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Retour à la page d'accueil  BIPEDIA  BIPEDIA n° 11

BIPEDIA 11.1
ON THE ORIGINS OF WHALES AND DOLPHINS
FROM AN ARCHAIC MARINE FORM

Première publication : juin 1994, mise en ligne : vendredi 27 juin 2003, François de Sarre


 The fish form of the CETACEA is not surprising at all for animals which swim all their life in the ocean. In some way, it is even convenient for the taxonomist, because the ancestors of the CETACEA might have evolved from any branch of the anterior Mammals up to their today hydrodynamic shape and configuration...

 

Morphology

 Simple suspension in the water, without moving, has already been put into effect by a spherical form of the body, like in jellyfishes or in some algae.

 As the oceanic creature tries to move, the things become a lot more complicated... The animal’s body is now thrusted against the water surface, through the action of the Archimede’s forces !

 So, if the creature really attempts to keep itself steadily sunk in the water, then it must actively fight against the natural tendency of its body to ascend and to break surface : otherwise, the animal only floats !

 The anatomical structure of the whales, in the same way as the corresponding structures in a fish or in an ichthyosaur, are obliged to yield to the needs of a straight horizontal locomotion through the aquatic milieu. With one big difference between fish and CETACEA with the latter, the flipper-tail knocks up and down, while the fish-tail curves only laterally in the water.

 According to this, there is thus a merely superficial resemblance of the CETACEA to the fish, surely best pronounced in the external form of the head...

 The CETACEA neck is short or not distinguishable ( the 7 neck vertebrae are short or are fusing in one another : they are not freely movable like in other mammals ). The extremity of the snout is not necessarily sharp-pointed, rather somewhat well-rounded ( like in fish ), for the best possible "high speed" penetration through the water. In whales and dolphins, moreover, the flattened and compressed head also serves to reverse the upward or downward progression.

 Since, this peculiar character of a smooth-truncated head in whales, correlated with the flattening of the whole rostrum and with the strong development of the trunk musculature ( in order to allow the "dolphin"swim ), leads us to think that these are indeed among primordial features in the CETACEA ancestry !

 In such a sense, the antecedents of the whales could not, for instance, have been in possession of a large, sharp-pointed snout, as suggested ( fig. 1 ) by the reconstitutions of Basilosaurus cetoides or of Ambulocetus natans.

 The character of a "pointed" snout, resembling the snout of a crocodile, with nostrils at the tip, is rather a phylogenetically derived feature, as also suggested by stages of the foetal development in the whales.

 

Anatomy

 Similitudes in the fossils and in the modern representatives of the CETACEA groups, are surely found in the shape and function of the auditory bones, in the dentition or in the development of mighty jaws, regarding the manners to retain a prey with their teeth and to gobble it up without masticating... Furthermore, some whales developed specific structures like the whalebone sieve.

 In that sense that they do not masticate, the CETACEA resemble more the dinosaurs ( or water reptiles like the crocodiles, the plesiosaur or the ichthyosaur ) than the other mammals.

 In my opinion, a fossil like the Ambulocetus, recently found in Pakistan by Hans THEWISSEN of the Northeastern Ohio College of Medicine and his team, is neither related to the ARCHEOCETI ( allegedly thought to be the ancestors of the whales ) nor to the PINNIPEDIA ( otaries and seals ) that are connected with the plantigrade bears and with the originally bipedal mammals...

 I would propose a special taxon, AMBULOCETI, for the genus Ambulocetus, with the characteristics of a quadrupedal big-footed amphibious creature, probably originated from some undifferenced CREODONTA ( see the tabloid on fig. 4 ). Ambulocetus used to catch its prey in diving with the help of its strong hind legs. He also used flexion-extension ( in a vertical plane ) of its back musculature to progress among the surface, as seals and otaries also do. The tail had more of a rudder function.

 Ambulocetus was tramping on flat-bottom seas and pools, walked on land in the art of otaries by bending his webbed hands and feet outsidewards. The AMBULOCETI had certainly no particular disposition to remain during all of his life in the water and even not to rush into the conquest of the ocean’s immensity by transforming into whales...

 The AMBULOCETI surely became extinct in the course of the Tertiary period, without leaving any descent...

FIG. 4
PHYLOGENETICAL SCALE OF THE EVOLUTION OF BIG WATER MAMMALS
 
REFERRING to INITIAL BIPEDALISM and to DE SARRE 1993,
THE ABOVE TAXA DEVELOPED FROM THE ANCESTRAL WATER FORMS WITH AN ERECT BODY POSTURE ( ERECTA ) - THEY EVOLVED
on the right side of the tabloid ) INTO THE CETACEA THAT LOST THEIR HIND LEGS ( = APODY )

 

Particularities of the CETACEA

 Before we come to speak of the caudal fin with its 2 horizontal flukes, let us consider some other typical characteristics of the whales.

