Amphipentas pentacrinus Ehrenberg (1840a: 205)

Sims, Pat A., Williams, David M. & Ashworth, Matt, 2018, Examination of type specimens for the genera Odontella and Zygoceros (Bacillariophyceae) with evidence for the new family Odontellaceae and a description of three new genera, Phytotaxa 382 (1), pp. 1-56 : 23-24

Amphipentas pentacrinus Ehrenberg (1840a: 205) ( Figs 87–90 )

Basionym:— Triceratium pentacrinus (Ehrenberg) Wallich (1858: 249 , pl. 12, figs 10–14)

Synonym:— Biddulphia pentacrinus (Ehrenberg) Boyer (1900: 717)

Type:— “Fossilis in Graeciae marga” ( Ehrenberg 1840a: 205)

Observations:— The basic outline and structure of A. pentacrinus differs little from A. boryana (description above). The differences lie in the number of poroid areolae within the anastomosing costae which are 4–8 (14) in A. pentacrinus , and the lack of interstices between radial costae linking elevations to valve centre ( Fig. 87 ). In A. pentacrinus the mantle is linked to the outer edge of the expanded valve margin by buttressed costae ( Figs 87, 88 ).

The description above is based on material from Ambrim, New Hebrides [Ambrym, Vanuatu] and Port Shepstone,

Natal, South Africa.

Figures

FIGURES 87–90. Amphipentas pentacrinus Ehrenberg (Ambrin, New Hebrides [Ambrym, Vanuatu]). Fig. 87. Exterior pentagonal valve with elevations at each pole, an ocellus on summit; valve covered in anastomosing costae with long costae linking elevations to depressed valve centre; scale bar = 10 μm. Fig. 88. Elevation with distally inclined ocellus on summit, note hyaline valve margin extending beyond valve face, mantle attached by costae to its margin; scale bar = 1 μm. Fig. 89. Openings from rimoportulae situated submarginally equidistant between ocelli, anastomosing costae enclosing several poroid areolae, most occluded by cribra with an occasional specialised pore (arrow); scale bar = 2 μm. Fig. 90. Interior with opening from rimoportula, interior openings of cribra and a specialised pore (arrow); scale bar = 1 μm.