The Permian Extinction
The Permian Extinction was the greatest extinction event in Earth’s history. Close to 95% of all marine species went extinction, as well as some 85% of all terrestrial life forms. Two of the hardest hit groups among the latter were the therapsids and the thecodonts. This loss in number and diversity opening the way for monotremes and mammals in the case of the former, and pterodactyls, dinosaurs, crocodilians, lung, and dragons in the case of the latter.
There is one possible dragon ancestor from this time. A medium sized crocodile like terrestrial predator that probably weighed about 60 pounds all told. However, it apparently went extinct some 10 million years before the end of the Permian. If it is ancestral to dragons there’s probably one or more transitional forms between it and the first proto-dragons of the Early Triassic.
The Early Triassic
This was a time of transition. The once dominant therapsids and thecodonts were giving way to the new dinosaurs. The new species of therapsids would be smaller, more furtive than their ancestors. Eventually to give way to the early mammals. One line of thecodonts also became small and furtive, but taking to the primitive trees instead of taking up a burrowing life as the therapsids were doing.
They looked much like a modern day lizard, with spawling limbs and a thick tail. They were quadrapeds, the mid-limbs having yet to evolve. Insectivores, they haunting the Triassic forest canopy, making rare trips to the forest floor if they made any at all.
The Mid-Limbs
When mid-limbs appeared among the proto-dragons is not known. Since those proto-dragons with such (not all did, even in the Early Jurassic) had fairly advanced limbs, it is possible the mutation or mutations that gave some proto-dragon lines an extra pair of legs occurred sometime in the Middle or Late Triassic. Just how it happened is a matter of some debate, but recent work on regulatory genes in tetrapods seems to indicate a change to one or more of the family of Vox genes; a group shown to be instrumental in embryological development. So popular recreations of Triassic Era scenes with six-legged ‘lizards’ may not be that far off.
(We now end this look at dragon evolution on the world of Dragon Earth. Next time we’ll be dealing with dragons in the Jurassic, and the threat posed to them by the first primates.)
The Permian Extinction was the greatest extinction event in Earth’s history. Close to 95% of all marine species went extinction, as well as some 85% of all terrestrial life forms. Two of the hardest hit groups among the latter were the therapsids and the thecodonts. This loss in number and diversity opening the way for monotremes and mammals in the case of the former, and pterodactyls, dinosaurs, crocodilians, lung, and dragons in the case of the latter.
There is one possible dragon ancestor from this time. A medium sized crocodile like terrestrial predator that probably weighed about 60 pounds all told. However, it apparently went extinct some 10 million years before the end of the Permian. If it is ancestral to dragons there’s probably one or more transitional forms between it and the first proto-dragons of the Early Triassic.
The Early Triassic
This was a time of transition. The once dominant therapsids and thecodonts were giving way to the new dinosaurs. The new species of therapsids would be smaller, more furtive than their ancestors. Eventually to give way to the early mammals. One line of thecodonts also became small and furtive, but taking to the primitive trees instead of taking up a burrowing life as the therapsids were doing.
They looked much like a modern day lizard, with spawling limbs and a thick tail. They were quadrapeds, the mid-limbs having yet to evolve. Insectivores, they haunting the Triassic forest canopy, making rare trips to the forest floor if they made any at all.
The Mid-Limbs
When mid-limbs appeared among the proto-dragons is not known. Since those proto-dragons with such (not all did, even in the Early Jurassic) had fairly advanced limbs, it is possible the mutation or mutations that gave some proto-dragon lines an extra pair of legs occurred sometime in the Middle or Late Triassic. Just how it happened is a matter of some debate, but recent work on regulatory genes in tetrapods seems to indicate a change to one or more of the family of Vox genes; a group shown to be instrumental in embryological development. So popular recreations of Triassic Era scenes with six-legged ‘lizards’ may not be that far off.
(We now end this look at dragon evolution on the world of Dragon Earth. Next time we’ll be dealing with dragons in the Jurassic, and the threat posed to them by the first primates.)
The whole thing got started as a take off on the Ultimate Guide to... series of specials on the Discovery Channel. Then got morphed into my idiosyncratic version of the Walking with Dinosaurs and Walking with Beasts series from the BBC. It is, in short, a natural history of dragons if dragons existed on a modern day Earth where D&D style dragons could exist.
