TAXONOMICAL CONSIDERATION ON GENERA OF
DELPHINIDAE*
MASAHARU NISHIWAKIINTRODUCTION

There are some difference in the considerations regarding separation and the
combination of the various genera of Delphinidae according to different authors.
According to the checklists by J.E. Gray, he separated them into three families
Balaenidae, Catodontidae and Delphinidae, in the suborder Cete in 1850, but hecorrected it to six families, Catodontidae, Ziphiidae, Platanistidae, Iniidae, Delphinidae
and Globicephalidae, in the section Denticeti in 1866. Some of the previous authors
after Gray have written on separation into families other than already established.
The separation considered differ according to the individual author however thereasons given by each are most reasonable, as for instance, some of the previous
authors have separated them into Kogiidae, Phocaenidae and Monodontidae (Delphinapteridae) as well as Physeteridae, Ziphiidae, Platanistidae and Delphinidae. There is veryclear reason for these separations, and the author could think it reasonable. Noneof them however, separated the Globicephalidae from the Delphinidae in the suborder
Odontoceti. If a genus of a family has some different characters from another generaof the family, it may be recognized as a subfamily or an individual family. The
author if possible does not wish to apply subfamily as a general principle. It isnecessary to consider, of cause, the genera is derived from what kind of ancestral
animals.
It is easy to understand that in the family Physeteridae, the subfamily Kogiinae
was separated with the subfamily Physeterinae, and then the subfamily Kogiinae wasmade an independent family Kogiidae. The author would like to induce separationsof the family Delphinidae as mentioned above.
The following names of the living genera were included in the family Delphhiidae
by recent authors. Delphinus, Stenella, Tursiops; Lagenorhynchus, Lissodelphis, Steno,
Sotalia, Cephalorhynchus, Globicephala, Pseudorca, Feresa, Grampus, Grampidelphis andOrcaella. These genera have one to ten species, so the family Delphinidae is the largest
family in the suborder Odontoceti. The author already recognized that Phocaena;
Phocaenoides and Neomeris were included in the family Phoocaenidae indepdendently
from the family Delphinidae.
It is considered that there are apparently two types in the family Delphinidae.
One has a pungent beak, numerous teeth and small in size, another has a beaklessblunt head, few teeth and moderate in size. The various characters of these types
must be studied.
Cephalorhynchus and Sotalia are considered in the first type, but the author has
no detailed descriptions on these genera, so the author with much regret is unable* Dedicated to Professor T. Ogawa for his sixtieth birthday93M. NISHIWAKI

94

to discuss on these genera.
BODY LENGTH AND NUMBER OF VERTEBRAE

It was clear that the total number of vertebrae, including cervical, dorsal (thoracic),
lumbar and caudal vertebrae, were different in each of the genera.

x17
90f-

0 0
6

so~

.,
....
"'

8

4 00 5

.0

2....
.,

" 70.,....

~

0

.0

E

z"

60~

x -70

I!!

•

13

10

0

16 ®
3
15

9

x

•

14

+

1 &.

so-

•

12

18

~

11

2

I

I

I

10

20

30

Body length in feetFig. 1. Relation between body length and number of vertebrae in various genera ofsmaller toothed whales.
Explanation of the marks in the figures.
The marks 0 are the genera with only the Atlas fused to the Axis; the marks •indicate those in witch the Atlas is fused with more than two other cervicals. The
genus Orcaella is shown with the mark @, and the mark 00 shows the genus Grampidelphis. The marks X are the genera of the family Phocaenidae, and the marks +are the genera of the family Monodontidae. The mark & shows the family Kogiidae.
The attached number of marks represent the name of the genera. 1 : Monodon, 2 :Delphinapterus, 3 : Orcaella, 4: Delphinus, 5: Stenella, 6: Lissodelphis, 7 : Steno, 8:
Lagenorhynchus, 9: Tursiops, 10: Feresa, 11 : Grampus, 12: Pseudorca, 13: Globicephala,
14: Glampidelphis, 15: Neomeris, 16: Phocoena, 17: Phocaenoides and 18: Kogia.

