Missing link mollusc found, according to reports in ScienceDaily and Nature, 2012; 490 (7418): 94 DOI: 10.1038/nature11328, 3 October 2012. A group of scientists led by Mark Sutton, of Imperial College London, along with researchers from the Universities of Oxford, Leicester, Yale and Queen’s University Belfast have found an unusual fossil mollusc they have named Kulindroplax, derived from the Greek words for a cylinder and a plate. It was found in the Herefordshire Lagerstätte, a deposit of marine creatures dated as 425 million years old, believed to have formed “when a cloud of volcanic ash settled through the Silurian seas and entombed a range of species, including Kulindroplax, as almost perfectly preserved fossils”. They were able to study new fossil’s three dimensional structure in detail by slicing it into 1300 slices, taking digital images of each one, and reconstructing them with a computer.
For many years scientists have debated the evolutionary relationship of two groups of molluscs: the aplacophorans, which are worm-like creatures without shells, and the chitons, which have shell-like armour-plating. The new fossil has a rounded worm-like body with a series of plate-like shells. The researchers believe it is “the missing link showing how worm-like aplacophorans evolved from chiton-like ancestors by losing their shells, providing fresh insight into the mollusc evolutionary tree”. Mark Sutton commented: “Most people don’t realise that molluscs, which have been around for hundreds of millions of years, are an extremely rich and diverse branch of life on Earth. Just as tracing a long lost uncle is important for developing a more complete family tree, unearthing this extremely rare and ancient Kulindroplax fossil is helping us to understand the relationship between two mollusc groups, which is also helping us to understand how molluscs have evolved on Earth.”
Editorial Comment: The fact that this Kulindroplax has a mix of features not seen together in other molluscs does not mean it was in the process of changing from a chiton-like to worm-like creature. It is true that if you already presume evolution then you can slot it between the chitons and the aplacophorans, and claim it is an intermediate, but that is a purely arbitrary exercise. Furthermore, if a mollusc with shell plates did lose plates and change into a mollusc without a shell, that would hardly be evolution. Losing what you already have is a change from complex to simple, which is the opposite of evolution. Showing how chitons got shells in the first place is what the evolutionist really needs to do. At present the data only shows Kulindroplax was a fully formed mollusc that shows no sign of having been anything else. (Ref. invertebrates, fossilisation, devolution)
Evidence News 10 October 2012