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scientist inChinahave unearthed two marvelously preserved , 160 million - yr - sure-enough lamprey eel fossils — including the largest found to date — shine a light on this group ’s unknown evolutionary history .
Lampreys are one of two living jawless craniate groups that first come along in the fogey track record around 360 million year ago , during theDevonian period(419.2 million to 358.9 million years ago ) . These ancient fish , including 31 mintage alive today , typically have teeth - occupy patsy mouth that they utilize to latch onto prey to excerpt blood and other body fluid .
These Jurassic lampreys have the most powerful “biting structures” among known fossil lampreys and suggest an ancestral flesh-eating habit of living lampreys.
The newly described fossil day of the month to theJurassic period(201.3 million to 145 million years ago ) and bridge a crack between early fossil discoveries and extant lineages . Researchers unearth the specimen from a fossil bed in northeast China and named themYanliaomyzon occisorandY. ingensdentes — their species names intend " Orcinus orca " in Latin and " large dentition " in Greek , respectively .
" These fogey lamprey were delicately preserved with a complete cortege of feeding anatomical structure , " researchers drop a line in a study publish Tuesday ( Oct. 31 ) in the journalNature Communications .
Looking at early fossils , it has long been clear that lampreys have undergone major variety since the Devonian , the authors wrote . But until now , huge gaps in the fossil record think scientists did n’t know when these change occurred .
A Jurassic lampreyYanliaomyzonwith feeding apparatus that surprisingly resembles that of pouched lampreys (Geotria australis).
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Y. occisor , the larger of the two newfound fossils , measured 25.3 inches ( 64.2 centimeters ) long and is the largest lamper eel fogy ever find , according to the study .
Living lamprey species can get much swelled than this , however ; ocean lamper eel ( Petromyzon marinus ) grow up to 4 feet ( 120 cm ) long , andPacific lampreys(Entosphenus tridentatus ) reach up to 2.8 feet ( 85 curium ) .
The early lampreys , on the other mitt , were only a few inches long . They had midget , simple tooth and in all probability no anticoagulant - producing secretory organ , which their modern similitude use to keep their prey ’s blood flowing . The mouthpart of these early lampreys point they were n’t predaceous or even parasitic , the author wrote , but alternatively fed on alga . " Their feeding chance were rather limited because the vast majority of their potential hosts then all had thick scales or armour " that they would not have been able-bodied to penetrate , the researchers added .
The newly described fossil show " extensively notched " mouth , indicate lampreys were preying on other beast at least 160 million years ago , agree to the field . The mouthparts ofY. occisorandY. ingensdentesalso bear a strike resemblance to those of extant pouched lampreys ( Geotria australis ) , point to " an ancestral flesh - corrode habit for innovative lampreys , " the authors compose . This predatory lifestyle in all likelihood led to an increment in lampreys ' eubstance sizing by the Jurassic period , they added .
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lamprey eel also underwent major change in their life history between the Devonian and the Jurassic , according to the subject area . The large sizing ofY. occisorin finical is similar to subsequent species that develop a three - staged life wheel — comprising a larval , metamorphic and grownup phase — indicating it may also have a triphasic hertz and migrated up rivers to spawn .
The breakthrough fills a gap in the evolutionary history of lampreys , throwing light both on changes in the Fish ' eating habits and on the modernisation of their life history during the Jurassic period , allot to the study .
" This history can be divided into two episodes linked by the Jurassic species , " the authors write .
