LIVING FOSSILS
A living fossil is an extant taxon that cosmetically resembles related
species known only from the fossil record. To be considered a living
fossil, the fossil species must be old relative to the time of origin of
the extant clade.
Living fossils are organism that has retained the same form over millions of
years, has few or no living relatives, and represents a sole surviving lineage
from an epoch long past. Many living fossils alive today, like the pig-nosed
turtle and the goblin shark, have unusual traits that make them seem
otherworldly. They have often survived several mass extinctions, and many
scientists consider them to be a rare glimpse into how life on Earth was long
ago.
Examples of Living Fossils
Komodo Dragon
Komodo dragons are the largest and heaviest lizards in the world,
measuring as long as 10 feet and weighting up to 350 pounds. They are the
dominant predators in their habitat, eating almost anything they find.
Sometimes they'll consume up to 80% of their body weight in a single
feeding.
While they are famously named after the Indonesian island of Komodo,
their ancestors first appeared in Australia, some 100 million years ago.
Sandhill Crane
While many birds can trace their ancestry back to dinosaurs,
fossils show that the sandhill crane itself dates back 10
million years.
Sandhill cranes are popular with bird enthusiasts because of
the annual migration of several species. Hundreds of
thousands migrate from Mexico and the southern United
States all the way up to the Arctic.
Aardvak
Aardvarks are nocturnal, burrowing animals and are the only living species in
the order Tubulidentata. Genetically, the animal can be considered a living
fossil because of the ancient arrangement of its chromosomes. Also, its
teeth are unlike any other mammals appearing like clusters of hundreds of
straws standing upright. These little tubes are constantly being worn down
and regrown.
Aardvark fossils dating back 5 million years have been found in South Africa.
Aardvarks are part of the group of animals that includes elephants, hyenas,
and golden moles.
Red Panda
Hailing from the temperate forests of the Himalayas and the
mountains of China, these adorable creatures are the only surviving
members of the family Ailuridae.
They have no living relatives and their nearest fossil relative,
Parailurus, lived 3 to 4 million years ago. In 2020, scientists discovered
that there are two distinct species of red pandas: the Himalayan red
panda and the Chinese red panda.
Relatives of the red panda lived between 5 and 12 million years ago.
Despite their shared taste for bamboo, red pandas are not closely
related to giant pandas.
Tuatara
Tuataras are actually part of a different order called Sphenodontia.
Only two species of tuatara exist today, and they have much the
same form as their ancient ancestors that thrived 200 million years
ago.
There are tuataras alive today that are well over 100 years old, and
some experts believe they could live to be more than 200 years old
under the right conditions. These amazing, long living creatures can
only be found only on small islands off the coast of New Zealand.
Unlike lizards, they enjoy cooler temperatures and are nocturnal.
Nautilus
The nautilus represents the only living member of the subclass Nautiloidea.
Nautiluses are cephalopods that retain an outer shell unlike other distantly
related animals such as squid and octopus.
Their beautiful shells have inspired many artists over the centuries, and they
are also among the finest natural examples of a logarithmic spiral or the golden
ratio.
Because of their long-lasting shells, the fossils of nautiluses are easier to come
by than remains of other cephalopods, and fossil hunters have discovered
ancient shells dating back at least 500 million years.
Purple Frog
Discovered as recently as 2003, this living fossil is also known as the pig-nosed
frog due to its shapely snout. A rare burrowing species, the purple frog is
difficult to find as it is only observed out in the open for short periods of time.
Though found in India, the purple frog’s closest living relatives can only be
observed on the Seychelles Islands, meaning these frogs have been around
for approximately 120 million years dating back to when India, Madagascar,
and Seychelles were connected as a single land mass. Purple frogs are listed
as endangered and their population is decreasing.
Platypus
With a snout like a duck and a hairy body like a mammal, it’s hard to find a
more unique animal than the egg-laying platypus. They have 10 sex
chromosomes instead of two (X and Y) like most other mammals, and are one
of the most venomous mammals in the world. It's no surprise that they are the
sole living representative of the family Ornithorhynchidae.
Fossils of platypus-like mammals date as far back as 100 to 146 million years
ago, making them extremely valuable for studying mammalian evolution.
