Reptiles vs Mammals
6/11/2021 / George F. Spicka
One of the things that separate reptiles from mammals is the amount of bones in the lower jaw. Mammals only have one bone on each side. Reptiles have multiple bones which help expand the lower jaws.
This is because of the types of teeth.
Reptiles only have one type in their jaws. Mammals have three: incisors to bite, canines to slash and pull, and molars to chew and grind.
Because of this, reptiles have to swallow their food whole. Mammals can gnaw and chew food into manageable pieces, and don’t need to expand their jaws.
This difference first started to show up in Early Permian Pelycosaurs, the first proto-mammal group, such as Dimetrodon.
By the time of the Late Permian, fossil “reptile” skulls were even found that had Vibrissae (whiskers) pits around the mouth. Vibrissae are compacted hair.
So if reptiles are cold-blooded, then why do they have hair, whose primary function is to keep endothermic mammals warm? When reptiles get cold, they sleep. Most warm-blooded creatures don’t.
It was then discovered that about 10 million years before the Great-Dying (250 mya), Earth had had a major climate event, the Karoo ice-age. We didn’t have another until only 2.5 mya, the Quaternary glaciation. There were 258 or so million years between these ice ages.
(tangent)
That means that through the entire Mesozoic Era (184 million years), and most of the Cenozoic Era (65 million years), Glacial Climates didn’t exist on our planet. That’s an indicator that the cooler clime we live in now is an anomaly. To that can be added the fact that since the most recent ice-age began, researchers have found at least 20 interglacial warming episodes, like the one we’re in now which is called the Holocene Epoch.
I’m not disputing the environmental issue, but when it comes to “Stopping” climate change, how do we halt a natural process that’s been occurring for at least 2.5 million years?
(end-tangent)
The current explanation is that these animals were in fact warm-blooded like mammals. The only reason they are classified as “proto-mammals,” is that their lower jaws jaws contain more then one bone. I wouldn’t be surprised if in the future, evidence of true mammals are found in the Late Permian.
The other fascinating point is that rather then disappear, over time, the extra bones migrated and became part of the mammalian ear.
“The reptilian quadrate bone, articular bone, and columella evolved into the mammalian incus, malleus, and stapes (anvil, hammer, and stirrup), respectively.”
This is because of the types of teeth.
Reptiles only have one type in their jaws. Mammals have three: incisors to bite, canines to slash and pull, and molars to chew and grind.
Because of this, reptiles have to swallow their food whole. Mammals can gnaw and chew food into manageable pieces, and don’t need to expand their jaws.
This difference first started to show up in Early Permian Pelycosaurs, the first proto-mammal group, such as Dimetrodon.
By the time of the Late Permian, fossil “reptile” skulls were even found that had Vibrissae (whiskers) pits around the mouth. Vibrissae are compacted hair.
So if reptiles are cold-blooded, then why do they have hair, whose primary function is to keep endothermic mammals warm? When reptiles get cold, they sleep. Most warm-blooded creatures don’t.
It was then discovered that about 10 million years before the Great-Dying (250 mya), Earth had had a major climate event, the Karoo ice-age. We didn’t have another until only 2.5 mya, the Quaternary glaciation. There were 258 or so million years between these ice ages.
(tangent)
That means that through the entire Mesozoic Era (184 million years), and most of the Cenozoic Era (65 million years), Glacial Climates didn’t exist on our planet. That’s an indicator that the cooler clime we live in now is an anomaly. To that can be added the fact that since the most recent ice-age began, researchers have found at least 20 interglacial warming episodes, like the one we’re in now which is called the Holocene Epoch.
I’m not disputing the environmental issue, but when it comes to “Stopping” climate change, how do we halt a natural process that’s been occurring for at least 2.5 million years?
(end-tangent)
The current explanation is that these animals were in fact warm-blooded like mammals. The only reason they are classified as “proto-mammals,” is that their lower jaws jaws contain more then one bone. I wouldn’t be surprised if in the future, evidence of true mammals are found in the Late Permian.
The other fascinating point is that rather then disappear, over time, the extra bones migrated and became part of the mammalian ear.
“The reptilian quadrate bone, articular bone, and columella evolved into the mammalian incus, malleus, and stapes (anvil, hammer, and stirrup), respectively.”