It Came From The Wastebasket #14: The Protorthoptera Puzzle

Protorthoptera was a group of fossil insects created in the early 20th century to categorize “primitive” neopterans – some of the earliest insects to have evolved the ability to fold their wings down over their backs. Known mostly from just fossilized forewings, they first appeared around 320 million years ago in the late Carboniferous, and after heavy losses during the Great Dying mass extinction they eventually disappeared in the mid-Triassic about 240 million years ago.

And this group was a massive wastebasket taxon.

As early as the mid-20th century the protorthopterans were recognized as being a general taxonomic dumping ground, containing a mixture of early members of multiple different “orthopteroid” insect lineages. But invertebrate paleontologists at the time considered this collection of “primitive” insects to lack enough distinctive features to confidently separate them out from each other, and so the highly paraphyletic grouping continued to be used well into the 1990s.

An illustration of Ctenoptilus elongatus, an extinct insect. It has long thin antennae, a small grasshopper-like head, six legs each ending in two small claws, a cylindrical abdomen, and two pairs of large wings folded over its back. It's colored red, tan, and dark brown, with striped markings on its wings.
Ctenoptilus elongatus

But in the early 2000s this situation finally changed. Proper cladistic analysis of protorthopteran fossils identified defining features of the wing vein patterns, and many species were reclassified into various lineages within the Archaeorthoptera – which includes modern grasshoppers, crickets, and locusts along with several closely related fossil groups like the titanopterans and caloneurodeans.

“Protorthoptera” is still sometimes used in a loose sense for fossil neopteran insects that still can’t be confidently classified anywhere else, so the wastebasket isn’t entirely cleared here.

And there are some alternate classification systems (mainly proposed by Russian paleontologists) that instead consider many protorthopterans to be notopterans closely related to modern ice-crawlers, and place others as part of other modern neopteran lineages such as webspinners and true bugs.

Hopefully better fossil discoveries and future studies will eventually help clear things up, and give us a better overall picture of the evolution of these insects.

It Came From The Wastebasket #13: Certifying Cetiosaurus

Discovered in England in the early 1840s, Cetiosaurus was one of the first sauropod dinosaurs known to science – although its scrappy remains were initially mistaken for a massive crocodile-like marine reptile, hence its name meaning “whale lizard”.

It wasn’t even identified as being some sort of dinosaur until a couple of decades later, and then in the 1870s discoveries of much more complete sauropods like Brontosaurus and Diplodocus in North America led to it finally being recognized as a similar long-necked form.

Like some other early dinosaur discoveries it quickly became a wastebasket taxon, with vaguely-similar fragmentary fossils found in England, France, Switzerland, and Morocco all being lumped under its name. By the end of the 20th century nearly 20 different Cetiosaurus species had been created, most of them highly dubious and based on poor fossil material without any distinctive anatomical features.

An illustration of Cetiosaurus, a sauropod dinosaur. It has a small head atop a long neck, a chunky four-legged body with mitten-like forefeet and three-clawed hindfeet, and a long tapering tail. It's colored pale teal with darker red-brown stripes and a lighter underside, with brighter yellow-green towards its head. There are also speculative red quill-like structures on its throat, cheeks, neck, and tail tip.
Cetiosaurus oxoniensis

It wasn’t until the early 2000s that the mess was finally cleaned up. A major revision and redescription of Cetiosaurus determined that just one species was actually valid: Cetiosaurus oxoniensis from the mid-Jurassic of England, known from fairly complete remains and dating to about 170 million years ago.

But this did create a new problem – it meant that the original type species Cetiosaurus medius wasn’t actually based on anything distinctive. So, much like what happened with Iguanodon, the type species was officially changed to Cetiosaurus oxoniensis in 2014, ensuring that this historically significant genus was defined by decent fossil material rather than by dubious fragments.

It Came From The Wastebasket #12: Coelurosaur Confusion

Historically Coelurosauria was the counterpart to the Carnosauria, with both of them representing two major lineages of theropod dinosaurs.

