I reblogged this last month, tagged it, and said “might as well see if it works.” I used this video as a reference to find all the forms that i needed (which is A LOT, especially if you’re a dependent) and sent them through the mail, not really allowing myself to hope.
dude.
$2,714 of medical debt from my top surgery - gone. im shaking this was such a weight on me for 2 years and it fucking worked. what the fuck.
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:
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.
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.
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.
Named just a year after Megalosaurus, in 1825, Iguanodon has remained a fairly iconic dinosaur ever since.
Discovered in a different region of Southeast England, its fossilized teeth were soon recognized as being similar to those of modern iguanas – but much much larger. Partial skeletal remains were initially reconstructed as belonging to a gigantic herbivorous lizard, with what was thought to be a horn placed on the tip of its nose.
1850s
The Victorian Crystal Palace statues of Iguanodon depicts a more bulky reptile with a nose horn, a toothless beak at at the front of its jaws, scaly skin, thick upright legs and hoof-like claws. Much like the Megalosaurus of the time it’s really not nearly so bad of a reconstruction as it’s often accused of being, showing a surprisingly naturalistic and almost mammal-like interpretation of these animals compared to later portrayals.
Technically the particular “Iguanodon” species at Crystal Palace has more recently been renamed Mantellisaurus atherfieldensis, but it was considered to be Iguanodon at the time so it’s included here anyway.
1880s-1960s
A massive discovery of the remains of nearly 40 Iguanodon individuals in a coal mine in Bernissart, Belgium, revealed the full anatomy of these dinosaurs for the first time. Much more well-preserved and complete than the patchy English material, these larger Iguanodon bernissartensis eventually became the official type species for the whole genus – a standard used to help determine whether similar-looking fossils are Iguanodon or not.
The Bernissart specimens were restored as bipedal animals in an upright kangaroo-like pose, with their tails dragging behind them acting like a tripod to prop them up. What had previously been the single “horn” was finally realized to instead be a thumb spike on each hand, interpreted as a defensive weapon against predators.
This image of Iguanodon persisted for decades, with a giraffe-like long prehensile tongue sometimes also depicted (including a particularly bizarre interpretation of it sticking out through a hole in the lower jaw!).
2020s
The Dinosaur Renaissance in the late 20th century corrected Iguanodon’s posture to hold its body horizontally, and it was eventually recognized as being capable of both bipedal and quadrupedal movement. Juveniles were found to have walked more on their hindlimbs, while adults spent more time on all fours but were still capable of running bipedally when they needed to.
We now have fossils of Iguanodon from across much of Europe during the Early Cretaceous, about 126-122 million years ago. Our modern view of this animal is a heavily built ornithopod that grew to around 9m long (~30’), with a horse-like head, a large keratinous beak at the front of its jaws, chewing teeth further back, and cheeks covering the sides of its mouth. Its chunky forelimbs each had a large thumb spike, hoof-like claws, and a prehensile grasping pinky finger, while its powerful hindlimbs ended in three-toed vaguely bird-like feet.
Soft tissue preservation discovered in related hadrosaurs suggests it probably also had a very bulky body with a thick heavily muscled neck and tail, and possibly an ornamental “frill” running along its back. Skin impressions show a covering of numerous tiny pebbly scales, generally too small to have been visible from a distance.
The first scientifically documented mosasaur fossils were skulls discovered in the Netherlands during the 1760s and 1770s, but these remains were initially interpreted as belonging to a fish, crocodile, or whale. In the late 1790s their resemblance to monitor lizards was noted, and the fossils were soon recognized as belonging to giant marine reptiles unlike any known living species – a revolutionary concept at the time, and influential in the early development of ideas about extinction.
In the 1820s Mosasaurus hoffmannii was the first species officially described. For several decades it was thought to be a giant amphibious lizard with either webbed feet or flipper-like legs, with one of the earliest popular reconstructions being the 1850s Crystal Palace statue.
By the 1870s more complete fossil discoveries in North America had revealed the paddle-like flippers and fully aquatic nature of mosasaurs. Skin impressions showed overlapping keeled diamond-shaped scales resembling those of rattlesnakes, but proportionally much smaller compared to their body size.
1890s
Then, in the late 1890s, one mosasaur specimen was interpreted as having a mane-like “fringe” of soft tissue along its back.
Only a few years later this was realized to be a mistake, actually being preserved tracheal cartilage, but it was too late. The idea had already caught on in artistic depictions and quickly became a paleoart meme, with mosasaurs frequently portrayed with elaborate frills for the majority of the next century.
