The depictions of prehistoric beasties in the books of our childhood are something we take for granted. It's not easy to piece together Earth's murky past.
Fragments of bones, weathered footprints, and impressions in rock aren't always the most accurate depictions of the complex, living, breathing animal that passed through or died there.
Researchers sometimes get it wrong while doing this work. Not just a little wrong! Here are some of the fossils that we have learned from.
The lizard has four legs.
There are tiny little feet. The Wikimedia Commons has a CC BY-SA 4.0 license.
In 2015, a paleontological marvel was revealed. Scientists said that the sinuous skeleton was a long-sought fossil. The first discovery of the missing link between snakes and lizards was made by a snake-like body with four tiny legs.
It was celebrated, but not everyone was convinced. The team of paleontologists who re-examining the remains of the Dolichosaurus found that the reptile was not a snake but a member of the extinct group of marine lizards.
The fossil has something to teach us and we expect there to be debate about it. It's well preserved, and may reveal something new about dolichosaurs, whose fossil record is patchy and sparse.
Hallucigenia's head.
The right way around is Hallucigenia. Caron et al., Proc. The Royal Society. B, 2013).
The animals that lived on the Earth during the Cambrian period were very different from what we see today. There are some strange creatures on the ocean floor. The remains were pressed in the lake and later hardened into the shale, preserving enigmatic marks that paleontologists later attempted to interpret.
Hallucigenia was named because it looked like a hallucination. It had at least seven pairs of rigid spikes on its back, seven pairs of weirdly floppy 'legs', and a large head at one end.
Many fossils were found without this head. Why did so many Hallucigenia get decapitated?
The re-examination of the fossil revealed teeth. And eyes. We thought it was its butt. The contents of the animal's guts were squeezed out as it was compressed in the soil.
The good news is that researchers could finally classify Hallucigenia as a lobopodian, the group that gave rise to velvet worms, arthropods, and our beloved tardigrades, because of the sorting out of its ass.
Dickinsonia: animal, vegetable, fungus?
There are Dickinsonia fossils in Australia. The University of Oregon.
Dickinsonia has had a long identity crisis. It was from the Ediacaran era before the emergence of the major phyla we know today. The Ediacaran biota were mostly soft-bodied organisms, and very few of them resemble any living or extinct organisms. They've been difficult to understand.
Dickinsonia looks like a ribbed oval, and it could be anything. It was classified as a type of jellyfish. Scientists think it could be a worm or a mushroom. It has been suggested that Dickinsonia was an extinct kingdom that was neither plant nor animal.
A study a few years ago seems to have solved the problem. The scientists' analysis shows that Dickinsonia is an animal, belonging to either Placazoa or Eumetazoa, which is a step up from sponges.
We had its head and butt around the wrong way. Oops.
Iguanodon had a nose or thumb.
The fossils were found in Bernissart, Belgium. G. Lavette is a public domain person.
Ah, iguanodon. Your thumb-horns are funny. We didn't know where they were supposed to go.
The strange spike was placed atop the beast's nose when it was first described. The rhinoceros has a single horn on its head.
It wouldn't be until over 50 years later that this supposition was exposed. The animal's forelimb was clearly visible in the specimen found in Belgium in 1878. Mantell's assumption is even more correct because we don't know what the spike was used for. Social interaction? Is there a defense against predator? Something to do with food?
It's possible that we won't know, but iguanodon taught us that we shouldn't take things for granted.
Is that an Archaenopeopter?
The feather is controversial. The Museum Natur furkunde.
The earliest known bird is known as Archaeopteryx. It lived around 150 million years ago and is known from just a dozen samples. The identification has been controversial.
Some believe that the animal has been miscategorized, that it was a dinosaur. Individual specimen have been scrutinized.
A team of scientists analyzed a specimen of Archaeopteryx that was originally thought to be a pterodactyl and found it to be an entirely unknown species of theropod dinosaur. The analysis seems to be holding up.
A single feather was reanalyzed in 2019. The researchers found that the specimen was an unknown species, due to the fact that it had a curved quill. In late 2020 a team of paleontologists found that the curvature was incorrect, and in any case, it can be variable.
They said that the feather was found at a site with other Archaeopteryx feathers and that it looked similar to other Archaeopteryx feathers.
We can be pretty sure that we haven't experienced our last Archaeopteryx drama, even if this matter is resolved.
Since the animal is so mysterious, whichever way the debate goes, it will give us an amazing opportunity to learn something new about our world, just like every scrap of fossil our planet has preserved in its wonderful depths.
