TAXONOMICAL CONSIDERATION ON GENERA OF DELPHINIDAE*

Transcription

1 TAXONOMCAL CONSDERATON ON GENERA OF DELPHNDAE* MASAHARU NSHW AK NTRODUCTON There are some difference in the considerations regarding separation and the combination of the arious 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 15, but he corrected it to six families, Catodontidae, Ziphiidae, Platanistidae, niidae, Delphinidae and Globicephalidae, in the section Denticeti in 1. Some of the preious authors after Gray hae written on separation into families other than already established. The separation considered differ according to the indiidual author howeer the reasons gien by each are most reasonable, as for instance, some of the preious authors hae separated them into Kogiidae, Phocaenidae and Monodontidae (Delphinapteridae) as well as Physeteridae, Ziphiidae, Platanistidae and Delphinidae. There is ery clear reason for these separations, and the author could think it reasonable. None of them howeer, separated the Globicephalidae from the Delphinidae in the suborder Odontoceti. f a genus of a family has some different characters from another genera of the family, it may be recognied as a subfamily or an indiidual family. The author if possible does not wish to apply subfamily as a general principle. t is necessary to consider, of cause, the genera is deried from what kind of ancestral animals. t is easy to understand that in the family Physeteridae, the subfamily Kogiinae was separated with the subfamily Physeterinae, and then the subfamily Kogiinae was made an independent family Kogiidae. The author would like to induce separations of the family Delphinidae as mentioned aboe. The following names of the liing genera were included in the family Delphhiidae by recent authors. Delphinus, Stenella, Tursiops; Lagenorhynchus, Lissodelphis, Steno, Sotalia, Cephalorhynchus, Globicephala, Pseudorca, Feresa, Grampus, Grampidelphis and Orcaella. These genera hae one to ten species, so the family Delphinidae is the largest family in the suborder Odontoceti. The author already recognied that Phocaena; Phocaenoides and Neomeris were included in the family Phoocaenidae indepdendently from the family Delphinidae. t is considered that there are apparently two types in the family Delphinidae. One has a pungent beak, numerous teeth and small in sie, another has a beakless blunt head, few teeth and moderate in sie. The arious 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 birthday 93

2 94 M. NSHWAK to discuss on these genera. BODY LENGTH AND NUMBER OF VERTEBRAE t was clear that the total number of ertebrae, including cerical, dorsal (thoracic), lumbar and caudal ertebrae, were different in each of the genera. x 17.,.... "'.,... "....,. E " so x -7 1 x f- 7- so- 1 9!! &. 1 1 Body length in feet Fig. 1. Relation between body length and number of ertebrae in arious genera of smaller toothed whales. Explanation of the marks in the figures. The marks 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 cericals. The genus Orcaella is shown with the and the mark 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, : Delphinapterus, 3 : Orcaella, 4: Delphinus, 5: Stenella, : Lissodelphis, 7 : Steno, : Lagenorhynchus, 9: Tursiops, 1: Feresa, 11 : Grampus, 1: Pseudorca, 13: Globicephala, 14: Glampidelphis, 15: Neomeris, 1: Phocoena, 17: Phocaenoides and 1: Kogia. Fig. shows that the total number of ertebrae, whether small or large, does not affect the body length. The aerage of a number of species of each genera are gien in the figure, but as for the body length, the measurements of full grown male hae been gien. Usually male is bigger than female in the suborder Odontoceti. According to this figure, the large sied genera hae smaller number of

