Nous sommes le Ven Octobre 23, 2020 11:36


Heures au format UTC + 1 heure




Poster un nouveau sujet Répondre au sujet  [ 426 messages ]  Aller à la page Précédent  1, 2, 3, 4, 5 ... 15  Suivante
Auteur Message
 Sujet du message:
MessagePosté: Jeu Janvier 29, 2004 16:46 
Hors ligne

Inscription: Mer Décembre 31, 2003 10:27
Messages: 25
L'article cité par Dragon est riche en enseignement. Existe-t-il une organisation qui recense les témoignages et les documents sur ces animaux marins non identifiés ?


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Jeu Janvier 29, 2004 19:47 
Hors ligne
Avatar de l’utilisateur

Inscription: Lun Mars 17, 2003 19:41
Messages: 1152
Localisation: Au fond des mers...
Oui, effectivement. J'ai entendu parler de cette affaire Cousteau. Etrange tout ça.
C'est vrai que la mer nous réserve bien des surprises. Et nous ne sommes prêts à en voir le bout.

_________________
Parmi les nouvelles espèces découvertes, la plupart viennent des océans...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Ven Mars 26, 2004 12:00 
Hors ligne

Inscription: Mer Décembre 31, 2003 10:27
Messages: 25
Au fait cette semaine (semaine 14) M6 passe un telefilm "megalodon" jeudi en 2eme partie de soirée.


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Sam Mars 27, 2004 18:52 
Hors ligne
Avatar de l’utilisateur

Inscription: Lun Mars 17, 2003 19:41
Messages: 1152
Localisation: Au fond des mers...
Une chose est sûre, j'ai hâte de voir le film. Je sens que je vais bien rigoler. :lol:
Autre chose, j'attend le film que les studios Disney sont entrain de produire: Mégalodon, tiré du roman de Steven Alten. Et celui-ci devrait être sérieux comme film.

_________________
Parmi les nouvelles espèces découvertes, la plupart viennent des océans...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Sam Mars 27, 2004 19:16 
Hors ligne
Avatar de l’utilisateur

Inscription: Dim Novembre 16, 2003 17:59
Messages: 213
Localisation: Amity
En complément du message de Leviathan,je precise que le film est pitoyable et tres mal coté.Si vous voulez rire,enregistrez le ou regardez le,mais vous n'y trouverez rien de serieux. 8)


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Lun Mars 29, 2004 15:31 
Hors ligne
Avatar de l’utilisateur

Inscription: Jeu Février 05, 2004 14:13
Messages: 72
Je m'intéresse aux requins :)
L'idée qu'un monstre (de part sa taille :P) puisse encore exister est vraiment... ouaouh lol!
Mais après tout pourquoi pas? Il y a des océans vraiment profonds qui n'ont jamais pus être explorés. C'est un peu comme le calamard géant.

Merci pour ces infos !

_________________
Donnie Darko.
It's a mad world.


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Lun Mars 29, 2004 18:42 
Hors ligne
Avatar de l’utilisateur

Inscription: Lun Mars 17, 2003 19:41
Messages: 1152
Localisation: Au fond des mers...
Je suis bien d'accord avec toi Elvirna. L'idée qu'une telle créature puisse exister, il y a un côté excitant.
C'est vrai qu'il y a des régions sous-marines encore inconnues et inexplorées. Comme je le disais dans un message, l'homme en sait plus sur l'espace que les fonds marins. Qui sait ce qui peut s'y cacher !

Tu parlais du calmar géant ( mon copain ) :wink:. Lui, à l'instar du mégalodon, on sait qu'il existe. Mais également le calmar super géant, qui même si personne ne l'a jamais encore vu, existe bel et bien.

Pour le mégalodon, toutes sortes d'hypothèses qui ont été dites sur le forum tiennent la route. Et je ne serai pas surpris d'apprendre qu'une petite population de mégalodon ait pu survivre.
Car rappelons-le, sa supposée disparition n'est qu'une hypothèse. On en sait rien après tout.
Toutes choses que l'on ne voit pas ne veut pas dire qu'elles n'existent pas.

_________________
Parmi les nouvelles espèces découvertes, la plupart viennent des océans...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Lun Mars 29, 2004 19:06 
Hors ligne
Avatar de l’utilisateur

Inscription: Dim Novembre 16, 2003 17:59
Messages: 213
Localisation: Amity
Il mesure dans les 20 mètres,de quoi créer une panique bien plus grande que Jaws,mais je doute qu'il puisse atteindre d'aussi pres le rivage ou se baignent les suicidaires(baigneurs),puis,vu sa taille,il suffit d'installer une tour anti requin,un garde avec des jumelles,une clochette et a la moindre alerte sonner la cloche. 8)


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Avril 11, 2004 16:26 
Hors ligne
Avatar de l’utilisateur

Inscription: Dim Avril 11, 2004 15:56
Messages: 96
Je viens de lire un livre "serpent de mer et monstres aquatiques" de J. J. Barloy. Trés intéréssant, ce livre ne répond pas beaucoup aux questions que l'on se pose mais il contient beaucoup de témoignages.

Malheureusement trés peu de preuves sur les apparitions de ces otaries à long coup et autres architeutis. Finalement si j'ai bien tout compris, il resterait plusieurs dinosaures encore vivant. Il ne reste qu'a trouver des preuves. Je trouve extrémement dommage que les fonds (financiers) ne soient pas débloqués pour les recherches. Bien sur cela ne raportera rien sur le plan financier mais il faut bien se dire que tout ne peut pas être lucratif et que savoir le fin mot de l'histoire serait un grand bon pour la science.

_________________
Même un trés long voyage doit commencer par un premier pas


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Avril 11, 2004 18:32 
Hors ligne
Avatar de l’utilisateur

Inscription: Lun Mars 17, 2003 19:41
Messages: 1152
Localisation: Au fond des mers...
Dis moi, Bastet, comment t'es-tu procuré ce bouquin de Jean-Jacques Barloy stp ?
J'en cherche, mais je n'en trouve pas, même pas sur le net. Plus d'édition la plupart du temps.

C'est vrai qu'il reste encore beaucoup d'animaux censés avoir disparu à découvrir. Mais pour beaucoup, on ne se repose que sur des témoignages. Malheureusement, beaucoup ne sont pas à prendre au sérieux. Et pour certains, nous avons des preuves irréfutables et visuelles. Cependant l'animal en question nous échappe toujours. Ce qui nous amène à nous poser des questions... décidemment, qu'est-ce qu'on peut s'en poser comme question en ce bas monde quand même. Je devrais créer un observatoir sur toutes les questions que se posent les scientifiques quant à la cryptozoologie marine. :wink:

Quoiqu'il en soit, nous sommes trop préoccupés à financer des voyages dans l'espace que dans les fonds marins. Mais ce que beaucoup de personnes ignorent, et je le regrette, c'est qu'en ignorant les mers, celles-ci vont aller de plus en plus mal. Et que si jamais, dans un futur pas si lointain que ça, les océans s'appauvrissent et disparaissent... nous sommes d'ores et déjà morts !

