Podoliacanthus sp. 1

Voichyshyn, Victor & Szaniawski, Hubert, 2012, Acanthodian jaw bones from Lower Devonian marine deposits of Podolia, Ukraine, Acta Palaeontologica Polonica 57 (4), pp. 879-896 : 890

Podoliacanthus sp. 1

Figs. 5G, 6C, E, F.

Material.—Three jaw bone fragments: ZPAL P.14/2.3, about 1 mm long, with 2 teeth; ZPAL P.14/9.7, 1.7 mm long, with two preserved teeth; and ZPAL P.14/11.15, 1.5 mm long, with two slightly worn but near complete teeth. All the specimens are obtained from two samples collected in 2008 and 2010 from the same locality and about the same stratigraphic level: left bank of the Dniester River, vicinity of Ivanie Zolote ( Fig. 2C); upper part of Ivanie Horizon of the Tyver Series, about 11 m below the boundary with the Dniester Series, Lower Devonian.

Description.—The teeth are rather thick in the lower 2/3 of their height, and markedly tapered in their upper third. Their width to height ratio is about 0.73. In the posterior to anterior view, the largest tooth in the main row has a convex lateral outline and sinusoidal medial profile ( Fig. 5G). The additional tooth denticles are represented by one medial side denticle, as in the type species. However in the specimen ZPAL P.14/11.15 this denticle is doubled, and on the smaller tooth of the jaw bone fragment there is a medial side ridge ( Fig. 6C). All the teeth of the form bear quite wide anterior and posterior flanges ( Fig. 6C, E, F). The lingual ridge is inclined anteriorly ( Fig. 6C, F). Posterior inclination of the teeth is better expressed than in the type species ( Fig. 6C, E, F). Well developed denticle groups of the lingual tooth row, including arrangement of the denticles in three lines, are typical for Podoliacanthus gen. nov. ( Fig. 6C). The inter−tooth denticles, probably six or seven in number, are poorly preserved. Pores of vascular canals on the inter−tooth pit surface are similar to those in the type species.

Remarks.—Although not well preserved, all three specimens share several morphological features: the teeth are thick at the base and tapered in their upper third, with well expressed posterior inclination, well developed medial denticle groups of unified morphology and presence of both the posterior and anterior flanges of the teeth. Some of these features distinguish this form from the most similar Podoliacanthus zychi sp. nov. The form differs from the type species in having teeth thicker in parabasal section, stronger posterior inclination of the tooth tips, relatively larger and more unified morphologically lingual denticle groups, and relatively wider tooth flanges, including an anterior one that seems to be lacking in Podoliacanthus zychi sp. nov. The described difference cannot be regarded as intraspecific variations of Podoliacanthus zychi sp. nov., but may indicate a separate species, but the available material is too incomplete to permit establishment of a new species.