What do we have in common with fish, besides being vertebrates? The types of joints we (and most vertebrates) share most likely originated from the same common ancestor. But it’s not a feature that we share with all vertebrates.
Humans, other land vertebrates, and jawed fish have synovial joints. The lubricated cavity within these joints makes them more mobile and stable because it allows for bones or cartilage to slide against each other without friction, which facilitates movement.
The origin of these joints was uncertain. Now, biologist Neelima Sharma of the University of Chicago and her colleagues have taken a look at which fish form this type of joint. Synovial joints are known to be present in jawed but not jawless fish. This left the question of whether they are just a feature of bony skeletons in general or if they are also found in fish with cartilaginous skeletons, such as sharks and skates (there are no land animals with cartilaginous skeletons).
As Sharma and her team found, cartilaginous fish with jaws, such as the skate embryos they studied, do develop these joints, while jawless fish, such as lampreys and hagfish, lack them.
So what could this mean? If jawed fish have synovial joints in common with all jawed vertebrates, including us, it must have evolved in our shared ancestor.
Something fishy in our past
While the common ancestor of vertebrates with synovial joints is still a mystery, the oldest specimen with evidence of these joints is Bothriolepis canadensis, a fish that lived about 387 to 360 million years ago during the Middle to Late Devonian period.
When using CT scanning to study a Bothriolepis fossil, Sharma observed a joint cavity between the shoulder and pectoral fin. Whether the cavity was filled with synovial fluid or cartilage is impossible to tell, but either way, she thinks it appears to have functioned like a synovial joint would. Fossils of early jawless fish, in contrast, lack any signs of synovial joints.
Also: Baby megalodons were likely the size of great white sharks and capable of hunting marine mammals
The giant extinct shark species known as the megalodon has captured the interest of scientists and the general public alike, even inspiring the 2018 blockbuster film The Meg. The species lived some 3.6 million years ago and no complete skeleton has yet been found. So there has been considerable debate among paleobiologists about megalodon’s size, body shape and swimming speed, among other characteristics.
While some researchers have compared megalodon to a gigantic version of the stocky great white shark, others believe the species had a more slender body shape. A new paper published in the journal Palaeontologia Electronica bolsters the latter viewpoint, also drawing conclusions about the megalodon’s body mass, swimming speed (based on hydrodynamic principles), and growth patterns.
As previously reported, the largest shark alive today, reaching up to 20 meters long, is the whale shark, a sedate filter feeder. As recently as 4 million years ago, however, sharks of that scale likely included the fast-moving predator megalodon (formally Otodus megalodon). Due to incomplete fossil data, we’re not entirely sure how large megalodons were and can only make inferences based on some of their living relatives.
Thanks to research published in 2023 on its fossilized teeth, we’re now fairly confident that megalodon shared something else with these relatives: it wasn’t entirely cold-blooded and kept its body temperature above that of the surrounding ocean. Most sharks, like most fish, are ectothermic, meaning that their body temperatures match those of the surrounding water. But a handful of species, part of a group termed mackerel sharks, are endothermic: They have a specialized pattern of blood circulation that helps retain some of the heat their muscles produce. This enables them to keep some body parts at a higher temperature than their surroundings.
Of particular relevance to this latest paper is a 2022 study by Jack Cooper of Swansea University in the UK and his co-authors. In 2020, the team reconstructed a 2D model of the megalodon, basing the dimensions on similar existing shark species. The researchers followed up in 2022 with a reconstructed 3D model, extrapolating the dimensions from a megalodon specimen (a vertebral column) in Belgium. Cooper concluded that a megalodon would have been a stocky, powerful shark—measuring some 52 feet (16 meters) in length with a body mass of 67.86 tons—able to execute bursts of high speed to attack prey, much like the significantly smaller great white shark.
(H) One of the largest vertebrae of Otodus megalodon; (I and J) CT scans showing cross-sectional views. Credit: Shimada et al., 2025
Not everyone agreed, however, Last year, a team of 26 shark experts led by Kesnshu Shimada, a paleobiologist at DePaul University, further challenged the great white shark comparison, arguing that the super-sized creature’s body was more slender and possibly even longer than researchers previously thought. The team concluded that based on the spinal column, the combination of a great white build with the megalodon’s much longer length would have simply proved too cumbersome.
A fresh approach
Now Shimada is back with a fresh analysis, employing a new method that he says provides independent lines of evidence for the megalodon’s slender build. “Our new study does not use the modern great white shark as a model, but rather simply asks, ‘How long were the head and tail based on the trunk [length] represented by the fossil vertebral column?’ using the general body plan seen collectively in living and fossil sharks,” Shimada told Ars.
Shimada and his co-authors measured the proportions of 145 modern and 20 extinct species of shark, particularly the head, trunk, and tail relative to total body length. Megalodon was represented by a Belgian vertebral specimen. The largest vertebra in that specimen measured 15.5 centimeters (6 inches) in diameter, although there are other megalodon vertebrae in Denmark, for example, with diameters as much as 23 centimeters (9 inches).
Based on their analysis, Shimada et al, concluded that, because the trunk section of the Belgian specimen measured 11 meters, the head and tail were probably about 1.8 meters (6 feet) and 3.6 meters (12 feet) long, respectively, with a total body length of 16.4 meters (54 feet) for this particularly specimen. That means the Danish megalodon specimens could have been as long as 24.3 meters (80 feet). As for body shape, taking the new length estimates into account, the lemon shark appears to be closest modern analogue. “However, the exact position and shape of practically all the fins remain uncertain,” Shimada cautioned. “We are only talking about the main part of the body.”
