BULLETIN DE L'INSTITUT ROYAL DES SCIENCES NATURELLES DE BELGIQUE, BIOLOGIE, 64 : 147-163, 1994 BULLETIN VAN HET KONINKLIJK BELGISCH INSTITUUT VOOR NATUURWETENSCHAPPEN. BIOLOGIE, 64 : 147-163, 1994 Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in living supra-specific taxa of Chondrichthyan fishes Editor : M. STEHMANN Addendum to Part A, No. 1 : Order : Hexanchiformes - Family : Hexanchidae. Odontological results supporting the validity of Hexanchus vitulus SPRINGER & WALLER, 1969 as the third species of the genus Hexanchus RAFINESQUE, 1810, and suggesting intrafamilial reordering of the Hexanchidae. by J. HERMAN, M. HOVESTADT-EULER and D.C. HOVESTADT Abstract mungsschlussel vorgestellt Die dargestellten odontologischen Ergeb- nisse legen eine andere intrafamiliare Gruppierung der Arten als die The tooth morphology of all hexanchid species, including the contro­ bishenge nach Zahl der Kiemenbogen, die anscheinend weniger rele­ versial species Hexanchus nakamiuai and H vitulus, is re-examined vant 1st. and illustrated. Odontologically Hexanchus nakamurai is clearly dis­ Schusselworter : Elasmobranchii - Selachii - Hexanchidae - Systema- tinct from H \itulus tik - Taxonomie - Odontologie An odontological determination key to all hexanchid species is given. The odontological results presented suggest another intrafamilial ordering of the taxa than by the number of branchial arches, which seem to be less important Key-words : Elasmobranchii - Selachii - Hexanchidae - Systematics - Introduction Taxonomy - Odontology. An addendum to Part A, No. 1, Family Hexanchidae is presented to further elucidate odontological characters Résumé of the three genera and their interrelationships. New arguments are provided, that Hexanchus vitulus La morphologie dentaire de tous les Hexanchidae, et en particulier appears to be a valid third species of the genus. ceWe d'Hexanchus nakamurai et de H xüulus espèces dont la validité Although, the aim of this series is to illustrate and restait controversée, est réexaminée et hgurée Cette demière espèce est odontologiquement distinguable d'Hexanchus nakamurai describe micro-teeth only, in the present case the Une clef de determination odontologique de tous les Hexanchidae est odontological characters of anterior and lateral macro- proposée. Les résultats de la présente étude odontologique suggèrent teeth were added to those of the posterior micro-teeth to des relations différentes entre les taxa de cette familie, autres que provide full information. celles avancées sur base du nombre de fentes branchiales dont l'importance semble tres relative TENG (1962) distinguished a new subspecies Hexanchus Mots-clés : Elasmobranchii - Selachii - Hexanchidae - Systématique - griseus nakamurai as a second form within the genus, Taxonomie - Odontologie. and SPRINGER & WALLER (1969) described a new spe­ cies ƒ/. vitulus. Variously the originally subspecies nakamurai of H. griseus has been synonymized by aut­ Kurzfassung hors either with H. griseus, or with the more recently described H. vitulus. TANIUCHI & TACHIKAWA (1991) Die Zahnmorphologie aller hexanchiden Arten, einschliesslich der resurrected nakamurai at species rank and synonymized strittigen Hexanchus nakamurai und H vitulus wird uberpruft und illustriert Odontologisch ist Hexanchus nakamurai deutlich von H /ƒ. vitulus with the latter. However, in their diagnoses vitulus zu unterscheiden neither TENG, nor SPRINGER & WALLER had included Fur alle Arten der Hexanchidae wird ein odontologischer Bestim- odontological information, and neither was such given 148 J. HERMAN, M. HOVESTADT-EULER and D.C HOVESTADT by TANIUCHI & TACHIKAWA Since tooth samples and Coll Herman 9 780 mm TL. Qaws) odontological information of all three forms became Coll. Herman ê 1220 mm TL. Oaws) available, investigational results support the validity of Coll Herman 6 890 mm TL. Qaws) all three species of Hexanchus It also turned out, that Coll Herman 6 670 mm TL. Oaws) the paratype of H xitulus happens to be a specimen of Coll Hovestadt 9 3150 mm TL. (jaws) H nakamwai. Coll. Hovestadt 9 2190 mm. TL. Oaws) A comparison of photographs of the jaw dentition of Coll Hovestadt 9 1150 mm TL. Oaws) H vitulus holotype (USNM 200674) and the jaws of Coll Hovestadt 9 1140 mm TL. Oaws) H vitulus (ORI 2822) from off Natal, as illustrated by Coll. Hovestadt 9 720 mm. TL. Oaws) BASS, D'AUBREY & KISTNASAMY (1975), revealed con­ Coll. Hovestadt 6 2050 mm TL. Oaws) formable tooth morphology. The jaws of another male Coll Hovestadt ê 1530 mm. TL Oaws) specimen (RUSI 6897), having been caught in a shark Coll. Hovestadt 6 1180 mm. TL. Oaws) net off Park Rynie and also mentioned by the latter Coll. Hovestadt ê 1180 mm TL Oaws) authors, were also