paleoart – Nix Illustration

Gargoyleosaurus

Gargoyleosaurus parkpinorum was a very early ankylosaur that lived in what is now Wyoming, USA, during the Late Jurassic, about 154-150 million years ago.

Known from a partial skeleton — including much of its armor preserved in place — it was a fairly small ankylosaur, around 3.5m long (~11’6″). Its head was proportionally small, its snout was rather narrow, and unlike later members of the group it still had teeth in the front of its jaws.

It would have inhabited the warm and semi-arid “Jurassic savanna” environment of western North America, feeding on vegetation along river flood plains and sharing its ecosystem with more famous dinosaurs such as Stegosaurus, Diplodocus, and Allosaurus.

Alienacanthus

Alienacanthus malkowskii was a placoderm armored fish that lived in the seas covering what is now Europe and northern Africa during the late Devonian, about 365 million years ago.

First discovered in the 1950s, this species was originally known only from some strange elongated bony elements that were interpreted as fin spines. But more recent finds of near-complete skull material revealed a surprise — the “spines” were actually this animal’s extremely elongated lower jaw!

Around 2.5m long (~8’2″), it was probably a streamlined open ocean swimmer that may have used its bizarre underbite similarly to the snouts of modern billfish, slashing at and stunning soft-bodied prey.

Ogresuchus

Ogresuchus furatus was a small crocodyliform that lived during the Late Cretaceous, about 66 million years ago, in what is now Catalonia, Spain.

It was originally classified as a sebecid, which would have made it the earliest known member of that family, but a more recent analysis suggests it was probably instead an atoposaurid.

Around 1m long (~3’3″), it was a lightly-built generalist predator that would have fed on invertebrates and small vertebrates — possibly even including sauropod hatchlings, since its fossil remains were discovered in a titanosaur nesting site.

Mamenchisaurus

Although sauropod dinosaurs are famous for their long necks, one group known as mamenchisaurids took that particular feature to the extreme, with elongated necks that made up around half of their total body length.

And ‘Mamenchisaurus’ sinocanadorum* was one of the largest and longest. Living in what is now northwestern China during the Late Jurassic, about 160 million years ago, it had a 15m-long neck (~49′) and an estimated total length of 25-30m (~82-98′).

(*The whole Mamenchisaurus genus is a bit of a wastebasket and needs revision. Recent phylogenetic analyses suggest M. sinocanadorum was closer related to Xinjiangtitan than to other Mamenchisaurus species, but whether it actually belongs in that genus instead or merits its own new name has yet to be determined.)

Its enormous neck was ultralightly-built and highly pneumatic, with the vertebrae containing around 70% air sacs by volume. Extremely long cervical ribs served to stabilize the neck, but would also have limited flexibility along most of its length — it may have operated like a crane arm, sweeping around to feed on vegetation across a wide arc without having to move its body at all.

Bataspis

Bataspis crux was an armored jawless fish that lived during the early Devonian, around 419 million years ago, in coastal marine waters covering what is now southwestern China.

It was a member of the galeaspids, a group characterized by massive headshields covered in a pattern of sensory canals, with a large opening on the front top surface between the eyes. While this hole often looked like a comical mouth, it was actually a single nostril that took in water for the gills, while the real mouth was located on the animal’s underside.

Galeaspids also had scaly bodies with three dorsal fins, a tail fin, and long low ribbon-like fins along the sides that may have been the precursors to paired fins in jawed fish.

Bataspis’ headshield was unusually shaped compared to its relatives, with sweeping side projections forming a distinct “batwing”. Hydrodynamic simulations indicate that it functioned as a hydrofoil, generating lift while swimming and making Bataspis an efficient underwater glider — and suggesting that galeaspids were much more ecologically diverse than previously thought.

Ictitherium

Ictitherium ebu* was a hyena that lived in what is now Kenya during the late Miocene and early Pliocene, around 7-5 million years ago. It was part of an early branch of the hyaenids known as ictitheres, dog-like hyenas found across Miocene Africa and Eurasia that occupied similar ecological niches to modern canids.

(*alternatively classified as Hyaenictitherium ebu by some studies)

It was similar in size to the modern aardwolf, standing about 50cm tall at the shoulder (~1’8″) – but it had proportionally longer legs, giving it a build convergently similar to the present-day maned wolf. Despite these long limbs it wasn’t a fast runner, with its joint anatomy instead suggesting it was adapted for efficient walking, pouncing on prey, and looking over the tall grasses of its savanna woodland habitat.

Polysacos

Polysacos vickersianum was a marine mollusc that lived during the early Carboniferous, around 345 million years ago, in what is now Indiana, USA.

It was part of a group known as multiplacophorans, which are usually considered to be close relatives of modern chitons — but may instead represent a much earlier branch of the aculiferan lineage that convergently evolved chiton-like anatomical features.

About 2.5cm long (~1″), Polysacos had seventeen shell plates surrounded by a fringe of long spines with concave upper surfaces. Like the modern chitons it resembled it was probably a grazer that scraped up algae from hard rocky surfaces.

Eons Roundup 16

I keep forgetting I still have unposted PBS Eons work, so let’s have a little bit more of that this week:

An illustration of the extinct metatherian mammal Wamradolops, a small mouse-like animal, shown clinging to a twig. — Wamradolops tsullodon

An illustration of the extinct marsupial Perulestes, a small possum-like animal, shown in a standing pose. — Wamradolops tsullodon

• The polydolopimorphian metatherian Wamradolops and the paucituberculatan marsupial Perulestes from “When the Amazon Flowed Backwards”

Beneziphius

Beneziphius cetariensis was an early beaked whale that lived off the coast of what is now the northwest Iberian peninsula.

It’s only known from a partial skull that was fished up by bottom trawling nets from the seafloor, so its exact age isn’t known, but based on related species it’s estimated to date to somewhere between the mid-Miocene and early Pliocene, around 13-5 million years ago.

About 4m long (~13′), it had a fairly short narrow snout and was functionally toothless, with evidence of only small vestigial teeth that would have been fully embedded in its gums. Males of this species probably had a pair of tusk-like “battle teeth” at the tip of their lower jaw, similar to some other beaked whales, which would have been used in fights against each other.

The back of Beneziphius’ skull was also proportionally tall, and although not as elaborate as some other fossil species this may still have functioned like “internal antlers” — display structures visible only via echolocation.

Eoraptor

It’s Moon Day, so let’s look at a dinosaur from the moon!

…Well, not literally. But Eoraptor lunensis‘ name means “dawn thief from the moon”, in reference to it being discovered in the Valle de la Luna (Valley of the Moon) of Ischigualasto Provincial Park, Argentina.

Living during the Late Triassic, around 231-229 million years ago, Eoraptor was one of the earliest known of all dinosaurs. Originally classified as an early theropod, it’s now thought to actually be a very early offshoot of the sauropodomorph lineage, closely related to other South American forms like Buriolestes and Pampadromeus.

It measured around 1.2m long (~4′), with leg proportions that indicate it was a fast runner. Its jaws contained both leaf-shaped and serrated pointed teeth, suggesting it may have been an opportunistic omnivore, feeding mainly on plant matter but occasionally supplementing its diet with smaller prey.

Unlike later dinosaurs it also still had vestigial palatal teeth on the roof of its mouth.

Eoraptor would have lived in a warm humid climate alongside several other early dinosaur species such as Herrerasaurus and Eodromaeus — but this was at a time before the dinosaurs had become the dominant terrestrial vertebrates, so other animals like rhynchosaurs, aetosaurs, rauisuchians, cynodonts and dicynodonts were also very abundant in the Ischigualasto ecosystem.