Smithicyathus mcleani, Wrzołek, 2007

Wrzołek, Tomasz, 2007, A revision of the Devonian rugosan phillipsastreid genus Smithicyathus, Acta Palaeontologica Polonica 52 (3), pp. 609-632 : 618

Smithicyathus mcleani sp. nov.

Fig. 6B, C.

1962 Phillipsastrea cincta Smith ; McLaren and Norris 1962: pl. 11: 28, 29 (colony re−illustrated here in Fig. 6C)

1994 Smithicyathus cinctus ( Smith, 1945) ; McLean 1994b: 80–82 (partim), pl. 2: 2–5 (non pl. 3: 1–4 = S. cinctus ).

Derivation of the name: In honour of Ross McLean, student of Devonian Rugosa .

Holotype: GSC 98208 (illustrated by McLean 1994b, pl. 2: 4, 5 and re−illustrated here in Fig. 6B), a colony.

Type locality: NW flank of Mount Mackenzie (Amoco Loc. 11411), Alberta, Canada ( McLean 1994b: 81).

Type horizon: Uppermost Frasnian (the top of Simla Formation).

Material.— Besides the holotype there are 2 other colonies listed by McLean (1994b: 80, 81) from the Uppermost Frasnian of Alberta, Canada: GSC 98207 from Eagle’s Nest Pass (Amoco Loc. 15255) and GSC13826 probably from Simla Fm of Cardinal Mountain ( GSC Loc. 24398) .

Diagnosis.—Submassive (phaceloid) colonies of Smithicyathus , commonly with cerioid walls in their massive fragments, and with well developed peripheral dissepimentaria. Corallites are large: their diameter is from 5.5 to 5.8 mm, tabularium diameter is from 2.99 to 3.5 mm.

Description.—The colonies are phaceloid, densely packed with corallites (Fig. 6B 1, C 1). Cerioid walls between the neighboring corallites are common, although pseudocerioid (septal) walls can also occur and in places walls are totally absent, possibly between parent–offset (Fig. 6C 1). Septa of both orders barely enter tabularium, they may be to a various degree withdrawn from the corallite periphery. The horseshoe dissepiments are developed in a single series at the tabularium–dissepimentarium boundary (Fig. 6B 2, C 2), locally they can be replaced by peneckielloid dissepiments in narrower fragments of corallites (Fig. 6B 2). At the corallite periphery there are typically one or two rows of peripheral, globose dissepiments. Tabularium is with mostly complete, usually flat tabulae.

Discussion.—Although McLean explicitely noted (1994b: 81) that high intracolony variation speaks for both phaceloid and massive colonies being included in a single species, namely Smithicyathus cinctus , the current re−examination of available material from the Upper Frasnian of Western Canada (6 colonies) suggests there are in fact two distinct species present there. The first is a massive species (presented as S. cinctus above), the other, S. mcleani sp. nov., is phaceloid and has large tabularia. The new species is numerically very close to S. lacunosus from the Holy Cross Devonian (described below); in fact comparison of most measured parameters (see Appendix 2: columns “b” and “c”) shows either very close or overlapping variability ranges of the two species. Generally, however, the separate species status of S. mcleani sp. nov. is indicated by: (1) larger tabularia, combined with (2) the morphometrical similarity of corallites to those of massive S. cinctus , and (3) analysis of variability of the total sample of phaceloid colonies indicating high “atypicality” of the Alberta material ( Table 1, prefixed GSC), in relation to “typical” colonies representing Smithicyathus lacunosus .

Stratigraphic and geographic range.—Uppermost Frasnian of Alberta, western Canada: Simla Formation and probable Simla Formation. More details on sampling locations are in McLean (1994b: 81, listed by him among the material of S. cinctus ).