Paracornus poulseni, Malinky & Skovsted, 2004

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 : 558-559

Paracornus poulseni gen. et sp. nov.

Fig. 3E, F .

Holotype: MGUH 27089 from GGU sample 314835.

Type horizon: Bastion Formation, Lower Cambrian.

Type locality: North−East Greenland.

Etymology: In honour of Christian Poulsen, in recognition of his work on the faunas and stratigraphy of Greenland.

Diagnosis.—Same as for genus.

Material.—MGUH 27089–27090 and a single fragment from GGU sample 314835.

Description.—Seemingly orthoconic conch with apical curvature slightly to right when viewed from dorsum; sides of conch nearly parallel to each other in apical region with sides diverging due to increase in apical angle at approximately half the distance between apex and aperture; dorsum high with blunt median ridge; flanks adjacent to it seem to be straight, and lateral edges tightly rounded; aperture seems to be orthogonal but with broad shallow median indentation along dorsal rim, and lateral sinuses poorly developed to non−existent. Ligula apparently long with flattened anterior edge and gently dipping sides. Cross−section has rounded triangular shape.

Shell on dorsum covered with series of knob−like projections that are aligned to create what appear to be ribs; ribs follow pattern of growth lines; width of knobs equal to width of space between each row of knobs. Venter has widely and evenly spaced ribs which are most pronounced near lateral edges beginning where apical angle changes to become fainter both near the middle of venter and toward apex. Protoconch appears to be elongate and tubular.

Remarks.—Knowledge of this species is derived from a generally well−preserved holotype and two less well−preserved paratypes. The rows of knobs provide details of the aperture on the holotype because part of the apertural rim is broken on that individual. No other hyolith species reported from the Bastion Formation or elsewhere in the Lower and Middle Cambrian resemble Paracornus poulseni gen. et sp. nov. in apical angle or ornament.

Stratigraphic range and distribution.—Same as for genus.

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.