_________________
Parmi les nouvelles espèces découvertes, la plupart viennent des océans...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Avril 11, 2004 19:21 
Hors ligne
Membre honoraire
Avatar de l’utilisateur

Inscription: Mer Avril 30, 2003 10:30
Messages: 10606
Léviathan a écrit:
Et que si jamais, dans un futur pas si lointain que ça, les océans s'appauvrissent et disparaissent... nous sommes d'ores et déjà morts !


Ce n'est pas encore fait, mais c'est en bonne voie, voir le topic : http://www.paranormal-fr.net/forum/viewtopic.php?t=1627


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Lun Avril 12, 2004 17:41 
Hors ligne
Avatar de l’utilisateur

Inscription: Dim Avril 11, 2004 15:56
Messages: 96
J'ai trouvé le livre dans une bouquinerie de Aix Les Bains.
Quelques renseignements au cas ou ça peut t'aider à le trouver :
Edition Famot 1978.
Je n'ai pas d'autres indications :( désolée.

_________________
Même un trés long voyage doit commencer par un premier pas


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Lun Avril 12, 2004 17:54 
Hors ligne
Avatar de l’utilisateur

Inscription: Lun Mars 17, 2003 19:41
Messages: 1152
Localisation: Au fond des mers...
Merci quand même. Il faut que je m'arme de patience pour en trouver.

Vois-tu Dragon... et pour les autres aussi, en revenant sur les océans, j'ai lu un texte comme quoi notre alimentation de base serait les algues si nous continuons à détruire ce que l'on a sur notre bonne vieille Terre. A condition bien sûr que les océans soient assez productifs pour ça.

_________________
Parmi les nouvelles espèces découvertes, la plupart viennent des océans...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Mar Août 10, 2004 20:55 
Hors ligne
Avatar de l’utilisateur

Inscription: Sam Juillet 03, 2004 12:49
Messages: 136
Localisation: suisse / VD
voilà de quoi motiver certaines personnes (en tout cas moi).
:D :D :D :D :roll:

_________________
l'acte ne sert à rien si la pensée ne suit pas


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Sam Mars 26, 2005 19:15 
Hors ligne

Inscription: Sam Mars 29, 2003 10:35
Messages: 123
J'ai trouvé une critique sur la présumée survivance du megalodon, si quelqu'un pouvait nous en faire une traduction fidèle (pas logicielle, tout le monde peut le faire ça)?

Merci par avance au courageux.

A Critical Evaluation of the Supposed Contemporary Existence of Carcharodon megalodon


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Sam Mars 26, 2005 22:21 
Hors ligne
Avatar de l’utilisateur

Inscription: Sam Mars 26, 2005 18:37
Messages: 68
Localisation: là juste ici
Bonjour

J'aurais une question pourquoi une bête comme le megalodon aurait-elle disparu. (P.S.: si la réponse est quelque part sur le topic excusez-moi, mais je n'ai pas pas tout lu).

Cordialement.

Myrddin :)

_________________
Je penses donc je suis tu penses donc tu suis


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Mars 27, 2005 08:26 
Hors ligne
Avatar de l’utilisateur

Inscription: Mer Mars 31, 2004 10:26
Messages: 927
Localisation: Yvelines (Pres de Paris, en France)
Probablement parce que son environnement a changé trop brutalement pour pouvoir s'y adapter...

_________________
Celle qui porte la vie, porte l'avenir...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Mars 27, 2005 12:20 
Hors ligne
Avatar de l’utilisateur

Inscription: Sam Décembre 25, 2004 01:35
Messages: 2708
Localisation: En Croisade contre l'idiotie
"Rien ne se perd, rien ne se crée, tout se transforme"

Le mégalodon n'a peut être pas disparu, peut-être même que vous en voyez dans certains reportages tv en Australie...

_________________
Heureux les imbéciles...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Mars 27, 2005 12:47 
Hors ligne

Inscription: Lun Mars 21, 2005 20:29
Messages: 3
Erreur, il a eté prouvé que le Requin Blanc n'est pas le descendant du Megalodon !!!


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Mars 27, 2005 14:21 
Hors ligne
Avatar de l’utilisateur

Inscription: Sam Décembre 25, 2004 01:35
Messages: 2708
Localisation: En Croisade contre l'idiotie
Tu sais moi les preuves...surtout que le mégalodon est un requin, tout comme notre "white shark", alors avec l'évolution...

Le poulet que tu mangera ce soir, est peut être le descendant du tyrannosaure, va savoir. :wink:

_________________
Heureux les imbéciles...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Mars 27, 2005 14:38 
Zeh je serai ravie de te traduire ta page, si seulement le lien marchait.


Haut
  
 
 Sujet du message:
MessagePosté: Dim Mars 27, 2005 22:48 
Hors ligne

Inscription: Sam Mars 29, 2003 10:35
Messages: 123
Méphistophélès a écrit:
Zeh je serai ravie de te traduire ta page, si seulement le lien marchait.


Voilà l'article:

Citation:
______________________________________________

A Critical Evaluation of the Supposed Contemporary
Existence of Carcharodon megalodon

by Ben S. Roesch
______________________________________________

Roesch, Ben S. 1998. A Critical Evaluation of the Supposed Contemporary Existence
of Carcharodon megalodon. The Cryptozoology Review 3 (2): 14-24.

Copyright 1999 Ben S. Roesch (bspeersr@uoguelph.ca)

Many consider the white shark (Carcharodon carcharias) to be among the most incredible creatures to roam the oceans today. Growing to lengths upwards of 6 m (20 ft) and weights of more than 2 000 kg (4 400 lb), this large lamnid shark is responsible for occasional attacks on humans. It has become the quintessential shark to many, especially after the success of the movie Jaws, which made the white shark’s name and toothy visage infamous.

About 16 million years ago during the Miocene (1), however, an even larger shark, possibly similar to the C. carcharias, appeared in the world’s oceans. Carcharodon (or Carcharocles) megalodon may have attained an astonishing maximum length of 15 m (50 ft), and weighed as much as 50 tonnes (49 tons) (Gottfried et al. 1996). Such estimates are gleaned from teeth and very rare skeletal components of the animal (sharks have a cartilaginous skeleton that does not readily fossilize; most species of fossil sharks are known from their teeth only, which are very durable structures). Traditional research holds that C. megalodon was ancestral to the white shark, but recent research suggests that it was actually a close relative (2). Authors such as Gottfried et al. (1996) envision C. megalodon as a much larger and bulkier version of this white shark. With a mouth large enough to swallow a cow whole and broad, triangular teeth much like those of the white shark (but up to 17 cm [7 inches] high, as opposed to a maximum of 6 cm [2 inches] in white sharks [Fig. 1]), C. megalodon apparently fed on primitive whales and other large marine mammals (Fig. 2) (3). It is possible that C. megalodon hunted in the same stealthy manner that white sharks often employ to prey on pinnipeds---stalking prey from below and then rising up at a high speed to deliver a massive, often fatal first bite (4). About 1.5 million years ago at the end of the Pliocene, C. megalodon disappeared, due to a variety of possible reasons (Applegate and Espinosa-Arrubarrena 1996), some of which will be discussed below.



Fig. 1. Tooth of Carcharodon megalodon, actual size. Illustration by Richard Ellis (1975).



