Nix Illustration – Page 71 – Paleontology and science illustration

Eucritta

Eucritta melanolimnetes, an amphibian-like creature from the Early Carboniferous of Scotland (~335 mya). About 25cm long (10″), it had a mixture of anatomical characteristics similar to baphetid stem-tetrapods, temnospondyls, and reptile-like amphibians, making its exact classification difficult. It’s currently considered to be a close relative of both the baphetids and Crassigyrinus, and it was probably close in appearance to what the common ancestor of all later tetrapods would have looked like.

Its name means “true creature from the black lagoon”, in homage to the 1954 monster movie.

Anteosaurus

Anteosaurus magnificus, a dinocephalian from the Middle Permian of South Africa (~266-260 mya). Known from several skulls and fragments of the rest of the skeleton, it was one of the largest carnivorous non-mammalian synapsids with an estimated body length of at least 5m (16′4″).

It had patches of thickened bone above its eyes forming a pair of short “horns”, as well as heavily reinforced areas around its skull roof and the sides of its lower jaw. These were probably used for head-butting behaviors, and similar adaptations are seen in other groups of dinocephalians.

The front part of its mouth was also prominently upturned, and it had enlarged “sabretooth” fangs – although these features are covered by lips in my reconstruction.

The Francevillian Biota

Life seems to have existed on Earth for over 4 billion years, but for much of that time it was primarily microscopic. And although multicellularity is known to have independently evolved multiple times, large complex forms didn’t really get started until around 600 million years ago, with the strange Ediacarans being some of the most famous early examples.

But that may not have been the first time such an evolutionary experiment happened.

A collection of fossils discovered near the city of Franceville in Gabon appear to represent an even earlier example of large multicellular life. Known as the “Francevillian biota” or “Gabonionta”, these fossils are over three times older then the Ediacarans, dating to a staggering 2.1 billion years ago during the Paleoproterozoic Era.

Over 400 specimens have been collected, representing a variety of different forms — including discs with ruffled edges, rods, rounded clusters of blobs, and elongated shapes that are sometimes attached to long “strings of beads” — with the largest reaching lengths of about 17cm (6.5”). Their age places them somewhere around the origin point of the earliest eukaryotes, and they may represent a completely unique kingdom of life unlike anything alive today.

These organisms’ appearance in the fossil record came shortly after the Great Oxygenation Event, suggesting the evolutionary development of large complex bodies is directly linked to the amount of available oxygen for aerobic respiration. Later, atmospheric oxygen dropped again, and the Francevillian biota disappeared into extinction, leaving us with only these mysterious fossils hinting at a surprisingly diverse and alien-looking period in life’s deep past.

Potanichthys

Potanichthys xingyiensis, a fish from the Middle Triassic of China, living around 235-242 million years ago.Measuring about 15cm long (6″), it was one of the oldest known fish capable of aerial gliding – possessing a “four-winged” body plan with enlarged pectoral and pelvic fins, and an asymmetrical tail with a long lower lobe. It was also almost completely scale-less, which may have helped to reduce drag and make it more aerodynamic.

Despite the similar appearance it had no close relation to modern flyingfishes, and was instead a result of convergent evolution in a completely different lineage of the ray-finned fishes.

Inermorostrum

Inermorostrum xenops, a recently-named ancient cetacean!

Living about 30 million years ago in shallow coastal waters around the southeast USA, in what is now South Carolina, it was a member of one of the very earliest groups of toothed whales known as the xenorophids. Although only very distantly related to modern forms, xenorophids show evidence of being able to echolocate, suggesting the ability was probably ancestral to all toothed whales.

Estimated to have measured about 1m long (3′3″), Inermorostrum had a very short downturned snout and was completely toothless – specialized adaptations for suction feeding on small soft-bodied creatures on the seafloor.

Unusually for a toothed whale it also had proportionally large infraorbital foramina, openings in the bones of its snout for blood vessels and nerves to pass through. This suggests the presence of well-developed fleshy lips and possibly whiskers (as illustrated here), or maybe even an electroreceptive sense similar to some modern dolphins.

Ceratopsian Month #31 – Triceratops horridus

Of course we’re ending this month with the most famous of the ceratopsians, the dinosaur superstar Triceratops (“three-horned face”).

Dating to the very end of the Cretaceous, between 68 and 66 million years ago, it was the most common ceratopsid in North America at the time, ranging from Alberta, Canada down to Colorado, USA. Two different species are currently recognized within the genus – T. horridus in the older part of that time range, and T. prorsus in the younger rock layers.

It was one of the very largest ceratopsians, with the biggest individuals reaching sizes of about 7.9-9m (26’-29’6”). Many fossil remains have been found, representing growth stages from juveniles to adults (with Torosaurus speculated to represent the most fully mature individuals), and a lot of variation in exact horn and frill shape is seen between different skulls. One specimen nicknamed “Yoshi’s trike” had some of the longest brow horns of any ceratopsid, with the bony cores alone measuring 1.15m long (3′9″).

