dinosaur – Page 6 – Nix Illustration

Retro vs Modern #02: Iguanodon bernissartensis

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 20^th 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.

Retro vs Modern #01: Megalosaurus bucklandii

It’s time for Retro vs Modern Month!

Every weekday this March we’ll be looking at some examples of how our paleontological understanding and visual depiction of various fossil creatures has evolved over the years.

Starting with…

Retro vs Modern #01: Megalosaurus bucklandii

Fragmentary fossil remains of dinosaurs have been found in Southeast England for hundreds of years, but it wasn’t until the 1820s that they were properly recognized as belonging to an ancient “great lizard” given the name Megalosaurus bucklandii – the very first non-avian dinosaur known to science, almost two decades before the term “dinosaur” would even be created to categorize these extinct animals.

1850s

The Victorian Crystal Palace reconstruction of Megalosaurus is often mocked for its inaccurate bulky appearance, but for its time it was actually an incredibly progressive vision of a predatory dinosaur. It was depicted as an alert, active, bear-like beast with upright muscular limbs, and a humped back based on what later turned out to actually be remains of a different dinosaur species.

1890s-1960s

Discoveries of other large theropod dinosaurs revealed their bipedal posture, and Megalosaurus reconstructions were revised to show an upright kangaroo-like stance. But despite some other early portrayals of active agile dinosaurs, the overall opinion of these animals began to drift during the first half of the 20^th century towards sluggish tail-dragging reptiles: depicting them as slow, stupid, cold-blooded, awkward and obsolete evolutionary failures whose extinction had been inevitable.

2020s

Starting in the late 1960s the Dinosaur Renaissance finally began to shift thinking back towards active and warm-blooded dinosaurs, recognizing theropods’ close evolutionary relationship to modern birds and correcting their posture into a horizontal stance with a counterbalancing tail. And while Megalosaurus itself is still only known from fragments, discoveries of more completely preserved relatives like Torvosaurus have given us a much better idea of what it was probably like.

We know know Megalosaurus lived on what at the time was a subtropical island in the shallow western Tethys Sea, about 166 million years ago during the Mid Jurassic. It would have been around 8m long (~26′), with a long narrow snout, and short muscular arms with enlarged meathook-like thumb claws. Its legs and tail would have been fairly thick and bulky, and it may have had a covering of hair-like protofeathers on its body.

Stegouros

While some ankylosaurs are famous for their specialized tail clubs, Stegouros elengassen here had something else entirely going on with its rear end.

Known from the late Cretaceous of southern Chile, about 75-72 million years ago, this small ankylosaur was around 1.5m long (~5′), roughly the size of a large dog. It had a proportionally larger head and more slender limbs than most other ankylosaurs, and a pelvis more resembling a stegosaur, but its most distinctive feature was its tail – it had a completely unique never-before-seen type of tail weapon, with a flat “frond-like” structure formed from several pairs of large fused osteoderms making a shape resembling a macuahuitl.

It seems to have been part of a previously unrecognized very early-branching lineage of Gondwanan ankylosaurs – the parankylosaurians – with its closest relatives Antarctopelta and Kunbarrasaurus also included in this new group. And since the tail regions of both of those other species are poorly known, this means they may also have possessed macuahuitls.

Spectember 2021 – Quadrupedal Pachycephalosaurs

Today’s #Spectember concept comes from an anonymous submitter:

Qinornis

66 million years ago, the end-Cretaceous mass extinction wiped out all dinosaurs except for the avian bird lineage.

…Or did it?

But I’m not talking about the dubious claims of non-avian dinosaur fossils found in places they shouldn’t be. This is about something else entirely: an unassuming little bird known as Qinornis paleocenica.

Living in Northwest China during the mid-Paleocene, about 61 million years ago, Qinornis was roughly pigeon-sized at around 30cm long (12″). It’s known only from a few bones from its legs and feet, but those bones are unusual enough to hint that it might have been something very special.

Uniquely for a Cenozoic bird, some of its foot bones weren’t fully fused together. This sort of incomplete fusion is seen in both juvenile modern birds and in adults of non-avian ornithurine birds from the Cretaceous – and the Qinornis specimen seems to have come from an adult animal.

If it was fully grown with unfused feet, then that would suggest it was actually part of a “relic” lineage living 5 million years after the mass extinction, surviving for quite some time longer than previously thought.

The last known non-avian dinosaur.

Brontornis

Brontornis burmeisteri was one of the largest flightless birds known to have ever existed, standing around 2.8m tall (9’2″) and estimated to have weighed 400kg (~880lbs).

Known from the early and mid-Miocene of Argentina, between about 17 and 11 million years ago, it’s traditionally considered to be one of the carnivorous terror birds that dominated predatory roles in South American ecosystems during the long Cenozoic isolation of the continent.

But Brontornis might not actually have been a terror bird at all – it may have instead been a giant cousin of ducks and geese.

The known fossil material is fragmentary enough that it’s still hard to tell for certain, but there’s some evidence that links it to the gastornithiformes, a group of huge herbivorous birds related to modern waterfowl.

