Tabulophyllum bonarense, Schröder & Soto, 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 : 549-550

Tabulophyllum bonarense sp. nov.

Figs. 3A–D , 4A–I , 5A–D , 9D, E .

Holotype: DPO 14670 ( Fig. 4A, B ).

Type locality: Colle , ca. 5 km SE of Boñar, Province León , Hoja 104 (Boñar), 1°33’37’’E / 42°50’42’’N .

Type horizon: Lower Devonian, Emsian, La Vid−Group, brown shales in the lower part of the Coladilla Formation [Col A−13−B−1].

Derivation of the name: After the village Boñar, Province of Leon.

Paratypes: 17 specimens, DPO 14671–14688.

Diagnosis.—Small solitary corals or “quasi−colonies” with a corallite diameter of 12–15 mm and 18–21 short major septa. Septa peripherally commonly interrupted by lonsdaleoid dissepiments. Minor septa are rudimentary and frequently reduced to spines on wall or dissepiments. Narrow dissepimentarium, of 1–2 rows of elongate dissepiments.

Description.—The fragments of corallites are cylindrical, withamaximum length of5cmand adiameter of 12–15 mm. Some specimens ( Figs. 3B , 5A, D ) show preserved offsets developed by lateral increase and some isolated fragments with small diameter (8 mm) should probably be regarded as fragments of such offsets. Preserved calices are shallow funnel shaped ( Fig.3C ). Fragments are generally long and cylindrical, and only a few specimens are slightly curved. Rejuvenescence occurs very often and is easily recognized because the expansions of lonsdaleoid dissepiments usually show a sharp boundary ( Fig. 3D ). Commonly rejuvenescence occurs together with minor shifting of the growth axis. In places structures similar to connecting processes are developed by periodical expansion of lonsdaleoid dissepiments ( Figs. 3A , 4I ), which usually are only preserved as short spines with thin, irregularly spaced transverse partitions ( Fig. 5C ). If complete, those structures are blind−ending hollow tubes ( Fig. 4I top left, 4C left corallite) and a presumed function as connecting tubulae in contact with possible neighbouring corallites is not definite. In addition to very fine rugae, the wall sometimes shows widely spaced stronger folds, but there is no obvious cyclicity.

Corallite walls are slightly thickened, 0.3– 1 mm wide and show a structure of “fibrous crystallites” ( Fig. 9D ) comparable to the structure of the septotheca observed in Tabulophyllum species by Sorauf (1997: 232, fig. 4.2, pl. 1: 7; 1998: 34). If septa are inserted at the wall additional thickenings are possible because of thickened septal bases, but depending on the common development of the lonsdaleoid dissepiments septa are usually interrupted by thin but elongate presepiments which are arranged in up to three rows ( Fig. 9E ). The innermost row may be of globose shaped dissepiments. In juvenile corallites or offsets septa are usually inserted at the wall and lonsdaleoid dissepiments are not developed in this stage ( Fig. 5D ). Major septa range in number from 18–21, but it is impossible to count them correctly in some cross sections in which septa are rudimentary and only recognizeable as short spines extending 1–2 mm into the corallite. Accordingly, there isalways a large axial space free of septa, which measures up to 7 mm and is traversed by few, mostly thickened sections of tabulae. Although minor septa are usually developed, they are generally very short and reach up to half of the length of major septa.

Longitudinal sections are simply structured and show a small lonsdaleoid dissepimentarium and a tabularium which is 6–10 mm wide and contains mainly complete tabulae. Tabulae are usually flat, but can be slightly arched. There are 8–10 tabulae/cm corallite−length. Dissepimentarium comprises 1–2, rarely 3 rows of medium sized, elongated, sometimes even sickle−shaped dissepiments. Close to the corallite−wall they are traversed by fine trabeculae, which are weakly inclined.

