Buzz
The reign of dinosaurs on Earth was vast, stretching over 165 million years, during which they dominated every continent. Their legacy continues to captivate us today. But they weren’t the only beings around. Alongside them were numerous other strange and fascinating species, some of which you may not have heard of.
This list excludes Archosaurs, a group that includes dinosaurs as well as modern birds and crocodiles. While the term used to encompass a wider range of creatures like pterosaurs and ancient marine reptiles, we’ll focus on everything else.
The exact moment dinosaurs first appeared remains unclear, with estimates varying from 250 to 235 million years ago. The first true non-avian dinosaurs emerged around 243 million years ago and vanished 66 million years ago. Any species that could have lived during this period might be considered for inclusion.
Let’s journey back in time and discover some truly strange and remarkable creatures!
10. The Turtle-Like Creature
Sinosaurosphargis yunguiensis lived around 243 million years ago in what is now southwestern China. It had a turtle-like appearance, complete with a broadened ribcage. However, unlike modern turtles, which are shielded by large, tough scales, the ancient turtle-like creatures often had smaller bony deposits known as osteoderms—scale-like structures embedded in the skin.
Despite its appearance, Sinosaurosphargis was not a true turtle. It shared a common ancestor with turtles, but it had branched off from that evolutionary path long before the first real turtles appeared.
Interestingly, the bony covering in Sinosaurosphargis raised some questions about the evolution of the turtle shell, as the ancestors of true turtles did not possess this feature.
9. The Almost Mammal
Scurrying across the dry lands of Late-Triassic France 200 million years ago, the small Megazostrodon might easily be mistaken for an odd rat or shrew. However, this tiny creature holds great importance for many paleontologists.
This little critter is regarded as a transitional form between the mammal-like cynodonts and true mammals, making it a key discovery in the study of mammal evolution. However, its exact position in the mammalian family tree remains debated, as does the question of when mammals officially became mammals.
Megazostrodon was likely far more focused on catching bugs than worrying about its complex place in the evolutionary hierarchy, though.
8. The Tuatara
Alright, I admit, I’m bending the rules here. I’m not talking about the modern tuatara—Sphenodon punctatus—but rather the entire Order of Sphenodontia. I simply couldn’t pick just one species.
The Sphenodontids were well established in the early Jurassic period, nearly 200 million years ago, and once represented a highly diverse group. They belonged to a larger category called Rhynchocephalians, which are the close relatives of modern lizards and snakes. These creatures were essentially an assortment of not-quite-lizards, sharing many similarities in structure but distinct enough to form their own classification.
Sadly, all Rhynchocephalians, except for one genus—Sphenodon—declined and vanished millions of years ago. Today, only the tuatara survives, now endangered due to human activities.
7. The Fish Lizard
Ichthyosaurs, meaning “fish lizard,” were a varied group of marine reptiles that appeared around 250 million years ago.
For this list, I’m highlighting the dolphin-like Stenopterygius, which lived about 180 million years ago. The choice is based on an exceptionally well-preserved specimen that reveals just how bizarre these creatures really were.
This specimen not only preserved remnants of pigment in its skin but also a layer of blubber beneath. While it cannot be definitively classified as warm-blooded, this discovery strengthens the idea that these creatures had some ability to regulate their body temperature, an essential characteristic for a reptile that often plunged into the deep ocean.
At one point, ichthyosaurs were likely among the top predators in the Mesozoic seas. However, they ultimately became extinct about 90 million years ago, 25 million years before the non-avian dinosaurs did.
6. The Beaver-Otter
Castorocauda lutrasimilis is an example of nature repeatedly using similar design principles. Much of its body resembled that of the modern beaver, from its flat, scaly tail to its small webbed feet.
However, this was not an ancient rodent. Its narrow skull was equipped with many sharp teeth designed for catching fish, much like modern otters. Intriguingly, the fur of this 164-million-year-old creature was strikingly similar to that of modern aquatic mammals, complete with guard hairs and a thick undercoat.