2020s
Early arguments about whether mosasaurs’ closest relatives were monitor lizards or snakes had settled down by the 1920s, with the consensus at the time being monitor lizards, and the first half of the 20th century saw little mosasaur research beyond the naming of a few new species. Much like the ichthyosaurs and plesiosaurs it was only really in the wake of the Dinosaur Renaissance that interest in these marine reptiles and their paleobiology really began to pick up again.
The debate about their evolutionary relationships has been reignited, too, with some recent studies once again supporting a very close relationship to snakes – although there’s currently no clear consensus.
Our modern view of Mosasaurus hoffmannii is a large chunky mosasaur that grew to at least 11m long (~36’). It lived during the end of the Cretaceous period, about 70-66 million years ago, and inhabited a wide range of climates across much of the ancient Atlantic Ocean and various connected shallow seaways, with fossils known from Europe, Africa, and North and South America.
Its long jaws had a powerful bite force and it seems to have been a more visual hunter than some other mosasaurs, with relatively large eyes and a less well-developed sense of smell. It was one of the largest marine animals of its time and was probably a generalist apex predator, feeding on a wide variety of prey such as fish, ammonites, and other marine reptiles.
Hadrosaurs were first discovered during the 1850s in North America, with the eponymous Hadrosaurus being both one of the most complete dinosaurs known at the time and also the first dinosaur skeleton to ever be mounted and displayed.
Like many other dinosaurs of the time hadrosaurs were initially reconstructed as bipedal with an upright kangaroo-like pose. Early in the history of their study their wide flat “duckbill” snouts were thought to indicate they were semi-aquatic, and they were frequently portrayed swimming and wading while feeding on soft water plants.
While elaborately bony-crested hadrosaurs like Parasaurolophus have become some of the most famous and recognizable members of the group, the species that’s gone through the most radical changes in our understanding in recent years is probably Edmontosaurus annectens.
1890s-1960s
Edmontosaurus has had an especially messytaxonomic history with various specimens spending decades under many different names, commonly being labelled as Anatosaurus and Trachodon for much of the 20th century. For the sake of avoiding a lot of confusion I’m just going to keep referring to it here as “Edmontosaurus”, even though the naming issues weren’t properly sorted out until the 1990s.
The idea of amphibious hadrosaurs was finally challenged in the mid-1960s, at the start of the Dinosaur Renaissance, with details of their anatomy, possible stomach contents, and the environments that their fossils had been preserved in all being used to help reinterpret them as fully terrestrial herbivores that walked on four legs and ran on two. The discovery of Maiasaura nesting colonies in the late 1970s also revealed a lot of new information about the life history of these dinosaurs, and helped to popularize the image of them as social animals living in herds and caring for their young.
From the 1990s onwards new discoveries of additional “mummies” of both Edmontosaurus and other hadrosaurs have given us even more insights into the soft parts of their anatomy. Their necks and tails were much more thickly muscled and chunky than their skeletons alone suggest, the frill may have had a sort of rectangular segmented appearance, and the webbing on their forelimbs was actually more of a “mitten” that bound their hands into fleshy weight-bearing pads. And instead of a broad “duckbill” they actually had large hooked beaks covering their snouts, giving then more of a horse-like head shape.
We now know Edmontosaurus lived during the very end of the Cretaceous, about 73-66 million years ago, with the older part of that time range represented by Edmontosaurus regalis in Western Canada and the younger part represented by Edmontosaurus annectens in Western Canada and the Western and West North Central United States. It was one of the largest known hadrosaurs with most adult specimens around 9-12m long (~30-39’), but some of the very largest known partial remains suggest the existence of rare enormous “super-adults” that were about 15m long (49’).
Its skin had a complex texture of varying scale shapes and sizes across its body, and one mummified specimen of Edmontosaurus regalis shows a raised bumpy pattern of large scale clusters on its neck and a fleshy crest on the top of its head. It’s currently unclear if these were sexually dimorphic features and we don’t know if Edmontosaurus annectens actually had them too, but I’ve speculatively included them in this reconstruction anyway.
And despite being one of the most intensely-studied and completely known non-avian dinosaurs in the world, Edmontosaurus is somehow still continuing to surprise us. Parts of the mummy specimen nicknamed “Dakota” are still being carefully prepared, and in late 2019 the North Dakota Geological Survey teased an unexpected discovery – a large single hoof-like nail on the front of its hand, unlike anything ever seen before on a dinosaur, and suggesting that Edmontosaurus may have been much more specialized for purely quadrupedal movement than previously thought.
