Heritschioides simplex, Fedorowski & Bamber & Richards, 2019

Fedorowski, Jerzy, Bamber, E. Wayne & Richards, Barry C., 2019, Bashkirian rugose corals from the Carboniferous Mattson Formation in the Liard Basin, northwest Canada - stratigraphic and paleobiogeographic implications, Acta Palaeontologica Polonica 64 (4), pp. 851-870 : 863-867

publication ID	https://doi.org/ 10.4202/app.00636.2019
persistent identifier	https://treatment.plazi.org/id/3B6D8103-F366-FFE9-7F5E-1F64DB472401
treatment provided by	Felipe
scientific name	Heritschioides simplex
status	sp. nov.

Treatment

Heritschioides simplex sp. nov.

Figs. 7B View Fig , 8 View Fig , 9 View Fig .

ZooBank LSID: urn:lsid:zoobank.org:act:3E992402-6358-49F2-8644-6ED18C91AC1D

Etymology: From Latin simplex , simple; after simplified morphology. Holotype: GSC 140526, one fragment of worn colony.

Type locality: GSC locality C-442050, Mattson Gap section 20RAH9, Northwestern Territories, Canada .

Type horizon: Upper member Mattson Fm. between 1056.7 and 1057.1 m above base Mattson Gap section 20RAH9 (1021.64 to 1022.04 m above base Mattson Fm. and 401.03 to 401.43 m above base upper member); Foraminiferal Biozone 20 of Mamet and Ross in Bamber and Waterhouse (1971).

Material.— Holotype, colony measuring approximately 9 × 11 × 15 cm. Corallites partly silicified, some compressed to a variable extent. Six thin sections available for study.

Diagnosis.— Heritschioides with n:d value variable; maximum septal number 29 × 2, maximum corallite diameter 23 × 18.5 mm; major septa stop short of simple axial structure with long thin median lamella; extra septal lamellae either absent or very restricted in number; most minor septa restricted to dissepimentarium, which occupies approximately ¼ corallite radius; cardinal fossula distinct, bordered by two parallel major septa.

Description.—Corallites loosely and irregularly arranged; twins occur ( Fig. 8A 8 View Fig , arrow) external walls of corallites thin. Septa attached to wall rather than penetrate it ( Fig. 8A View Fig 4 View Fig , A 5 View Fig ). Major septa thin in dissepimentarium, strongly wavy, rarely interrupted by small lonsdaleoid dissepiments ( Fig. 8A View Fig 4 View Fig ), their tabularial sectors slightly dilated, mostly next to slightly thickened inner wall; they thin gently toward axis, most major septa withdrawn from axial structure, rarely temporarily united with corresponding lamellae, in part of one corallite major septa “doubled” ( Fig. 9A View Fig 2 View Fig , A 5 View Fig ), with additional septal blades present in tabularium not corresponding to minor septa, their occurrence and function doubtful. Minor septa closely resemble peripheral sectors of major septa in morphology, most restricted to dissepimentarium, rarely cross it slightly. Cardinal septum shortened, but may be met or closely approached by elongated, thin extension of median lamella ( Fig. 8A View Fig 3, A 2, respectively). Counter septum equal in length and thickness to adjacent major septa in most corallites, may be slightly elongated ( Fig. 8A View Fig 1 View Fig , A 2 View Fig ). Cardinal fossula shallow, but distinct; bordered by two major septa commonly equal to remaining ones in length and thickness ( Figs. 8A View Fig 1 –A View Fig 3, 9A 2). Axial structure variable in morphology, commonly simple, consisting of long, thin median lamella, several septal lamellae and numerous axial tabellae; arrangement, length and number of septal lamellae and sections of axial tabellae on either side of median lamella may differ greatly ( Figs. 8A View Fig 2 View Fig , 9A View Fig 2 View Fig ); extra septal lamellae not found, except for problematic one or two in one corallite. Crushing of parts of skeleton precludes firm documentation of axial column in longitudinal section ( Figs. 8A View Fig 6, 9A 1). However, obvious difference in arrangement between incomplete peripheral tabulae, almost semispherical, and axial tabellae elevated steeply towards median lamella, suggest occurrence of isolated axial column. Microstructure of septa finely trabecular as documented both in transverse and longitudinal sections ( Fig. 9A View Fig 3, A 5, respectively), i.e., matches that in H. columbicum ( Smith, 1935) ( Fedorowski et al. 2014b: fig. 7: 4, 7); lack of sclerenchymal sheets in part of septum documents original width of primary septa ( Fig. 9A View Fig 3, arrow). Offsetting lateral ( Fig. 8A View Fig 6), but details in septal insertion unknown; pinnacles seen at parent/offset border ( Fig. 8A View Fig 7 View Fig ) suggest general similarity to offsetting documented in detail by Fedorowski et al. (2014a, b).

Remarks.—In view of the fairly recent revision of Waagenophyllum columbicum Smith, 1935 , the type species of the genus Heritschioides ( Fedorowski et al. 2014a) , supplemented by descriptions of species from Alaska ( Armstrong 1972; Fedorowski et al. 2014b), no discussion is given here of the diagnostic characters of Heritschioides and its taxonomic relationships. Data from the above papers allow both a close comparison of Heritschioides simplex sp. nov. with the known species of that genus and a suggestion of its probable stratigraphic position. The redescription and reillustration of Smith’s (1935) type collection and the study of topotype material ( Fedorowski et al. 2014b: figs. 2: 1–7; 5: 8, 9; 7: 7 and figs. 3: 1–8; 4: 1–5; 5: 1–7, 10, 11; 6: 1–8; 7: 1–6; 8: 1–4) document large intraspecific variability in the type species and thus the possibility of comparison with taxa having both complex and simple morphology. Four? characters in common between the holotype and the paratype of H. columbicum and H. simplex sp. nov. are of special value in the context of the present paper. These are: (i) a very similar trabecular septal microstructure, (ii) a restricted number or absence of extra septal lamellae from the axial structures of mature corallites, and (iii) a comparatively narrow and simple morphology of the dissepimentarium and (iv) similar morphology of the tabularium. Much more complex dissepimentaria and more common occurrence of extra septal lamellae in the topotypes were accepted by Fedorowski et al. (2014a) as intraspecific variants, but they also may be considered as adequate for separation of a new species. The main differences between the simplest specimens of the type species and the specimen described here include different n:d values, (i.e., larger corallite diameter and smaller septal number), much shorter major septa that seldom reach the simple axial structure, and less steeply orientated axial tabellae in the axial column of H. simplex sp. nov.

Heritschioides separatus Fedorowski and Stevens, 2014b , first described by Armstrong (1972) as the paratype of his species Corwenia jagoensis , is another species of simple morphology to consider. That species, which was collected from the Wahoo Limestone (Atokan) in the Brooks Range (Alaska), resembles H. simplex sp. nov. in several features. These include a narrow, simple axial structure with extra septal lamellae absent or very rare, similar morphology of the dissepimentarium and similar n:d values of mature corallites. In comparison with H. simplex sp. nov., H. separatus shows a common reduction of its median lamella, less regularity in the morphology of its axial structure in longitudinal section, a cardinal fossula that is more difficult to recognize in some corallites and a wider dissepimentarium in its largest corallites. Some of those differences are slight, so that these two species are morphologically close to each other.

The similarity of H. simplex sp. nov. to morphologically simplest and stratigraphically lowest species of Heritschioides and its occurrence along with Nemistium liardense ( Fig. 7B View Fig , black arrows) suggest that it is probably not younger than early Bashkirian.

Stratigraphic and geographic range.—The type locality and horizon only.