Unusually for a chasmosaur, it had a very short and solid frill with no weight-reducing holes, suggesting the structure served a much more defensive role than in other ceratopsids. Damage to the frill bones in some specimens appears to have been caused by other Triceratops, giving support to the popular depiction of these dinosaurs locking horns in fights.

Tooth-marks from the equally-famous Tyrannosaurus have also been found on Triceratops bones. Not all of these predator-prey encounters were fatal, however, with some specimens showing evidence of healing around the damaged areas.

Fossilized skin impressions show that Triceratops was scaly – but with scales unlike those of any other known dinosaur, showing large polygonal scales interspersed with even bigger knobbly scales with odd “nipple-shaped” conical projections in their centers. It’s possible that the “nipples” may have supported larger structures (as I’ve illustrated above), but unfortunately no official scientific description of this skin has been published yet and details about it are vague.

And with this final entry, here’s the chasmosaur evolutionary tree:

Ceratopsian Month #30 – Torosaurus latus

Torosaurus (“perforated lizard”) was a particularly widespread member of the Triceratopsini, found across western North America. Fossils are known from Canada all the way down to New Mexico and Texas in the southern regions of the USA, although the southernmost specimens represent a second species within the genus, T. utahensis.

Living about 68-66 million years ago, it was one of the largest ceratopsids, reaching body lengths of around 7.5m (24’7″). The size and shape of its three horns varied between individuals, from short and straight to much longer and curving forwards.

It had one of the longest skulls of any known land animal, with some specimens’ heads measuring at least 2.5m long (8′2″). Around half of that length consisted solely of its frill, the shape of which was also quite variable – some were very flat while others curved upwards, and the top edge could be either rounded, straight, or have a “heart-shaped” notch.

In 2010 a study was published by John Scannella and Jack Horner, hypothesizing that Torosaurus wasn’t a unique genus and was actually the fully mature form of Triceratops. While poor media reporting briefly sent the internet into a panic about Triceratops “never existing”, further studies by other paleontologists have failed to come up with the same results, and the debate doesn’t seem to have come to any overall consensus yet.

Ceratopsian Month #29 – Regaliceratops peterhewsi

The Triceratopsini branch of the chasmosaurs first split off somewhere around 75 million years ago, with Titanoceratops being the earliest known member. But they don’t seem to have really diversified until several million years later, towards the very end of the Cretaceous 70-68 million years ago, around the time the centrosaurs had already mostly disappeared.

Regaliceratops (“royal horned face”) dates to about 68-67 million years ago, and is estimated to have measured around 5m long (16’4″). Known from a single near-complete skull discovered in Alberta, Canada, the fossil specimen was nicknamed “Hellboy” for both its stubby brow horns and the immense difficulty of removing it from the surrounding rock.

It had highly unusual ornamentation for a chasmosaur – a long nose horn, short brow horns, and large crown-like spikes ringing its relatively short frill – convergently resembling the sort of arrangement seen in many centrosaurs.

Ceratopsian Month #28 – Vagaceratops irvinensis

Vagaceratops (“wandering horned face”) was originally thought to be a species of Chasmosaurus, but was separated out into its own genus in 2010 after new studies suggested it was much more closely related to Kosmoceratops.

Measuring around 5m long (16’4”), it lived about 75 million years ago in Alberta, Canada – much farther north than its Utahn relative, inspiring its “wandering” genus name. It had a short nose horn, and brow horns reduced down to low bosses, along with a distinctive squared-off frill topped with a row of forward-curving spikes.

Ceratopsid forelimb posture has been a long-standing puzzle in paleontology. While the hindlimbs were clearly held straight under the body, the bones of the forelimbs are a lot more ambiguous, and various different arrangements have been proposed over the years from straight to heavily sprawled and lizard-like.

While the fully sprawled position mostly fell out of favor during the dinosaur renaissance, debate continued about whether ceratopsids had a fully straight forelimb posture or some sort of in-between arrangement with the elbows slightly bent out to the sides. In 2007, digital scans of Vagaceratops’ forelimb bones were used to model how it could have walked, suggesting the best fit was in fact the intermediate position.

Ceratopsian Month #27 – Kosmoceratops richardsoni

Kosmoceratops (“ornamented horned face”) was discovered in Utah, USA, and had one of the most ornate skulls of any known dinosaur.

Living about about 75 million years ago, it’s known from a partial skeleton and an almost complete skull and is estimated to have measured around 5m long (16’4”).

Its frill was relatively short and wide for a chasmosaur, topped with a “fringe” of eight long folded-over spikes and a pair of sideways-curving hooks. Its brow horns curved sideways, and its nose horn was thin and flattened into a blade-like shape.

Overall it had a total of fifteen large horns and spikes – ten big frill spikes, two brow horns, a nose horn, and two cheek spikes – along with sixteen additional scallops along the sides of its frill.