Polymerolepis undetermined

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 : 18

POLYMEROLEPIS SP.

( FIG. 6D ; TABLE 1; SUPPL. 1, FIGS. 5 , 7 , 11, 14)

Referred specimens —Very rare, one scale at level 458.67’ (139.8 m) and possible scale fragments from 430.5’ (131.2 m), 453’ (138.1 m), 492.3’ (150.1 m): Roberts Mountains Formation.

Description and comparison —The scales and scale fragments have finely noded ridges. The scale base is always flat or concave. The type material of P.whitei from the Lochkovian of Podolia shows a wide range of scale morphotypes (e.g., Obruchev and Karatajūtė-Talimaa 1967, pl. 2 figs. 1–4, Karatajūtė-Talimaa 1998, figs. 6, 7). Hanke et al. (2013, figs. 1–5) demonstrated in their description of a partial articulated specimen from the Lochkovian MOTH locality in the Northwest Territories, Canada assigned to P. whitei , comprising an anal fin and part of the caudal fin and peduncle, that the scale varia- tion over the body is even greater than seen in the type scales. Specimens referred to P. whitei from the younger Lochkovian (delta conodont Zone) Windmill Limestone, Simpson Park Range, Nevada include head, fin, and body scales ( Turner and Murphy 1988, table 1, figs. 2.14, 15, 20, 22–26). The Nevadan scales are the first record in the Silurian for this taxon. Given the morphological variation in scales from the known localities, it seems possible that more than one species is represented, so we only refer the BC II specimens to an open taxon within the genus rather than to the type species.

Figures

Figure 5. Funicristata nevadaensis n. gen. n. sp. from the uppermost Silurian of the Birch Creek II section. A–C. UCR 10750-3 (level 456.5') in crown views and magnified view of the crown ridges; D, E. UCR 10750-2 (level 456.5') in crown and lateral views; F, G. UCR 10746-10 (level 430.5') in anterocrown and crown views; H, I. UCR 10746-8 (level 430.5') in anterocrown and laterocrown views; J, K. UCR 10750-10 (level 456.5') vertical longitudinal section; L. UCR 10750-12 (level 456.5') horizontal section through crown. Abbreviations: c=canal; en=enameloid; h=hyphal boring; po=pore openings. Scale bars=0.1 mm in A, B, D–L, 0.01 mm in C; anterior is to left or down, otherwise arrows point to anterior. See Table 1 for meterage.

Figure 6. Chondrichthyan and stem osteichthyan scales from the uppermost Silurian of the Birch Creek II section; A, C–G, light microscope images of whitened specimens; B, ESEM image. A-C. Ellesmereia schultzei. A, scale UCR 10746- 44 (level 430.5’) in crown view (from Suppl. 1, fig. 5); B, UCR 10746-28 (level 430.5’) in anterolateral-crown view; C, scale UCR10746-45 (level 430.5’ in crown and lateral views (from Suppl. 1, fig. 4). D. Polymerolepis sp. scale UCR 10752-1 (level 458.67’) in crown view (from Suppl. 1, fig. 11). E-G. Lophosteus sp. cf. L. superbus. E, dermal bone fragment 10754-1 (level 468’) in external view (from Suppl. 1, fig. 12); F, G, tubercles UCR951-1, 2 (level 457’) in crown views (from Suppl. 1, fig. 10). Scale bars=0.25 mm, anterior of scale is up or to left, otherwise arrow points to anterior. See Table 1 for meterage.

Figure 7. Thelodont scales from the uppermost Silurian of the Birch Creek II section, all level 430.5' except B, C, G, K, L, P, Q. A. Trimerolepis sp. cf. T. tricava. UCR 10746-43 in crown view. B. Trimerolepis sp. AMF97876 (Parkes 1995, fig. 22.19, 20) from level 503’, base view. C.?Lanarkia sp. UCR 944-20 (level 527.25’) in lateral view. D.?Turinia sp. UCR10746-19, showing taphonomic effects and ultrasculpture, in crown view. E-J. Nikolivia spp. E. UCR 10746-13 with cell pattern on surface in crown view; F, UCR 10746-20 in crown view; G, AMF97875 (Parkes 1995, fig. 22.17, 18) from level 402' with possible bite marks, in crown view; H, UCR 10746-27 in ventral basal view; I, UCR 10746-25 showing taphonomic effects in crown view; J, Nikolivia sp. cf. N. auriculata, UCR 10746-18 in crown view. K, L. Apalolepis sp. AMF97872 (level 503’) (Parkes 2005, fig. 22.11, 12), crown and basal views. M-O. Talivalia sp. cf. T. elongata. M, UCR 10746-17 in crown view; N, UCR 10746-37 in crown view; O, UCR 10746-21 in lateral view. P-S. Barlowodus sp. cf. B. tridens. P,Q, AMF97874 (level 875’) in crown and basal views (Parkes 2005, fig. 22.15, 16). R, S, UCR 944-21 (level 527.25') in laterocrown view, closeup in S showing striated ultrasculpture. Scale bars=0.2 mm; anterior to left or top, otherwise arrow points to anterior. See Table 1 for meterage.