Struveria sp. 2

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

Struveria sp. 2

Figures 13L , 17A, 17C

Dalmanitina (Eudolatites) aborigenum Öpik, 1953: 26 (partim.), pl. 10, figs 86–87 (non pl. 10, fig. 85 = Dalmanites athamas Öpik, 1953 ).

Material. NMV P52483 (fragmentary pygidium), from PL 2269, Thomas locality F51, Costerfield. Wapentake Formation. For locality see Thomas (1960). NMV P139337 (cranidium), NMV P138209 (pygidium), from PL 206, Wallan. Bylands Siltstone.

Remarks. Compared to the pygidium of Struveria sp. 1 from Broadmeadows, the pygidium from Wallan (fig. 17A) is longer (maximum width about 150% sagittal length), with a wider axis (almost 33% maximum pygidial width anteriorly) and a greater number of axial rings (nine or ten) and pleural furrows (ten or 11). It is unlikely that these differences can be explained by the larger size of the Wallan pygidium, and we therefore consider it to belong to a separate species. The cranidium from Wallan (fig. 17C) is small and indifferently preserved but its morphology is consistent with assignment to Struveria .

The paratype of ʻ Dalmanitina (Eudolatites)ʼ aborigenum is a fragmentary pygidium from Costerfield, consisting of the anterior part of the axis and the adjacent part of the right pleural lobe (fig. 13L). It differs from pygidia of Dalmanites athamas , to which the holotype of aborigenum belongs, in that the inter-ring furrows do not shallow markedly medially but are deeply impressed across the entire width of the axis; the pleural furrows are not expanded but are short (exsag.), sharply impressed and similar in appearance to the interpleural furrows; and the anterior and posterior pleural bands are flat-topped. These characters suggest that the specimen belongs to Struveria , and it may be conspecific with the Wallan specimens which come from a similar stratigraphical level.

Figures

Figure 13. A–K, Dalmanites athamas Öpik, 1953. A, NMV P138215, thoracopygon, × 1.5, from the ʻIllaenus bandʼ, Costerfield. B, NMV P138219, pygidium, × 3.5, from PL2269, Costerfield. C, paratype NMV P52485, cranidium, × 2, from PL2262, Costerfield. D, G, NMV P138217, pygidium, × 2, from PL389, Costerfield. E, paratype NMV P52486, cranidium, × 2, from PL2269, Costerfield. F, NMV P138218 pygidium, × 2, from PL2269, Costerfield. H, holotype NMV P52484, pygidium, × 1.5, from PL2262, Costerfield. I, NMV P138223, thorax, enlargement showing granulation, from PL2269, Costerfield. J, NMV P139805, teratological pygidium, × 2, from PL386, Costerfield. K, NMV P52482, incomplete fixigena, holotype of ʻDalmanitina (Eudolatites) aborigenumʼ Öpik, 1953, × 2, from PL2269, Costerfield. L, Struveria sp. 2, NMV P52483, pygidium, paratype of ʻDalmanitina (Eudolatites) aborigenumʼ Öpik, 1953, × 3, from PL2269, Costerfield. (B, D are latex casts)

Figure 17. A, C, Struveria sp. 2, from PL206, Wallan. A, NMV P138209, pygidium, × 2. C, NMV P139337, cranidium,× 5.5.B, Dalmanitidae indet., NMV P127957, partial view of incomplete thorax, × 0.9, from old Costerfield Antimony Mine, Costerfield. D–F, Bessazoon sp. D, NMV P147769, pygidium (fragment), × 1.8, from PL256, Wallan. E, NMV P312817, cranidium (fragment), × 2.2, from PL6361, Springfield. F, NMV P147770, pygidium (fragment), × 2.4, from PL256, Wallan.