Cordilleria oculina ( Sando, 1963 )

Fedorowski, Jerzy, Bamber, E. Wayne & Richards, Barry C., 2021, Mississippian colonial tabulate and rugose corals from the Flett Formation, Liard Basin, northwest Canada, Acta Palaeontologica Polonica 66 (3), pp. 679-704 : 695-699

Cordilleria oculina ( Sando, 1963)

1963 Lithostrotion (Siphonodendron) oculinum sp. nov.: Sando 1963: 1075, pl. 145: 2–5 only.

1969 Lithostrotion (Siphonodendron) oculinum Sando ; Sando 1969a:

309, pl. 35: 2–5. 1985 Lithostrotion (Siphonodendron) oculinum Sando ; Sando and Bamber 1985: pl. 5: 8, 9.

Type material: USNM 143243 .

Type locality: Redwall between Bridge Canyon and the Peach Springs- Nelson area, south of the Grans Canyon ( Sando 1963: 1074).

Type horizon: Redwall Limestone, C Member, Kinderhookian Series, upper Tournaisian. Mississipian, Carboniferous.

Emended diagnosis.—Fasciculate colonial coral with maximum n:d value of 23–25:5.6 mm and most common n:d value of 20:4.5–5.2 mm and 21:4.5–4.8 mm ( Fig. 12 ). Major septa amplexoid, on tabula surfaces reach up to 2/3 corallite radius, reduced to 1/3–1/2 corallite radius when sectioned between tabulae, i.e., terminated at steep, peripheral parts of tabulae. Minor septa up to 1/2 length of majors when latter not elongated, commonly enter peripheral part of tabularium. Pseudocolumella short, thin, commonly interrupted. Tabulae slope from pseudocolumella at angle of 20°–40° in long inner parts, trapezoid to slightly convex when pseudocolumella absent, sharply deflected downward at periphery; most horizontal near dissepimentarium; some rest upon underlying tabulae. Dissepimentarium in one, incomplete row of interseptal dissepiments

Remarks.—The synonymy is restricted to the papers dealing with the holotype. The emended diagnosis, comprising all main characteristics of skeleton of the holotype, is based on Sando 1963: 1075, 1076, pl. 145: 2–5.

Stratigraphic and geographic range.— Type locality and horizon only.

Cordilleria aff. oculinum ( Sando, 1963)

Figs. 12 , 13 .

Material.— Five fragments of colonies from Flett Formation , Rundle Group , Liard Basin , Northwest Territories, Canada: IG-16 = UAM-Tc./Can.5, IG-30 = UAM-Tc./Can.7, Tlogotsho Member , lower Viséan ; IG-85 = UAM-Tc./Can.6, Meilleur Member, middle Viséan ( Fig. 6 ); C-52268 = GSC 142473 , C-52361 = GSC 142474 , Meilleur Member, middle Visean; and C-52205 = GSC 142472 from Prophet Formation, Rundle Group, Liard Basin, Northwest Territories, Canada. All colonies diagenetically altered by recrystallization and dolomitization that destroyed microstructure of septa in all corallites .

Description.—Intra- and inter-colony variation advanced in both n:d values ( Fig. 12 ) and in morphological characteristics ( Fig. 13 ). Amplexoid character of major septa weakly accentuated, resulting in their comparatively small length, not exceeding 1/2 corallite radius, commonly less. All major septa thin, equal in length. Cardinal fossula absent. Minor septa differentiated in length from hardly recognizable projections on surface of external wall to well developed, penetrating outermost tabularium. Pseudocolumellae underdeveloped to various extent, short and thin when present; very rare in most colonies ( Fig. 13A 1 , E, F), probably absent from some corallites ( Fig. 13A 2 ). In acolumellate parts of corallites tabulae complete, with flat sectors extending through major part of corallite diameter, sloping steeply down in their short peripheral sectors to meet external walls or dissepimentarium ( Fig. 13A 2 , B 1, D 1 , white arrow). In columellate corallite growth intervals, tabulae elevated towards pseudocolumella under various angles, but not steeply ( Fig. 13C, D 1 , black arrow). Dissepiments in one row, may be absent from great distances of corallite growth ( Fig. 13A 2 ).

Remarks.— Sando (1963: fig. 1) suggested wide intraspecific variability in n:d value of this species. However, a great majority of his specimens are located within narrow limits similar to the intra-colony variation in the holotype. Small specimens are immature (omitted here from Fig. 12 ). Large corallites are very rare. Most specimens here identified as C. aff. oculinum resemble the type collection in the number of septa present, but differ in larger corallite diameter, i.e., their n:d value differ from that in both the holotype and the type collection. The amplexoid character of the major septa, weakly accentuated in the specimens described here, differs from that in the type collection. That amplexoid weakness results in the absence of short projections of major septa on surfaces of tabulae, apparently characteristic for the holotype. Very short minor septa in some colonies are characteristic for C. warreni rather than C. oculinum , whereas the morphology in longitudinal section in those colonies points towards the latter.

Cordilleria sp.

Figs. 14 , 15 .

