by Matthew Cobb
I just realised that the perfect counter-point to yesterday’s post about the Ediacara is this excellent Palaeocast podcast with Dr. Alex Liu of the University of Cambridge, who has been studying one of the best-known Ediacaran fossil formations, at Mistaken Point in Newfoundland. This link to the podcast will also take you to a set of fantastic photos by Dr Liu.
You should also read this great post on Mistaken Point by Tony Martin from his terrific blog Life Traces of the Georgia Coast.
The Ediacaran rocks are named after Ediacara in Australia, but there are a number of other key sites around the world that yield bizarre and enigmatic fossils. Mistaken Point – a deep tropical sea bed 565 million years old – is particularly important as it contains many fossils of rangeomorphs. Rangeomorphs look vaguely like ferns, but a) they show a fractal-like structure that is utterly different from a fern and b) they were (apparently) found in the deep ocean. This latter point indicates that they could not have photosynthesised and were therefore probably some kind of animal. With their high surface-area to volume ratio, they could have been osmotrophs, directly absorbing carbon, or perhaps they were some kind of early cnidarian, like a sea pen.
One thing the Mistaken Point biota were not, however, was terrestrial. And here’s a further indication: a trace of an animal, about 1cm wide, moving along the sea-floor from left to right (Tony Martin’s pal Paleontologist Barbie is there for scale):
Martin Brasier, author of the marvellous Darwin’s Lost World (highly recommended) has recently published an article (Open Access! Hooray! – pics below taken from here) in which he has tried to show how rangeomorphs grew, by looking at hundreds of fossils. Here are some examples of what he’s been looking at, followed by his model for how a couple of these life-forms may have grown. By focusing just on the ‘architecture’ (his term) of the rangeomorphs, he and his colleagues think they have provided a new framework for classifying these organisms.
Finally, here’s Brasier from a few years back advertising his excellent book and briefly explaining how he got hooked on pre-Cambrian rocks and their importance for our understanding of evolution: