According to the fossil record, the largest sauropods dwarfed the largest marine vertebrates during the Jurassic and Cretaceous. The largest sauropods reached 30m, while the largest marine vertebrates then only reached 10-12 meters.
In fact the largest theropods were also equal or larger in length and weight than the largest marine vertebrates. The t rex was generally longer and heavier than the mosasaurus hofmanii and thlosaudus proriger. The Mapusaurus was 2 meters longer than the largest kronosaurus.
Doesn't this break the physical rule that the ocean always has the largest animals? Does this mean that mosasaurs and pliosaurs that were the size of blue whales must have existed and that we just haven't found remains of them yet?
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There is no such physical rule though? The largest baleen whales are uniquely large for sea animals and the largest sauropods were uniquely large for land animals, sea animals can theoretically get larger than the largest land animals but most don’t get anywhere that maximum (baleen whales only got uniquely large relatively recently due to the changes in climate and seasonal food concentrations)
There is, due to the fact that gravity has less effect in water, making less structural support needed. Baleen Wells were not uniquely large to see animals Triassic ichtyosaurs achieved similar sizes.
Edit: Damn, for some reason lots of down votes for pointing out an a discrepancy in marine and land max sizes. What's so wrong in that?
The rule holds true for every period except the Jurassic and Cretaceous which seems extremely random and without logical explanation which is why I made this post.
Let's see in which periods the largest marine animals were larger than the largest terrestrial animals; Cambrian: n/a Ordovician: n/a Silurian: largest marine animals larger than largest land animals (arthropods, fish)
Devonian: largest marine animals larger than largest land animals (fish)
Carboniforous: largest marine animals larger then largest land animals (eugeniodontids)
Permian: largest marine animals larger then largest land animals (eugeniodontids)
Triassic: largest marine animals larger than largest land animals (ichtyosaurs)
Jurassic: largest marine animals MUCH SMALLER than largest land animals (pliosaurs, plesiosaurs, ichtyosaurs)
Cretaceous:largest marine animals MUCH SMALLER than largest land animals (lamnids, pliosaurs, plesiosaurs, mosasaurs)
Paleogene:largest marine animals larger than largest land animals(lamnids, primitive whales)
Neogene: largest marine animals larger than largest land animals (lamnids, whales)
The main perplexing thing is that marine vertebrates in the Jurassic and Cretaceous periods had unusually small maximum sizes. It's extremely unusual that the largest marine animal of the Jurassic was as large as a whale shark while the largest one in the Cretaceous was slightly lighter than a grey whale, and barely the length of a Trex.
Somehow according to current findings theropods had less size constraints in the Cretaceous compared to the largest marine vertebrates then.
It wasn't just whales being uniquely large. The otodontid sharks of the Neogene were much larger than the largest mosasaurs and pliosaurs AND sharks during the Jurassic and Cretaceous
You seem to be completely misunderstanding how evolution works. There is no rule that animals automatically get as large as physically possible for their environment. Why are there no land animals since sauropods that got as large as they did? There are multiple factors involved including physiological ones. Why did ichthyosaurs never get as big again as they did in the Triassic? (which while very large was nowhere near as large as the largest blue whales by the way). It’s modern baleen whales, sauropods and Triassic ichthyosaurs that are the historical outliers by some way here and yes, two are marine which isn’t surprising given what we have discussed about physical restrictions. Sauropods could get so large because of their unique anatomy and baleen whales could get so large because of the unique climatic conditions.
I see a lot of posts where an OP acts like evolution is a video game, constantly min/maxing animals and trying follow hard rules.
And they always get argumentative when other Redditors point out they’ve misunderstood evolution are treating it like a directed process.
It's completely ok to be argumentative if the answers to my question are basically "they didn't because they didn't, there's no reason bro". You're acting like animals don't reach specific maximum sizes for no reason and some animals reach specific sizes randomly, when there are always ecological and morphological possibilities and constraints.
And I'll keep asking if there's a reason for the phenomenon I pointed out. If no oneknows hat's ok, but , "there's no reason, it's just because" isn't a good answer.
There are and were no land animals approaching the size of sauropods in the Cenozoic because mammals, due to giving live birth, having less efficient respiratory systems, and less pneumatization of the skeleton had much smaller maximum possible size than dinosaurs in general, let alone sauropods. Avialans and crocodilians also have more limiting morphological size constraints.
That's exactly my question. Ichthyosaurs, pliosaurs and plesiosaurs broke Copes law during the Jurassic.
They do if there's an available niche which necessitates massive size and the animal has the morphological potential to evolve increased size. In the Jurassic and Cretaceous if there were no large marine vertebrates exceeding the size of large theropods, let alone sauropods, that niche must not have existed, but existed in the Triassic and Cenozoic. Why then was there no such niche.
Toothed whales and sharks evolved much larger maximum sizes than mosasaurs and pliosaurs, before baleen whales evolved larger sizes. Baleen whales arent and exception. Why did the former 2 have species reaching over 14m but marine reptiles in the Jurassic and Cretaceous didn't?
It's not that unusual when you look at which groups reach those sizes. Since the K/Pg extinction, only whales and a couple of shark groups have reached atypically large sizes (more than say 7 metres or so). Different groups have different ecological size limits. The Jurassic had Plesiosaurs, thalattosuchians and extremely large Pachycormiformes, with large ichthyosaurs dying out in the early Jurassic. Cretaceous still had very large plesiosaurs and thalattosuchians, as well as extremely large sharks and mosasaurs.
