Kuqaia quadrata Li, 1993

Kuqaia quadrata Li, 1993

Figs 5E, 5F View Fig 5 , 6 View Fig 6 , 7F and 7G View Fig 7

Material. NRM X12703; NRM X12704; NRM X12705; NRM X12706.

Description. Shell reniform in lateral view; elliptical in dorso-ventral view. Shell surface covered with 34–51 radial and 21 concentric ridges (based on a specimen preserved in lateral view). Ridges are flat-crested, never blade-shaped; radial ridges 5–9 μm wide, concentric ridges 7–13 μm wide. Radial and concentric ridges are equally developed, forming a regular, rectangular mesh-like ornamentation. Collar-shaped margin preserved on one specimen, 22 μm high. Back conspicuous, slightly thicker than concentric ridges. Caudal spine damaged.

Comparison: This species is distinguished from other species based on the prominence of both concentric and radial ridges forming a chequered pattern.

Dimensions: Length 413(449)467 μm; width 150(186)240 μm (four specimens).

Remarks. One specimen (NRMX12704) with an ornamentation of regular rectangular meshes composed of flat interconnecting ridges ( Fig 6A–6C View Fig 6 ), shows a predominance of concentric ridges at the venter and dorsum, and radial ridges in the lateral parts, possibly representing an intermediate ornamentation between Kuqaia yangii Cui et al., 2004 and K. quadrata . However, this specimen is broken, and the concentric ridges at the venter are inconspicuous; we tentatively identify it as Kuqaia quadrata .

Occurrence, unit and age. 46.97– 46.07 m, 42.25– 41.15 m, Kavlinge BH-928; Katslösa Member, Rya Formation; Pliensbachian.