Fig. I shows that the total number of vertebrae, whether small or large, does
not affect the body length. The average of a number of species of each genera
are given in the figure, but as for the body length, the measurements of full grown
male have been given. Usually male is bigger than female in the suborder Odontoceti. According to this figure, the large sized genera have smaller number of

TAXONOMICAL CONSIDERATION ON DELPHINIDAE

95

vertebrae, as compared with the larger number of vertebrae in the smaller sized
genera. This suggests that each vertebral bone is bigger in the large sized genera.
These figures (Fig. I-Fig. 3) also show the positions of the genera of the families
Kogiidae, Monodontidae and Phcaenidae which are already separated from the family
Delphinidae by the previous authors.
FUSED BONES IN CERVICAL VERTEBRAE

The very important character is which of the seven cervical vertebrae are fused.
(As it is well known, there is no genus which has six or eight cervical vertebrae inthe order Cetacea.)
In the family Physeteridae, the Atlas is free, but the Axis to the seventh cervicalare all fused, but the all cervicals are fused in the case of the family Kogiidae. The
family ,Ziphiidae has fused cervicals, from the Atlas to the Axis or to the fourth. All
free cervical vertebrae are observed in the case of the family Monodontidae and thePlatanistidae.
In the case of the genera in the family Delphinidae, it is described that at least
the first and the second cervical vertebrae are fused together. Some authors
mention that "at least two bones are fused" but the author on examining thischaracter have found the following facts.
The names of the genera with only the Atlas and the Axis fused, are Delphinus,
Stenella, Lagenorhinchus, Tursiops, Lissodelphis, Steno and Orcaella (Cephalorhynchus andSotalia were not studied). The author observed, however, in this genera especiallyin the Stenella or the Delphinus, the third cervical became fused with the Axis after
growth. It seems that these cases have not occurred due to the hereditary nature,
but to the ageal changes. These seven genera are small in size and have a pungent
beak, except the genus Orcaella.
The genus Orcaella (Irawaddy dolphin) has a beakless blunt head, moderate
number of teeth (15-17/12-14) and small in size. They are very different incharacter from both types of the Delphinidae. Furthermore the Orcaella is generally
fluviatile and comparatively restricted in distribution. The author would first
like to separate this genus Orcaella from the family Delphinidae.
Another genera in the family Delphinidae have not only the Atlas and the Axis
fused but also the third or more cervical vertebrae fused to the Atlas. In the caseof the genus Feresa, the Atlas to the third cervicals are fused, and in the genus Grampus
the cervicals are fused from the Atlas to the fourth. The genera in which the Atlas
is fused to the sixth cervical vertebrae are the Globicephala, Pseudorca and Grampidelphis. These five genera have a beakless blunt head, fewer number of teeth (under
fifteen in a tooth row) and some of them reach moderate in size.
SHAPE OF SKULL

The characteristics of the skull are very important, and a most intricate methodof measurement is employed, however it would be too complicated to explain theM. NISHIWAKI

96

method here, therefore, in this paper only the length of the skull and the length of
the rostrum will be treated as the ratio of their breadth. The length of the skull
is the straight length from the middle of the occipital conuyles to the tip of the snout
when the skull is situated horizontally. By the breadth of the skull, the greatest
width of the skull is meant and this is usually equal to the breadth across the middleof the orbits. The length of the rostrum is obtained by measuring the base, and thisis almost equal to the length between antorbital notches.
Fig. 2 shows the relation between the length/breadth ratio of the skull and thelength/breadth ratio of the rostrum. In the figure the plotted points are arranged
from underleft to upperright. The open circles are the genera in which are Atlas
0

0
0

x
17

0

2.0 I-

9

x +2

-"'

"

.

