Wednesday, April 16, 2014

What Tamisiocaris tells us about the history of life

To me, the most important lesson to draw from life of the past is that no era is particularly more advanced than another. Sure, the animals of one era may have features which were absent in the previous (i.e. bones, eyes, etc.), but in general the most advanced periods of each era were stocked with a diverse and unique array of life. What I’m trying to get at is that, to me, it seems that the Cretaceous had just as many dinosaurs as the Miocene had mammals. Different times, different environments, different groups of animals, but neither one was better or more adapted to its surroundings than the other.

Gould's Wonderful Life focuses on the complexity of life in the Burgess
Shale, pictured here. Painting by Carel Brest van Kempen.
Having recently finished Stephen J. Gould’s Wonderful Life, I have a new-found respect for the Cambrian explosion, Paleozoic life, and invertebrates in general. They are some goddamned wacky creatures, more unique and alien than anything else we know. Gould’s main point in Wonderful Life is that the creatures of the Burgess Shale (extrapolate: the mid-late Cambrian) were not simple or ill-equipped to survive by any standards, as was commonly thought. Had cataclysmic extinction events not occurred, they would very well still be swimming the seas, continuing their domination of the world’s oceans.

How can we make such an assumption? Surely their lack of bones and complex eyes and lungs make them inferior to mammals, or reptiles, or even fish. But success and diversity aren’t measures of body parts. They’re measures of niches. The Cambrian was a hotbed of awesome creatures which filled every niche available at the time. There were sponges, worms that preyed on sponges, trilobites, arthropods that looked like trilobites, jellies, scaly urchin-y things, “riddle teeth,” and giant predators measuring a whopping 1m in length. Every niche, from benthic scavengers to macropredators was filled by invertebrates of various phyla, some of which are now completely extinct. 

If that wasn’t enough to convince you that the Cambrian wasn’t an age of failed creatures, one recent discovery will. Tamisiocaris borealis is a newly-found anomalocarid, a relative of the famous Cambrian critter Anomalocaris, one of the world’s first large predators. The anomalocarids all feature “great appendages”* with adaptations which hint at a predator lifestyle, with small spikes and barbs perfect for grasping prey and articulating it into the ventrally-located mouth. What makes Tamisiocaris so special is that, instead of having great appendages for grasping prey, it evolved long, feather-like branches: Tamisiocaris was a filter-feeder.
The great appendage of Tamisiocaris. From Vinter et. al, 2014.

*Yes, this is the actual technical term.

That’s not such a stunning fact now: in the hundreds of millions of years since the Cambrian, filter-feeding has independently evolved across the animal kingdom, from whales to pterosaurs. But in the Cambrian, there was nothing that lived even a remotely close lifestyle. Tamisiocaris was the first creature we know of that evolved from its carnivorous, predatory ancestors to a lifestyle of peaceful planktivory. Instead of noshing on crunchy trilobites near the sea floor, it could glide along in the open ocean, using its huge brush-like great appendages to trap primitive plankton and other tasty vittles.

To me, this is the most exciting fossil found in recent years. Sure, reptiles will always have a special place in my heart, but when we find fossils from the Cambrian, especially ones which totally shake our idea of what it means to be ancient, and not primitive, we view our earth in a much more realistic, and much less mammalian-biased, light. 

Reconstruction of Tamisiocaris and other Cambrian critters by Rob Nicholls.

Tuesday, April 15, 2014

The Sorry-for-the-Absence Post

I can’t believe it’s been five months since I've written here. I kinda have a bad habit of falling in and out of projects… Allow me to try to fix this.

Anyway, lots has been happening in my life since I last wrote here. I’m finally starting to steer my life in the direction of actual biology, instead of slogging my way through classes. I will be heading to Ghost Ranch, New Mexico over the summer to work for a few weeks at the Hayden Quarry in the Chinle Formation, which is unbelievably exciting for me because of the formation's unique Triassic fauna (I’m particularly fond of weird little Vancleavea). I’ve been studying microfossils from the quarry with a professor here, and so far I've found some little bones and scales, which is more than I expected myself to find.

Just yesterday, my first-ever grant was accepted by the field station affiliated with my school. I will be monitoring temperatures in wood duck (Aix sponsa) nest boxes around the field station, as well as examining how temperature, humidity, direct sunlight, and habitat affect the colonization of these nest boxes by the ducks.

So, anyway, that’s what’s been going on with me. But I do hope to get back into writing for the blog. Lots of awesome zoological/paleontological happenings have been… Well, happening. Crocodylians turn out to climb trees more often than we imagine. A new Triassic marine reptile is the first tetrapod to display a “bony tube” of various types of ribs, presumably to protect itself from some of the first giant marine predators. Several new species of dinosaur have been named, including a new Portuguese species of Torvosaurus, the dwarf Arctic tyrannosaur Nanuqsaurus, and Anzu, which I will henceforth refer to as “Satan’s cassowary,” just to add to the list of terrifying (and terrible) bird-related monikers the species has acquired.

So, anyway, I apologize (for, what, the fourth or fifth time now) for the lack of updates. I’ll try my damnedest to keep this going.