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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 ]

Paraceratherium

While the largest animal known to ever exist is an aquatic mammal (the modern blue whale), mammals on land have never managed to attain the same sort of massive sizes seen in the sauropod dinosaurs. This is probably due to a combination of factors, including their reproductive strategies, metabolisms, and physiological differences like lacking internal air sacs – but even being limited to overall smaller body sizes, some of the mega-mammals known to have evolved during the Cenozoic were still absolutely enormous.

And one of the largest was Paraceratherium transouralicum.

(The exact name of this animal has a long and complicated history, and in various times and places it’s also been known as Indricotherium, Baluchitherium, and Pristinotherium.)

Found across much of Eurasia during the Oligocene, about 34-23 million years ago, Paraceratherium was part of an ancient lineage of long-legged hornless rhinoceroses. It stood around 4.8m tall at the shoulder (15’9″) – big enough that most modern humans would be able to walk right underneath its belly without even having to duck – and it had elongated limbs and a long neck that gave it an overall appearance much more like a giant weird horse than a rhino.

There was a pair of downward-pointing tusks at the front of its upper jaw, and the shape of the nasal region of its skull suggests its nose formed a short prehensile tapir-like trunk, which would have been used to help grab and strip leaves from high branches.

I’ve also reconstructed it here with a speculative dewlap on its neck, used for both display and thermoregulation.

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

Guizhouichthyosaurus

In the mid-Triassic seas, covering what will one day be part of southwestern China, an ichthyosaur flails at the surface desperately trying to deal with an ambitiously large meal.

240 million years later human paleontologists will name their kind Guizhouichthyosaurus tangae, and initially assume that their narrow snout and small peg-like teeth are suited only for a diet of small soft-bodied fish and cephalopods.

In reality they eat a much wider range of prey – including other marine reptiles.

But for a 5m long (16’5″) Guizhouichthyosaurus, perhaps this particular catch is a little too much. The unlucky thalattosaur was a rather large example of a Xinpusaurus xingyiensis – nearly matching the ichthyosaur in length at around 4m long (13’2″), although much less bulky – and after biting off the head and tail the predator is still struggling to actually eat the sizeable carcass.

Even with a gravity assist from holding their prize vertically up above the water, swallowing is proving difficult and the Guizhouichthyosaurus can’t breathe around it.

They’re slowly suffocating.

They’ll eventually get it down their gullet, but by then it’ll be too late. Weak and dizzy from asphyxiation, they’ll soon sink to the sea floor and never resurface, their body settling not very far from where their prey’s severed tail fell.

Harpagofututor

Sometimes sexual dimorphism in the fossil record is hard to identify for certain – and sometimes it’s incredibly obvious.

Harpagofututor volsellorhinus here is a wonderful example of the second category. This 17cm long (~7″) cartilaginous fish was a distant relative of modern chimaeras, and lived during the Early Carboniferous about 326-318 million years ago in the shallow tropical sea that formed the Bear Gulch Limestone deposits in Montana, USA.

While all specimens show an elongated eel-like body, they come in two different forms: one with a fairly normal skull, and one with a pair of huge jointed cartilaginous appendages in front of its eyes that resemble antennae or antlers.

The presence of large claspers on the “antlered” forms indicated they were males, with the weird appendages probably being used either for display or as “grappling hooks” to hang onto females during mating.

(Modern male chimaeras also have clasping structures on their heads!)

Meanwhile a couple of non-antlered specimens preserved with unborn offspring still inside their bodies confirmed that these unadorned forms of Harpagofututor were indeed females. Some of their young were quite large and well-developed, suggesting live birth, and with multiple different fetal growth stages found within a single mother it’s also a rare example of fossilized superfetation.

Smilesaurus

Despite having a genus name that sounds more like it should belong to a cartoon dinosaur mascot for dental hygiene, Smilesaurus ferox was actually a real gorgonopsian, a predatory synapsid distantly related to modern mammals.

Living in South Africa during the Late Permian, around 259-254 million years ago, Smilesaurus was comparable to a medium-sized dog at around 1m long (3’3″). It had some of the longest sabre-like canine teeth of any known gorgonopsian, proportionally comparable to those of sabertoothed cats – and it may have hunted in a similar manner, using powerful grasping limbs to pin down struggling prey and then dispatching it with slashing bites.

