Table Of ContentBULLETIN DE L'INSTITUT ROYAL DES SCIENCES NATURELLES DE BELGIQUE, BIOLOGLE, 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 1n 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 H exanchus 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 mungsschliissel vorgestellt. Die dargestellten odontologischen Ergeb
nisse legen eine andere intrafamiliare Gruppierung der Arten als die
bisherige nach Zahl der Kiemenbogen, die anscheinend weniger rele
The tooth morphology of all hexanchid species, including the contro
versial species Hexanchus nakamurai and H. vitulus, is re-examined vant ist.
and illustrated. Odontologically Hexanclws nakamurai is clearly dis Schiisselworter : Elasmobranchii -Selachii -Hexanchidae -Systema
tinct from H. vitulus. 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.
Introduction
Key-words : Elasmobranchii -Selachii -Hexanchidae -Systematics
Taxonomy-Odontology.
An addendum to Part A, No. 1, Family Hexanchidae is
presented to further elucidate odontological characters
Resume 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.
celle d'Hexanchus nakamurai et de J-1. vitulus, especes dont Ia validite Although, the aim of this series is to illustrate and
restait controversee, est reexaminee et figuree. Cette derniere espece
describe micro-teeth only, in the present case the
est odontologiquement distinguable d'Hexanchus nakamurai.
Une clef de determination odontologique de tous les Hexanchidae est odontological characters of anterior and lateral macro
proposee. Les resultats de Ia presente etude odontologique suggerent teeth were added to those of the posterior micro-teeth to
des relations differentes entre les taxa de cette famille, autres que provide full infmmation.
celles avancees sur base du nombre de fentes branchiales dont
TENG (1962) distinguished a new subspecies Hexanchus
!'importance semble tres relative.
Mots-cles : Elasmobranchii -Selachii - Hexanchidae -Systematique - griseus nakamurai as a second form within the genus,
Taxonomie -Odontologie. and SPRINGER & WALLER (1969) described a new spe
cies H. 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. TANIUCHl & TACHIKAWA (1991)
Die Zahnmorphologie aller hexanchiden Arten, einschliesslich der resurrected nakamurai at species rank and synonymized
strittigen Hexanchus nakamurai und H. villi/us wird iiberprlift und
H. vitulus with the latter. However, in their diagnoses
illustriert. Odontologisch ist Hexanchus nakamurai deutlich von H.
vitu/us zu unterscheiden. neither TENG, nor SPRINGER & WALLER had included
Fiir aile Arlen der Hexanchidae wird ein odontologischer Bestim- odontological information, and neither was such given
''
148 1. HERMAN, M. HOYESTADT-EULER and D.C. HOYESTADT
by TANlUCHI & TACHlKAWA. Since tooth samples and Coli. Herman 2 780 mm. TL. Uaws)
odontological information of all three forms became Coli. Herman 0 1220 mm. TL. Uaws)
available, investigational results support the validity of Coli. Herman 0 890 mm. TL. Uaws)
all three species of Hexanchus. It also turned out, that Coli. Herman 0 670 mm. TL. Uaws)
the paratype of H. vitulus happens to be a specimen of Coli. Hovestadt 2 3150 mm. TL. Uaws)
H. nakamurai. Coli. Hovestadt 2 2190 mm. TL. Uaws)
A comparison of photographs of the jaw dentition of Coli. Hovestadt 2 1150 mm. TL. Uaws)
H. vitulus holotype (USNM 200674) and the jaws of Coli. Hovestadt 2 1140 mm. TL. Uaws)
H. vitulus (ORI 2822) from off Natal, as illustrated by Coli. Hovestadt 2 720 mm. TL. Uaws)
BASS, D' AUBREY & KISTNASAMY (1975), revealed con Coli. Hovestadt 0 2050 !Tim. TL. Uaws)
formable tooth morphology. The jaws of another male Coil. Hovestadt 0 1530 mm. TL. Uaws)
specimen (RUSI 6897), having been caught in a shark Coli. Hovestadt 0 1180 mm. TL. Uaws)
net off Park Rynie and also mentioned by the latter Coil. Hovestadt 0 1180 mm. TL. Uaws)
authors, were also examined and had the same dentition Coil. Hovestadt 0 1160 mm. TL. Uaws)
as both specimens mentioned above. Coli. Hovestadt 0 920 mm. TL. Uaws)
Furthermore, we compared jaw photographs of the Coli. Hovestadt 0 800 mm. TL. Uaws)
H. vitulus paratype (USNM 200675), jaws of Japanese
specimen (FUMT P.l 0859) from off Ogasawara Islands Hexanchus vitulus
(TANlUCHI & TACHlKAWA, 1991), jaws of a male Holotype USNM 200674 0 1480 mm. TL.