examined and had the same dentition Coll. Hovestadt Ó 1160 mm TL Oaws) as both specimens mentioned above. Coll Hovestadt S 920 mm TL. Oaws) Furthermore, we compared jaw photographs of the Coll. Hovestadt ê 800 mm. TL Oaws) H vitulus paratype (USNM 200675), jaws of Japanese specimen (FUMT P 10859) from off Ogasawara Islands Hexanchus vitulus (TANIUCHI & TACHIKAWA, 1991), jaws of a male Holotype USNM 200674 s 1480 mm TL (AMNH 33475) and female (AMNH 29830) (both (photographs) without data), and a jaw of a Canbbean specimen Paratype USMN 200675 9 1420 mm TL. (uncat) at the Institut des Sciences Naturelles de Belgi- (photographs) que, Brussels, which all were determined as H vitulus. ORI 2822 6 1550 mm TL. Oaws) They all showed conformable tooth morphology too but RUSI 6897 S 1550 mm TL. Oaws) clearly differed in odontological characters from those of the H vitulus holotype and both African specimens Hexanchus nakamurai of this species mentioned above FUMT-P10643 9 958 mm. TL. The tooth morphology of the hexanchid-species H gii- (postenor upper seus, H vitulus and H nakamwai is here described, and lower teeth) illustrated and compared FUMT-P10859 6 1171 mm TL The illustrations in BASS, D'AUBREY & KISTNASAMY, (symphysial, para 1975 are used for further comparison of the species of symphysial and Hexanchus with Heptranchias peilo and Notorhynchus lateral upper and cepedianus and to illustrate general odontological lower teeth) characters AMNH 33475 Ó 1100 mm TL. Oaws) The authors will here not draw any nomenclatorially AMNH 29830 9 1575 mm. TL. Oaws) valid conclusions. Being aware of dealing with one IRSNB uncat. ? No data Oaws) complex of characters only, they will present their odontological results and leave it to following revising Notorhynchus cepedianus authors to incorporate also odontological points of view Coll Vanderhoeft S 2400 mm. TL. Oaws) in a full systematic review with possible taxonomie and nomenclatonal changes. Heptranchias pei lo Coll. Herman 6 1150 mm. TL. Oaws) Coll. Herman 9 1200 mm TL. Oaws) Coll. Hovestadt 9 1220 mm TL Oaws) Materials and method The odontological differences are mainly documented The following 35 specimens of 5 species were exa­ by the biometncal results of the lower lateral teeth. mined : Textfigure 1 shows the tour artificial lines resulting in five measurements : Hexo nchus gi iseus 1 cusplet apex line Coll Herman ? 2700 mm TL. (jaws) — connecting as straight line all cusplet Coll. Herman 9 1270 mm TL (jaws) apices. Coll. Herman ? 1190 mm. TL. (jaws) 2 crown base line Coll Herman 9 1100 mm TL (jaws) — connecting extreme mesial and distal Coll. Herman ? 1050 mm TL. (jaws) edges ot tooth along crown-root junc­ Coll. Herman 9 890 mm TL (jaws) tion. Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites 149 3 : root base line HETERODONTY — connecting extreme mesial and distal lower edges of root, and may cut Disregarding the commissural teeth, hexanchid dentition through median lower part of root. is in general gradient dignathic heterodont. 4 : principal cusp dividing line The dentition of an upper jaw half consists of two ante­ — from tip of principal cusp along about rior rows (including the parasymphysial one), seven midline of its exposed upper part, and lateral rows (with the exception of five rows in A', cepe­ not connecting to a fixed lower point. dianus) and eight to fourteen commissural rows. The dentition of a lower jaw presents one symphysial The corresponding standard measurements are accord­ row, five lateral rows in Heptranchias perlo, Hexanchus ingly : vitulus and H. nakamurai, but six in Hexanchus griseus A : maximum cusplet height - distance between points and Notorhynchus cepedianus and three to thirteen com­ of intersection of lines 1 and 2 with line 4. missural rows. B : exceeding length of principal cusp - distance The anterior and lateral teeth of both upper and lower between tip of principal cusp and point of intersection jaws are strongly compressed in inner-outer direction of lines 1 and 4. with a narrow anaulacorhizid root. Commissural teeth of C: mesial length of root - perpendicular distance both upper and lower jaws are always irregularly shaped between lines 2 and 3 at extreme upper mesial edge of and show flattened crown, mostly presenting a median root. keel, and an anaulacorhizid, relatively wide root. Due to E : maximum length of crown - distance between ex­ their inactive function, they are irregularly shaped and treme mesial and distal edges of crown, i.e. points of numbered, and rest as rudimentary remains. However, line 2. their crown possesses an inner and outer ornamentation, which is characteristic for its genus (Hovestadt, Hove- stadt & Smith, 1983; Herman, Hovestadt & Hovestadt- Euler,1987).