Created as a group in the early 20th century, coelurosaurs quickly became a dumping ground for all small-bodied theropods – including coelophysoids, compsognathids, ornithomimids, oviraptorosaurs, dromaeosaurids, and troodontids– and for a while this wastebasket taxon also included the large-bodied ceratosaurids and tyrannosauroids, before they were moved over into the carnosaurs.

But during the 1960s and 1970s this arrangement began to break down. A better understanding of groups like dromaeosaurs revealed a confusing mixture of traditional “carnosaur” and “coelurosaur” anatomical features, and paleontologists struggled to figure out where these sorts of theropods actually fit in.

The development of cladistic methods from the 1970s onwards led to efforts to clean up the coelurosaur wastebasket, trying to figure out a more accurate version of these animals’ evolutionary relationships. After briefly collapsing Coelurosauria down to just coelophysoids and “coelurids“, the growing recognition of modern birds as living theropod dinosaurs eventually resulted in the group being properly redefined in the 1980s as “birds, and all theropods closer related to them than to carnosaurs“.

An illustration showing four examples of coelurosaurs, theropod dinosaurs closely related to birds. One the left is Citipati, a bird-like feathery oviraptorosaur that has a cassowary-like crest on its head, a short beak, a long neck, feathered wings, long slender legs, and a short tail with a feather fan at the end. It's mostly colored black and white, with bright blue and yellow face markings and small eyespots on its wing and tail feathers. At the top is Albertosaurus, a tyrannosaur with short bony crests above its eyes, tiny two-fingered hands, long bird-like legs, and a long thick counterbalancing tail. It's colored with a blotchy striped pattern of yellow, red, and dark brown, with bright blue on the crests over its eyes. On the right is Yi, a small bird-like scansoriopterygid with a fluffy feathery coat, four long tail feathers, and large membranous wings supported by a bony extension from its wrist that make it look like a dino-bat or a wyvern. It's colored brownish-grey with a yellow snout and striped markings on its neck, wings, and tail feathers. At the bottom is Sinosauropteryx, a compsognathid with a typical theropod body plan – triangular head, S-shaped neck, three-clawed hands, bird-like legs, and a long tail – but it's covered in fluffy feathers which are especially bushy on its tail. it's colored ginger-and-white, with a black raccoon-like mask marking over its eyes and a stripey tail.
Clockwise from the left (not to scale): Citipati osmolskae, Albertosaurus sarcophagus, Yi qi, Sinosauropteryx prima

The coelophysoids were finally removed entirely, reclassified as a much earlier branch of theropods – but quite a few of the other groups from earlier concepts of Coelurosauria survived this reshuffling, with the compsognathids, ornithomimids, oviraptorosaurs, dromaeosaurs, and troodontids all proving themselves to have really been closely related the whole time. Meanwhile the tyrannosauroids were brought back in, along with the therizinosaurs, alvarezsauroids, and a whole bunch of paravian and avialan lineages.

(Megaraptorans might belong somewhere in the coelurosaurs, too – possibly being tyrannosauroids – but their classification is currently being disputed.)

It Came From The Wastebasket #11: A Cetothere Change

Cetotheres were a group of small baleen whales, one of three major lineages of these cetaceans alongside the rorquals and the right whales. They first appeared in the fossil record in the mid-Miocene, about 14 million years ago (but are estimated to have actually originated 10-15 million years earlier), and disappeared during the Pleistocene about 2 million years ago.

First recognized in the mid-19th century, for a long time the cetotheres were used as a wastebasket for all fossil baleen whales that didn’t clearly fit into any modern whale families. By the start of the 21st century nearly 30 different genera representing numerous different species were all lumped into the group – and the genus Cetotherium was another wastebasket in itself with at least 12 assigned species, many of which were based on fragmentary or dubious remains.

An illustration of Ciuciulea, an extinct cetothere baleen whale. It looks similar to modern rorquals, with a streamlined and relatively slender body, but lacking the typical throat grooves of that type of whale. Its jaws are long and narrow, with a paired blowhole at the top of its head and small eyes set near the corners of its mouth. It also has fairly small flippers, a dorsal fin set about two-thirds of the way down its back, and a horizontal tail fluke. It's coloration is countershaded, mostly grey on top and white underneath.
Ciuciulea davidi

This was finally cleaned up in the 2000s, when a revision of the cetotheres cut the group down to just 6 genera. Since then a handful of additional new genera and species have been named, and while a few polyphyletic Cetotherium species may still need tidying up the cetotheres have overall gone from being a total taxonomic mess to actually being one of the best studied groups of fossil baleen whales.