(AMNH 33475) and female (AMNH 29830) (both (photographs)
without data), and a jaw of a Caribbean specimen Paratype USMN 200675 2 1420 mm TL.
(uncat.) at the Institut des Sciences Naturelles de Belgi (photographs)
que, Brussels, which all were detennined as H. vitulus. ORI 2822 0 1550 mm. TL. Uaws)
They all showed conformable tooth morphology too but RUSI 6897 0 1550 mm. TL. Uaws)
clearly differed in odontological characters from those
of the H. vitulus holotype and both African specimens !-lexanchus nakamurai
of this species mentioned above. FUMT-Pl0643 2 958 mm. TL.
The tooth morphology of the hexanchid-species H. gri (posterior upper
seus, H. vitulus and H. nakamurai is here described, and lower teeth)
illustrated and compared. FUMT-P10859 0 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 perlo and Notorhynchus lateral upper and
cepedianus and to illustrate general odontological lower teeth)
o
characters. AMNH 33475 1100 mm. TL. Uaws)
The authors will here not draw any nomenclatorially AMNH 29830 2 1575 mm. TL. Uaws)
valid conclusions. Being aware of dealing with one IRSNB uncat. ? No data Uaws)
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 Coli. Vanderhoeft o 2400 mm. TL. Uaws)
in a full systematic review with possible taxonomic and
nomenclatorial changes. Heptranchias perlo
o
Coli. Herman 1150 mm. TL. Uaws)
Coli. Herman 2 1200 mm. TL. Uaws)
Coil. Hovestadt 2 1220 mm. TL. Uaws)
Materials and method
The odontological differences are mainly documented
The following 35 specimens of 5 species were exa by the biometrical results of the lower lateral teeth.
mined: Textfigure 1 shows the four artificial lines resulting in
five measurements :
Hexanchus griseus 1 : cusplet apex line
Coli. Herman 2 2700 mm. TL. Uaws) - connecting as straight line all cusplet
Coil. Herman 2 1270 mm. TL. Uaws) apices.
Coil. Herman 2 1190 mm. TL. Uaws) 2 : crown base line
Coil. Herman 2 1100 mm. TL. Uaws) - connecting extreme mesial and distal
Coli. Herman 2 1050 mm. TL. Uaws) edges of tooth along crown-root junc
Coil. Herman 2 890 mm. TL. Uaws) 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 inN. 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 nan·ow 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).
Sexual heterodonty does not exist, but ontogenetic hete
rodonty is given by lower number of cusplets in lateral
teeth of upper and lower jaws.
DESCRIPTION OF THE ODONTOLOGICAL CHARACTERS
The description of the odontological characters will here
only consider anterior and lateral teeth of upper and
0
u
lower jaws of Heptranchias perlo, Hexanchus griseus
and Notorhynchus cepedianus. Commissural teeth were
already described in Part A, No. 1 of this series.
Textfigure 1. - Biometrical criterions.
Genus: Heptranchias RAFINESQUE, 1810
Heptranchias perlo (BONNATERRE,l788)
Squa!us per!o, Bonnaterre, 1788, Tableau encyclopedique et
Family : Hexanchidae methodique des trois regnes de Ia nature. Paris, p. 10.
After CoMPAGNO (1984), the family Hexanchidae com UPPER JAW
prises three genera : Notorhynchus, monotypic with the
type species Notorhynchus cepedianus (PERON, 1807), The crown of anterior and lateral teeth has an elongated
Heptranchias, monotypic with the type species Hept principal cusp, which is inclined distally and sigmoidal
ranchias per/o (BONNATERRE, 1788) and Hexanchus in both anterior teeth and slightly bent in lateral ones.
with the type species Hexanchus griseus (BONNATERRE, The crown height diminishes toward the commissure.
