Flabellulirostrum kielcensis, Baliński, 2006

Baliński, Andrzej, 2006, Brachiopods and their response to the Early-Middle Frasnian biogeochemical perturbations on the South Polish carbonate shelf, Acta Palaeontologica Polonica 51 (4), pp. 647-678 : 656-660

Flabellulirostrum kielcensis sp. nov.

Figs. 8B–D , 9 , 10 .

1988 Flabellulirostrum nov. sp. A; Makowski 1988: 33–36, pl. 13: 1–6, pl. 10: 1–5, text−fig. 13A.

1988 Flabellulirostrum nov. sp. B; Makowski 1988: 36–38, pl. 14: 2, 4, 6 (non 1, 3, 5 = F. rackii sp. nov.), pl. 12: 10, 11 6 (non 9, 12 = F. rackii sp. nov.), text−fig. 13B.

1993 Flabellulirostrum nov. sp. B; Makowski in Racki et al. 1993: 86, pl. 18: 1, 2.

Holotype: Complete shell ZPAL Bp 60/2 ( Fig. 8C ).

Type horizon: Complex C, bed 44, Palmatolepis transitans conodont Zone.

Type locality: Wietrznia Ie quarry, SE part of city of Kielce; GPS coordinates: N 50°51’21.0’’, E 20°38’30.6’’.

Derivation of the name: After Kielce, the name of the city where this new species was found.

Diagnosis.—Shell variable in total dimension, up to 20.5 mm in length, transversally subelliptical to subpentagonal in outline; cardinal margin long, broadly obtuse; ventral flanks gently convex, slope sharply at the margins; dorsal fold distinct, with 4–9 costae; ventral sulcus shallow to deep, with concave to flat bottom, and 3–9 costae. From Flabellulirostrum guerichi ( Baliński, 1979) differs by having wider sulcus and fold and more numerous median costae. F. afrum (Drot, 1997) and F. bergica ( Schmidt, 1975) have more triangular shell outline. F. wolmericus ( Veevers, 1959) and F. morzadeci Brice, 1983 in Brice and Morzadec (1983) have wider shell. From F. rackii sp. nov. differs by having convex flanks and round−edged lateral commissure.

Material.—More than 100 well preserved specimens of complete to nearly complete shells and more than 200 fragmentary specimens from Wietrznia Id−W (beds 4, 5, 14, 18, and 31) and Wietrznia Ie sections (beds 29, 30, 43–45, and 48).

Description.—Shell medium sized to large for genus, dorsibiconvex, subelliptical to subpentagonal in outline, widest at about midvalve or slightly more posteriorly; cardinal margin long, broadly obtuse, lateral margins gently rounded, anterior margin truncated to slightly emarginate, anterior commissure strongly uniplicate; lateral commissure of large shells tapered as a result of slight geniculation of valves edges.

Ventral valve gently convex in lateral profile, gently convex when viewed from the anterior, sometimes with concave middle region; flanks gently convex, slope evenly towards the commissure, then more sharply at the margins; interarea wide, limited by blunt borders, beak slightly incurved; sulcus wide, originating about 6–8 mm anterior to the beak, shallow to moderately deep, with concave to flat bottom; tongue long, gently rounded, strongly bent dorsally.

Dorsal valve much deeper than ventral one, regularly arched in lateral profile, and strongly convex in anterior view with elevated tongue and fold; fold originating at about midvalve, anteriorly high, with rounded top.

Shell posteriorly smooth, noncostate, except for fine, flat, radiating capillae (5–8 per mm) and dense concentric growth lines (about 12 per mm); at about 7 mm from umbo capillae gradually fade away with simultaneous appearance of radial costae; there are about 5–16 costae on each flank, 4–9 (mean 6.2) costae on fold, and 3–9 costae in sulcus; costae are simple, round−top, median ones sometimes are stronger than those on flanks; parietal costae usually absent, exceptionally one barely discernible parietal costae may be seen but it does not reach anterior margin.

Interior of ventral valve ( Fig. 9 ) without dental plates but with thickened umbonal region. Dorsal valve interior ( Fig. 9 ) with high, rather thin median septum supporting short, horizontal hinge plates; cardinal process distinct; crura closely set, short, delicate, ventrally curved.

Intraspecific variability.— Flabellulirostrum kielcensis sp. nov. occurs in Wietrznia Id−W and Wietrznia Ie sections. The occurrence of the species in the former section were studied in details by Makowski (1988; Racki et al. 1993). He discriminated in his material two species of Flabellulirostrum , namely Flabellulirostrum sp. A , smaller form which occurs in the older stratigraphic horizon (beds 4 and 5), and Flabellulirostrum sp. B , which was recovered by him in higher beds (14 and 18). There is no doubt that the younger form is evidently greater that the older, whereas all other shell characters seem to be virtually identical (compare with Fig. 10A, B where smaller and greater shells form two clusters). This difference in the shell dimension could be interpreted more reasonably, however, as environmentally controlled and intraspecific. This point of view is supported by recent recovery in the material from bed 5 of one large shell attaining 19.5 mm in width; this specimen is fully conspecific with specimens from beds 14 and 18.

