Polychaetaspis kozlowskii, Szaniawski & Drygant, 2014

Szaniawski, Hubert & Drygant, Daniel, 2014, Early Devonian scolecodonts from Podolia, Ukraine, Acta Palaeontologica Polonica 59 (4), pp. 967-983 : 972

Polychaetaspis kozlowskii sp. nov.

Fig. 5A–G .

Etymology: In honour of the great paleontologist and teacher Roman Kozłowski (1889–1977), who first described polychaete jaw apparatuses of the genus.

Holotype: Right MI, ZPAL Sc.8/2.6 ( Fig. 5A ).

Type locality: Section 48, near Khudykivtsi village, Podolia, Ukraine.

Type horizon: Lower part of the Borshchiv Horizon, Lower Lochkovian, Lower Devonian.

Material.— 3 right MI, 4 left MI, and 1 basal plate ( ZPAL. Sc.8/2.4–2.6, 2.13–2.15, 2.17), sample S.Kh. 1. All from the type locality and horizon, from lower part of the section 48

Fig. 2 ).

Diagnosis.—Right MI of the length more than two times bigger than width, with bight significantly longer than half of the jaw length and 14–15 denticles on the inner margin. First denticle curved posteriorly, in the direction of the outer margin. Inner slope steep, narrowing posteriorly. Opening of the pulp cavity much longer than half of the jaw length. Left MI widest above the middle length, with dentary line slightly sigmoid and inner wing much longer than half of the jaw length. Basal plate about three times longer than wide gradually narrowing in posterior part, with inner margin nearly straight, bearing about 15 denticles.

Description.—Right MI more than twice longer than wide. Bight longer than half of the jaw length. Shank well differentiated, triangular, directed postero-laterally. Dentary formed of 14–15 denticles. The first one large, in form of a hook curved posteriorly, toward the outer margin. Of the others the biggest are some at the middle part and the smallest those at the most posterior part. Inner slope wide, narrowing posteriorly. Left MI widest above the middle length. Dentary line slightly sigmoid, curved medially in the anterior part and outwardly in the posterior part, bears 13–15 denticles of which those in the middle part are the biggest. First denticle much bigger than all others, directed posteriorly. Shank short, well differentiated, triangular in shape, pointed laterally. Outer margin over the shank slightly concave, beneath the shank straight, directed postero-medially. Inner wing wide, longer than half of the jaw length. Ligament scar in both MI not preserved. Basal plate of the length about three times the width. Its denticulated, inner margin nearly straight, bears 15 denticles of which the first is longest and hooked. Next four are much smaller, narrow and laterally directed. Others gradually increase in width, became triangular and posteriorly directed. The last two are smaller, short and again laterally directed. Outer margin convex in the anterior part and nearly straight, directed postero-medially in the posterior part. Its anterior part is separated from the posterior one by a small incision. Most posterior part of the plate is triangular and pointed.

Comparisons.—Basal plate of the new species is somewhat similar to that described by Eller (1938) from the Devonian of Michigan, as Oenonites orthodentes Eller, 1938 , but is comparatively wider, has more and differently arranged denticles and shorter undenticulated posterior part of the plate. Right MI is similar to the jaw described by Eller (1961) from the well samples of the Devonian of Michigan as Lumbriconereites cooperi? Eller, 1938 but differs from it by longer bight and bigger number of denticles. From the Polychaetaspis sp. found in the Upper Devonian of Poland ( Szaniawski and Wrona 1973) the new species differs significantly by the shape of the basal plate. From the joined jaws described by Jansonius and Craig (1974) as Polychaetaspis cooperi? ( Eller, 1938) comb. nov. The right MI of the new species differs with slightly longer bight, while the left MI differs by concave anterior part of the outer margin. The new species is very similar to the species described by Männil and Zaslavskaja (1985) as Polychaetaspis cf. aequilateralis Kielan-Jaworowska, 1966 . However, the right MI of the new species differs from the corresponding element of it by concavity in the anterior part of the outer margin and by longer inner wing of the left MI. The right MI of the new species is very similar to corresponding element of Polychaetaspis cf. wyszogrodensis Kozłowki, 1956 described by Hints (1998). It differs from it only by somewhat narrower posterior part and longer bight. Both MIs of the new species are very close to the corresponding jaws illustrated as Oenonites sp. from Silurian of Canadian Arctic (Hints at al. 2000: figs. 7–9) but the left MI of the new species is somewhat wider while the right MI has a longer bight. The right MI of the new species is very close to the corresponding jaw from boring cores of the Wenlockian deposits in Estonia, assigned to Oenonites sp. by Hints et al. (2006: pl. 2: 8), but is slightly narrower.

Remarks.—Possessed collection is not rich but contain three most characteristic and well preserved elements of a polychaetaspid apparatus. The elements fit to each other very well and have been found in the same sample. There is no doubt that they belonged to apparatuses of the same species, the more that all other samples did not contain any elements of polychaetaspids. The new species belongs to the group of species similar to Polychaetaspis wyszogrodensis Kozłowski, 1956 (sensu Kielan-Jaworowska 1966).

Stratigraphic and geographic range.— Type locality and horizon only.

Figures

Fig. 5. SEM micrographs of polychaetaspid scolecodonts from Lower Lochkovian of Podolia, lower part of Borshchiv Horizon, section 48, sample S.Kh.1. A–G. Polychaetaspis kozlowskii sp. nov. A. ZPAL Sc.8/2.6, holotype, right MI in dorsal view. B. ZPAL Sc.8/2.15, right MI in dorsal view. C. ZPAL Sc.8/2.14, incomplete right MI in dorsal (C 1) and ventral (C 2) views. D. ZPAL Sc.8/2.5, basal plate in dorsal (D 1) and right lateral (D 2) views. E. ZPAL Sc8/2.17, left MI in dorsal (E 1) and left lateral (E 2) views. F. ZPAL Sc.8/2.13, left MI in dorsal (F 1) and oblique ventral (F 2) views. G. ZPAL Sc.8/2.4, left MI in dorsal (G 1) and oblique left lateral (G 2) views. H. Polychaetaspis? sp., ZPAL Sc.8/2.20, left MIII? in dorsal (H 1) and right lateral (H 2) views. I–L. Polychaetaspis? spp. anterior plates (MIV). I. ZPAL Sc8/2.1, right MIV in dorsal (I 1) and dorsal lateral (I 2) views. J, K. Right MIV in ventral lateral view. J. ZPAL Sc8/2.12. K. ZPAL Sc.8/2.11. L. ZPAL Sc8/2.24, left MIV in ventral lateral view.

Fig. 2. Stratigraphic ranges of the described scolecodonts. Section numbers as in Fig. 1.