Gomphonchus 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 (4), pp. 1-32 : 12

publication ID

https://doi.org/ 10.5070/P940454153

publication LSID

lsid:zoobank.org:pub:58312615-0833-432E-BF5D-3DFFBF361AAA

DOI

https://doi.org/10.5281/zenodo.11488300

persistent identifier

https://treatment.plazi.org/id/B21CD55B-FFD3-FFEE-5ACE-8D26FD19243D

treatment provided by

Felipe

scientific name

Gomphonchus undetermined
status

 

GOMPHONCHUS SP. AFF. G. MEDIOCOSTATUS

( Fig. 3W–3Z View Figure 3 ; Table 1 View Table 1 ; Suppl. 1, figs. 20, 21)

Referred specimens —Rare scales assigned to this species occur in a very restricted range, at levels 526’ (160.3 m), 527.25’ (160.7 m), and possibly 527’ (160.6 m), and include UCR 944-6, -8, -17, -19 (level 527.25’= 160.7 m): Roberts Mountains Formation.

Description —Scales from BC II with crowns resembling the type scales of this species have a marked median sulcus extending over half the length of the crown, usually edged by sharp ridges. Smaller scales have only these two ridges ( Fig. 3W, X View Figure 3 ), larger scales have oblique lateral ridges directed towards the median ridges ( Fig. 3Y, Z View Figure 3 ). Most scales have a short- to medium-height neck. The base is strongly convex. Histological structure was not investigated, due to the lack of material.

Comparison —The type scales of Gomphonchus mediocostatus are from an upper Přidolí East Baltic-derived erratic limestone; the species is also recorded from Lithuania, Timan–Pechora (Valiukevičius 2005), Latvia ( Valiukevičius 2004b), the Welsh Borderlands ( Vergoossen 1999a) and Novaya Zemlya ( Burrow et al. 2018). In Latvia, Valiukevičius (2004b) nominated G. mediocostatus as the acanthodian index species for his second highest fine-scale biostratigraphic interval in the Přidolí. A crown ornament similar to that of G. mediocostatus has been illustrated in a number of other taxa, including Pechoralepis zinaidae ( Valiukevičius 2003b, fig. 3K) from the Lochkovian of Timan–Pechora, and one of the morphotypes of the older taxon Gomphonchus ? turnerae from the Ludlow of north Queensland, Australia ( Burrow and Simpson 1995, fig. 2A–C). The type scales of G. mediocostatus all have deep necks with relatively shallow bases, thus differing from the BC II scales with their short necks and deeply convex bases.

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