Kikis

The Dolphin was not a fish

19 posts in this topic

rolleyes.gif I ever floor the statement about Dolphin and whale was not a fish but its classified in sea mamals. Many audiences was not believed, they need a proved . I tried my best to prove it but i had shortage with concept and theory and also evolution picture. I need help for some material, and picture that could explain much about dolphin evolution from its ancestor till recent species.
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There are lots of other aspects of their physiology that are easier to exaplin why they are mammals. One obvious one is that they don't posses gills. Both dolphins and whales need to come to the surface to breath using lungs and then they hold their breath while swimming. Granted bluw whales can hold their breath for a VERY long gitme with a single gulp of air. Another exampel would be that they give birth to their young in a very similiar way to land mammals. Fish tend to lay eggs that eventually hatch to release the young...although not all fish do this.

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You can make a very simple experiment:

Take a whale into your left hand and with your right hand keep its head under water for two and a half hour. If the whale is dead, it is not a fish.

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Dolphins evolved from a wolf-like animal and you can see the evidence of this because dolphins and whales have vestigial hip bones which through evolution have shrunk over time. There's also the fact that both dolphins and wolves move their spine up and down, rather than like fish and sharks which move their spin or spin-like structure left and right.

Edited by steevey
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There are lots of other aspects of their physiology that are easier to exaplin why they are mammals. One obvious one is that they don't posses gills. Both dolphins and whales need to come to the surface to breath using lungs and then they hold their breath while swimming. Granted bluw whales can hold their breath for a VERY long gitme with a single gulp of air. Another exampel would be that they give birth to their young in a very similiar way to land mammals. Fish tend to lay eggs that eventually hatch to release the young...although not all fish do this.

They also nurse their young. Whale milk is supposedly similar in texture to cottage cheese.

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Dolphins evolved from a wolf-like animal and you can see the evidence of this because dolphins and whales have vestigial hip bones which through evolution have shrunk over time. There's also the fact that both dolphins and wolves move their spine up and down, rather than like fish and sharks which move their spin or spin-like structure left and right.

 

Do you have any papers to refer to, for further information please? That is quite a large claim to make.

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Do you have any papers to refer to, for further information please? That is quite a large claim to make.

 

steevey might be referring to Mesonychidae, an extinct family of land mammals which was once thought to be the ancestor of many modern mammal lineages including cetaceans (whales and dolphins), and which existed from around 65 to 35 million years ago. Those things really looked like wolves. The studies were all based on dentition (tooth anatomy), but this has recently been discredited somewhat. Now it is thought that cetaceans branched off from other mammals in the artiodactyl lineage (along with the hippo).

 

However, there were actually some wolf-like cetaceans before the non-aquatic ones all died out, for example Pakicetus (see pic below) and Ichtyolestes. There was a 2001 paper in Nature about it: Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls (Thewissen et al.). It's important to note that the 'wolf like' ancestor of dolphins and whales was not actually a wolf, so directly drawing a comparison between whales and modern wolves is a bit confusing. The spine idea is a good one though: fish flex the spine laterally (side to side) whilst most mammals flex it dorso-ventrally (up and down).

 

See the Wikipedia page on evolution of cetaceans for more info.

 

Pakicetus.jpg

 

Pakicetus attocki skeleton (early land cetacean).

Edited by Blahah
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  • They have no gills (must come up to the surface for air.
  • They internally fertilise during sex.
  • They give birth to live young.
  • They have vestigial legs.

No fish have these qualities. Both Dolphins and Whales have all of these qualities.

 

 

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Endothermic

Have mammary glands

Have hair

Edited by SMF
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  • They have no gills (must come up to the surface for air.
  • They internally fertilise during sex.
  • They give birth to live young.
  • They have vestigial legs.

No fish have these qualities. Both Dolphins and Whales have all of these qualities.

 

 

 

Yep, and as mentioned already they suckle their young with milk, and have hair (around the blowholes, at least in whales).

 

Jerry Coyne's excellent Why Evolution is True has a good section on the evolution of whales.

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You can make a very simple experiment:

Take a whale into your left hand and with your right hand keep its head under water for two and a half hour. If the whale is dead, it is not a fish.

 

To throw a spanner into the works here, don't certain species of lung fish also drown if not allowed to surface for air? (I am also wondering about species of snakehead?)

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Indeed. I think that most lungfishes actually have atrophied gills and would eventually drown (at least from what little I remember). Which demonstrates that single traits are often insufficient to make precise phylogenetic distinctions, especially over large distances.

Edited by CharonY
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There are also fish that feed their young a milk like substance as well, I'm not sure there is one thing you can point to and say this makes a dolphin a mammal and not a fish because no fish does this but no fish has all the mammalian characteristics a dolphin does nor does a dolphin have all the characteristics a fish does. On a necropsy table the mammal-ness becomes obvious as does the fishiness of a fish, also it should be trivial to show that dolphins are mammals genetically by comparing their genomes. Just like it is possible to show that Humans are genetically mammals and not reptiles it should be possible to show that dolphins are genetically mammals and not fish.

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Phenotypic evidence, such as endothermy, lungs rather than gills, vestigial legs, hair, lack of scales, placental young etc and so on strongly suggest that cetaceans (whales & dolphins) are mammals and genetic evidence evidence is in support :

 

- Maureen A. O'Leary and Jonathan H. Geisler (1999) The Position of Cetacea within Mammalia: Phylogenetic Analysis of Morphological Data from Extinct and Extant Taxa Systematic Biology Vol. 48, No. 3 (Sep., 1999), pp. 455-490

- Springer MS, Stanhope MJ, Madsen O, de Jong WW (2004) Molecules consolidate the placental mammal tree. Trends Ecol Evolut 19:430–438

 

The process by which they came to physically resemble fish is called convergent evolution, whereby similar environmental conditions select for similar traits in organisms with different ancestors, which leads to distantly related organisms having similar appearances.

Edited by Arete
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there are no such things as a vestigal organs

!

Moderator Note

This is a mainstream science forum, where mainstream science is discussed. Empty claims are not allowed, let alone one that tries to hijack a thread to promote your own pet theory or unscientific notion of reality. Don't do it again.

 

 

"No vestigial organs" topic split into its own topic here.

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Dolphins have the fish, reptilian and higher mammalian (like us) parts in their brains.

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yup,, that was so nice,, all I know b4 that i dolphins is mammal

 

yup,, that was so nice,, all I know b4 that i dolphins is mammal

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