Retro vs Modern #04: Archaeopteryx lithographica

Archaeopteryx lithographica was first discovered in the 1860s, still in the early days of our understanding of dinosaurs, and was a timely example of the sort of transitional form first proposed by Charles Darwin only a couple of years earlier. For over a century it was a famous icon of evolution, and has been part of a lot of weird drama over the years – it’s been central to arguments about bird origins, was accused of being a fake, and one specimen even vanished under mysterious circumstances.

1860s-1970s

At the time of its discovery Archaeopteryx was actually fairly quickly accepted as demonstrating an evolutionary link between dinosaurs and birds… but sadly this view wasn’t to last.

In the early 20th century opinion shifted towards birds not being dinosaurs but instead descended from “thecodont” reptiles (what we’d now call early archosaurs and pseudosuchians). And so for a long time Archaeopteryx ended up being depicted as simply the “first bird”, a half-reptile half-avian curiosity.

Reconstructions of it from this time period varied from very good to kind of awkward depending on how much the artist was trying to emphasize its reptilian ancestry, commonly featuring wonky-fingered wings and a scaly lizard-like face. It was also frequently depicted with bright gaudy parrot-like coloration, with a specific yellow-and-blue color scheme becoming a “paleoart meme” so prolific that it would eventually inspire the design of a Pokémon.

2020s

After decades of stagnation the dinosaur-bird link was resurrected in the early 1970s, with the discovery of the bird-like Deinonychus kicking off the Dinosaur Renaissance. Along with the explosion of spectacularly feathered dinosaur fossils from China in the mid-1990s, Archaeopteryx finally began to be properly presented as a feathered dinosaur again.

Continued study of the known Archaeopteryx specimens in the last couple of decades has vastly improved our knowledge of what this animal would have looked like, revealing previously unknown features like the exact plumage arrangement on its wings and legs, and even potentially some details about its coloration.

Living in southern Germany during the Late Jurassic, about 150-148 million years ago, Archaeopteryx inhabited what was then an island archipelago in a shallow tropical sea. It grew to around 50cm long (~1’8″) and was almost entirely covered with pennaceous feathers, externally probably just looking like a long-tailed bird.

It had broad wings, with asymmetrical flight feathers similar to those of modern birds but with more extensive coverts, some of which were probably a matte black color. Its legs also sported long “feather trousers” and a “raptor“-like hyperextensible second toe, and there was a slight forked shape to the tip of its tail.

Arguments have gone back and forth about how well it was actually able to fly, with current thinking being that it made short bursts of active flapping flight a little like a modern pheasant – but since its shoulder joints were less mobile than those of modern birds it must have used a different sort of flight stroke to generate lift.

It’s no longer always considered to have been the “first bird”, or even to have been the direct ancestor of any modern birds. Instead it represents an offshoot lineage of early birds (or very-bird-like dinosaurs) that was just one part of a still-expanding flock of feathery fossil discoveries.

Retro vs Modern #03: Hylaeosaurus armatus

Despite being the third-ever scientifically named dinosaur genus, and being used in the first official definition of dinosaurs as a group, Hylaeosaurus armatus has ended up as a much less well-known name than Iguanodon or even Megalosaurus.

It was also the very first ankylosaur to be discovered, found as a partial skeleton in Southeast England in the early 1830s. Its large bony spikes were quickly recognized as being some sort of defensive armor, initially thought to be arranged in a vertical row along the animal’s back and tail.

1850s

The Victorian Crystal Palace statue of Hylaeosaurus is surprisingly decent for such an early attempt at reconstructing something as weird as an ankylosaur. It gives the impression of a slower and much more lizard-like animal than Iguanodon or Megalosaurus, showing it as a large squat quadruped with hoof-like claws and heavily armored scaly skin, with long spines running along its back and numerous smaller bony bumps over its head and sides.

1860s-1920s

Discoveries of other more complete armored dinosaurs began to give a better picture of what ankylosaurs actually looked like. But although Hylaeosaurus was soon recognized as having had multiple rows of spikes rather than just one, actual reconstructions of it seem to have been scarce during this period – mostly all derivative of a single 1869 image that depicted it as a sort of fat sprawling pinecone-lizard bristling with spikes.

2020s

Still only known from fragmentary material, Hylaeosaurus has remained rather obscure for a long time. In the 21st century it’s started to get a bit more attention, however, with the original specimen being further prepared and examined – and 2020 was Hylaeosaurus’ big year, with both a redescription of the genus being published and it also being featured on a special-edition British 50p coin.

