Retro vs Modern #21: Deinonychus antirrhopus
Deinonychus antirrhopus was one of the most significant dinosaur discoveries of the 20th century, kicking off the Dinosaur Renaissance and the recognition of the evolutionary link between maniraptoran theropods and modern birds.
1960s
The first remains of this species were discovered in North America in the 1930s, but at the time the fossils weren’t officially described or named. It wasn’t until the 1960s that more specimens were found in Montana, representing at least three preserved individuals, and paleontologist John Ostrom recognized that there was something very special about this dinosaur.
In contrast to the prevailing view at the time that theropods were all upright tail-dragging “sluggish lizards” this was clearly a highly specialized and active predator, with a huge sickle-shaped claw on each foot and a long stiff tail for balance – inspiring its scientific name’s meaning of “counterbalancing terrible claw”.
And while the very first reconstruction of Deinonychus might seem retro to modern eyes, at the time it was revolutionary and it went on to become an iconic representation of the species for the next couple of decades. Drawn by Robert Bakker, who was Ostrom’s student at the time, it depicted a lizard-like creature with its body held in a horizontal pose and its tail held out straight behind it. Its head was portrayed as more domed than we now know Deinonychus’ skull to have been, and its neck was up in an alert posture while the animal ran at full sprint, with its sickle-claws held up away from the ground to keep them sharp.
A few years later further discoveries showed a highly bird-like pelvis and hands very similar to those of Archaeopteryx, triggering the Dinosaur Renaissance reinterpretation of dinosaurs as active warm-blooded animals, and the revival of the 19th century idea that they were the ancestors of birds.
1980s-1990s
As the “birds are dinosaurs” idea began to gain acceptance with increasing amounts of anatomical evidence, some paleontologists in the 1980s began to also suspect that highly bird-like dromaeosaurids like Deinonychus might have also been feathered. Some reconstructions during this time showed this to varying degrees, particularly those drawn by Bakker and by Gregory Paul – but it didn’t really catch on more widely at first, for one very big reason:
Jurassic Park happened.
Dromaeosaurs hadn’t been well-known dinosaurs to the general public before that point, but the 1993 JP “raptors” were an instant hit in pop culture. Physically based much more on Deinonychus than on Velociraptor, and exemplifying the renaissance view of dinosaurs in major media for the first time, the movie’s fully scaled and oversized version of these animals dominated popular depictions for years afterwards. Even the most rigorous and anatomically accurate artwork showcasing their bird-like features still usually kept them completely naked to retain that familiar reptilian appearance.
Most 1990s attempts at any feathering tended towards being as sparse as possible – often along with the shrinkwrapping typical for the era – at best being decent for the time but what we’d now deride as “half-assed”, and at worst being “a few token quills on the back of the head”.
Deinonychus fossils found in association with Tenontosaurus were also interpreted as being evidence of cooperative pack hunting behavior during this time, and it became a common paleoart meme to depict the large herbivore being constantly swarmed by ravenous raptors.
2020s
The mid-1990s discovery of fully-feathered dinosaurs like Sinosauropteryx in China, followed a few years later by raptors with wing-feathered arms like Sinornithosaurus, gradually began to put the fluff back onto dinosaurs like Deinonychus.
(…At least in reasonably scientific paleoart. The much much stronger and ongoing resistance from popular culture is far too big a subject to get into here. But maybe, just maybe, we’re finally hitting a turning point there?)
Early attempts at properly feathering dinosaurs were a bit awkward, usually looking rather like a bunch of scruffy greasy hair glued onto a scaly raptor, a dinosaur wearing fuzzy pajamas, or like the old “bird-lizard” depictions of Archaeopteryx. Even into the early 2010s some paleoart memes were still common in depictions of dromaeosaurs, but increasingly better understanding of their anatomy and plumage arrangements over the last decade or so has brought us to a much more birdlike interpretation of these animals – with paleoartists like Emily Willoughby being especially influential in popularizing the modern view of dinosaurs like Deinonychus.
We now know Deinonychus lived during the Early Cretaceous, about 115-108 million years ago, in what is now the Mountain West and South Central United States. Up to around 3.4m long (11’), it stood about 1m tall (3'3"), similar in size to a large dog.
It had blade-like teeth in its jaws, and forward-facing eyes with stereoscopic vision. Its three-fingered arms would have been covered by wing-like feathers, and its tail probably had feathers all the way along its length and was stiffened but not totally inflexible.
It may have used the sickle-claws on its feet to pin down struggling prey, eating it alive while flapping its wings and waving its tail for balance. And while often depicted as an extremely fast-runner, its leg proportions and foot anatomy suggest it was actually built more for walking and had an especially strong grip strength in its feet, trading speed for power and probably being more of an ambush predator – often being compared to a “giant ground-hawk”.
Pack hunting has been called into question recently, too, arguing that the Tenontosaurus sites may actually represent crocodile-like or Komodo dragon-like behavior with mobs of scavenging individuals congregating at a carcass. But other evidence from trackways and Utahraptor does offer potential support for pack behavior in raptors, so it’s still open to interpretation.
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Strutting through the week like the striped hyena (Hyaena hyaena)? This scavenger lives in parts of Africa, the Middle East, and India, inhabiting savannas, scrublands, and semi deserts. While it prefers to eat carrion, it also supplements its diet with fruits, seeds, and leaves.
