Cantabriastraea nov., 2003

Schröder, Stefan & Soto, Francisco, 2003, Lower Devonian (Emsian) rugose corals from the Cantabrian Mountains, northern Spain, Acta Palaeontologica Polonica 48 (4), pp. 547-558 : 552-553

Genus Cantabriastraea nov.

Type species: Cantabriastraea cantabrica .

Diagnosis.—Astreoid to thamnasterioid genus of the Paradisphyllinae with everted calice and smooth to heavily carinate septa. Septa typically dilated (occasionally spindle−shaped) in the inner dissepimentarium. Carinae irregular, with development of retiform septa towards their peripheral part. Tabulae usually complete and arched.

Remarks.—Someprotocorallitesof C. cantabrica havingonly slightly thickened and weakly carinate septa ( Fig. 8H) bear a strong resemblance to species of the genus Cyathophyllum Goldfuss, 1826 (sensu Birenheide 1963) and are reminiscent especially of the recently described Platysmatophyllum Pedder,1998,whichisknownfromtheLowerDevonian(Emsian, nothoperbonus zone)ofCabriéres/Montagne Noire. Although the generic description of Platysmatophyllum is based on two specimensonly itisregarded asa solitary taxon ofthe Cyathophyllidae characterized by lateralbudding and everted calices. Indeed, septa are very thin even in the inner dissepimentarium ( Pedder 1998: fig. 8) and their general morphology is closely similar to Cyathophyllum . According to that author, the slightly withdrawn major septa and consequently more complete tabulae in the type species, P. halleri Pedder, 1998 , are sufficient for separating the genus from Cyathophyllum . But suchamorphologyisnotunusualinspeciesof Cyathophyllum known from the Eifelian of the Eifel, as in C. spongiosum ( Schulz 1883) . Cantabriastraea displays some characters typical of the Cyathophyllidae , like the very thin septa which are carinate and strongly retiform towards the periphery ( Fig. 8J). However, as septa within the inner part or the dissepimentarium are generally affected by trabecular thickenings ( Fig. 9C )andsometimesbyadditionalstereome,indicatingacoarse trabecular structure we regard it as a disphyllid and assign it tentatively to the Paradisphyllinae.

Superficially the new genus also shows some characters diagnostic of Kuangxiastraea Yu and Kuang, 1983 . Growth form of both genera is thamnasterioid−astreoid and there are strongly carinate septa with a tendency to retiform degeneration at the periphery, which has been clearly refigured recently in specimens of the type species K. elegans from the Upper Givetian of Guangxi ( Yu 1997: pl. 1: 3). Kuangxiastraea differs from Cantabriastraea by its more consistently carinate septa, which are predominantly composed of yardarm carinae. Even if the septa are strongly thickened the carinae are always typically developed as yardarm carinae and zigzag carinae are very rare. Although Cantabriastraea is likewise characterized by peripherally retiform septa, its septa bear almost exclusively zigzag carinae. Another difference are the strongly everted calices, causing an arrangement of dissepiment layers in strongly arched series, which is followed by the trabeculae ( Fig. 9A ). Tabulae are usually complete and arched. The tabularium of Kuangxiastraea is composed of incomplete, strongly arched tabellae but the solid axial column/plate consisting of joined distal ends of major septa as observed in the type species by Yu (1997: 270) is most probably not a true axial structure. Another aspect is the difference in the stratigraphic distribution of both genera: whereas Cantabriastraea is only known from the Lower Devonian, Kuangxiastraea and related genera are widely distributed in upper Givetian and lower Frasnian strata. The Eifelian records of the genus ( He 1978) are questioned by Yu (1997: 267) who regards Kuangxiastraea as a (regional) index fossil for the Upper Givetian. Several specimens described from the upper Givetian of western Europe and Canada support this assumption ( Coen−Aubert 2002; Errenst 1993; Küster 1987). In any case, the two Eifelian species Kuangxiastraea breviseptata (Cao in Cao and Lin 1982) and “ H. filata ” sensu He, 1978 non Schlotheim differ strongly from the new species.

Hillastraea Brownlaw and Jell, 1997 from the Frasnian of NW Australia (Lennard Shelf) was proposed for solitary and thamnasterioid corals with slightly everted calices and strongly naotic septa with presumably compound trabeculae, that appear to be extremely thickened. Tabularium of the type species H. floriforme ( Hill, 1936) is composed of small, slightly convex tabellae. The classification of Keriophylloides Soshkina, 1951 isstillunresolved asthetrabecular structure of its type−species K. astreiforme ( Soshkina, 1936) from the Eifelian of the Ural Mtns. is insufficiently known. The species is also characterized by everted calices and strongly carinate/vesiculate (vepreculate?) septa ( Soshkina 1936: 62, figs. 71, 72). However, some authors have discussed a possible development of horseshoe−dissepiments in the type specimen and the genus is currently regarded as a phillipsastreid ( Hill 1981: F282, Brownlaw and Jell 1997: 333) and questionable synonym of the Australian genus Bensonastraea Pedder, 1966 . The only other known thamnasterioid−astreoid genus within the Paradisphyllinae is Radiastraea Stumm, 1937 , which occurs in the Lower Devonian of North America and Australia. It is distinguished from Cantabriastraea by having a differently structured tabularium, with a weakly developed axial structure and generally complete septa.

Occurrence.—Lower Devonian (Emsian) of the Cantabrian Mountains ( Spain).

Figures

Fig. 9. A. Cantabriastraea cantabrica gen. et sp. nov., specimen DPO 14789. A1. Cross sec− tion of tabularium and inner dissepimentarium. Trabeculae are oriented perpendicular to the rows of dissepiments; × 15. A2. Detail of A1; trabeculae intercalate between existing ones or bifurcate; × 20. A3. Septa in cross section with strong dilations in inner dissepimentarium caused by thickening of trabeculae. Towards the periphery (left side) septa become irregular carinate and may split into discrete trabeculae; × 24. B, C. Tabulophyllum bonarense sp. nov. B. Wall of corallite DPO 14673 in cross sec− tion. Thickenings of wall and lonsdaleoid dis− sepiments show a fibrous structure caused by thickened septal bases; × 24. C. Thin septa of corallite DPO 14686 (compare with Fig. 4G) inserting on lonsdaleoid dissepiments (dark lines in lower part of picture). Central part to− wards the axis (top of picture) is strongly af− fected by cement; × 24. All specimens from the Upper Emsian of Colle.