Despite the general consensus among zoologists and paleontologists that C. megalodon is extinct, it has been suggested by several cryptozoologists and other researchers (e.g. Stead 1963; Clark 1968; Clostermann 1969; Perry 1972; Cartmell 1978; Goss 1987; Bright 1989; Corliss 1991; Shuker 1991, 1995, 1997) that this enormous shark may continue to exist in the deep-sea or another remote part of the ocean. These proponents of C. megalodon survival cite a small body of ‘evidence’ to support their claim, including eyewitness accounts, unfossilized and recently fossilized C. megalodon teeth, and the discovery of the megamouth shark (Megachasma pelagios) in 1976. (Other researchers, such as Ellis [1975, 1994], Ellis and McCosker [1991], and, to a lesser extent, Steel [1985], provide a level-headed, yet open-minded, review of the question of C. megalodon survival). It will be argued below, however, that all of this proposed evidence is weak, and that the suggestion of present-day survival of C. megalodon does not conform with accepted paleontological and ecological knowledge.

Fig. 2. In a Miocene sea, Carcharodon megalodon chases down an early pinniped called Allodesmus. From a forthcoming book written and illustrated by Richard Martin. Artwork Copyright Richard Martin, 1998.

Eyewitness Accounts


A few reports of alleged encounters with large, unidentified sharks have been proposed as evidence for C. megalodon survival. One of the most widely cited is an extraordinary tale recounted by Australian naturalist David Stead (1963: 45-46):

In the year 1918 I recorded the sensation that had been caused among the "outside" crayfish men at Port Stephens, when, for several days, they refused to go to sea to their regular fishing grounds in the vicinity of Broughton Island. The men had been at work on the fishing grounds---which lie in deep water---when an immense shark of almost unbelievable proportions put in an appearance, lifting pot after pot containing many crayfishes, and taking, as the men said, "pots, mooring lines and all". These crayfish pots, it should be mentioned, were about 3 feet 6 inches [1.06 m] in diameter and frequently contained from two to three dozen good-sized crayfish each weighing several pounds. The men were all unanimous that this shark was something the like of which they had never dreamed of. In company with the local Fisheries Inspector I questioned many of the men very closely and they all agreed as to the gigantic stature of the beast. But the lengths they gave were, on the whole, absurd. I mention them, however, as a indication of the state of mind which this unusual giant had thrown them into. And bear in mind that these were men who were used to the sea and all sorts of weather, and all sorts of sharks as well. One of the crew said the shark was "three hundred feet [90 m] long at least"! Others said it was as long as the wharf on which we stood---about 115 feet [35 m]! They affirmed that the water "boiled" over a large space when the fish swam past. They were all familiar with whales, which they had often seen passing at sea, but this was a vast shark. They had seen its terrible head which was "at least as long as the roof on the wharf shed at Nelson's Bay." Impossible, of course! But these were prosaic and rather stolid men, not given to 'fish stories' nor even to talking about their catches. Further, they knew that the person they were talking to (myself) had heard all the fish stories years before! One of the things that impressed me was that they all agreed as to the ghostly whitish color of the vast fish. The local Fisheries Inspector of the time, Mr Paton, agreed with me that it must have been something really gigantic to put these experienced men into such a state of fear and panic.


This report initially sounds promising, especially considering Stead’s proclamation of the witnesses’ integrity. But how can we actually believe a report that speaks of a 150-300 ft (35-90 m) creature---longer than any other animal ever recorded? Shuker (1991, 1995, 1997) contends that, if the account is true---as he seems to believe---fear and surprise could have resulted in these unbelievable figures. Shuker expresses confidence that the actual size of the creature responsible must still have been gigantic to instil such a shock in the fishermen. Stead and Shuker propose that a living C. megalodon would be a near-perfect match.

I remain unconvinced. Admittedly, I cannot disprove this story because of its anecdotal nature, but that trait alone would be grounds enough for most scientists to dismiss it as an unverified “fish-story”. Even if one is asked to ignore the inadmissibility of anecdotal evidence, the enormity of the alleged shark sighted is absurd, even if exaggerated by shock. The “ghostly whitish color” of the alleged animal is also bizarre. Very few marine animals maintain such a colouring; certainly not the white shark, which despite its name is only white on its underside, whereas its back is a distinct dark charcoal grey or bronze-grey. This demarcation is termed dorsal-ventral countershading. In many sharks and pelagic fishes, the darker back reduces contrast with the background and renders the animal less conspicuous. This allows a certain degree of stealth when stalking prey or avoiding predators. Traditional thought holds that the lighter underside works in much the same way when the animal is viewed from below, by matching the down-welling light and eliminating some of the silhouette effect. There is actually an insignificant reduction in silhouette under ambient light conditions. C. megalodon is believed to have occupied a neritic lifestyle much like the white shark (see below), and it is likely that it was similarly countershaded. Thus, the ghostly white shark seen in 1918 appears to be at odds with a well-known environmental adaptation.

Also worth noting in reference to the colour of the 1918 alleged shark is that while some researchers have suggested that the resurrected C. megalodon might live in the deep-sea (see below), deep-sea sharks certainly are not white---in fact most are uniformly dark, both on the dorsal and ventral surfaces of their bodies. (I mention this because I can imagine that some supporters of C. megalodon survival might suggest that the whitish colour of the 1918 alleged shark could be an adaptation to the virtually lightless deep-sea. It seems instilled in the minds of many that a dark environment results in white animals. While this is the case in many cave animals and a few deep-sea creatures, lack of pigmentation is certainly not a general feature of deep-sea animals).

Shuker (1995) and Goss (1987) include two more reported sightings of very large sharks that they interpret as possible evidence for C. megalodon survival. One involved Zane Grey, the famous author of western novels and an avid deep-sea angler, and the other his son Loren. (Not having access to the Grey’s original works in which their sightings are recounted, I rely on Goss [1987] for details). The first sighting occurred when Zane Grey was deep-sea fishing off Rangiroa in the South Pacific in 1927 or 1928. Glancing over the boat’s railing, he spotted an enormous “yellow and green” shark with a “square head, immense pectoral fins and a few white spots.” Grey claimed it was “considerably longer than my boat---conservatively between 35 and 40 feet [10.5 and 12 m].” Some New Zealand fishermen aboard who also saw the great shark agreed with Grey’s estimate. Initially, Grey thought the shark was a whale shark (Rhincodon typus) (Fig. 3), which grows to a length of at least 12 m (40 ft), but according to Goss (1987) Grey thought “only the size of this ... shark was the same; otherwise it was in no way similar.” Here I beg to differ with Grey. Not only does the size correspond well, but whale sharks also have very wide, squarish heads, enormous pectoral fins and are covered with white spots (admittedly, Grey mentions only “a few” white spots, but the degree of spotting in whale sharks is highly variable among individuals and by body region [Richard Martin pers. comm.]). Nonetheless, Grey stated: “I figured out that the fish ... was not a harmless whale-shark but one of the man-eating monsters of the South Pacific. Then I was more frightened than I remember for a long time.” Despite his dramatic style, I would identify Grey’s shark as a whale shark long before suggesting that what he saw was a living C. megalodon or, say, an enormous tiger shark (Galeocerdo cuvier). (This latter species may exceed 5 m [16 ft] in length and has a characteristically squarish snout. Grey caught a great number of tiger sharks in his day and was probably thinking of them when he wrote the above quoted phrase.)


