Analysis of a well - preserved ancient skull show that ghost sharks — a radical of elusive deep ocean fish with abnormally large eye and wing - like cinque — are descended from a flakey shark - similar Pisces that lived 280 million age ago .
Anew studypublished in the journal Nature is offering unique insight into an strange beast that ’s not often glimpse by human eye . A research squad led by Michael Coates from the University of Chicago Medical Center has found that touch sharks , also known as chimaeras , are descended from a 280 million - twelvemonth - old Pisces dubbed Dwykaselachus oosthuizeni ( pronounced dwike - a - selak - us oos - thwee - acid - ee ) . Not amazingly , these ancient animal were just as strange as their New day descendants .
Chimaeras belong to a family of unusual mystifying - sea Pisces whose body are stiffened not by clappers , but by plates and bone - alike bits of gristle . Though often bear on to as touch sharks , they ’re not actually shark , having diverge from a common ancestor one C of millions of geezerhood ago . These animals , which can grow as long as five infantry in duration , feature large eyes , bird - like fins , and tooth plates used for grate prey . Males have a retractable member - like appendage on their foreheads . maritime biologists estimate that virtually 50 specie of ghost sharks live in the oceans around the world , butsightings have been sparseowing to the animals ’ preference for inscrutable waters .
Very little is do it about chimaeras and their evolutionary origin , but we do know they are class Chondrichthyes , a group of Fish that also include sharks and beam . Scientists have struggled to retrace the ghost shark family tree owe to a dearth of ossified remains ; their bodies are made of cartilage , which does n’t preserve as well as bone . The left physical features of chimaeras , include exceptionally big eyes with orbits ( eye socket ) so bad they actually distort the material body of the brain , are n’t regain in the restrict fogey record .
“ Chimaeroids belong somewhere nigh to the shark and irradiation , but there ’s always been dubiety when you look for deeply in prison term for their evolutionary branching point , ” take down Coates in a statement . “ Chimaeras are unusual throughout the long twosome of their dodo record . Because of this , it ’s been difficult to sympathise how they got to be the agency they are in the first place . ”
A CT scan of a beautifully well - maintain fish , the aforesaid D. oosthuizeni , is finally shed spark on the early phylogeny of shark - comparable fishes , and also on jawed vertebrates as a whole . The skull was found in a careen by a South African inexpert paleontologist in the 1980s , but access to CT scanners and muscular Modern computer rendering engineering science made the fresh analysis potential .
Looking at this skull from the outside , the researchers noted a striking resemblance to a family of prehistorical shark eff as symmoriiforms , which issue over 300 million years ago . These now - nonextant shark featured exaggerated and oddly shaped dorsal louver spines , some resembling glide thunder and others ironing boards . But scans of the skull ’s interior revealed some very chimaera - like characteristics . In fact , these characteristics were so exchangeable to modern day chimaeras that the researchers trust this ancient creature was n’t a shark at all , but a very early ancestor of chimaeras .
In summation to the exceptionally large eye orbits , the researchers document other Chimera - like characteristic , including the tell - tale shapes of the major cranial nerves , nostril , and inner ears . The scan suggest that D. oosthuizeni diverge from symmoriiform sharks , and subsequently evolve into the ghost sharks we see today ( albeit very rarely ) .
The researchers suspect that D. oosthuizeni ’s large orbits may have been an adaption to dimly - lit waters , allowing them to forage for fish in dark conditions . This implies that symmoriiforms adapted to weak - limit condition ( likely deep water ) earlier in evolutionary chronicle than previously thought .
[ Nature ]
EvolutionMarine biologyScience
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