+

::;

x

1.5 ~

0

16

•
12

~
~

0

•

10

El

15

14

i

.,

M

." •

0

•
II

13

'""'

1.0 ~

A
18

I

I

I

1.0

2.0

3.0

Length / breath ratio of roserum

Fig. 2. Relation between skull and snout on their slenderness in various genera ofsmaller toothed whales.

only is fused to the Axis, and the closed circles indicated those in which the Atlas
is fused more than three cervicals. There is one exception however and that is
the genus Orcaella shown with an open circle with a point. It is clearly separated
into two groups, the open circle group is the Delphinus type which have long slenderrostrum (over twice the breadth in length), and the closed circle group is the
Globicephala type which have short broad rostrum (1.5 times of breadth or less inlength). The long skull length of the Delphinus type group is mainly due to its
rostrum length, but in the Globicephala type group the brain case is wider. In thisfigure the genus Orcaella occupies a special position near the genus Neomeris of thefamily Phocaenidae.

97

TAXONOMICAL CONSIDERATION ON DELPHINIDAE

NUMBER OF MAXILLARY TEETH AND LENGTH OF ROSTRUM

It can be considered that the longer rostrum has more teeth than the shorter rostrum.
Fig. 3 shows the relation between the number of maxillary teeth and the length/
breadth ratio of the rostrum. In the figure the long rostrum generally has moreteeth. The genus Steno has the longest ratio of the rostrum but surprisingly the
number of teeth are relatively small (20-27 in each tooth row). This is caused by
the following reason. The teeth size is relatively large and the rostrum is comparatively slender. In this figure also the open circled genera have formed a group(relatively widely diffused) and the closed circle genera have formed another group.

0

7

3.0-

0

4

2.5

0

0

5

9

0

a

6

~ 2.0...

0

0

-·Z

8

•
10

0

17

x

..."'

x

2+e12
1

16

•

!#
14

11

®3

•

LO-

x

13

15

A
18
I

I

I

I

I

I

0

10

20

30

40

50

60

Number of teeth

Fig. 3. Relation between number of teeth and length breadth ratio of snout in various
genera of smaller toothed whales.

However the genus Grampidelphis has no maxillary teeth and does not belong toeither of the groups. This may be a reason for separating it into an individual
group.
The genera of the family Monodontidae and the Phocaenidae each form a different
group. The genus Orcaella also occupies a special position near the genus Neomeris.
In these two genera (Orcaella and Neomeris), the shape of the teeth are quite different,
but no discussion on the matter will be taken up here.
It is possible to discriminate them into groups by elaborating on the relationship of the foregoing elements, however the author has refrained from illustratingthem in figures, because it would be too difficult to explain their connection.

98

M. NISHIWAKICONCLUSION

Some taxonomical considerations are made on the reasons already mentioned above.
In the fourteen genera of the family Delphinidae, the six genera are accepted
as the Delphinus type, and the five genera are considered as the Globicephala type.
The genus Orcaella is being separated from the two types. The author considers
that the family Phocaenidae is already separated from the family Delphinidae by theprevious authors. The Delphinus type genera generally have a long slender beak(over twice the breadth in length of rostrum), numerous teeth (over 20 teeth in each
tooth row) and relatively small in size (under 13 feet). This type also has the cervical vertebrae with only the Atlas fused with the Axis. The genera of the Delphinus
type are Delphinus, Stenella, Lagenorhynchus, Tursiops, Lissodelphis and Steno ( Sotalia
and Cephalorhynchus may be included in this type, but these two genera are excluded
from this study because the available data was scanty). The author considers thesegenera should be included in the family Delphinidae.
The genus Orcaella should be separated from the family Delphinidae and independently form the new family Orcaellidae.
The Globicephala type genera generally have a beakless blunt head (under 1.6
breadth in length of skull), fewer teeth (under 15 in each tooth row) and some ofthem reach moderate in size (over 25 feet). Furthermore the cervical vertebraeof this type are recognized as having the Atlas fused not only with the Axis, but alsowith the third or more cervicals. The genera of the Globicephala type are Globicephala, Feresa, Pseudorca, Grampus and Grampidelphis, and these genera should be
separated from the family Delphinidae. The author would like to propose that thefamily Globicephalidae has come to the fore again and that these genera should belong
to this family.
Though the morphological characters should be examined very carefully,
differences which are too minor should not be considered in making. Neverthlessthe separation should be made with confidence, if the feature can be clearly differenciated. In the taxonomical consideration of animals, making too many species,
genera or families may be indiscreet, but using subfamilies are not an adequate
way also.
Each genus of the family Globicephalidae has its own special characters, but themost distinct feature in the majority of them is no teeth on the upper jaw. The
genus which has this feature is the Grampidelphis. The author would like to venture
to set up the new family Globidelphinidae.
As a conclusion, the author considers that the genera of the foregoing family
Delphinidae should be separated into the Delphinidae, Orcaellidae, Globicephalidae andGlobidelphinidae families.
The author in the following table shows a key to the living families of Odontoceti
through his examination of the characters of the genera.

