| The tooth crown of the Japanese topeshark, Hemitriakis japanica (MÜLLER & HENLE, 1839) has costules on its lingual mesial base (Herman, 1988*1). We examined this ornamentation in detail to see if it could serve as a means of detailed identification. The specimens used in this study were a male shark measuring 88.5 cm in length and a female shark measuring 99.5 cm in length. Both sharks were collected in the waters off Peninsular shima. |
| Plate 1; Specimens were taken from the right side jaw of both male and female sharks. A total of eight teeth were examined, four each from the upper and lower seventh and eleventh.. |
| The range of costules observed and their characteristics are described in the Plate. |
| Using both the image data of the dentition (overall shape) of the Japanese topeshark and the image data of the costules shown here, we attempted to identify the fossil teeth of the Japanese tope shark (plate 2) in detail. The results are shown in Table 1. |
| plate 2: Fossil shark teeth of the Japanes topeshark |
| Table1. Identification |
| specimen | (1) | (2) | (3) |
| species | H. japanica | ||
| sex | female | female | male |
| stage | adult | adult | adult |
| position | LL5-LL7 | UL3 | UL9-UL12 |
| Miscellaneous impressions; I was surprised because I thought the costule was ornamentation in the enamelloid of the crown, but the structure actually reached the root of the tooth. |
| Ref. *1 BIOLOGIE, 58: 99-126, 1988 Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in living supraspecific taxa of Chondroichthyan fishes Editor: M. STEHMANN Part A: Selachii. No.2a: Order: Carcharhinusformes-Family: Triakidae by J. HERMANN, M. HOVESTADT- EULER and D.C. HOVESTADT |
| ver.1. 20241104 |
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