Credit: DePaul University/Kenshu Shimada
The team also found that a 24.3-meter-long megalodon would have weighed a good 94 tons with an estimated swimming speed of 2.1-3.5 KPM (1.3-2.2 MPH). They also studied growth patterns evident in the Belgian vertebrae, concluding that the megalodon would give live birth and that the newborns would be between 3.6 to 3.9 meters (12-13 feet) long—i.e., roughly the size of a great white shark. The authors see this as a refutation of the hypothesis that megalodons relied on nursery areas to rear their young, since a baby megalodon would be quite capable of hunting and killing marine mammals based on size alone.
In addition, “We unexpectedly unlocked the mystery of why certain aquatic vertebrates can attain gigantic sizes while others cannot,” Shimada said. “Living gigantic sharks, such as the whale shark and basking shark, as well as many other gigantic aquatic vertebrates like whales have slender bodies because large stocky bodies are hydrodynamically inefficient for swimming.”
That’s in sharp contrast to the great white shark, whose stocky body becomes even stockier as it grows. “It can be ‘large’ but cannot [get] past 7 meters (23 feet) to be ‘gigantic’ because of hydrodynamic constraints,” said Shimada. “We also demonstrate that the modern great white shark with a stocky body hypothetically blown up to the size of megalodon would not allow it to be an efficient swimmer due to the hydrodynamic constraints, further supporting the idea that it is more likely than not that megalodon must have had a much slenderer body than the modern great white shark.”
Shimada emphasized that their interpretations remain tentative but they are based on hard data and make for useful reference points for future research.
An “exciting working hypothesis”
For his part, Cooper found a lot to like in Shimada et al.’s latest analysis. “I’d say everything presented here is interesting and presents an exciting working hypothesis but that these should also be taken with a grain of salt until they can either be empirically tested, or a complete skeleton of megalodon is found to confirm one way or the other,” Cooper told Ars. “Generally, I appreciate the paper’s approach to its body size calculation in that it uses a lot of different shark species and doesn’t make any assumptions as to which species are the best analogues to megalodon.”
Shark biologists now say a lemon shark, like this one, is a better model of the extinct megalodon’s body than the great white shark. Credit: Albert Kok
Cooper acknowledged that it makes sense that a megalodon would be slightly slower than a great white given its sheer size, “though it does indicate we’ve got a shark capable of surprisingly fast speeds for its size,” he said. As for Shimada’s new growth model, he pronounced it “really solid” and concurred with the findings on birthing with one caveat. “I think the refutation of nursery sites is a bit of a leap, though I understand the temptation given the remarkably large size of the baby sharks,” he said. “We have geological evidence of multiple nurseries—not just small teeth, but also geological evidence of the right environmental conditions.”
He particularly liked Shinada et al.’s final paragraph. “[They] call out ‘popular questions’ along the lines of, ‘Was megalodon stronger than Livyatan?'” said Cooper. “I agree with the authors that these sorts of questions—ones we all often get asked by ‘fans’ on social media—are really not productive, as these unscientific questions disregard the rather amazing biology we’ve learned about this iconic, real species that existed, and reduce it to what I can only describe as a video game character.”
Regardless of how this friendly ongoing debate plays out, our collective fascination with megalodon is likely to persist. “It’s the imagining of such a magnificently enormous shark swimming around our oceans munching on whales, and considering that geologically speaking this happened in the very recent past,” said Cooper of the creature’s appeal. “It really captures what evolution can achieve, and even the huge size of their teeth alone really put it into perspective.”
Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban.
Lizards are ancient creatures. They were around before the dinosaurs and persisted long after dinosaurs went extinct. We’ve now found they are 35 million years older than we thought they were.
Cryptovaranoides microlanius was a tiny lizard that skittered around what is now southern England during the late Triassic, around 205 million years ago. It likely snapped up insects in its razor teeth (its name means “hidden lizard, small butcher”). But it wasn’t always considered a lizard. Previously, a group of researchers who studied the first fossil of the creature, or holotype, concluded that it was an archosaur, part of a group that includes the extinct dinosaurs and pterosaurs along with extant crocodilians and birds.
Now, another research team from the University of Bristol has analyzed that fossil and determined that Cryptovaranoides is not an archosaur but a lepidosaur, part of a larger order of reptiles that includes squamates, the reptile group that encompasses modern snakes and lizards. It is now also the oldest known squamate.
The misunderstandings about this species all come down to features in its bones that are squamate apomorphies. These are traits unique to squamates that were not present in their ancestral form, but evolved later. Certain forelimb bones, skull bones, jawbones, and even teeth of Cryptovaranoides share characteristics with those from both modern and extinct lizards.
Wait, what is that thing?
So what does the new team argue that the previous team that studied Cryptovaranoides gets wrong? The new paper argues that the interpretation of a few bones in particular stand out, especially the humerus and radius.
In the humerus of this lizard, structures called the ectepicondylar and entepicondylar foramina, along with the radial condyle, were either not considered or may have been misinterpreted. The entepicondylar foramen is an opening in the far end of the humerus, which is an upper arm bone in humans and upper forelimb bone in lizards. The ectepicondylar foramen is a structure on the outer side of the humerus where the extensor muscles attach, helping a lizard bend and straighten its legs. Both features are “often regarded as key lepidosaur and squamate characteristics,” the Bristol research team said in a study recently published in Royal Society Open Science.