TAXONOMICAL CONSIDERATION ON DELPHINIDAE

99

KEY TO THE LIVING FAMILIES OF ODONTOCETI
11 Tip of lower jaw ending an appreciable distance behind foremost part of head; blowhole
far forward on head.
2 1 Head massive, 1/4 to 1/3 of body length; functional teeth large, 18 to 28 pairs in number,confined to lower jaw; dorsal fin an ill-defined lump ; flipper rounded ; size large (30to 60 feet).
Physeteridae
22 Head l /6 of body length ; functional teeth small, slender and curved, 9 to 16 pairs confined
to lower jaw; dorsal fin well developed; flippers tapering; size small (9 to 13 feet).
Kogiidae
12 Lower jaw extending at least as far as tip of snout; blowhole some distance from tip ofsnout.
31 Two conspicurous grooves forming a V-shape on the surface of throat blubber; dorsal
fin present, considerably behind middle of body ; no notch in middle of hinder margin of
flukes.
:(iphiidae
3 2 No grooving on throat; dorsal fin when present at or near middle of body; notch in
middle of hinder margin of flukes.
41 Seven cervical vertebrae all separate from one another.
51 Dorsal fin absent or rudimentary; beak absent; inhabits Arctic regeon.
Monodontidae
52 Dorsal fin present but almost low ; beak extremely long ( l /6 to l /7 of body length) ;inhabits tropical fresh water ; teeth very numerous in upper and lower jaws.
Platanistidae
42 Two or more cervical vertebrae fused.
61 Only atlas and axis fused.
71 Beak long and narrow (breath of snout less than 1/2 of its length) ; more than 20 teeth
in each row of upper jaw; size small (less than 13 feet).
Delphinidae
72 Beak absent ; less than 20 teeth in each row of upper jaw ; size small.
Orcellidae
6 2 Not only atlas and axis fused, but also third or more cervical vertebrae fused.
81 Head without distinct beak; each row of upper teeth more than 15; body length
less than 8 feet.
Phocaenidae
82 Head without distinct beak; each row of upper teeth less than 15 ; body length
more than 8 feet.
91 Teeth present in upper jaw.
Globicephalidae
92 Teeth absent in upper jaw.
Globidelphinidae

REFERENCES
ANDERSON, J. (19-). Comprising and account of the Zoological results of the two Expeditions to \'V'estern
Yunnan in 1868 and 1875, and a monograph of the two Cetacean genera, Platanista and Orcella. Vol.
I-II.
ANDREWS, R. C. (1911). A new porpoise from Japan. Bull. Amer. Mus. Nat. His. Vol. 30.
BEDDARD, F. E. (1900). A book of whales.
CHASEN, F. N. (1940). A handlist of Malaysian mammals.
ELLERMAN, J. R. & T. C. S. MoRRISON-SCOTT. (1951). Checklist of Palaearctic and Indian Mammals,
1758 to 1946.
- - (1955). Supplement to Chasen (1940). A handlist of Malaysian Mammals.
ELLERMAN, J. R., T. C. S. MoRRISON-ScoTT & R. \;\'.HAYMAN (1953). Southern African Mammals 1758
to 1931.
GRAY J. E. (1950). Catalogue of the specimens of Mammalia in the collection of the British Museum.
Part 1. Cetacea.
- - (1866). Catalogue of Seals and Whales in the British Museum. Second Edition.
HALL, E. R. & Kl E. KELSON (1959). The mammals of North America, Vol. II.
MATSUURA, Y. (1953). The sea mammals (in Japanese). Rev. Rev. Ocean. Sci. Vol. 7.
MILLER, Jr., G. S. & R. KELLOGG. (1955). List of North American Recen Mammals, U.S. Nat. Mus.

