PAST EARTH - The Silurian Period

THE SILURIAN

THE DOMINANCE OF SCORPIO

Leaving the time if evolution and richness, the Silurian earth looks identical to that we just left. Blank, desolate, hot and boring. But look down at your feet. Something amazing has happened in the last few million years. The ground beneath you is green. Thin shoots of primitive plants have appeared, growing upwards towards the baking sun. These small shoots, no higher than a few centimetres are destined to become the tallest trees and deepest forests. Funny to think, as you smile to yourself. But this evolutionary landmark sits amongst a world still hostile to humans and alien to us. Inland as you are, there is no life, just baking rock, dappled with primitive plants in places. Oxygen levels are so low here that without a supply of oxygen a human would die. Plants have not yet laid the corner stone for life.

But next to a narrow stream you come across something interesting. A series of narrow small imprints in the sand. Foot steps of an animal who has braved land, clambering from the ocean. One small step for life on earth. So lets take a plunge into the Silurian sea and find our mysterious land lover.

450 million years into the past of planet earth and the narrow stream we are swimming down is empty. But suddenly out of the murky river water appears a small fish. Perfectly common to us, but at this point in history fish are some of the newest types of life. It's a small fish, no longer than your arm, and its amongst the first creatures in history to have an internal skeleton, the ancestors of all vertebrates from elephants, to dinosaurs, to humans.  This is certainly a landmark era in life. Astraspis [ass-tras-pis] is our fish. Jawless, it has a permanently open mouth, which it sucks small creatures in with. Its curiously blocky head and short tail, with little or no fin to speak off is common for fish at this time. Astraspis is armoured too, with bony plates on its back, glittering blue and silver in the early morning sun. You watch it bury its head in the silty river bed, sifting though the fine particles to locate edible morals beneath. You swim on.

Out to the open ocean and again, life here is flourishing. Astraspis is not the only form of jawless primitive fish in these waters, many exist, all with different shapes and colours, creating seas of plenty like those in the Cambrian. And just like the Cambrian these seas of plenty are harvested by the predatory arthropods. Swimming all around you are sea scorpions, or Eurypterids [your-rip-ter-ids]. These one metre long scorpions have the body shape but bare little resemblance to scorpions on the land from our time. A rounded head sits at the front of a plated body that ends, not in a curled tail but in a flat fan that propels the creatures. The animal's legs fan out behind as it swims, while two sets of spined arms stick out the creature's front. Like all scorpions, its mouth parts are crushing mandibles, needed to destroy the armoured fish that exist here.

Everywhere you look the sea scorpions are, they fill these waters, patrolling like sharks, graceful swimmers and fast. Their razor sharp claws are supreme killing weapons, as you watch one such scorpion rip open an unlucky unarmoured fish, its flesh floating in the water and collected by fish floating near by. In the ocean these armoured arachnids are supreme and agile, but on land they are clumsy and certainly wouldn't be able to make the well laid and neat tracks we saw on the sand. We must move on.

Below on the sea bed there is a common animal here. The Trilobites have remained, although in fewer species than the Cambrian. Many have adapted to the new predators by growing distinct patterns of defensive spines, and some have grown to such huge sizes, more than a metre long, that they are totally impregnable to many predators here. These larger Trilobites remain more to the traditional shape of the Cambrian Trilobites, with no spines or distinct defences. Moving slowly along the sea bed they suck up anything small enough to fit though their mouth parts, and any sea scorpions in the way are quickly removed by a swift head butt. Many animals here have lost their colouration, becoming as drab as their surroundings. The Trilobites have used this effect for many millions of years to camouflage themselves.

Above you float another type of armoured creature. Ammonites. [ammo-nights] These spiral shelled creatures bare resemblance to the Nautilus and squids of modern times. A simple curled shell, drab coloured holds a fleshy body that projects from the end of the shell. With their many tentacles these reddish pink skinned creatures sift though the water, floating on currents. Like the Trilobites below them they will stay around a very long time, being common among the dinosaur's oceans. And like the Trilobites their hard outer shells are a perfect defence. A young Eurypterid swims up and takes several swipes at the armoured giant, who is easily as large as it is. Though gallant his efforts may be, the scorpion's claws can't penetrate the shell, and all he accomplishes is giving the floating creature a bouncy ride. That being said however, the Ammonites are not totally free of risk, and something quickly spooks the sea scorpion away.     