Hylaeosaurus was probably around 4m long (~13′), and lived in southeast England about 140-136 million years ago. It may have also ranged further across Europe, with possible remains known from Germany and some more dubious records from France, Spain, and Romania. Generally classified as an early nodosaurid, most of our modern knowledge of what it would have looked like comes from other discoveries of much better-known ankylosaurian relatives, including some exquisitely well-preserved examples in the last few years like Borealopelta and Zuul.

It would have had a low triangular head, with a toothless beak at the front of its jaws and leaf-shaped teeth further back, and a pair of short horns on the back of its skull behind its eyes. Rows of spiky osteoderm armor ran along is body, with longer curving spines over its shoulders, all covered in thick keratin sheaths that would have made them look even larger in life. Numerous smaller bony nodules in its skin filled in the gaps between the armor, forming a tough protective shield over its entire back. Its short powerful limbs had hoof-like claws, and if it was indeed a nodosaurid its tail would have lacked the famous club of its ankylosaurid cousins.

Based on Borealopelta we even now know a little bit about the potential coloration and patterning of these animals – some of them were reddish-colored, with a countershaded camouflage pattern, darker on top and lighter on the underside.

Retro vs Modern #02: Iguanodon bernissartensis

Named just a year after Megalosaurus, in 1825, Iguanodon has remained a fairly iconic dinosaur ever since.

Discovered in a different region of Southeast England, its fossilized teeth were soon recognized as being similar to those of modern iguanas – but much much larger. Partial skeletal remains were initially reconstructed as belonging to a gigantic herbivorous lizard, with what was thought to be a horn placed on the tip of its nose.

1850s

The Victorian Crystal Palace statues of Iguanodon depicts a more bulky reptile with a nose horn, a toothless beak at at the front of its jaws, scaly skin, thick upright legs and hoof-like claws. Much like the Megalosaurus of the time it’s really not nearly so bad of a reconstruction as it’s often accused of being, showing a surprisingly naturalistic and almost mammal-like interpretation of these animals compared to later portrayals.

Technically the particular “Iguanodon” species at Crystal Palace has more recently been renamed Mantellisaurus atherfieldensis, but it was considered to be Iguanodon at the time so it’s included here anyway.

1880s-1960s

A massive discovery of the remains of nearly 40 Iguanodon individuals in a coal mine in Bernissart, Belgium, revealed the full anatomy of these dinosaurs for the first time. Much more well-preserved and complete than the patchy English material, these larger Iguanodon bernissartensis eventually became the official type species for the whole genus – a standard used to help determine whether similar-looking fossils are Iguanodon or not.

The Bernissart specimens were restored as bipedal animals in an upright kangaroo-like pose, with their tails dragging behind them acting like a tripod to prop them up. What had previously been the single “horn” was finally realized to instead be a thumb spike on each hand, interpreted as a defensive weapon against predators.

This image of Iguanodon persisted for decades, with a giraffe-like long prehensile tongue sometimes also depicted (including a particularly bizarre interpretation of it sticking out through a hole in the lower jaw!).

2020s

The Dinosaur Renaissance in the late 20th century corrected Iguanodon‘s posture to hold its body horizontally, and it was eventually recognized as being capable of both bipedal and quadrupedal movement. Juveniles were found to have walked more on their hindlimbs, while adults spent more time on all fours but were still capable of running bipedally when they needed to.

We now have fossils of Iguanodon from across much of Europe during the Early Cretaceous, about 126-122 million years ago. Our modern view of this animal is a heavily built ornithopod that grew to around 9m long (~30′), with a horse-like head, a large keratinous beak at the front of its jaws, chewing teeth further back, and cheeks covering the sides of its mouth. Its chunky forelimbs each had a large thumb spike, hoof-like claws, and a prehensile grasping pinky finger, while its powerful hindlimbs ended in three-toed vaguely bird-like feet.

Soft tissue preservation discovered in related hadrosaurs suggests it probably also had a very bulky body with a thick heavily muscled neck and tail, and possibly an ornamental “frill” running along its back. Skin impressions show a covering of numerous tiny pebbly scales, generally too small to have been visible from a distance.

Retro vs Modern #01: Megalosaurus bucklandii

It’s time for Retro vs Modern Month!

Every weekday this March we’ll be looking at some examples of how our paleontological understanding and visual depiction of various fossil creatures has evolved over the years.

