What Animal Has Been Around The Longest
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When we think about the history of life on world and the vast changes that have transpired over millions and millions of years—as single-celled organisms evolved into species every bit disparate every bit redwood trees, dragonflies and humans—are wonderfully apparent. But, amongst all that evolutionary change, some organisms have little modified from their distant ancestors. Creatures such as sharks and crocodiles are often viewed as evolutionary sluggards or "living fossils." While the rest of nature was caught upwards in life'south race, the coelacanth and duck-billed platypus sat things out.
This perception isn't quite correct. Many species of these living fossils differ significantly from their prehistoric counterparts, and often the apparently archaic creatures are the remaining representatives of lineages that were again varied and various. Still, many of these organisms look equally if they belong to some other era. Charles Darwin explained why in his famous book On the Origin of Species: Natural selection may have vastly modified other branches in the tree of life over fourth dimension, merely, among organisms similar the lungfish, the quirks and contingencies of their habitats and lifestyles remained so stable that there was little evolutionary pressure to alter. By take a chance, these lineages occupied an evolutionary sweetness spot. The great Victorian naturalist Thomas Henry Huxley called these creatures "persistent types," but there is an even simpler name for them—survivors.
1. Crocodylians
Watch whatsoever documentary about crocodiles and yous're almost certain to hear the line "They have gone unchanged since the time of the dinosaurs." That isn't exactly true. While crocodylians as we know them today—the alligators, gharials and crocodiles that alive at the water's border—have been around for about 85 million years, they vest to a much more diverse and disparate group of creatures that goes back to the Triassic.
Crocodylians are the final living representatives of the crocodylomorpha, an even bigger group that originated over 205 1000000 years agone. They shared the earth with the dinosaurs and came in a startling array of forms. Some—like the 112-million-yr-erstwhile, approximately xl-human foot-long behemothic Sarcosuchus—looked quite similar to their modern cousins, merely in that location were also formidable ocean-going predators such every bit Dakosaurus; small forms with mammal-similar teeth such as Pakasuchus; crocs with tusks and extra armor such as Armadillosuchus; and lithe, state-dwelling carnivores such as Sebecus. Modern crocs practise expect aboriginal, but they are just the remainders of an even older and stranger lineage.
2. Velvet worm
"Velvet worm" is something of a misnomer. Stretching a quarter of an inch to eight inches long, and flanked by rows of stubby legs along their smooth bodies, these invertebrates aren't worms at all. They vest to their own group, which is more closely related to arthropods, and these inhabitants of the woods undergrowth are part of a much, much older lineage that goes back to one of the greatest evolutionary explosions of all time.
In 1909, secretary of the Smithsonian Institution Charles Doolittle Walcott discovered the brute of the Burgess Shale—exquisitely preserved creatures from a 505-million-twelvemonth-old sea. Many of these animals were dissimilar annihilation seen before, and the true affinities of many of the weird creatures from these deposits are still existence debated. Fifty-fifty so, at least ane creature looked familiar. Aysheaia, an invertebrate named past Walcott in 1911, closely resembles velvet worms and may be close to the group's ancestry. Fifty-fifty though this course lacks some of the specialties seen in modern velvet worms, such equally a unique nozzle arrangement that squirts an instant web over prey, the Cambrian animate being shared the segmented, chubby-legged body plans with living forms. Frustratingly, the soft bodies of velvet worms don't fossilize very well so no one is entirely sure when they emerged onto state for the offset time. Only, if you know what to look for, you can still find them crawling through the leaf litter of tropical forests from Australia to South America.
3. Cow sharks
Most living sharks, from nurse sharks to corking whites, have 5 gill slits on a side. But there are iv species of cow sharks that have six or seven gills, a feature thought to be retained for millions of years from some of the earliest sharks. These deepwater, vi- and seven-gill sharks are considered some of the most archaic of all shark species.
The evolutionary story of sharks is primarily one of teeth. With the exception of rare fossils that preserve remnants of soft parts, teeth are usually all that is preserved from cartilaginous shark bodies. An articulated specimen of the early shark Doliodus problematicus pushes the shark's existence back to at least 409 1000000 years agone, and they are probably fifty-fifty older than that. The lineage to which today's six- and seven-gill sharks vest, however, is more recent. Based upon isolated, saw-blade fossil teeth, paleontologists retrieve moo-cow sharks have existed for at to the lowest degree 175 million years. These deepwater sharks are opportunistic feeders—taking whatever they tin can—and may accept had a stable part as a deep-sea cleanup crew, scavenging on the bodies of marine reptiles during the Mesozoic and shifting to marine mammals subsequently the fourth dimension of the dinosaurs. Nosotros know very little most the appearances of these aboriginal sharks, merely their roughly bladed teeth hint that they have been complete deep-body of water carrion feeders for millions of years.