A huge body suddenly strikes out, wrappings it many arms around the ammonite and drawing it to the creatures centre. With a loud crack, the ammonites shell is quickly defeated. It has been caught by an Orthocone [ortho-cone]. These animals are among the top predators in these waters.  They also come in shells, but unlike the ammonites, their shells are long and pointed, like horns, and are streamlined to allow great bursts of speed. The creature inside is again similar to an ammonite, but has much longer tentacles, and as it opens them to engulf another ammonite, a huge rasping beak, that makes short work of the tough Silurian prey. Sea scorpions give these animals a wide berth. This particular Orthocone  is around 5 metres long, and is a young specimen. Her shell is ornately patterned, with spirals of different colour, but many of these colours are not bright. Reds and oranges nestle among creams and browns. It is the fish here that hold the colours in these waters.

Swimming backwards, the Orthocone displays her prominent eyes, while simple compared to the eyes most octopus and squid have in the 21st centaury, they are still useful for finding prey.  Swimming out to deeper waters the youngster starts looking for more prey, and finds an adult Sea Scorpion swimming by. She judges precisely when it gets close enough and darts her arms forward, easily catching hold of the prey. These arms are much different to those in the future. Suckers have not yet evolved and instead the arms are groved and spined to hold onto prey. However scorpion is not going down so easily. Smaller and less armed than the predator that holds it, the scorpion manages to wound the Orthocone arms and she soon decides that this scorpion is not worth the effort. Drifting down lower to the sea bed she hopes to find some more Trilobites, however she quickly finds something much bigger.

Below you stretches the drab brown plated body of the largest Arthropod of all time, Pteregotus              [Tear-re-goat-us]. From tip to tail this one measures over 3 metres long; making it larger than a crocodile. It retains the Eurypterid body shape, with a flat tail, and two sets of forward arms, these ones armed with pincers rather than claws. Its enormous head bulges with eyes made of many lenses, and all of them are focused on the female Orthocone. Snapping its pincers in a loud and scary gesture of strength, the scorpion is clearly not afraid of the juvenile, who splays her arms and snaps her beak in return. Eventually the Pterygotus wins and the female blasts away, kicking up clouds of silt as she does.

The largest of any plated animal, these huge sea scorpions are frightful animals to comprehend, and fiercely carnivorous, a Astraspis that wanders too close is quickly caught in pincers and destroyed. Being so large and armoured makes Pterygotus almost top dog. But there is one big enough to knock it of its perch. The young juvenile Orthocone is not having a good day, and its not likely to get better. Because of their long bodies and simple eyes, keeping an eye on everything around you is tricky if you're an Orthocone and she has missed a danger. From below huge arms lock around her, and she is quickly engulfed towards a beak. Shell and flesh crush, and a small part of her body, the long pointed shell end lands with a soft thump near the Pterygotus, moving it off.

Crunching and crushing the juvenile is a fully grown Orthocone. These adults are well and truly deserving of the title of Giant. They are the top predators here, weighing several tonnes and being at least 12 metres long. A shelled tentacle monster as long as a truck. These giants are the tankers of the open seas, preying on anything stupid enough to venture too far out from the coasts. So large, nothing is save, not even Pterygotus.  The rule of these shelled creatures is however going to be short lived. Swimming back towards the coastline to avoid being eaten yourself by a crushing beak you glimpse something familiar.

A type of jawless fish is swimming amongst crags on the floor when a pincered claw grasps it. It is however, not a sea scorpion. The fish quickly struggles, but is soon put down by a jolt of venom from a arched tail. This is Brontoscorpio. A traditional scorpion by our human standards. Two pincer arms, with another two below its head, 8 legs on a body exactly those of scorpions, and an arched tail with a stinger. However, as we have seen, nothing is ever exactly like the modern day. The stinger that has just punctured the fish is the size of a light bulb; its claws could stretch around your neck with ease. Brontoscorpio is a gilled scorpion over a metre long. It finishes the fish quickly and wanders off. Many of its kind are here, a huge number.  They are all making their way back up the river channel where we started. Their shells are at least slightly more decorative, with blue and white colouration. They march in file down the channel, and fish are quick to move out of the way. Its strange behaviours and your curious as to what they are doing. Soon your curiously is put to rest. As you sit on the river edge, the scorpions advance like an amphibious army out of the water towards a wide open pool behind. While not deep, the ground is moist and the scorpions have come her to lay their eggs. These are the creatures that have taken the first steps onto dry land. Not the ancestors of ourselves, but the Insects.  The true colonists of the land, stepping out from waters full of the scorpions…