Sphaerophthalmus sp. C

Ahlberg, Per, Szaniawski, Hubert, Clarkson, Euan N. K. & Bengtson, Stefan, 2005, Phosphatised olenid trilobites and associated fauna from the Upper Cambrian of Västergötland, Sweden, Acta Palaeontologica Polonica 50 (3), pp. 429-440 : 434

Sphaerophthalmus sp. C

Fig. 3C .

Material.—An incomplete thoracic tergite (estimated width 2.9 mm).

Remarks.—The axial ring is convex (tr.) and very wide, about twice as wide as the pleura, and has a narrow crescentic articulating half−ring separated by a deep continuous furrow, and a slight swelling medially in front of a short, sharp axial spine. The pleura is horizontal proximally, but distally sharply bent down at approximately two−thirds of the distance to the outer edge. The lateral margin is straight, exsagittally orientated, and forms a fine ridge. The pleural furrow is distinctly incised and nearly reaches the lateral margin. The integument is very thin, as indicated by the intact anterior margin seen from the anterior edge. The external surface is almost smooth. The closest resemblance may lie with S. humilis in terms of the proportion of the axial ring to the pleura.

Figures

Fig. 3. A. Sphaerophthalmus sp. A, cranidium, SMNH Ar59729 (2.21), sample 2. B. Sphaerophthalmus sp. B, right librigena with intact eye, SMNH Ar59730 (3.11), sample 2. C. Sphaerophthalmus sp. C, incomplete thoracic tergite, SMNH Ar59731 (2.19), sample 2. D–F. Peltura cf. transiens (Brögger, 1882). D. Pygidium, SMNH Ar59732 (1.3), sample 1. E. Pygidium, SMNH Ar59733 (2.7), sample 2. F. Small pygidium, SMNH Ar59734 (3.12), sample 2. G. Peltura cf. paradoxa (Moberg and Möller, 1898), pygidium, SMNH Ar59735 (1.7), sample 1. H, I. Peltura sp. A. H. Pygidium, SMNH Ar59736 (1.2), sample 1. I. Transitory pygidium, SMNH Ar59737 (1.21), sample 1. J. Peltura sp. B, transitory pygidium, SMNH Ar59738 (1.6), sample 1. K–P. Indeterminate olenid fragments. K–M. Occipital rings. K. SMNH Ar59739 (1.19), sample 1. L. SMNH Ar59740 (1.15), sample 1. M. SMNH Ar59741 (2.14), sample 2. N. Axial ring seen edge on, SMNH Ar59742 (1.18), sample 1. O. Axial ring, SMNH Ar59743 (2.22), sample 2. P. Incomplete thoracic tergite, SMNH Ar59744 (1.24), sample 1. Scale bars 0.1 mm.