3 TAXONOMCAL CONSDERATON ON DELPHNDAE 95 ertebrae, as compared with the larger number of ertebrae in the smaller sied genera. This suggests that each ertebral bone is bigger in the large sied genera. These figures (Fig. -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 preious authors. FUSED BONES N CERVCAL VERTEBRAE The ery important character is which of the seen cerical ertebrae are fused. (As it is well known, there is no genus which has six or eight cerical ertebrae in the order Cetacea.) n the family Physeteridae, the Atlas is free, but the Axis to the seenth cerical are all fused, but the all cericals are fused in the case of the family Kogiidae. The family,ziphiidae has fused cericals, from the Atlas to the Axis or to the fourth. All free cerical ertebrae are obsered in the case of the family Monodontidae and the Platanistidae. n the case of the genera in the family Delphinidae, it is described that at least the first and the second cerical ertebrae are fused together. Some authors mention that "at least two bones are fused" but the author on examining this character hae 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 and Sotalia were not studied). The author obsered, howeer, in this genera especially in the Stenella or the Delphinus, the third cerical became fused with the Axis after growth. t seems that these cases hae not occurred due to the hereditary nature, but to the ageal changes. These seen genera are small in sie and hae a pungent beak, except the genus Orcaella. The genus Orcaella (rawaddy dolphin) has a beakless blunt head, moderate number of teeth (15-17/1-14) and small in sie. They are ery different in character from both types of the Delphinidae. Furthermore the Orcaella is generally fluiatile and comparatiely restricted in distribution. The author would first like to separate this genus Orcaella from the family Delphinidae. Another genera in the family Delphinidae hae not only the Atlas and the Axis fused but also the third or more cerical ertebrae fused to the Atlas. n the case of the genus Feresa, the Atlas to the third cericals are fused, and in the genus Grampus the cericals are fused from the Atlas to the fourth. The genera in which the Atlas is fused to the sixth cerical ertebrae are the Globicephala, Pseudorca and Grampidelphis. These fie genera hae a beakless blunt head, fewer number of teeth (under fifteen in a tooth row) and some of them reach moderate in sie. SHAPE OF SKULL The characteristics of the skull are ery important, and a most intricate method of measurement is employed, howeer it would be too complicated to explain the

4 9 M. NSHWAK 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 horiontally. By the breadth of the skull, the greatest width of the skull is meant and this is usually equal to the breadth across the middle of the orbits. The length of the rostrum is obtained by measuring the base, and this is almost equal to the length between antorbital notches. Fig. shows the relation between the length/breadth ratio of the skull and the length/breadth ratio of the rostrum. n the figure the plotted points are arranged from underleft to upperright. The open circles are the genera in which are Atlas x "' ". ::; i M '""' 1.5 x El ,. " 13 + x A Length / breath ratio of roserum Relation between skull and snout on their slenderness in arious genera of Fig.. smaller toothed whales. only is fused to the Axis, and the closed circles indicated those in which the Atlas is fused more than three cericals. There is one exception howeer and that is the genus Orcaella shown with an open circle with a point. t is clearly separated into two groups, the open circle group is the Delphinus type which hae long slender rostrum (oer twice the breadth in length), and the closed circle group is the Globicephala type which hae short broad rostrum (1.5 times of breadth or less in length). 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. n this figure the genus Orcaella occupies a special position near the genus Neomeris of the family Phocaenidae.

5 TAXONOMCAL CONSDERATON ON DELPHNDAE 97 NUMBER OF MAXLLARY TEETH AND LENGTH OF ROSTRUM t 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. n the figure the long rostrum generally has more teeth. The genus Steno has the longest ratio of the rostrum but surprisingly the number of teeth are relatiely small (-7 in each tooth row). This is caused by the following reason. The teeth sie is relatiely large and the rostrum is comparatiely slender. n this figure also the open circled genera hae formed a group (relatiely widely diffused) and the closed circle genera hae formed another group a Z... "' 3.- LO- 1!# 14 A 1 1 +e x x 1 3 Number of teeth Fig. 3. Relation between number of teeth and length breadth ratio of snout in arious genera of smaller toothed whales. Howeer the genus Grampidelphis has no maxillary teeth and does not belong to either of the groups. This may be a reason for separating it into an indiidual 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. n 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. t is possible to discriminate them into groups by elaborating on the relationship of the foregoing elements, howeer the author has refrained from illustrating them in figures, because it would be too difficult to explain their connection.

6 9 M. NSHWAK CONCLUSON Some taxonomical considerations are made on the reasons already mentioned aboe. n the fourteen genera of the family Delphinidae, the six genera are accepted as the Delphinus type, and the fie 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 the preious authors. The Delphinus type genera generally hae a long slender beak (oer twice the breadth in length of rostrum), numerous teeth (oer teeth in each tooth row) and relatiely small in sie (under 13 feet). This type also has the cerical ertebrae 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 aailable data was scanty). The author considers these genera 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 hae a beakless blunt head (under 1. breadth in length of skull), fewer teeth (under 15 in each tooth row) and some of them reach moderate in sie (oer 5 feet). Furthermore the cerical ertebrae of this type are recognied as haing the Atlas fused not only with the Axis, but also with the third or more cericals. 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 the family Globicephalidae has come to the fore again and that these genera should belong to this family. Though the morphological characters should be examined ery carefully, differences which are too minor should not be considered in making. Neerthless the separation should be made with confidence, if the feature can be clearly differenciated. n 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 the most 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 enture 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 and Globidelphinidae families. The author in the following table shows a key to the liing families of Odontoceti through his examination of the characters of the genera.

