Holocephali Bonaparte, 1841

Ginter, Michał & Sun, Yuanlin, 2007, Chondrichthyan remains from the Lower Carboniferous of Muhua, southern China, Acta Palaeontologica Polonica 52 (4), pp. 705-727 : 716

publication ID

https://doi.org/ 10.5281/zenodo.13741212

persistent identifier

https://treatment.plazi.org/id/954A87EC-2C12-336B-FCDA-FD057AEE7F3D

treatment provided by

Felipe

scientific name

Holocephali Bonaparte, 1841
status

 

Superorder Holocephali Bonaparte, 1841 View in CoL Order Helodontiformes Patterson, 1965 Family Helodontidae Patterson, 1965 Genus Diclitodus Davis, 1883

Diclitodus denshumani ( Newberry and Worthen, 1866) Fig. 7A View Fig .

1866 Helodus denshumani sp. nov.; Newberry and Worthen 1866: 76, pl. 4: 21.

Material.—One tooth.

Description.—The crown of Diclitodus denshumani is convex labially and concave lingually. Its lingual/lateral ends slope down at 45 ° and are gently crenulated. The biting edge is almost horizontal, with lateral corners only slightly higher than the median part. The base is strongly expanded lingually and excavated at the lingual end. The orolingual side of the base is perforated with numerous nutritive canals and grooves. Width of the tooth is 1.5 mm.

Remarks.—An almost identical tooth was described by Newberry and Worthen (1866: pl. 4: 21a–c) from the Viséan Keokuk Limestone of Illinois as Helodus denshumani ; although the illustrations are somewhat confusing, the description and diagrammatic sketch of the lateral view leave no doubt. However, as the tooth is much different from the specimens typically referred to as Helodus , and, on the other hand, resembles the type specimen of Diclitodus scitulus Davis, 1883 ( BMNH P.49629; Fig. 10A View Fig ) from the Carboniferous Limestone of Yorkshire, it should be included in Diclitodus . D. scitulus is much larger (7 mm wide) than D. denshumani and shows more prominent lateral corners of the crown, but the exposed labial part of the holotype (the rest is embedded in limestone) reveals a similar shape of the base.

Based on indirect reasoning, it was suggested (Woodward, unpublished notes, fide Stahl 1999: 54) that Diclitodus is a symphyseal tooth of a helodontiform. Such a position could explain the extreme rarity of such forms in comparison to other bradyodont teeth and tooth−plates. This being the case, it is quite possible that Diclitodus sp. is in fact a symphyseal tooth of the next described species, Helodus coniculus , and, consequently, represents the genus Helodus , as originally proposed.

Kingdom

Animalia

Phylum

Chordata

Class

Holocephali

Loc

Holocephali Bonaparte, 1841

Ginter, Michał & Sun, Yuanlin 2007
2007
Loc

Helodus denshumani

Newberry, J. S. & Worthen, A. H. 1866: 76
1866
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