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


Table 1. Stratigraphic and locality information for all specimens of Soligorskopterus tchepeliensis n. gen. n. sp. examined in this study. Specimen


Year


BSUM P-276/P-170 BKM 942 BKM 943


1981/1982 2006 2008


BKM 1052 (holotype) 2012 Lost


Lost


1976 2002


Depth (m) 690


740 630


670 640


700


Eurypterida Burmeister, 1843 Stylonurina Diener, 1924 Stylonuroidea Diener, 1924 Stylonuridae Diener, 1924 Soligorskopterus new genus


urn:lsid:zoobank.org:act:46990205-E94F-4ACA-87D6- 545DAEEB5FC5


Type species.—Soligorskopterus tchepeliensis n. gen. n. sp., by monotypy.


Diagnosis.—Stylonurid of medium size, 12–34cm in length. Prosoma is horseshoe-shaped with a relatively narrow marginal rim. Compound lateral eyes are crescentic, located in the ante- rior half of the prosoma. Opisthosoma is wide, the metasoma bearing slight epimera, and tapering into a styliform telson. Prosomal appendages are robust, gradually increasing in length anteriorly to posteriorly. Prosomal appendages II − IV are spi- niferous Ctenopterus-type; prosomal appendages V and VI are nonspiniferous Parastylonurus-type. The metastoma is petaloid in shape, markedly narrower than long with an angular anterior notch and a flattened posterior margin. Type A genital appen- dage is long, reaching beyond the fifth opisthosomal segment, and is composed of at least two segments with a median ridge. Type B genital appendage is short and narrow. The pretelson is elongated and bears a pair of ridges ventrally comprised of large overlapping scales. Cuticular ornament is in the form of small, contiguous or separate, semilunate, linguoid-shaped and aci- cular scales, which in some places transform into ridges and crests.


Etymology.—The genus name is derived from the words Soli- gorsk (the town in Belarus closest to where the specimens were found) and pterus, meaning wing.


Remarks.—Soligorskopterus n. gen. is differentiated from all other stylonurid taxa in possessing a prosomal shield and opis- thosoma morphologically similar to Parastylonurus Kjellesvig- Waering, 1966, but prosomal appendages reminiscent of Pagea Waterston, 1962 and Laurieipterus Kjellesvig-Waering, 1966.


Soligorskopterus tchepeliensis new species


urn:lsid:zoobank.org:act:A0A05255-FE4B-42F0- 8CDF-26F1FBFE8AE7 Figures 3–6; Table 1


Latitude (°N) 52.88


52.89 52.85


52.87 52.87


52.84


Longitude (°E) 27.51


27.57 27.42


27.64 27.45


27.57


841


Lithologic and Stratigraphic Notes


Halopelite interbedded within a thick bed of halite separating sylvinite beds III and IV


Halopelite interbed located at the bottom of package 3 of sylvinite bed IV


Halopelite interbedded within layers of sylvinite, which are interbedded within a thick bed of halite separating sylvinite beds III and IV


Halopelite interbedded within a thick bed of halite separating sylvinite beds III and IV


Halopelite interbed of sylvinite bed III Halopelite interbed, at the bottom of sylvinite bed V


Type specimens.—Holotype, BKM 1052, Upper Devonian (middle Famennian), upper Soligorsk Formation, Pripyat Basin in the Pripyat Trough of Belarus. Paratypes, BKM 942, 943; BSUM P-276/P-170.


Diagnosis.—As for the genus.


Occurrence.—Upper Devonian (middle Famenian, Streshin regional stage), upper Soligorsk Formation (Osovets beds), near Soligorsk, Belarus.


Description.—The holotype (BKM 1052; Fig. 3) is the largest specimen of Soligorskopterus tchepeliensis n. gen. n. sp. recovered, with a length of 34 cm, and represents a mostly complete individual preserved in ventral aspect. The prosoma (71mm in length; 80mm in width; length/width ratio 0.89) is horseshoe-shaped with a comparatively narrow (3mm) mar- ginal rim. The lateral eyes are crescentic, located in the anterior half of the prosoma. The prosomal ventral plates are of Eurypterus-type, bearing a single median suture. Transverse sutures are evident on the ventral plates, expanding forward anteriorly. The prosomal appendages are incomplete, with appendages III–VI evident on the left and appendages IV–VI evident on the right. On appendage III, only the third and fourth podomeres are fragmentarily preserved, largely in the form of an imprint. The appendages of limb pair IV are also preserved


fragmentarily, being known from the second, third, fourth, and fifth podomeres. Podomeres four and five bear multiple rows of fixed spines. The cuticular ornament of these podomeres con-


sists of weakly expressed small scales. Appendages V and VI are better preserved than the previous appendage pairs. Appendage V is known from the coxa to the seventh podomere and is nonspiniferous. Appendage VI, also known from the coxa to the seventh podomere, also lacks spines. The fourth podo- mere of appendage VI is the longest, with subsequent podomeres reducing in length consecutively. Both appendages exhibit cuticular ornamentation of a row of small, closely situ- ated semilunate scales along the anterior third of each podo- mere. The lateral margins of the podomeres are also ornamented with a series of thickened scales. The metastoma is petaloid in shape with an angular anterior notch and a flattened posterior margin. The opisthosoma is generally broad but does not exceed the


maximum width of the prosomal carapace. The opisthosoma consists of 12 segments, divided between the six-segmented mesosoma anteriorly and the six-segmentedmetasoma posteriorly.


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