Weird Heads Month #21: Honking Hadrosaurs

The ceratopsians and pachycephalosaurs weren’t the only ornithischian dinosaurs to do weird things with their skulls.

The hadrosaurs are commonly referred to as “duck-bills” (despite how their beaks weren’t actually duck-like at all), and are famous for the elaborate crests seen on some of the group’s members, with shapes ranging from lobes to helmets to hatchets to spikes – and even some of the apparently crestless species are now known to have sported fleshy combs instead of the bony structures seen in their relatives.

But by far the most recognizable of the crested hadrosaurs is Parasaurolophus walkeri, with its long curved backwards-pointing tubular crest.

This particular species was mid-sized for the genus, growing up to around 10m long (32’10”) and is known from Western North America during the Late Cretaceous, about 76-73 million years ago.

Its crest was intermediate in size and shape between the other two known species. The larger Parasaurolophus tubicen had a longer and slightly straighter crest, while the smaller Parasaurolophus cyrtocristatus had a shorter more strongly curved one. Juveniles developed these crests as they matured, starting off with much smaller bumps on their snouts that gradually grew backwards and upwards.

Some hadrosaur crests were purely for visual display, but in the lambeosaurine lineage that Parasaurolophus belonged to they also incorporated complex looping nasal passages that were probably used as resonating chambers, allowing each species to make a unique-sounding loud bellowing call to communicate with each other.

There are also rumors of a currently-undescribed specimen of Parasaurolpphus that has preserved soft tissue around its crest, possibly a keratinous covering or skin flaps that made it appear even larger and more flamboyant in life than the underlying bone. So I’ve given this reconstruction a speculative structure like that, along with hoof-like claws on its hands similar to those recently revealed for Edmontosaurus.

Weird Heads Month #18: Boneheaded Dinosaurs

Pachycephalosaurs are highly recognizable dinosaurs with their thick spiky skulls, and it’s not hugely surprising that they were the evolutionary cousins of the equally weird-headed ceratopsians.

Much like their frilled relatives they had beaks at the tips of their snouts and large gut cavities for digesting plant matter, but they also had surprisingly sharp theropod-like teeth in front of their more standard herbivore teeth further back – suggesting they may also have been opportunistic omnivores, occasionally snacking on carrion or small animals similarly to modern pigs or bears.

Their striking-looking dome heads were probably used for combat, headbutting or flank-butting each other, and many fossil skulls show evidence of injuries that would have been caused by that sort of behavior.

The eponymous Pachycephalosaurus wyomingensis lived in North America right at the end of the Cretaceous, about 70-66 million years ago. It was one of the largest of its kind, reaching lengths of around 4.5m (14’9″), and was characterized by a large bony dome-head surrounded by small blunt spikes.

But it turns out that was probably only what it looked like as a fully mature adult.

Recent discoveries of juvenile Pachycephalosaurus skulls confirmed a hypothesis proposed a few years earlier: these dinosaurs changed appearance drastically as they grew up, and younger individuals had been mistaken for separate species. They started off with domeless flat heads, bristling with long spikes (a form previously named Dracorex hogwartsia) then as they matured their domes began to grow (previously Stygimoloch spinifer) and by full maturity they had big domes with the spikes shrunk down to smaller stubbier knobs (the classic Pachycephalosaurus look).

This particular reconstruction depicts a Stygimoloch-like subadult individual, not quite fully mature and still sporting some longer spikes.

Weird Heads Month #14: Horns and Frills

We can’t go through this month without having an appearance from the most famous group of weird-headed dinosaurs: the ceratopsids!

Their distinctive-looking skulls were highly modified from those of their ancestors, with large bony frills extending from the back of their heads, various elaborate horns and spikes, enormous nasal cavities, large hooked beaks at the front of their snouts, and rows of slicing teeth further back.

And while typically depicted as purely herbivorous, ceratopsids’ powerful parrot-like beaks and lack of grinding teeth suggest they may actually have been somewhat more omnivorous – the Cretaceous equivalent of pigs – still feeding mainly on plant matter but also munching on carrion and opportunistically eating smaller animals when they got the chance.