Their exact evolutionary relationships with each other are still in flux, but the most surprising discovery from the improved understanding of these ancient whales is that they might not be extinct after all.

A set of three screenshots from the animated movie "Ice Age: Dawn of the Dinosaurs". The first image shows the two opossum characters Crash and Eddie asking, "Were you killed?!" The second image shows the weasel buck looking away and replying, "Sadly, yes…" The third image shows Buck leaning closer and adding "but I lived!" Buck's face has been photoshopped into that of a Cetotherium whale in both shots.

A study in the early 2010s suggested that the pygmy right whale may actually be a living cetothere. This classification was initially controversial, but further discoveries of fossil relatives of this enigmatic modern whale and comparisons of their distinctive inner ear anatomy have provided stronger evidence for an evolutionary link.

At this point it seems fairly likely that the pygmy right whale really is either the last surviving representative of the cetothere lineage, or at least is a very close evolutionary “cousin” (a “cetotherioid”) closer related to them than to any other modern baleen whales.

It Came From The Wastebasket #10: Struggling With Stegoceras

First described and named in the early 1900s, Stegoceras validum was a dog-sized small pachycephalosaur that lived in Alberta, Canada, during the Late Cretaceous (~77-74 million years ago).

Initially just known from its skull domes, it was one of the first pachycephalosaurs to be discovered and was very poorly understood until more complete remains were found in the 1920s. Then it spent a couple of decades being mixed up with Troodon due to similarities in tooth shape, until the discovery of Pachycephalosaurus led to pachycephalosaurs finally being recognized as a distinct group of ornithischian dinosaurs in the 1940s.

An illustration of Stegoceras, an extinct pachycephalosaur. It's a small bipedal dinosaur with tiny arms, bird-like legs, a speculative coat of fluffy protofeathers over most of its body, and a long tapering tail with speculative bristly quills. It has a large bony dome on its forehead, rimmed with short spikes, and a short snout with a stubby beak. It's mainly colored white and grey, with brighter red and yellow markings on its face and red towards the tip of its tail.
Stegoceras validum

For much of the 20th century Stegoceras was treated as a wastebasket taxon for any small-to-mid-sized North American (and one Asian) pachycephalosaur, and multiple different species were named based on what were often rather dubious fragmentary fossils. But towards the start of the 21st century this mess did start getting cleaned up, merging some dubious species into the original Stegoceras validum, and moving others to separate genera like Sphaerotholus, Colepiocephale, Hanssuesia, and Sinocephale.

By the early 2000s just the Canadian Stegoceras validum remained – but then in 2011 the new species Stegoceras novomexicanum was named based on specimens from New Mexico, USA. The validity of this second species has been debated, since the fossils are juveniles and might instead belong to Stegoceras validum or another genus like Sphaerotholus, but if it is some sort of Stegoceras then it significantly re-extends the known geographic range of this little pachycephalosaur.

It Came From The Wastebasket #09: Hammering Away At Hamites

Ancyloceratines were a lineage of distinctive-looking ammonites, commonly known as “heteromorphs“, which had unusual uncoiled shells that ranged in shape from near-straight to hooked to helical to paperclip-like to “balls of string“.

Heteromorphs’ strange shells would have created a lot of drag in the water, and they may not have been especially agile swimmers, but they were very hydrodynamically stable and easily maintained neutral buoyancy. Their paleobiology has only just started to be properly understood in recent years, and now most species of these ammonites are thought to have floated suspended in the photic zone and twilight zone of the open ocean, catching small zooplankton from the water around themselves.

What these ammonites were doing obviously worked very well for them, because they were incredibly diverse and successful during the Cretaceous period. They were also the only type of ammonite to persist for a short time after the end-Cretaceous mass extinction, existing as a “dead clade walking” for another half a million years or so before finally disappearing entirely.

