Month: August 2022

Ornithoprion

The eugeneodonts were a group of cartilaginous fish that convergently resembled sharks but were actually much closer related to modern chimaeras. They had unique “tooth whorls” in their jaws, and the most famous member of the group is probably Helicoprion, whose bizarre buzzsaw-like tooth arrangement was only properly understood within the last decade.

Ornithoprion hertwigi here was one of the first eugeneodonts found with fossilized skull material, and helped with the early understanding of just how their weird jaw anatomy actually worked.

It lived during the Late Carboniferous, about 315-307 million years ago, in a shallow tropical sea that covered what is now southwestern Indiana, USA.

At only around 50cm long (~1’8″) it was one of the smaller eugeneodonts, and along with a small Helicoprion-like tooth whorl it also had a distinctive highly elongated chin. Similar to modern halfbeak fish this structure may have served a sensory function, helping Ornithoprion to detect prey in dark or murky waters.

Jakapil

The thyreophorans were heavily armored ornithischian dinosaurs, with their most famous representatives being the stegosaurs and the ankylosaurs. Earlier members of the group were all small bipedal animals covered in rows of prickly osteoderms, and until now these “primitive” forms were known only from the early-to-mid Jurassic, around 200-165 million years ago.

But now the recent discovery of Jakapil kaniukura is suggesting a lineage of early thyreophorans actually survived for much much longer than previously thought – all the way into the Late Cretaceous, about 97-94 million years ago.

Just 1.5m long (5′), Jakapil lived in what is now southern Argentina, in an ancient desert with a braided river system. It was bipedal, with a short beak, small arms, and a body bristling with spiky armor, and its unusually deep lower jaw and heavily worn teeth indicate it fed on rather tough vegetation that required a lot of chewing to process.

It’s currently only known from somewhat fragmentary remains, so reconstructions of its full appearance are rather speculative and there’s already been some dispute about whether Jakapil actually was a thyreophoran. One proposal is that it shared a lot of anatomical features with early ceratopsians instead, which if true would make it an incredibly weird armored ceratopsian, and also the first definitive member of that group from South America. But the ceratopsian-like features could also just be due to convergent evolution – and a Jakapil-like dinosaur might actually help explain the only other known dubious South American “ceratopsian” Notoceratops, and the similarly-disputed Australian Serendipaceratops.

But whatever it was – late-surviving basal thyreophoran, southern armored ceratopsian, or even a previously unknown lineage of ornithishcians entirely new to science – it’s an exciting and unexpected discovery.

Slavoia

Slavoia darevskii was a lizard that lived in what is now Mongolia and Kazakhstan during the Late Cretaceous, about 85-70 million years ago.

Around 12cm long ~(4.75″), it had a compact skull, small eyes, a short neck, shovel-like hands, an elongated body and slightly reduced hind limbs – all features that indicate it was a burrowing animal, digging tunnels and feeding on underground invertebrates.

Its exact relationships are uncertain, but recent studies have suggested it was an early amphisbaenian, representing a point in the group’s evolution before the full loss of their legs and the development of their extremely long worm-like shape.

Rajasaurus

Abelisaurids were a group of theropod dinosaurs characterized by short snouts, bony ornamentation on their skulls, tiny stiff arms, and stocky legs. Known mostly from the southern continents of Gondwana, they were the dominant predators in these regions and are thought to have been specialized hunters of titanosaurian sauropods.

Rajasaurus narmadensis lived in what is now western India during the Late Cretaceous, about 67 million years ago. Around 7m long (23′), it had very rough-textured thickened bone on the top of its snout, along with a short rounded horn on its forehead that was probably used for display or headbutting behaviors.

India at this time was an isolated island continent located off the east coast of Africa, and Rajasaurus‘ ancestors probably island-hopped across from then-nearby Madagascar – where its closest known relative lived, the very similar-looking Majungasaurus.

Auroralumina

Cnidarians – a group of animals that includes modern corals, sea anemones, sea pens, jellyfish, hydra, and a couple of parasitic forms – are one of the most ancient animal lineages, originating at least 580 million years ago in the Ediacaran period.

Actual identifiable fossils of cnidarians that old are incredibly rare, however, and until now there was only one example – the small polyp-like Haootia from Canada.

But a second definite Ediacaran cnidarian has now been described: Auroralumina attenboroughii.

It was discovered in Charnwood Forest, England, in the very same site where the first recognized Precambrian fossils were found in the 1950s. About 20cm tall (~8″) it dates to around 560 million years ago and was made up of a pair of forking stiff-walled tubes which expanded into wide four-sided goblet-like shapes full of stubby tentacles. These densely-tentacled crowns would have been used to capture tiny planktonic organisms from the water around it, making it the current earliest known example of a predatory animal.

The one known fossil specimen has an incomplete base, so it’s uncertain if this was actually the full life appearance of Auroralumina or if it was even larger with more branches and goblets. And although it was preserved in deep-water sediments, it appears to have originated from much shallower waters, being swept down into the depths during a volcanic eruption.

While it superficially resembled a sea anemone, details of its anatomy suggest it was actually much closer related to medusozoans, having similar traits to the immobile polyp stage of the jellyfish life cycle. Its four-way symmetry and boxy shape may also link it to the enigmatic conulariids.

It’s not clear if it was able to bud off swimming medusa stages like its modern relatives – that might be an evolutionary innovation that came along later – but it at least shows that a basic medusozoan body plan was already in place around 20 million years earlier than previously thought.