long-lost relative of humans : Xenoturbella
At first glance it looks like a slug worm but don’t be surprised it belongs to the same super phyla Deuterostomia, which also includes human beings .Deuterostomes can be classified into four
* Phylum Chordata (vertebrates and Urochoradata,e.g. Ascidians,Cephalaochordata e.g.Amphioxus)
* Phylum Echinodermata (starfishes, sea urchins, sea cucumbers, etc.)
* Phylum Hemichordata (acorn worms and possibly graptolites)
* Phylum Xenoturbellida (2 species of worm-like animals)
Xenoturbella was first thought to be a relative of bivalve molluscs, such as mussels and oyster,but later the phylogenic data based on nuclear and mitochondrial data allowed Xenoturbella to join elite company of hemichordates and echinoderms as sister group along side vertebrates.
Xenoturbella ,which grows 4cm in length have a very simple body plan for a deuterostome as it lacks brain, proper gut,gonads indicating that it has lost many genes in evolution and or might have lost function.Group of Max Telford has shown that show that, amongst all of the invertebrates that exist, Xenoturbella is one of our very closest relatives.
Xenoturbella is a great addition to the huge diversity of animals found on earth displaying an amazing array of shapes, sizes, colors ,behaviors and body plan.
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