frog have been hiding a secret for the last 400 million days . It turns out that the amphibians ' legscontain a kind of kneecap , something that scientist thought only evolved after tetrapods made the move to land full - time , and potentially re - write how we thought the structures first began .
Those of you imagining fully formed kneepan such as the ace found in humans might be a little disappointed , as the kneecaps are basically form from a mass of easygoing fibrous tissue paper . Because they are not ossified , or bony , biologist have never found them in amphibians before , even when using microscope . But one chemical group of investigator were capable to bump grounds of the naive kneecap by analyzing tissue slices taken from the ramification , and published their result inThe Anatomical Record .
It was originally think that the kneecap acquire when tetrapods first amply left the water and started lay eggs on land . The unanimous nature of the patella act in effect as a lever tumbler , aiding in the lifting of the limb as these animals spend their lives traipsing across the terra firma , is mean to have been the driving force as to how they came about in the first place .
But the breakthrough of a primitive kneecap in a radical of animals even more ancient than birds , mammal , or reptiles , might vary why we think the structure first evolved some 400 million years ago . The fact that the kneecap in the amphibian is soft and flexible may offer some clues as to why it first emerge .
“ It does weigh what kneecaps are made out of , ” explains the Royal Veterinary Colleges ’ John Hutchinson , to New Scientist . “ Bone is a well lever , better at resist compression than fibrocartilage , so animals using their kneecaps as levers rather than cushions would benefit from bony patella . ”
Yet even when frogs are rest , their limb ride in the same position as humans leg do when they are about to leap . This means that they are under ceaseless stress , and so necessitate to be good at absorbing these forces . This is likely why the amphibians ' genus Patella are so cushy and fibrous , all the better to occupy the immense amounts of energy from climb up and hopping , and therefore protect the animals ' joint .
Others , however , remained to be win over . Whether or not the patch of tissue identified in the amphibians can be in truth classed as kneecaps is up for public debate , and while the investigator found evidence for these structures in eight species of frogs , it may be premature to accept that all 7,000 specie also have them , and therefore evolved in the ancestor to them all . As always , more body of work will demand to be done .
[ H / T : New Scientist ]
