It would shrink and basically turn into a predatory ostrich, complete with feathers and with the newfound speed (from reduced weight put on its body) stop being a scavenger, turning into a true predator.
The same goes for all big dinosaurs really, since they could only grow so big due to the circumstances of the era they thrived in. Without them, it's either shrink or die.
That is a hypothetical question so broad it has no single answer. The law of Natural Selection states that as a population of organisms randomly experience mutation, the environment will select those that are the most successful, which will spread throughout the population, gradually changing it. So it depends entirely on what is happening in the T-Rex's environment. If nothing significant changes over the couse of 60 million years, then no new random mutations will be successful, and the T-Rex might not change. Otherwise, it will adapt to the environment, or go extinct.
If you are asking how it might have adapted to the current environment (and every environmental change since then) the answer is based on the fact that the dinosaurs were not as calorie-efficient as modern mammals are. Competition with the mammals, therefore, would likely have driven it to become more mammalian in nature (smaller, more warm-blooded, more intelligent) as time went by (doing this successfully might very well have prevented the evolution of today's top predators, like the lions or tigers). It might look somewhat like a two footed crocodile that can run.
I'm done trying to sound smart. "Clear" is the new smart."Mosasaurus would wipe out todays ocean ecosystem, several species would go extinct in a heartbeat."
Gunna have to disagree there. Species adapt to specific environmental conditions. Once those conditions change, they are no longer well adapted. Im not an expert on mosasaurus, specifically, but Im skeptical it could compete today with species that have had millions of years to adapt to the ocean as it is now.
Edited by DeMarquis on Jul 30th 2019 at 10:03:11 AM
I'm done trying to sound smart. "Clear" is the new smart.I’m a little skeptical a Mosasaurus could comfortably survive in modern oceans. As far as we know they were shallow-water predators and relied on the abundance of other massive marine life to meet their huge food intake needs. They’d probably have some serious trouble feeding themselves these days.
They should have sent a poet.People over emphasize the importance of fighting between animals, esp carnivores. The real competition is energy efficiency—how many calories an animal can afford to expend in order to acquire more. Mosasaurs could swim at some speed for some period of time. If sharks can swim farther faster and consume more prey than mosasaurs can (highly likely), then the mosasaurs will starve and go extinct, even if no shark ever directly encountered a mosasaur. This doesnt even get into such things as changes in ocean temperature and salinity, the presence of new micro-organisms, etc.
Ah, partially
Edited by DeMarquis on Jul 31st 2019 at 8:52:29 AM
I'm done trying to sound smart. "Clear" is the new smart.![]()
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I must admit I went for the opposite; I portrayed Mosasaurus and Tylosaurus and Liopleurodon preying on whales and giant squid.
With ancient creatures surviving in modern ecosystems, it's a bit of a mixed back. For example, a T. Rex would be a solution in search of a problem in today's ecosystem. It was designed to deliver very powerful strikes to large and extremely durable prey animals.
Problem is, nowadays very few prey animals are tough enough to justify a bite like that. A lot of today's animals are, by dinosaur standards, fragile speedsters.
Leviticus 19:34The ocean still holds many large predatory species today, many of them with faster metabolisms and more active hunting habits than your average mosasaur or pliosaur probably had. Predatory megafauna are generally more fragile and less likely to become invasive than smaller predators are - if their main prey species goes away, if they can't cope with the warming oceans, if they start getting hunted by humans, they're going to have a population drop and probably die out. Any evolution in this case would involve the survival of the populations that display the correct traits: better climate tolerance, ability to live away from the human-infested coastal waters, diversification of prey species, and so on.
That's part of the reason things like the Megalodon went extinct: they got outcompeted on their home turf by smaller predators that could subsist on smaller preys, while the cetaceans they used to prey on moved to colder waters.
Edited by eagleoftheninth on Aug 3rd 2019 at 6:26:58 AM
One day, we will read his name in the news and cheer.I've seen some interesting an interesting take on the no KT extinction from Transapient
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Sauropods are nearly extinct as a group due to the rise of grassland ecosystems while hadrosaurs and ceratopsians thrive in them.
Tyrannosaurs have become small to midsized speed hunters while dromaeosaurs have become the main apex predators.
Previous marine reptiles have diminished leaving fully aquatic champsosaurs and marine mammals to fill the oceans.
And the main predators of Australia are terrestrial notosuchians and carnivorous bipedal leptoceratopsids.
Edited by Kaiseror on Aug 8th 2019 at 10:29:00 AM

Let's assume some animals that went extinct suddenly had the chance to contiue evolving, what could happen?
For example, how would A T.Rex evolve in 65 million years time?