Protacrodus sp.

Ginter, Michał & Sun, Yuanlin, 2007, Chondrichthyan remains from the Lower Carboniferous of Muhua, southern China, Acta Palaeontologica Polonica 52 (4), pp. 705-727 : 712

Protacrodus sp.

Fig. 4A, B.

Material.—Four teeth.

Description. —These protacrodont teeth are characterised by a pentacuspid crown with a prominent, labio−lingually compressed median cusp, about twice as high as the lateral cusps ( Fig. 4B 3 ) or a little less ( Fig. 4A 3 ). All the lateral cusps may either be equal to each other or the outermost are the largest. All the cusps are rounded in both the labial and lingual views and ornamented on both sides with two generations of cristae: the outer, concentric and parallel to the cusps margins and the inner, more vertical ones, often branching basally. The base is perforated by a single large nutritive canal whose openings are situated submedially on the lingual and basolabial faces. It is uncertain whether the other, minute foramina particularly visible in Fig. 4B 1 were open on the surface before fossilisation.

In the rounded shape of the cusps and the form of cristae, Protacrodus sp. is similar to P. aequalis Ivanov, 1996 , but the crown of the latter is characterised by only three cusps of virtually the same size.

Figures

Fig. 3. Cladodont teeth from sample MH−1, middle Tournaisian of Muhua, China. A–C. Stethacanthus sp. A. PKUM02−0133 in lingual (A1) and labial (A2) views. B. PKUM02−0134 in labial (B1) and aboral (B2) views. C. PKUM02−0135 in labial (C1), lingual (C2), oral (C3), and lateral (C4) views. D–G. Tamiobatis sp. D. PKUM02−0136 in lingual (D1) and oral (D2) views. E. PKUM02−0137 in labial view. F. PKUM02−0138 in oral (F1) and lingual (F2) views. G. PKUM02−0139 in lingual view.

Fig. 1. A. Geology of the area of Muhua; location of the studied section (MH) marked with asterisk. B. Location of the Muhua locality in China. C. Stratigraphic column of the MH section with the position of the studied sample (MH−1). D. Major morphological terms of a cladodont tooth in labial view. A–C, courtesy of A. Baliński.