Nummulites striatoreticulatus Rutten, 1928

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 : 575-580

Nummulites striatoreticulatus Rutten, 1928

( Fig. 15A–M )

1928 Nummulites striatoreticulatus Rutten : 1068, pl. 1, figs 41–50, F–J.

1941 Camerina vanderstoki (Rutten & Vermunt) ; Cole: 28, pl. 8, figs 5, 8.

1942 Camerina vanderstoki (Rutten & Vermunt) ; Cole: 27, pl. 8, fig. 10.

1958 Camerina striatoreticulata (Rutten) ; Cole: 265, pl. 32, figs 6–8.

1974 Nummulites (Nummulites) striatoreticulatus Rutten ; Frost & Langenheim: 74, pl. 11, figs 1–14, pl. 13, figs 1, 13.

1993 Nummulites striatoreticulatus Rutten ; Robinson & Wright: 331, pl. 30, fig. 5, pl. 30, fig. 6.

Material. Sixty-one well-preserved megalospheric specimens comprising 15 equatorial sections from Entronque de Herradura (98LC-2); 12 equatorial and nine axial sections from Loma Candelaria (98LC-1); seven equatorial sections from Loma El Santo (CA-215); and nine equatorial and nine axial sections from (E-126).

Description.

External features. The test is planispiral involute, inflated, biconvex with a lenticular contour and a diameter in the A form ranging from 1.7 to 8.5 mm. Surface smooth with radial septal traces forming distinctly raised lines radiating from the centre to the periphery.

Internal features. The embryonic apparatus is bilocular, proportionally small for the test size. Subspherical proloculus ranging from 0.12 to 0.40 mm followed by a reniform deuteroconch about 0.10 to 0.56 mm in diameter. Spiral exhibits a weaker marginal radius increase, producing numerous whorls. There are many simple chambers that are more or less equidimensional in the equatorial plane. In some specimens, chambers in the outer whorls can be up to 2 times as long as high. Chambers are divided by septa gently bent inwards (weak backbend angle), and supplementary passages can be present as a result of gaps in the septa between adjacent alar prolongations of the chambers. The well-developed marginal cord, with a fanshaped cluster of coarse canals, forms the chamber apex. Pillars visible in axial section usually do not reach the surface of the test.

Characters and attributes (means and standard deviations) for Nummulites striatoreticulatus and comparison to Palaeonummulites trinitatensis , Operculinoides floridensis (tightly coiled) and O. floridensis are given in Table 3 .

Occurrences. Early middle Eocene, P11/12, lower part of Loma Candela Formation; late middle Eocene to late Eocene, NP 16/17, upper part of Loma Candela Formation; late middle Eocene, CNE 13/ NP 16, Arroyo Blanco Formation; late Eocene, Jicotea Formation.

Remarks. Nummulites striatoreticulatus is one of the most widely recognized species of Nummulites in the Caribbean. It is distinguished from N. macgillavry by the much smaller diameter of the proloculus. In random sections, the range of morphological variation of the species P. trinitatensis overlaps with N. striatoreticulatus and it is difficult to distinguish between these two species. Nummulites striatoreticulatus is rare in the latest Eocene. It is almost absent in the Loma Viǵıa and Jabaco localities and sparsely present (two specimens) in the Norona section. These localities represent optimum conditions for orbitoids, with enormous numbers of microspheres and megalospheres of Lepidocyclina chaperi and L. pustulosa . Amphistegina cubensis is less abundant and might replace N. striatoreticulatus .

Stratigraphical and geographical distribution. Middle Eocene to late Eocece (Lutetian to Priabonian); Cuba, Mexico, Curacao, Florida, Trinidad, Costa Rica, French Lesser Antilles, Panaḿa, Jamaica and St. Bartheleḿey.

Figures

Figure 15. Nummulites striatoreticulatus Rutten. A–C, Entronque de Herradura; A, 98LC-2-686; B, 98LC-2-687; C, 98LC-2-1a. D–F, Loma Candelaria; D, 98LC-1-660; E, 98LC-1-630; F, 98LC-1-806. G–K, La Esperanza; G, E-126-474; H, E-126-466; I, E-126-458; J, E-126-470, gaps in the septa between adjacent alar prolongations of the chambers; K, E-126-459; L, M, Loma El Santo; L, CA-215- 865; M, CA-215- 65. A, B, E, F, H, I, L and M are A forms in equatorial section; C, D, G and J are A forms in axial section.