Official details on the “hoof” still haven’t been published yet, but whenever it happens it’ll be exciting to find out just what’s actually going on there.
Plesiosaurs were first recognized as a distinct group of fossil animals in the early 1820s, only a few years after ichthyosaurs. Initially they were perceived as being closer in form to reptiles in the “chain of being” than the more fish-like ichthyosaurs were, and so the group’s scientific name ended up reflecting that early interpretation – “plesiosaur” roughly translates to “near to reptiles”.
The first named species of plesiosaur was Plesiosaurus dolichodeirus, based on a near-complete skeleton discovered by Mary Anning that revealed the strange long-necked proportions of these animals for the first time.
1830s-1850s
Early reconstructions of plesiosaurs in the 1830s compared them to “a snake threaded through a turtle”, giving them highly sinuous necks and a turtle-like body. Much like ichthyosaurs they were assumed to be amphibious, using their flippers to crawl up onto the shore like a sea turtle.
The 1850s Crystal Palace plesiosaur statues show a variant of this design with smooth skin textures and fairly flexible reptilian bodies, with powerful shoulders and flipper postures that give them an overall almost seal-like appearance.
1860s-1990s
From the 1860s onwards a more upright S-shaped neck pose became the most common depiction of plesiosaurs. The writhing snake-like necks persisted in some reconstructions of the extremely long-necked elasmosaurids, but the overall design for these animals that caught hold for the next century was an egg-shaped body with oar-like flippers and a swan-like neck – a body plan that would end up so influential in pop culture that it was incorporated into modern lake monster folklore, with the Loch Ness Monster being the most famous example.
During this period plesiosaurs were often portrayed as floating or swimming at the water’s surface, rowing along with their flippers and using their long necks to snatch up prey. They were generally assumed to still haul out turtle-style to lay their eggs on the shore, although it wasn’t clear how the very largest species would have been able to support their own weight.
2020s
Since the 1990s a boom of new plesiosaur species and biomechanical studies have brought a lot of changes to our understanding of these marine reptiles.
Their necks are now considered to have been less flexible, capable only of more gentle curving, and were probably much thicker and more streamlined with the body than previously depicted. Rather than oar-like rowing all four of their flippers were probably used in more of an “underwater flying” vertical motion similar to modern sea turtles – which is pretty fitting, considering that their closest living relatives are now thought to actually be turtles.
We now know Plesiosaurus itself was a fairly small species, around 3.5m long (~11'6"), with a broad body and a short thick tail that probably had a rudder-like fin – usually assumed to be vertically-oriented, but possibly horizontal instead. It lived during the Early Jurassic, about 201-183 million years ago, in the shallow tropical sea that covered what is now southern England, and had a rather small head compared to other plesiosaurs, with its eyes facing upwards and to the sides.
Fossilized ichthyosaur bones have been found for centuries, but were initially misidentified as being the remains of fish, dolphins, and crocodiles. More complete skeletons began to be discovered in the early 19th century – particularly by pioneering paleontologist Mary Anning – and Ichthyosaurus communis was one of the first species of these ancient “fish lizards” to be scientifically recognized.
1830s-1870s
Early reconstructions of ichthyosaurs in the 1830s depicted flippered crocodile-like animals with long straight eel-like tails and strangely shrinkwrapped features, showing the sclerotic rings of their eyes and the internal bones of their flippers as highly visible externally. They were also frequently portrayed as being amphibious, hauling themselves out of the water to bask.
By the late 1830s impressions of smooth scaleless skin had been found, and specimens with tail-tips that were always “broken” in the exact same place were interpreted as evidence of the presence of some sort of paddle-like tail fin. The 1850s Crystal Palace Ichthyosaurus statues show this slightly updated version, along with a low dorsal ridge on their backs reminiscent of a beluga whale.
2020s
From the 1880s onwards the discovery of exceptional ichthyosaur specimens preserving whole body outlines revealed a fully aquatic streamlined shape, a triangular dorsal fin, and a crescent-shaped vertical tail fluke. Numerous examples of fossilized pregnant females also showed that ichthyosaurs gave live birth rather than laying eggs.
This highly dolphin-like version of ichthyosaurs quickly caught on and became the standard depiction into the early 20th century, frequently showing them as highly active animals – swimming in groups, chasing fish and ammonites, and leaping dramatically out of the water like their modern cetacean counterparts. While we don’t actually know if they were social or acrobatic like dolphins, it was still a surprising and refreshing contrast to the increasingly lumpy and sluggish depictions of non-avian dinosaurs that were happening around the same time.