If it was a gastornithiform, that would mean it represents a previously completely unknown lineage of South American giant flightless galloanserans. And, along with the gastornithids and the mihirungs, it would represent a third time that group of birds convergently evolved this sort of body plan and ecological role on entirely different continents during the Cenozoic.

Aquilarhinus

Aquilarhinus palimentus here was an early hadrosaurid dinosaur known from the Late Cretaceous of Texas, USA, living about 80 million years ago. Around 5m long (16″5″), it had a prominent humped nose that seems to have been an evolutionary prelude to the larger and much more elaborate crests found in later hadrosaurs.

It also had an unusually wide and shovel-like beak, unlike any other known hadrosaur, which was probably a specialization for a different diet than its relatives. Since it lived along coastal marshlands it may have used its broad jaws to scoop up large mouthfuls of soft vegetation – or, much like the “shovel-tusker” proboscideans that were once thought to have a similar lifestyle, it may actually have been doing something else entirely with that beak.

Shri

About 72 million years ago, in the Late Cretaceous of what is now Mongolia, a dead dromaeosaurid dinosaur lost its head.

30 years ago, in 1991, its headless fossilized remains were discovered during a joint Mongolian Academy of Sciences / American Museum of Natural History expedition in the Gobi Desert.

For a long time the specimen was known only by the nickname of “Ichabodcraniosaurus”, in reference to a character haunted by a headless ghost in the story The Legend of Sleepy Hollow – but now it’s finally been given a full scientific description and a proper name.

Say hello to the first new non-avian dinosaur of 2021, Shri devi!

Named after a buddhist deity, this little dinosaur was around 2m long (6’6″), roughly the size of a modern peacock or wild turkey. It was a very close relative of Velociraptor, but lived in a slightly different part of the ancient Gobi than its famous cousin, giving us a glimpse of how dromaeosaurid species varied across that region.

A map of the Gobi region of Mongolia and China, showing locations where various dromaeosaurid dinosaur fossils have been found. — [ From fig 28 in Turner, A. H. *et al* (2021). A New Dromaeosaurid from the Late Cretaceous Khulsan Locality of Mongolia. *American Museum Novitates*. https://doi.org/10.1206/3965.1 ]

Eons Roundup 9

New year, new PBS Eons commission roundup day!

An illustration of an extinct early walrus. Unlike modern walruses it has no tusks, more resembling a sea lion in appearance. — Neotherium mirum

An illustration of an extinct species of walrus. It has shorter thicker tusks than modern walruses, and it's depicted grubbing around on a muddy seafloor for buried shellfish. — Neotherium mirum

The ancient walruses Neotherium and Valenictus, from “How the Walrus Got Its Tusks”
https://www.youtube.com/watch?v=BKDGYGV2LK8

An illustration of an extinct nodosaur, a type of quadrupedal herbivorous dinosaur. Its body is covered in densely-packed knobbly spiky armor. — Borealopelta markmitchelli (life restoration)

An illustration of the carcass of an extinct nodosaur, a type of quadrupedal herbivorous dinosaur. Its body is covered in knobbly spiky armor, and its belly is massively bloated up from trapped gasses, forcing it to have turned upside down. — Borealopelta markmitchelli (life restoration)

The nodosaurid ankylosaur Borealopelta, in both alive and “bloat-and-float” carcass states, from “The Dinosaur Who Was Buried at Sea”
https://www.youtube.com/watch?v=a-UZXBF63z4

An illustration of an extinct ankylosaur, a type of quadrupedal herbivorous dinosaur. Its body is covered in knobbly spiky armor, but unlike most other ankylosaurids it has no bony club at the tip of its tail. — Gobisaurus domoculus

An illustration of an extinct ankylosaur, a type of quadrupedal herbivorous dinosaur. Its body is covered in knobbly spiky armor, and it has a small bony club at the tip of its tail. — Gobisaurus domoculus

The ankylosaurid ankylosaurs Gobisaurus and Dyoplosaurus, from “How Ankylosaurs Got Their Clubs”
https://www.youtube.com/watch?v=lRt-4SdzWrk

Elsornis

The enantiornitheans (“opposite-birds”) were the most diverse and widespread group of Mesozoic birds, existing all around the world throughout the Cretaceous period. They retained claws on their wings and had toothy snouts instead of beaks, and while most of them lacked the lift-generating tail fans of modern birds they appear to have still been very adept fliers.

But Elsornis keni here was doing something different.

Known from the Late Cretaceous of Mongolia, about 80 million years ago, this opposite-bird lived alongside famous dinosaurs like Velociraptor and Protoceratops in what is now the Gobi Desert. Only a single partial specimen has ever been found, so its full life appearance is unknown and this reconstruction is somewhat speculative, but it would have been around the size of a pigeon at 25cm long (10″) – not including any decorative tail feathers it may have had, similar to other enantiornitheans.

It wing and shoulder bones were very odd for an opposite-bird, with proportions that don’t match anything capable of competent flight. Instead Elsornis appears to have been a flightless enantiornithean, a representative of a previously unknown terrestrial lineage.