Stellaphyllia luciensis, Fernández-Martínez & Tourneur & López-Alcántara, 2003

Fernández-Martínez, Esperanza, Tourneur, Francis & López-Alcántara, Antonio, 2003, A new Middle Devonian heterocoral from Spain, Acta Palaeontologica Polonica 48 (4), pp. 531-546 : 534

Stellaphyllia luciensis gen. et sp. nov. Fernández−Martínez and Tourneur

Figs. 3–10. Table 1.

Derivation of the name: With reference to the Santa Lucia Formation, from where the material originates.

Holotype: Specimen DPO 15440−11 (Figs. 3,4 R,9F).

Paratypes: Specimens DPO 15440−4 (Figs. 3,4N,9D),DPO 15440−5 (Figs. 3,4H,9B),DPO 15442−23 (Figs. 3,4K),DPO 15442−40 ( Figs. 3, 4D , 8C ) (transverse sections) and DPO 15443−16 (longitudinal section). Type locality: Geras de Gordón (west of La Pola De Gordón , Bernesga Valley,southern slope of the Cantabrian Zone,in NW Spain) ( Fig. 1 ). Type horizon: A brown clayey bryozoan packstone. It is placed about 4 meters below the top of the formation ( Fig. 2 ) .

Material.—Four thin sections (DPO 15440 to 15443),com − prising a total of 44 corallite sections,of which 20 are trans − verse,21 vary from being slightly to highly oblique and three are longitudinal. One ultra−thin section (DPO 15444) contains several corallites.

Diagnosis.—Cylindrical coralla,from one to two millime − ters in diameter,with four to six,more unusually seven,septa joined axially by an oblique septum. In young specimens and in the sections made very near the top of the mature coralla, only septal thickenings are present,and the outer profile is stellate. In mature specimens,very thick tabulothecal walls are developed.

Methods.—Due to the scarcity of material,it has not been possible to carry out work on ontogenesis with acetate peels and all the specimens described in this paper have been identified through the study of thin sections alone.

In spite of the limited data available,a quantitative study has been carried out which presents observations on transverse or slightly tangential sections only (longitudinal and strongly oblique profiles were omitted from the study) corresponding to three elements:

(1) Corallite diameter. Because the irregular profile of some sections,the diameter was measured along the minimum (not medium) transverse dimension of the corallite.

(2) Septal number. The different proposed models of septogenesis result in several different methods for measuring septal number. In this study,it was determined by counting the number of septa intersecting the external wall in the cross section of a corallite.

(3) The outer profile of the studied cross sections.

Using the data obtained from the measurements of these three features it was possible to perform a simple statistical analysis,which demonstrates the relationships between each pair of features ( Table 1 and Fig. 3).

Figures

Fig. 4. Schematic drawings of some of the sections studied,grouped according to the number of septa. Note the different sizes and outlines that can be f ound within each group. In the drawings,the septa can be distinguished by their dark midlines. Upper part (four septa): Specimens DPO 15442−33 (A),DPO 15442−41 (B),DPO 15440−8 (C),DPO 15442−40,paratype (D),DPO 15442−28 (E),and DPO 15442−31 (F). Middle part (five septa): Specimens DPO 15440−12 (G),DPO 15440−5,paratype (H),DPO 15442−24 (I),DPO 15442−32 (J),DPO 15442−23,paratype (K),15442−38 (L). Lower part (six septa): Specimens DPO 15442−27 (M),DPO 15440−4,paratype (N),DPO 15442−37 (O),DPO 15442−34 (P),DPO 15442−27 (Q),and DPO 15440−11,holotype (R).

Fig. 8. Stellaphyllia luciensis gen. et sp. nov. Morphology. A. General view of a fragment of the thin section DPO 15440 containing two cross sections of heterocorals (white arrows),the holotype is marked with two arrows; × 4.5. B. Transverse section of DPO 15442−28,with four septa and a profile in the pro − cess of rounding−off. C. Transverse section of DPO 15442−40,with 4 septa and a rounded outline. D. Transverse section of DPO 15442−37,with four septa. Note that one of the septa is in the beginning of a bifurcation. E. Transverse section of DPO 15442−25. Note the stellate profile of the section and the presence of four septa,two of which are bifurcated. F. Specimen DPO 15442−38. Transverse section with five septa and a stellate profile. G. Transverse section of DPO 15442−32,with five septa and a slightly rounded profile. H. Specimen DPO 15442−24. Transverse section of a corallum with five septa and a markedly rounded outline.

Fig. 1. Geographic and geologic setting of the sample location. A. Simplified geology map of Cantabrian Mountains,NW Spain showing position of studied area. AO−L Zone indicates Westerasturian−leonese Zone (“Zona AsturOccidental−leonesa”) and the rest of the figure belong to the Cantabrian Zone B. Detailed location of the outcrop.

Fig. 2. Stratigraphic column of the Santa Lucia Formation,near Geras de Gordón (the lowest part of this formation is lacking in this section). The sample with heterocorals was taken from the bed marked with a star. Modified from Tourneur et al. (1995).