Weird Heads Month #01

It’s been a whole four years since Weird Backs Month, so we’re long overdue for a companion series:

Weird Heads Month!

Ever since heads first evolved as a defined body part, over 500 million years ago, evolution has been experimenting with them. There are many modern examples of animals that have modified parts of their heads and faces in a variety of strange-looking ways – elephants, deer, narwhals, hornbills, sawfish, bats, stalk-eyed flies, hammerheads, barreleyes, and star-nosed moles, to name only a few – and species in the fossil record were just as diverse and weird.

So let’s start off with…


Weird Heads Month #01: Wacky Flying Headgear

One of the most immediately recognizable examples of extinct animals with strange head structures are the pterosaurs, almost always depicted in pop culture with a large Pteranodon-like head crest.

But that wasn’t anywhere near as weird as pterosaur crests got.

Nyctosaurus gracilis here had an absolutely ridiculous elaborate crest, sporting an enormous antler-like structure on the back of its skull that grew to lengths longer than its own body.

Living around the Western Interior Seaway of the Midwestern United States during the Late Cretaceous, around 85 million years ago, it was a fairly small pterosaur standing about 40cm tall without the crest (1’4″) and with a 2m wingspan (6’6″). Its wings were long and narrow, and had completely lost the three small clawed fingers seen on other pterosaurs, suggesting it may have been less capable of moving around on the ground. It’s thought to have been a specialized soaring flier that spent most of its life on the wing at sea, much like a modern albatross.

Made up of two long thin spars arising from a common base, Nyctosaurus‘ crest has sometimes been reconstructed with a large sail-like membrane of skin – but since there’s no evidence at all of soft-tissue attachment on the bones, this seems unlikely. Juveniles were crestless, with only fully mature adults developing their spectacular headgear, so it was probably some sort of display structure.

It’s also not clear whether there was any sexual dimorphism in Nyctosaurus, since well-preserved skulls with intact crests are incredibly rare. But as with most other crested pterosaurs it’s likely that all mature individuals had crests, just with a difference in size and shape between sexes.

Cryodrakon

Fragmentary fossils of huge azhdarchid pterosaurs have been found in Canada since the early 1970s, and for a long time they were assumed to belong to Quetzalcoatlus. But more recently these remains were re-examined and shown to actually represent an entirely new genus and species.

Cryodrakon boreas – an excellent name meaning “icy dragon of the north wind” – was officially described in late 2019. With a wingspan of around 10m (32’10”) it was similar in size to its close relative Quetzalcoatlus, but it dates to about 10 million years earlier making it one of the oldest azhdarchids ever found in North America.

It lived about 76 million years ago in Alberta, with its fossils coming from the Dinosaur Park Formation, an area that at the time would have been a coastal plain near the northern parts of the Western Interior Seaway. Despite Alberta being located somewhat closer to the Arctic Circle than it is today, the climate was warm-temperate and temperatures rarely dipped below freezing, with short nights in the summers and only a few hours of daylight in the winters.

Like other azhdarchids Cryodrakon would have spent a lot of its time on all fours on the ground. While moving like that it would have been almost 5m tall (16’5″), similar in size to a modern giraffe, stalking smaller animals and eating whatever it could catch and fit into its mouth.

Ferrodraco

Fossils of pterosaurs are already rather rare due to their fragile hollow bones — and they’re especially scarce in Australia, with only a handful of fragments known.

But recently a more complete one was discovered in central-western Queensland.

Ferrodraco lentoni (“Lenton‘s iron dragon”) is named after the ironstone that the fossils were found in, and while it’s known only from a partial skull, some pieces of its neck and wings, and various teeth, it’s still by far the best pterosaur specimen ever found in Australia.

Living during the mid-Cretaceous, somewhere between 94 and 90 million years ago, it had a 4m wingspan (~13′) and was also one of the very last of its kind. It was a member of the ornithocheirids, a group characterized by rounded crests at the tips of their long toothy jaws, which were previously thought to have all gone extinct by that time.

Many of Australia’s Cretaceous animals were close relatives of those found in South America, due to an earlier land connection via Antarctica, but surprisingly Ferrodraco wasn’t particularly closely related to any South American ornithocheirids. Instead it seems to have been part of a lineage known from halfway around the world in Europe, suggesting that these pterosaurs were capable of crossing long distances over oceans to disperse between continents.

Island Weirdness #09 – Hatzegopteryx thambema

There are no big theropod dinosaurs known from the end-Cretaceous Hațeg Island ecosystem, but that doesn’t mean there weren’t any large carnivores at all.

The apex predator niche here instead seems to have been occupied by Hatzegopteryx, an enormous azhdarchid pterosaur. Standing up to 4.5m tall (14’9″) when on the ground, and with an estimated wingspan rivaling Quetzalcoatlus (~11m / 36′), it was one of the largest animals to ever fly – although like other azhdarchids it probably actually spent most of its time stalking around quadrupedally on the ground eating whatever it could fit into its mouth.

Its neck was shorter and chunkier than most other azhdarchids, and its skull was wider and more massively built. The walls of its hollow bones were also unusually thick and reinforced for a pterosaur, so much so that they were initially mistaken for those of a theropod instead.

Fossils of Hatzegopteryx are very fragmentary, however, so its full appearance and the specifics of its diet are still uncertain. But it would have probably been able to tackle much larger prey than other azhdarchids, possibly capable of using its sturdy beak to bludgeon or stab anything too big to pick up and swallow whole in a similar manner to modern marabou storks.

Cycnorhamphus

Cycnorhamphus suevicus, a pterosaur from the Late Jurassic of Germany and France (~150-145 mya).

It had a wingspan of about 1.3m (4′3″), and was originally thought to look similar to Pterodactylus with long straight jaws – but a well-preserved fossil nicknamed “the Painten Pelican” revealed its snout was actually much more oddly-shaped.

“Painten Pelican mount” by Mike Steele | CC BY 2.0 | cropped from original

It turns out Cycnorhamphus’s jaws arced outwards, creating an opening that seems to have become more pronounced as individuals reached adulthood. Soft-tissue impressions in the fossil also show some sort of stiff “flanges” on each side of the upper jaws, covering the gap and giving it a sort of bulldog-like appearance.

The function of this jaw structure is unknown for certain, but it’s been speculated to be a specialization for cracking open hard-shelled prey like molluscs.

Caelestiventus

Caelestiventus hanseni, a pterosaur from the Late Triassic of Utah, USA. Living about 208-210 million years ago, it was very closely related to Dimorphodon – but unlike its younger coastal-dwelling relative it instead lived in a desert environment made up of a massive sand dune sea with occasional interdunal lakes.

It’s the earliest known example of a desert pterosaur, over 60 million years older than other examples, suggesting that even fairly early in their evolutionary history these flying animals had already adapted to a much wider range of habitats than previously thought.

Although only known from a partial skull and a single wing bone, it was probably one of the largest Triassic pterosaurs with a wingspan of over 1.5m (4′11″). It had a “keel” on its lower jaw that may have supported a soft-tissue crest or a pelican-like throat pouch, and there were several different types of teeth in its mouth – large pointed fangs at the front, “leaf-shaped” blades further back in its upper jaw, and numerous much smaller teeth along its lower jaw.

The skull roof also preserved the impression of Caelestiventusbrain shape, showing that it had very well-developed vision but a poor sense of smell.