An illustration of Hamites attenuatus, an unusually-shaped extinct ammonite. It has a mostly-uncoiled shell shaped like a long sideways U, almost paperclip-like. At the bottom end of the shell it has a squid-like body, with large eyes and ten short webbed arms that are lined with speculative fringes for filter-feeding. It has a pinkish color scheme with a faint iridescent sheen.
Hamites attenuatus

The hamitids were a group of heteromorphs from the mid-Cretaceous (~110-90 million years ago), with their namesake genus Hamites traditionally being used as a wastebasket taxon for anything that that didn’t neatly fit into any other group of similar heteromorph ammonites.

By the late 1990s Hamites had become a mess of multiple different diverse lineages, with over 20 species all lumped together – and this was a problem because the hamitids were the ancestors of several other heteromorph ammonite lineages, and having the taxon in such disarray made studying the evolutionary origins of all those other groups very difficult.

So in the early 2000s attempts were made to clean this all up, figuring out the relationships between the different Hamites species and dividing the genus into multiple new genera.

There hasn’t been much more detailed research on the relationships of hamitids since then – and other groups of heteromorphs are still in need of revision – but it’s a start at clearing the wastebasket, at least.

It Came From The Wastebasket #08: Stem-Carnivoramorphs Do What Creodon’t

Creodonts were some of the earliest predatory placental mammals to evolve after the extinction of the non-avian dinosaurs, first appearing in the mid-Paleocene about 60 million years ago. Represented by two main lineages – the oxyaenids and the hyaenodonts – they ranged across North America, Eurasia, and Africa, and were the dominant large carnivorous mammals until the end of the Eocene (~34 million years ago), with forms like Sarkastodon being some of the biggest mammalian land predators of all time.

After that point they started to decline over most of their range, gradually being replaced by early carnivorans – but the hyaenodonts retained their dominance for a while longer in Africa, diversifying during the Oligocene and early Miocene and producing more giant apex predators. The last known representatives of these animals survived in Asia until the late Miocene, just 9 million years ago, ending an impressive run that had lasted for most of the Cenozoic.

This grouping was originally named in the 1870s to encompass just the oxyaenids and Didymictis (a genus now considered to be a viverravid). Just a few years later hyaenodonts, miacids, arctocyonids, leptictids, and mesonychids were all lumped in, too – and at one point creodonts were even a part of the massive insectivoran mess before instead being classified as ancestors of the carnivorans.

During the first half of the 20th century creodonts were recognized as actually being a loose collection of mostly-unrelated mammals, and over the next few decades various groups were gradually removed and reassigned to other parts of the mammal family tree. Towards the end of the century most of the creodont wastebasket had been cleared, and just the oxyaenids and the hyaenodonts were left as two branches of one seemingly distinct creodont lineage.

An illustration of two "creodonts". On the left is Patriofelis, an oxyaenid that looks like a mix between a weasel and a cat, with a short boxy snout, a low-slung body, a long tail, and a greyish color scheme with faint darker spots in its pelt. On the right is Hyaenodon, a hyaenodont that looks like a mix between a dog and a tiger, with a long boxy snout, a heavyset body, a cat-like tail, and a striped coat.
The cougar-sized oxyaenid Patriofelis ferox (left) & the bear-sized hyaenodont Hyaenodon gigas (right)

…But their evolutionary relationships were still a problem.

They’d been traditionally considered to be early carnivorans, but although they had flesh-slicing carnassials the creodonts’ versions of these teeth weren’t quite right. Different teeth in their jaws had been specialized for this function compared to those of true carnivorans – with oxyaenids and hyaenodonts having slightly different arrangements compared to each other, too – suggesting a lot of convergent evolution rather than shared ancestry.

By the 1990s it wasn’t clear anymore if the oxyaenids and hyaenodonts were even closely related to each other, or what type of mammal they actually were.

But over the last couple of decades the consensus seems to have become that creodonts weren’t a single natural group, but that they were still related to carnivorans – oxyaenids and hyaenodonts were actually two separate offshoots of the Ferae, forming an evolutionary grade of stem lineages between pangolins and the carnivoramorphs.