Paleontologists have long puzzled over how the dinosaurs—originally relatively small and of minor importance to the broader ecosystem—evolved to become the dominant species some 30 million years later. Fossilized feces and vomit from dinosaurs might hold important clues to how and why this evolutionary milestone came about, according to a new paper published in the journal Nature.
Co-author Martin Qvarnström, an evolutionary biologist with Uppsala University in Sweden, and his collaborators studied trace fossils known as bromalites, a designation that includes coprolites as well as vomit or other fossilized matter from an organism’s digestive tract. As previously reported, coprolites aren’t quite the same as paleofeces, which retain a lot of organic components that can be reconstituted and analyzed for chemical properties. Coprolites are fossils, so most organic components have been replaced by mineral deposits like silicate and calcium carbonates.
For archaeologists keen on learning more about the health and diet of past populations—as well as how certain parasites evolved in the evolutionary history of the microbiome—coprolites and paleofeces can be a veritable goldmine of information. For instance, in 2021 we reported on an analysis of preserved paleo-poop revealing that ancient Iron Age miners in what is now Austria were fond of beer and blue cheese.
If a coprolite contains bone fragments, chances are the animal who excreted it was a carnivore, and tooth marks on those fragments can tell us something about how the animal may have eaten its prey. The size and shape of coprolites can also yield useful insights. If a coprolite is spiral-shaped, for instance, it might have been excreted by an ancient shark, since some modern fish (like sharks) have spiral-shaped intestines.
A tale of two models
Excavations in the Late Triassic locality at Lisowice, Poland. The site yielded a large number of coprolites of predators and herbivores. Credit: Krystian Balanda
Qvarnström et al. were keen to test two competing hypotheses about the dinosaurs’ rise to dominance from the Late Triassic Period (237 million to 201 million years ago) to the onset of the Jurassic Period between 201 million to 145 million years ago. “No single hypothesis seems capable of explaining the rise of dinosaurs fully and critical questions about how dinosaurs established their dynasty on land remain largely unanswered,” the authors wrote about their research objectives.
One hypothesis cites evolutionary competition—the traditional “competitive replacement” model—as a driving factor, in which dinosaurs were better equipped to survive thanks to superior physiologies, anatomical adaptations, and feeding habits. Alternatively the “opportunistic replacement” model suggests that the dinosaurs were better able to adapt to a rapidly changing environment brought about by random processes—volcanic eruptions, climate change, or other catastrophic events that led to the decline and/or extinction of other species.
The duck-billed dinosaur Parasaurolophus is distinctive for its prominent crest, which some scientists have suggested served as a kind of resonating chamber to produce low-frequency sounds. Nobody really knows what Parasaurolophus sounded like, however. Hongjun Lin of New York University is trying to change that by constructing his own model of the dinosaur’s crest and its acoustical characteristics. Lin has not yet reproduced the call of Parasaurolophus, but he talked about his progress thus far at a virtual meeting of the Acoustical Society of America.
Lin was inspired in part by the dinosaur sounds featured in the Jurassic Park film franchise, which were a combination of sounds from other animals like baby whales and crocodiles. “I’ve been fascinated by giant animals ever since I was a kid. I’d spend hours reading books, watching movies, and imagining what it would be like if dinosaurs were still around today,” he said during a press briefing. “It wasn’t until college that I realized the sounds we hear in movies and shows—while mesmerizing—are completely fabricated using sounds from modern animals. That’s when I decided to dive deeper and explore what dinosaurs might have actually sounded like.”
A skull and partial skeleton of Parasaurolophus were first discovered in 1920 along the Red Deer River in Alberta, Canada, and another partial skull was discovered the following year in New Mexico. There are now three known species of Parasaurolophus; the name means “near crested lizard.” While no complete skeleton has yet been found, paleontologists have concluded that the adult dinosaur likely stood about 16 feet tall and weighed between 6,000 to 8,000 pounds. Parasaurolophus was an herbivore that could walk on all four legs while foraging for food but may have run on two legs.
It’s that distinctive crest that has most fascinated scientists over the last century, particularly its purpose. Past hypotheses have included its use as a snorkel or as a breathing tube while foraging for food; as an air trap to keep water out of the lungs; or as an air reservoir so the dinosaur could remain underwater for longer periods. Other scientists suggested the crest was designed to help move and support the head or perhaps used as a weapon while combating other Parasaurolophus. All of these, plus a few others, have largely been discredited.
Enlarge/ Half of the upper arm bone of this species can fit comfortably in the palm of a modern human hand.
Yousuke Kaifu
The discovery of Homo floresiensis, often termed a hobbit, confused a lot of people. Not only was it tiny in stature, but it shared some features with both Homo erectus and earlier Australopithecus species and lived well after the origin of modern humans. So, its precise position within the hominin family tree has been the subject of ongoing debate—one that hasn’t been clarified by the discovery of the similarly diminutive Homo luzonensis in the Philippines.
Today, researchers are releasing a paper that describes bones from a diminutive hominin that occupied the island of Flores much earlier than the hobbits. And they argue that, while it still shares an odd mix of features, it is most closely related to Homo erectus, the first hominin species to spread across the globe.