Hagfish
These animals may look like slimy eels, but many experts don't consider them
to be fish. In fact, some taxonomists are hesitant to consider them
vertebrates, since they are the only living animals that have a skull but not a
vertebral column. From an evolutionary point of view, they can be recognized
from fossils that date back to 330 million years ago, and they represent a
crucial living link between vertebrates and invertebrates.
One descriptor that is not a misnomer is slimy. In fact, hagfish secrete a gooey
slime when handled or threatened, which in the wild helps them to escape
from predators. The slime is a wondrous substance that expands by an
astonishing 10,000 times within a half-second of release.
Hoatzin
These odd-looking, pheasant-sized birds are arguably the most debated living
birds because their evolutionary tree is missing so many branches. The
hoatzin is the only member of its family (Opisthocomidae), though some
taxonomists also place them in their own order. They retain some
characteristics that are not found in any other birds. For instance, as chicks
they still retain claws on the ends of their wings, which aid them in climbing
and clinging to trees.
Evaluation of fossils suggests that hoatzin may have existed as far back as 34
million years ago. Regardless of how they fit into the evolutionary picture,
they are stunning ancient animals found in the Amazon and Orinoco basins of
South America.
Koala
These Australian marsupials are an icon for wildlife across the globe, with a
familiarity that overshadows their uniqueness. Though often referred to as
bears, they are not related to bears at all. In fact, they are members of the
family Phascolarctidae. Their closest relative in the marsupial family is the
wombat, but the species diverged at least 30 million years ago.
As marsupials, they carry their young in a pouch. Fossils of koalas are rare, but
these marsupials have likely been around for at least 30 to 40 million years.
Pig-nosed Turtle
As the only living member of the family Carettochelyidae, the pig-nosed turtle
is one of a kind not just because of its distinctive snout.
Unlike most freshwater turtles, these guys have flippers that more closely
resemble those of marine turtles, making them almost entirely aquatic. This
unique turtle, which was around over 140 million years ago, currently occupies
a small area of southern Australia and northern New Guinea.
Horseshoe Crab
Despite their name, horseshoe crabs are not crabs at all. In fact, they aren't
even crustaceans, being more closely related to arachnids like spiders than to
anything else. But for years, there was doubt about their relationship to
arachnids. In 2019, a team of evolutionary biologists from the University of
Wisconsin-Madison analyzed a collection of genetic data and confirmed that
horseshoe crabs are in fact related to arachnids.
Horseshoe crabs have been around for about 450 million years. They are truly
alien-looking—they even have blue blood. Horseshoe crabs also have a unique
immune system, and studying them has led to breakthroughs in cancer
research and spinal meningitis treatments.
Goblin Shark
The frightening looking goblin shark is an ancient deep sea shark thought to be
closely related to the extinct shark genus Scapanorhynchus, which existed as
long as 66 million years ago. These sharks, which are known for their unusually
long snouts, can grow to over 12 feet in length, but are rarely seen outside of
their deep underwater habitat, usually off the coast of Japan. Goblin sharks
are part of the Lamniformes order of mackerel sharks, which also includes
basking sharks and great white sharks.
Elephant Shrew
Their common name suggests otherwise, but these odd-nosed animals are
not related to shrews. Elephant shrews share a relationship to other distant
and distinct animals such as aardvarks, elephants, and even manatees.
Believed to exist as long as 45 million years ago, the elephant shrew gets its
name from its long movable snout that's similar to a trunk.
A 2020 observation of the Somali elephant-shrew in Africa has encouraged
researchers who thought the species may have been lost. They are
insectivores that release a strong musk from the underside of their tails as
they move along and mark their territory.
Crocodile
No other animal deserves the title of living dinosaur like the crocodile. These
beasts have exhibited the same body form since dinosaurs walked the Earth,
surviving the mass extinctions that wiped out nearly all of their mammoth
brethren.
Crocodiles are also the closest living relatives of birds, representing a longdiverged connection between birds and reptiles. A common ancestor of both
species existed over 240 million years ago. Some evidence suggests that
crocodiles swam from Africa to South America, aided by ocean currents.