Poraspididae, Kiaer, 1932

Mark-Kurik, Elga, Blieck, Alain, Burrow, Carole J. & Turner, Susan, 2013, Early Devonian fishes from coastal De Long Strait, central Chukotka, Arctic Russia, Geodiversitas 35 (3), pp. 545-578 : 555-556

Poraspididae gen. et sp. indet.

( Fig. 6G, H )

MATERIAL. — Specimens GIT 580-4, 6 and 7 of the Institute of Geology, Tallinn University of Technology, Estonia: fragments of a flank scale ( GIT 580-4) and of undetermined plates ( GIT 580-6 and 7).

LOCALITY AND STRATIGRAPHIC HORIZON. — Locality (sample) 73, Tonnel’nyj Brook, south of De Long Strait , Chukotka ; Lower Member (1) of Enmakaj Formation, Lochkovian .

DESCRIPTION ħis material is represented by three small fragmentary remains of dermal bony elements. ħe specimen GIT 580-4 ( Fig. 6G ) is from a flank scale of a poraspidid heterostracan similar to the scales figured, for example, by Blieck (1982: pl. VIII: 2, 4: Poraspis rostrata Kiaer &Heintz, 1935 ). It bears six flat dentine ridges per mm as in various Poraspis Kiaer,1930 species from the Lochkovian of Spitsbergen ( Blieck& Heintz 1983: table 1). ħe specimen GIT 580-7 ( Fig. 6H ) has more vaulted (convex) and wider(2/mm) dentine ridges.It probably also comes from a poraspidid plate.

Figures

FIG. 6. — Heterostracan microremains from the Lower Devonian of Chukotka,Arctic far-eastern Russia:A, B, Traquairaspididae? gen. et sp. indet., specimen GIT 580-5, from locality (sample) 73, Tonnel’nyj Brook, Lower Member (1) of Enmakaj Formation, Lochkovian; C, Traquairaspididae? gen. et sp. indet., specimen PIN 3845/2, locality 73-4 (74-3), Tonnel’nyj Brook, Lower Member (4) of Pil’hikaj Formation,Lochkovian; D, Lepidaspis? sp., tessera,specimen GIT 580-2,locality 73,same origin as specimen 580-5 (A, B); E, F, Oniscolepis? sp., tesserae, specimens GIT 580-1 (E) and 580-3 (F), locality 73, same origin as specimen 580-5 (A, B); G, H, Poraspididae gen. et sp. indet.,fragments of a scale (G) and of a plate (H), specimens GIT 580-4 (G) and 580-7 (H), locality 73, same origin as specimen 580-5 (A, B); I, Heterostraci? indet., tessera (platelet), specimen GIT 580-8, locality 73, same origin as specimen 580-5 (A, B). Scale bars: A, C, 1 mm; B, 100 µm; D, 300 µm; E, G, 500 µm; F, H, I, 200 µm.