Remarkably small
The bones come from a site on Flores called Mata Menge, where the bones were found in a large layer of sediment. Slight wear suggests that many of them were probably brought to the site by a gentle flood. Dating from layers above and below where the fossils were found limits their age to somewhere between 650,000 and 775,000 years ago. Most of the remains are teeth and fragments of jaw bone, which can be suggestive of body size, but not definitive. But the new finds include a fragment of the upper arm bone, the humerus, which is more directly proportional to body size.
The researchers argue that the bone is broken at roughly the mid-point of the humerus, meaning that the full-sized bone was twice its length. Based on the relationship between humerus length and body size, they estimate that the individual it came from was only a bit above a meter tall.
They also took a slice from the center of the sample and imaged the cells present in the bone when it fossilized. These suggest that the fossil came from a fully mature adult. That makes its dimensions, including the diameter of the bone, the smallest yet found. It is, to quote the paper, “smaller than LB1 (H. floresiensis) and any other adult individuals of small-bodied fossil hominins (Australopithecus and H. naledi.” So, even by the standards of small species, the new fossils belong to an extremely small individual.
As for what these individuals are related to, the answers are (once again) complicated. The morphology of the humerus is most closely related to the H. floresiensis individuals who resided on Flores hundreds of thousands of years later. Beyond that, it’s most similar to H. naledi. From there, its shape appears to be equally distant from various species, including both H. erectus and various species of Australopithecus. The teeth show a variety of affinities but are generally closest to members of the Homo genus.
So, the authors make two arguments. One is that the fossils come from the ancestors of the hobbits and belong to the same species, indicating that they inhabited Flores for at least half a million years. The second is that it’s a branch off the population of H. erectus, a species that was similar in stature to modern humans. The population would have evolved a shorter stature once isolated on Flores.
Nothing makes a lot of sense
That’s the argument, at least. There will undoubtedly be different opinions among paleontologists, however. Some had already argued that H. floresiensis was an offshoot of H. erectus and will be happy to accept this as new evidence. But the species is such a hodge-podge of features of earlier and contemporary species that it has been easy for others to make contrary arguments.
Even if those arguments were settled, there’s the issue of how it got there. Even at times of significantly lower sea levels, Flores would have required a significant ocean crossing from what is now Java, where H. erectus is known to have been present, and which was connected to Asia at the time. There’s no indication that any species that came before modern humans had developed boating technology, and some have suggested that the population was established on Flores after being swept there on tsunami debris. Once present, the island environment could have selected for a smaller body size.
But then there’s the issue of Homo luzonensis, which shared a similar body size but inhabited a very different island. That would seem to require a second event that was also unlikely: either a second ocean passage involving individuals from Flores or another ocean trip by H. erectus followed by similar evolution of smaller body size, despite a potentially different environment.
It’s clear that, while the new finds tell us something about the Flores population, they’re not going to settle any arguments.
In the early 2000s, local fossil collector Mohamed ‘Ou Said’ Ben Moula discovered numerous fossils at Fezouata Shale, a site in Morocco known for its well-preserved fossils from the Early Ordovician period, roughly 480 million years ago. Recently, a team of researchers at the University of Lausanne (UNIL) studied 100 of these fossils and identified one of them as the earliest ancestor of modern-day chelicerates, a group that includes spiders, scorpions, and horseshoe crabs.
The fossil preserves the species Setapedites abundantis, a tiny animal that crawled and swam near the bottom of a 100–200-meter-deep ocean near the South Pole 478 million years ago. It was 5 to 10 millimeters long and fed on organic matter in the seafloor sediments. “Fossils of what is now known as S. abundantis have been found early on—one specimen mentioned in the 2010 paper that recognized the importance of this biota. However, this creature wasn’t studied in detail before simply because scientists focused on other taxa first,” Pierre Gueriau, one of the researchers and a junior lecturer at UNIL, told Ars Technica.
The study from Gueriau and his team is the first to describe S. abundantis and its connection to modern-day chelicerates (also called euchelicerates). It holds great significance, because “the origin of chelicerates has been one of the most tangled knots in the arthropod tree of life, as there has been a lack of fossils between 503 to 430 million years ago,” Gueriau added.
An ancestor of spiders
The study authors used X-ray scanners to reconstruct the anatomy of 100 fossils from the Fezouata Shale in 3D. When they compared the anatomical features of these ancient animals with those of chelicerates, they noticed several similarities between S. abundantis and various ancient and modern-day arthropods, including horseshoe crabs, scorpions, and spiders.
For instance, the nature and arrangement of the head appendages or ‘legs’ in S. abundantis were homologous with those of present-day horseshoe crabs and Cambrian arthropods that existed between 540 to 480 million years ago. Moreover, like spiders and scorpions, the organism exhibited body tagmosis, where the body is organized into different functional sections.
“Setapedites abundantis contributes to our understandings of the origin and early evolution of two key euchelicerate characters: the transition from biramous to uniramous prosomal appendages, and body tagmosis,” the study authors note.
Currently, two Cambrian-era arthropods, Mollisonia plenovenatrix and Habelia optata are generally considered the earliest ancestors of chelicerates (not all scientists accept this idea). Both lived around 500 million years ago. When we asked how these two differ from S. abundantis, Gueriau replied, “Habelia and Mollisonia represent at best early-branching lineages in the phylogenetic tree. While S. abundantis is found to represent, together with a couple of other fossils, the earliest branching lineage within chelicerates.”
