Eric is a science teacher. He teaches paleontology and evolution. He has a special interest in prehistoric times.
Evolution is defined as the change of an organism from a preexisting species. This change can happen to a being to adapt to a new environment. Many creatures are already disappeared due to mass extinction or had been changed, but some continue their goal on earth. The survivor of evolution and mass extinction are called living fossils. They are ancient creatures that did not get extinct, unchanged for millions of years, and are still around in the present time.
This article is about prehistoric animals that are still roaming around. It's about living fossils that appeared on our planet after, during, and before the dinosaurs.
Komodo dragon is the largest and heaviest extant species of lizards in the world. These scaly lizards are found in Indonesia's Lesser Sunda Islands. They evolved from their larger ancestor, Megalania.
Hoatzin or Reptile Bird
Hoatzin is well known for having chicks that have claws on the tip of their wings, a trait similar to the extinct bird Archaeopteryx, which lose when they grow older. This bird exists naturally only in South America, principally in the Amazon jungle.
Elephant shrews were once thought to be related to the shrews. However, after the DNA barcoding result, scientists found out that they are more related to the elephants than to the true shrews. They are officially reclassified to a new order of mammal, Macroscelidea. These little guys that live in Africa evolved from the same ancestor of elephants, manatees, and aardvark, Moeritherium.
Gladiator Bug or Heelwalker
This insect resembles a cross of praying mantis, grasshopper, and stick insect. It was originally considered to be a pure fossil group and was thought to be extinct millions of years ago. However, in 2001, they were discovered alive in Namibia. It was like seeing a fossil come back to life. They have been classified to a new order of the class Insecta, Notoptera.
Goblin shark is the only extant species of the shark family Mitsukurinidae. It is the cousin of the extinct Mesozoic shark Scapanorhynchus, which is the most basal representative of the mackerel sharks. The living specimen was discovered in Japan in 1898.
Tapirs are ancient mammals believed where rhinoceros evolved. There are four extant species of tapir: Baird's tapir (Central America and South America), South American tapir (South America), mountain tapir (S. America), and Malayan tapir (Southeast Asia). They evolved from the same ancestor of horses 65 million years ago.
The frilled shark has very primitive traits like their brown color, eel-like body, and placement of their jaws. This scary-looking swimmer frightens squids and other sea creatures since over 80 million years ago. Today, they are found in the Pacific and the Atlantic oceans.
Alligator Snapping Turtle
Alligator snapping turtles have a dark-brown shell that has spikes similar to the armor of plated dinosaurs giving it a prehistoric appearance. They are the largest freshwater turtles in North America. This genus of turtles appeared on earth 90 million years ago.
Crocodilians lived with dinosaurs, and they were capable of killing and eating the terrible lizard. They survived the worst mass extinctions in the planet's history that wiped out 90% of the creatures during that time. Today, they are distributed in the Americas, Africa, and Asia-Pacific.
False Fairy Wasp
False fairy wasp or fairfly are known as the world's smallest insects in the world whose size range from 0.14 mm to 1 mm. There is little known information about these insects because they are hard to see due to their microscopic size especially when they are flying. The tiny fossils of these bugs were found in the amber from the early Cretaceous period.
The duck-billed platypus and three species of echidna are the only extant mammals that lay eggs. They are weird-looking animals. Echidna have spines on their back to use as defense from their enemy. It has a beak similar to birds, breasts that have no nipple, and a four-headed penis.
The platypus has the bill and feet of a duck, the tail of a beaver, and the body and fur of an otter. The story of the discovery of this critter was funny. When it was introduced to the naturalists, they thought that it was fake and the locals were just fooling around. They believed that it was just made by different animals sewn together.
Both of them are living in Australia. They share the same characteristics as reptiles and mammals. They provide important clues for the evolution and origin of placental mammals.
Purple frogs do not live on the surface of the land, instead, they spend their time burrowing themselves underground, digging, and searching for food. It has tadpoles that have a sucker used to attach themselves to rock, so they won't be carried away by the turbulent flowing stream, unlike the typical tadpoles that swim freely. They evolve to adapt to this environment. This amphibian is endemic to India. They appeared on our planet in the early Cretaceous Period.
