Microcornus petilus Bengtson, 1990a

Malinky, John M. & Skovsted, Christian B., 2004, Hyoliths and small shelly fossils from the Lower Cambrian of North-East Greenland, Acta Palaeontologica Polonica 49 (4), pp. 551-578 : 556

Microcornus petilus Bengtson, 1990a

Fig. 3C, D .

Microcornus petilus Bengtson, 1990a: 217 , figs. 145–147. Microcornus petilus Bengtson, 1990a ; Wrona 2003: 194, fig. 8A–H.

Holotype: South Australian Museum , Adelaide SAMP30887 .

Material.— MGUH 27087–27088 from GGU sample 314835.

Description.—Orthoconic to slightly cyrtoconic conch with curvature toward dorsum; apical angle small creating narrow appearance for conch; venter slightly inflated, grading into tightly rounded lateral edges and then into straight flanks; flanks meet at prominent dorsal ridge; dorsum low, giving conch depressed triangular cross−section. Aperture amblygonal, defined by very broad though shallow lateral sinuses; central portion of dorsal apertural rim rises to form low protuberance on that side.

Shell varies from nearly smooth on both dorsum and venter to having prominent well−developed ribs on either or both sides; spaces between ribs equal to diameter of between 1–3 ribs; protoconch generally bulbous, tapering to a bluntly rounded apex.

Remarks.—Specimens from North−East Greenland assigned to this species match well the descriptions and illustrations of this species given by Bengtson (1990a) and Wrona (2003).

Stratigraphic range and distribution.—Lower Cambrian; Australia, Antarctica, and North−East Greenland.

Figures

Fig. 3. A, B. Microcornus eximius Duan, 1984. A. MGUH 27085; A1, dorsum; A2, right flank of dorsum; A3, venter; A4, cross−section and view of dorsum from aperture. B. MGUH 27086; B1, dorsum; B2, cross−section and view of dorsum from aperture. C, D. Microcornus petilus Bengtson, 1990a. C. MGUH 27087, venter. D. MGUH 27088; D1, dorsum; D2, venter. E, F. Paracornus poulseni gen. et sp. nov. E. MGUH 27089, holotype; E1, dorsum; E2, venter; E3, enlarged view of ornament at right lateral edge (venter to right). F. MGUH 27090, dorsum. G. Parkula bounites Bengtson, 1990a, MGUH 27091; G1, exterior of operculum from above; G2, exterior of operculum from conical shield; G3, lateral view of operculum with conical shield to right; G4, exterior of operculum with cardinal shield in foreground. A, D–G, from 314835; B, from GGU sample 314906; C, from GGU sample 314904. Scale bars 0.2 mm, except E3 which is 50 µm.