100

M. NISHIWAKI

NrsHIWAKI, M. (1957). A list of marine mammals found in the seas adjacent to Japan (mainly in Japanese).
Szm. Desc. Sci. Fisheries.
NoRMAN, J. R. & F. C. FRASER. (1937). Giant fishes, whales and dolphins.
OGAWA, T. (1936-1937). Studies on the Odontoceti in Japan (in Japanese). Plants and Animals, Vol. 4,
No. 7-Vol. 5, No. 3.
- - (1937). A list of Odontoceti in Japan (in Japanese). Annual Rep. Saito-Hoonkai, No. 12.
- - (1939). Additional description on he small toothed whales Cogia and Steno (in Japanese). Plants
and Annimals. Vol. 7, No. 7.
- - (1940). On the Grampus (Risso's dolphin) (in Japanese). Plants and Animals, Vol. 8, No. 3.
POOLE, A. J. & V. S. SCHANTZ (1942). Catalog of the type specimens of mammals in the United States
National Museum, includingthe biological surveys collection. Smithsonian Inst. U. S. Nat. Mus. Bull.
178.
SIMPSON, G. G. (1945). The principles of classification and a classification of mammals. Bull. Amer. Abts.
Nat. His. Vol. 85.
ToMILIN, A. G. (1957). Animals around U. S. S. R. Vo! IX, Cetacea. (in Russian).
TRUE, F. W. (1889). Contribution of the natural history ofCetacea. A Review of the family Delphinidae.
U. S. Nat. Mus. Bull. 36.
·wrNGE, H. (Translated by E. DEICHMANN & G. M. ALLEN) (1942). The interrelationship of the Mammalian genera, Vol. III, Cetacea.

~Lissodel/Jhis

Delphinus

D~~

MonodonGenus nameandout line of
typical body form

8

8

71/2

7

18

12

Body
lengthin feet.

,..,,-:-:~--~~

c-:=Si~
~

.

..

i.

~

-...........

···(<

·~

;::_, :-_-:-:----- _~-: '1<·.

Ventral viewof skullof typical species

7
(?)

(0)

7
(2)
D : 14-15 (5)L : 29-30
Ca: 37-39

c :

88-90

7
(2)
D : 14-16 (4)L : 21-24
Ca: 31-35

c :

68-81

c : 7 (2)
D : 14-16 (4)L : 21-23
Ca: 31-34

73-76

c : 7 (2)
D : 13-14 (8)L : 13-14
Ca: 27-28

62-63

D
L
Ca

c

50-52

7
(0)
D : I 1-12 (?)
L : 6-10
Ca: 26-27

c :

50-55

Detailed number with)number of fused cer( vicals & number of two
headed ribs

Number of vertebrae

v

IV

III

II

I

v

IV

1-2
8
6
3
2-3

4
I

I

9
7

I

II
III

IV

v

3
0-1

8
6

2

1-2
6-9
4-5
2-4
2-4

1-2
5-8
4-6
2-4
2-3

1-2
7-9
6-7
2-4
1-2

I
II
III

v

IV

I
II
III

v

IV

III

II

I

v

IV

II
III

I

(Included metacarpals)

Number ofphalangeal bones

40-43
42-46

34-56
34-56

47-65
47-65

15-17
12-14

8-10
8-10

0

2. 18

2.40

2.93

I. 10

1.50

I .31

2. 17

2.00

2.22

1.41

I. 79

1.66

I of skull

Length/breath
ratio(in typical species)of rostrum

I

Upper
.
Lower fa side

Dentition

Appendix: Body form and osteological characters on the various genera of smaller toothed whales.

z

-0

tri

~

~
~
~
~

b

z
z0

~0

6

<fJ

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0

0

~

0

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......

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'--"

•

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C/1
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~

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8
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~ 8, ci.

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/?

--=~

12

9

8

Body
lengthin feet

~

l

-

~
.