7 TAXONOMCAL CONSDERATON ON DELPHNDAE 99 KEY TO THE LVNG FAMLES OF ODONTOCET 1 1 Tip of lower jaw ending an appreciable distance behind foremost part of head; blowhole far forward on head. 1 Head massie, 1/4 to 1/3 of body length; functional teeth large, 1 to pairs in number, confined to lower jaw; dorsal fin an ill-defined lump ; flipper rounded ; sie large (3 to feet). Physeteridae Head l / of body length ; functional teeth small, slender and cured, 9 to 1 pairs confined to lower jaw; dorsal fin well deeloped; flippers tapering; sie small (9 to 13 feet). Kogiidae 1 Lower jaw extending at least as far as tip of snout; blowhole some distance from tip of snout. 3 1 Two conspicurous grooes 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 No grooing on throat; dorsal fin when present at or near middle of body; notch in middle of hinder margin of flukes. 4 1 Seen cerical ertebrae all separate from one another. 5 1 Dorsal fin absent or rudimentary; beak absent; inhabits Arctic regeon. Monodontidae 5 Dorsal fin present but almost low ; beak extremely long ( l / to l /7 of body length) ; inhabits tropical fresh water ; teeth ery numerous in upper and lower jaws. Platanistidae 4 Two or more cerical ertebrae fused. 1 Only atlas and axis fused. 7 1 Beak long and narrow (breath of snout less than 1/ of its length) ; more than teeth in each row of upper jaw; sie small (less than 13 feet). Delphinidae 7 Beak absent ; less than teeth in each row of upper jaw ; sie small. Orcellidae Not only atlas and axis fused, but also third or more cerical ertebrae fused. 1 Head without distinct beak; each row of upper teeth more than 15; body length less than feet. Phocaenidae Head without distinct beak; each row of upper teeth less than 15 ; body length more than feet. 9 1 Teeth present in upper jaw. 9 Teeth absent in upper jaw. Globicephalidae Globidelphinidae REFERENCES ANDERSON, J. (19-). Comprising and account of the Zoological results of the two Expeditions to \'V'estern Yunnan in 1 and 175, and a monograph of the two Cetacean genera, Platanista and Orcella. Vol. -. ANDREWS, R. C. (1911). A new porpoise from Japan. Bull. Amer. Mus. Nat. His. Vol. 3. BEDDARD, F. E. (19). A book of whales. CHASEN, F. N. (194). A handlist of Malaysian mammals. ELLERMAN, J. R. & T. C. S. MoRRSON-SCOTT. (1951). Checklist of Palaearctic and ndian Mammals, 175 to (1955). Supplement to Chasen (194). A handlist of Malaysian Mammals. ELLERMAN, J. R., T. C. S. MoRRSON-ScoTT & R. \;\'.HAYMAN (1953). Southern African Mammals 175 to GRAY J. E. (195). Catalogue of the specimens of Mammalia in the collection of the British Museum. Part 1. Cetacea. -- (1). Catalogue of Seals and Whales in the British Museum. Second Edition. HALL, E. R. & Kl E. KELSON (1959). The mammals of North America, Vol.. MATSUURA, Y. (1953). The sea mammals (in Japanese). Re. Re. Ocean. Sci. Vol. 7. MLLER, Jr., G. S. & R. KELLOGG. (1955). List of North American Recen Mammals, U.S. Nat. Mus.

8 1 M. NSHWAK NrsHWAK, M. (1957). A list of marine mammals found in the seas adjacent to Japan (mainly in Japanese). Sm. Desc. Sci. Fisheries. NoRMAN, J. R. & F. C. FRASER. (1937). Giant fishes, whales and dolphins. OGAWA, T. ( ). Studies on the Odontoceti in Japan (in Japanese). Plants and Animals, Vol. 4, No. 7-Vol. 5, No (1937). A list of Odontoceti in Japan (in Japanese). Annual Rep. Saito-Hoonkai, No (1939). Additional description on he small toothed whales Cogia and Steno (in Japanese). Plants and Annimals. Vol. 7, No (194). On the Grampus (Risso's dolphin) (in Japanese). Plants and Animals, Vol., No. 3. POOLE, A. J. & V. S. SCHANTZ (194). Catalog of the type specimens of mammals in the United States National Museum, includingthe biological sureys collection. Smithsonian nst. U. S. Nat. Mus. Bull. 17. SMPSON, G. G. (1945). The principles of classification and a classification of mammals. Bull. Amer. Abts. Nat. His. Vol. 5. ToMLN, A. G. (1957). Animals around U. S. S. R. Vo! X, Cetacea. (in Russian). TRUE, F. W. (19). Contribution of the natural history ofcetacea. A Reiew of the family Delphinidae. U. S. Nat. Mus. Bull. 3. wrnge, H. (Translated by E. DECHMANN & G. M. ALLEN) (194). The interrelationship of the Mammalian genera, Vol., Cetacea.