Machairoceratops cronusi here lived during the late Cretaceous of Utah, USA, about 77 million years ago. Only one partial skull has ever been found belonging to an individual about 4.5m long (14’9″), but it wasn’t fully grown and so probably reached slightly larger sizes.

It had two long spikes at the top of its frill, similar to its close relative Diabloceratops but curving dramatically forward and downwards above its face. Whether they were purely for display or used in horn-locking shoving matches is unknown, but either way it was a unique arrangement compared to all other known ceratopsids.

Weird Heads Month #12: Double-Crested Dinosaurs

Dilophosaurus wetherilli is a fairly recognizable dinosaur thanks to its memorable appearance in the Jurassic Park franchise – but unfortunately that also means the popular image of it is completely wrong.

Rather than a small frill-necked venom-spitting creature, this early theropod was actually rather large, reaching around 7m long (~23′), and along with its distinctive double crests it also had a narrow snout with large teeth and a distinctive notch at the front of its lower jaw.

It lived in North America during the early Jurassic, about 196-183 million years ago, and while it wasn’t venomous its notched jaws were probably capable of delivering powerful bites to small struggling prey, much like the similar-looking ornithosuchids in the Triassic. Some structural similarities to the skulls of spinosaurids suggest it may have primarily eaten fish.

Its two bony crests were probably used for visual display, with juveniles only having small crests that fully developed as they matured. They also may have had a more extensive keratinous covering, so it’s not clear what their actual shape and full extent was in life.

Bambolinetta

Between about 9 and 7 million years ago, the modern regions of Tuscany, Corsica, and Sardinia were once part of a single island in the ancient Mediterranean Sea.

And since evolution often goes in weird directions on isolated islands, it’s no surprise that some unusual species developed there.

One of which was a very odd duck.

A map of the Mediterranean region during the Late Miocene, showing the location of the Tusco-Sardinian island.
From fig 4 in Williams, M. F. (2008). Cranio-dental evidence of a hominin-like hyper-masticatory apparatus in Oreopithecus bambolii. Was the swamp ape a human ancestor?. Bioscience Hypotheses, 1(3), 127-137. https://doi.org/10.1016/j.bihy.2008.04.001

Bambolinetta lignitifila lived during the Late Miocene, about 7.5 million years ago. Known from a single partial skeleton discovered in the mid-1800s, it was initially thought to be a fairly normal dabbling duck and wasn’t properly re-examined until 2014, when its strange features were finally recognized.

It was a medium-sized duck, probably around 50cm long (1’8″), but it had much chunkier wing bones than its relatives, with noticeably shortened forearms – looking much more like the wings of an auk or penguin, and suggesting that it was a similar sort of wing propelled diver. This is incredibly weird for a duck, since every other known diving species uses feet for propulsion instead, and so Bambolinetta may be the only known waterfowl to ever develop this type of underwater locomotion.

It’s not clear whether it was still capable of flying or not. There were few predators in its habitat, so it may well have become completely flightless – and that could also be the reason it later went extinct. Sea levels in the region began to drop around 7 million years ago, reconnecting the Tusco-Sardinian island to the European mainland, and Bambolinetta‘s high level of ecological specialization and its potential island tameness would have given it little defence against an influx of new unfamiliar predators.

Atlasaurus

Sauropod dinosaurs were just generally weird animals, but there’s something… not quite right about Atlasaurus imelakei.

Named after the Atlas Mountains of Morocco where its fossil remains were discovered, Atlasaurus lived during the mid-Jurassic period, around 168-165 million years ago. While it wasn’t the strangestlooking sauropod by any means, compared to other species its body proportions still show a particularly bizarre combination of features, with a slightly bigger head, unusually short neck, and very long slender legs that made up nearly half of its 9m height (29’6″).

It’s sort of the uncanny valley of sauropods. Everything about it is just a tiny bit wrong.