--=-,Jl~Jg~_,,.. ~.li?'-'.i

Ventral viewof skullof typical species"'<'______./ --------- -

./('

p~

~

C ~'\::-----------~\

Feresa*

18

30

8

-

_______ _________j.

;; A- -:-: J:'\_ _ '.
E®
.

~
~

(2)

:

Ca:26-29

L

L
Ca

D

c

Ca

D
L

c

50-52

7
(6)
10
(6)
9-10
22-24

7
(4)
ll-12 (6)1021-24

~a: 32~33

g : l~

67-68

((~))

g ; 12._'.'14
m
17-19

7
(2)
D : 14-15 (6)L : 18-22
Ca: 38-41

c :

D
L

61-66

50

7

13 (4-5)
15-16
Ca: 30-31

c

73-92

66

Detailed number with)number of fused cer( vicals & number of two
headed ribs

Number of vertebrae

1--~~~~~~~~~~~-t--~~-t--~~~~~~--+~~~

Tursiops

·.:_~

SteCo
...__( _______ _Genus nameandout line ot
typical body form

Appendix (continued)

2

V:

22-45
22-45

20-27
20-27

2.02

3.18

I

I

I

1.74

2.25

Length/breath
ratio(in typical species)
U ppcr of a sidcl
I Lowerof rostrum of skull
Dentition

2-3

1-2

v

1

5
2

III
IV

l

6

I
II

v

IV

III

2

6-7
4-5
3-4
2-3

I

II

lg ~=~
It ~=~

I

--~~-

V

8-11

8-ll

10-13
10-13

10 - 12
10-13

I

l. 49

l.36

1.84

--~~---~--

I

I

l.62

1.36

l.62

-~~-~!~~~--+-~~~

20 26
rgIV 2-3~=~ tl -20---2- - I 2.32
I 2.04
6

1-2

2-3

IV:

I

6

1-2
10

3
2

3
8-9
6-7

III

II

I

II
III
VI:
V:

I

(Included metacarpals)

Numrbe ofphalangeal bones

-

:;-::

~

::r:

[ /).

-

~

z

0

""

----~----.....___

~\

13

7

6

13

28

Body
lengthin feet--- --·

~

~~\j

.

Phocaenoides /~

~---~

~

,,---------

Neomeris~

Globicej1hala

Genus nameandout line of
typical body form

Appendix (continued)-~·

I~ .v'~ "{ .

~~'C:-·':~i~,-- . n

•" \.

'l
-,.~
· e:~J /.

··~Ventral viewof skullof typical species

---

(7)
7
D : 12-13 (8)L : 10-12
Ca: 24--:;27

c :

50-51

7
(7)
D : 15-18 (12)
L : 24-27
Ca: 44-49

c :

92-98

7
(6)
D : 12-14 (JO)L : 14-17
Ca: 27-32

c :

62-66

7
(5)
J) : 13-14 (11)
L : 12-13
Ca: 25-31

c :

58-63

7
(6)
D : 12-13 (6)L : 17-18
Ca: 30-31

c :

68-69

7
(6)
]) : 11-12 (6)L : 12-14
Ca: 28-29

c :

57-60

(Detailed number with)number of fused cervicals & number of two
headed ribs

Number of vertebrae

v

I
II
III
IV

v

I
II
III
IV

v

IV

III

I
II

v

IV

III

I
II

v

IV

III

I
JI

v

I
II
I II
IV

2
5-8
4-8
4-8
2-7

I
6
4-.5
1-2
0-1

I- 3
5-10
5- 8
2- 6
1- 3

2
5-7
5-6
3
2

2
8-10
5- 8
3- 5
I

3- 4
9-14
9-11
2- 3
I- 2

(Included metacarpals)

Number ofphalangeal bones

I

6-8
9-16

23-27
23-27

23-27
23-27

15-19
L'i-19

7-12
7-12

2-7

()

0. 79

l. 47

I .39

1.03

1.04·

1.30

I

I

1.03

2.10

I. 7;)

I. 51

1.25

1.50

I of skull(in typical species)

ratio

Length/breathof rostrum

I

Upper f"<l
Lower
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