paleoart – Page 43 – Nix Illustration

Kulindroplax

Kulindroplax perissokomos, a mollusc from the mid-Silurian of England (~428-423 mya).

About 4cm long (1.6″), it had a wormlike body covered in spicules (tiny spines) which suggests it was a member of the aplacophoran molluscs – but it also had a row of seven larger shells along its back resembling those of chitons.

Modern aplacophorans are all shell-less and were traditionally thought to be a very early branch of the mollusc lineage that retained a “primitive” ancestral body plan. More recently, however, a combination of genetic evidence and fossil discoveries of animals like Kulindroplax have revealed that they’re actually close relatives of the chitons and instead lost their shells much more recently during the course of their evolution.

Qianzhousaurus

Qianzhousaurus sinensis, a tyrannosaur from the Late Cretaceous of southern China (~72-66 mya). Measuring about 9m long (29′6″) it had an unusually long and slender snout for a tyrannosaur, leading to its nickname of “Pinocchio rex”.

The only other known long-snouted tyrannosaur was the closely related Alioramus from Mongolia – but since only juveniles of that genus have been found so far, it’s also possible that Qianzhousaurus was actually just a fully-grown species of Alioramus.

Anomalochelys

Anomalochelys angulata, a terrestrial turtle from the mid-Cretaceous of Hokkaido, Japan (~100-94 mya).

Measuring around 60cm long (2′), it had a pair of large forward-facing horn-like spikes at the front of its shell – the function of which isn’t clear, but they may have been useful for defense if it was incapable of fully retracting its head into its shell.

It was part of a family of turtles from Asia and North America known as nanhsiungchelyids, a group that adapted to live fully on land and ended up convergently closely resembling modern tortoises. Other members of this group included the larger Nanhsiungchelys (which was also recently found to have possessed “horns” on its shell!) and the very flat Basilemys.

They were also a rare example of a turtle family that didn’t survive through the end-Cretaceous mass extinction, with no known remains from the Cenozoic.

Eons Roundup

This year I’ve been lucky enough to have some of my work featured in several PBS Eons videos – and I even recently got the opportunity to do some custom images for them! Since I didn’t show any of these off at the time, here they are now:

The basal temnospondyl amphibian Iberospondylus, from “When Giant Amphibians Reigned”
https://www.youtube.com/watch?v=rGthtRZl8B0

The flying paleognath bird Lithornis, from “When Birds Stopped Flying”
https://www.youtube.com/watch?v=M3h05ajJw0o

The ground sloth Nematherium, from “How Sloths Went From the Seas to the Trees”
https://www.youtube.com/watch?v=pt9tBtQoAHo

Happy new year, everybody!

Sanctacaris

Nicknamed “Santa Claws”, Sanctacaris uncata was a marine arthropod from the Middle Cambrian (~505 mya) Burgess Shale deposits of Canada. Its exact evolutionary relationships are unclear, but it’s thought to have been very closely related to or part of an early branch of the chelicerates – the lineage that includes modern arachnids and horseshoe crabs.

Measuring up to about 9cm long (3.5″), it had forward-facing eyes and five pairs of grasping appendages on the underside of its head, adaptations that suggest it was an active predator convergently similar to anomalocaridids. It probably swam around grabbing onto whatever small prey items it could catch, trapping them in its “limb basket” while it ate them.

Peltephilus

Peltephilus ferox, an armadillo from the Early Miocene of Argentina (~17-16 mya) that was similar in size to a large dog, probably around 1.5m long (5′). It had less solid armor than its modern relatives, with its bony osteoderms being arranged more like chain mail, loosely connected to each other and slightly overlapping, creating a much more flexible body covering.

Its most unusual features were the horns on its snout, convergently resembling the later horned gophers of North America. But unlike other mammals Peltephilus‘ horns were actually modified plates of its face armor, enlarged pointed osteoderms that were only connected to its skull by soft tissue membranes – meaning that after death they tended to fall off, and the exact number and position of them is still a little uncertain.

Its unusually broad snout and large teeth were originally interpreted as evidence of it being an active carnivore, but more recent studies of its anatomy have suggested that it was much more likely to have been a herbivorous or omnivorous digger, mainly feeding on underground plant matter like roots and tubers.

