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Animals number in all shapes and size , and many have iconic features that make them memorable . From the long neck of Giraffa camelopardalis to the oddly shaped heads of hammerhead sharks , here ’s how 10 singular animalsevolvedtheir signature features .
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1. Turtle shells
For years , scientists debated how turtleneck shells evolved . According to a news report publish in the journalCurrent Biology , paleontologists once believed that the shell was formed through the nuclear fusion reaction of osteoderms — bony deposit that make up the protective scales on crocodile and armadillo . But developmental biologists disagreed with this hypothesis , give how the embryos of modern daylight turtles develop . Instead , they believed the ribs underneath turtle ancestor ' body fuse and gradually unite over the dead body to form the shell .
The disputation was n’t settled until 2008 , when Chinese scientist discover thefossil ofOdontochelys semitestacea , whose name imply " half husk turtle with teeth . " Although the fossilize animal ’s shell was incomplete , it had no osteoderms and demonstrate widening of the ribs , confirming the developmental biologists ' possibility . Scientists say it represents an intermediate step in the phylogeny of the turtle shell . The later stages of evolution are shown in fogy of the genusProganochelys .
2. Giraffes' long necks
Giraffes ' necks can be up to10 pes ( 3 meters ) long , allowing the animal to strain leave luxuriously up in trees . But they did n’t always have this telling feature .
Discokeryx xiezhiis a sheep - size , ancient relative of modern day giraffes that live on around 17 million years ago during the the other Miocene epoch ( 23 million to 5.3 million years ago ) . It had a stumpy neck opening and a disk - influence , thick skull . Scientists in 2022 proposed that the slurred skulls ofD. xiezhievolved to withstand massive blows to the heading during fights between males . Those same round fuel the growth of their neck to assist in fighting . This is call in the " necks for sex " hypothesis and suggest contention led to long necks develop . Male who advance fights more often give-up the ghost these factor onto their offspring than did the unsuccessful person , finally lead to the giraffes we see today .
3. Elephant tusks
Elephants have deeply steady down tusks protruding from their mouths that grow continuously . These tusks are actually tremendous tooth that give the pachyderm anevolutionary advantagewhen dig , lifting objects , stripping bark of Sir Herbert Beerbohm Tree and protecting themselves .
The earliest known tusks are found inDicynodonts , a grouping of stocky , pig - like herbivores that populate 270 million class ago and had unparalleled pointed beaks with protruding tooth on either side .
member of this clade with true tusks were also missing several tooth . Researchers theorize that it may have been more energetically favorable todevelop tusk that continuously mature , rather than replacing teeth that may have fall out . They also suggested that the tusk evolved independently in different population over time . When the tusk developed , soft tissue ligament formed , anchor the large teeth to the jaw .
4. Blue whales' gigantic size
Blue whale ( Balaenoptera musculus ) are the bad animals to have ever live on . Their size makes it unvoiced to believe the mammoth sea mammal evolved from a dog - sized ancestor , Pakicetus . fit in to a 2016 sketch in the journalBiology Letters , the size of baleen whales , including the spicy giant , get significantly over the last 5.3 million years .
One of the main reasons for this accelerated growth is the filter - give behavior of baleen whales , which use bristle - similar teeth to screen out plankton from the ocean . This moderately " peaceful " feeding strategy is tie to a extremely effective metabolic process which let the whales to economise large amounts of vim while traveling long space .
investigator believethe explosive outgrowth of baleen heavyweight started in thePleistocene epoch(2.6 million to 11,700 years ago ) . Nutrient impenetrable overflow from the ice spill into the ocean , creating dense mend of plankton and krill . Thehigh productivityof the sea immix with the low zip - using whales drove a monumental growth spurt in the brute , allowing them to reach the colossal sizes we see today .
5. Tigers' stripes
Panthera tigris stripes change between individuals , much like fingermark in humans . The markings dally an of import role in helping a Panthera tigris persist hidden while hunting prey . The grade insignia help snap off up the form of the fauna ’s body , appropriate it to commingle in with tall grass .
In 1952 , the British Mathematician Alan Turing theorized that a chemical chemical reaction between two homogeneous substances were responsible for the famous tiger - stripe pattern , along with otherpatterns commonly find in nature . He dubbed these gist " morphogens . " One acted as an " activator " and the other as an " inhibitor " — with the " activator " causing a banding to form and the " inhibitor " create a clean blank space .
In 2012 , a field in the journalNature Geneticsexperimentally formalize this hypothesis by identifying the morphogens at period of play in the formation of ridge practice in the mouths of mice .
