Thamnasteria cf. mettensis Milne Edwards & Haime, 1851

Vasseur, Raphaël & Lathuilière, Bernard, 2021, Pliensbachian corals from the Western Tethys, Geodiversitas 43 (22), pp. 1187-1291 : 1274

Thamnasteria cf. mettensis Milne Edwards & Haime, 1851

( Fig. 60 )

Thamnasteria mettensis Milne Edwards & Haime, 1851: 141 , pl. 30, fig. 3. — Lathuilière 2000b: 161, fig. 13.4, 13.6, 13.9, 18, 19 cum syn. — Pandey & Fürsich 2003: 75 pl. 20 fig. 3, pl. 21 fig. 1, 4-6.

Thamnasteria aff. mettensis – Pandey & Fürsich 2003: 76, pl. 22, fig.3.

Thamnasteria sp. 1 – Vasseur 2018: 344-345, fig. 3.96.

Thamnasteria sp. – Brame et al. 2019: fig. 7J-K.

TYPE MATERIAL. — Syntype lost. TYPE HORIZON. — Bajocian. TYPE LOCALITY. — Saint Quentin, near Metz ( France) and Crickley ( Great Britain). STUDIED SAMPLES. — Two specimens: CPUN DA2705E5-1 and CPUN DA2805E6-1. GEOGRAPHIC AND STRATIGRAPHIC RANGES. — Pliensbachian of Ziz valley ( High Atlas of Morocco).

DESCRIPTION

Massive thamnasterioid corallum without epitheca (14 to 38 mm in size). Radial elements are subcompact (upward) to compact (in depth), septa or biseptal sheets sometimes anastomosed and often sinuous. Distal edge with regular small teeth, which diameter decrease from the periphery to the center of the calice. These teeth are often well detached at the distal-inner edge. False pennulae small, in the form of horizontally flattened dentate expansions never turned upward and not alternating or corresponding from a septum to the neighbouring one or from one side to the other of a single septum. Acute granules also present on lateral faces. Styliform columella in depth. Endotheca present, made of numerous dissepiments. Synapticulae abundant, wall absent.

Calicular diameter: 3.5 to 6 mm – Distance between calices: 3.5 to 6 mm – Number of septa: 20 to 30 – Septal density: 6 to 7 for 2 mm.

REMARKS

According to Lathuilière (2000b), the dimensions of the present species range within the species Thamnasteria mettensis , the only species of the genus for which a population study is available. However they are situated in the upper part of the spectrum with regards to the distance between calices. Moreover we identified the species with a cf. due to the absence of holotheca, an unusual character in the Bajocian T. mettensis . Since its creation in 1823 the genus Thamnasteria includes 165 nominal species that obviously need a thorough revision. We refer here to T. mettensis because it is well known in terms of variability and it is the closest species in terms of stratigraphy. The revision of common Upper Jurassic species ( T. dendroidea Lamouroux, 1821 , T. gracilis Goldfuss, 1829 and T. concinna Goldfuss, 1826 among others) could lead to a synonymy of T. mettensis Milne Edwards & Haime, 1851 .

Figures

FIG. 60. — Thamnasteria cf. mettensis Milne Edwards & Haime, 1851: A, distal view of the specimen CPUN DA2705E5-1; B, transverse thin section of the specimen CPUN DA2805E6-1; C, detail of septal structure in transverse section of the specimen CPUN DA2805E6-1;D, transverse thin section of the specimen CPUN DA2705E5-1; E, transverse thin section of the specimen CPUN DA2805E6-1. Scale bars: A, C, D, 2 mm; B, E, 4 mm.