Sharks were n’t always the Brobdingnagian , vicious alpha predators that they are today . Hundreds of millions of class ago , they were just another midget little harmless fish species hang out in lakes and river . So yeah … things have changed slightly since then .
The most striking grounds of shark ’ humble start has been found , in all places , in the primal Asian land of Kyrgyzstan . It ’s toilsome to discover a spot on Earth much further from the ocean , and it ’s been that way for a long time – this region was likewise isolated during the Late Triassic 230 million years ago . And yet it ’s here that paleontologists have found fossilized tooth and egg condensation belong to to the tiny ancient shark Lonchidion ferganensis . you’re able to see some examples of these bollock abridgement fossil down below , along with a Reconstruction Period .
The fogey represent two metal money of ancient shark , one of which go to the hybodontid mob , while the other is have it off as a xenacanthid . These testis capsules represent the first have it away case of sharks reproducing in fresh water – all shark alive today regurgitate alone in the ocean . It ’s unknown whether the parent shark also remained in these ancient lakes and rivers , or whether they mostly go in the open sea , and only swam century of miles upriver for multiply role .
Either way , the fundamental principle of shark reproduction remain unusually unchanged after 230 million eld . While the location has shift from lakes to oceans , the tiny shark of the retiring and jumbo shark of the present both search out shallow waters for spawning . Because shark so seldom fossilize – a by-product of their gristle skeletal frame – this uncovering of even just a few tooth and testis capsules represent one of the biggest hauls in history , as researcher Michael Budwitz explicate :
“ The dodo record of shark is no express mirth thing ; a spine here , a tooth there , or three minuscule denticle [ humble spines of the peel ] picked from a 10 kilogram sample . Therefore , dozens of egg capsule alongside jejune teeth in one deposit is a dream come true ! ”
As for the ancient sharks who leave behind these fossils , we do at least know their ultimate fate . The xenacanthid did n’t make it out of the Triassic , going extinct about 200 million years ago . The hybodontids , on the other manus , bear witness much more successful , hold up until about 65 million years ago , when they likely succumbed to the same mass extinguishing event that wiped out the dinosaur .
Via theJournal of Vertebrate Paleontology . Artist ’s innovation of hybodontid sharks byNobu Tamara .
DinosaurEvolutionFossilPaleontologyScience
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