Operculinoides floridensis ( Heilprin, 1885 )

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 : 583-584

Operculinoides floridensis ( Heilprin, 1885)

( Fig. 16A–H )

1885 Nummulites floridensis Heilprin : 321.

1941 Operculinoides floridensis (Heilprin) ; Cole: 20, pl. 9, fig. 8, pl. 10, figs 1–3.

1941 Operculinoides willcoxi (Heilprin) ; Cole: 32, pl.9, figs 2, 3.

1958 Operculinoides floridensis (Heilprin) ; Cole: pl. 33, fig. 2.

1974 Nummulites (Operculina) floridensis Heilprin ; Frost & Langenheim: 77, pl. 12, figs 1–9.

1981 Nummulites floridensis Heilprin ; Butterlin: 31, pl. 10, figs 3, 4.

1993 Palaeonummulites floridensis (Heilprin) ; Robinson & Wright: 333, pl. 30, figs 1–3.

Material. Twenty-seven megalospheric specimens in equatorial section, comprising 19 from Loma Candelaria (98LC-1), three from Loma El Santo (CA-215), four from Loma Viǵıa (CA-216) and one from Loma Jabaco (LM-52).

Description.

External features. The planispiral test varies from flattened to robust forms. Flattened forms are laterally compressed and fragile, with a prominent, sharply defined umbo due to a partially involute nepionic stage. Robust forms are more involute with a less inflated umbo. External surface smooth or marked by slightly raised septal sutures.

Internal features. Megalospheric generations in equatorial section are characterized by a small, spherical to subspherical proloculus with a mean diameter of 0.2 mm followed by a reniform deuteroloculus, then by a variably coiled spiral. The individuals with the highest rates of marginal radius increase (lax variants) have at the adult stage 2–3 rapidly enlarging whorls. Chambers are separated by operculine septa with pronounced septal undulations. Chamber height in the adult stage can be more than 10 times higher than chamber width. The other end of this range of morphological variability is typified by more inflated individuals with a weaker marginal radius increase, producing tightly coiled spirals in which the adult test involves 3–4 whorls. Chamber height is up to 4 times chamber length. Septal undulations are less pronounced.

Characters and attributes (means and standard deviations) for Operculinoides floridensis (tightly and loosely coiled) and comparisons with Nummulites striatoreticulatus , Palaeonummulites trinitatensis and Operculinoides soldadensis are given in Tables 7 and 8 .

Occurrences. Early middle Eocene, NP14/15, Penon Formation; late middle Eocene to late Eocene, NP16/17 upper part of Loma Candela Formation; late middle Eocene, CNE 13, Arroyo Blanco Formation; late Eocene, NP19-20/CP 15, Jabaco Formation; late Eocene, NP17/ 19, Blanco Formation.

Remarks. Operculinoides floridensis is one of the most widely recognized operculinoid species in the Caribbean province. It exhibits a wide range of variability in coiling, which overlaps with the characteristics of Operculinoides , Palaeonummulites and Operculina . The tightly to moderately coiled Cuban specimens are similar to those described by Frost & Langenheim (1974) from Chiapas. Abundant loosely coiled forms were found in localities with optimum conditions for lepidocyclinids and orthophragminids in contrast to localities with Nummulites striatoreticulatus . Intra-population morphological diversity is greatest for O. floridensis at Loma Candelaria (98LC-2) where tightly to moderately loosely coiled forms occur.

Stratigraphical and geographical distribution. Middle Eocene to late Eocene (Lutetian to Priabonian) Cuba, US Gulf Coast, Peru, Curacao, Mexico, Ecuador, Panaḿa, St. Bartheleḿey, Trinidad, Jamaica, Costa Rica, Brazil.

Figures

Figure 16. Operculinoides floridensis (Heilprin). A–C, Loma Candelaria; A, 98LC-1-651; B, 98LC-1-667; C, 98LC-1-815. D, E, Loma Viǵıa; D, CA-216-F3-16; E, CA-216-D1a. F, Loma El Santo, CA-215-852. G, Loma Jabaco, LM-52-759. H, Angelita Quarry, 98MT-1. A–D, F and G are A forms in equatorial section; E and F are A forms in axial section.