This means Habelia and Mollisonia are relatives of the ancestors of modern-day chelicerates. On the other side, S. abundantis represents the first group that split after the chelicerate clade was established, making it the earliest member of the lineage. “These findings bring us closer to untangling the origin story of arthropods, as they allow us to fill the anatomical gap between Cambrian arthropods and early-branching chelicerates,” Gueriau told Ars Technica.
S. abundantis connects other fossils
The researchers faced many challenges during their study. For instance, the small size of the fossils made observations and interpretation complicated. They overcame this limitation by examining a large number of specimens—fortunately, S. abundantis fossils were abundant in the samples they studied. However, these fossils have yet to reveal all their secrets.
“Some of S. abundantis’ anatomical features allow for a deeper understanding of the early evolution of the chelicerate group and may even link other fossil forms, whose relationships are still highly debated, to this group,” Gueriau said. For instance, the study authors noticed a ventral protrusion at the rear of the organism. Such a feature is observed for the first time in chelicerates but is known in other primitive arthropods.
“This trait could thus bring together many other fossils with chelicerates and further resolve the early branches of the arthropod tree. So the next step for this research is to investigate deeper this feature on a wide range of fossils and its phylogenetic implications,” Gueriau added.
Rupendra Brahambhatt is an experienced journalist and filmmaker. He covers science and culture news, and for the last five years, he has been actively working with some of the most innovative news agencies, magazines, and media brands operating in different parts of the globe.
Gaiasia jennyae, a newly discovered freshwater apex predator with a body length reaching 4.5 meters, lurked in the swamps and lakes around 280 million years ago. Its wide, flattened head had powerful jaws full of huge fangs, ready to capture any prey unlucky enough to swim past.
The problem is, to the best of our knowledge, it shouldn’t have been that large, should have been extinct tens of millions of years before the time it apparently lived, and shouldn’t have been found in northern Namibia. “Gaiasia is the first really good look we have at an entirely different ecosystem we didn’t expect to find,” says Jason Pardo, a postdoctoral fellow at Field Museum of Natural History in Chicago. Pardo is co-author of a study on the Gaiasia jennyae discovery recently published in Nature.
Common ancestry
“Tetrapods were the animals that crawled out of the water around 380 million years ago, maybe a little earlier,” Pardo explains. These ancient creatures, also known as stem tetrapods, were the common ancestors of modern reptiles, amphibians, mammals, and birds. “Those animals lived up to what we call the end of Carboniferous, about 370–300 million years ago. Few made it through, and they lasted longer, but they mostly went extinct around 370 million ago,” he adds.
This is why the discovery of Gaiasia jennyae in the 280 million-year-old rocks of Namibia was so surprising. Not only wasn’t it extinct when the rocks it was found in were laid down, but it was dominating its ecosystem as an apex predator. By today’s standards, it was like stumbling upon a secluded island hosting animals that should have been dead for 70 million years, like a living, breathing T-rex.
“The skull of gaiasia we have found is about 67 centimeters long. We also have a front end of her upper body. We know she was at minimum 2.5 meters long, probably 3.5, 4.5 meters—big head and a long, salamander-like body,” says Pardo. He told Ars that gaiasia was a suction feeder: she opened her jaws under water, which created a vacuum that sucked her prey right in. But the large, interlocked fangs reveal that a powerful bite was also one of her weapons, probably used to hunt bigger animals. “We suspect gaiasia fed on bony fish, freshwater sharks, and maybe even other, smaller gaiasia,” says Pardo, suggesting it was a rather slow, ambush-based predator.
But considering where it was found, the fact that it had enough prey to ambush is perhaps even more of a shocker than the animal itself.
Location, location, location
“Continents were organized differently 270–280 million years ago,” says Pardo. Back then, one megacontinent called Pangea had already broken into two supercontinents. The northern supercontinent called Laurasia included parts of modern North America, Russia, and China. The southern supercontinent, the home of gaiasia, was called Gondwana, which consisted of today’s India, Africa, South America, Australia, and Antarctica. And Gondwana back then was pretty cold.
“Some researchers hypothesize that the entire continent was covered in glacial ice, much like we saw in North America and Europe during the ice ages 10,000 years ago,” says Pardo. “Others claim that it was more patchy—there were those patches where ice was not present,” he adds. Still, 280 million years ago, northern Namibia was around 60 degrees southern latitude—roughly where the northernmost reaches of Antarctica are today.
“Historically, we thought tetrapods [of that time] were living much like modern crocodiles. They were cold-blooded, and if you are cold-blooded the only way to get large and maintain activity would be to be in a very hot environment. We believed such animals couldn’t live in colder environments. Gaiasia shows that it is absolutely not the case,” Pardo claims. And this turned upside-down lots of what we knew about life on Earth back in gaiasia’s time.
Enlarge/ Painting of a gryphon, or griffin, a lion-raptor chimera from ancient folklore.
Mark Witton
The gryphon, or griffin, is a legendary creature dating back to classical antiquity, sporting the body, legs, and tail of a lion and the wings, head, and front talons of an eagle. Since the 1980s, a popular “geomyth” has spread that the griffin’s unique appearance was inspired by the fossilized skeleton of a horned dinosaur known as Protoceratops. It’s a fascinating and colorful story, but according to the authors of a new paper published in the journal Interdisciplinary Science Reviews, there is no hard evidence to support such a connection.