9 Appendix: Body form and osteological characters on the arious genera of smaller toothed whales Length/breath ratio <fj b tri - - Genus name and out line of typical body form Body length in feet Ventral iew of skull of typical species ( Number of ertebrae Detailed number with) number of fused cericals & number of two headed ribs Number of phalangeal bones (ncluded metacarpals) Dentition Upper. (in typical species) Lower fa side of rostrum of skull Monodon 1 ;::_, :-_-:-:----- _-: '1<. (< i c : 7 () D : 1-1 (?) L : -1 Ca: -7 V D c D L Ca 7 () (?) V c : 7 () D : () L : Ca: 7- V 3-1 Delphinus 7 1 / c : 7 () D : 14-1 (4) L : 1-3 Ca: V c-:=si -1 c : 7 () D : 14-1 (4) L : 1-4 Ca: V Lissodel/Jhis,..,,-:-:-- -9 c : 7 () D : (5) L : 9-3 Ca: V

10 j "" -[/). ::r: :;-:: - " :;-' g > "'., E:?f, ci. '--"...,.,..., "g a? "' :l '(;;' """ cc ;';] <...; :l.,., 5.."""' " c.,.., " '< "' < > g :::: "'"'..., " & "' '--' "'.,..,., ::;; "' "' 5 llq ;:?;" O"' "' :l - s. "'., C/1 e ::r - - "' :.E [ g, s: ;:o"' f,l "O., "' (")., (").., ::ri - ::r (") Genus name and out line ot typical body form SteCo... (.:_--= Tursiops /? Appendix (continued) Body length in feet 9 Ventral iew of skull of typical species _,,...li?'-'.i --=-,Jl g J.- l ( Number of ertebrae Detailed number with) number of fused cericals & number of two headed ribs c D L Ca: 1---t---t () 13 (4-5) c : 7 () D : () L : 1- Ca: 3-41 Numrbe of phalangeal bones Length/breath Dentition ratio (in typical species) U ppcr of a sidcl (ncluded metacarpals) Lower of rostrum of skull V: V: V: V: g ; 1._'.'14 m rg = tl L : V -3 - Ca:-9 V 1- Feresa*./(' !--+- C./ g : l (()) lg = l. "'<' 1-13 '\:: \ a: 333 t = p 3 1 '. E. \. - ;; A -:: :' - - J 5-5 c 7 (4) D ll-1 () L 1 Ca c 7 () D 1 () L 9-1 Ca -4 V V l ll -11 l l. 49 l.

11 Appendix (continued) Genus name Body Ventral iew Number of ertebrae Number of Length/breath and Dentition ratio phalangeal bones out line of length of skull (Detailed number with) (in typical species) in feet of typical species number of fused cer- Upper f "<l typical body form icals & number of two (ncluded metacarpals) Lower a si e headed ribs of rostrum of skull Globicej1hala 13 'l c : 7 () 9-14 () ;;! -,. " \.. e:j / Ca: -9 - ]) : 11-1 () L : 1-14 V ;:.<: ---. n c : 7 () J , 5 D : 1-13 () t"' L : 17-1 V ' Ca: 3-31 C:- ':i -.' "{. Neomeris 5-3 t::j,, c : 7 (5) ti:: J) : (11) L : 1-13 V 3 L'i-19 >..., --- Ca: c : 7 () D : 1-14 (JO).39. 7;) b L : Ca: 7-3 V Phocaenoides / c : 7 (7) D : 15-1 (1) \ L : 4-7 V Ca: "' '.; ti l t>:j c : 7 (7) 5- - D : 1-13 () 4- L : 1-1 V Ca: 4--:; <.>:>