Lobodiscus

Trilobozoans (also known as triradialomorphs) are some of the more enigmatic members of the Ediacaran biota. In the past their unique three-way-symmetrical body plan was interpreted as linking them to groups like sponges, cnidarians, or echinoderms, but currently they’re considered to be their own weird little phylum with uncertain evolutionary affinities, classified no more specifically than “probably some sort of early eumetazoan animal“.

Lobodiscus tribrachialis is a newly-described member of this mysterious lineage. It lived in warm shallow marine waters covering what is now Southwestern China, and with an age of around 546 million years it’s currently the youngest known trilobozoan, extending the group’s time range by several million years.

About 3.7cm in diameter (~1.5″), it had the characteristic trilobozoan disc-shaped shield-like body, with a central depression surrounded by three triradially-symmetric lobes with branching ridges and grooves.

Its body would have been soft but fairly rigid, and it’s not clear if it was capable of moving over the seafloor or if it had a more static lifestyle. Like its relative Tribrachidium it was probably a filter feeder, with the grooves on its surface directing water flow towards the central depression – and this surface ornamentation may also have been covered with cilia that actively caught and transported suspended food particles.

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Jiangxichelys neimongolensis

Jiangxichelys neimongolensis was a terrestrial turtle that was part of an extinct group known as nanhsiungchelyids, whose closest living relatives today are the aquatic softshell turtles.

(This species was previously known as “Zangerlia” neimongolensis, but has since been moved into the genus Jiangxichelys instead.)

It lived towards the end of the Cretaceous, about 75-71 million years ago, in what is now the Gobi Desert – which at the time was more of a semi-arid climate with both rivers and sand dunes.

Its 60cm long (~2′) carapace had a long wide shape that made it appear rather flattened from the front, but not to quite as much an extreme as its larger American cousin Basilemys.

Several fairly well-preserved specimens have been found that appear to have been buried alive, probably either engulfed by sudden sandstorms or trapped in collapsing burrows. This has preserved some anatomical details previously unknown in nanhsiungchelyids, such as the pattern of scales on top of the head and the presence of large bony osteoderms on the underside of the front toes, which may have aided with traction on loose sandy ground.

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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.

Further reading under the cut:

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