Struveria Rickards, 1965

Sandford, Andrew C. & Holloway, David J., 2006, Early Silurian phacopide trilobites from central Victoria, Australia, Memoirs of Museum Victoria 63 (2), pp. 215-255 : 245-246

Struveria Rickards, 1965

Type species. Struveria howgillensis Rickards, 1965 from the upper Wenlock–lower Ludlow of northern England and North Wales, by original designation .

Remarks. Apart from the type species and the Victorian specimens described below, Struveria includes S. orba ( Barrande, 1852) from the upper Wenlock of the Czech Republic, and S. simrica ( Hede, 1915) from the upper Llandovery?–Wenlock of southern Sweden (see Laufeld et al., 1975) and the upper Wenlock of Poland ( Tomczykowa, 1991). S. howgillensis is the most completely known species ( Rickards, 1965:pl.85, figs 1–6) but neither this nor the other representatives have been extensively illustrated, and most are rather poorly preserved. Consequently the genus is not very well known morphologically, but distinctive characters include: a very short (sag., exsag.) anterior cephalic border; almost transverse S1 and S2, both containing apodemal pits; a moderately large eye extending very close to the lateral border furrow anteriorly and laterally; a long, flattened genal spine; a pygidium that is curved in outline posterolaterally and lacks a convex border or mucro; pygidial axial rings bearing oblique muscle impressions laterally, except for the last few; a narrow, rather sharp postaxial ridge; short (sag., exsag.), sharply impressed pygidial pleural and interpleural furrows, the pleural ones terminating distally a short distance from the margin whereas the interpleural ones reach the margin; and posterior pleural bands that are slightly more raised distally than the anterior bands towards the back of the pygidium.

Struveria orba was tentatively assigned to Delops by Šnajdr (1982), but the lectotype cranidium and other specimens figured by Šnajdr (1982: pl. 2, figs 5–10) resemble the type species of Struveria in the strongly transverse frontal lobe and distinctly concave lateral outline of the glabella behind a transverse line through the inner end of S3, and they lack the tuberculate sculpture and expanded (exsag.) pygidial pleural furrows characteristic of Delops . Two pygidia assigned to orba by Barrande, one of them a paralectotype ( Barrande 1852: pl. 26, fig. 38; Šnajdr 1982: pl. 2, fig. 1), are not conspecific with the lectotype but belong to Delops dermolac (see also Budil, 1996). ʻ Calymene ? daviesii Salter, 1865, known only from an internal mould of a pygidium from the upper Wenlock of Wales, was tentatively assigned to Struveria by Morris (1988: 223) but we cannot assess this assignment from the woodcut illustration of Salter (1865) (fig. 23).

As pointed out by Rickards (1965: 549) and Bergström (in Laufeld et al., 1975: 219), Struveria shows similarities to Eudolatites, a genus largely restricted to the Caradoc apart from the late Ashgill subgenus E. ( Deloites ) Destombes, 1972, which was regarded as an independent genus by Tomczykowa (1991) and Vaněk and Vokáč (1997). Eudolatites differs from Struveria in that S1 is more obliquely oriented; S2, though commonly rather deep,seems to lack an apodemal pit( Destombes, 1972: pl. 3, fig. 1a, pl. 4, fig. 1a); the librigenal field is much broader anterior and lateral to the eye; there is either no genal spine present, or it is short, strongly tapered,and rounded in cross section distally rather than flattened (see Rábano in Gutierrez Marco and Rábano, 1987: pl. 1, fig. 1c); and the pygidium lacks a sharply defined postaxial ridge.