Entogoniopsis major (Grove & Sturt) J. Witkowski, P.A. Sims, N.I. Strelnikova & D.M. Williams, comb. nov., 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

7. Entogoniopsis major (Grove & Sturt) J. Witkowski, P.A. Sims, N.I. Strelnikova & D.M. Williams, comb. nov.

et stat. nov.

(SEM: Figs 97–101 ; LM: Figs 102–107 )

BASIONYM: Triceratium venulosum var. major Grove & Sturt (1886 , Journal of the Quekett Microscopical Club Series 2(2): 327, pl. XIX, figs 15–16).

TYPE (here designated):—‘ Oamaru , Otago, New Zealand’ (BM46554, holotype! = Fig. 105 ) .

Triceratium majus (Grove & Sturt) Grunow (1888: 40 ; in Schmidt 1888: taf. 127, figs 1, 2).

Triceratium tabellarium var. majus (Grove & Sturt) De Toni (1894: 954) .

‘ Biddulphia majus (Grove & Sturt) ’ [sic] Hanna & Grant (1926: 133), nom. invalid.

Frustules subrectangular in girdle view ( Fig. 103 ), valves tripolar, most commonly with straight sides and broadly rounded poles. Valves with slightly concave or slightly convex sides and/or acute poles are less common ( Fig. 107 ). Prominent pseudocelli are located on the distal faces of stout polar elevations ( Figs 97, 100 ). Except for the poles and the valve face margin (both raised), valve face is deeply depressed ( Figs 97, 99 ). Within the depressed portion, minor raised areas occur representing local thickenings of the valve ( Fig. 97 ). Most such undulations bear a single areola ( Fig. 97 ). The thickenings and associated areolae appear randomly scattered, and large areas of the valve face are hyaline, including the margins ( Figs 97 , 102, 104–107 ). Mantle is steeply downturned, shallow, with a smooth, hyaline margin that is slightly expanded inwards ( Figs 98–99 ). The margin of the mantle lies at approximately the same level as the bottom of the valve face depression ( Fig. 99 ). Mantle largely hyaline, except for two to three rows of poroids ( Figs 99–100 ). Series of short, robust costae extend on valve interior, along each side of the valve ( Figs 98–99 ). Valvocopula attaches to the costae by means of a series of clasping devices, and to the expanded mantle margin by means of a fossa ( Figs 98, 101 ). Valvocopula is deeper than the mantle, closed, largely hyaline, except for few poorly defined rows of poroid areolae ( Fig. 100 ). Additional detached girdle element was observed, probably a copula of the epicingulum ( Fig. 97 ). Copula is closed, narrow, with well-defined rows of poroids, and a narrow hyaline band at the abvalvar margin ( Fig. 97 ). Measurements (n =20): average side length: 80.1–234 µm; 2 areolae in 10 µm; 2 costae in 10 µm, measured along valve face margin.

Typification:—The first mention of Triceratium venulosum (not identified as a variety) in Sturt’s unpublished catalogue is on p. 134, slide BM46554. This specimen is in valve view, with a minor portion of the valve face obscured by debris, and has girdle elements attached ( Fig. 105 ), which matches the specimen figured in Grove & Sturt (1886: pl. XIX, fig. 15). Also its size agrees well with the published illustration. Other specimens indicated in Sturt’s catalogue are either larger (BM46556), or situated with the valve tilted (BM46575). The specimen on slide BM46554, however, is not as densely areolated as the one illustrated by Grove & Sturt (1886); it is possible that the areolation pattern on the figure was modified to show what the authors considered typical morphology. Therefore we conclude that the specimen on slide BM46554 is the holotype of Entogoniopsis major ( Fig. 105 ).

