perneri, Vaškaninová & Kraft, 2016

Vaškaninová, Valéria & Kraft, Petr, 2016, A Unique Occurrence Of A Psammosteid Heterostracan On The Peri-Gondwanan Shelf In The Lower / Middle Devonian Boundary Marine Deposits, Fossil Imprint 72 (3 - 4), pp. 155-160 : 156

Schizosteus perneri ( RŮŽIČKA, 1929)

Pl. 1

For synonymy see Tarlo (1965: 63).

H o l o t y p e. NM-Lc 62 (National Museum, Prague).

T y p e l o c a l i t y. Prastav Quarry near Holyně, southwest of Prague.

T y p e h o r i z o n. Lower/Middle Devonian boundary beds, Emsian/Eifelian; Třebotov/Choteč limestones (see Discussion).

D e s c r i p t i o n a n d r e m a r k s. Růžička (1929) acquired the specimen NM-Lc 62 from the quarry workers without being told about the exact circumstances of the discovery. He presumed the origin on the basis of contemporary labours in the central part of the quarry wall.

We refer to the previous determination of the specimen to Schizosteus perneri ( RŮŽIČKA, 1929) as published by Tarlo (1965). We have no new data or observations to alter the diagnosis or the systematic position of the specimen, but we include remarks on some non-diagnostic features we have observed on the specimen.

The specimen represents a well preserved left branchial plate, with its dorsal surface exposed (Pl. 1, Fig. 1). It is covered with superficial dermal ornament laterally, whereas in the mesial area, the ornament is exfoliated, and the inner vascular bone surface exposed (Pl. 1, Fig. 2c). The plate is ca. 17 cm long, slightly convex, except for the anterior-most margin, which is concave (Pl. 1, Fig. 2a). The overall convex shape is increasing towards the posterior end (Pl. 1, Fig. 2b). Posterior to the concave area, a transverse fracture is visible. The ornament is composed of well-bordered roundish tubercles with radially oriented ribs, slightly almond-shaped in cross section. Meeting points of the ribs are oriented towards the lateral margin of the plate (Pl. 1, Fig. 2d–e) on each well preserved tubercle. The tubercles are small at the anterior margin of the plate, and gradually enlarge towards the posterior end. In the anterior displaced area, a cross section of the dermal layers is visible (Pl. 1, Fig. 2f), as well as the shape of the tubercles, which are narrower at the base. The tubercles tend to be arranged in diagonal rows on most of the plate surface.