1788) and Hexanchus vitulus SPRINGER & WALLER, The size of the root remains more or less equal through
1969. Hexanchus nakamurai TENG, 1962 resurrected as out.
a senior synonym of H. vitulus by TANIUCHI & TACHI The mesial cutting edge of the anterior teeth is smooth,
KAWA (1991). whereas lateral teeth bear two or three mesially directed
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Textplate. - Hexanchus vitulus SPRINGER & WALLER, 1969.
o
1. Holotype, USNM 200674, 1480 mm tl., Bahamas USA; some upper and lower teeth.
2. Paratype, USNM 200765 <i! 1420 mm tl., Bahamas USA; left (a) and right side views (b) of the jaws.
Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites 151
cusplets at the base. The number of cusplets increases Genus: Hexanchus RAFINESQUE,l810
toward the commissure. The orientation of the distal
cutting edge follows more or less the angle of the Hexanchus griseus (BONNATERRE,1788)
principal cusp, curves distally just before reaching the (Plates l & 2)
base of the crown, to form a blade on anterior teeth.
One to four distally directed cusplets are present on Squalus griseus BONNATERRE, 1788. Tableau encyclopedique
et methodique des trois regnes de Ia nature. Paris, p. 9.
lateral teeth, their number increasing toward the com
missure. A juvenile specimen was selected for comparison with
The flattened root is anaulacorhizid and subquadrangu specimens equally small as H. vitulus and H. nakamu
lar in shape. rm.
The principal cusp and cusplets are slightly convex and
smooth on outer surface, stronger convex and smooth UPPER JAW
on inner surface.
An inner or outer ornamentation is absent. The crown of anterior and lateral teeth has an elongated
The inner part of the root is divided by a protuberating, principal cusp, which is slightly bent distally. The crown
transverse ridge just below the crown-root junction. height diminishes toward the commissure. However, the
One or two vertically elongated apertures may be size of the root remains nearly equal in the first five
present on the lower part, which in fact are side-long tooth rows and becomes slightly wider only from the
opened vertical canals, being part of the vascularization sixth tooth row onward.
system (HOVESTADT & HOVESTADT-Euler, 1993). Minute The mesial cutting edge of tl1e anterior and lateral teeth
foramina are scattered all over the lower part of the is smooth. A poorly developed, distally directed, cusplet
root. may be present. The distal cutting edge follows more or
less the angle of the principal cusp, and curves distally
just before reaching the base of the crown, forming a
LOWER JAW
blade on anterior first two lateral teeth. On the follow
ing, lateral teeth one or two, distally directed cusplets
The principal cusp of the symphysial tooth is erect and are present. (In adult specimens all laterals have one to
flanked by two pairs of cusplets, of which the outer ones four distal cusplets)
are very low. The crown of the lateral teeth bears an The flattened root is anaulacorhizid and subquadrangu
elongated, distally inclined principal cusp with two or lar in shape.
three well developed mesial cusplets, three to five, more The principal cusp and cusplets are slightly convex and
or less equally large, distal cusplets and one or two smooth on outer surface, more convex and also smooth
lower cusplets at the extreme distal edge. The dimen on inner surface.
sions of A and B (textfigure 1) are equal sized, which An inner or outer ornamentation is absent.
show the extreme height difference between the princi The inner part of the root is divided by a protuberating,
pal cusp and cusplet apex line. transversal ridge, just below the crown-root junction.
The principal cusp becomes stronger inclined toward On the lower part one or two, vertically elongated aper
the commissure, and the number of distal cusplets tures can be present. Minute foramina are scattered all
decreases. over the lower part of the root.
