Sea animals larger than land animals.Why its not the case with Dinosaurs?

[Sergey Woropaew]

Sea animals today larger than land animals.(whale vs elephant) Why?- Because the effects of gravity are lower in water. their skeletons don't have to  support as much weight as they would out of water. Thats why biggest animal is whale. So - why it's not work with dinosaurs? Biggest dinosaurs - is land creatures -  Argentinosaurus-30-40 meters long (and other titanosaurs),while in the sea we find smaller animals (biggest is Liopleurodon i guess  -6 meters as known today)?.

So why is that? is laws of physics was completely upside down in dinosaur times?

 

Edited January 29, 2017 by Sergey Woropaew

[ashcraft]

I suspect it is a case of niche exclusion.  There were already large lunged vertebrates filling the ocean, keeping dinosaurs out.

 

Could also be that there is more available biomass for growth now, since the biggest whales are filter feeders.

 

Brent Ashcraft

[Ramon]

1 hour ago, Sergey Woropaew said:

Sea animals today larger than land animals.(whale vs elephant) Why?- Because the effects of gravity are lower in water. their skeletons don't have to  support as much weight as they would out of water. Thats why biggest animal is whale. So - why it's not work with dinosaurs? Biggest dinosaurs - is land creatures -  Argentinosaurus-30-40 meters long (and other titanosaurs),while in the sea we find smaller animals (biggest is Liopleurodon i guess  -6 meters as known today)?.

So why is that? is laws of physics was completely upside down in dinosaur times?

 

 

The ocean has no effect on animals. There is no big animals on land because of the megafauna extinction 10,000 and of course dinosaurshe are already extinct. Some animals on the sea like the giant squid grow that big because animals living at deep depths of the ocean tend to be bigger. This is called gigantism and happens when there's really cold temperatures, this was also the case for trilobites some where big because of cold temperature of the depths. Whales are big because they evolved that way. 

 

And gravity is the same on water and land, it's just that animals adapt to float and swim.

 

                      Hope this answers your question!!!  

[Sergey Woropaew]

6 hours ago, Ramon said:

"This is called gigantism and happens when there's really cold temperatures, this was also the case for trilobites some where big because of cold temperature of the depths. Whales are big because they evolved that way."

Thanks for serious answer, couldn't find answer for this question on other forums.:)

So- even if land animals was  gigantic in dinosaur era- there is not the same with sea animals? because there was no cold temperature of the depths in dinosaur era?

[Ash]

There was still cold water. I think the above answers, whilst being good, didnt quite get the question.

 

Today the largest animals on the planet are found in the ocean. In dinosaur days the largest were found on land. I think he's asking why is that the case. Why were there no 30m long creatures swimming in the dinosaur days compared to now?

[LordTrilobite]

Animals can get bigger in water due to their body being supported by the water. Weight is just less of an issue for animals living in water.

 

Dinosaurs, while being land animals got really big for several reasons. For example, like birds, dinosaurs have much more efficient breathing. Airsacks in their bones not only save weight but also aid in breathing. This among other things makes the basic bodyplan of a dinosaur better for being really big. Us mammals literally have heavy bones and thus don't get as big on land.

[Fossildude19]

11 hours ago, Sergey Woropaew said:

...   "Biggest dinosaurs - is land creatures -  Argentinosaurus-30-40 meters long (and other titanosaurs),while in the sea we find smaller animals (biggest is Liopleurodon i guess  -6 meters as known today)?." ...

 

 

A quick correction:

Shastasaurus  sikkanniensis  (a species of ichthyosaur) has been estimated to have been 21 meters long (69 feet), which would make it the largest aquatic reptile found so far.

Liopleurodon ferox has only been estimated to have been 6.39 meters long. (21 feet)  Predator X was a much larger pliosaur, estimated to have been around 15 meters in length. (49 feet) 

Regards,

 

Info from LINK

[ashcraft]

What is being spoken of relating body size to temperature is known as Bergman's rule which states that within a species, the farther you get from the equator, the larger their body sizes tend to become.  Compare Keys white tailed deer versus Northern white tailed deer.

 

In order to become large, three factors have to be met.  The species must have the genetics to become larger, they must physically be able to get larger, and there must be a driving force (evolution) to select for larger size.

