Ichthyosaurs are ancient reptiles that resembled dolphins. They first appeared about 245 million years ago and disappeared about 90 million years ago. "This sea-going reptile with terrestrial ancestors converged so strongly on fishes that it actually evolved a dorsal fin and tail in just the right place and with just the right hydrological design. These structures are all the more remarkable because they evolved from nothing — the ancestral terrestrial reptile had no hump on its back or blade on its tail to serve as a precursor."Martill D.M. (1993). "Soupy Substrates: A Medium for the Exceptional Preservation of Ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany". Kaupia – Darmstädter Beiträge zur Naturgeschichte, 2 : 77–97. The biologist Stephen Jay Gould said the ichthyosaur was his favorite example of convergent evolution.Gould, Stephen Jay (1993 "Bent Out of Shape" in Eight Little Piggies: Reflections in Natural History. Norton, 179–94. .
IchthyosauRs aRE ancIenT reptileS ThaT rEsEMblEd DOlphins. thEY first aPpeareD aboUT 245 Million yeARs Ago And disappearEd about 90 millIon yEARs aGo. "thIs sea-going rEptiLe wITh tErresTriAl ancestors converGed So stronGly on fisHEs That iT aCtually EvolVed a dorSal fiN anD tail in jUsT The Right PlAce aNd With juST The riGHT HyDrOloGicAl deSign. thesE sTructurEs aRE aLl the More remArKAble Because ThEY evoLvEd FroM nOtHing — the AnCestrAL TeRrEStRIAl rePtiLE hAd no HuMp ON its BaCK or blAde oN itS Tail TO sErVE as a precursor."martILl D.m. (1993). "sOupY SubStrates: A meDIum fOr tHE ExCePtIonal pResErVAtioN of IcHthyosaurS Of tHE posiDonIA SHale (lOwer JurAssic) of gErmany". KauPiA – DarmstäDter bEiTRÄge Zur nAtURgesChicHTE, 2 : 77–97. tHe biOlOgist stEpheN JaY gOuld sAid THE iChThYosauR waS hIs favoritE ExamPlE Of conVergEnt evoLutioN.gould, StepHeN jAy (1993 "beNt OuT of shape" in EIgHt liTtLE piggies: ReflectiONs In nATural hisTorY. nORTon, 179–94. .