Actual further paleontological study on ichthyosaurs was scarce for decades, however, with a general attitude that the group was already scientifically “complete” and there wasn’t much new or interesting left to learn about them anymore. It wasn’t until the late 20th century that they began to have their own “ichthyosaur renaissance” alongside the dinosaurs, with a sharp rise in research in the last few decades bringing us a lot of new information about their diversity and biology.
Ichthyosaurus communis was just one of several species in the Ichthyosaurus genus, living during the Early Jurassic, about 196-183 million years ago, in the shallow tropical seas of what is now Europe. About 3.3m long (~11’), it was adapted for high-speed long-distance swimming like a modern tuna, and it probably had a large keeled peduncle on the sides of its tail.
Some of the preserved pigmentation has enough microscopic detail to show what appear to be branched melanophore cells associated with the ability to change color – suggesting that ichthyosaurs may have been able to actively darken and lighten their coloration like some modern lizards.
okay I really hate to make another post but I just found out that my next paycheck from the government will be only half of what it typically is, and the normal amount covers my rent. Meaning I’ll have to come up with $400 to cover rent :)
I’m meeting with my supervisor about getting a second job at the nonprofit I work at to get me up to full time until I finish getting my GED and get into college to receive benefits again. I’ve been really good about my money, but there’s only so much I can do working 10 hours a week.
anyways, I’m ojibwe/lakota, a local activist for foster youth and youth of color in the system and I really don’t want to go back to retail and put my body through that to pay my bills. chi-miigwech friends :)
Hi, this post is getting a lot of notes but not much in terms of help :( so I’m going to offer earring commissions! I make hand crafted fringe beaded earrings independently.
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The base price is $30, since these do take me roughly 4 hours considering the length you’d like, and the width. This covers shipping as well. Since I don’t want anyone to feel like they’re “appropriating” Ojibwe culture by including native designs, I’ll be doing only ombre colors for now! ^^ feel free to direct message me for details.
The first known stegosaur fossils were found in England and South Africa between the 1840s and 1870s, but these dinosaurs weren’t properly recognized as a highly distinctive group until the discovery of Stegosaurus itself in North America during the late 1870s.
1880s
The first Stegosaurus reconstructions were based on fragmentary and disarticulated fossil material, and its life appearance was very poorly understood. Initially it was depicted as a bipedal long-necked animal, with its plates laying flat against its back like a turtle shell, numerous spikes across its back, and more plates running along its tail.
1890s-1970s
Better skeletons of the species Stegosaurus stenops were discovered in the late 1880s, and by the 1890s stegosaur anatomy was becoming clearer. Reconstructions quickly adopted an arch-backed body shape with a tiny head and drooping tail, short semi-sprawling forelimbs and long hindlimbs, and with the plates now properly upright on the back and the spikes at the end of the tail.
Stegosaurus’ unique appearance rapidly made it one of the most famous and recognizable dinosaurs to the general public. Its comical-seeming tiny head and even tinier brain also unfortunately ended up contributing to the prevailing early 20th century attitude that dinosaurs were sluggish and unintelligent, with the myth that it needed a “second brain” in its hips to control its huge body becoming a popular notion for quite some time.
The exact arrangement of the iconic back plates and tail spikes was uncertain for several decades, with early versions in the 1890s having up to eight tail spikes and a single row of plates. This was then updated in the 1900s to a double row of symmetrical plate pairs, and by the 1920s the standard arrangment had soon become an alternating two-row pattern with the tail spikes reduced to four – a layout that’s still considered correct today.
2020s
In the second half of the 20th century a combination of numerous new stegosaur species from China and the Dinosaur Renaissance began to revise the way Stegosaurus was understood, bringing it into a fully upright posture with its head and tail held high, and recognizing the convergently sauropod-like anatomy of its hands and feet.
But something still wasn’t right.
Compared to other known stegosaurs, Stegosaurus itself was starting to seem… rather weird. Its short neck, short forelegs, giant plates, sloping back and high rump were much more exaggeratedly proportioned than any of its relatives.
This was finally resolved in the 2010s when a near-complete specimen nicknamed “Sophie” was thoroughly described – and revealed that Stegosaurus’ proportions had been wrong the whole time. All previous skeletal reconstructions had been composites, put together from remains of multiple individuals that had all been different ages and sizes, and in the process had heavily distorted our idea of what this animal actually looked like.