Photo: Balaji Venkatesh Sivaramakrishnan, CC BY-NC-SA 2.0, flickr
#AnimalFacts #hyena #africa #NaturalHistory #nature #wildlife #dyk
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Retro vs Modern #23: Spinosaurus aegyptiacus
Spinosaurid teeth were first found in the 1820s in England, but were misidentified as belonging to crocodilians. It wasn’t until nearly a century later that Spinosaurus aegyptiacus was discovered and recognized as a dinosaur – and it would be another century after that before we really started to learn anything about it.
1910s
The first fossils of Spinosaurus were discovered in Egypt in the 1910s. With only a few fragments of its skeleton known it was an enigma right from the start, hinting at a large and very strange theropod dinosaur with crocodile-like teeth, an oddly-shaped lower jaw, and elongated neural spines on its vertebrae that seemed to be part of a huge sail.
A few possible extra fragments were found in the 1930s, but overall these few pieces were all that was known of Spinosaurus for a long time.
The fossils were kept in the Paleontological Museum in Munich, Germany,a building that was severely damaged during a bombing raid in World War II. Many important specimens were destroyed, including Spinosaurus, and only the published drawings and descriptions of the bones remained.
So for the next several decades Spinosaurus remained a very poorly-understood mystery. During this period it was generally depicted as a generic “carnosaur”, often modeled on something like Megalosaurus, in the standard-for-the-time tripod pose and with a Dimetrodon-like sail on its back.
Interestingly a 1930s skeletal reconstruction shows Spinosaurus with an unusually long torso and fairly short legs, details that are surprisingly modern despite the retro posture.
1990s
In the 1980s some partial snout bones from Niger were recognized as having similarities with the jaw of Spinosaurus. Around the same time the fairly complete skeleton of Baryonyx was discovered, and along with further spinosaurid discoveries in the mid-to-late 1990s a decent idea of what Spinosaurus might have looked like began to emerge.
It was reconstructed with a long kinked crocodilian-like snout, a ridged bony crest in front of its eyes, an S-curved neck, and large thumb claws on its hands – an interpretation that was heavily popularized by Jurassic Park III in the early 2000s, bringing this enigmatic dinosaur to public attention and portraying it as a fearsome super-predator bigger than Tyrannosaurus.
2020s
Despite attempts to locate more complete Spinosaurus remains, only fragments continued to be found, and it remained a frustratingly poorly-known species even into the early 2010s.
Finally, in 2014, almost a full century after it was first described and named, Spinosaurus started to reveal its secrets with the announcement of the discovery of the most complete skeleton so far, discovered in the Kem Kem fossil beds in Morocco. Its body was still only partially represented, but it included skull fragments, part of a hand, a complete leg and pelvis, some sail spines, and several vertebrae from the neck, back, and tail.
And nobody was expecting what these pieces revealed.
It had a very long torso and proportionally short stumpy legs, and was reconstructed with a huge distinctive “M-shaped” sail on its back. Its feet had flat-bottomed claws and its “dewclaw” toe was enlarged into an extra weight-bearing digit – adaptations for spreading its weight over soft muddy ground, and suggesting its feet may also have been webbed. Initially it was also presented as possibly being quadrupedal, due to how far forward its center of mass seemed to be, reviving an odd idea from the late 20th century.
Along with its long crocodile-like head and conical teeth, this was interpreted as evidence it was a semiaquatic fish-eating swimming animal – potentially making it the first known semiaquatic non-avian dinosaur. Spinosaurids had been suggested to be specialized piscivores before, especially since Baryonyx had been found with fish scales in its stomach, but they were generally assumed to be more like modern grizzly bears, wading into water to hunt but not being habitual swimmers. Spinosaurus’ weird croco-duck proportions, however, seemed like they might be much more suited to watery habitats than to the land.
Since Spinosaurus had become a popular dinosaur with the general public by that point, the discovery was big news – and a big controversy for a while. It was so bizarre that some paleontologists were skeptical of the radical new interpretation, wondering if the measurements of the skeleton were correct or if the short legs were even from the same individual or the same species as the rest of the bones.
After a while the new proportions were accepted as fairly accurate, and over the next few years attention turned to instead figuring out just how this animal worked and how aquatic it actually was. An earlier isotope analysis of its teeth supported a semiaquatic lifestyle similar to crocodiles and turtles, but a buoyancy study argued that it might not have been able to dive below the water suface and its sail made floating unstable – but also found that its center of mass was closer to its hips than previously calculated, suggesting it could walk bipedally after all.
Then in 2020 came another surprise: more of the tail of the new specimen had been found, and it was just as weird as the rest of Spinosaurus. Its tail was a huge vertically flattened paddle-like fin supported by long thin neural spines and chevrons, resembling a giant eel or newt more than a dinosaur and also giving some more weight to the idea that it was a swimmer.
Our modern view of Spinosaurus is still evolving, and likely to be full of even more surprises in the future as we discover more about this unique dinosaur. But we at least know it lived in what is now North Africa during the Late Cretaceous, about 99-93 million years ago, and whether it was a swimmer or wading generalist predator it was one of the largest known theropods to ever live, estimated to have reached around 16m long (~52ft).
While the “M-shaped” sail reconstruction has been popularized by the recent discoveries, the exact shape of this structure is still unknown. Like with other sailbacked animals it’s also not clear what it was for, with ideas including temperature regulation, visual display, supporting a fatty hump, and a potential hydrodynamic adaptation.
EDIT: And while I was working on this entry (late March 2022) I missed that another study had just come out with more anatomical support for swimming Spinosaurus!
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