The mesial and distal cutting edges of principal cusp
and cusplets are smooth. LOWER JAW
The flattened root is anaulacorhizid and more or less
quadrangularly shaped, becoming wider in teeth toward The principal cusp of the symphysial tooth can be ex
the commissure. From the crown-root junction down tremely bent distally or mesially (this is undefined),
ward the root is constricted at the mesial edge. The root flanked by a pair of cusplets, of which the ones at the
height C at the mesial part is slightly higher than at the extreme edges are very low. The crown of the lateral
distal part D. The dimensions of C are 25 to 28 % of the teeth presents a low principal cusp, which is distally
total tooth width E. oblique. Mesial cusplets or senation are absent. Three to
The principal cusp and cusplets are slightly convex and five, distal cusplets (seven to nine in adult specimens)
smooth in outer view, but more convex and also smooth are present, which gradually diminish in height. The
in inner view. very low height difference between the principal cusp
An inner and outer ornamentation is absent. and the first cusplet makes B (textfigure 1) absent,
The inner part of the root is divided by a protuberating. which means, that the apex of the crown is in line with
transversal ridge, just below the crown-root junction. the cusplet apex line.
On the lower part one or two, vertically elongated aper The principal cusp becomes more oblique and the num
tures can be present. Minute foramina are scattered all ber of distal cusplets slightly decreases closer toward
over the lower part of the root. the commissure.
I I
152 J. HERMAN, M. HOVESTADT-EULER and D.C. HOVESTADT
The mesial and distal cutting edges of the cusplets are LOWER JAW
smooth.
The flattened root is anaulacorhizid and more or less
The principal cusp of the symphysial tooth is more or
quadrangularly shaped, becoming wider on positions
less erect, flanked by a set of three cusplets. The crown
closer to the commissure. From the crow-root junction
of the lateral teeth presents a low principal cusp, which
downward the root is constricted at the mesial edge. The
is distally oblique. The mesial cutting edge of tl1e first
root height C at the mesial part is slightly higher than at
two lateral teeth is finely serrated but smooth on the
the distal part D. The dimensions of C are 40 to 44 % of
remaining lateral teeth. Seven to eight, distal cusplets
the total tooth width E.
are present, which gradually diminish in height. The
The principal cusp and cusplets are slightly convex and
very low height difference between the principal cusp
smooth in outer view, but more convex and also smooth
and the first cusplet makes B (textfigure 1) absent,
in inner view.
which means, that the apex of the crown is in line with
An inner and outer ornamentation is absent.
the cusplet apex line.
The inner part of the root is divided by a protuberating,
The principal cusp becomes slightly more oblique and
transversal ridge, just below the crown-root junction.
the number of distal cusplets slightly decreases closer
On the lower part one or two, vertically elongated aper
toward the commissure.
tures can be present, Minute foramina are scattered all
The mesial and distal cutting edges of the distal cusplets
over the lower part of the root.
are smooth.
The flattened root is anaulacorhizid and more or less
quadrangularly shaped, becoming wider on positions
closer to the commissure. From the crown-root junction
downward the root is constricted at the mesial edge. The
He xanc hus nakamurai TENG, 1962
root height C at the mesial part is slightly higher than at
(Plates 3, 4 & 5)
the distal part D. The mesial root height is 22 to 29 % of
the maximum crown length E.
Hexanchus nakamurai TENG, 1962. Classification and distri The principal cusp and the cusplets are slightly convex
bution of the Chondrichthyes of Taiwan. Ogawa print.
and smooth on outer surface but more convex and also
Maizuru, pp. 304.
smooth on inner surface.
An inner or outer ornamentation is absent.
The inner part of the root is divided by a protuberating,
UPPER JAW
transversal ridge, just below the crown-root junction.
On the lower part one or two, vertically elongated aper
The crown of anterior and lateral teeth has an elongated
tures can be present. Minute foramina are scattered all
principal cusp, which is slightly bent distally. The crown
over the lower part of the root.
height diminishes toward the commissure. However, the
size of the root gradually becomes slightly wider toward
the commissure.
COMMISSURAL TEETH
The mesial cutting edge of both anterior teeth is smooth,
whereas that of the first two lateral teeth is slightly
serrated. The remaining lateral teeth have smooth mesial The· morphology of the upper and lower commissural
cutting edges. The orientation of the distal cutting edge teeth is more or less equal. Possible differences are
follows more or less the angle of the principal cusp, within their natural range of variation and therefore are
curves distally just before reaching the base of the not separately described.
crown to form a blade on anterior first two lateral teeth. The commissural teeth are transversely elongated and
One to three distally cusplets are present on the follow low, with a slightly rounded, flattened crown.
ing lateral teeth. A transversal median keel on the crown is mostly absent
The flattened root is anaulacorhizid and subquadrangu and the top of the crown consists of a weakly convex
lar in shape. surface. The outer face presents extremely coarse and
The principal cusp and cusplets are slightly convex and very protuberated, basal costules, that are irregularly
smooth on outer surface, but more convex and also bent longitudinally, often forming a coarse reticulation.
smooth on inner surface. The inner face also has coarse costules, which are less
An inner or outer ornamentation is absent. developed than the outer ones.
