We ’ve been getting the mouthpart of theropod dinosaurs likeT. Rexwrong for over a century , a new study claim . If any of their victims had been foolish enough to await back while being chased , they would not have seen some of the most fearsome tooth ever mould coming for them , at least while the theropod ’s mouth was close . Instead , a thin set of scaly “ lips ” hid the revulsion of what was to come .
Palaeontologists face the never - ending job that skin and soft organs seldom fossilise , so animate being must be reconstructed base on ivory and teeth , with a minuscule extrapolation from living species . Once aesthetic renderings are done , they often make up in the general world ’s cognisance and test very heavy for subsequent evidence to sack .
Some of our most iconic dinosaur images involveT. Rexand other vertex predators with exposed teeth , a conclusion possibly establish on the permanent , and not at all reassuring , grinning of the crocodile . However , this view has been challenge in a unexampled report .
A theropod skull, and a comparison of reconstructions using crocodilian-like lipless jaws, or a lizard-like lipped mouth, from two angles. Image credit: Mark P. Witton
Komodo dragons , the other gravid reptilian predator of the modern era , have the grace to hide their sharp tooth behind balmy facial tissues . Dr Thomas Cullen of Auburn University and co - authors wondered if there was any reason to anticipate theropod to be more aligned with crocodilian than Varanidae , other than with child phallus of the former being much more vulgar and familiar today .
We may not have any soft tissue bequest to square off the interrogative , but we do have stack of theropod teeth , and the source take note the enamel on these is comparatively thin . That might not matter if you throw away your tooth oft like a shark , but there is grounds theropods , at least the larger unity , kept their teeth for a longsighted clock time .
That gaveT. Rexand friend ( ok , cousins ) an inducement to search after their incisor . Not possess dental dental floss , and lacking thearmsto apply it anyway , they would have postulate other solutions , the source reasoned . protect mouthparts from the open strain when not in use would have been a good kickoff .
A T. rex eating a juvenile Edmontosaurus looks unfamiliar now the lips have been added. Image credit: Mark P. Witton
Cullen and co - authors compared the skull length and tooth size of various dinosaurs and living reptiles . They also canvass the clothing patterns of the teeth .
The paper concludes bird-footed dinosaur keep open their teeth inside their lip . The lack of control surface clothing on tyrannosaurid teeth in comparison with those of modern crocodiles is especially revelatory . The generator consider this an reading the dinosaurs kept their teeth hydrated with spit , which would have been very ineffective if it meant non - stop drooling . Far more likely that some kind of covering protected the gnashers from the elements . Crocodiles do n’t postulate to do this because they have thick enamel .
Moreover , despite the sizing of some ancient violent death political machine ’ teeth , the tooth - to - jaw proportion indicate keep them protected would have been solely potential . The authors evoke this was done through a solidification of tenuous , scaly lips , known as labial scales .
The authors note that they have found grounds for a “ superficially cheek - like structure ” that cover the teeth of ornithischians . These were herbivorous dinosaurs however , and nothing alike is known for theropods . Moreover , even thoughKomodo dragonsmay wait more like aT. rexthan crocodiles do , they are actually more distant congener .
Nevertheless , the evolutionary distance between theropods and any mintage animated today is so large that bracket out them with crocodiles is probable to be shoddy , and it ’s better to rely on forcible evidence such as tooth vesture .
The study is publish open admission inScience .