Fig. 3. Whale shark (Rhincodon typus). Illustration by Richard Martin (1995).



The second sighting took place in 1933, again off the coast of Rangiroa. Aboard the S.S. Manganui, Grey and his son Loren were returning to San Francisco after a fishing trip to Tahiti. One evening at about 5:00 p.m., Loren was at the rail when he saw a small flock of spiralling sea gulls and, near by, an area of yellow water (5):

At first I thought it was a whale, but when the great brown tail rose in the ship’s wake as the fish moved ponderously away from the liner, I knew immediately that it was a monstrous shark. The huge round head appeared to be at least 10 to 12 feet across if not more ... It was my belief that this huge, yellowish, barnacled creature must have been at least 40 or 50 feet long. He was not a whale shark: the whale shark has a distinctive white purplish green appearance with large brown spots and much narrower head. So what was he---perhaps a true prehistoric monster of the deep?

What we had seen was something [that] no ichthyologist had ever dreamed existed. The largest known specimen of this type of shark, generally known as a sand shark or black-tipped shark, had hardly been known to exceed a length of about 15 feet.


Despite Loren Grey’s assertions that what he saw was not a whale shark (mirroring his father’s reaction to his own sighting), it is most likely that that is exactly what is was. Grey’s description of a whale shark is completely erroneous: whale sharks are a dark grey, greenish grey or reddish colour above, with many white or yellowish spots and transverse stripes, and are yellowish or white on the underside (Castro 1983). As mentioned previously, they also have a very wide, squarish, yet slightly rounded head. All of these traits fit well with Grey’s description.

Both of the sharks seen by the Greys were at the surface, which mirrors whale shark behaviour. In deep waters, many pelagic and neritic sharks, including the white shark, stay deep much of the day, near the thermocline (where the warm surface water layers sit on and mix with the colder deeper layers). In shallower waters, sharks like the white shark stay near the bottom most of the time, usually only visiting the surface during feeding. The planktivorous whale shark, on the other hand, is often seen browsing the surface layers of the water column, where its food often reaches the highest concentrations.

(Shuker [1995] suggested that the creature that the Greys spotted may be the same responsible for a traditional belief among Polynesian (6) fishermen in New South Wales, Australia. They speak of an enormous 100 ft [30 m] long sea monster, not unlike a white shark, which they call the Lord of the Deep. Such a parallel, however, is completely speculative without further evidence showing an identifiable similarity between this mythical animal and the Grey’s sightings.)

The last eyewitness accounts interpreted as being of C. megalodon are put forward by Cartmell (1978). His first piece of evidence is sonar trackings by “one of the new breed of underwater exploratory vehicles” of an unidentifiable object about 100 ft (30 m) long that was travelling faster than any submarine. The absurdity of this account---which supposedly serves as evidence for C. megalodon survival---will not be commented upon. Cartmell also mentions another eyewitness account of a giant shark:

In the 1960’s along the outer edge of Australia’s Great Barrier Reef, an 85 foot [26 m] ship experienced engine trouble which forced it to weigh anchor for repairs. Although the men subsequently refused to openly report what they had seen for fear of public ridicule, the captain and his crew later told friends of sighting an immense shark as it moved slowly past their ship. Whitish in color, they were awed by its size. It was as long if not longer than their boat! Experienced men of the sea, they too were certain the creature was not a whale.


Cartmell provides no references for his claims, so without verifiable sources, the above stories (the latter of which drips with tabloid style and reads much like a rewritten account of the 1918 giant shark) are useless as evidence.

What is one to make of these alleged sightings? A whale shark identity does not fit perfectly with the Grey’s sightings, but does, however, provide the most sensible and believable explanation. As for the 1918 giant shark, I remain unconvinced that the story is true. Cartmell’s stories are, as mentioned above, even more unbelievable. In any case, the usage of these five unconfirmed and dubious anecdotes as evidence for the resurrection of a giant, extinct shark is ridiculous. As is the case with a large percentage of cryptozoological sightings, the above reports simply are not worthwhile evidence: they are lacking in details, corresponding eyewitness accounts, and overall reliability. If, for example, there were 50 similar sightings of an enormous shark in the South Pacific or elsewhere that did not fit a whale shark identity, attention might be warranted. As it stands, however, there are only five sightings (two of which can be reasonably attributed to whale sharks) and they are highly questionable ones at that. Eyewitness accounts provide no good evidence for the proposed modern-day survival of C. megalodon .

Evidence from Teeth


One of the most persistent and erroneous myths in the case of alleged C. megalodon survival is the claim that unfossilized C. megalodon teeth have been dredged from the ocean floor. The claim, cited as evidence by Cartmell (1978), Goss (1987), and Shuker (1991, 1997), ignores the ironclad fact that no unfossilized C. megalodon tooth has ever been found. This point has been expounded repeatedly by Ellis (1975, 1994) and Ellis and McCosker (1991), yet no cryptozoologist who has written about C. megalodon has bothered to acknowledge it. The myth of unfossilized C. megalodon teeth appears to have originated from at least three different publications, as discussed by Ellis (1975, 1994) and Ellis and McCosker (1991). The first is Whitley (1940) who wrote:

Fresh-looking [my italics] teeth [of C. megalodon ] measuring 4 by 3 1/4 inches [10 by 8 cm] have been dredged from the sea floor, which indicates that if not actually still living, this gigantic species must have become extinct within a recent period.


The next source is Smith (1953: 49), who wrote in his discussion of the white shark:

Teeth 5 ins. [13 cm] long have been dredged from the depths, indicating Sharks of 100 ft. [30 m] with jaws
at least 6 ft. [2 m] across. These monsters may still live in deep water but it is better to believe them extinct.


The third source is Stead (1963: 46). In reference to the 1918 Port Stephens giant shark (see above), he writes:

Personally I have little doubt that in this occurrence we had one of those very rare occasions when humans have been vouchsafed a glimpse of one of these enormous sharks of the White Death [white shark] type which we know to exist, or to have existed in the recent past, in the depths of the sea. While they are probably not abundant they may yet be so. Lest the reader may still think me to be credulous I would like to say that I have seen actual teeth of a shark of this type which were no less than five inches (individually) across the base. They had been dredged up from the bottom of the Pacific Ocean. These, I believe [my italics], were not fossil teeth, such as are found in various Tertiary deposits---from which large quantities of great teeth of the White Shark type have been obtained. In my opinion they were so recent as to justify the belief that they had come from Great Sharks of a type which might still exist in the deep seas!