“Everything about griffin origins is consistent with their traditional interpretation as imaginary beasts, just as their appearance is entirely explained by them being [mythological] chimeras of big cats and raptorial birds,” said co-author Mark Witton, a paleontologist at the University of Portsmouth. “Invoking a role for dinosaurs in griffin lore, especially species from distant lands like Protoceratops, not only introduces unnecessary complexity and inconsistencies to their origins, but also relies on interpretations and proposals that don’t withstand scrutiny.”
There are representations of griffin-like creatures in ancient Egyptian art dated to before 3000 BCE, while in ancient Greek and Roman texts the creatures were associated with gold deposits in Central Asia. By the Middle Ages, griffins were common figures in medieval iconography and in heraldry. The hippogriff named Buckbeak in Harry Potter and the Prisoner of Azkaban is a related mythical creature, the product of a griffin and a mare.
It was the legendary link to Central Asian gold deposits that intrigued classical folklorist Adrienne Mayor in the 1980s. Drawing on Greek and Latin texts and related artworks, she suggested (beginning with a 1989 paper in Cryptozoology) that nomadic prospectors stumbled across fossilized skeletons of Protoceratops and brought tales of strange beaked quadrupeds to other regions as they traveled southeast along ancient trade routes. The dinosaur’s bony neck frill might have been interpreted in early illustrations as mammal-like external ears, with its beak indicating a creature that was part-bird, leading to the eventual addition of wings.
Enlarge/ This 9th century BCE relief depicts a griffin-like monster being pursued by a deity.
L. Gruner/Layard (1853)
Over the last 30 years, Mayor’s hypothesis has gained traction in the popular media and within certain academic circles; it’s now one of the most famous and widely touted examples of geomythology. It’s not an entirely crazy idea, even if its origins lie in the pseudoscientific field of cryptozoology. After all, people as far back as Paleolithic times certainly used fossils as decorative ornaments or talismans, and there are bona fide cases of such “geomyths”: For example, British ammonites were modified into “snake stones”; shark teeth were interpreted as snake tongues; and “winged” brachiopods became “stone swallows” in historic China.
The case for skepticism
But Witton and fellow Portsmouth paleontologist Richard Hing were skeptical because of the lack of any material evidence to support the connection between the griffin and Protoceratops. And they weren’t alone. Paleontologist Paul Sereno once dismissed Mayor’s claims as “sophomoric” and questioned her understanding of how fossils are found, identified, and interpreted, per the authors. So they set out to conduct the first detailed assessment of Mayor’s claims, re-examining historical fossil records—including the distribution of sites where Protoceratops fossils have been found—and classical sources, as well as consulting with historians and archaeologists about the supposed link.
“It is important to distinguish between fossil folklore with a factual basis—that is, connections between fossils and myth evidenced by archaeological discoveries or compelling references in literature and artwork—and speculated connections based on intuition,” said Hing. “There is nothing inherently wrong with the idea that ancient peoples found dinosaur bones and incorporated them into their mythology, but we need to root such proposals in realities of history, geography, and palaeontology. Otherwise, they are just speculation.”
Enlarge/ The echidna, an egg-laying mammal, doesn’t develop teeth.
Outliers among mammals, monotremes lay eggs instead of giving birth to live young. Only two types of monotremes, the platypus and echidna, still exist, but more monotreme species were around about 100 million years ago. Some of them might possibly be even weirder than their descendants.
Monotreme fossils found in refuse from the opal mines of Lightning Ridge, Australia, have now revealed the opalized jawbones of three previously unknown species that lived during the Cenomanian age of the early Cretaceous. Unlike modern monotremes, these species had teeth. They also include a creature that appears to have been a mashup of a platypus and echidna—an “echidnapus.”
Fossil fragments of three known species from the same era were also found, meaning that at least six monotreme species coexisted in what is now Lightning Ridge. According to the researchers who unearthed these new species, the creatures may have once been as common in Australia as marsupials are today.
“[This is] the most diverse monotreme assemblage on record,” they said in a study recently published in Alcheringa: An Australasian Journal of Paleontology.
The Echidnapus emerges
Named Opalios spendens, the “echidnapus” shows similarities to both ornithorhynchoids (the platypus and similar species) and tachyglossids (echidna and similar species). It is thought to have evolved before the common ancestor of either extant monotreme.
The O. splendens holotype had been fossilized in opal like the other Lightning Ridge specimens, but unlike some, it is preserved so well that the internal structure of its bones is visible. Every mammalian fossil from Lightning Ridge has been identified as a monotreme based partly on their peculiarly large dental canals. While the fossil evidence suggests the jaw and snout of O. splendens are narrow and curved, similar to those of an echidna, it simultaneously displays platypus features.
So what relates the echidnapus to a platypus? Despite its jaw being echidna-like at first glance, its dentary, or the part of the jaw that bears the teeth, is similar in size to that of the platypus ancestor Ornithorhynchus anatinus. Other features related more closely to the platypus than the echidna have to do with its ramus, or the part of the jaw that attaches to the skull. It has a short ascending ramus (the rear end) and twisted horizontal ramus (the front end) that are seen in other ornithorhynchoids.
Another platypus-like feature of O. splendens is the flatness of the front of its lower jaw, which is consistent with the flatness of the platypus snout. The size of its jaw also suggests a body size closer to that of a platypus. Though the echidnapus had characteristics of both surviving monotremes, neither of those have the teeth found on this fossil.
