Nostolepis matukhini, VALIUKEVICIUS, 1994

Burrow, Carole Jan, Murphy, Michael & Turner, Susan, 2023, Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U. S. A., PaleoBios 40 (1975), pp. 1-32 : 16

NOSTOLEPIS MATUKHINI VALIUKEVIČIUS, 1994

( FIG. 4Q–T ; TABLE 1)

Nostolepis matukhini Valiukevičius 1994 , 157, 158, figs. 68.2–68.5, 69.1, 69.2, pl. 20.9, 20.10.

Type material — Holotype LIGG 30-1627 ; Uryum beds, Taimyr , Russia (Lower Devonian, Lochkovian).

Referred specimens —Scales assigned to this species occur at levels 527.25’ (160.7 m) and 562.6’ (170.1 m) and include UCR 5443-2, -5 (level 562.6’= 170.1 m): Roberts Mountains Formation.

Description —Scales with a distinctively ornamented crown, with 5–7 strong, smooth subparallel or radial ridges that bifurcate towards the anterior margin.

Posterolateral edges of the crown are straight and

smooth, converging at a slightly obtuse angle at the posterior corner ( Fig. 4Q–T ). The base is moderately convex, and the neck has only small pore openings. Scarcity of material precluded thin sectioning to examine histology.

Comparison —The crown ornament on N. matukhini scales is very distinctive, with all ridges bifurcating along the anterior margin, a feature not shown in any other nostolepid-type scales.

Figures

Figure 4. Nostovicina and Nostolepis sp. acanthodian scales from the Siluro-Devonian boundary levels of the Birch Creek II section. A. Nostovicina sp. cf. N. elegans: UCR 10755-1 (level 470.2’) in crown view (from Supplement 1, fig. 13). B–D, J. Nostovicina laticristata: B. UCR 10768-10 (level 518.3') in crown view; C, D. UCR 10768-6 (level 518.3') in anterocrown and crown views; J. UCR 10768-11 (level 518.3') horizontal thin section through crown. E–I, K, L. Nostovicina sp. cf. N. guangxiensis; E. UCR 5443-1 (level 562.6') in anterocrown view; F, G. UCR 5443-3 (level 562.6') in crown and lateral views; H. UCR 5443-4 (level 562.6') in posterocrown view; I. UCR 5443-6 (level 562.6') in crown view; K, L. UCR 5443-7 (level 562.6') vertical transverse section, magnified view of crown structure in L. M–P. Nostovicina sp. cf. N. lacrima: M. UCR 5439-8 in lateral view; N. UCR 5439-6 in posterior view; O. UCR 5439-4 (level 549') in lateral view; P. UCR 10768-1 (level 518.3') in anterior view. Q–T. Nostolepis matukhini: Q, R. UCR 5443-2 (level 562.6') in crown and laterocrown views; S, T. UCR 5443-5 (level 562.6') in crown and anterocrown views. Abbreviations: cgz=crown growth zones; h=hyphal borings; Sf=Sharpey’s fiber bundles. Scale bars=0.1 mm, anterior of scale is to right or up, otherwise arrows point to anterior. See Table 1 for meterage.