 

Keep in mind,  titanotheres were larger then most dinosaurs.

 

Brent Ashcraft

[Ramon]

Opps!!! I forgot to mention, dinosaurs and other land creatures grew larger because the oxygen level was higher. Today the oxygen level is 21% 100 million years ago it was about 35%!!! 

[ashcraft]

2 hours ago, Ramon said:

Opps!!! I forgot to mention, dinosaurs and other land creatures grew larger because the oxygen level was higher. Today the oxygen level is 21% 100 million years ago it was about 35%!!! 

 

How would increased oxygen levels lead to larger vertebrates?  Insect size is straight forward because of their passive method of oxygen intake, they can't get larger because they can't get oxygen to tissue.

 

I don't know about vertebrates though.........humans can push a thousand pounds in the right (or wrong) circumstances.

 

I am not trying to be argumentative, but I suspect there is something I am not seeing.

 

Brent Ashcraft

[Sergey Woropaew]

8 hours ago, ashcraft said:

 

So what's the correct answer for that? why sea dinosuars was smaller than land dinosaurs. what stops them to grow? if everything was gigantic in dinosaur era - land predators,insects - all this was gigantic - so we expect that sea creatures was even more bigger than land creatures (because of weight in water).But no- they was smaller.So any straight answer?

Edited January 30, 2017 by Sergey Woropaew

[ashcraft]

You are looking for a simple answer for a complicated subject.  Not going to happen.

 

As far as dinosaurs in the ocean, they were late comers to try and inhabit an already full ocean.  It is very difficult for any species to evolve into a niche that is already occupied.

 

As far as the size of whales, the very largest whales I think are largely filter feeders.  They seem to be remnants of a time when the oceans produced more biomass.  These conditions may not have existed during the Mesozoic.

 

Brent Ashcraft

[aplomado]

On 1/28/2017 at 7:46 PM, Ramon said:

And gravity is the same on water and land, it's just that animals adapt to float and swim.

 

The effect of gravity is reduced in water.  You "weigh" less the amount of the weight of water you displace, as the water bouys you up.  Try standing on a mechanical scale submerged in water and you will see what I mean.  Astronauts train for weightlessness in tanks of water, after all.

[Ramon]

13 hours ago, Sergey Woropaew said:

So what's the correct answer for that? why sea dinosuars was smaller

 

There are no "sea dinosaurs", mosasaurs, plesiosaurs, and other sea reptiles are called that way by many. But, they shouldn't be called like that because they are not members of the Dinosauria. This is also the case for "flying dinosaurs" which are pterosaurs, also not from the Dinosauria. 

 

[ynot]

Hey hi @Sergey Woropaew 

Welcome to TFF!

 

Things that will affect the size limits of a given species....

Available space

Available food

Available oxygen

Genetics

Predators

Environmental conditions

(Have I forgotten any?)

 

All of these things will have an effect on the things living within an ecosystem. When they are all supporting of a larger sized animal (or plant) then one will evolve.

 

Tony

 

[britishcanuk]

Nature doesn't reach for extremes, it simply produces organisms best suited to their niche. We won't ever know what the maximum size of a terrestrial or aquatic creature could be, after all we are only here for a few decades and our fossil record is a mere scratch of the surface. The biggest may be yet to come, may be extant (in the water) or might already be extinct (sauropods). Species only evolve to survive, not to break records. 

[Sergey Woropaew]

thanks for the answers.complicated question Btw i agree, maybe these creatures  not found yet. like 100 meters long (like Amphicoelias but larger). maybe it lives now - https://en.wikipedia.org/wiki/Bloop. who knows:)

Edited January 31, 2017 by Sergey Woropaew

[Sil]

When people talk of the largest, they need to define what they mean too. Sometimes they are meaning mass (weight), girth, length. Today there are jellyfish with tentacles longer than a blue whale, ignoring the fact jellyfish are actually colonies of organisms. In practice on land there is the problem of bodily support which can limit size that is mitigated somewhat by water pressure in the oceans that allow for larger growth there. Mobility comes into play, the bigger you are more bits are exposed to attack by predators so it takes time for that species to evolve in favour of individuals with toxic flesh or faster reflexes and in practice not enough may survive for evolution to shape them this way very often. On land the larger size also means you are more likely to snag or cut yourself in rocks and plants leading to increased rates of infection so again time to evolve armour and better immune systems will limit here too. Bare in mind these are limiting factors, not proof of impossibility.