It grew up to around 9m long (~30ft), and had a small head with a long narrow snout, with a toothless beak at the front of its jaws and small peg-shaped teeth further back. Bony ossicles lined the underside of its neck, possibly providing chainmail-like protection to its throat, and its skin was covered in tiny pebbly scales interspersed with “rosettes” formed around slightly larger oval scales. Its neck was longer than previously thought, more in line with other stegosaurs, and its torso and hind legs were a bit shorter, making its posture more horizontal and its back less arched.
The actual function of the large back plates is still uncertain. Ideas about them being defensive armor (and speculation about them even being moveable!) have mostly been discounted at this point, since they were actually relatively fragile – although their keratinous covering may have had a fairly sharp edge. Thermoregulation has been a popular explanation for many decades, with blood vessel impressions in the plates being proposed as evidence they were used as “radiators” to prevent overheating like the ears of modern African elephants.
But currently the most likely primary plate function is thought to be visual display, with the large plates increasing the perceived size of Stegosaurus either to intimidate predators and rivals or to impress potential mates. If this was the case then they may have also been strikingly colored and patterned in life.
Meanwhile the “thagomizer” on its tail actually does seem to have been a weapon, with injuries to that area of the body being fairly common, and several Allosaurus fossils have been found with puncture wounds the exact size and shape of Stegosaurus spikes. Articulated specimens have also shown that the tail curved downwards at the tip, holding the thagomizer with the spikes pointing horizontally outwards and backwards.
First discovered in Western Australia in the mid-1880s, the bizarre-toothed eugeneodont cartilaginous fish Helicoprion davisii was initially mistaken for a species of the equally weird Edestus. It was eventually recognized as part of a separate genus over a decade later, when similar fossils of its close relative Helicoprion bessonowi were found in the Ural Mountains.
1890s-2000s
With Helicoprion only known from strange buzzsaw-like spiral whorls, the function and location of this structure in the fish’s body was a huge source of confusion for over a century.
The earliest interpretation was a defensive structure curling upwards from the snout, then as part of the tail or dorsal fins. It was soon realized to probably be part of the lower jaw instead, but the exact arrangement was still a mystery.
A downward-curling position was popular in reconstructions for much of the 20th century. From the 1960s onwards, however, discoveries of preserved skull cartilage and soft-tissue body outlines of other eugeneodont species began to give a better idea of what these fish were and what they looked like. They were identified as being related to modern chimaeras, but with a very different appearance – they had streamlined shark-like bodies with large triangular pectoral fins, a single dorsal fin, no pelvic or anal fins at all, and broad keels along the sides of their tails.
A single tooth whorl sat in the middle of the lower jaw, with its sides covered by skin, and the largest and youngest teeth formed at the back before spiralling forwards, downwards, and inwards.
In the 1990s a “pizza-cutter” reconstruction gave Helicoprion long narrow jaws with the whorl positioned very far forwards, sawing and crushing prey against the underside of the snout. A version with the whorl very deep inside the throat was also proposed in 2008, but only a year later a new variant of the pizza-cutter saw-jaw model suggested the presence of a specialized “pocket” in the upper jaw lined with teeth.
2020s
Finally, in 2013, CT scanning of a Helicoprion specimen originally discovered in the 1960s revealed something incredibly special – an almost complete three-dimensionally preserved and articulated set of jaws. It showed narrow jaws that were shorter than the previous reconstructions, with the whorl occupying the entire lower jaw and braced by cartilage on each side.
We now know Helicoprion davisii was found worldwide during the early-to-mid Permian, about 272-268 million years ago, and based on some of the biggest known tooth whorls it may have reached sizes of up to 8m long (~26’), similar in size to modern basking sharks. It continuously added new and larger teeth to its whorl throughout its life, with the smaller older teeth being retained instead of shed, slowly pushed into a tight spiral deep inside the lower jaw.
The upper jaw formed a sheath-like pocket lined with a “pavement” of numerous tiny rounded teeth, and as Helicoprion closed its jaws the various parts of the whorl simultaneously grabbed, sliced, and pulled prey further into its mouth – a mechanism possibly specialized for efficiently de-shelling cephalopods like ammonites and nautiloids.
Therizinosaurs were some of of the most unique theropod dinosaurs. It’s only in the last few decades that we’ve started to understand much about them, and they’re still somewhat enigmatic even today.
1950s
The first known therizinosaur fossil discovery was Therizinosaurus cheloniformis, found in Southern Mongolia during the late 1940s and described and named in the mid-1950s based on a few fragments that included some unusually large and elongated claws.