A photograph of an Atlasaurus model. Its been reconstructed very skinny, which only serve to emphasize its weird proportions.
And more shrinkwrapped depictions really don’t help with that. [image source]

Its tall shoulders and sloping back resemble the body plan of brachiosaurids so closely that it was initially thought to be an early member of that group, but more recent studies suggest it may have been part of an earlier evolutionary branch of sauropods known as the turiasaurs – which would mean its brachiosaur-like shape was actually the result of convergent evolution.

But what was it doing with such weird proportions?

…We really don’t know. Other short-necked sauropods seem to have been adapted for feeding on lower vegetation only a couple of meters off the ground, but Atlasaurus’ leggy build would have made it a high browser like the brachiosaurids it was mimicking. Its long legs may also have allowed it to move faster, or given it some advantage navigating over rough terrain, but since no other sauropod ever seemed to evolve this way it must have been doing something particularly unique.

Or perhaps it was just an evolutionary fluke. Maybe part of a lineage that had started adapting to short-necked low browsing, then moved back towards the high browsing niche – and happened to end up lengthening their legs instead of their necks to get the necessary height back.

Palaelodus

The closest living relatives to modern flamingos are, surprisingly, the grebes. But this relationship is especially ancient, with their last common ancestor probably living sometime between the end of the Cretaceous and the early Eocene.

Such an ancestor is thought to have been a highly aquatic swimming bird, more grebe-like than flamingo-like, but there are few fossils of intermediate forms between that and the modern wading flamingos – with the exception of a group known as the palaelodids.

Palaelodus ambiguus here lived about 29-12 million years ago in Europe, from the early Oligocene to the mid-Miocene. It was similar in size to a small flamingo at about 80cm tall (2’7″), but had proportionally shorter legs and appears to have been capable of both wading and swimming in different depths of water, leading to its nickname of “swimming flamingo”.  (Even though modern flamingos do occasionally swim too!)

Its straight pointed beak also suggests it had a much less specialized diet than its modern cousins, probably feeding on small aquatic animals like snails, insect larvae, and fish.

Various other palaelodid species have been found all around the world – even as far as New Zealand – so they seem to have been incredibly common and successful birds during their time. The last definite remains of this group come from the late Miocene, about 7 million years ago, although one Australian fossil may represent a late-surviving relict population that existed until just half a million years ago in the mid-Pleistocene.

Kaijutitan

Originating from Japanese monster movies like Godzilla, the word “kaiju” is now often used to refer to giant creatures in general – and so it was only a matter of time before a huge sauropod dinosaur was named after the concept.

Kaijutitan maui* was a titanosaur living in Argentina during the Late Cretaceous, about 89-86 million years ago. It’s only known from fragmentary remains, so its full size is difficult to estimate, but it was probably somewhere in the region of 20m long (66′). Nowhere close to the largest sauropod, but possibly one of the heaviest since it does seem to have been rather chunkily built, with stout limbs and an estimated weight of 40-60 tonnes (44-66 US tons).

* Not named for the Polynesian hero, apparently, but for the initials of the Museo Argentino Urquiza.

Island Weirdness #59 — Terrestrial Otters & Owls

The Mediterranean island of Crete had very few predators during the Pleistocene, with most being birds of prey. And with the terrestrial carnivore niches in the ecosystem left vacant, it was a semi-aquatic mammal and an owl that ended up taking advantage of that opportunity.

Neither were large enough to threaten the dwarf elephants and hippos, and don’t even seem to have habitually eaten even the smallest of the miniature giant deer. Instead these Cretan predators focused much more on the smaller land vertebrates on the island, preying on birds, shrews, rodents, amphibians, and reptiles.

A stylized illustration of an extinct otter. It has a blunt snout and chunky legs.
Lutrogale cretensis

Lutrogale cretensis (previously known as Isolalutra cretensis) was a close relative of the modern smooth-coated otter. It was about the same size as its living cousin, around 1m long (3’3″), but had stronger jaws and chunkier limbs.

