I think this is number four. Feel free to correct me if it aint.
In any case...
As noted in our previous installment, placental mammals got their start early. The Early Jurassic as a matter of fact. And they started diversifying back then too.
From the available evidence it would appear that primates were one of the first orders to evolve from the root group. Consider primate senses for example. Primates as a group depend more on their vision than most any other order of mammals. While relying less on their sense of smell. From this it is likely that early primates were the first mammals to venture out into the daytime, and this at a time when the mammals were supposed to be skulking around in the dark hiding from those awful dinosaurs.
Still, it was the dinosaur's world, and so most mammalian groups stayed hidden. Not until the Cretaceous would other orders appear, that we know of. Though evidence is now becoming available pointing to the possibility that old catch-all classification of insectivore never really applied in the first place, and a number of modern day groups first appeared during the Jurassic.
The K/T extinction event changed everything. Even without the asteroid strike it's possible the dinosaurs would've died out anyway. But with the strike on top of the other stressors the dinosaurs pretty much had it. The world was wide open.
The mammals, marsupial and placental both, were in the right place at the right time.
[sidebar]
But what about the monotremes?
The monotremes have always been rare, today is really no different. Modern day monotremes are not very adaptable and breed slowly. The platypus itself is on the thin edge of near extinction, while the echidna is having problems of it's own. In short, all through their history the monotremes have been damn lucky.
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So the mammals diversified with a vengeance. But not really, and not all that much.
Yes, most of the modern orders made their first verifiable appearance during the Paleocene (along with a number now extinct), but during the Paleocene they remained rather primitive.
How primitive?
In some areas the modern platypus is more advanced than the typical Paleocene mammal. In a battle of wits between a Nile Crocodile and an early Paleocene primate, bet on the croc.
Not the most promising group, but compared to such as the suchians and avians, they had potential.
For one thing, they were more adaptable than the contemporaneous crocodilians, and their forelimbs weren't as specialized as those of birds. They were still generalists, and as such could potentially try out most any role possible.
The Paleocene came to an end with another extinction event. With the old, primitive mammals giving way to the first of the modern mammals. Well, more modern than their primitive predeccessors.
This was the age of the rhino and the pig.
At which point I'll bring this installment to and en, since thematically we've just made a big sea change. When next I return to this series we'll be taking a look at primitive rhinos and pigs, as well as early horses, the first examples of Carnivoria, and primates. Till then.
In any case...
As noted in our previous installment, placental mammals got their start early. The Early Jurassic as a matter of fact. And they started diversifying back then too.
From the available evidence it would appear that primates were one of the first orders to evolve from the root group. Consider primate senses for example. Primates as a group depend more on their vision than most any other order of mammals. While relying less on their sense of smell. From this it is likely that early primates were the first mammals to venture out into the daytime, and this at a time when the mammals were supposed to be skulking around in the dark hiding from those awful dinosaurs.
Still, it was the dinosaur's world, and so most mammalian groups stayed hidden. Not until the Cretaceous would other orders appear, that we know of. Though evidence is now becoming available pointing to the possibility that old catch-all classification of insectivore never really applied in the first place, and a number of modern day groups first appeared during the Jurassic.
The K/T extinction event changed everything. Even without the asteroid strike it's possible the dinosaurs would've died out anyway. But with the strike on top of the other stressors the dinosaurs pretty much had it. The world was wide open.
The mammals, marsupial and placental both, were in the right place at the right time.
[sidebar]
But what about the monotremes?
The monotremes have always been rare, today is really no different. Modern day monotremes are not very adaptable and breed slowly. The platypus itself is on the thin edge of near extinction, while the echidna is having problems of it's own. In short, all through their history the monotremes have been damn lucky.
[/sidebar]
So the mammals diversified with a vengeance. But not really, and not all that much.
Yes, most of the modern orders made their first verifiable appearance during the Paleocene (along with a number now extinct), but during the Paleocene they remained rather primitive.
How primitive?
In some areas the modern platypus is more advanced than the typical Paleocene mammal. In a battle of wits between a Nile Crocodile and an early Paleocene primate, bet on the croc.
Not the most promising group, but compared to such as the suchians and avians, they had potential.
For one thing, they were more adaptable than the contemporaneous crocodilians, and their forelimbs weren't as specialized as those of birds. They were still generalists, and as such could potentially try out most any role possible.
The Paleocene came to an end with another extinction event. With the old, primitive mammals giving way to the first of the modern mammals. Well, more modern than their primitive predeccessors.
This was the age of the rhino and the pig.
At which point I'll bring this installment to and en, since thematically we've just made a big sea change. When next I return to this series we'll be taking a look at primitive rhinos and pigs, as well as early horses, the first examples of Carnivoria, and primates. Till then.