My, what teeth you don’t have
Cretaceous monotremes might not have had as many teeth as the echidnapus, but they all had some teeth. The other two new monotreme species that lived among the Lightning Ridge fauna were Dharragarra aurora and Parvopalus clytiei, and the jaw structure of each of these species is either closer to the platypus or the echidna. D. aurora has the slightly twisted jaw and enlarged canal in its mandible that are characteristic of an ornithorhynchoid. It might even be on the branch that gave rise the platypus.
P. clytiei is the second smallest known monotreme (after another extinct species named Teinolophos trusleri). It was more of an echidna type, with a snout that was curved and deep like that of a tachyglossid rather than flat like that of an ornithorhynchoid. It also had teeth, though fewer than the echidnapus. Why did those teeth end up disappearing altogether in modern monotremes?
Monotremes without teeth came onto the scene when the platypus (Ornithorhynchus anatinus) appeared during the Pleistocene, which began 2.6 million years ago. The researchers think competition for food caused the disappearance of teeth in the platypus—the spread of the Australo-New Guinean water rat may have affected which prey platypuses hunted for. Water rats eat mostly fish and shellfish along with some insects, which are also thought to have been part of the diet of ancient ornithorhynchoids. Turning to softer food to avoid competition may explain why the platypus evolved to be toothless.
As for echidnas, tachyglossids are thought to have lost their teeth after they diverged from ornithorhynchoids near the end of the Cretaceous. Echidnas are insectivores, grinding the hard shells of beetles and ants with spines inside their mouths, so have no need for teeth.
Although there is some idea of what happened to their teeth, the fate of the diverse species of Cretaceous monotremes, which were not only toothy but mostly larger than the modern platypus and echidna, remains unknown. The end of the Cretaceous brought a mass extinction triggered by the Chicxulub asteroid. Clearly, some monotremes survived it, but no monotreme fossils from the time have surfaced yet.
“It is unclear whether diverse monotreme fauna survived the end-Cretaceous mass extinction event, and subsequently persisted,” the researchers said in the same study. “Filling this mysterious interval of monotreme diversity and adaptive development should be a primary focus for research in the future.”
Enlarge/ Later theropods had multiple adaptations to varied temperatures.
Dinosaurs were once assumed to have been ectothermic, or cold-blooded, an idea that makes sense given that they were reptiles. While scientists had previously discovered evidence of dinosaur species that were warm-blooded, though what could have triggered this adaptation remained unknown. A team of researchers now think that dinosaurs that already had some cold tolerance evolved endothermy, or warm-bloodedness, to adapt when they migrated to regions with cooler temperatures. They also think they’ve found a possible reason for the trek.
Using the Mesozoic fossil record, evolutionary trees, climate models, and geography, plus factoring in a drastic climate change event that caused global warming, the team found that theropods (predators and bird ancestors such as velociraptor and T. rex) and ornithischians (such as triceratops and stegosaurus) must have made their way to colder regions during the Early Jurassic. Lower temperatures are thought to have selected for species that were partly adapted to endothermy.
“The early invasion of cool niches… [suggests] an early attainment of homeothermic (possibly endothermic) physiology in [certain species], enabling them to colonize and persist in even extreme latitudes since the Early Jurassic,” the researchers said in a study recently published in Current Biology.
Hot real estate
During the Mesozoic Era, which lasted from 230 to 66 million years ago, proto-dinosaurs known as dinosauromorphs began to diversify in hot and dry climates. Early sauropods, ornithischians, and theropods all tended to stay in these regions.
Sauropods (such as brontosaurus and diplodocus) would become the only dinosaur groups to bask in the heat—the fossil record shows that sauropods tended to stay in warmer areas, even if there was less food. This suggests the need for sunlight and heat associated with ectothermy. They might have been capable of surviving in colder temperatures but not adapted enough to make it for long, according to one hypothesis.
It’s also possible that living in cooler areas meant too much competition with other types of dinosaurs, as the theropods and ornithiscians did end up moving into these cooler areas.
Almost apocalypse
Beyond the ecological opportunities that may have drawn dinosaurs to the cooler territories, it’s possible they were driven away from the warm ones. Around 183 million years ago, there was a perturbation in the carbon cycle, along with extreme volcanism that belched out massive amounts of methane, sulfur dioxide, and mercury. Life on Earth suffered through scorching heat, acid rain, and wildfires. Known as the Early Jurassic Jenkyns Event, the researchers now think that these disruptions pushed theropod and ornithischian dinosaurs to cooler climates because temperatures in warmer zones went above the optimal temperatures for their survival.
The theropods and ornithischians that escaped the effects of the Jenkyns event may have had a key adaptation to cooler climes; many dinosaurs from these groups are now thought to have been feathered. Feathers can be used to both trap and release heat, which would have allowed feathered dinosaurs to regulate their body temperature in more diverse climates. Modern birds use their feathers the same way.
Dinosaur species with feathers or special structures that improved heat management could have been homeothermic, which means they would have been able to maintain their body temperature with metabolic activity or even endothermic.
Beyond the dinosaurs that migrated to high latitudes and adapted to a drop in temperature, endothermy might have led to the rise of new species and lineages of dinosaurs. It could have contributed to the rise of Avialae, the clade that includes birds—the only actual dinosaurs still around—and traces all the way back to their earliest ancestors.
