Nostolepis, Burrow, 2003

Burrow, Carole J., 2003, Earliest Devonian gnathostome microremains from central New South Wales (Australia), Geodiversitas 25 (2), pp. 273-288 : 276-278

publication ID	https://doi.org/ 10.5281/zenodo.5376020
persistent identifier	https://treatment.plazi.org/id/020087A6-3245-3116-FCA9-F9C74B2DFC82
treatment provided by	Marcus
scientific name	Nostolepis
status

Treatment

Nostolepis ? spp. indet.

MATERIAL EXAMINED ( Table 1). — Two flank s c a l e s i n c l u d i n g f i g u r e d s c a l e M M M C0 2 5 5 8

( Fig. 2E, F View FIG ), a possible branchial scale MMMC02559 ( Fig. 2G View FIG ), one “ N. applicata ”- type scale and one tooth whorl MMMC02560 ( Fig. 3A, B View FIG ) from sample C925 ; one flank scale and one “ N. applicata ”- type scale MMMC02552 ( Fig. 4C, D View FIG ) from C923 .

DESCRIPTION AND REMARKS

Flank scales ( Fig. 2E, F View FIG )

These two scales are twice as big as those assigned to N. lacrima . MMMC02558 is 0.7 mm wide, with a horizontal crown, five short anterior crown ridges which are radially directed relative to the posterior corner, and a short diagonal ledge on each postero-lateral vertical face of the crown. Except for this ledge and their larger size, the scales are morphologically similar to those of N. lacrima ; however, they also resemble scales which have been assigned to several other taxa including “ Gomphonchus cf. hoppei ” from the Lochkovian of Ellesmere Island (Vieth 1980: pl. 8, fig. 9) and Nostolepis taimyrica from the Pragian-Emsian of Tareya, Russia (Valiukevic˘ius 1994: pl. XVIII, fig. 5a, b). Scales of this general shape have traditionally (although perhaps not correctly!) been assigned to Nostolepis . Because there are so few scales, their histological structure was not determined.

?Branchial scale ( Fig. 2G View FIG )

Scale MMMC02559 has a crown which is smaller than the base, with three ridges extending almost to the weakly curved posterior edge, from the centre of which a single ridge extends down towards the base/neck rim. This scale type resembles flank scales of “ Nostolepis ” guangxiensis Wang, 1992 but differs in lacking a flat horizontal crown plane with a sharp posterior corner. Scales of this type are found in the branchial region of one of the enigmatic fish – specimen UALVP42273 – from the Lower Devonian MOTH site in the Northwest Territories, Canada (pers. obs.; G. Hanke pers. comm. 2000), and are likely to be a morphotype common to several different species .

“ N. applicata ”- type scale ( Fig. 4C, D View FIG )

Scale MMMC02552 is 0.7 mm long and 0.4- 0.5 mm wide, with a flat base having an irregularly polygonal outline. The ornament comprises separate areal growth zones stacked against each other like petals, most of which have broken off. Vieth (1980: pl. 4, figs 6-17) erected a new taxon Nostolepis applicata for scales with this general form from the Lochkovian Red Canyon River Formation Member A, Ellesmere Island, Arctic Canada. However, scales with this form have been recognized as a morphotype found in several different species, rather than being a biological taxon: e.g., the “tessera-like head platelets” of Nostolepis linleyensis Miller & Märss, 1999 ( Miller & Märss 1999: pl. 5, figs 2-5) and some of the coronate plates and stellate tessera of Nostolepis striata ( Gross 1971: pls 2, 3).

Tooth whorl ( Fig. 3A, B View FIG )

This element is very small, being 0.4 mm wide and 0.3 mm long. Its base is slightly concave antero-posteriorly with a curved anterior and a straight posterior edge. The two teeth are extremely worn and flattened, with a shallow groove visible between them on the upper surface of the bone base. The teeth are presumed to have had larger central cusps, flanked by smaller cusps on the posterior tooth, which have all worn down to stubs. There is no indication of an enameloid surface on the teeth. The element, though smaller, shorter and more worn-down, resembles a tooth whorl of Nostolepis striata ( Gross 1971: pl. 3, fig. 32a-c).