#Wolf eel skeleton series#

How did two distantly related lineages stumble upon the same solution? Was there a common template, an ancient developmental program that unfurled in Tarrasius and tetrapod, but was ignored in others? Or did similar selection pressures shape their backbones in similar ways? In other words, is homology or convergence to blame? Yet this particular arrangement of vertebrae only evolved in Tarrasius and in tetrapods. Put this way, it makes perfect sense for a fish to have a segmented vertebral column. The rigid trunk would have controlled the forces generated by the beating tail. Sallan think this unusual anatomy allowed Tarrasius to thrust through the water like a giant tadpole, sweeping its flexible tail from side to side. Its lumbar vertebrae were compact, its sacral vertebrae huge and locked into each other, whereas the vertebrae in its tail were tiny, thin and scattered. While Tarrasius might have looked and lived like a modern eel, it certainly didn't swim like one. Here it stalked the reefs, crushing the shells and carapaces of its prey with its molars, just like modern wolf eels do. It lived between 359 and 318 million years ago, in the shallow waters of what is now Scotland. Far from it, Tarrasius was a small and slender eel-like fish. Tarrasius tells a rather different story: not all animals with necks and sacrums were landlubbers. Like the Tarrasius paper, this research was published today.Ĭase closed, but not quite. Update: computer models indicate Ichthyostega could not walk. Ahlberg speculated Ichthyostega could walk, or at least crawl. This was a departure from the side-to-side wrenching that is so typical of fish. Ahlberg, who reconstructed the Ichthyostegaskeleton in 2005, pointed out that Ichthyostega could probably flex the lumbar region of its spine up and down. The enigmatic Ichthyostega, an ancient amphibian that lived between 375 and 360 million years ago, was amongst the first to waddle around with such a fully 'regionalized axial column'. Since segmented backbones evolved in the early tetrapods that exchanged water for land, paleontologists assumed it was a specific adaptation to a terrestrial life. First up are the cervical vertebrae of the neck, followed by the thoraic vertebrae that carry our ribs, the lumbar vertebrae, the sacral vertebrae wedged between our hip bones and finally the caudal vertebrae of the tail, for those of us that have one. Travel down our spine and you will encounter five distinct types of vertebrae, each with their own place, function and shape.

#Wolf eel skeleton series#

Their vertebral column is a monotonous series of vertebrae strung together, with only minor modifications from head to tail. Modern fish don't have a sacrum, nor do they have a neck or thorax. Its spine was divided into five sections, as it is in every tetrapod, the group of four-limbed, land-dwelling animals that includes humans. Lauren Sallan was peering through her microscope, studying a fossil specimen of Tarrasius, when she noticed something odd. One of them echoed through the halls of the Collections Centre of the National Museum of Scotland, not too long ago: Evolution has a knack for confronting us with strange and unexpected questions.