The inner part of the root is divided by a protuberating, The anaulacorhizid root is basally large and plane to
transversal ridge, just below the crown-root junction. subconcave. The inner and outer face show some irregu
On the lower part one or two, vertically elongated aper larly lined-up foran1ina.
tures can be present. Minute foramina are scattered all
over the lower part of the root.
I I
Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites 153
Hexanchus vitulus SPRINGER & WALLER,l969 The flattened root is anaulacorhizid and more or less
(Plates 5, 6 & 7., Textplate 1 ) quadrangularly shaped, becoming wider on positions
closer to the commissure. From the crow-root junction
Hexanchus vitulus SPRINGER & WALLER, 1969. Bulletin of downward the root is constricted at the mesial edge. The
Marine Science. 19: 159-174.
root height C at the mesial part is slightly higher than at
the distal part D. The latter diminishes strongly toward
UPPER JAW the commissure. The dimensions of C are 22 to 29 % of
the total tooth width E.
The crown of anterior and lateral teeth has an elongated The principal cusp and cusplets are slightly convex and
principal cusp, which is slightly bent distally. The crown smooth in outer view, but more convex and also smooth
height diminishes toward the commissure. However, the in inner view.
size of the root gradually becomes slightly wider toward An inner and outer ornamentation is absent.
the commissure. The inner part of the root is divided by a protuberating,
The mesial cutting edge of both anteriors is smooth and transversely ridge, just below the crown-root junction.
of the first two laterals slightly serrated. Also the re On the lower part one or two, vertically elongated aper
maining lateral teeth have a weak serration, which is tures can be present. Minute foramina are scattered all
stronger developed in the mid-lateral positions and over the lower part of the root.
again is weaker in the teeth toward the commissure. The
orientation of the distal cutting edge follows more or COMMISSURAL TEETH
less the angle of the principal cusp, and curves distally
just before reaching the base of the crown, forming a The morphology of the upper and lower commissural
blade on anterior first two lateral teeth. One to six distal teeth is more or less equal. Possible differences are
ly directed cusplets are present on the following lateral within their natural range varietion and therefore are not
teeth, with size of cusplets gradually increasing toward described separately.
the commissure. The commissural teeth are transversely very elongated
The flattened root is anaulacorhizid and more or less and low, with a slightly rounded, flattened cusp.
quadrangularly shaped and lower toward the commis The rounded to flattened crowns are divided into an
sure. inner and outer face by a transversal median keel. The
The principal cusp and cusplets are slightly convex and outer face presents coarse, protuberated, basal costules,
smooth on outer surface, but stronger convex and also that are irregularly bent transversely and reach to half
smooth on inner surface. way the outer crown surface. Some teeth also present a
An inner or outer ornamentation is absent. secondary, fine, poorly developed, reticulated ornamen
The inner part of the root is divided by a protuberating, tation between the costules.
transversal ridge, just below the crown-root junction. The inner face also has coarse costules, which are less
On the lower part one or two, ve1tically elongated aper developed than the outer ones.
tures can be present. Minute foramina are scattered all The anaulacorhizid root is basally large and plane to
over the lower part of the root. subconcave. The inner and outer face show some inegu
larly lined-up foramina.
