A new representative of a stylonuroid eurypterid from the Upper Devonian of the Kursk region, Russia

Abstract

© 2019, Paläontologische Gesellschaft. The paper deals with the description of a new species Soligorskopterus shpinevi, which was found in Upper Devonian deposits cropped out in the Mikhailovsky quarry (the City of Zheleznogorsk, Kursk region, Russia). The new species is based on the single although practically complete specimen visible from its abdominal side. The new species is characterized by following features: (1) widest part of the body is disposed in area of second/third sternites, the L/W ratio of prosoma is about 0.7; (2) compound eyes are crescentic, with rounded ends; (3) the ocelli are small, of ovoid shape, orientated along the prosoma, diverge towards anterior direction; (4) the ocellar area anteriory two-lobed, heart-like; (5) the metastoma of prolonged shape, with parallel lateral margins, straight posterior margin and round anterior margin; (6) the length of sternites is more or less equal; (7) the basal part of the telson is broad subtriangular. The upper Devonian deposits of the studied area show a distinctly regressive trend, which ended in complete change of the shallow water lagoon deposits by interruption of sedimentation up to the Jurassic time. This trend corresponds well to the “terrestrialisation” of the late Devonian environments, which could be also reflected in developing of “walking” of some of the Devonian eurypterids in contrast to less evolutionary advanced representatives of this group.