A cladogram showing the classification of oxyaenids and hyaenodonts within the group Ferae. They're shown as two separate lineages branching off between pangolins and the ancestors of modern carnivorans. A bracket marking indicates that they both traditionally used to be classified as "creodonts".

It Came From The Wastebasket #07: Carnosaur Carnage

Carnosauria was originally named in the 1920s as a grouping for all of the large-bodied theropod dinosaurs known at the time.

For much of the 20th century it was used as a general wastebasket taxon collecting together all big carnivorous forms – including allosaurids, carcharodontosaurids, megalosaurids, spinosaurids, ceratosaurids, abelisauroids, and tyrannosaurids – and for a while it even included a species that later turned out to be closer related to crocodiles than to dinosaurs.

An illustration showing four different carnosaurs: Asfaltovenator, Torvosaurus, Giganotosaurus, and Baryonyx. They're all bipedal carnivorous dinosaurs with small three-clawed arms, bird-like legs, and long counterbalancing tails, but they vary in size, coloration, and most notably head shape. Asfaltovenator and Giganotosaurus have fairly typical boxy theropod heads, while Torvosaurus has a longer snout and Baryonyx has slender crocodile-like jaws.
From left to right: Asfaltovenator vialidadi, Torvosaurus tanneri, Giganotosaurus carolinii, & Baryonyx walkeri

But then cladistic analysis in the 1980s and 1990s revealed that some of these theropods weren’t actually closely related at all. Carnosaurs weren’t a natural lineage but instead were highly polyphyletic, with the physical similarities between them seeming to be more due to convergent evolution than direct shared ancestry.

Some carnosaurs were split off and reclassified as more “primitive” types of theropod, while the tyrannosaurs were placed much closer to birds with the coelurosaurs. The remaining “carnosaurs” were just the allosaurids, carcharodontosaurs, and their closest relatives, and some paleontologists now prefer to use the name Allosauroidea for this group to distance it from the previous wastebasket mess.

…But Carnosauria might not be done just yet.

A screenshot from "Phineas and Ferb", with the two main characters in a room lit up by an offscreen disco ball, with one grabbing the arm of the other. Text below them reads "Dude, we're getting the band back together!" Both of their heads have been photoshopped into those of Megalosaurus and Asfaltovenator.

The discovery of Asfaltovenator in 2019 complicated matters once again, with a mixture of anatomical features linking it to both the allosauroids and the megalosauroids (megalosaurids, spinosaurids, and their relatives) – suggesting that these two groups might actually have been closely related to each other in a single lineage after all.

This would potentially return Carnosauria back to something surprisingly close to its original definition, with the various megalosauroids now forming an evolutionary grade leading to the allosauroids.

It Came From The Wastebasket #06: Messy Miacids

Most modern meat-eating placental mammals are carnivorans, a group that contains two distinct lineages: the feliforms (cats, hyenas, mongooses, viverrids, civets, linsangs, and euplerids) and the caniforms (dogs, bears, seals, raccoons, and mustelids).

The closest living relatives of these animals are pangolins, and their last common ancestor probably lived sometime between the Late Cretaceous and early Paleocene. But the actual early evolutionary history of the carnivorans themselves is rather murkier.

The earliest known carnivoran-like forms – known as carnivoramorphs – all looked vaguely-genet-like and were an ecologically diverse bunch of small predators, ranging from weasel-sized tree-climbers to fox-sized ground-based hunters, found all across North America and Eurasia during the Paleocene and Eocene. They lacked most of the anatomical specializations of true carnivorans, and didn’t quite fit into either the feliforms or caniforms, but their distinctive carnassial teeth make it obvious they were still very closely related.

From their initial discovery in the late 19th century, through to the late 20th century, these carnivoramorphs were traditionally all lumped together under the name “miacids“. As a result the group quickly turned into a big wastebasket taxon of similar-looking animals, all united more by just not being true carnivorans than by any shared characteristics between themselves.