Remarks.—Although strongly fragmentary, the available material suggests a solitary growth form, with development of rare lateral offsets ( Figs. 3B , 4C : above left corallite, 5A, D) which have not reached maturity. This is important, as a specimen should be defined as colonial only in case if its offsets reach morphological maturity ( Fedorowski 1978). The existence of underdeveloped offsets, which is not related to extrinsic factors, is most probably genetically controlled and such offsets are known as “lost structures” ( Fedorowski 1978). The corresponding corallites are regarded as “quasicolony” as defined by Fagerstrom and Eisele (1966) or as “simple budding forms” (Minato and Rowett 1967). Acom − parable morphology has been well documented for Craterophyllum verticillatum Barbour, 1911 from the Carboniferous of Nebraska and for Permian Heritschioides specimens from New Mexico ( Fedorowski 1978: pl. 23: 9). However, the best preserved corallite of our material does not show lateral budding in verticils consisting of numerous offsets arising at the same time as in C. verticillatum ( Fagerstrom and Eisele 1966: pl. 73: 1, 4), but a more irregular, randomly arrangement ( Fig. 3B ).

T. bonarense is a morphologically very simple form and differs strongly from its rather large and septal−rich Upper Devonian relatives. Accordingly, there are only a few species of Tabulophyllum which may be compared to T. bonarense sp. nov., but generally occur in much younger strata. A closely related species seems to be Tabulophyllum manifestum Spasskiy, 1971 (in Dubatolov and Spasskiy 1971) from the Eifelian of the Altai Mountains. This species has also short major septa which are interrupted by lonsdaleoid dissepiments, whereas minor septa are strongly reduced ( Spasskiy 1960: pl. 1: 3, 4, pl. 2: 1–6, pl. 3: 1, 2). It is distinguished from T. bonarense in having a larger corallite diameter, a much higher number of septa and its strong calicinal budding, indicating an incipient coloniality as defined by Fedorowski (1970: 603). Cyathophyllum timanicum Lebedew, 1902 (Frasnian?, Uchta River, Timan) has a higher number of longer, more regularly developed major septa (26–29 SI) and a stronger development of the lonsdaleoid dissepimentarium ( Lebedew 1902: 134, 179, pl. 5: 64–66). However, the classification of some morphologically insufficiently known corals assigned to Tabulophyllum remains questionable. This is the case with Tabulophyllum angulosum Spasskiy, 1971 (inDubatolov and Spasskiy 1971: 106, pl. 38: 1), which has been described form the Givetian of the Dzhungarian Alatau or Calophyllum tchernyschewi Lebedew, 1902 , which is known from the Frasnian of the Timan. Detailed information is lacking on growth form of those species and they are difficult to assign with certainty to Tabulophyllum and may belong to Smithiphyllum .

Figures

Fig. 3. Tabulophyllum bonarense sp. nov., external morphology of corallites. A. CoralliteDPO 14686withincompletelateralprojectionofconnecting process on left side. B. Specimen DPO 14678 with two incomplete lateral offests. C. Corallite DPO 14679 with septa interrupted by lonsdaleoid dissepimentsin distal view (C1). Side view (C2) showing flat base and weak development of talon structures. All × 3. All specimens from the Upper Emsian of Colle.

Fig. 4. Tabulophyllum bonarense sp. nov. A. Holotype DPO 14670 in cross section (A1) and longitudinal section (A2), with narrow dissepimentarium. B. Fragment of corallite DPO 14673 with lateral offsets. Well developed major septa are frequently interrupted by lonsdaleoid dissepiments. C–G. Cross sections of isolated corallites, showing variable development of septa: DPO 14688 (C), DPO 14685 (D), DPO 14672 (E), DPO 14671 (F), DPO 14686 (G). H. Longitudinalsectionwitha“rhizoidprocess”onleftsideofcorallite.All×3, exceptB, whichis×2. AllspecimensfromtheUpperEmsianofColle.

Fig.5. Tabulophyllum bonarense sp.nov. A.CrosssectionDPO14677bwith smalloffsetonleftside;×8.5. B.CrosssectionnofcoralliteDPO14676.Lateral connecting process on left side; × 4. C. Detail of Fig. 4H. DPO 14674. Lateralprojectiondevelopingfromanextensionofalonsdaleoiddissepiment with transverse partitions internally; × 9. D. Lateral offset of corallite DPO 14673; × 8.5. All specimens from the Upper Emsian of Colle.

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.