Dawn of the Therapsids

October 27, 2003 at 12:27 am (Uncategorized)

About 300 million years ago or so, the world was dominated by a species that shared much with reptiles, yet was no longer so easily defined as such. Their jaws, their teeth, their bodies’ means of regulating heat, their lifestyles were all changing, adapting, becoming more and more unlike their reptilian cousins. They stood poised on the edge of dominating the world, when suddenly a massive extinction took place, and of that diverse horde of beasts, only one small surviving remnant of their glory survived.

Sound familiar? We’re not talking about dinosaurs and their sole survivors, the birds. We’re talking the mighty Therapsid empire, of which mammals are the only reminder. (As a side note, it is difficult, if not impossible, for us to know how many species we don’t know about. After all, we only know about a species when we find a fossil of it…for years, until we found ambulocetus, we had no idea how relatives of the mesonychians had managed to move into the water and become whales.)

At the end of the Permian, 90% of all life on earth died. Imagine it. This awsome planet, so thick with life, suddenly nearly wiped clean of things that crawl or swim or buzz, stripped of life in a mass death almost inconceivable to modern minds. An extinction even more brutal than that which crushed the Dinosaurs and led to the foundation of the modern world.

Indeed, there’s a kind of irony there, if you think about it. The rise of the therapsids was the rise of us. We are the therapsids. Mammals and our kind were on the cusp of total world domination at that exact moment when all continents were united, poised to spread and conquer the massive Pangaean land-mass. Replacing the pelycosaurs (such as dimetrodon) as top synapsids, the therapsids dominated the land as the Permian became seasonal (much as, during the Eocene, mammals would rise to dominate the land as the lush worldwide forests declined and the world became seasonal) and spread into a wide variety of roles. Carnivores with poisonous bites, plant eaters, gigantic Dinocephalians (terrible heads) and robust Tapinocephalia, the savage maws of Gorgonopsids like Galesuchus, the ‘cat crocodile’ and the more familiar looking Therocephalians with their more evolved jaw muscles, and finally the Cynodonts themselves, our ‘dog toothed’ ancestors…it was as astonishing, as diverse, as bursting with life as the world has ever been.

Interesting, then, that death stepped in and delivered the world to dinosauria at the end of the Permian. Equally interesting, after some 160 million years of hiding in trees while those self-same dinosaurs ruled the planet, that death should step in and deliver the world back into the hands of the therapsids. I’m sure there’s a rational explanation for this, of course. Possibly massive climate change caused by the formation of a single land-mass, similar to the way the fragmentation of the world’s continents and the southward drift of Antarctica eventually cooled the world’s oceans and killed off some 20% of life on earth at the end of the Eocene, perhaps, but on a more massive scale. That sounds rational enough.

It would be entirely insane to postulate, as an example, that the land empire of the Therapsids somehow engaged in a great war with the seagoing nation of Trilobytes, now wouldn’t it? I mean, the idea of some sort of magical conflict between arthropods and therapsids, or a series of conventional battles (and keep in mind that for all we know the two sides were masters of genetic engineering, or bacteriological warfare…perhaps all the innovations in therapsid jaws was an attempt to breed better and better warriors for the cause) ending in total annihilation…that’s just bizarre. For one thing, it doesn’t take into account that cephalopods fed on trilobytes. Are the modern cephalopods the creations of therapsid geneticists, creating anti-trilobyte weapons in the seas? And for that matter, perhaps the rise of the archosauromorpha was a counter-weapon created by the trilobytes to have a similar effect on their therapsid enemies? It’s interesting to consider that cephalopods have large, powerful brains…but brains totally unlike our own, an intelligence as alien from ours as could be imagined. We often muse that unknowable, alien intelligences may have shaped our world and us…what if our distant ancestors merely started the ball rolling by shaping unknowable, alien intelligences to use as living torpedos against trilobyte enemies lurking in the darkness?

Of course, if we think of cephalopods as bioweapons and archosaurs as doomsday devices that inherited the earth, that does lead one to wonder why after a 160 million year reign they were so rudely displaced. It certainly seems odd to imagine the increased vulcanism and falling rock that ended the age of the dinosaurs as being a manipulation of the ley lines to destablize the world’s telluric energies and cause mass eruptions as part of a plan to summon a rock from the sky, a lapsit ex caelis to strike down the saurians, doesn’t it? I mean, the mammals of that time were barely larger than possums…unless one is willing to either believe in a horde of therapsid ghosts slowly gathering their strength over hundreds of millions of years to strike down their usurpers, or a mammalian mass mind that could tweak gravity sufficiently to snatch death from the sky and the cthonic depths of the underworld, a proto-cerberus of sorts. And that, too, would be crazy.

Yeah, I’ve been kinda weirdly obsessed with paleontology this month. Anyway, just some musing…I may come back and expand it later. Oh, and check this out. The book got a positive review as part of a nifty article. This makes me happy.