A lot of times I notice most people are at a loss to explain what exactly was on Earth before the dinosaurs... ask them and they just freeze up and draw a blank. Draw a few therapsids and pelycosaurs and you get odd stares and questions like "wait, so that's NOT a dinosaur"? Phytosaurs and rauisuchians: "heh cool, a big gator".
Draw early amphibians of the Coal Age and you get "oh, a big newt. Wait we still have them today, what's so special about that?..." And go back to the Devonian and I swear somebody will mistake a Dunkleosteus for an overgrown Sheepshead or Mahi Mahi. Tell them it ate sharks for breakfast, and watch the eyes roll...
But now take a look at some TRULY ancient creatures. Some of the oldest animal fossils known are from a formation called the Burgess Shale, dating back to the Cambrian period over 500 million years ago. The Burgess Shale provides a valuable window into the ecosystem of some of the first animals. Back then, all life was in the seas. The atmosphere was still far too devoid of oxygen to allow much more than bacteria to survive. Few of the creatures preserved in Burgess bear any resemblance to animals living today, but the Cambrian does have one BIG distinguishing feature - it was the time of the world's first super-predator.
Anomalocaris, the "strange shrimp" of the Cambrian, was an early arthropod distantly related to true shrimps and scorpions. Arthropods would later diversify into insects, arachnids, centipedes and so on, but their first "legend" was this creature. Nearly a meter long (not counting the long tail filaments of some species) it was many times larger than any other Cambrian life form.
It is rumored that this painting is actually based on Laggania,
a smaller relative of Anomalocaris. At top left you can see Pikaia,
the translucent ancestor of vertebrates. That's right, look at our humble beginnings ;)
And this was possibly the ONLY time that a predator dwarfed all other species by such a huge margin. Anomalocaris had no legs, only rows of undulating fins on its sides. Two huge spiny "jaws" raked food into its disk-shaped mouth. It was insatiable, eating anything its monstrous jaws could capture and kill.
Ironically, the first specimens of Anomalocaris were only small parts of it, and were actually described as several different animals! Decades after its initial discovery, the errors were resolved and it turned out Anomalocaris was truly the Godzilla of the ancient seas, dwarfing everything else in sight - it was fifty times larger than the next largest creature of that time (its relative Laggania). Indeed, with the possible exception of the Devonian fish Dunkleosteus, it's probably the only REAL "Godzilla" predator that ever existed in terms of relative scale.
So here for your enjoyment is a somewhat hasty, minimalist scene from the Cambrian, a few hundred miles south of the Burgess Shale.
Two Anomalocaris, hunting for food, seem to soar in an iridescent shallow sea over smaller arthropods like the flat-bodied Helmetia and the compact trilobite Brachyaspidia, as well as a few smaller forms. Also seen are early sponges, the spiky worm Hallucigenia, the strange, urchin-like Wiwaxia and the ten-jawed ambush predator Sanctacaris. There were even odder creatures not pictured here such as Opabinia, a finned "worm" with five eyes and tiny toothed jaws at the end of a long "trunk", and Aysheaia, a soft caterpillar-like creature related to Velvet Worms, that likely ate sponges. (I'm too impatient to post links to these critters. Google them if you're curious!)
Yeah. It was a VERY weird world. Where only the seas had life, the air was toxic, multi-celled plants didn't exist, and a "shrimp" was the undisputed King of Beasts. How's THAT for a romantic time-travel getaway spot!