HETEROSTRACI (Dineley & Loeffler, 1976)

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 : 557

HETEROSTRACI? indet.

( Fig. 6I )

MATERIAL. — Specimen GIT 580-8: isolated tessera or platelet.

LOCALITY AND STRATIGRAPHIC HORIZON. — Same as specimens GIT n°580-1, 2, 3, 4, 6 and 7: locality (sample) 73, Tonnel’nyj Brook, south of De Long Strait, Chukotka; Lower Member (1) of Enmakaj Formation, Lochkovian.

DESCRIPTION ħis specimen is an isolated square-shaped element (either a tessera or platelet), partially broken, and with an altered surface. It bears a single, probably central, star-shaped tubercle ( Fig. 6I ). Because it is larger (c. 3.2 mm long for its preserved part) than all other tesserae that have been prepared from sample 73 of the Coast section, we suggest that it might correspond to a different taxon. Furthermore, with such a small sample (a single specimen), no thin section has been made, and thus its histology is not confirmed as being of a heterostracan.

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.