Nostovicina 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 : 15-16

NOSTOVICINA SP. CF. N. LACRIMA

( Figure 4M–P ; Table 1; Suppl. 1, figs. 19–21, 25–27, 29) Referred specimens —Scales from levels 518.3’ (158 m), 526’ (160.3 m), 527’ (160.6 m), 527.25’ (160.7 m), 549’ (167.3 m), 562’ (171.3 m), 562.6’ (171.5 m), 591.5’

(182.6 m), 599.5’ (182.7 m), 600’ (182.9 m), 712’ (217

m), including UCR 5439-8, -6, -4 (level 549’= 167.3 m), UCR 10768-1 (level 518.3’= 158 m): Roberts Mountains Formation.

Description —These scales from the BC II section have a range of morphotypes, within the range shown by the type material of N. lacrima , but are relatively rare in the samples. Scales are less than 0.3 mm wide with a shallow base, 4–6 sharp, single smooth ridges running back from the rounded anterior crown margin to mid-crown ( Fig. 4M–P ), and occasionally short weak ridges running down towards the base from the middle of the side of the crown ( Fig. 4M, N ). The crown is narrower than the base, but usually extends behind the posterior corner of the base.

Comparison —Some of the scales with short ridges on the side of the crown resemble the body scales of Nostolepis? tewonensis ( Wang et al. 1998) , from the late Wenlockian of Zoige county and early Lochkovian of Tewo county, China. Unfortunately, no histological description or illustrations were given for N? tewonensis , so it is unknown to which of the new histology-based genera, which Valiukevičius and Burrow (2005) separated off from Nostolepis sensu lato, this species conforms. Nostovicina lacrima type material comprises 100 scales, and so, like Nostolepis matukhini (see below), is relatively rare even in the type locality, and, given the number of nostolepid-type species erected by Valiukevičius (1994) from those type localities in Taimyr plus variation within species, we only tentatively assign the relatively rare scales in BC II section to N. lacrima .

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.