 The auditory bones ( hammer, anvil and stirrup-bone ) are highly modified, the tympanics are shell-like and loosely attached to the skull : these modifications are done to adapt in the conditions of audition among the water surface. Similar adaptations may have occurred in other aquatic lineages and are a simple result of convergence : they cannot be invoked in phylogenetical purposes, as the palaeontologists claim.

 The nostrils ( = blow holes ) have been shifted in whales to the upper side of the head, at some distance from the tip of the snout of beak. The blow holes are either 2 longitudinal slits in the MYSTACOCETI ( whalebone whales ), or a single crescentic slit in the ODONTOCETI ( toothed whales ).

 The nasal canals ( see fig. 2 ) pass nearly vertically downwards in front of a lofty brain-case which is home the big globulous encephalon.

 The larynx and epiglottis form a tube through the oesophagus, so the blow holes become continuous with the windpipe and the lungs. The mouth is being used solely for feeding, as in newly born mammals, but not in adults, which can breathe through either the nose or the mouth. In fact, this system is a particular feature of the whales that indicates a very ancient adaptation to life in the water. It is not to be observed in the allegedly "prior" forms, like the AMBULOCETI or the ARCHEOCETI.

 

The question of the caudal fin

 The palaeontologists usually claim that the CETACEA developed during the Eocene period. Their ancestors were allegedly quadrupedal land mammals. Through a transitional form that may have looked like a seal, then losing legs and pelvis ( vestiges of which, as well as vestiges of femurs, are still embedded in the flesh of the baleens ), they evolved into the typical whalebone ( MYSTACOCETI ) or toothed ( ODONTOCETI ) whales.

 The problem is not only how the CETACEA obtained a big globulous brain from antecedents that may have looked like Ambulocetus, but also how they develop their typical caudal fin ?

 It must first be said that the "tail" ( as it is commonly called ) of the whales, is in reality a sympodium attached to the extremity of it.

 The tail is only the prolongation of the body vertebrae. The 2 horizontal flukes are boneless fleshy appendices. They are supported in the middle by the tail.

 As expressed by mammalogist Serge FRECHKOP in 1944, the lower skin surface of the CETACEA flukes is homologous to our plantar foot surface !

 Dr. FRECHKOP further remarks that the caudal fin of the CETACEA works in a similar way like a motor-boat propeller, i.e. in a helicoidal motion, with the only restriction that the rotation is, evidently, not complete !

 This fact can surely be explained by the original disposition of their 2 legs and feet ( see fig. 3 ) before they began to disappear, as the specific tail muscles parallely developed...

 Similar patterns are certainly due to explain the development of the caudal fm in the SIRENIA and in the ARCHEOCETI, which kept a movable neck.

 The horizontal disposition of the tail-flukes in the ancestors of the CETACEA did facilitate the rising from or to the water surface, whereas the fore limbs were used for maintaining the body’s balance and for steering. They contain the typical mammalian bones.

 A fleshy dorsal fin for a better stabilization in water then appeared in the whales, as they became the hydrodynamic fish form. Sometimes, the dorsal fin is wanting, as the rostrum is well-careened.

 

Phylogeny

 From the standpoint of the Theory of Initial Bipedalism, as emphasized by several authors ( Max WESTENHOFER, Serge FRECHKOP, Bernard HEUVELMANS ), the original mammals were bipeds and they were closely connected with a prior aquatic phase.

 In my Marine Homonculus Hypothesis, I suggested the vertebrate brain resulted of an ancient apical organ that was conceived originally as a spherical float in a marine creature.

 The characteristics of a big brain in a globular skull, and of the bipedal gait, were obtained before the adaptation of the first mammals to a terrestrial way of life.

 As a matter of fact, the skull of the CETACEA is being deeply transformed, consistently with the external "fish" form. Therefore, the large and efficient encephalon has remained quite undamaged, not far different from a human brain !

 So I emphasize that the CETACEA directly evolved from the Marine Homonculus stage. In other words, the whales and dolphins have always lived in the oceans !

 Indeed, with the exception of the zoophagic feeding, the CETACEA show no characteristics that would bring them in connection with the quadrupedal CARNIVORA or with the undifferenced ancestors of the today ONGULATA.

 In that sense, the relation with the newly discovered fossil Ambulocetus, enhanced as "missing link" by the scientific press, appears as one of the usual and common blowers in the course of the development of natural science...

 

REFERENCES

FRECHKOP, Serge
 1944 Essai d’interpretation biologique de la structure des Cétacés. Bulletin du Musée Royal des Sciences Naturelles de Belgique, 20 [ n° 13 ] : 1-28.

SARRE, François de
 1993 In search for taxonomy and relationships in the vertebrates. Bipedia, n° 10 : 3-13 ( Juin ).

SLIJPER, E.J. et D. HEINEMANN
 1971 Les Cétacés. In : B. Grzimek et M. Fontaine : Le Monde Animal, Zurich, Stauffacher, tome IX.

THEWISSEN, J.G.M. et al.
 1994 In : Science, January 14.

WESTENHOFER, Max
 1948 Die Grundlagen meiner Theorie zum Eigenweg des Menschen. Heidelberg, Carl Winter Universitätsverlag.

 

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