A reading of each of these quotations gives some idea as to how the myth of unfossilized C. megalodon teeth has crept into the literature. It is important to note that none of the authors---except Stead---are outright in their proclamation of the teeth as unfossilized. The teeth that Whitley and Stead examined are undoubtedly fossilized specimens dredged up by oceanographic surveys such as the Challenger expedition (1873-1876). When found, these teeth are encrusted in layers of manganese dioxide, a mineral that precipitates from sea water over thousands of years. As Ellis (1975) points out, these teeth are often discussed and illustrated in the literature after they have been cleaned of this coating. Such preparation often results in teeth that look like they have been plucked directly from the mouth of a live shark, except for the fact that they are not white but rather a brownish or blackish colour. Many of these teeth are very well preserved, and some have even been found that are a whitish colour (Richard Martin, pers. comm.), possibly a result of geographical and/or biogeochemical variability of the concentration of certain precipitating elements. Such features could conceivably trick an untrained observer (neither Whitley nor Stead were paleontologists) into thinking the teeth were unfossilized.

Surely, the teeth noted by Smith are also fossilized specimens dredged up by oceanographic expeditions. However, because he does not specify that they were fossilized, his comments have been taken as suggestive of the discovery of unfossilized, fresh C. megalodon teeth from the abyss. Despite the persisting rumours of such fresh C. megalodon teeth---rumours which appear to have originated from the above three inconclusive sources---the fact remains that all those discovered to date are unequivocally fossilized.

Supporters of C. megalodon survival have also looked to fossilized C. megalodon teeth for evidence that the species is still alive today. The basis for this argument involves two 12.5 cm- (5 inch-) high C. megalodon teeth dredged up from 4 300 m (14 300 ft) in the South Pacific by the Challenger expedition. Both of the teeth were encrusted in manganese dioxide; one had a 1.7 mm (0.067 inch) layer of the mineral and the other a layer of 3.64 mm (0.14 inches). In 1959, Dr. W. Tschernezky of London’s Queen Mary College dated the teeth by comparing the layer of manganese dioxide on them to an accepted rate of deposition of the mineral in the deep-sea, 0.15 - 1.4 mm per 1000 years. Using the lower value of deposition (see below), Tschernezky (1959) found the teeth to be only about 11 000 and 24 000 years old, respectively. Such a period is a mere blink in the scale of geological time, and Tschernezky’s findings made many ponder the idea that C. megalodon did not go extinct near the close of the Pliocene about 1.5 million years ago, but survived until the end of the Ice Age. It is thus unsurprising that the proponents of C. megalodon survival used this evidence as another reason to believe that C. megalodon could still exist.

These proponents, however, are relying on a paper published nearly 40 years ago. Researchers now believe that this and all other claims of post-Pliocene C. megalodon teeth (some of which are more convincing than Tschernezky’s work) are erroneous, representing reworked material from older deposits (Applegate and Espinosa-Arrubarrena 1996; John Bruner pers. comm.; Henry Mollet pers. comm.; David Ward unpubl. data). This means that C. megalodon teeth have been eroded from pre-Pleistocene deposits and redeposited in younger strata, such as those from the Pleistocene. Whereas reworked fossil bones often show wear from the process, shark teeth (and vertebrate teeth in general) are very durable structures that can withstand high pressures, erosive forces and long-distance transport. Their durability makes it difficult to determine if they have been reworked from older deposits. For example, teeth of fossil sharks reworked into present day beach deposits in southern England are microscopically identical in sharpness to teeth of present-day sharks (Darren Naish, pers. comm.).


Besides probably representing reworked material, a fundamental flaw in Tschernezky’s findings lies in his use of manganese dioxide as an indication of geological age. Manganese dioxide deposition is far from constant, varying due to fluctuations in the concentrations of ions of iron (especially Fe2+) and other elements in sea water. The presence of phytoplankton also plays a factor in the rate of manganese dioxide deposition, partly because Fe2+ is a key ingredient in photosynthesis. Therefore, when a plankton bloom occurs---often caused by an increased concentration of Fe2+---more Fe2+ is removed from the sea water (often remaining removed for many years) and less is available to help form manganese nodules (Valiela 1995; Waller 1996; Richard Martin pers. comm.). Furthermore, Tschernezky only used the lower value of the manganese dioxide deposition rates to obtain his oft-cited age estimates. Some readers may have noticed that by using the higher values for manganese deposition, one obtains dates for the teeth at 1214 years old and 2600 years old, respectively. It is a mystery that the proponents of C. megalodon survival have never jumped on this fact to help support their claim. They would be in error to do so, however, as the large discrepancy in dates caused by the rather wide range of possible depositions of manganese is indicative of the unreliability of this method of dating. For example, if one found a hypothetical C. megalodon tooth that had a layer of manganese 50 mm (2 inches) thick, the approximate datings for that tooth would be 333 000 years old for the lower value (which Tschernezky used) and 36 000 years old for the high value. The difference between those two dates is 297 000 years. Utilizing the higher value consistently gives a date representing only 10% of that of the lower value. Such a large range of error is hard to accept and thus dating by rates of manganese deposition is inaccurate and unreliable.

One final piece of tooth “evidence” put forward by some C. megalodon survival supporters regards a story involving the Australian cutter Rachel Cohen (Clostermann 1969; Barloy 1985). While in an Adelaide dry dock in March 1954, workers found 17 teeth embedded in the ship’s wooden hull that reportedly resembled those of the white shark. Unlike the white shark, however, the teeth were said to have been 8 cm (3 inches) wide and 10 cm (4 inches) high; the largest white shark teeth on record measure about 6 cm (2.5 inches) in height. The teeth were arranged in a semi-circle (typical of a shark bite) about 2 m (6 ft) in diameter, and the “bite” was near the propeller. The propeller shaft itself was bent. The Rachel Cohen’s captain recalled a shudder the boat experienced one night during a storm near Timor, Indonesia. At the time, he thought it had been caused by a collision with a floating tree trunk, which are apparently common in the area. While this report makes entertaining reading, it is useless for a critical examination of supposed evidence for the present-day survival of C. megalodon . Even if the story is true, the sizes of the teeth may be exaggerated (Richard Ellis, pers. comm.), and it is even reasonable to suggest that the ‘teeth’ were misidentified (Richard Martin, pers. comm.) (7). The sources of the story are unreliable and give no references, which if provided could be used to verify or disprove the claim.

The Megamouth Analogy

Ever since the megamouth shark (Fig. 4) was accidentally discovered tangled up in a U.S. Navy deep-sea anchor in 1976, cryptozoologists have been keen on using it to point out that the oceans can still harbour large species unknown to man. Some proponents of modern-day C. megalodon survival have also used the megamouth to support their claim (e.g., Shuker 1995). However, the comparison of the megamouth with C. megalodon , or almost any other marine cryptid, is illogical.


Fig. 4. Megamouth (Megachasma pelagios). Illustration by D. Bryan Stone III, from Castro (1983).



As a very general analogy, the megamouth does show that the oceans have a lot of secrets left to reveal, but one has to realize that the megamouth is by nature a very elusive, highly specialized and unique creature. Inhabiting mesopelagic waters (200-1000 m [660-3300 ft] in depth), it is a vertical migrator, following the diel (night/day) movements of its prey, euphausiid shrimps and other small marine animals. A megamouth tracked off California by Nelson et al. (1997) was found to stay deep in the water column during the day, at about 100-200 m (330-660 ft) or more; at night it moved shallower, to within 12-25 m (39-82 ft) of the surface. Because of its deep-water habits it is thus unlikely to be encountered by humans. Much of our knowledge of deep-sea creatures comes from long-lines and trawls set at depth, but these methods would not help in finding a megamouth. Being a planktivore, it would not be interested in a baited hook, and because of its large size it probably would not be swept up in a trawl (admittedly, this latter point applies equally to other hypothetical large marine cryptids). Also, many trawls have doors that close when the net is raised to the surface, and as far as we know, the megamouth does not cruise close to the sea floor. These factors, among others, highlight why the megamouth may have remained undiscovered for so long.