LOWER JAW
The principal cusp of the symphysial tooth is more or less
Genus: Notorhynchus AYRES, 1855
erect, ftarlked by a set of three cusp lets. The crown of the
lateral teeth presents a hjgh principal cusp, which is
Notorhynchus cepedianus (PERRON, 1807)
distally inclined. The mesial cutting edge of teeth of the
first two rows have a coarse senation, becoming poorer Squalus cepedianus PERRON,I807. Voyages de decouverte
developed on teeth of the third and fourth rows and finely aux Terres Australes. Tome I : 377.
has disappeared on teeth of the fifth row. Seven to nine
distal cusplets are present, which gradually diminjsh in UPPER JAW
height. The great difference in height between the prin
cipal cusp and the first cusplet makes B (textfigure 1) 23 The crown of anterior and lateral teeth has an elongated
to 30 % of A, which means, that the apex of the crown is principal cusp, whjch is slightly inclined distally. The
obviously higher than the cusplet apex line. crown height diminishes toward the commissure. The
The principal cusp becomes slightly more oblique and size of the root becomes slightly wider in lateral teeth.
the number of distal cusplets slightly decreases closer The mesial cutting edge of the anterior and lateral teeth
toward the commissure. is smooth. However, on the more posterior ones a poor
The mesial and distal cutting edges of the distal cuspl ets ly developed, distally directed, cusplet can be present.
are smooth. The orientation of the distal cutting edge follows more
I I
154 J. HERMAN, M. 1-!0VESTADT-EULER and D.C. HOVESTADT
or less the angle of the principal cusp, and curves distal chus cepedianus have a cusplet-like irregularity on the
ly just before reaching the base of the crown, forming a mesial cutting edge. Heptranchias perlo has true mesial
blade on anterior first two lateral teeth. On the follow cusplets, while Hexanchus nakamurai and He.xanchus
ing, lateral teeth one or two, distally directed cusplets vitulus have a mesial serration. All species bear upper a
are present. number of distal cusplets on their upper teeth.
The flattened root is anaulacorhizid and subquadrangu
lar in shape. LOWER TEETH
The principal cusp and cusplets are slightly convex and
smooth on outer surface, stronger convex and also The lower lateral teeth of Hexanchus griseus, Notorhyn
smooth on inner surface. c/1Us cepedianus and Hexanchus nakamur(li have a prin
An inner or outer ornamentation is absent. cipal cusp, that does not, or hardly exceed the height of
The inner part of the root is divided by a protuberating, cusplets. However, in Heptranchias perlo and Hexan
transversal ridge, just below the crown-root junction. chus vitulus the principal cusp is much longer than the
On the lower part one or two, vertically elongated aper cusplet as expressed by the relation of tooth measure
tures can be present. Minute foramina are scattered all ments A and B. Only Heptranchias perfo possesses true
over the lower part of the root. mesial cusplets. Notorhynchus cepedianus and Hexan
chus vitulus have only rather coarse mesial senations,
LOWER JAW and Hexanchus griseus and Hexanchu.s nakamurai lack
mesial cusplets and serrations but show smooth mesial
The principal cusp of the symphysial tooth can be ex tooth edges.
tremely bent distally or mesially (this is undefined), All species have lower lateral teeth bearing a number of
flanked by a pair of cusplets. The crown of the lateral strong distal cusplets.
teeth presents a low principal cusp, which bents distally. The height of the root in juvenile Hexanchus griseus
Mesial cusplets are absent, but a rather coarse serration and Notorhynchus cepedianus is equal, and roughly
is present on the mesial cutting edge of all lateral teeth. twice as high as that of Heptranchias perlo, Hexanchus
Four distal cusplets are present, which gradually dimi nakamurai and Hexanchus vitulus.
nish in height distally. Tooth measurement B (textfigure
1) is nearly 0, which means, that the apex of the princi COMMISSURAL TEETH
pal cusp is about level with the cusplet apex line.
The principal cusp becomes stronger inclined toward The most significant features of the commissural teeth is
the commissure. the ornamentation of the crown. Heptranchias perlo,
The mesial and distal cutting edges of the cusplets are Hexanchus griseus and Notorhynchus cepedianus have
smooth. always a well developed ornamentation (HERMAN,
The flattened root is anaulacorhizid and subquadrangu HOVESTADT and HOVESTADT, 1987), which is relatively
lar in shape, becoming wider in teeth toward the com less developed in Hexanchus nakamurai and Hexanchus
missure. From the crown-root junction downward the vitulus. The ornamentation of Hexanchus vitulus is re
root is constricted at the mesial edge. The root height C stricted to very coarse, basal costules only. In Hexan
at the mesial part is slightly higher than the at the distal chus vitulus the remains of a secondary reticulated orna
part D. The dimensions of C are 39 to 45 % of the total mentation is absent. The costules on commissural teeth
tooth width E. of Hexanchus nakamurai more or less merge to form a
The principal cusp and cusplets are slightly convex and very coarse, poorly developed retictilation.
smooth on outer surface, stronger convex and also
smooth on inner surface.