 

The fossil record is also incomplete. Keep in mind the extraordinary sets of circumstances needed for a creature to die where its body will be preserved by a layer of sediment before scavengers break up and redistribute the carcass or the biomass rots makes for a low chance of a single individual becoming a fossil. Plus tectonics means the planet is always being reshaped so some of the fossil record will have been lost during that process. This means there are still layers of fossils around the world yet to be hinted at simply because humans haven't dug to them yet either. Just like some marine environments became deserts and mountains ranges revealing prehistoric marine creatures, we would have lost some land fossil records to our present day oceans.

 

So prehistoric deep ocean environments may have produced fossils we have yet to reveal, we may have only seen fossil records from depths too shallow to support larger creatures than we currently know about.  We are talking about long time scales and our knowledge isn't perfect. We may have skipped over fossil beds, there's no reason one fossil bed isn't laid on top of layers on top of another bed. We just have literally scratched the surface only as its the easiest and some of the best fossil finds have been from quarries and open cut mines where massive amounts of ground are excavated.

 

Atmospheric composition was different and with our pollution we may be stunting growth possibilities, plus we humans spread everwhere so the creatures of the world don't get to roam so much. It IS interesting that pretty much everything in prehistoric times seemed to grow to large sizes. I would hazard population densities were low so interaction and territoriality may have stayed low too so less stress and plentiful vegetation with a suitable climate and atmosphere allowed individuals to grow to such large sizes. I don't know if we know if these are typical sizes though of outlyers on the bell curve (possibly due to the longer time it would take for them to rot away allows for longer time to get buried naturally to allow fossilisation).

 

The way I look at it is we have yet to find the ultimate super predator (and look forward to future jurassic movies to exploit it), it could just be the largest creatures were something soft and boring like a jellyfish that may not be anywhere preserved as a fossil. Sort of exciting that there is so much yet to discover.

 

 

[Yvie]

Great article,re fossil layers,where I live there are 7 different geological layers due to plate movement,the formation of the English channel and Weald,glaciation,England sinking and Scotland rising,climate change plus who knows what else went on before!!

 

[Boesse]

So two things:

 

1) Don't conflate body length with body mass. Even sauropod dinosaurs have a series of large air sacs lightening up the neck; for dinosaurs will have a much lower amount of mass per unit length relative to marine reptiles.

 

2) It is true that there is a lower maximum body mass observed in marine reptiles and a higher maximum body mass for dinosaurs, suggesting less of an extreme body size difference than in extant mammals. This may reflect physiological differences; we don't know much about the physiology of marine reptiles (IIRC), and many nonavian dinosaurs were not completely endothermic judging from growth studies - I've heard poikilothermic used before.

 

3) Note however that body mass is closely related to sea surface temperature. SST was much higher during the Mesozoic than it is today, or even higher than during the Cenozoic for that matter; cool temperatures permit gigantism in marine mammals, as endotherms produce a lot of excess heat; many whales, dolphins, and pinnipeds are literally too insulated to survive for long periods of time at the equator, for example. In the Miocene we see examples of marine mammal dwarfism, with a smaller body size coinciding with an uptick in temperature. Think of it this way: warm waters will generally "cap" maximum size and lower minimum size, and cool waters will cap minimum size and permit larger sizes. In baleen whales, body size does not really exceed 10-15 meters until the Plio-Pleistocene - so extreme gigantism is a relatively recent development judging from the fossil record.

[FossilDAWG]

It's worth considering that gigantism has a significant cost: it takes a lot of food to attain and maintain an extremely large body size, and it takes a lot longer to attain reproductive maturity.  Often species will evolve a large body size to escape predation.  This may select for some predators to evolve a large body as well, to be able to take very large prey, or alternatively predators may evolve a group (pack) hunting strategy.  Nevertheless, extremely large animals have fewer predators to contend with, compared to smaller animals.  Whether or not animals will evolve large bodies will be strongly influenced by factors including predation pressure, as well as food availability and temperature.  These factors could easily be different in marine and terrestrial environments.

 

Don

[Kane]

(just realized my question was answered earlier in the thread - doh!)