Thursday, 30 January 2014

Is This The Mother Of All Spiders?

A Silurian short-great-appendage arthropod

A strange new arthropod beautifully preserved in a nodule of calcite, found in rocks known to geologists as the Wenlock Series Lagerstätte in Herefordshire, UK, may be the ancestor of modern arthropods, including spiders, insects, lobsters, king crabs and scorpions. It has been given the scientific name Enalikter aphson. The arthropods get their name from the fact that they all have jointed legs and an external skeleton, features which evolved very early on. The only other group to evolve jointed limbs were the much later vertebrates with internal skeletons.

Using a technique known as Optical Projection Tomography the team led by Derek J. Siveter of Oxford University Department of Earth Science produced this detailed image from the only known 3D fossil of what are known as the stem-group arthropods, i.e. the group from which other arthropods evolved.

The significance of this find is that it is from rocks known to be 425 million years old, which makes it young by stem-group arthropod standards, being some 100 million years younger than previously found Megacheira (=short-great-appendage) all of which were from the Middle Cambrian era between 480 and 540 million years ago.

The taxonomic position of the Megacheira is controversial: were they stem chelicerates (a later sub-group of arthropods), or stem euarthropods? This specimen, together with another older Megacheira, Bundenbachiellus giganteus, found in Hunsrück Slate in Germany from the Devonian Era, makes it much more likely that the group this new species belonged to were stem euarthropods, in other words, that they were the ancestors of all spiders, lobsters, insects, etc.

Any creationist prepared to hazard an explanation of why an intelligent designer who made everything just the way it is today, would put this fossil of a primitive arthropod so unlike anything else we see today, in a calcite nodule in Herefordshire, UK and made it look 425 million years old?

Derek J. Siveter, Derek E. G. Briggs, David J. Siveter, Mark D. Sutton, David Legg, and Sarah Joomun, A Silurian short-great-appendage arthropod; Proc R Soc B 2014 281: 20132986

'via Blog this'

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1 comment :

  1. Don't know as I'd say it's "so unlike anything else we see today", though. Not to go into structural details, which, not being a biologist, I'm not expert on. But the modern Myriapoda seem to have the same basic structural plan. In fact, the myriapod body structure seems to fit a basal arthropod plan which could be twisted and compressed to create the other arthropod classes.

    It's pointless wasting your breath challenging Creationists. They can't reply rationally so debate is futile.

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