Conochitina, EISENACK, 1931 emend. PARIS, GRAHN, NESTOR et LAKOVA, 1999

Morávek, Radek, 2009, Lower Wenlock Chitinozoa From The Bykoš Locality (Silurian, Prague Basin, Barrandian Area, Czech Republic), Acta Musei Nationalis Pragae Series B 65 (1 - 2), pp. 37-60 : 42-43

Conochitina proboscifera EISENACK, 1937

Pl. 5, figs. 8-11; pl. 9, figs. 5-7, 15.

1937 Conochitina proboscifera EISENACK, p. 225, pl. 15, figs. 4-5.

1974 Conochitina proboscifera EISENACK, Laufeld, p. 70-72, fig. 32 A-D.

1982 Conochitina proboscifera EISENACK, Verniers, p. 35-36, pl. 1, figs. 1-17.

1985 Conochitina proboscifera EISENACK Grahn, p. 160, pl. 1, figs. 12-13.

1990 Conochitina proboscifera EISENACK, Dufka, p. 68, pl. 39, figs. 8-16.

1993 Conochitina proboscifera EISENACK, Nestor, pl. 2, fig. 13- 14.

1994 Conochitina proboscifera EISENACK, Nestor, p. 36, pl. 18, figs. 1-3.

1995 Conochitina proboscifera EISENACK, Grahn, figs. 7 C-D.

2002 Conochitina proboscifera EISENACK, Nestor et Nestor, pl. 1, fig. 12

2004 Conochitina proboscifera EISENACK, Mullins et Aldridge, p. 758-762, pl. 3, fig. 13, pl. 6, figs. 3-14, pl. 7, figs. 10-12, pl. 8, figs. 1-2, 5, 7, 12.

2005 Conochitina proboscifera EISENACK, Nestor, pl. 1, figs. 8- 9.

D e s c r i p t i o n: Tubular vesicle with a hardly distinguishable neck. The neck is tubular or flared at the apertural pole. The chamber may be conical. The flanks are straight or slightly convex. The basal edge is rounded and the base is flat to convex with a tiny mucron. The mucron can be sunken and is then invisible. Ratio of maximal diamater to the length of vesicle is greater than 1:5 but less than 1:9.

D i s c u s s i o n: The shape of Conochitina proboscifera sometimes resembles C. proboscifera f. truncata. The differentiation is made on the basis of the ratio of diameter and length of the vesicle.

O c c u r r e n c e: Lower Silurian of the Prague Basin ( Dufka, 1990): Sheinwoodian (zones: C. murchisoni, M. riccartonensis and C. rigidus) .

Hughley Brook section, Hughley, Shropshire ( GSSP for the base of the Wenlock; Mullins et Aldridge, 2004), UK: C. proboscifera is distributed throughout unit G of the Buildways Formation .

Gotland ( Laufeld, 1974): From the lower Visby Beds to the top of the Högklint Beds (upper Telychian to the middle Sheinwoodian).

Mehaigne area (Brabant Massif, Belgium; Verniers, 1981, 1982): From the Formation MB2A to the Formation MB5, Llandovery to early Wenlock.

Southern Ohio ( Grahn, 1985): Estill Shale (zones: M. crenulata to C. centrifugus).

Jaagarahu Core, Estonia ( Nestor, 1993): Velisa Formation of the Adavere Stage (Llandovery) to the Mustjala Member of the Jaani Stage (Wenlock).

Estonia and North Latvia ( Nestor, 1994): Adavere Stage to the Jaani stage, chitinozoan biozone 10 (middle Telychi- an), 12 and 13 (lower Sheinwoodian).

Subsurface of Gotland ( Grahn, 1995): from the Aeronian (zone M. sedgwickii) to the lower Sheinwoodian (zone C. murchisoni).

Southwestern Estonia ( Nestor et Nestor, 2002): Staicele ( Estonia) drill core: middle part of Tõlla Member, chitinozoan biozone number 4.

West Estonian drill cores – Margachitina margaritana Biozone ( Nestor, 2005): C. proboscifera appears in all four sampled cores through the Llandovery-Wenlock boundary.

Conochitina proboscifera EISENACK, 1937 forma truncata LAUFELD, 1974

Pl. 5, figs. 1-7; pl. 9, figs. 1-4.

1974 Conochitina proboscifera EISENACK forma truncata LAUFELD, p. 72, figs. 34D - E.

1981 Conochitina proboscifera EISENACK forma truncata LAUFELD, Paris, p. 184-185, pl. 19, figs. 4, 7.

1982 Conochitina proboscifera EISENACK forma truncata LAUFELD, Verniers, p. 35, pl. 1, figs. 3-9.

1990 Conochitina proboscifera EISENACK forma truncata LAUFELD, Dufka, p. 70, pl. 40, figs. 3-4.

1995 Conochitina proboscifera EISENACK forma truncata LAUFELD, Grahn, fig. 7F.

D e s c r i p t i o n: Tubular to subtubular vesicle. The neck is tubular, sometimes tapering in the apertural pole. Flexure inconspicuous. The flanks are straight and parallel or convex. The shoulders can be well developed. Flat to convex base and with basal edge bluntly rounded. The mucron is wide. Ratio of the maximal diamater to length is from 1:4 to 1:5.

D i s c u s s i o n: Vesicles from the Bykoš locality are very similar to the specimens depicted in Laufeld (1974).

O c c u r r e n c e: Lower Silurian of the Prague Basin ( Dufka, 1990): Sheinwoodian (zones:? C. murchisoni and C. riccartonensis) .

Gotland ( Laufeld, 1974): From the upper Visby Beds to the top of the Slite Marl (lower to the middle Sheinwoodian).

Coupé du Rocher and coupé de la Lande-Murée, France ( Paris, 1981): zone M. turriculatus (upper Llandovery).

Mehaigne area (Brabant Massif, Belgium; Verniers, 1981, 1982): see occurence of C. proboscifera.

Subsurface of Gotland ( Grahn, 1995): from the upper Telychi- an (zone M. spiralis) to the Sheinwoodian (zone M. belophorus).

Conochitina proboscifera EISENACK, 1937 forma gracilis LAUFELD, 1974

Pl. 9, figs. 8-10.

1974 Conochitina proboscifera EISENACK forma gracilis LAUFELD, p. 72, figs. 34 A-C.

1990 Conochitina proboscifera forma gracilis EISENACK forma gracilis LAUFELD, Dufka, p. 71, pl. 40, figs. 5-9.

1995 Conochitina proboscifera EISENACK forma gracilis LAUFELD, Grahn, fig. 7E.

D e s c r i p t i o n: Very rarely found specimens with extreme ratio of maximal width to length of vesicles – more than 1:8. Tubular to subtubular vesicle. The neck is not diferentiated from the chamber and is tapering in the apertural pole. The base is convex and the basal edge is round- ed. The mucron is wide if at all visible.

D i s c u s s i o n: This species can be differentiated from C. proboscifera by its greater length to diameter ratio.

O c c u r r e n c e: Lower Silurian of the Prague Basin ( Dufka, 1990): Upper Sheinwoodian (zones: C. perneri and C. ramosus) .

Gotland ( Laufeld, 1974): From the upper Visby Beds to the lowermost Högklint Beds (lower Sheinwoodian).

Mehaigne area (Brabant Massif, Belgium; Verniers, 1981, 1982): see occurence of C. proboscifera.

Subsurface of Gotland ( Grahn, 1995): from the upper Telychian (zone M. spiralis) to the Sheinwoodian (M. riccartonensis).