Plax et al.—New stylonurid eurypterid from Upper Devonian of Belarus


843


Figure 4. Soligorskopterus tchepeliensis n. gen. n. sp., paratype BKM 943; specimen preserving the ventral surface: (1) specimen photograph; (2) interpretive drawing. Abbreviations as in Figure 3. Scale bar=10mm.


only the proximal podomeres of appendages IV–VI preserved. Only the third and fourth podomeres of appendage IV are preserved, but they are fragmentary and do not preserve the armature. Appendages V and VI are both known from the coxa to the fifth podomere.Both appendages show the characteristic lateral border of thickened scales. The metastoma is petaloid, with an anterior notch and a truncated, flattened posterior. The lateral margins of the metastoma are remarkably straight, resulting in an almost rectangular appearance. A slight median ridge runs down the center of the metastoma. Small semilunate scales are present on the metastoma and the coxae. The opisthosoma is relatively broad and tapers regularly


throughout the metasoma. The mesosoma is generally well preserved. It is somewhat wider than the metasoma. The genital operculum is clearly composed of an anterior opercular plate, a median opercular plate (corresponding to the first opisthosomal segment), and a posterior opercular plate (corresponding to the second opisthosomal segment). The median opercular plate is 8mmin length and 73mminwidth at the base, whereas the posterior opercular plate is 9mm in length and 75mmin width at the base. A clear suture is present


between them. Both opercular plates have an ornament of small semilunate scales, whereas the posterior opercular plate also has acicular scales. A type B genital appendage is present, oval and elongated in shape, with a length of 13mm and a width of 3mm. The terminal part of the genital appendage is missing, and so it is impossible to ascertain how many segments it comprises. There are no deltoid plates evident alongside the insertion of the genital appendage, despite the region being well preserved. The remaining opercula are generally uniform in mor-


phology. The operculum of the third segment is 10mm in length with a posterior width of 77mm; that of the fourth segment is 11mm in length with a posterior width of 77mm; the fifth segment is 12mm in length with a posterior width of 71mm; and the sixth operculum is 12mmin length and 64mm in width at the base. The cuticular sculpture of the opercula comprises small semilunate and acicular scales. A median furrow is present on all the postgenital opercula, shallowing out just before the posterior margin of the sixth operculum. The opercula of segments 4–6 appear medially fused, however those of the third opisthosomal segment exhibit a median


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