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Living fossil

Adapted from Wikipedia · Discoverer experience

A preserved coelacanth fish on display at the Steinhart Aquarium in San Francisco.

A living fossil is a special kind of animal or plant that looks very much like ancient species we know only from fossils. Scientists use this term for living things that seem almost unchanged from millions of years ago. For example, some fish and plants today look very similar to their relatives from long ago, even though they are not exactly the same species.

The coelacanths were thought to have gone extinct 66 million years ago, until a living specimen belonging to the order was discovered in 1938.

Even though these living fossils look similar to old fossils, they have still changed over time in small ways. This slow change happens because of a process called stasis, where the basic body plan stays the same for a very long time. Scientists now understand that living fossils have evolved, even if it seems like they haven’t changed much.

The idea of a living fossil can be confusing because some people think these creatures have not evolved at all. But scientists know that all living things change slowly through evolution. The term “living fossil” is not used much anymore by experts, as it can give the wrong idea that these plants and animals have not changed over millions of years. In fact, they have evolved in quiet, steady ways, showing how life adapts and survives through time.

Characteristics

Living fossils are special because they look very similar to ancient species found only in fossils. They have changed very little over millions of years. For example, the Ginkgo biloba tree looks almost the same today as it did millions of years ago.

Scientists use the term "living fossil" carefully because it can be confusing. These organisms have stayed mostly unchanged, but their DNA and other features have still evolved over time. Some famous living fossils include the dawn redwood and certain types of fish called Coelacanthiformes. These creatures remind us of how life on Earth has persisted through long periods.

Evolution and living fossils

The term living fossil is used for species that look very similar to ancient species found only in fossils. Scientists have studied why these species change so little over millions of years. Some think these species stay the same because they are well adapted to their environment and don’t need to change much.

Recent studies show that living fossils can still evolve, even if their body shapes stay the same. For example, research on tadpole shrimp shows they continue to adapt to new conditions. Some scientists suggest using a new term, stabilomorph, to describe these species because they adapt very effectively without needing many different forms.

History

Elephant shrews resemble the extinct Leptictidium of Eocene Europe.

The idea of a "living fossil" started with Charles Darwin in 1859. In his famous book, On the Origin of Species, he talked about animals like the platypus and the South American lungfish. He noticed these creatures looked a lot like fossils and had survived for a very long time because they lived in places where there wasn’t a lot of competition from other animals.

Scientists use different ways to decide if an animal is a living fossil. Some look for animals that have been around for millions of years, like the Australian lungfish. Others focus on animals that look very similar to ancient fossils. Some also consider animals that have many old traits or live in only a few places left in the world. These special animals give us clues about how life on Earth has changed — and sometimes stayed the same — over millions of years.

Examples

Some living things are informally called "living fossils" because they look very similar to ancient species found only in fossils.

Protists

Ginkgos not only have existed for a long time, but also have a long life span, with some having an age of over 2,500 years. Six specimens survived the atomic bombing of Hiroshima, 1 to 2 kilometers from ground zero. They still live there today.

Plants

  • Moss
  • Pteridophytes
  • Gymnosperms
    • Conifers
      • Agathis – kauri in New Zealand, Australia and the Pacific and almasiga in the Philippines
      • Araucaria araucana – the monkey puzzle tree (as well as other extant Araucaria species)
      • Sequoioideae - Redwoods (includes the Coast redwood, Sierra redwood and Dawn redwood).
      • Sciadopitys – a unique conifer endemic to Japan known in the fossil record for about 230 million years.
      • Taiwania cryptomerioides – one of the largest tree species in Asia.
      • Wollemia tree (Araucariaceae – a borderline example, related to Agathis and Araucaria)
    • Cycads – although this has been challenged by multiple lines of evidence
    • Ginkgo tree (Ginkgoaceae)
    • Welwitschia
  • Angiosperms
    • Amborella – a plant from New Caledonia, possibly closest to base of the flowering plants
    • Magnolia –_ a genus whose form is little changed since the earliest days of flowering plant evolution in the Cretaceous and possibly earlier
    • Trapa – water caltrops, seeds, and leaves of numerous extinct species are known all the way back to the Cretaceous.
    • Nelumbo – several species of lotus flower are known exclusively from fossils dating back to the Cretaceous.
    • Nymphaeales — includes water lilies; fossils date back to Cretaceous period
    • Sassafras – many fossils of sassafras are known from the late cretaceous through the late Pleistocene.
    • Platanus Sycamore (Plane tree) fossils are very abundant throughout the northern hemisphere with several extinct species. Sycamore leaves and fruits are quite common in plant fossils. They are known from the Cretaceous onwards. Sycamores exhibit many primitive features as well such their exfoliating bark which is a result of a lack of elasticity. Platanus occidentalis fossils are known from the Pliocene and the Pleistocene in North America.
    • Nyssa Blackgum fossils go way back to the late Cretaceous period. Many extinct species are recorded as well.
    • Liriodendron Fossils from the Cretaceous and the Tertiary period are found with many extinct species. Tulip trees at one point were present in Europe during the Cretaceous and the early Paleocene. Liriodendron tulipifera fossils dating from the Pliocene and Pleistocene were discovered at the Chowan formation in North Carolina.
    • Liquidambar Sweetgums appeared during the mid-late Cretaceous and several extinct species are found throughout Asia, Europe and North America. The genus was once widespread in Europe and Asia especially during the Miocene. The American sweetgum is a living fossil itself since fossil specimens dating from the Miocene, Pliocene and Pleistocene were discovered in the eastern United States
Ferns were the dominant plant group in the Jurassic period, with some species, such as Osmunda claytoniana, maintaining evolutionary stasis for at least 180 million years.

Fungi

Animals

Echidnas are one of few mammals to lay eggs.

Vertebrates

Hoatzin hatch with two visible claws on their wings, but the claws fall out once the birds reach maturity.

Invertebrates

Images

A fossilized leaf from the ancient Ginkgo plant, showing how scientists study plants from millions of years ago.
Beautiful ginkgo biloba leaves with their distinctive fan shape.
A Malayan Black Trapdoor Spider, a fascinating species found in Malaysia.
A crocodile in a swamp in Jalisco, Mexico.
A tuatara named Henry, a unique reptile found in New Zealand, shown in its natural habitat.
A rare deep-sea fish known as the goblin shark, displayed in a museum.
A beautiful nautilus shell from Palau, Micronesia, showing its spiral shape.
A horseshoe crab on the beach at Anna Maria Island, Florida.
A Golden toad, an extinct species of amphibian, photographed in its natural habitat.

This article is a child-friendly adaptation of the Wikipedia article on Living fossil, available under CC BY-SA 4.0.

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