dinosaur – Nix Illustration

Mexidracon

Mexidracon longimanus was an ornithomimid dinosaur that lived during the late Cretaceous, about 72 million years ago, in what is now northern Mexico.

It was a fairly small ornithomimid at around 2.5-3m long (~8-10′), and its leg proportions suggest it was less specialized for fast running than some of its other relatives. But its most unique feature was its hands, with extremely elongated metacarpal bones – giving it palms that were longer than its upper arm!

It’s unclear what the function of these unusual limbs was. Possibly they gave Mexidracon extra reach to hook its claws onto foliage and pull it within reach of its head, in a similar manner to ground sloths, chalicotheres, and therizinosaurs.

Isisaurus

Isisaurus colberti was a sauropod dinosaur that lived in what is now India and Pakistan at the end of the Cretaceous Period, about 70-66 million years ago.

It was part of the titanosaur group of sauropods and had some unusual proportions* compared to its close relatives, with elongated forelimbs and a relatively short chunky neck. Since it’s only known from a partial skeleton its full size is unknown – estimates have been made as large as 18m long (~60′) but it was probably somewhat smaller, closer to around 11m in length (36′).

(*Measurement errors in the original paper resulted in some very weird proportions, but more recent and rigorous reconstructions have made Isisaurus not quite so cursed-looking.)

Like most other titanosaurs it probably lacked the thumb claws seen in other sauropods, and it may also have had some bony osteoderm armor studding its skin.

Coprolites that may represent Isisaurus’ poop show evidence of several different fungi that grow on tree leaves in humid tropical and subtropical climates, suggesting that this sauropod was a selective browser somewhat like modern giraffes.

Avisaurus

Avisaurus darwini here lived at the very end of the Cretaceous, about 66 million years ago, in what is now the Hell Creek fossil beds in Montana, USA.

It was a member of a diverse group of Mesozoic birds known as enantiornitheans, which retained claws on their wings and often still had toothed snouts instead of beaks – and being part of the avisaurid family it was also one of the larger known examples of these birds, similar in size to a modern hawk at around 60cm long (~2′).

Although this species is only known from isolated foot bones, the remains have distinct enough anatomical features to show that Avisaurus had powerful gripping talons similar to those of modern hawks and owls, suggesting it had a similar lifestyle hunting small vertebrate prey in the ancient swampy Hell Creek ecosystem.

Spectember/Spectober 2024 #07: Mole Dino

Today’s spec creature is a combination of a couple of submissions – James P. Quick asked for “a post-K/Pg relict dinosaur from pre-glaciation Antarctica”, and an anonymous asked for “a subterranean (like, say, Talpa or Spalax) burrowing dinosaur”:

At the time of the K/Pg mass extinction some of the small ornithopods that inhabited Late Cretaceous Antarctica had been developing increasingly complex burrowing behavior and a more generalist omnivorous diet than most other ornithischians – and, along with their ability to endure the long dark cold polar winters, this was juuust about enough for them to survive while the rest of their non-avian cohorts vanished.

They were very briefly a fairly successful disaster taxon in the devastated polar forests, but they were quickly displaced by other diversifying survivors and never really got another ecological foothold to regain anything close to the non-avian dinosaurs former glory.

Instead the little ornithopods specialized even further for burrowing, spending more and more of their lives underground to avoid the increasing competition and predation from mammals and birds.

A shaded sketch of a speculative descendant of small ornithopod dinosaurs in Antarctica. It's a fuzzy little mole-like animal with a hoked beak at the tip of its toothy snout, no eyes, a keratinous shield on its head, large shovel-clawed forelimbs, a chunky body, stocky legs, and a fat bristly tail.

Now, well into the Cenozoic at the dawning of the Miocene, Cthonireliqua quicki is the very last representative of the non-avian dinosaurs. Small and stocky and mole-like, just 15cm long (~8″), it has muscular forelimbs with large shovel-like claws, a keratinous shield on its head, and a thick bristly tail where large fat reserves are stored.