Starting with…

Retro vs Modern #01: Megalosaurus bucklandii

Fragmentary fossil remains of dinosaurs have been found in Southeast England for hundreds of years, but it wasn’t until the 1820s that they were properly recognized as belonging to an ancient “great lizard” given the name Megalosaurus bucklandii – the very first non-avian dinosaur known to science, almost two decades before the term “dinosaur” would even be created to categorize these extinct animals.

1850s

The Victorian Crystal Palace reconstruction of Megalosaurus is often mocked for its inaccurate bulky appearance, but for its time it was actually an incredibly progressive vision of a predatory dinosaur. It was depicted as an alert, active, bear-like beast with upright muscular limbs, and a humped back based on what later turned out to actually be remains of a different dinosaur species.

1890s-1960s

Discoveries of other large theropod dinosaurs revealed their bipedal posture, and Megalosaurus reconstructions were revised to show an upright kangaroo-like stance. But despite some other early portrayals of active agile dinosaurs, the overall opinion of these animals began to drift during the first half of the 20th century towards sluggish tail-dragging reptiles: depicting them as slow, stupid, cold-blooded, awkward and obsolete evolutionary failures whose extinction had been inevitable.

2020s

Starting in the late 1960s the Dinosaur Renaissance finally began to shift thinking back towards active and warm-blooded dinosaurs, recognizing theropods’ close evolutionary relationship to modern birds and correcting their posture into a horizontal stance with a counterbalancing tail. And while Megalosaurus itself is still only known from fragments, discoveries of more completely preserved relatives like Torvosaurus have given us a much better idea of what it was probably like.

We know know Megalosaurus lived on what at the time was a subtropical island in the shallow western Tethys Sea, about 166 million years ago during the Mid Jurassic. It would have been around 8m long (~26′), with a long narrow snout, and short muscular arms with enlarged meathook-like thumb claws. Its legs and tail would have been fairly thick and bulky, and it may have had a covering of hair-like protofeathers on its body.

Utaurora

Ever since the bizarre anatomy of Opabinia was first recognized in the 1970s, it’s been a persistently unique “weird wonder” of the Cambrian period. Over the decades we’ve figured out that it was an early type of arthropod in an evolutionary position between lobopodians and radiodonts, but this whole time it’s still been sitting there alone as the only known representative of a weird stem-lineage with no other known close relatives.

…Until now!

A fossil from the Wheeler Shale in Utah, USA (~507 million years ago) that was originally thought to be a tiny radiodont has been re-studied, and now we finally have another member of the opabiniid family: Utaurora comosa.

Only about 3cm long (1.2″), Utaurora had 15 pairs of swimming flaps along the sides of its body, and a tail region with a 7-part fan and a pair of serrated spines. Hair-like gill blades covered both its back and the bases of its swimming flaps, and although its head region was poorly preserved it probably had an arrangement of 5 eyes and a long flexible claw-tipped proboscis similar to that of Opabinia.

Its discovery extends both the geographical and temporal known range of opabiniids, and suggests that their continued scarcity in other Cambrian fossil sites compared to other soft-bodied arthropods may simply be because they were just incredibly rare animals in those habitats at the time.

Kogiopsis

Kogiopsis floridana was a physeteroid whale that lived near the coast of the southeastern United States from the mid-Miocene to the early Pliocene, about 14-4 million years ago.

Known just from fossilized lower jaws and teeth, with some teeth up to nearly 13cm long (~5″), its full life appearance and size are uncertain – but it may have been slightly larger than a modern bottlenose dolphin at around 4.5m long (~14’9″). It’s traditionally been considered to be part of the kogiid family, closely related to modern pygmy and dwarf sperm whales, but some studies disagree with that classification and instead place it in the true sperm whale lineage.

It was probably a predator in a similar ecological role to modern orcas, adapted for hunting prey like squid, fish, and smaller marine mammals. But unlike orcas it wouldn’t have been the apex predator of its ecosystem, subject to predation pressure by even larger carnivores like macroraptorial sperm whales and everyone’s favorite ridiculously huge shark – and as a result it probably had a “live fast and die young” lifestyle similar to modern kogiids and other small-to-medium-sized Miocene physeteroids, rapidly maturing and only living to around 20 years old.

I’ve reconstructed Kogiopsis here as a kogiid-like animal, with a similar sort of shark-like head shape and “false gill” markings. In the background a second individual is depicted displaying “inking” behavior, releasing a defensive cloud of reddish-brown fluid from a specialized sac in its colon.

