I don't care if they tear down trees, I don't feel the hotter breeze...

[gemfyre]

Today on the way home I saw a car that riverstar will be very jealous of. Twas a Prelude in chameleon colour. Bronze and a purplish blue. I really wanted to key it. *grinz*

Glad I actually had the radio on today as I left uni. Traffic report was saying something about a truck rollover on the corner of Yale & Nicholson. I decided not to risk the Bannister/Nicholson intersection (which is nearby) and go the other way. But then I decided, instead of going up Metcalfe and along Albany Highway to the Kenwick Link that I'd turn off High onto Nicholson further up and get straight onto Roe (my favouritest road in the world). So glad I took the alternate route. Traffic banked up along Nicholson, traffic banked up down Roe for ages. I just laughed at 'em.

Then my last car shenanigan for the day. There is a breed of driver on the road that I call a "90-sitter", not a very original name but it will suffice. Most 100kph roads in Perth have 80 zones for traffic lights, or as a token gesture as the Freeway passes through the city. 90-sitters will sit on 90 in the 100 zone and piss everyone else off, and still sit on 90 in the 80 zones, therefore speeding and pissing off all the other drivers. As I headed onto Roe an old Laser roared past me (I woulda been doing around 75/80), but not long after I got up to the speed limit and suddenly he was eating my dust. Moron.

Today's E&C tute was on the Cambrian Explosion/Burgess Shale *squee*. I hadn't done any of the reading but still was one of the main participants in the discussion because, hello, I've been reading this stuff since I could read.

Warning - Educational stuff!

I like the Burgess Shale. It's a deposit of fine shale in Canada. And it has yielded LOADS of fossils. These fossils date from the Cambrian era. Something called the Cambrian Explosion occured, hundreds if not thousands of forms evolved over a remarkably short time. Many of them from families that no longer exist today. Many that completely stumped paleontologists for years.

First up we have Opabinia regalis.

This little curiousity had a chinitous exoskeleton like modern arthropods. It had no legs and it's assumed that it swum by undulating the flap-like structures to it's sides. It has FIVE eyes on the top of it's head. No other creature has that, some creatures have one "eye" or light sensitive spot and as far as I know everything else with eyes has an even number of them. (The New Zealand Tuatara has two regular eyes and a light sensitive spot between them). And then there's that weird trunk thingy at the front end. At first it was thought it had the mouth at the end and worked kind of like a vacuum cleaner. But closer inspection showed that the digestive tract ended under the body (if you look closely you can see the digestive tract, it makes a U shape near the head where it comes out at the mouth). Further investigation has now shown that the extension has a claw on the end, it's pretty much an extra appendage probably used to catch and/or hold prey.

Next is the one with the groovy name - Hallucigenia (you can possibly guess why they called it that.)
First reconstructions of this critter had it walking on a set of spines with a single row of weird looking tentacles along the back and a bulbous head.

It was thought it could maybe be a type of Onycophoran (velvet worm), some Onycophorons live today. It's still thought that Hallucigenia may be of this group, but further research into the fossils produced a much more plausible reconstruction, with the critter walking on a set of tentacles (due to bad fossilisation the tentacles looked to be only one row, but further findings show there were two rows). The spines that it previously walked on now become a defense on it's back.


Wiwaxia was similar to Hallucigenia, it was a wormlike thing with spines on it's back. Also possibly an onycophoran.

I don't know much else about this guy.

Then we come to Anomalocaris.
First of all they discovered fossils like this one...

Radial symmetry, it looked like a jellyfish, and was classified as one.
They also found some weird fossils of prawns but for some reason the heads were always missing.

These were classified as Anomalocaris "Strange prawn".
But after a while some other alarming fossils began to emerge, along with evidence of large chunks bitten out of trilobites.
Turns out that jellyfish was the mouthparts and the prawns the head appendages of a creature about as long as cat and top predator of the seas at the time.

Second pic has some Hallucigenia reconstructions down the bottom too.
It's thought that the presence of this guy in the Cambrian seas encouraged the organisms to try out every permutation of body design available to escape or hide from being eaten.

But for some reason, all these guys died out. There is nothing resembling them today.

One unassuming critter however, called Pikaia also swam these seas. Pikaia was a worm like creature, but he had a special feature. He had a notochord. In fact he resembled the modern Amphioxious or lancelet a lot.

Pikaia's family didn't die out. Human beings possess a notochord. The notochord is what brings all chordates (among them the vertabraes) together.

So, a soft bodied wormy like critter survived, but a formidable predator did not. Who knows why? And who knows what the world would be like now if Anomalocaris had survived instead of Pikaia?

Who knows?

Comments

[delphinbella.livejournal.com]

oooh - love the lesson - it was very interesting today! Im just starting my evolution class, and love learning about all the interesting creatures that evolved and evenutally died out - they are so cool!

Hallucigenia kinda looks like a bristleworm ^_^