Material.— Four fragments of colonies from Flett Formation , Rundle Group , Liard Basin , Northwest Territories, Canada: IG-18 = UAM-Tc.Can./10, middle part of the Tlogotsho Member , lower Viséan ; IG-82 = UAM-Tc.Can./8, IG-83 = UAM-Tc.Can./9, lower part of the Meilleur Member, middle Viséan ( Fig. 6 ); C-47942 = GSC 142475 , Flett Formation undivided, Viséan. All specimens recrystallized and/or dolomitized; some strongly ( Fig. 15A 1 , B). Thin sections and peels available for the study .

Description.—Diameters and numbers of septa in all colonies similar in most corallites measured with only rare corallites of colony UAM-Tc.Can./8 larger ( Fig. 14 ). Major septa thin, vary in length in particular colonies; shortest and weakly amplexoid in colony UAM-Tc.Can./10, reach 2/3 corallite radius at most ( Fig. 15C 3 ), longest and almost non-amplexoid in colony GSC 142475 ( Fig. 15B 1 , B 2 ), almost approach corallite axis in some corallites. Length of major septa in remaining two colonies ( Fig. 15A 1 , D) intermediate between those two. In all colonies, minor septa penetrate tabularium; in colony GSC 142475, longest, extending up to 4/5 length of major septa. Dissepimentarium complete in most corallites, comprises 2–4 rows of interseptal, rectangular dissepiments. Only in colony UAM-Tc.Can./10 dissepimentarium incomplete in some fragments of corallites, but locally up to 3 rows of dissepiments. Pseudocolumella thin and short, when present; in colony UAM-Tc.Can./9 ( Fig. 15D ) not traced. In remaining colonies, interrupted to various extent, absent from long interval of corallite growth in some ( Fig. 15A 2 ). Morphology in longitudinal section depends only in part on presence/absence of pseudocolumella. Shape of tabulae most irregular in colony UAM-Tc. Can./10 irrespective of presence/absence of pseudocolumella ( Fig. 15C 1 , C 2 ). Also, down sloping of peripheral parts of tabulae in that corallite very weakly accentuated. This character most distinctly accentuated in acolumellate part of corallites of colony UAM-Tc.Can./8 ( Fig. 15A 2 , A 3 , arrow), but weak in its columellate part. Same corallite demonstrates differentiated deflection of tabulae from pseudocolumella and their variable density in parts of growth. Deflection of tabulae steepest in colony GSC 142475 ( Fig. 15B 3 ).

Remarks.—Colonies described as Cordilleria sp. differ from all the other specimens of Cordilleria gen. nov. described above, i.e., C. mutabile , C. aff. mutabile , C.oculinum and C. aff. oculinum by having larger numbers of septa and corallite diameters. Three of those colonies ( Fig. 15A 1 , B, D) differ from them in possessing wider dissepimentaria, comprising 2–4 rows of interseptal dissepiments. The dissepimentarium in corallites of colony UAM-Tc.Can./10, comprising 1–3 rows of dissepiments in most, absent from some part of corallites, is intermediate between three colonies described here and the other species of Cordilleria gen. nov. described above. Other characters, except for those in some longitudinal sections (e.g., Fig. 15B 3 , C 1 , C 2 ) are comparable. All four colonies resemble specimens of “ Lithostrotion whitneyi Meek, 1877 ” of Nelson (1960: pl. 25: 1–4), who pointed out that “a complete redescription of the primary types or topotypes is desirable” ( Nelson 1960: 124).

Sando (1965) made such a revision starting from a discussion on the authorship of “ Lithostrotion whitneyi ”. According to him, White’s authorship has priority over the paper by Meek (1877) due to White’s (1875) preprint of his report, published eventually in White (1877). We accept Sando’s reasoning in that matter, but we do not follow Sando’s (1965: E15) identification of that species as belonging to Orygmophyllum Fomichev, 1953 . The latter genus has nothing in common with the colony of “ Lithostrotion whitneyi ”, catalogue number USNM 8480, selected by Sando (1965: E15, pl. 5: 1–9) as the lectotype of that species. First of all, the Ukrainian genus has a solitary growth form. Secondly, its morphology ( Fomichev 1953: pl. 18: 2–14; pl. 19: 1, 2), discussed recently by Fedorowski (2019), differs considerably from that in “ L. whitneyi ”, pointing towards the family Neokoninckophyllidae Fomichev, 1953 , as Fedorowski (2019) documented. Sando (1965) did not study the offsetting and the septal microstructure in the lectotype and we did not restudy that colony. However, its morphology closely resembles that of Heintzella Fedorowski, 1967 , into which it should probably be transferred. With all the mistakes and doubts, the colonies resembling those identified as Cordilleria sp. require a new species name supported by a thoroughly studied and well documented holotype. None of the colonies studied here can serve as such a type. Besides, the restricted number of specimens are inadequate for establishing the intraspecific variation of such a new species. It may be considerable as suggested by the variability of the colonies described here. Thus, the introduction of a new species is not proposed.