Ichthyosaur Blubber

In early 2017 evidence of blubber was found in plesiosaurs, indicating that they were probably much more chubby than they’re usually reconstructed, and now in late 2018 it’s been found in an ichthyosaur, too!

Living during the Early Jurassic (~183-179 mya) in the shallow seas that covered most of Europe at the time, Stenopterygius was an average-sized ichthyosaur growing up to about 4m in length (13′). A fossil found in Germany has some incredibly good soft-tissue preservation, showing smooth flexible scaleless skin, a layer of insulating blubber very convergently similar to that found in cetaceans, and even evidence of countershaded coloration.

While the confirmation of blubber is amazing, and gives further evidence that ichthyosaurs were warm-blooded, the color preservation might actually be even more interesting. The skin pigmentation is preserved in enough fine detail for branched melanophores to be visible under a microscope – a type of cell associated with the ability to change color. So there’s a possibility that ichthyosaurs could actively darken or lighten their color patterns, for purposes such as better camouflage, UV protection, or temperature regulation.

Falcatus

Falcatus falcatus, a 30cm long (12″) cartilaginous fish from the mid-Carboniferous of Montana, USA (~326-318 mya).

Although it looked very shark-like it was actually much more closely related to modern chimaeras, and its most distinctive feature was the forward-pointing “unicorn horn” spine just behind its head – a sexually dimorphic structure formed from a highly modified dorsal fin, found only on mature males.

The spine’s function is unknown for certain, but it may have been a sort of clasper involved in courtship and mating, since one fossil seems to preserve a female in the act of biting onto it. Some of its close relatives like Damocles and Stethacanthus also had similarly weird dorsal fins, so whatever these fish were actually doing with these structures it must have been a fairly successful strategy.

Falcatus lived out in the open ocean, with proportionally big eyes giving it good vision in deep dark water, and its large symmetrical tail fin suggests it was a fast maneuverable swimmer that actively chased after small prey. Numerous fossils have been found together, which may also indicate schooling behavior.

Although definite fossils of falcatids are only known from the Carboniferous, recently there’s been some possible evidence of them surviving for much much longer. A few isolated fossil teeth from Europe suggest that some of these fish may have persisted for at least another 180 million years into the Early Cretaceous, living in isolated deep water refugia environments in a similar situation to the modern coelacanth – making them fossils of what would have been “living fossils” at the time!

Lisowicia

Dicynodonts were a group of herbivorous animals with toothless beaks and protruding tusks, part of the synapsid lineage and much closer related to mammals than to reptiles. They were some of the most successful and widespread land vertebrates from the Late Permian to the Middle Triassic, with one genus even briefly taking over the world in the aftermath of the End-Permian mass extinction event.

And it turns out some of them got very big.

Fossils of a surprisingly large dicynodont were first reported in 2008, but it wasn’t until just recently (in late 2018) that this giant creature was finally given an official name – Lisowicia bojani.

Close in size to a modern elephant, at around 2.6m tall (8′6″) and 4.5m long (14′9″), it was by far the largest known example of its kind to have ever lived. And while most other dicynodonts had upright hindlimbs and sprawling forelimbs, Lisowicia seems to have developed a fully upright posture much more similar to that of quadrupedal dinosaurs and modern mammals.

It was also one of the very last of its kind, living during the Late Triassic of Poland, about 208 million years ago (although there was a possible later survivor in Australia). This was around the same time that early sauropod dinosaurs were likewise first starting to experiment with gigantism, suggesting that both groups were convergently evolving to exploit newly-available ecological niches.

Enaliarctos

Enaliarctos mealsi, an early seal from the Late Oligocene and Early Miocene of California, USA (~23-20 mya).

Measuring about 1.5m long (5′), it was a transitional form between modern seals and their more otter-like ancestors. It was well-adapted for swimming with a flexible spine and flipper-like limbs, but unlike most modern pinnipeds it probably used both its front and hind flippers for propulsion.

Its teeth also still resembled those of terrestrial carnivores, with slicing carnassials at the back of its jaws. This suggests that it had to drag larger prey items back to shore in order to tear them apart and eat them, similar to the behavior of modern otters.