“[Our findings] provide novel insights into the origin of avian endothermy, suggesting that this evolutionary trajectory within theropods… likely started in the latest Early Jurassic,” the researchers said in the same study.
That really is something to think about next time a sparrow flies by.
Enlarge/ Discovered in 1931, Tridentinosaurus antiquus has now been found to be, in part, a forgery.
Valentina Rossi
For more than 90 years, scientists have puzzled over an unusual 280 million-year-old reptilian fossil discovered in the Italian Alps. It’s unusual because the skeleton is surrounded by a dark outline, long believed to be rarely preserved soft tissue. Alas, a fresh analysis employing a suite of cutting-edge techniques concluded that the dark outline is actually just bone-black paint. The fossil is a fake, according to a new paper published in the journal Paleontology.
An Italian engineer and museum employee named Gualtiero Adami found the fossil near the village of Piné. The fossil was a small lizard-like creature with a long neck and five-digit limbs. He turned it over to the local museum, and later that year, geologist Giorgio del Piaz announced the discovery of a new genus, dubbed Tridentinosaurus antiquus. The dark-colored body outline was presumed to be the remains of carbonized skin or flesh; fossilized plant material with carbonized leaf and shoot fragments were found in the same geographical area.
The specimen wasn’t officially described scientifically until 1959 when Piero Leonardi declared it to be part of the Protorosauria group. He thought it was especially significant for understanding early reptile evolution because of the preservation of presumed soft tissue surrounding the skeletal remains. Some suggested that T. antiquus had been killed by a pyroclastic surge during a volcanic eruption, which would explain the carbonized skin since the intense heat would have burnt the outer layers almost instantly. It is also the oldest body fossil found in the Alps, at some 280 million years old.
Yet the fossil had never been carefully analyzed using modern analytical techniques, according to co-author Valentina Rossi of University College Cork in Ireland. “The fossil is unique, so this poses some challenges, in terms of analysis that we can do when effectively we cannot afford to make any mistakes, i.e., damaging the fossil,” Rossi told Ars. “Previous preliminary studies were carried out in the past but were not conclusive and the results not straightforward to interpret. The incredible technological advancement we are experiencing in paleontology made this study possible, since we can now analyze very small quantities of precious fossil material at the molecular level, without the risk of damaging the whole specimen.”
Enlarge/ The fossil under normal light (left) and under UV light (right).
Valentina Rossi
Rossi et al. focused on the dark body outline believed to be carbonized soft tissue for their analysis. This involved photographing the fossil—plus some fossilized plants found in the same area—in both white light and UV light, and using those images to build a photogrammetric map and 3D model. They also took minute samples and examined them with scanning electron microscopy, micro X-ray diffraction, Raman spectroscopy, and ATF-FTIR spectroscopy.
The entire specimen, both the body outline and the bones, fluoresced yellow under UV light; the plant specimens did not. But coatings like lacquers, varnishes, glues, and some artificial pigments do fluoresce yellow under UV light. There was no evidence of fossilized melanin, which one might expect to find in preserved soft tissue. Also, fossils with preserved soft tissue are typically flattened with little topography; the T. antiquus specimen showed a lot of topographical variation in the dark outline areas.
The authors thought this was consistent with some kind of mechanical preparation, perhaps to (unsuccessfully) expose more of the skeleton. They concluded that one or more layers of some kind of coating had been applied to the body outline and the bones. The granular texture of what had been presumed to be soft tissue was more consistent with manufactured pigments used in historical paintings—specifically, “a manufactured carbon-based pigment mixed with an organic binder,” i.e., bone black paint. Conclusion: T. antiquus is a forgery and scientists therefore should be wary of using the specimen in comparative phylogenetic analysis.
Enlarge/ Valentina Rossi with an image of Tridentinosaurus antiquus.
Zixiao Yang
How could scientists have presumed the dark outline of carbonized soft tissue for so many decades? “This fossil was discovered in 1931 and back then fossils were treated very differently than today,” said Rossi. “Application of paints, consolidates and lacquers on fossil bones was the norm, because that was the only way to protect the specimens for further deterioration. It was also sometimes to embellish specimens by making them sleek and shiny. Unfortunately, in the case of Tridentinosaurus, the mechanical preparation did most of the damage and then the application of a black paint created the illusion of a lizard-like animal impression on the surface of the rock.”
This analysis also casts doubt on the validity of the fossil’s assigned taxon, which was based on observations of the body proportion and measurements of limbs, neck, and abdomen. Part of the fossil, at least, appears to be genuine—the long bones of the hind limbs—but that doesn’t mean it will be easier now to determine species or where the specimen fits in the fossil record. “The bones that are recognizable appear to be very poorly preserved, so it might be very difficult to extrapolate any information,” said Rossi. “But perhaps the discovery of new fossil material from the same area where this specimen was found might help identify this ancient animal.”
So how can paleontologists prevent this kind of error from happening in the future? Rossi recommends reporting such finds via scientific journals with a detailed explanation of the methods that were used to characterize the surface materials on both the fossil and the rock. “It’s important to be aware that certain practices are not acceptable anymore, and not just because it creates—whether intentionally or by genuine mistake—misinformation and distorts our perception of a specimen,” said Rossi. “But also because the fossil will be irreparably damaged, and we might have lost key information about the original aspect and preservation state of the fossil.”
