Hadrosaurs were among the most successful dinosaur family of the later Cretaceous . Were it not for that annoying asteroid / comet they might be the cosmos ’s most common large herbivore today . However , a new breakthrough reveals we ’ve probably been incorrect in some of our thought about key view of their development .
Famous for their duck - similar bills , hadrosaurids dominated North America 73 - 66 million years ago , being far more numerous than the predator that preyed on them and the sauropods that favor size over figure . Last year we see they had justmade it to Africabefore the world as they recognize it came to a crash stop . Who knows how unwashed they might have become there , dedicate more prison term ?
The first hadrosaur fogey were pick up in North America , and it has subsequently been wide consider that this was where they evolved before stamp down much of the world . However , the discovery of a unexampled species , namedYamatosaurus izanagiiinScientific Reports , on the Nipponese island of Awaji throw this into interrogative sentence .
Japan was still bind to Asia 71 - 72 million year ago whenYamatosauruslived – its island position is just 15 million days old . Although dating to near the end of the dinosaurs ' sovereignty , Yamatosaurus ' features indicate it was a comparatively early break - away from more widespread hadrosaur production line . This makes its discoverers consider it more likely that the family ab initio evolved in Asia , and only later migrated to the continent on which they were most successful .
The flatten rostrum that are hadrosaurs most recognizable feature of speech house 100 of tooth , making them hotshot chewers . These tooth were endlessly replaceable , like those of shark , with backups grow in when any tooth wear out from the task of break down so much rugged vegetation .
Yamatosauruswas dissimilar from every other duck-billed dinosaur we have found , with no running replacement available for many of its teeth . Combined with a difference in tooth shape from the hadrosaurus norm , this ledProfessor Yoshitsugu Kobayashiof Hokkaido University Museum to conclude they lived on a different diet from their counterpart , although we do n’t know what that was .
Japan lacks the exposed dodo - racy outcrop that have provided most of our knowledge of the Cretaceous elsewhere , so Kobayashi and carbon monoxide gas - authors were excited when an amateur witness the low jaw , teeth , shoulder and neck and tail vertebrae of aYamatosaurusin an Awaji Island quarry .
Despite this , hadrosaurid fossils have been found on all of Japan ’s four major islands , as well as Awaji , indicating how rough-cut they were . However , jawbones and tooth have testify to be a particularly treasured find .
" These are the first dinosaurs discovered in Japan from the later Cretaceous period , " Kobayashi enunciate in astatement . " Until now , we had no thought what dinosaurs hold out in Japan at the end of the dinosaur old age . "
The shoulder joint bone also essay a significant find . It appear to reveal a species reversing the process that produce us , going from walking on two branch to catch around mostly on four , and suggesting this occurred near the start of the phylogeny of hadrosaurus .
The name commingle an ancient name for Japan and a god credit with create the Japanese islands , with Awaji being first .