Its eyes are almost completely absent, only vestigial remnants present under the skin of its face, and it navigates its extensive burrows using sensitive whisker-like filaments and its keen senses of hearing and smell. Still omnivorous like its ancestors, it feeds on whatever it comes across while tunneling – mainly worms, insects, smaller vertebrates, roots, and tubers.

Unfortunately for Cthonireliqua, and the rest of its Antarctic ecosystem, time is running out. Over the last few million years Antarctica’s climate has been steadily cooling and drying, the continent has become fully isolated, and the Antarctic Circumpolar Current has formed. Glaciation is well underway in the continental interior, and the once-lush forests are shrinking away and being replaced with tundra.

Soon all evidence of these dinosaurs’ existence will be buried under the ice.

Spectember 2024 #03: Terrible Toucan

This concept comes from thecomiccreator, who suggested a “carnivorous/omnivorous toucan”:

A shaded sketch of a speculative descendant of toucans, shown both standing on one leg and in flight. Its a stork-like bird with a massive long serrated beak, a bald vulture-like head and ruffed neck, large broad wings with slotted flight feathers, and long legs with two forward-facing toes and two backwards-facing toes.

Descended from toco toucans inhabiting savanna grasslands, Deinotukan auctorcomicus is a large stork-like bird standing about 1.2m tall (~4′).

Unlike its mostly-frugivorous ancestors it’s primarily a scavenger, soaring on thermals with its long broad wings and following vultures towards sources of carrion. Its massive serrated beak allows it to efficiently open up tough-skinned carcasses, and with its nostrils positioned up near its eyes it can probe around inside much deeper than other scavengers while still being able to breathe.

It also opportunistically hunts live prey, especially during the breeding season while raising chicks, slowly stalking around on foot snatching up anything small enough to fit in its mouth and be swallowed whole.

Its beak contains an extensive network of blood vessels, which along with the large surface area make it an effective way of shedding excess heat in its hot tropical habitat – but when soaring at high altitudes where temperatures are near-freezing it’s also able to shunt blood flow away from its beak to conserve body heat instead.

Compsognathus

First discovered in the 1850s, Compsognathus longipes was the first theropod dinosaur known from a fairly complete skeleton, and also the smallest known non-avian dinosaur for over 130 years.

(A second specimen was also, briefly, the “first” aquatic non-avian dinosaur, but that’s another story.)

Living in what is now Europe during the late Jurassic, about 150 million years ago, it was a lightly built animal with long legs and a long tail, growing to around 1.2m long (~4′). Its hands seem to have had only two functional fingers, with the third being vestigial and possibly not even having a claw.

Skin impressions from about a third of the way along its tail show small bumpy scales – but since other compsognathids like Sinosauropteryx are known to have been covered in fur-like feathers, this likely means that just that particular region of Compsognathus’ body wasn’t fluffy.

Some of Compsognathus‘ diet is known for certain, since preserved gut contents show it fed on smaller vertebrates like lizards and rhynchocephalians. The remains of a lizard in the stomach of one specimen were even identified as belonging to a previously-unknown species, Schoenesmahl dyspepsia, with the dismembered nature of the skeleton suggesting Compsognathus tore its prey into bite-sized chunks in a similar manner to modern predatory birds.

Lokiceratops

Lokiceratops rangiformis was a ceratopsian dinosaur that lived during the Late Cretaceous (~78 million years ago) in what is now Montana, USA. Estimated at about 6.7m long (~22ft), it was one of the largest known members of the centrosaurine branch of the ceratopsians.

It had a unique arrangement of ornamentation on its skull, with no nose horn, two long brow horns, and a pair of huge asymmetrical curving blade-like spikes on the top of its square frill – some of the largest known frill spikes of any ceratopsian.

It lived in a swampy environment near the shore of the Western Interior Seaway, in an area that seems to have had an unusually high diversity of ceratopsians – along with Lokiceratops there were three other centrosaurines (Medusaceratops, Albertaceratops, and Wendiceratops), and one chasmosaurine (Judiceratops).

