Trilamina wittiana, J.Witkowski, P.A.Sims, N.I.Strelnikova & D.M.Williams, 2015

Witkowski, Jakub, Sims, Patricia A., Strelnikova, Nina I. & Williams, David M., 2015, Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser, Phytotaxa 209 (1), pp. 448-450 : 448-450

2. Trilamina wittiana (Truan in Truan & Witt) J. Witkowski, P.A. Sims, N.I. Strelnikova & D.M. Williams,

comb. nov.

(SEM: Figs 230–235 ; LM: Figs 236–238 )

BASIONYM: Triceratium wittianum Truan in Truan & Witt (1888, Die Diatomaceen der Polycystinenkreide von Jérémie in Hayti Westindien: 23, pl. VII, fig. 16).

TYPE:—‘Jérémie’.

Valves tripolar, with tapering or broadly rounded projections, and deeply concave sides ( Figs 236–238 ). Valve face undulate, with margins and the central area raised to equal level, and a prominent depressed area within each projection ( Fig. 230 ). The central area and the depressed areas are hyaline ( Figs 230–231 ), except for a poorly defined ring of sparse poroid areolae in the marginal part of the central area ( Fig. 230 ), and few poroids next to the mid-point of each side ( Figs 236–238 ). The raised valve face margin, and most of the mantle are finely areolated, with poroid areolae aligned in rows parallel to the pervalvar axis ( Figs 230, 232 ). Areolae become slightly reduced at each pole, which may represent a poorly defined pseudocellus ( Fig. 232 ). Mantle is shallow, steep, but with a gradual valve face-mantle transition ( Figs 230, 232 ). At the mid-point of each side, a narrow hyaline area is present on the mantle ( Fig. 230 ). Mantle margin is smooth, hyaline, slightly expanded inwardly ( Fig. 233 ). On the valve interior, there is a series of robust costae radiating in regular intervals from each of the depressed hyaline areas ( Figs 231, 234 , 236–238 ). Additional, shorter costae are found on the underside of the raised central area ( Fig. 231 ). Next to the junction of the central area and the projections, two large costae protrude from each of the depressed hyaline areas toward the mid point of the adjacent sides ( Figs 231, 235 ). These large costae provide attachment for the large clasping devices located on the valvocopula ( Fig. 235 ). Small clasping devices on the valvocopula attach to the remaining marginal costae ( Figs 231, 233–234 ), and a fossa attaches to the inward expansion of the mantle margin ( Figs 231, 233 ). Valvocopula is closed, its depth comparable to that of the mantle ( Figs 230, 232, 234 ). A single row of evenly spaced poroid areolae, interrupted only where the large clasping devices are located, is immediately adjacent to the fossa ( Fig. 234 ). Otherwise, the valvocopula is hyaline ( Figs 230, 232–234 ). Measurements (n =5): average side length: 49.8–87.0 µm; 3–4 costae in 10 µm measured along the valve face margin; 3–4.5 areolae in 5 µm measured across a projection; 8–10 rows of areolae in 10 µm, measured along a projection.

Geographic and stratigraphic distribution ( Fig. 10, sites 21, 26):

(a) specimens:

Early Miocene: Jérémie, Haiti: BM63801 ( Fig. 238 ).

Middle Miocene : Wonosari-Series, Java, Indonesia: BM stubs P.683 ( Fig. 234 ), P.1319 ( Figs 232, 235 ), and P.1333 ( Figs 230–231, 233 ), BM36216 ( Fig. 236 ; label reads „Reinhold sample AY-12”), BM63802 ( Fig. 237 ).

(b) records:

Early Miocene: Jérémie, Haiti: Truan & Witt (1888: 23, pl. VII, fig. 16);.

Middle Miocene : Wonosari-Series, Java, Indonesia: Reinhold (1937: 129, pl. 19, figs 11–12).

Observations:— Trilamina wittiana is known from Jérémie, Haiti, and Java, Indonesia; only specimens from Java

32 • Phytotaxa 209 (1) © 2015 Magnolia Press

WITKOWSKI ET AL.

have been available for SEM examination. As figured in Truan & Witt (1888: pl. VII, fig. 16), specimens from the type locality have broadly circular projections, whereas valves from the Javan material ( Reinhold 1937) consistently have tapering, wedge-shaped projections. A specimen on slide BM63801 (Jérémie; Fig. 238 ) has a single row of poroid areolae located along the margin of the depressed hyaline area in each of the projections. No such perforations were observed in the specimens from Java. However , we see no additional morphological differences between the specimens from both localities. In particular, the morphology of the central area is identical in all examined specimens. Finally , the comparable age of both deposits, and their location in tropical latitudes, strongly suggests that specimens from Jérémie and Java are conspecific .

The valve outline of T. wittiana from Jérémie is similar to that of Trilamina tripes comb. nov. ( Fig. 249 ). The difference between the two is that the depressed parts of the projections in T. wittiana are hyaline or bear a single marginal row of poroids, whereas in T. tripes the entire central part of each projection is perforated. Given the large uncertainty in the age assignment of the various Barbadean deposits, it is impossible to confidently state that T. tripes (originally proposed from Mount Hillaby, Brun 1896: 246) is age-equivalent to T. wittiana . However, the valve outline similarity suggests that these two taxa may represent valves of heterovalvar frustules. Examination of intact frustules is required to verify this hypothesis.

Figures

FIGURES 230–235. Scanning electron micrographs of Trilamina wittiana from sample AY-12, Java, Indonesia. Fig. 230: Oblique external view of a frustule with preserved valvocopulae (VC), showing the prominent, depressed hyaline areas within each projection. The fracture reveals internal costae (arrow) and the fossa. Fig. 231: Oblique internal view of a specimen with attached fractured valvocopula. A cross-section through the fossa is indicated by the arrow. Fig. 232: Detail of the distal part of a projection in a specimen with attached valvocopula (VC). Note the poorly defined pseudocellus indicated by the arrow. Fig. 233: Detail of a fractured projection revealing the clasping devices on the valvocoupla holding the remnants of internal costae (arrow). Fig. 234: Internal oblique view of a partly dissolved valve, showing clasping devices of the valvocopula (VC) attached to the internal costae (black arrows). Note the single row of poroids on the valvocopula (white arrow), adjacent to the fossa. Fig. 235: Detail of the valve interior, showing the large clasping device attached to the prominent costae along the margin of the central area (arrow).

FIGURES 236–238. Light micrographs showing the range of morphological variation in Trilamina wittiana. Fig. 236: BM36216, Java, Indonesia (label reads: ‘Reinhold sample AY-12’). Fig. 237: BM63802, Java, Indonesia. Fig. 238: BM63801, Jérémie, Haiti.

FIGURES 249–252. Light micrographs of some of the new combinations proposed in this study. Fig. 249: BM63779, Trilamina tripes, Joe’s River, Barbadoes. Fig. 250: BM2763, Trilamina denticulata, Cambridge, Barbadoes, holotype. Slide thickness prevents Köhler illumination. Fig. 251: BM2111, Trilamina rotundata, Barbadoes, holotype. Slide thickness prevents Köhler illumination. Fig. 252: BM3078, Trilamina obesa, Cambridge, Barbadoes, holotype.