It is also important to note that the megamouth shark is highly adapted to its nutrient-poor deep-sea environment, with a poorly calcified skeleton, flabby muscles and a low activity level (Taylor et al. 1983). These and other specializations represent millions of years of evolution, and cannot be achieved “over-night” by species with different adaptations and ecologies, including C. megalodon (see below).

The megamouth is not a useful analogy to support the existence of marine cryptids, including C. megalodon, unless the marine cryptid is proposed to be a highly-specialized mesopelagic planktivore. In our case, it is safe to say that C. megalodon was certainly not such a creature.

Ecological Counter-Evidence


The ultimate point that debunks the suggestion of modern-day survival of C. megalodon is the current paleoecological view of the shark. Simply put, all available evidence suggests that C. megalodon inhabited tropical waters and, like the extant white shark, was a coastal species (Purdy 1996). It was not a deep-sea inhabitant that fed on giant squids (Architeuthis sp.), as envisioned by many proponents of C. megalodon survival (e.g. Clark 1968; Shuker 1995). A creature as large and adapted to a coastal, warm and food-rich marine habitat as C. megalodon could not survive in the cold, food-poor deep-sea. Millions of years of evolution moulded C. megalodon to be an active, shallow-water predator of primitive whales, not a sluggish, deep-sea, squid-eating leviathan. In fact, C. megalodon may have died out due partially to the Pliocene extinction of a major food source, early baleen whales known as cetotheriids. (Other possible factors in the extinction of C. megalodon include changes in oceanic circulation, the closing of the Isthmus of Panama [which might have cut off access to mating and pupping areas] and even competition from other large predators such as orcas [Orcinus orca] [Richard Martin in prep.].) The whales that survived and evolved into the species we know today may have simply been too fast for C. megalodon to catch (Richard Martin in prep.). These new whales also showed a trend towards colder waters, to which C. megalodon was not suited. These factors resulted in a lessened food supply, and in a sense, C. megalodon may have starved to death.

Some proponents of C. megalodon survival might still say that C. megalodon could have adapted to a deep-sea environment after its accepted extinction date of about 1.5 millions years ago. This argument lacks all reason. Deep-sea fishes and other animals are extremely well adapted to the harsh conditions of their environment, with reduced skeletons and tissues, pressure- and temperature-insensitive enzymes, low activity and metabolic rates, and specialized foraging methods, among other adaptations (Ellis 1996; Helfman et al. 1997). Likewise, C. megalodon was probably well adapted to its very different shallow-water environment. The idea that C. megalodon could simply change all of its anatomical, physiological and behavioural specializations to adapt itself to a totally different environment, such as the deep-sea, is fatuous.

If C. megalodon were still alive today, than it would have to exist in the shallow, food-rich continental shelf waters to which it was so well adapted. I doubt that any serious proponent of C. megalodon survival would suggest that the great shark could remain undetected in this region. Like the extant white shark, C. megalodon surely fed near the sea surface at times, and if it were still alive today we would have ample evidence of its existence. Certainly, popular activities such as surfing, swimming and boating would become that much more hazardous with a 15 m, super-predatory shark swimming around.

Conclusion

The suggestion by some researchers and cryptozoologists that C. megalodon has survived to the present-day lacks any acceptable supporting evidence. Furthermore, the idea conflicts with current paleontological and ecological knowledge. The case of C. megalodon survival can thus be safely classified as a popular myth without any basis in fact. Pending further, substantial and tenable evidence, the question of C. megalodon’s continued existence should provisionally be considered answered: the shark is dead. In the opinion of this researcher, the question of C. megalodon survival warrants no further serious attention.

Acknowledgements

I would like to express my deepest thanks to Richard Martin, John Moore, and Darren Naish for providing references, encouragement, comments, and criticism. Thanks also to John Bruner, Richard Ellis, Ian Fergusson, Henry Mollet, and David Ward for various comments.

Endnotes

(1) Some evidence exists that suggests that C. megalodon appeared as early as the Eocene, about 50 million years ago, but these finds are largely discounted by most researchers as results of misidentification or poor documentation (Ellis and McCosker 1991; Applegate and Espinosa-Arrubarrena 1996; Purdy 1996).

(2) There is a fair amount of controversy over the phylogeny of C. megalodon . Some researchers think it is related to the white shark and therefore deserves to be placed in the genus Carcharodon. Others subscribe to the theory that C. megalodon is only a distant relative of the white shark, and that it should be given its own genus, Carcharocles, and placed in a separate lineage that gave way to the modern day odontaspidid sand tiger sharks (Cappetta 1987). (If the latter theory is true, than C. megalodon may not have looked much like the white shark, but possibly more like an oversized sand tiger shark with much larger and broader teeth [Richard Martin in prep.].) For the sake of stability, the more popularly used genus, Carcharodon, is used in this discussion. It should be noted, however, that in the paleontological literature, Carcharocles is presently the favoured genus for C. megalodon (Richard Martin pers. comm.). For more details on the Carcharodon vs. Carcharocles debate, see various papers in Klimley and Ainley (1996) and paleoichthyologist Jim Bourdon’s web site at http://www.elasmo.com/

(3)A significant part of the white shark’s diet at all growth phases consists of fishes, and C. megalodon was certainly piscivorous as well. Because of its large size, however, C. megalodon was probably more reliant on marine mammals as a food item than is the white shark. Like extant tiger sharks, C. megalodon may have also scavenged to a greater extent than does the white shark, augmenting its diet in its nutrient-poor tropical environment (Richard Martin pers. comm.).

(4) This is a rather simplistic view of white shark predatory behaviour, and recent research hints at more complicated and dynamic interactions between it and its prey.

(5) The yellow water mentioned by Loren Grey could have been the result of a plankton bloom or coral spawn---an occurrence that often attract whale sharks (Richard Martin pers. comm.).

(6) It is probable that Shuker meant Melanesian.

(7) A one-time loss of 17 teeth from a white shark or other shark represents a considerable reduction of dentition. Sharks continuously shed and lose teeth throughout their life, but they almost never lose more than a few teeth at a time. Typically, lost teeth are from the functional (outermost and oldest) series, with the lower teeth shed or lost more frequently than the upper teeth. If a shark really did chomp down on the Rachel Cohen’s hull, it would have been essentially toothless for sometime: a white shark that lost 17 teeth would be missing some 65% of its upper functional series and about 70% of its lower functional series. It is unlikely that a white shark or other shark would lose that many teeth with one bite (Richard Martin pers. comm.).