4. Horsetails
Long-lived lineages of animals often become most of the attention, but there are some survivors among the plants, also. Horsetails must be some of the greatest. These archaic plants are oft constitute growing in patches along streamsides and other moisture habitats. Place a dinosaur toy among them, and the prehistoric model will wait quite at home.
The reason why horsetails are considered and so ancient comes from two lines of evidence. Living horsetails are unique among plants in that they reproduce via spores rather than seeds. Other plants probable gave up this method of reproducing millions and millions of years agone, simply, one-time though information technology may exist, the spore technique makes horsetails resilient and very difficult to remove from places where they are considered weeds. Horsetails also have a very deep fossil tape. Though they brand upwardly small parts of forests at present, enormous horsetails once fabricated up unabridged forests in the days earlier modern trees evolved. In fact, much of the globe's coal, which originates from 360- to 300-one thousand thousand-twelvemonth-old Carboniferous deposits, are the remnants of horsetails such as Calamites that could accept grown to be over 100 anxiety alpine.
v. Lice
Not all the nifty survivors are charismatic. Some of evolution's greatest success stories are parasites, but few have stuck in there longer than lice.
Although louse fossils are rare, in 2004 paleontologists appear that they had constitute a 44-million-year-quondam feather louse that was strikingly like to lice that live on the plumage of waterbirds today. The record of lice probably goes back even farther. Final year, researchers used the few known louse fossils along with genetic comparisons betwixt living lice to make up one's mind when major lice lineages evolved. Plumage lice, in item, seem to have split from their hitchhiking relatives onetime between 115 and 130 one thousand thousand years agone—right when little mammals were scurrying through the Cretaceous undergrowth and feathered dinosaurs were flocking effectually on land. Since feather lice evolved to feed on early birds and plume-covered, non-avian dinosaurs, they have had to change niggling to keep upwardly with their hosts.
6. Brachiopods
Option up a brachiopod and you might recall you're looking at an ordinary mollusk. A crush split into two halves, called valves, protects the invertebrate, but in the case of the brachiopod, these 2 halves are unequal in size. That's how they got their common name—the unequal proportions of the shells make some of the creatures look like old oil lanterns, hence the name "lamp shells."
Whether found in gravel, attached to kelp or clinging to the stone of a continental shelf, brachiopods are relatively rare today. There may exist effectually 100 unlike genera now living, but over five,000 are known from a fossil record spanning 530 million years. By about 488 million years agone, brachiopods had become the dominant shelled animals in the seas—they were then thick in some places that their shells compose most of the sediment other fossils are plant in—but that all changed with the worst mass extinction of all time. This was the Permian mass extinction, which some paleontologists rightly call the "Great Dying" for its catastrophic effect on the planet'south animate being. Though the verbal triggers are yet debated, about 251 one thousand thousand years ago a huge amount of greenhouse gases were dumped into the atmosphere, and the oceans became highly acidic. Brachiopods suffered, giving a foothold to the clam ancestors and cousins of mod clams and cockles. Brachiopods take hung on in whatever crevices they could adhere to just never managed to regain their potency.
7. Ginkgo
Ginkgo trees aren't quite as primitive as horsetails, merely a record of over 175 million years is null to sneeze at. Today these trees are represented only by one species,Ginkgo biloba, only this tree with fan-shaped leaves had its heyday when ferns, cycads and Jurassic dinosaurs dominated the landscape.
ModernGinkgo trees are non very dissimilar from those that herbivorous dinosaurs may have fed on. A recentPaleobiology report by Wesleyan University paleobotanist Dana Royer and colleagues plant thatGinkgo copse seem to do best in disturbed habitats alongside streams and levees, a habitat preference that may have been their downfall. Scientists know from livingGinkgo copse that they abound slowly, starting time reproducing late and are more often than not reproductive slowpokes when compared to more recently evolved lineages of plants that live in the same places.Ginkgo trees may have simply been out-bred by other plants when suitable habitats opened up, just this makes information technology all the more remarkable that one species managed to survive to the present twenty-four hours.
