Heterostegina sp.

Torres-Silva, Ana. I., Eder, Wolfgang, Hohenegger, Johann & Briguglio, Antonino, 2018, Morphometric analysis of Eocene nummulitids in western and central Cuba: taxonomy, biostratigraphy and evolutionary trends, Journal of Systematic Palaeontology 17 (7), pp. 557-595 : 587-588

Heterostegina sp. indet.

( Fig. 18I )

2017 Heterostegina sp. indet. Torres-Silva, Hohenegger, Cori ́́c, Briguglio, & Eder: 57, fig. 10F.

Material. Three megalospheric specimens in equatorial section from Loma Candelaria (98LC-1).

Description. This species is known only from its internal equatorial morphology. Test diameter ranges from 3.1 to 3.5 mm. The embryonic apparatus is characterized by a large and subspherical proloculus between 0.2 and 0.25 mm wide. It is followed by a second chamber of similar in size and form, and by a spiral with a weaker marginal radius increase. It produces many whorls, with shorter chambers; hence, it shows a decrease in the number of chamberlets in comparison to H. cubana and H. ocalana . Primary septa have a weaker backbend angle in the first few whorls, hence forming straighter chambers. In later whorls, the chambers became more arched. After the embryonic stage, two undivided chambers are followed by chambers that are subdivided into sub-rectangular to hexagonal chamberlets, divided by complete septula. The first chamberlet nearest to the marginal spiral is 2–3 times longer than the others. The number of chamberlets and septula increases during ontogeny.

Remarks. This seems to be a new species because it is significantly distinct from H. ocalana and H. cubana in its marginal radius increase and the size and form of the embryonic apparatus. The latter is the most important character for species delimitation, especially in larger benthic foraminifera. Due to missing axial sections, the possibility that this new species might actually be Spiroclypeus cannot be rejected.

Occurrences. Late middle Eocene to late Eocene, NP 16/17, Loma Candela.

Figures

Figure 18. A, B, D–H, Heterostegina ocalana Cushman; A, Loma Viǵıa, CA-216-D1a; B, Norona, NOR-UN 15/14; D, Loma Viǵıa, CA-216-79; E, F, Loma Jabaco; E, LM-52-756; F, LM-52-752; G, H, Norona, NOR-UN 24. C, Heterostegina cubana Cizancourt, Loma candelaria, 98LC-1H-809. I, Heterostegina sp. indet., Loma Candelaria, 98LC-1H-808. A, B, A forms in axial section; C–G, I, A forms in equatorial section; H, external view.