring (to “peneropliform”), with chambers incompletely divided internally by (1) primary and (2) secondary “vertical subepidermal partitions” and (3) “horizontal partitions” (respectively (1) “beams”, (2) “intercalary beams” and (3) “rafters” sensu Loeblich & Tappan 1985 and Hottinger 2006) which continue between septa. These form an internal mesh described by Hamaoui, 1963, as a “regular, pigeon-hole (honey-comb) pattern”, apparently following the terminology used by Henson (1948).

The main aperture in Reissella is basal in the apertural face in earlier chambers and progresses to the middle of the face in later chambers where it is projected on a short neck. It is surrounded by numerous, smaller, supplementary apertures. See the Species Key Chart (Appendix) for diagnostic and other characteristics.

A “subepidermal pigeon- hole” pattern is now referred to as a “polygonal subepidermal network” and is a feature not observed in living foraminifera ( Hottinger 2006). Hottinger goes on to state that…

“ The extremely thin, often transparent epiderm in agglutinated foraminifera suggests, that the polygonal network is a device to keep symbionts exposed to light and in the immediate vicinity of the location where gas exchange through the shell should be enhanced by particular, porous textures.”

This may be the case for larger agglutinated foraminifera such as the orbitolinids. However, the small overall size of this species (<1mm) suggests that these are perhaps not cells for photosymbionts in which case their exact function is unknown. The primary partitions do not reach the middle of the chamber and the secondary and horizontal partitions are even more limited to the marginal area.

Although regarded as agglutinated and classified accordingly ( Loeblich & Tappan 1988, Mikhalevich 2004b; Kaminski, 2004, 2014) there remains questions about the exact nature of the wall of Reissella and that it may have “possibly” originally been porcelaneous ( Hamaoui, 1963). This would place Reissella in the Soritids (i.e., “probably the Peneroplidae ” according to Hamaoui 1963). However, Hamaoui (1963) also states that the main areal aperture surrounded by supplementary apertures, and the presence of secondary radial subepidermal horizontal partitions (which are parallel to the septa) would be considered unusual features for a Peneropolid and was more typically “lituolid” following the concept of the latter by Smout (1963). Nevertheless, examination of the type illustrations in Hamaoui (1963) cannot remove a suspicion that Reissella is a soritid although its general similarity with the soritid Pseudorhipidionina casertana (see below) is perhaps superficial. The higher taxonomic classification of this taxon (Family level and above) remains an enigma.

De Castro (1981) and De Castro in Schroeder & Neumann (1985) remarked on the similarity between P. casertana and R. ramonensis with the former lacking the ‘rafters’ element of the polygonal subepidermal network. P. casertana also appears to have a greater tendency to fully uncoil compared with R. ramonensis . However, P. casertana and R. ramonensis are also remarked upon regarding their similarities in stratigraphic and ecological distribution ( De Castro, 1981).

In the original description ( Hamaoui 1963) no thin-section examples are shown with only light-microscope photographs and schematic drawings provided. The form illustrated in thin-section as R. ramonensis by Hamaoui & Saint-Marc (1970: pl. 40, fig. 8) from the late Cenomanian of Lebanon strangely does not appear to conform to the concept of the original description and lacks the “peneropolid- like” appearance. It appears to tend towards the concept of P. casertana . In other illustrations by Hamaoui (1966), De Castro (1981) notes that one illustration (pl. 3, fig. 6) looks very similar to P. casertana .

In summary, considering morphological, stratigraphic and ecological similarities, the taxonomic relationship between Reissella ramonensis Hamaoui (1963) and Pseudorhipidionina casertana ( De Castro 1965) may be synonymous in which case the former name would take priority. However, there are subtle differences although such differences may not be easy to determine except in good quality thin-section examples. The two taxa may be micro- and macro-spheric forms of the same species. On the other hand, the differences in wall composition (if confirmed and maintained) indicates clear taxonomic separation with R. ramonensis being the agglutinated isomorph of P. casertana (the position tentatively adopted here).

Stratigraphic Distribution

Late Cenomanian.

Hamaoui’s original description from Israel ( Hamaoui 1963) indicates his specimens were recorded from unnamed clays of the Judea Limestone Group, dated as late Cenomanian based on associated microfaunas. Arkin and Hamaoui (1967) confirmed an approximate late Cenomanian age.

It was subsequently reported (though poorly illustrated) by Hamaoui (1965) from the Hazera Formation of Israel. Lipson-Benitah (2009) reported this as “in association with” the planktonic foraminifera Helvetoglobotruncana helvetica (Bolli) which – she stated – therefore conferred a middle Turonian youngest age for R. ramonensis . However, the only occurrences of R. ramonensis positively identified by Hamaoui were recorded below the lowest occurrence of H. helvetica . It is also possible that Hamaoui (1965) was using an outdated concept of H. helvetica and may have in fact recorded H. praehelvetica which ranges down into the late Cenomanian.

“ Reissella sp ” was described from the Albian of Turkey by Solak et al. (2021). This might be ancestral to R. ramonensis or the Pseudorhipidionina group.

Cenomanian Paleogeographic Distribution

Central Neotethys.

Limited distribution, confirmed by illustration from Israel and unconfirmed from undifferentiated Cenomanian – Turonian strata of Crete by Leppig (1976).