References


Applegate, S. P., & L. Espinosa-Arrubarrena. 1996. The fossil history of Carcharodon and its possible ancestor, Cretolamna: a study in tooth identification. In A. P. Klimley and D.G. Ainley (eds.), Great White Sharks: The Biology of Carcharodon carcharias (San Diego: Academic Press), pp. 19-36.

Barloy, J-J. 1985. Les Survivants de L’Ombre: Enquête sur les Animaux Mysterieux. (Paris: Editions Arthaud).

Bright, M. 1989. There are Giants in the Sea. (London: Robson Books).

Cappetta, H. 1987. Handbook of Paleoichthyology. Chondrichthys II: Mesozoic and Cenozoic Elasmobranchii. Handbook of Paleoichthyology 3B: 1-193.

Cartmell, B.C. 1978. Let’s Go Fossil Shark Tooth Hunting. (Venice, Florida: Natural Science Research).

Castro, J. I. 1983. The Sharks of North American Waters. (College Station, Texas: Texas A&M University Press).

Clark, J. F. 1968. Serpents, Sea Creatures and Giant Sharks. Unpublished manuscript.
Clostermann, P. 1969. Des Poissons si Grands. (Paris: Flammarion).

Corliss, W. 1991. Searching for Monster Sharks. Science Frontiers 74 (reproduced athttp://www.knowledge.co.uk/frontiers /sf074/sf074b08.html).

Ellis, R. 1975. The Book of Sharks. (New York: Grosset & Dunlap).

---------------------. 1994. Monsters of the Sea. (New York: Alfred A. Knopf).

---------------------. 1996. Deep Atlantic: Life, Death, and Exploration in the Abyss. (New York: Alfred A. Knopf).

---------------------, & J. McCosker. 1991. Great White Shark. (New York: HarperCollins and Stanford, California: Standford University Press).

Goss, M. 1987. Do Giant Prehistoric Sharks Survive? Fate 40 (11): 32-41.

Gottfried, M.D., L.J.V. Compagno, & S.C. Bowman. 1996. Size and skeletal anatomy of the giant “Megatooth” shark Carcharodon megalodon. In A. P. Klimley and D.G. Ainley (eds.), Great White Sharks: The Biology of Carcharodon carcharias (San Diego: Academic Press), pp. 55-66.

Helfman, G.S., B.B. Collette & D.E. Facey. 1997. The Diversity of Fishes. (Toronto: Blackwell Science).

Klimley, A.P. & D.G. Ainley (eds.). 1996. Great White Sharks: The Biology of Carcharodon carcharias. (San Diego: Academic Press).

Nelson, D.R., J.N. McKibben, W.R. Strong, C.G. Lowe, J.A. Sisneros, D.M. Schroeder & R.J. Lavenberg. 1997. An acoustic tracking of a megamouth shark, Megachasma pelagios: a crepuscular vertical migrator. Environmental Biology of Fishes 49: 389-399.

Perry, R. 1972. The Unknown Ocean. (Newton Abbot: David & Charles).

Purdy, R.W. 1996. Paleoecology of Fossil White Sharks. In A. P. Klimley and D.G. Ainley (eds.), Great White Sharks: The Biology of Carcharodon carcharias (San Diego: Academic Press), pp. 67-78.

Shuker, K.P.N. 1991. The search for monster sharks. Fate 44 (3): 41-49.

---------------------. 1995. In Search of Prehistoric Survivors. (London: Blandford).

---------------------. 1997. From Flying Toads to Snakes with Wings. (St. Paul, Minnesota: Llewellyn Publications).

Smith, J.L.B. 1953. The Sea Fishes of Southern Africa. (Johannesburg: Central News Agency).

Stead, D.G. 1963. Sharks and Rays of Australian Seas. (London: Angus & Robertson).

Steel, R. 1985. Sharks of the World. (New York: Facts on File Publications).

Taylor, L.R., L.J.V. Compagno & P.J. Struhsaker. 1983. Megamouth---a new species, genus, and family of lamnoid shark (Megachasma pelagios, family Megachasmidae) from the Hawaiian Islands. Proceedings of the California Academy of Sciences 43: 87-110.

Tschernezky, W. 1959. Age of Carcharodon megalodon? Nature 184: 1331-1332.

Valiela, I. 1995. Marine Ecological Processes, 2nd ed. (Berlin: Springer Verlag)

Waller, G. (ed.). 1996. SeaLife: A Complete Guide to the Marine Environment. (Washington, D.C.: Smithsonian Institution Press).

Whitley, G. P. 1940. Fishes of Australia. Part I: The Sharks. (Sydney: Royal Zoological Society of New South Wales).


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Mars 27, 2005 23:57 
Hors ligne
Avatar de l’utilisateur

Inscription: Sam Décembre 25, 2004 01:35
Messages: 2708
Localisation: En Croisade contre l'idiotie
Pas le courage de lire, désolé, encore moins de le traduire :lol:

_________________
Heureux les imbéciles...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Lun Mars 28, 2005 13:22 
Allez amuse toi bien Lilie! Je vais m'y mettre mais tu l'auras pas de suite la patience est le meilleur des maux... :roll:


Haut
  
 
 Sujet du message:
MessagePosté: Sam Avril 02, 2005 18:56 
Je suis vraiment désolée mais je dois m'avouer vaincue, il ya trop de mots que je ne connais pas et c'est trop long. Vraiment désolée! :oops:


Haut
  
 
 Sujet du message:
MessagePosté: Dim Avril 03, 2005 00:36 
Hors ligne
Avatar de l’utilisateur

Inscription: Sam Décembre 25, 2004 01:35
Messages: 2708
Localisation: En Croisade contre l'idiotie
J'en étais sûr :lol:

_________________
Heureux les imbéciles...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Avril 03, 2005 04:34 
Traduction de la 1ère partie: Du tout début à la partie nommée "Eyewitness Accounts".

Citation:
______________________________________________

Une évaluation critique de l’existence contemporain supposée
du megalodon de Carcharodon

par Ben S. Roesch
______________________________________________

Roesch, Ben S. 1998. Une évaluation critique de l'existence contemporaine supposée
du megalodon de Carcharodon. La Revue De Cryptozoology 3 (2) : 14-24.

Copyright Ben 1999 S. Roesch (bspeersr@uoguelph.ca)

Beaucoup considèrent le requin blanc (carcharias de Carcharodon) parmi les créatures les plus incroyables errant les océans de nos jours. Atteignant des longueurs de 6 m (20 pi) et pesant plus de 2 000 kilogrammes (4 400 livres), ce grand requin de lamnid est responsable des attaques occasionnelles sur les humains. C'est devenu le requin quintessenciel à beaucoup, particulièrement après le succès du film Jaws, qui ont rendu le nom et la bouche remplie de dents du requin blanc infâmes.