…And it also turns out that when you don’t horribly shrink-wrap a gorgonopsian, you end up with something that looks rather like a bear-hippo.

(For some similarly chonky gorgonopsians, check out Tas’ @i-draws-dinosaurs reconstructions here. Bullet Man was definitely a bit of an inspiration in this.)

Leptostomia

Leptostomia begaaensis here is a recently-discovered pterosaur that lived during the mid-Cretaceous period, around 100 million years ago.

Its fossil remains were found in the Kem Kem beds of Morocco – ancient river deposits famous for yielding some of the newer specimens of the bizarre aquatic dinosaur Spinosaurus – and consist of just a couple of small pieces of jaw bones.

But those fragments are rather weird for a pterosaur.

While it’s hard to tell for certain from such meagre remains, Leptostomia might have been part of the azhdarchoid lineage, related to both the elaborately-crested tapejarids and the terrestrial-stalking giants like Quetzalcoatlus. And if it was indded an azhdarchoid it was an especially tiny one, possibly the smallest known member of the whole group. Based on the proportions of its relatives it would have stood just 30cm tall (1′) with a wingspan of 60-70cm (2′-2’4″), roughly comparable in size to a modern pigeon.

And it had an incredibly long beak that tapered to a thin delicate tip, resembling the beaks of modern probe-feeding shorebirds more than any other known pterosaur. It may have been specialized for the same sort of ecological niche, poking around in mud and shallow water for small invertebrates and snapping them up, possibly detecting its hidden prey using super-sensitive nerve endings in the tip of its beak.

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.

Heckerites

While most modern echinoderms display the group’s characteristic five-way symmetry, there were plenty of much much stranger-looking forms back during the Paleozoic.

And some of the most confusing of them were the paracrinoids, which evolved an incredibly diverse range of body shapes during their group’s relatively short 40 million year existence during the Ordovician.

Despite the name these echinoderms weren’t particularly closely related to true crinoids, instead being part of a completely extinct lineage known as the blastozoans. Their ancestors had been radially symmetric, but paracrinoids largely abandoned that body plan, instead developing irregularly shaped and often asymmetric bodies ranging from round to flattened. They had between two and five “food grooves” on their upper surfaces, derived from the ambulacra, lined with numerous feeding appendages along only the left side of each.

They were shallow-water animals, living either attached to the seafloor by a long stem or anchored into the sediment by a shorter one, suspension feeding with their appendages and transporting the food particles towards the mouth located between the bases of the food grooves.

(…And speaking of mouths, some paracrinoid species appear to have had two of them.)

Heckerites multistellatus here lived around 458-445 million years ago, during the Late Ordovician. It inhabited the then-subtropical seas of the Baltica region, with fossil material known from what is now Estonia, southeastern Norway, and northwest Russia.

About 10cm tall (4″), it lived on the seafloor in sheltered waters protected from strong waves by large reefs, and is unusual even among its weirdo relatives for features such as retaining feeding appendages on both sides of its food grooves – although irregularly arranged and with fewer on one side than the other. Its body was shaped rather like a flattened bean, with two food grooves diverging from roughly the centre of the top margin, chunky skeletal plates forming a border around its edges, and a short stem at is base.

It also had an unusually large “anal pyramid” on the opposite side of its body from its mouth, and this may have been used for respiration as well as waste expulsion, similar to modern sea cucumbers.

Brachydectes

The lysorophians were a group of Carboniferous and Permian tetrapods with highly elongated bodies and tiny limbs, usually thought to be part of the lepospondyl amphibians – but some recent studies have instead placed them and some of their close relatives as possibly being very early members of the reptile branch of amniotes.

Brachydectes newberryi here is one of the best-known lysorophians, represented by a good amount of fossil material compared to many of its relatives. Living in the Midwestern United States during the late Carboniferous and early Permian, around 310-290 million years ago, it had a proportionally tiny head and reached lengths of around 60-70cm (2′-2’4″).

Its wide shovel-shaped snout and thickened reinforced bones around its braincase suggest it was adapted for headfirst digging, and some specimens have actually been found preserved inside their burrows. The roof of its skull also developed extensive “sculpturing” as individuals aged, with juveniles having smooth bone surfaces and larger adults having a distinct rough bumpy texture.

So I’ve depicted it here with a speculative keratinous “head shield”.