Whales and ichthyosaurs really are outliers here. Thalattosuchians and plesiosaurs would have been some of the biggest marine predators ever when they arrived on the scene. Mosasaurs were also huge but extremely slender in build, and hadn't been around long at all when the asteroid hit.
The flip side is that land happened to be dominated by atypically gigantic dinosaurs. Just because marine organisms have a theoretically higher size limit, it does not mean that all marine groups must be bigger than terrestrial counterparts. If you remove whales, ichthyosaurs and sauropods from the picture, the Jurassic and Cretaceous species suddenly don't seem so small.
It’s not a rule that the ocean has the largest animals, that’s just a generalization based on the fact that there’s a larger maximum size that is possible for life when supported by water.
But the Jurassic and Cretaceous were the only periods of history where that allegedly wasn't the case. Isn't that kind of weird?
The biggest discovered animals. That's the key.
Only something like 0.001% of animals fossilize when they die. Many environments - most of the deep sea, mountains, rainforests - are extremely hostile to fossilization for various environmental reasons. Due to this, it's estimated that we only know 5-10% of species that actually lived in any period in the past.
There is so much that we don't know, and will never know. It's just as likely that there were marine reptiles as big or bigger than the largest sauropods, but we'll never discover them.
That bothers me and keeps me awake. There is so much unknown. I wished the CP extinction didn't happen. There would be a handful creature still a live today.
If that didn't happen then we wouldn't be alive today.
Is that really a bad thing
Depends on who you’re asking
I thought that if there was some planet 68 million light years from us that had a powerful enough telescope they would be able to see the light from the Earth during the Cretaceous and actually see the creatures that existed on the planet. I’m somewhat comforted by that fact.
If we are really lucky some alien civilization has been seeding the galaxy with von neuman probes for hundreds of millions of years and they've been recording life on the planet for ages.
Can you imagine learning there is extra terrestrial intelligence and getting video of dinosaurs on the same day
I feel you 100% dude. It grieves me greatly that we'll never truly know them.
You could go back and fix it. Contact Emmett “Doc” Brown at your earliest convenience. He may have a flux capacitor and a T-Rex available to make the jump.
Is it weird? The Jurassic and Cretaceous are 40% of earths history in which there are Amniotes in terrestrial communities.
So nearly half.
The body sizes of giant terrestrial sauropods also didn't exist on land prior to or after the Jurassic or Cretaceous.
The record in absolutely incomplete, but there is no rule that marine life is always larger than terrestrial life.
Bro. Does. Not. Understand. Sample. Bias
So. Your. Point. Is?
What rule? There’s no rule.
So was there a reason that marine vertebrates had far smaller maximum lengths in the Jurassic and Cretaceous compared to the Triassic and Miocene-Holocene? It wasn't just amniotes, the largest cartilaginous fish of the cenozoic were larger than the largest ones during the Jurassic and Cretaceous.
Obviously there was an ecological reason for the smaller average sizes. Though "small" is a misnomer, as many sea animals hit the 50 ft range in the Jurassic and Cretaceous.
It's just evolution. There are no goals or intent. It's just life filling niches and then going extinct and then repeating. It all depends on the ecological and environmental pressures that exists at any specific time, which will effect what niches need to be filled and which animals evolve the traits to excel in those areas.
It’s important to note that those are only the animals that we’ve discovered. It’s quite possible that there were marine vertebrates that dwarfed the largest dinosaur. We can’t assume that we’ve found everything.
yea most of the plates that were underwater are still underwater
if there were any mind boggling large creatures in the cretaceous oceans, plates still wouldnt have moved them onto solid ground yet, esp if they didnt beach
Not on earth but to WALK on earth.
It’s most likely that even the largest sauropods did not outweigh the most massive animal to ever evolve: the Blue Whale.
I'm talking about when they lived, not compared to now
Coral Colonies:
Wasn't there a theory that some icthyosaurs grew up to as large or larger than blue whales?
In the Triassic yeah.
The species would be shastosaurus
Biggest on land yeth
Counting the ocean?
Icthyotitan and the blue whale look angrily
I'm talking about when the largest sauropods lived lived, i.e. only Jurassic and Cretaceous
Well probably yes i don't know of any marine reptiles during that time that outweight any sauropod
Therefore there's no reason for the pliosaur from walking with dinosaurs to not have existed.
Almost none of the animals from Walking with Dinosaurs actually existed the way they were shown. It was a documentary that took liberties with a lot of animals (even back then). Since then, we also found out a lot more information about various animals from those eras.
There is no rule that ocean animals have to be larger. In fact there are multiple advantages for size that may come up on land that people don't talk about
Most likely there were bigger marine reptiles in the oceans filling the niche of today's large whales.
Niches don’t work like that.
The niche of big whales exists now.
It likely didn’t, atleast not to the extent it is now back then.
I love seeing proper recognition of the tautological basis for the pervasive misuse of ‘niche’ 🥹
Why wouldn't that niche exist back then? Whales are filter feeders that eat plankton and krill, wouldn't these be around in the Mesozoic?
Niches are highly dependant on a large variety of things, including but not limited to; climate, competition, environment, prey variety, prey density, prey quantity and many more. These are all highly volatile, and have and will change constantly. So the niches that exist now, are nothing quite like any that have existed. Even if similar. Especially when we are talking about at a minimum 65 million years.
Ppl will see a tyrannosaurus and say it's survive today even though it's niche wouldn't exist it's just die out ppl don't seem to understand that niches change and appear or disappear. Modern grazers couldn't fill the Fraser niches seen in the Jurassic because it's now a fundamentally different niche due to different predators environment plants etc it's a shame that some many scientifically illiterate ppl exist.