Il y a environ 16 millions d'années pendant le (1) miocène, un requin encore plus grand, probablement semblable aux carcharias de C., apparut dans les océans du monde. Le megalodon de Carcharodon (ou Carcharocles) a pu avoir atteint une longueur maximum étonnante de 15 m (50 pi), et avoir pesé pas moins de 50 tonnes (49 tons) (Gottfried et al. 1996). De telles évaluations sont glanées des dents et des composants squelettiques très rares de l'animal (les requins ont un squelette cartilagineux qui ne fossilise pas aisément ; la plupart des espèces des requins fossiles sont connues de leurs dents seulement, qui sont des structures très durables). La recherche traditionnelle soutient que le megalodon de C. était héréditaire au requin blanc, mais la recherche récente suggère que c'ait été réellement un parent étroit (2). Les auteurs tels que Gottfried et al. (1996) envisagent le megalodon de C. comme version beaucoup plus grande et plus encombrante de ce requin blanc. Avec une bouche assez grande pour avaler une vache en long et en large, les dents triangulaires tout comme ceux du requin blanc (mais jusqu'à 17 centimètres [ 7 pouces ] d'hauteur, par opposition à un maximum de 6 centimètres [ 2 pouces ] pour les requins blancs [ fig. 1 ]), les megalodon de C. se sont apparemment nourri des baleines primitives et d'autres grands mammifères marins (fig. 2) (3). Il est possible que le megalodon de C. ait chassé de la même façon furtive que les requins blancs utilisent souvent pour attaquer leur proie, les pinnipèdes, c’est-à-dire traquer des proies par dessous et puis ensuite remonter à grande vitesse afin de leur asséner une massive et parfois fatale première morsure (4). Il y a environ 1.5 million d'années à la fin du pliocène, le megalodon de C. a disparu en raison d'une variété de raisons possibles (Applegate et Espinosa-Arrubarrena 1996), dont certaines seront discutées ci-dessous.



En dépit du consensus général parmi les zoologistes et les paléontologistes qui dit que le megalodon de C. est maintenant éteint, il été suggérée par plusieurs cryptozoologistes et d'autres chercheurs (par exemple Stead 1963 ; Clark 1968 ; Clostermann 1969 ; Perry 1972 ; Cartmell 1978 ; Goss 1987 ; 1989 lumineux ; Corliss 1991 ; Shuker 1991, 1995, 1997) que cet énorme requin continue peut-être d’exister en eaux profondes ou dans une autre partie éloignée de l'océan. Ces partisans de la survie du megalodon de C. citent une infime preuve pour soutenir leurs dires, y compris des comptes de témoin oculaire, des dents du Megalodon défossilisés et récemment fossilisés, et la découverte du requin Megamouth (Megachasma pelagios) en 1976. (D'autres chercheurs, tels qu'Ellis [ 1975, 1994 ], Ellis et McCosker [ 1991 ], et, à un moindre degré, Steel [ 1985 ], fournissent un avis pondéré, quoique ouvert d’esprit, faisant le point sur la question de la survie du megalodon de C.). On en discutera ci-dessous, pourtant, que toute cette évidence proposée est faible, et que la suggestion de la survie actuelle du megalodon de C. ne se conforme pas à la connaissance paléontologique et écologique admise.


Notes de bas de page

(1) Des évidences existantes suggèrent que le megalodon de C. soit apparu dès l'Eocène, il y a environ 50 millions d'années, mais ces trouvailles sont en grande partie escomptées par la plupart des chercheurs comme résultat d'identification erronée ou de documentation faible (Ellis et McCosker 1991 ; Applegate et Espinosa-Arrubarrena 1996 ; Purdy 1996).

(2) Il y a une quantité considérable de polémique à propos de la phylogénie du megalodon de C.. Quelques chercheurs pensent qu'on le lie au requin blanc et qu’il mérite donc d'être placé dans le genre des Carcharodon. D'autres souscrivent à la théorie que le megalodon de C. est seulement un parent éloigné du requin blanc, et qu'on devrait lui donner son propre genre, Carcharocles, et le placer dans une lignée séparée qui a mené aux requins tigre de sable d'odontaspidid modernes (Cappetta 1987). (Si la dernière théorie est vraie, le megalodon de C. ne peut pas avoir ressembler au requin blanc, mais probablement plus à un requin surdimensionné du tigre de sable avec des dents beaucoup plus grandes et plus larges [ Richard Martin in prep. ].) Pour la stabilité, le genre le plus populairement utilisé, Carcharodon, est employé dans cette discussion. Il est à noter, cependant, que dans la littérature paléontologique, Carcharocles est actuellement le genre favorisé pour le megalodon de C. (Richard Martin pers. comm.). Pour plus de détails sur le Carcharodon versus le Carcharocles, voir les divers papiers sur le site Web de Klimley et d'Ainley (1996) et du paléoichthyologiste Jim Bourdon [ Lien ]

(3)Une significative part du régime du requin blanc à toutes les phases de croissance se compose des poissons, et le megalodon de C. était certainement aussi piscivore. En raison de sa grande taille, cependant, le megalodon de C. était probablement plus dépendant des mammifères marins comme nourriture qu’en est le requin blanc. Comme les requins tigre existant encore, le megalodon de C. a également fouillé à un plus grand degré que le requin blanc pour se nourrir, afin d’améliorer son régime dans son environnement tropical pauvre en alimentation (Richard Martin pers. comm.).

(4) C'est une vue plutôt simpliste du comportement prédateur du requin blanc, et les récentes recherche laissent entendre des interactions plus compliquées et plus dynamiques entre lui et sa proie.


C'est de la traduction assez vite faite, alors ce n'est pas parfait.
J'arriverai dès que possible avec la partie suivante, qu'on appelle Comptes de Témoins Occulaires. Mais cela demande beaucoup de temps.

@ + ;)
-Ghost-


Haut
  
 
 Sujet du message:
MessagePosté: Dim Avril 03, 2005 08:46 
Chevalier Baran a écrit:
J'en étais sûr :lol:

Je suis véxée! :oops: Mais j'ai vraiment pas le temps!
Par contre Ghost si tu veux la première partie des témoins oculaires je l'ai... :cry:


Haut
  
 
 Sujet du message:
MessagePosté: Dim Avril 03, 2005 19:37 
Hors ligne
Avatar de l’utilisateur

Inscription: Sam Décembre 25, 2004 01:35
Messages: 2708
Localisation: En Croisade contre l'idiotie
Perso, même traduite, je ne sais même pas si je la lirai.

Ca ne vaut que pour moi mais est ce que ca en vaille le coup?

_________________
Heureux les imbéciles...


Haut
 Profil  
 
 Sujet du message:
MessagePosté: Dim Avril 03, 2005 20:25 
On va quand même pas faire un sondage pour savoir qui va lire ou pas? J'avoue que c'est long maintenant on oblige personne a lire je crois. :wink:


Haut
  
 
Afficher les messages précédents:  Trier par  
Poster un nouveau sujet Répondre au sujet  [ 426 messages ]  Aller à la page Précédent  1, 2, 3, 4, 5 ... 15  Suivante

Heures au format UTC + 1 heure


Qui est en ligne

Utilisateurs parcourant ce forum: Aucun utilisateur enregistré et 2 invités


Vous ne pouvez pas poster de nouveaux sujets
Vous ne pouvez pas répondre aux sujets
Vous ne pouvez pas éditer vos messages
Vous ne pouvez pas supprimer vos messages
Vous ne pouvez pas joindre des fichiers

Rechercher:
Aller à:  

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Traduction par: phpBB.biz
phpBB SEO