An illustration of Miacis, an extinct mammal related to early carnivorans. It's a somewhat weasel-like animal with a small triangular head, small rounded ears, a long tubular body, cat-like limbs, and a long bushy tail. It's depicted with brownish fur, with raccoon-like black-and-white markings on its face and a stripey tail.
Miacis parvivorus

But during the last couple of decades this mess has finally started to get cleared up. One distinct lineage of miacid-like animals called viverravids were split off, now thought to be the one of very earliest branches of the carnivoramorph evolutionary tree. Several other “miacids” have also been reassessed and renamed, reclassified as falling into various points in an evolutionary grade between viverravids and true carnivorans, and a couple of species even turned out to actually be caniforms.

A cladogram showing the classification of carnivoramorphs. Miacis is shown as just one of several different branching lineages originating between viverravids and modern carnivorans. A bracket marking indicates that everything before the true carnivorans traditionally used to be considered to be "miacids".

The true carnivorans arose from somewhere within the “miacids” during the mid-Eocene, but it’s still unclear where exactly to draw the taxonomic line between them. Forms like Quercygale and Tapocyon might be very close to the ancestral carnivoran – but they might instead be early feliforms – and some studies have also proposed that nimravids (“false sabertooth cats”) may actually be “advanced” carnivoramorphs instead of early feliforms.

There are also quite a few remaining “miacids” that still need sorting out, especially in the genus Miacis. There have to be other distinct lineages of these carnivoramorphs still hidden in the remaining wastebasket pile, and if we can eventually distinguish them from each other it might help to make early carnivoran relationships a bit clearer.

It Came From The Wastebasket #05: The Trouble With Troodon

Troodontids were small bird-like theropod dinosaurs, lightly built with slender legs and sickle-shaped “raptor” claws on the second toes of their feet. They had fairly big brains proportional to their body size, rather like modern birds, and their large forward-facing eyes had good depth perception. Owl-like asymmetrical ears in some species gave them a very keen sense of hearing, suggesting they may have been nocturnal hunters using sound to pinpoint the location of small prey.

The original specimen of the namesake of the group, Troodon formosus, was a serrated tooth discovered in the 1850s, about 77 million years old and originating from the Late Cretaceous Judith River Formation fossil beds in Montana, USA. It was so little to work with that it was initially mistaken for a lizard tooth, then during the 20th century it was recognized as belonging to a dinosaur and spent time classified as a megalosaurid, then a pachycephalosaur, then finally as a small theropod similar to the Mongolian Saurornithoides.

In the late 1980s it was merged together with multiple other troodontids (including Stenonychosaurus of speculative “dinosauroid” fame), and since Troodon had been the first of all of them to be named it took priority as the genus name.

And then for a while every single Late Cretaceous troodontid specimen from North America was also lumped into Troodon, turning it into a wastebasket taxon.

An illustration of five troodontids standing in a circle facing each other. They're all very bird-like feathered dinosaurs with vaguely owl-like faces, reddish-orange and dark brown plumage, and white spots and bars on their longer wing and tail feathers. There are minor variations in their color shades and markings, but otherwise they all look incredibly similar to each other. The overall composition of the image is similar to that of the "Spider-man pointing at Spider-man" memes.

The problem was that all these troodontids came from locations separated by thousands of kilometers and millions of years of time, and it’s unlikely that they all actually represented just one single species. But they were only known from rare fragmentary remains, making distinguishing them from each other difficult, and the original Troodon tooth didn’t really have any distinctive features either – it turns out most troodontid teeth all look exactly the same!

It was becmoning increasingly dubious whether Troodon was even a valid name at all, and during the 2010s several paleontologists began trying to sort the mess out. The old names Pectinodon and Stenonychosaurus were revived, and some ‘Troodon’ fossils were also split off and given completely new names, becoming Albertavenator and Latenivenatrix*.

* Although Latenivenatrix might not actually be distinct enough from Stenonychosaurus to justify having a separate name.

As of 2022, Troodon itself is now in a sort of taxonomic limbo, with some paleontologists abandoning it as a dubious name while others are still arguing in favor of continuing to use it. The name could potentially be properly rescued if the original tooth can be clearly linked to better fossil material, letting Troodon take over priority again from one of the other better-established troodontids, or by defining a new type species similar to what happened with Iguanodon.

…But with how incredibly generic that tooth is, both of those options would be very difficult.