Radioporacanthodes scheii

• Main Authors: Burrow, Carole Jan, Murphy, Michael, Turner, Susan
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2023
• Subjects: Biodiversity; Taxonomy; Animalia; Chordata; Ischnacantiformes; Poracanthodidae; Radioporacanthodes; Radioporacanthodes scheii; Arctic; Canada; Devon Island; Ellesmere Island; Irene Bay
• Online Access: https://doi.org/10.5281/zenodo.11488268; http://treatment.plazi.org/id/B21CD55BFFD7FFE959F68C8BFBA8220F

RADIOPORACANTHODES SCHEII (SPJELDNAES, 1967) (FIG. 2 CC–EE; TABLE 1; SUPPL. 1, FIGS. 2, 3, 5, 9 –13) Ischnacanthus ? Scheii Spjeldnaes 1967, 807, figs. 1–3, pl. 1. Radioporacanthodes scheii Burrow 2013, 947, figs. 2-6. Diagnosis —see Burrow (2013). Type material — The holotype is fin spine CMN55213, in a block with other fin spines, jaw fragments and scales considered to be conspecific; from the northwest side of Irene Bay, Ellesmere Island, arctic Canada, Devon Island Formation (Přidolí? or early Lochkovian). Referred specimens —Rare scales recognized at levels 395’ (120.4 m), 424.9’ (129.5 m), 430.5’ (131.2 m), 456.5′–471′ (139.1-143.6 m) in the BC II section, including UCR 10750-1, -5 (level 456.5’= 139.1 m): Roberts Mountains Formation. Description —These scales are characterised by regularly spaced short sharp ridges along the anterior edge of the crown, without a median sulcus. Pore openings are relatively small, with a maximum of six subparallel rows running back along the posterior half of the crown (Fig. 2 CC-EE). The undersurface of the posterior crown has the large canal openings characteristic of this family (not illustrated). The small pores on the crown surface are not always visible with a light microscope, and some scale varieties lack pores. Comparison — Burrow (2013) reassigned this species from “ Ischnacanthus ?” to Radioporacanthodes based on presence of a pore canal system in the crown of most scales, while also recognising that some variants lack a pore canal system. The BC II scales show some similarity with those of Poracanthodes canadensis in having many short ridges along the anterior edge of the crown, but differ in having a few small pores in subparallel rows on the posterior crown, rather than rows of many pores paralleling the posterolateral crown edges. As noted above, some scales also lack a pore canal system, making it difficult to distinguish these from scales of Gomphonchus volborthi (Rohon, 1893), a species resurrected by Vergoossen (1999c), and Gomphonchus sandelensis ...