Figures

Fig. 12. Variation in septal number and corallite diameters in colonies of rugose coral Cordilleria aff. oculinum (Sando, 1963) and holotypes of Cordilleria oculina (Sando, 1963) and Cordilleria warreni (Nelson, 1960) added for comparison. Data for C. oculina after Sando (1963: part of fig. 1); for C. warreni after Nelson (1960: pl. 24: 11).

Fig. 13. Rugose coral Cordilleria aff. oculinum (Sando, 1963), from Meilleur Member, Flett Formation (Mississipian), Rundle Group, Liard Basin, Northwest Territories, Canada (A, C, F), Tlogotsho Member, Tlett Formation (Mississippian), Rundle Group, Liard Basin, Northwest Territories, Canada B, D), and upper Prophet Formation (Mississippian), Roundle Group, Northwest Territories, Canada (E). A. C-52268 = GSC-142473, locality 2 (Fig. 2); transverse thin section (A1), longitudinal thin section (A2). B. IG-16 = UAM-Tc.Can./5 B-D, locality 3 (Fig. 2); longitudinal section, peel (B1), transverse thin section (B2). C. IG-85 = UAM-Tc.Can./6, locality 3 (Fig. 2); longitudinal section (peel). D. IG-30 = UAM-Tc.Can./7, locality 3 (Fig. 2); longitudinal section, peel (D1), transverse thin section (D2). E. C-52205 = GSC-142472, locality 2 (Fig. 2); transverse thin section. F. C-52361 = GSC-142474, locality 13 (Fig. 2); transverse thin section.

Fig. 6. Stratigraphic column of type section of Viséan Flett Formation at Jackfish Gap on Yohin Ridge, eastern Cordillera, southwest corner of Northwest Territories. Shows lithostratigraphic positions of coral collections discussed in this paper.Abbreviations: Fm., Formation. Stratigraphic column modified from Richards et al. (1989: fig. 24).

Fig. 1. Map showing location of study area, Carboniferous lithofacies assemblages subcropping beneath Permian and Mesozoic deposits in the Western Canada Sedimentary Basin, principal sub-basins, uplifts, and shelves. In the Liard Basin western occurrences of the Rundle and Matson lithofacies assemblages overlie and pass westwards into the Besa River lithofacies assemblage. See Fig. 3 for the formational composition of the Banff, Rundle, and Mattson lithofacies assemblages. Modified from Richards et al. (1994).

Fig. 2. Simplified geological map of study region showing distribution of outcrops of Carboniferous Prophet, Flett, and Mattson formations in southwest corner of Northwest Territories and southeastYukon Territory and lines of cross-sectionA–A’ and B–B’ (see Figs.4, 5 for details). Surface and subsurface sections (corallocalities are in orange):1,Twisted Mountain;2, north end Mattson anticline;3, Jackfish Gap (main coral locality); 4, Tlogotsho Plateau;5, Etanda Lakes; 6, Tika Creek; 7, Pan American Home Signal C.S.P. Celibeta Number 7; 8, Texaco N.F.A. Bovie Lake J-72; 9, Pan American A-1 Pointed Mountain P-53; 10, Canada Southern et al. North Beaver River YT 1-27; 11, Pan American Beaver YT G-01; 12, West Flett anticline; 13, Southern Liard Range; 14, Sheaf Cree.Abbreviations:Fm., Formation (formal unit); fm., formation (informal unit); fms.,formations; S., south; W., west;YT,Yukon Territory;C.S.P., Canada Southern Petroleum. Modified from Harker (1963) and an unpublished map by Andrew Okulitch from 2005 (reproduced with permission).

Fig. 14. Variation in septal number and corallite diameters of rugose coral Cordilleria sp.

Fig. 15. Rugose corals Cordilleria sp. A. IG-82 = UAM-Tc.Can./8, locality 3 (Fig. 2), from Meilleur Member, Flett Formation (Mississipian), Rundle Group, Liard Basin, Northwest Territories, Northwest Territories, Canada; transverse thin section (A1); longitudinal thin sections (A2, A3), weakly accentuated down sloping of peripheral part of tabulae (arrow). B. C-47942 = GSC-142475, locality 14 (Fig.2), from Flett Formation undivided, Rundle Group, Liard Basin, Northwest Territories, British Columbia, Canada; transverse section (B1, B2), longitudinal section, peel (B3). C. IG-18 = UAM-Tc.Can./10, locality 3 (Fig. 2), from Tlogotsho Member, Flett Formation (Mississipian), Rundle Group, Liard Basin, Northwest Territories, British Columbia, Canada; longitudinal thin sections (C1, C2), transverse thin section (C3). D. IG-83 = UAM-Tc.Can./9, locality 3 (Fig. 2), from Meilleur Member, Flett Formation Mississipian), Rundle Group, Liard Basin, Northwest Territories, Canada; transverse thin section.

Fig. 3. A. Partly schematic, palinspastic stratigraphic cross-sectionA–A’ showing stratigraphic relationships of Flett Formation in eastern Cordillera of northern part of project area in southwest corner of Northwest Territories and southeast Yukon. B. Environments of deposition. See Fig. 2 for line of cross-section A–A’.Abbreviations:Fm., Formation (formal unit); fm., formation (informal unit); Mbr., Member (formal unit). Modified from Richards et al. (1989).