Sphenothallus kukersianus ( Öpik, 1927 )

Vinn, Olev & Kirsimäe, Kalle, 2015, Alleged cnidarian Sphenothallus in the Late Ordovician of Baltica, its mineral composition and microstructure, Acta Palaeontologica Polonica 60 (4), pp. 1001-1008 : 1003-1004

Sphenothallus kukersianus ( Öpik, 1927)

Fig. 2D .

1927 Serpulites kukersianus ; Öpik 1927: 27, pl. 2: 14.

Material.—One complete specimen TUG 1087-12 from Kohtla-Järve, NE Estonia; Viivikonna Formation, lowermost Sandbian.

Description.—Large flattened slightly curved tube with very thin wall. Distal part of the tube is slightly tapering. Tube grew relatively fast in diameter 1.6 mm per 10 mm of length. Tube wall has two lateral thickenings 180° apart that are 0.4 mm thick. The tube wall between lateral thickenings is 0.15 mm thick. Tube external surface is smooth and glossy, with very fine somewhat irregular perpendicular wrinkles. There are six to seven wrinkles per 5 mm. Tube wall has a lamellar structure.

Dimensions.—Maximal length 8.8 mm, maximal width 13.0 mm

Remarks.— S. kukersianus differs from S. aff. longissimus by its relatively fast growing diameter and tapering distal part of the tube. The tapering distal part of the tube could be caused by lateral compression and is presumably an artifact of preservation. It is possible that the fast growing diameter could also be characteristic of the proximal part of the tube of S. aff. longissimus . However, the studied material did not contain proximal parts of S. aff. longissimus tubes. Thus, S. kukersianus may be a junior synonym of S. aff. longissimus .

Geographic and stratigraphic range.—North East Estonia, oil shale basin, Sandbian.

Sphenothallus aff. longissimus ( Murchison, 1839) Fig. 2A–C .

1927 Serpulites longissimus Murchison, 1839 ; Öpik 1927: 26, pl. 2: 13.

Material.—Twelve partially preserved tubes TUG 1087-11, TUG 1008-25, TUG 1008-26, TUG 1008-27, TUG 1648-2, TUG 1648-3, TUG 1648-4, TUG 2-548, TUG 2-549, TUG 2-550, TUG 2-551, and GIT 494-14; from Kohtla, Kohtla- -Nõmme, Kohtla-Järve, Kiviõli, Ubja from NE Estonia, and Kükita 24 borehole; Viivikonna Formation, lowermost Sandbian to Tudulinna Formation, middle Katian.

Description.—Very large slightly curved and flattened tubes with thin walls. Tubes grew very slowly in diameter 0.3 to 0.7 mm per 10 mm of length. Tube wall has two lateral thickenings 180° apart that are 0.4 to 0.9 mm thick (N = 7, mean = 0.56 mm, sd = 0.18). The tube wall between lateral thickenings is 0.15 mm thick (N = 6, mean = 0.17 mm, sd = 0.04). Tube external surface is smooth and glossy, but some tubes have fine somewhat irregular perpendicular wrinkles. There are about three wrinkles per 5 mm in wrinkled tubes. In addition, irregular wrinkles in various directions and of various magnitudes occur in many tubes. Tube wall has a lamellar structure, both at thickenings and between them.

Dimensions.—Maximal length> 355 mm, maximal width 25 mm (N = 12, mean = 19.3 mm, sd = 4.89)

Remarks.—The studied specimens are affiliated with Serpulites longissimus Murchison, 1839 ( Murchison 1854: 233, pl. 16: 1) from Ludlow of Great Britain due to their very large and slightly curved tubes. Sphenothallus specimens described by Bolton (1994: 2) have somewhat similar shape to S. aff. longissimus , they also show various wrinkles ( Neal and Hannibal 2000: 374–376), but their tubes are much smaller. Another Ordovician species, S. ruedemanni ( Kobayashi 1934: 527, pl. 1: 9–12; Choi et al. 1990: 3, figs. 3, 4), has also somewhat similar wrinkles to some specimens of S. aff. longissimus , but it differs by the much smaller size of the tube. It also has much greater angle of expansion of the tube than S. aff. longissimus .

Figures

Fig. 2. Tubes of Sphenothallus aff. longissimus (A–C) and Sphenothallus kukersianus (Öpik, 1927) (D) Viivikonna Formation, lowermost Sandbian, NE Estonia. A. TUG 73-37 from Kohtla-Järve. B. TUG 1087-14 from Kohtla. C. TUG 2-551 from North East Estonia, oil shale basin. D. TUG 1087-12 from Kohtla-Järve.