Remarks.— Flabellulirostrum kielcensis sp. nov. is similar in details of the internal shell structure as well as in the general shape and ornamentation of the shell to Bergalaria guerichi Baliński, 1979 (= Flabellulirostrum guerichi ) from the Early Frasnian of the Dębnik anticline, southern Poland. F. kielcensis differs from the latter mainly in having wider sulcus and fold, which attains 51–73% of the total shell width, in comparison to 49–55% in the latter species ( Fig. 10C ). F. kielcensis differs from F. guerichi also by having more numerous costae on fold and in sulcus, namely 6 and 7 costae on average respectively in comparison to 4.5 and 5.5 costae on average in F. guerichi ( Fig. 10D ). It is also noteworthy that the species from Wietrznia seems to be generally a little larger and thicker.

The new species differs from Bergalaria bergica Schmidt, 1975 (= Flabellulirostrum bergica ) from the earliest Frasnian of Bergisches Land by having not as triangular outline of the shell and by costation which in the latter is confined to more anterior region of the shell. Flabellulirostrum afrum ( Drot, 1971) has also more triangular shell outline and shorter, more acute cardinal margin (see Drot 1971, 1982).

Flabellulirostrum kielcensis sp. nov. differs markedly from F. morzadeci Brice, 1983 in Brice and Morzadec (1983) from the Late Givetian of Massif Armoricain, France (see Brice and Morzadec 1983), by having transversally elliptical to subpentagonal outline of the shell whereas the latter is longitudinally suboval and possesses more acute cardinal margin and more numerous costae. F. kielcensis sp. nov. is wider and has less acute and longer cardinal margin than F. wolmericus ( Veevers, 1959) described from the Sadler Formation (Early Frasnian) of the Fitzroy Basin, Western Australia.

The distinction of this species from F. rackii sp. nov. is discussed under the remarks on the latter species.

Occurrence.— Flabellulirostrum kielcensis sp. nov. seems to be one of the most common brachiopod species in the Frasnian of the Wietrznia I quarry. Its smaller phenotype is numerous in beds 4 and 5 of Id−W section. Larger phenotype prevails in beds 14, 18, and 31 of the section as well as in beds 29, 30, and 43–45 of the Ie section. All occurrences represent Palmatolepis transitans conodont Zone.

Length (mm)

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%

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width sulcus of

Index

Width (mm) Length (mm) Width (mm)

Figures

Fig. 8. Rhynchonellid brachiopods from the Frasnian of Wietrznia and Dębnik. A. Flabellulirostrum guerichi (Baliński, 1979), ZPAL Bp 60/15, complete shell from the Nodular Limestone (Palmatolepis hassi Zone) of Dębnik in dorsal (A1), ventral (A2), lateral (A3), posterior (A4), and anterior (A5) views. B–D. Flabellulirostrum kielcensis sp. nov., ZPAL Bp 60/1 (B), ZPAL Bp 60/2 (C), and GIUS 4−273 Wt/IM−1 (D), three shells (C—holotype) from the middle Wietrznia Beds of Wietrznia Ie (B, C) and Id−W (D), in dorsal (B1, C1, D1), ventral (B2, C2, D2), lateral (B3, C3, D3), posterior (B4, C4, D4), and anterior (B5, C5, D5) views. E–G. Flabellulirostrum rackii sp. nov., ZPAL Bp 60/11 (E), GIUS 4−273 Wt/IM−9 (F), and ZPAL Bp 60/12 (G), three shells (G—holotype) from the middle Wietrznia Beds of Wietrznia Ie (E, G) and Id−W (F) in dorsal (E1, F1, G1) ventral (E2, F2, G2), lateral (E3, F3, G3), posterior (E4, F4, G4), and anterior (E5, F5, G5) views.

Fig. 9. Serial sections of Flabellulirostrum kielcensis sp. nov., ZPAL Bp 60/29, middle Wietrznia Beds of Wietrznia Ie. Numbers refer to distance in mm from ventral umbo.

Fig. 10. Scatter diagrams of shell width to shell length (A), shell thickness to shell length (B), sulcus width to shell width (C), and number of costae on fold to shell width ratios in Flabellulirostrum kielcensis sp. nov. from Wietrznia Id−W and Ie Wietrznia (solid diamonts) and Flabellulirostrum guerichi (Baliński, 1979) from Dębnik (open diamonts).