Its skeleton shows features associated with walking and running more than swimming, and it seems that this was something of a “land otter” — still able to swim, but spending most of its time on land similar to the modern small-clawed otter.

Shellfish were likely still the main part of its diet, indicated by its crushing teeth. But it probably also regularly ate whatever small terrestrial vertebrates it could catch, since more aquatic otters are already known to prey on those types on animals when they can.


A stylized illustration of an extinct giant little owl. It has longer legs than its modern relatives, almost resembling a large burrowing owl.
Athene cretensis

Athene cretensis was yet another weird island owl, but this time not a descendant of a Strix or Tyto species. Instead this owl was descended from the Eurasian little owl — except it had become much much larger.

It stood around 60cm tall (2′), over three times bigger than its living relative. Its legs weren’t quite as long as those of the modern burrowing owl, but they were still proportionally much longer than those of little owls and show adaptations for terrestrial movement. Little owls already sometimes chase down prey on foot, and Athene cretensis was probably even more of a ground-based hunter, convergently similar to the Hawaiian stilt-owls and the Cuban terror owls.

Preserved pellets show that it ate small mammals and birds, mainly large mice.

Its wings were still quite large, and it was probably also a good flier — and may even have spread over to some of the Dodecanese islands to the east of Crete, since a wing bone closely resembling that of Athene cretensis has been found on Armathia.

Both of these predators seem to have disappeared around the end of the Pleistocene, at the same time as many of the other native Cretan species about 21,500 years ago. Much like the situation with Candiacervus, this may have been a result of a combination of a rapidly shifting climate and the presence of humans disrupting the already fragile island ecosystem.

Island Weirdness #57 — Cygnus falconeri

The island of Sicily was isolated about 5.3 million years ago when the Mediterranean rapidly refilled. During the next few million years changes in sea level and tectonic uplift allowed repeated colonizations by mainlaind species via the sea strait separating Sicily from Italy, and opened up occasional connections with nearby Malta, resulting in a series of different ecosystems over time.

During the mid-Pleistocene, between about 900,000 and 500,000 years ago, a lack of large land predators on Sicily and Malta allowed a weird mix of endemic species to evolve. Most famous are the tiniest elephants (Palaeoloxodon falconeri), but there were also a couple of giant owls, a small long-legged owl, a giant crane, a big lizard, a giant tortoise, an otter, and giant dormice.

And then there were the swans.

Cygnus falconeri was enormous, at least a third larger than the biggest living swans, at least 1.5m tall (4’11”) — taller than the native elephants, although not nearly as heavy. Its wings were large, with a span of around 3m (9’10”), but at such a hefty size it would have been either a very poor and reluctant flier or functionally flightless.

Its legs were better adapted for walking around on land than for swimming, with shorter toes and possibly reduced webbing. It would have been one of the biggest terrestrial herbivores on Siculo-Malta, probably mainly a grazer but also capable of reaching much higher vegetation than the elephants or tortoises.

It lived alongside another unique swan species, the goose-like dwarf swan Cygnus equitum. Both the giant and dwarf swans probably evolved from the same whooper swan-like ancestor species, but each resulted from separate colonization events — otherwise interbreeding would have probably prevented them from developing such a huge difference in size.

Or an alternative scale comparison to highlight the utter ridiculousness of this island:

A scale comparison between a dwarf elephant and a giant swan. The swan is the taller of the two.
Palaeoloxodon falconeri vs Cygnus falconeri

Between 500,000 and 200,000 years ago multiple sea level fluctuations allowed new species to colonize Siculo-Malta from the mainland, including various large mammalian herbivores and carnivores. With new competition and predators, Cygnus falconeri probably disappeared around the same time as the tiny elephants and most of the other mid-Pleistocene endemic animals.

The dwarf swan, smaller and still a strong flier, may have survived the altered ecosystem for a bit longer, but would have gone extinct during the rapid climate changes at the start of the last glacial period 115,000 years ago.