Everticyclammina praekelleri Banner & Highton, 1990

Pleş, George, Bucur, Ioan I. & Păcurariu, Adriana, 2015, Foraminiferal Assemblages And Facies Associations In The Upper Jurassic Carbonates From Ardeu Unit (Metaliferi Mountains, Romania), Acta Palaeontologica Romaniae 11 (2), pp. 43-57 : 46-47

Everticyclammina praekelleri Banner & Highton, 1990 ( Fig. 3 f-h)

1990 – Everticyclammina praekelleri – Banner & Highton, p. 8, 10; pl. 1, fig. 1; pl. 3, fig. 5; pl. 4, figs. 1- 11.

2007 – Everticyclammina praekelleri – Krajewski & Olszewska, p. 299, fig. 5, C-D.

2008 – Everticyclammina praekelleri – Olszewska et al., fig. 8, K.

Description: The test is planspirally enrolled, involute and may develop trends to terminal rectilinearity. Wall is agglutinated, alveolar. The alveolar hypodermis is coated by a thin imperforate layer (epidermis) which seals the alveoli. The septa are slightly curved and non-alveolar with a thickness comparable to that of the chamber walls. Chambers are not flattened and irregular in shape and size. The last whorl is characterized by the development of coarse alveoli in the hypodermis. The aperture is single, terminal (“ammobaculitid”- type). In the posterior-lateral area of the hypodermis the alveoli are enlarged, elongated and closely spaced. Depending on the sectioning type they can appear ramified, fused together or subpolygonal. In the anterior-peripheral area, the alveoli are widely spaced given rise to a certain irregularity of the hypodermis. Dimensions: diameter of the enroled part of the test – 0.83 – 1.53 mm; lenght of the test – 1.59 – 1.86 mm; width – 0.51 – 0.71 mm.

Remarks: The main differences between Everticyclammina praekelleri and other representatives of the genus Everticyclammina , are associated with the development of alveolar structures. Many E. praekelleri specimens from our samples allowed observation of its inner structure, especially of the hypodermical layer. Elongated broadened alveoli are clearly noticed in the posterior-lateral parts of the hypodermis ( Fig. 3 f-h - arrows). Also, the anterior-peripherial alveoli are irregularly dispersed in most of the cases ( Fig. 3 f-h). The presence of an apparently multiple aperture in the E.

praekelleri specimen illustrated in Fig. 3g , can be explained by the sectioning model. A closer look to several key studies ( Hottinger, 1967; Loeblich & Tappan, 1988; Banner & Whittaker, 1991) points out the fact that multiple or cribrate types of aperture do not define any species of the genus Everticyclammina . All of these, together with other morphological features (the unflattened shape of the chambers or the reduction of chambers per whorl), represent key arguments in distinguishing E. praekelleri from Everticyclammina virguliana (Koechlin) , the oldest species of the genus. Moreover, E. virguliana possess a distinctive row of subcircular hypodermal alveolar spaces in the posterior-lateral part of the chambers wall. The relatively close resemblance of E. praekelleri with its descendent Everticyclammina kelleri (Henson) , can be excluded based on several traits. As opposed to E. kelleri , E. praekelleri has a much wider aperture, less structured wall, enlarged elongated lateral alveoli and a different stratigraphic position. More detailed arguments regarding this topic or the phylogeny of Everticyclammina can be found in the works of Redmond (1964) and Banner & Highton (1990).

Stratigraphic range: According to Banner & Highton (1990) and Banner & Whittaker (1991), the stratigraphic range of Everticyclammina praekelleri is restricted to the upper part of the Jurassic (Kimmeridgian-Tithonian). In the European Tethyan realm, the species was recorded in very few carbonate deposits, such as: the Tithonian of Crimeea Mountains, Ukraine ( Krajewski & Olszewska, 2007), the Tithonian Cieszyn Beds from Polish Western Carpathians ( Olszewska et al., 2008) or the Kimmeridgian lagoonal limestones of Paris Basin ( Lefort et al., 2012). It is worth mentioning that the presence of E. praekelleri in the Ardeu Unit limestones, represents the first report of this species from Romania. Taking into account these arguments, we consider that E. praekelleri represents a typical Upper Jurassic taxon with a stratigraphic position ranging from early Kimmeridgian up to late Tithonian.

Figures

Fig. 3 Upper Jurassic foraminifers from the Ardeu Unit. a-c Bramkampella arabica Redmond (a - Sample 65, b - Sample 172, c - Sample 146). d Undetermined lituolid (Sample 41). e Kaminskia-type foraminifer with fine canaliculated wall (Sample 66). f-h Everticyclammina praekelleri Banner & Highton (Sample 65). i Alveosepta jaccardi (Schrodt) (Sample 49). j-l Ammobaculites sp. (j - Sample 65, k - Sample 110, l - Sample 95). m-n Charentia evoluta (Gorbachik) (m - Sample 32, n - Sample 45). o-p Protopeneroplis striata Weynschenk (o - Sample 153, p - Sample 212).