6. Head of a hammerhead shark
dunce shark famously have trenchant hammer - shaped heads , with jewelled eyes at each last . Ancestors of the hammerheads active today first appeared20 million twelvemonth ago .
It was assumed that the evolution of the hammer - straits develop from a ' normal shaped head ' , so from sharks with a more rounded head that step by step elongated over meter into much larger sharks where the chief is even more defined .
In 2010 , aDNA analysisof eight species of hammerhead shark alive today and of varying sizes revealed that ascendent of hammerhead were very large , around 6.5 human foot ( 2 MiB ) long . scientist hypothesized that modern hammerheads ' outstandingly regulate heads came from big individuals and only later express up in small-scale bodied loggerhead , like the bonnethead ( Sphyrna tiburo ) , as they evolved .
Few theories live to excuse the function of bonehead ' unusual head shape and why it evolved this agency . Some intimate itimproves maneuverability , helps the sharks capture target and even may raise their sense of feel . In a report published in December 2023 in theJournal of Experimental Biology , scientist bear witness that the shark ' broad heads give them well binocular vision , deepness perceptual experience and stereovision than a slimmer - head shark .
7. Rattlesnake rattle
The sound of a rattler ’s tail sends chills down the sticker of anyone that hears it . The noise - make rattle on the tail is made of hollow caps of ceratin that slackly interlock , making strait when the snake excite its tail .
In a2016 report in the journalThe American Naturalist , scientists calculate at 56 snake species from the familiesViperidae(which include rattlesnakes ) andColubridae(one of the largest snake families ) . When exposed to a possible threat , snakes from both family commence shake off and hover the ends of their tails , suggesting a portion out inception of this behavior . The species more closely related to rattlesnakes also shared law of similarity in the continuance and charge per unit of tail vibration .
The research worker behind this study suggested that this widespread Hydra behaviormay have served as " the signal precursor to rattlesnake rattling behavior . “Snakes that shake their tails fastest may have develop callus at the end of their tails to process as a better warning sign to vulture , with this eventually direct to the creation of the rale .
8. Hummingbirds' long bills
The smallest birds in the world , hummingbirds are eff for their bright colors and long pecker that help turn over ambrosia in flowers . Hummingbirds split from swifts — worm - eat on hiss that have unretentive and wider beaks — in Europe 42 million years ago . They then come along in South America around22 million years ago , having germinate a unique taste sensory receptor for sweetness . They also develop a predilection for nectar , according to a 2014 study published in the journalScience .
As a result , hummingbird broadside evolved to better feed on different flower coinage , and competition boosted diversity in card duration and shape .
9. Lobster claws
Lobster - like crustaceans first appearedaround 400 million geezerhood ago . The New creatures have strikingly declamatory , asymmetrical clawswith the larger one being prevailing , like to how humans are either right - handed or left - handed .
Adult lobsters develop a cutter claw withfast fiber musclesthat can snap at a speed of20 millisecondsto help tear and cut off their food . Their other nipper is a short and heavy crusher claw . The crusher chela muscle is made up ofslow muscle fibersthat can exercise apowerful pressure of 100 pounds per square column inch .
Juvenile lobster pincer , on the other hand , are symmetrical and slowly change over prison term as the animals get bigger . The claws bit by bit change in reply to how they are being used .
Clawed lobsters first showed leftover and good - handedness from theEarly Triassic . Theories suggest that this adaptation helped lobsters pry subject or crush shell - creatures during the time of theMesozoic Marine Revolution — a menstruum of time between the Triassic ( 247.2 and 242 million years ago ) and the end of the Cretaceous ( 66 million years ago ) during which marine animal evolved new way of preying on mollusk and there was increased competition for food between predators .
10. Pelican beak pouches
Pelicans are large water birds , known for their long beaks and magnanimous throat pouches that aid them consumeup to 4 pounds ( 1.8 kg ) of fish per 24-hour interval . They scoop bucket of urine , trapping the Pisces the Fishes inside its beak .
— Crabs keep evolving to go from the ocean to the land — and back again
— Human elbow and shoulders evolved as ' bracken ' for climbing ape ancestors
— Caterpillars evolved their eldritch chubby little ' prolegs ' from ancient crustaceans
How this handy prick evolved is a mystery because hooter and bill fogy arerarely found from birds that live in the Paleogene era(between 66 million and 23 million age ago ) . That changed in2010 , when the early know pelican fogey was found with an almost completely continue neb . The pouches of the pelican have changed minimally over the last 30 million years , the researchers find .
Pelicans caneat a massive amount of foodthanks to their pouches , so the discipline authors think this is why they evolved .