An inner or outer ornamentation is absent.
The inner part of the root is divided by a protuberating, Conclusions
transversely ridge, just below the crown-root junction.
On the lower part one or two, vertically elongated aper Hexanchus nakamurai and Hexanchus vitulus are clear
tures can be present. Minute foramina are scattered all ly distinguishable by odontological characters. So far,
over the lower part of the root. only three specimens of He.xanchu.s vitulus and six of
H exanchus nakamurai could be re-identified by the
authors. Further H. vitulus in various collections are of
questionable identity and need to be reexamined.
Differential diagnosis Also the distribution of Hexanchus vitulus and Hexan
chus nakamurai, and even of Hexanchus griseus should
UPPER TEETH be reviewed.
All tJu·ee species can be separated from each other by
The upper teeth of Hexanchus griseus and Notorhyn- their differences in their tooth morphology.
\I
Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites 155
Based on odontological characters the Hexanchidae can Sa Principal cusp bent distally in upper anterior
be grouped into two lineages : teeth . . . . . . . . . . . . . . . Hexanchus griseus
Group 1 Group 2 Sb Principal cusp distally inclined 6
UPPER TEETH 6a Mesial serrations absent on upper anterior and
- Mesial serration present - Mesial serration absent lateral teeth . . . . . . . Notorhynchus cepedianus
LOWER TEETH 6b Mesial serration present on upper anterior and
- 5 lateral teeth - 6 lateral teeth lateral teeth . . . . . . . . . . . . . . . . . . . . 7
- root low root high
7a Mesial serrations poorly developed on upper
anterior and anterolateral teeth. Hexanchus vitulus
The taxonomy of the hexanchid species is traditionally
strongly affected by the number of branchial arches, 7b Mesial serration well developed on upper
being considered an important systematic character by anterior and anterolateral teeth . . . . . . . . .
various authors. However, several authors also doubt the Hexanchus nakamurai
significance of this character (BASS, o' AUBREY & KlsT
NASAMY, 1975, HERMAN, HOVESTADT & HOVESTADT, 1 b Root compressed and low (C ;:::: 39 % of E) 8
1987). SHIRAI, 1992 investigated the origin of the
branchial arches in Hexanchiformes by extensive mor 8a 3 or more distal cusplets . . . . . . . . . . . 9
phological and anatomical studies and concluded :
within Hexanchiformes, Chlamydoselachus seems to be 9a Principal cusp of upper anterior and first late-
descent of a different lineage; Hexanchus is more close ral teeth strongly sigmoidal . Heptranchias perlo
ly related to Heptranchias, and two families Hexanchi
dae and Notorhynchidae can be recognized. These 9b Principal cusp of upper anterior and first
results largely conform with our odontological findings. lateral teeth inclined . . . . . . 10
WARD (1979) already introduced the terms "grisiform"
and "vituliform" to separate lower lateral teeth of fossil lOa Mesial serrations absent on upper latera-
hexanchid records. posterior teeth . . . . . 11
lla Mesial cusp lets present on upper latera-
posterior teeth . . . Heptranchias perlo
Odontological key to the hexanchid species
11 b Mesial cusp lets absent on upper latero
(The lower symphysial and the commissural teeth are posterior teeth . . . . . . Hexanchus griseus
excluded)
lOb Mesial serration present on upper latera
1a Root compressed and high (C ;:::: 39 % of E). 2 posterior teeth. . . . . . . . . . . . . . . . . . . 12
2a 7 or more distal cusplets on lower lateral teeth 12a Serration poorly developed on upper latera
.. . ·. . . . . . . . . . . . . . . Hexanchus griseus posterior teeth . . . . . . . Hexanchus nakamurai