Spinosuchus

Allokotosaurs were a group of mostly-herbivorous archosauromorph reptiles, distantly related to the ancestors of crocodiles, pterosaurs, and dinosaurs. They lived across Eurasia, Africa, and North America during the mid-to-late Triassic period, and their lineage included some weird and diverse forms – such as the bull-horned Shringasaurus, the long-beaked Teraterpeton, and possibly also the gliding kuehneosaurids.

Spinosuchus caseanus here was yet another one of these Triassic allokotosaurian weirdos, part of the trilophosaurid family and closely related to Trilophosaurus and Teraterpeton.

Living about 221-212 million years ago in what is now northwest Texas, USA, Spinosuchus was around 2.2m long (~7’2″) and had distinctive elongated neural spines along the vertebrae of its back and the base of its tail, forming a “high back” or short “sail”. Since it’s only known from a partial spinal column the rest of its anatomy isn’t known for certain, but it probably had body proportions similar to its close relative Trilophosaurus, with sprawling limbs and a short-snouted beaked head adapted for herbivory.

Like many other fossil “sailbacked” animals the exact function of Spinosuchus’ elongated vertebrae is unclear, but the structure may have been used for visual display. I’ve depicted it here with a speculative frill of colorful elongated scales, along with a flashy dewlap.

Elasmotherium

Elasmotherium sibiricum was a giant rhinoceros that lived during the mid-to-late Pleistocene epoch, between about 800,000 and 39,000 years ago. Found across much of the Eurasian steppe dry grassland environments, it stood around 2.5m tall (8’2″) at the top of its humped shoulders and weighed about 4 tonnes (4.4 US tons), making it close in size and mass to a modern elephant.

It was the last known representative of a particularly ancient lineage of rhinos, last sharing a common ancestor with modern forms over 40 million years ago.

A large bony dome on its forehead is traditionally thought to have supported an enormous keratinous horn like the distantly-related woolly rhino, but a 2021 study has recently challenged that interpretation. The dome structure was actually rather thin-walled and wouldn’t have been able to support the weight of a giant horn, instead probably being covered by a much stumpier backwards-pointing nub – while an enlarged nasal cavity inside the dome also suggests it may have actually functioned as a resonating chamber, similar to the crests of hadrosaurs or the extinct wildebeest Rusingoryx.

It also had a smaller toughened “pad” on its nose that may have been used along with a prehensile upper lip to dig around in the soil for plant roots and tubers.

Whatcheeria

Whatcheeria deltae here was an early tetrapod from the Early Carboniferous, about 340 million years ago, descended from the earlier fish-like forms and closely related to the ancestors of modern amphibians and amniotes.

Hundreds of fossils of this species have been found in Iowa, USA. Most represent juveniles, but rare larger specimens suggest fully-grown adults reached at least 2m long (6’6″).

Its large chunky limbs and flat feet seem to have been well-adapted for walking, with body proportions similar to later temnospondyl amphibians. But its cartilaginous ankles and the presence of lateral lines on its skull suggest it was still primarily aquatic, possibly walking along on the bottom of the ancient lakes, rivers, and swamps it inhabited.

It also had an unusually long neck and oddly-shaped skull for such an early tetrapod – most other known species had rather wide and flat skulls, but Whatcheeria‘s head was instead proportionally taller and narrower. Along with heavily reinforced sutures between the bones of its skull, it would have had a very powerful bite and been able to resist the twisting forces of large struggling prey in its jaws, suggesting it was a specialized crocodile-like predator.

Echinochimaera

Echinochimaera meltoni here was a cartilaginous fish found in the Bear Gulch Limestone deposits in Montana, USA, dating to the Early Carboniferous about 326-318 million years ago.

It was an early member of the chimaera lineage, but unlike its mostly-scaleless modern relatives its body was covered in small shark-like placoid scales.

It also showed a large degree of sexual dimorphism, with males and females almost looking like different species entirely. Males are identified by the presence of claspers and were up to 15cm long (6″), with four pairs of spiny “horns” on their heads, larger more pointed dorsal fins, and rows of spines along their tails. Females were less than half the size of males at just 7cm long (2.75″), with only one pair of smaller “horns” and none of the additional spines.

The rounded bodies and relatively small paddle-like tail fins of both sexes suggest they weren’t very strong swimmers, probably relying on their large dorsal fin spines to defend themselves – which may have been venomous much like those of modern chimaeras.