8. Duck-billed platypus
The duck-billed platypus truly looks every bit if it belongs to some other era, if not another planet. In fact, when 19th-century European naturalists get-go saw blimp specimens sent from Australia, some scholars thought the animals must be a joke. But evolution wasn't kidding—hither was a mammal with a duck-like snout and a tail similar a beaver and that laid eggs.
Monotremes, like the platypus, are foreign mammals. These archaic, egg-laying forms final shared a common ancestor with marsupial and placental mammals over 175 1000000 years ago, and rare fossils from Commonwealth of australia indicate that there have been platypus-similar forms since 110 million years agone. Though often reconstructed with a narrower-snout, the Late CretaceousSteropodon was a close cousin of early platypuses. A much closer relative to the modernistic platypus, known asObdurodon, has been found in more recent rocks spanning about 25 to 5 million years ago. This creature is different from its living relative in retaining adult teeth and some particular skull characteristics, but the skull shape is strikingly similar. Rather than being a new kind of animate being that evolved later the dinosaurs, the duck-billed platypus is truly a more primitive kind of mammal with roots that arrive deeper than about other mammals on the planet.
ix. Coelacanth
Coelacanths were supposed to be expressionless. As far every bit early 20th-century paleontologists knew, these distant fishy cousins of ours—categorized as "lobe-finned" fish because of their fatty fins supported by a series of bones like to those in our own limbs—had gone extinct by the end of the Cretaceous, most 66 one thousand thousand years agone, forth with the mosasaurs, pterosaurs, ammonites and non-avian dinosaurs. But information technology in 1938 Marjorie Courtenay-Latimer, a curator at South Africa's Due east London Museum, recognized a very foreign fish lying on a dock after getting a tip most something strange from the deep. As it would turn out, the fish was a living coelacanth—she might as well take found a livingTyrannosaurus.
Paleontologists have discovered fossil coelacanths younger than 65 1000000 years erstwhile since 1938, only, since these were unknown when the fish was re-discovered off Southward Africa, the discovery of a living member of the group immediately catapulted the fish to fame. Two species have since been recognized, and they are different than their prehistoric relatives—enough to belong to a unlike genus,Latimeria—just they are still quite similar to their prehistoric cousins. Creatures recognizable as coelacanths go back to about 400 million years agone, and these fleshy-finned fish were the evolutionary cousins of lungfish and our own archaic forerunners—the very first vertebrates to walk on land were specialized lobe-finned fish related to the recently discoveredTiktaalik. Similar many other organisms on this list, though, living coelacanths are the last of a once again widespread and varied lineage.
x. Horseshoe crab
There is probably no animal that epitomizes the title of "survivor" than the horseshoe crab. With their shield-like carapaces and long, spined tails, these arthropods await prehistoric. When masses of 1 species,Limulus polyphemus, besiege on Mid-Atlantic beaches in the warmth of early summer, information technology is hard not to imagine the scene as something from the deep by.
Exactly when, where and how horseshoe crabs evolved remains a matter of ongoing investigation, but the group of arthropods they belong to is thought to have diverged from their arachnid cousins around 480 1000000 years ago. The basic horseshoe crab torso plan has been around since then, although non exactly in the form we now know. The newly named, 425-million-year-oldDibasterium durgae looked roughly like a horseshoe crab from the top, though if you were to turn the arthropod over, you lot would have been greeted by a nest of double-branched legs used for both animate and locomotion.
Over time, other horseshoe crab species developed other odd adaptations. Creatures like the boomerang-shapedAustrolimilus and the double-push horseshoe crabLiomesaspis represent the extremes in the group'south variation, but it is true that horseshoe crabs as we know them today have been around for a very long time—the 150 one thousand thousand year oldMesolimulus looks like it would fit right in on a Delaware beach. Horseshoe crabs have continued to change since then, of course. The modern Atlantic horseshoe crab is non institute in the fossil record, and the specific group of horseshoe venereal to which it belongs but has a record of most 20 million years. Still, the changes within the group have been astonishingly slight when viewed against the big picture of development. Since the fourth dimension of the horseshoe crab'due south origin, the world has seen several mass extinctions, the ascension and fall of the non-avian dinosaurs and shiftings of continents and climates so drastic that the world truly is a wildly different place. All the while the horseshoe venereal take been in that location, crawling along the seafloor. May they will continue to practise so for millions of years to come up.
Source: https://www.smithsonianmag.com/science-nature/the-top-10-greatest-survivors-of-evolution-118143319/
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