Geographic and stratigraphic distribution ( Fig. 10, site 18): (a) specimens: Late Eocene-earliest Oligocene: Oamaru , New Zealand: BM stub P.1337 ( Figs 97–101 ), BM coll. Adams: G3, G28 ( Fig. 107 ),

G100, G659, GC3304, BM46554 ( Fig. 105 , holotype), BM61142, BM61276. Oamaru Diatomite outcrops at: ‘Railway

Cutting 9’: BM coll. Adams G72; Allan’s Farm: BM coll. Adams G89, G614 ( Figs 102, 104 ); Forrester’s: BM37914 ( Fig.

106), BM37916 ( Fig. 103 ); Jackson’s Paddock: BM coll. Adams G116; Cormack’s Siding: BM61141. Locality and age unspecified: BM coll. Adams TS317.

(b) records:

Late Eocene-earliest Oligocene: Oamaru , New Zealand: Schmidt (1888: taf. 127, figs 1–2, as T. majus , and fig. 3, as T. venulosum ; 1891: taf. 168, fig. 5, as T. majus ). Oamaru Diatomite outcrop at Cormack’s Siding: Grove & Sturt (1886: 327, pl. XIX, figs 15–16), De Lautour (1888: 311, pl. XXI, fig. 1).

18 • Phytotaxa 209 (1) © 2015 Magnolia Press

WITKOWSKI ET AL.

Observations:— The original publication of this species as a variety of Triceratium venulosum Greville (1864b: 90) has caused considerable confusion. Grove & Sturt (1886: 328) distinguished the variety based on the diameter of the valves, which are much larger in T. venulosum var. major than in Greville’s species. Grunow (1888) suggested the replacement species name T. majus for T. venulosum var. major and Grove’s later annotations (in Grunow 1889) indicate that Grove & Sturt accepted this name. Yet, Greville’s figure of T. venulosum (1864b: pl. XIII , fig. 21) is difficult to interpret and does not allow precise identification; furthermore, the holotype specimen of T. venulosum has not been located ( Williams 1988: 60), further complicating identification. As a result, the diatom reported from the Oamaru Diatomite by Grove & Sturt (1886) as T. venulosum var. major is commonly identified as both T. venulosum Greville and T. majus Grove & Sturt. Our study shows that Entogoniopsis major is absent from Greville’s Barbadean localities, suggesting that T. venulosum is not the same as T. venulosum var. major . Finally, Simonsen, in the 1968 reprinting of some of Greville’s papers, synonymized T. venulosum with Triceratium tabellarium Brightwell (1856: 275) , although he gave no reasons for doing so ( Simonsen 1968: xii; see discussion on Entogoniopsis tabellaria , below). In summary, T. venulosum is not the same as T. venulosum var. major and therefore we propose Entogoniopsis major comb. nov. et stat. nov. based on Triceratium venulosum var. major Grove & Sturt (1886: 327) .

Figures

FIGURES 97–101. Scanning electron micrographs of Entogoniopsis major from Oamaru, New Zealand. Fig. 97: Oblique external view of a hypovalve with a displaced epicingulum element (C? = copula?). Note the thickenings on the depressed part of the valve face. Fig. 98: Detail of the specimen in Fig. 99, showing poorly preserved clasping devices of the valvocopula attached to the internal costae. Fig. 99: Oblique internal view of a specimen with remnants of the valvocopula attached (arrow). Fig. 100: Girdle view of a specimen with a valvocopula attached (VC). Fig. 101: Oblique internal view of the specimen in Fig. 100, revealing well-preserved clasping devices embracing the internal costae (arrow), and a fossa holding the inward expansion of the mantle margin (arrowhead).

FIGURES 102–107. Light micrographs showing the range of morphological variation in Entogoniopsis major. Fig. 102: BM coll. Adams G614, Allan’s Farm, Oamaru, New Zealand. Fig. 103: BM37916, Forrester’s, Oamaru, New Zealand. Fig. 104: BM coll. Adams G89, Allan’s Farm, Oamaru, New Zealand. Fig. 105: BM46554, Oamaru, New Zealand, holotype. Fig. 106: BM37914, Forrester’s, Oamaru, New Zealand. Fig. 107: BM coll. Adams G28, Oamaru, New Zealand.