Unlike most modern mammals, Castorocauda likely laid eggs, which has led some to propose that its lifestyle could have resembled that of the modern platypus.
5. The Long Lizard
The origin of snakes and the loss of their limbs remains one of the most debated topics in paleontology. So, when a fossil of a serpentine reptile from Brazil mysteriously surfaced in Germany under questionable circumstances (especially since fossil exports have been banned from the country since 1942), many were understandably thrilled.
You see, most of the primitive snakes discovered so far had already begun losing their limbs, retaining no more than a single set. This fossil, however, was different. The discovery of a truly four-limbed snake would have been groundbreaking.
But it wasn’t meant to be. This was Tetrapodophis amplectus, a creature from the Early Cretaceous, about 120 million years ago. And it turned out to be just a very long lizard, not a snake in the slightest.
That’s not to say that this creature contributed nothing to the ongoing discussion. Tetrapodophis was a burrower, and the structure of its tiny limbs has often been compared to those of known early snakes. It’s now believed that snakes ultimately lost their limbs in order to become more skilled at burrowing, just like this little lizard did.
4. Ancient Platypus
Yes, things get even stranger.
Modern monotremes come from a very ancient lineage, although the exact timing of their split from other modern mammals is still uncertain. Estimates suggest this divergence occurred anywhere between the Early Triassic and the Jurassic periods. Nonetheless, the oldest-known relative of the platypus, Teinolophos trusleri, dates back to the Early Cretaceous, around 120 million years ago. After that, many closely related species emerged.
Unfortunately, many of these fossils are incomplete. Still, it’s been proposed that the quirky features of the modern platypus had their origins here. Although only one species of platypus survives today, they were once a much more varied group whose range even extended beyond Australia, as evidenced by the South American Monotrematum sudamericanum.
Also, here’s an interesting tidbit! Another bizarre creature, the echidna, actually diverged from a platypus ancestor anywhere from 20 to 50 million years ago (or possibly even earlier).
3. Primates
Alright, I might be stretching the rules just a bit here.
Technically, one of the earliest primates (or perhaps one of its earliest direct ancestors), Purgatorius janisae, is only known from fossils dating to just after the Cretaceous extinction event. But studies suggest this genus could actually be much older, potentially dating back as far as 81 million years ago. So, I have no qualms about it.
Purgatorius, to be blunt, looked like a cross between a ferret and a squirrel. But it also had the flexible ankle and wrist joints that would become essential for later primates, enabling it to thrive in the treetops, far from the reach of most predators.
And the primates' journey would only get even stranger from here.
2. The “Crazy Beast”
Adalatherium hui must have left quite an impression on its discoverers, given the name it was given. And believe me, it certainly did.
To quote lead researcher David Krause: “Given what we know about the skeletal structure of all living and extinct mammals, it’s hard to imagine how a mammal-like Adalatherium could have evolved; it bends and even shatters a lot of rules.”
In other words, this peculiar creature from Madagascar, which roamed 66 million years ago, was truly, truly bizarre.
To begin with, it had more openings in its skull than any other mammal. Its teeth were unlike anything seen in any other mammal. It also had more vertebrae than any contemporary mammal. Additionally, researchers had quite a challenge figuring out how it moved, as “the front half… doesn’t match the back half.”
And this bizarre seven-pound (3-kilogram) creature was probably just a baby!
1. The Antarctic Sea Dragon
Recently showcased on BBC’s Prehistoric Planet, Kaikaifilu hervei ruled the Antarctic seas during the Late Cretaceous, 66 million years ago. https://www.sciencedirect.com/science/article/abs/pii/S0195667116303123 Kaikaifilu was a mosasaur, a marine reptile most closely related to modern lizards and snakes. More specifically, Kaikaifilu was a type of tylosaurine mosasaur, meaning it had a long, snake-like body compared to the bulkier mosasaurine mosasaurs.
It was estimated to be an impressive 33 feet (10 meters) long, the largest predator from the South Pole, and was likely the top predator in the region. However, its reign was short-lived, as mosasaurs went extinct by the end of the Cretaceous.