This mollusk is neither a squid nor octopus. Although it resembles both, it is classified in a different order, Vampyromorphida. They evolved from shelled-cephalopods such as ammonite and nautilus. Its tentacles are connected by webbing, which used to catch marine snow that it feeds. They live in deep water at depths of 3000m where the oxygen level is very low and the light cannot penetrate.
The members of glypheoidea or Jurassic shrimp are probably the forefather of all decapods (crabs, shrimps, hermit crabs, and lobster). They were known only from fossils until a live one was caught off the coast of the Philippines in 1908. Until then, they were thought to be extinct 50 million years ago. In 2005, a new species, Laurentaeglyphea neocaledonica, was discovered in the Coral Sea near New Caledonia.
Tadpole shrimps have a shield-shaped carapace that conceals the head, long body, and two caudal rami. They look like a hybrid of the horseshoe crab and trilobite. This crustacean has little change since 300 million years ago. They are found in freshwater and brackish water worldwide.
The first appearance of mudskipper is unknown because there are no fossil records for it. However, it is possibly a transitional link between a swimming fish and an amphibian. They are considered the first vertebrates that moved to land and possibly the origin of all four-limbed animals. It is the only known fish that breathe air, lives and walks outside the water, and even climbs trees. 32 recorded species occur on the swamps, mudflat, and estuaries of the Indo-Pacific region.
Like the gladiator bugs and glypheoidea, coelacanths were thought disappeared millions of years ago but this fish-like organism rediscovered in the water of South Africa. In 1997, a new species was found for sale in a local market in Indonesia. They are more closely related to four-limb organisms than swimming fishes. Their fins have flesh and bones. The pelvic and pectoral fins believe was evolved into legs and the middle of the caudal fin turned into a tail. These fish-like creatures follow the oldest living lineage of the lobe-finned fish and terrestrial vertebrates.
Agnathans are jawless fishes and possess a cartilaginous notochord. Most of them are extinct, only two groups are survivors, lampreys, and hagfishes. Hagfishes are only vertebrates that the skeleton is just the skull. Lampreys have a toothed, funnel-like mouth used to suck the blood of their host. These swimmers are probably the first chordate that appeared on our planet. They are considered as the evolutionary link between invertebrates and vertebrates.
The phylum of velvet worms or peripatus, Onychophora, is the only phylum that wholly terrestrial. The representatives resemble a worm with legs. Its progenitor, which is an aquatic peripatus-looking creature, gave rise to the arthropod, tardigrade, nematodes, and this organism. They're found on all continents except Antarctica.
Horseshoe crabs are not actually crabs at all, they are much more closely related to spiders, scorpions, and ticks and are considered the ancestors of the arachnids. It has a hard carapace that is shaped like a horseshoe, hence the name.
Nautiloids are the only member of cephalopods with an external shell. They use their shell as protection from the enemy. The chambered nautilus is the only nautilus that still alive today. Squids, cuttlefish, and octopuses are the products of their evolution.
The Greatest Survivor of Evolution and All Mass Extinction is Either the Comb Jellies or the Sponges
The first animal was probably unicellular and is believed to be evolved from the same ancestor of fungi, the protists. It is an unknown species because most of the animals during the Precambrian era were soft-bodied and easily decomposed so fossils are hard to find.
The oldest recorded animal is Ikaria wariootia discovered in Australia which was multicellular and had a worm-like body, however, this aquatic organism is extinct. The sponge and comb jellies are the candidate for the greatest living prehistoric animals on earth. They are believed to be evolved from the worm-like creature but there is no evolutionary link between them. There is still a debate about which of them came first. They distribute in our ocean from more than half a billion to over a billion years ago.
© 2020 Eric Caunca
Peggy Woods from Houston, Texas on December 17, 2020:
You gave us an interesting assortment of animals and sea creatures to look at and learn about in your article. Thanks!