2b Less than 7 distal cusplets on lower lateral l2b Serration well developed on upper latera-
teeth ... 3 posterior teeth. . . . . . . Hexanchus vitulus
3a 5 or more distal cusplets on lower lateral teeth 8b Less than 3 cusplets . . . . . . . . . . . . . . . 13
. .. ..... Notorhynchus cepedianus
13a Mesial cusplets present on lower lateral teeth
3b Less than 5 distal cusplets on lower lateral . . . . . . . . . . . . . . . . . H eptranchias perlo
teeth ... 4
13 b Mesial cusplets absent on lower lateral teeth . 14
4a 3 or more distal cusplets on lower lateral teeth
Uuveniles only) . . . . . . . . Hexanchus griseus 14a Mesial serration absent on lower lateral teeth
. . . . . . . . . . . . . . . . . . Hexanchus griseus
4b Less than 3 distal cusplets on lower lateral
teeth . . . . . . . . . . . . . . . . . . . . . . . . 5 14b Mesial serration present on lower lateral teeth . 15
II
156 J. HERMAN, M. HOVESTADT-EULER and D.C. HOVESTADT
15a Principal cusp clearly exceeds height of cus HERMAN, J., HOVESTADT-Euler, M. & HOVESTADT, D.C., 1987,
plets . . . . . . . . . . . . . . . Hexanchus vitulus Contributions to the comparative morphology of teeth and
other relevant ichthyodorulites in living supraspecific taxa of
Chondrichthyan fishes, Part A Selachii No.I Order : Hexan
15b Principal cusp does not exceed height of cus- chiformes, family : Hexanchidae. Ed. Stehmann, M. Bulletin
plets ..................................... Hexanchus nakamurai de I' Institut Royal des Sciences naturelles de Belgique, Biolo
gie, 57 : 43-56.
HOVESTADT,D.C. & HOVESTADT-Euler, M., 1993, Vasculariza
tion in Selachii. In : Elasmobranches et Stratigraphie. Her
man, J. & Van Waes, H. (eds.) Service Geologique de Belgi
Acknowledgements que, Professional Paper 1993/6, 264 : VTII + 260 pp.
SHIRAI, S., 1992, Identity of Extra Branchial Arches of
We would like to thank Mrs. M.N. FEINBERG, American Hexanchiformes (Pisces, Elasmobranchii). Bulletin of the
Museum of Natural History, New York, Dr. D. NOLF, Faculty of Fisheries, Hokaido University, 43 (I): 24-32.
lnstitut Royal des Sciences naturelles de Belgique, SPRINGER, S. & WALLER, R.A., 1969, Hexanclws vitulus, a
new sixgilled shark from the Bahamas. Bulletin of Marine
Brussels, Dr. M.E. ANDERSON, J.L.B. Smith Institute of
Science, 19: 159-174.
Ichthyology, Grahamstown, Dr. T. TANIUCHl, Depart
TANIUCHI, T. & TACHIKAWA, H., 1991, Hexanchus nakamurai,
ment of Fisheries, University Museum, University of
a Senior Synonym of H. vitulus (Elasmobranchii), with Notes
Tokyo, Mr. E. VANDERHOEFr, Collaborator B.G.S., Bms
on its Occurrence in Japan. Japanese Journal of Ichthyology,
sels for the loan of species at their disposal and Mr. J.C.
38 (1) : 57-60.
HOWE, and Miss S.J. RAREDON, Washington for pro
TENG, H.T., 1962, Classification and distribution of the
viding photographs of the jaws of Hexanchus vitulus
Chondrichthyes of Taiwan. Ogawa Print, Maizuru. 304 pp.
(Holotype and Paratype).
WARD, D.J., 1979, Additions to the fish fauna of the English
We also like to thanks Miss. F. LADEUZE, F.N.R.S., Palaeogene.3. A review of the Hexanchid sharks with a
Brussels as well as Miss. I. SILVA, Jacqmain, Brussels, description of four new species. Tertiary Research, London 2
for technical assistance. (3):111-129.
The SEM-photographs were taken by J. CILLIS, lnstitut
STEHMANN, M.
Royal des Sciences naturelles de Belgique, Brussels,
Institut fi.ir Seefischerei
and the photographs were printed by the crew of Minit
Bundesforschungsanstalt fi.ir Fischerei
Color Laboratorium (Brussels).
Palmaille 9
D-22767 Hamburg, Ge1many
HERMAN, J.
Service Geologique de Belgique
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