WhenTyrannosaurus rexprowled the country , the oceans of the Late Cretaceous were n’t particularly safe either . Cruising the waters at the prison term were large predatory reptiles fuck as mosasaurs , stretch and streamlined for hunting down their prey in the warm shallow sea . Some of these were unfeigned animate being reach up to 18 meter ( 59 feet ) in length , but others were a small more modest . Researchers have revealedthe first mosasaur of its kind to be reveal in Japan , and discovered that it probably hunted at night using binocular vision .
The marine reptile in head is a species calledPhosphorosaurus ponpetelegans , and come in at a relatively diminutive – for mosasaur at least – 3 meters ( 10 feet ) long . The remarkably well preserved skull is the only object lesson known from Japan , and helps palaeontologists fill a geographic opening of the coinage from between the Middle East and the eastern Pacific . It also appropriate the investigator to determine that the animal quite perchance fed on bioluminescent fish and calamari during the nighttime , whilst their larger cousins dominated the sea during the daytime .
“ The forward - face eye onPhosphorosaurusprovide depth perception to vision , and it ’s common in birds of prey and other predatory mammals that consist among us today , ” explains Takuya Konishi in astatement . Konishi is a coauthor of the study , which is write in theJournal of Systematic Palaeontology . “ But we knew already that most mosasaurs were pursuit marauder based on what we know they feed upon – swimming animals . Paradoxically , these small mosasaurs likePhosphorosauruswere not as skillful swimmers as their large contemporaries because their flippers and tail fin were n’t as well developed . ”
But when compared to their larger relatives , the vision ofPhosphorosaurusis markedly different . On the bigger specimen , their eyes are settle on either side of their head – not unlike a gymnastic horse or cervid today – which is think to have helped streamline the reptile and provide it to swim faster to catch the turtles , sharks and other mosasaurs they fed on .
With the smaller mintage , however , the eyes are forward face , which in nocturnal animals doubles the bit of photoreceptors used to detect light . Because fogy of lantern Pisces the Fishes and squid - like animalshave been foundin the same stone shaping in Japan asPhosphorosaurus , the researchers advise that the reptile might have been run at night . They even go on to postulate that perhaps this might have been a larger trend for other metal money of mosasaurs , with the orotund animals hunting and go after down quarry during the day , while the smaller , more vulnerable ones only came out at night .
The mining of the skull that enabled this discovery take in a painstaking two years . It involved dip the rock music in which it was encased in battery-acid overnight , and then washing it off every morning , bit by bit disengage the clappers . These were then piece together to re - make the original skull . The investigator now mean to look into how the species match into the evolutionary tree of mosasaurs .