These remains were interpreted as belonging to a giant turtle-like reptile that used its scythe-like claws to harvest aquatic plants – inspiring both parts of its scientific name, with Therizinosaurus meaning “reaper lizard” and cheloniformis meaning “turtle-shaped”.
1990s
The turtle interpretation began to be questioned during the 1970s, and the discovery of some slightly better (but still fragmentary) specimens reclassified Therizinosaurus as an unusual theropod dinosaur.
In the late 1970s and early 1980s fossils of another group of dinosaurs known as “segnosaurs” were also starting to be discovered, with a confusing mixture of anatomical features that seemed to link them to multiple different dinosaur lineages. As a result opinions about their evolutionary relationships varied during the 1980s, sometimes considering them to be theropods, sometimes late-surviving “relic” prosauropods, and sometimes a whole new major lineage of rare and weird saurischians.
Similarities between segnosaurs and the known material of Therizinosaurus were soon noted, and the discovery of the fairly complete Alxasaurus in the early 1990s confirmed that they were all part of the same group of bizarre herbivorous theropods – and the name “segnosaurs” was dropped in favor of “therizinosaurs”, since older names usually get priority in taxonomy.
Reconstructions of Therizinosaurus during this time tended to look rather weird and awkward. As with the majority of dinosaurs during this period it was depicted as entirely scaly and reptilian, and was often shown with a stiff hunched downcurving neck and an oddly tiny-looking tail.
Further discoveries during the 1990s finally began to clarify therizinosaurs’ evolutionary affinities, eventually placing them as an early branch of bird-like maniraptoran theropods, closely related to both oviraptorosaurs and the alvarezsaurs – and in 1999 the discovery of the small early therizinosaur Beipiaosaurus helped to confirm this relationship, revealing impressions of an extensive coat of filamentous feathers and longer stiffer quill-like structures.
2020s
Over the next couple of decades more and more therizinosaur fossils were found in both Asia and North America, and details about these dinosaurs’ appearance, biology, and ecology gradually became better understood. While there’s still a lot we don’t know about them, we do now at least have some fairly complete examples like Nothronychus, fossilized therizinosaur footprints, more feathers, an idea of Beipiaosaurus’ coloration (it was brown!), and even eggs and potential colonial nesting sites.
And while Therizinosaurus itself is still only represented by fragmentary and incomplete material, we now have a much better idea of what it was probably like. It lived in what is now the Gobi Desert during the Late Cretaceous, about 70 million years ago, and would have been both the largest known therizinosaur and the largest known maniraptoran dinosaur, estimated to have been as much as 10m long (33’) based on the proportions of its relatives.
It would have had a tiny head with a toothless beak at the front of its jaws, a long neck, and a wide bulky “pot-bellied” body housing its huge plant-fermenting gut. With its especially large body size it probably wasn’t as extensively feathered as its smaller relatives, but it may have still been sparsely fuzzy across parts of its body.
Unlike most other theropods it walked on all four toes of its feet, with the dewclaw enlarged into an extra weight-bearing digit. Recent analysis of footprints has also suggested that the larger therizinosaurs like Therizinosaurus may actually have been plantigrade, walking with their feet completely flat on the ground. This might turn out to just be an artifact of how the tracks were preserved, but therizinosaurs are certainly already weird enough that it could be a plausible interpretation.
But Therizinosaurus’ most distinctive feature was its hands, with extremely long narrow claws each at least 50cm long (1'8"). Unlike the strongly curved claws seen in other therizinosaurs, these ones were fairly straight for most of their length, only curving more sharply towards their tips.
While in the past these claws have been proposed as being weapons or digging adaptations, they were actually relatively delicate and were probably mainly used for pulling clumps of vegetation closer in a convergently similar manner to the later mammalian chalicotheres and ground sloths.
Therizinosaurus would have been a heavy slow-moving animal, and probably spent a lot of time sitting on its haunches supported by its especially robust hip bones while it browsed on large amounts of vegetation. It likely relied on its pure bulk and intimidation to deter potential predators, possibly even making aggressive displays with its claws when threatened – essentially it may have been a giant goose-sloth.
Ratty. 27 Transmasc Nonbinary, Florida. A 'Kin of Rodent tendencies, a system. Acearotrans exclusionists/transmeds /gender crits, go eat sandpaper. Safe sex positive. If I reblog something from a reg, pm me and they'll be deleted+blocked from my blog. White as hell so please call me out when I fuck up. Please don't interact with me if you're a little.