(There’s also a possibility that it might not actually be a unique species. We know some other ceratopsians’ faces changed quite drastically as they aged, so Lokiceratops could instead represent a fully mature individual of Medusaceratops.)

Xenerodiops

Xenerodiops mycter was an unusual heron from the Oligocene (~30 million years ago) of what is now Egypt.

Known only from a partial skull and an arm bone, it’s estimated to have stood around 70cm tall (~2’4″) and was probably fairly similar in overall appearance to modern night herons. Its beak was powerfully built and had a distinctive downwards curve, shaped more like some types of stork than other herons – suggesting it may have had a convergently stork-like lifestyle, slowly walking through its marshy habitat probing around for prey and snapping up whatever its beak came into contact with.

Patagopteryx

While birds are one of the few animal groups to have achieved powered flight, they’re also very prone to losing their aerial abilities. Many times over their evolutionary history, multiple different bird lineages have convergently become secondarily flightless – and Patagopteryx deferrariisi was one of the earliest known examples of this.

Living during the Late Cretaceous, about 86-84 million years ago, in what is now the northern part of Argentine Patagonia in South America, Patagopteryx was roughly the size of a modern chicken at around 50cm long.

When it was first discovered it was classified as a ratite, but soon after it was recognized as actually being a much earlier type of bird, an early ornithuromorph only distantly related to any modern groups.

It had small wings, little-to-no keel, and no wishbone, indicating it lacked the large powerful musculature required for flight. Its legs were quite long, with large feet with all four toes facing forward – proportions that suggest it was built more for walking than for high-speed running.

Growth rings in its bones also show that it had a much slower growth rate than modern birds, taking several years to reach adult size.

April Fools 2024: The Curious Case Of The Chunky-Necked Ceratopsians

Much like the aquatic Compsognathus featured here a couple of years ago, not every novel idea that came out of the Dinosaur Renaissance was a winner.

And one of the oddest examples came from author/illustrator John C. McLoughlin.

His 1979 book Archosauria: A New Look at the Old Dinosaur featured an unusual interpretation of ceratopsian dinosaurs’ characteristic bony frills, proposing that they were actually muscle attachment sites for both powerful jaw muscles and enormous back muscles to help hold up their large heavy heads. This would have completely buried the frill under soft tissue, giving the animals massive thick necks and humped shoulders, and resulted in an especially weird reconstruction of Triceratops with a grotesque sort of wrinkly sewn-together appearance.

This concept didn’t entirely originate from McLoughlin – three years earlier in 1976 he’d illustrated Ronald Paul Ratkevich’s book Dinosaurs of the Southwest, which seems to have been the inspiration for Archosauria’s fleshy-frilled ceratopsians. A few paleontologists had also proposed jaw muscles attaching onto the frills during the 1930s and 1950s, and there’s even a book from as far back as 1915 that also shows the top of a Triceratops’ frill connected to its back! But McLoughlin’s Archosauria image is still by far the most extreme and infamous version of the idea.

There were a lot of things in Archosauria that were actually very forward-thinking for the time period, such as putting fuzz and feathers on small theropods and depicting non-avian dinosaurs as active fast-moving animals. The unique ceratopsian reconstructions, however, never caught on for several big reasons:

Firstly, all that hefty muscle tissue would have locked ceratopsians’ heads firmly in place, unable to move at all, which just doesn’t make sense biomechanically. Then there was the lack of skeletal evidence – muscles that big should have left huge visible attachment scars all over the frill bones, and there was no sign of anything like that on any fossil specimens. Finally, it turns out the ceratopsian head-neck joint was actually highly mobile, suggesting their heads were free to make a wide range of motions in life.

As wrong as they were even at the time, McLoughlin’s ceratopsians were still an interesting speculative idea, and notable for advocating for fleshier dinosaur reconstructions at a time when paleoart was trending towards shrinkwrapping.