invertebrate – Page 5 – Nix Illustration

Kalligrammatids

Did you know butterflies weren’t the first insects to look like butterflies?

Lepidopterans (the group of insects containing moths and butterflies) have been around since the Late Triassic – but it wasn’t until the diversification of flowering plants during the Cretaceous that recognizable moths would have evolved, and true butterflies didn’t actually appear until the early Cenozoic.

Before then, back in the mid-Jurassic about 165 million years ago, a completely different group of insects convergently evolved remarkably butterfly-like features such as large colorful scaled wings and long sucking proboscises.

Known as the kalligrammatids, these insects were giant members of the lacewing group, related to modern forms like antlions and owlflies. But unlike their predatory relatives the kalligrammatids were specialized pollinators, possibly having a mutualistic relationship with the flower-like cones of bennettitales or the pollination drops of some types of conifers. They seem to have originated in China and were found across Asia and Europe by the Late Jurassic, but a few fossils from South America suggest they were even more widespread and may just have a poor fossil record.

They reached wingspans of up to 16cm (~6″), comparable to some of the largest modern butterflies, and often sported conspicuous anti-predator markings on their wings such as stripes and eyespots – so it’s not surprising that they’re often nicknamed the “butterflies of the Jurassic”.

Rather ironically, the extinction of the kalligrammatids was probably linked to the rise of the flowering plants that the true butterflies would later be so dependent on. As flowers diversified and plants like the bennettitales declined, the kalligrammatids dwindled and disappeared, with the last known fossil record coming from the mid-Cretaceous of Brazil about 113 million years ago.

But while they were around, I do wonder if they also exhibited some similar behaviors – such as mud-puddling for extra nutrients, and specifically the habit of drinking the tears of larger animals that we see in some species. Perhaps some non-avian dinosaurs like this Dilong occasionally put up with kalligrammatids sitting on their faces!

Eons Roundup 3

Some more recent work I’ve done for PBS Eons!

The eurypterids Hibbertopterus and Brachyopterus, from “When Giant Scorpions Swarmed the Seas”
https://www.youtube.com/watch?v=1sQXTXbuLYo

The short-faced bears Plionarctos and Arctotherium, from “The Mystery Behind the Biggest Bears of All Time”
https://www.youtube.com/watch?v=KtsOhmBb92E

The big cats Panthera blytheae and Panthera atrox, from “The Ghostly Origins of the Big Cats”
https://www.youtube.com/watch?v=oPJnqWke5n8

Clausocaris

While this might look like a sci-fi alien design, it was actually a very real Earth animal!

This strange-looking creature was Clausocaris lithographica, a member of a group of unique marine arthropods known as thylacocephalans. Only about 3.5cm long (1.4″), it lived in a shallow tropical lagoon environment during the Late Jurassic of Germany, about 150-145 million years ago.

Like most other thylacocephalans it had a narrow flattened shield-like carapace, three pairs of large grasping limbs, and a battery of swimming appendages further back – along with absolutely enormous bulbous eyes. Based on this anatomy it would have been a highly visual hunter, using its huge eyes to locate prey items and then snagging them with its long spiny limbs.

And we’re not even entirely sure what type of arthropods thylacocephalans actually were. They’re generally thought to be some sort of crustacean, but their highly modified anatomy makes linking up their exact evolutionary affinities very difficult. Whatever they were, they must have been incredibly successful as a group because they first appeared in the early Cambrian (~518 mya) and survived all the way into the Late Cretaceous (~94 mya).

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.

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.

Vaderlimulus

Vaderlimulus tricki, a horseshoe crab from the Early Triassic of Idaho, USA (~251-247 mya). Named for its resemblance to the shape of Darth Vader’s helmet, it’s the earliest known Mesozoic horseshoe crab from North America and was closely related to another oddly-shaped form from Australia.

It was much smaller than its modern relatives, only about 10cm long (4″), and probably lived in a brackish estuary environment where seawater and freshwater met.

Thanahita

Thanahita distos, a recently-named species from the mid-Silurian of the UK (~430 mya).

This little lobopodian was very closely related to the famous Cambrian Hallucigenia, but it lived over 70 million years later – giving us the first evidence that these weird worms weren’t just short-lived “evolutionary experiments”, but must have actually been a very successful lineage that thrived for quite a long time.

Measuring around 3.5cm long (1.4″), it had seven pairs of legs tipped with one or two claws each, and at least two pairs of shorter tentacles on its neck. The head region of the only known fossil specimen wasn’t preserved, so it’s unclear exactly what its front end looked like – but it would have probably been quite similar to Hallucigenia with a slender oval head, two simple eyes, and a small round mouth ringed by tiny teeth.

Unlike its spiky relative, however, Thanahita’s back was covered in rows of numerous small raised soft-tissue “tufts”. I’ve reconstructed it here with them brightly warning colored, mimicking stinging coral polyps.

Almost-Living Fossils Month #16 – Fancy Triangle Clams

Trigonia was a genus of bivalve mollusc that first appeared in the Middle Triassic, around 245 million years ago. Part of a much older lineage (the trigoniidans) that originated over 400 million years ago in the Late Silurian or Early Devonian, and distantly related to modern freshwater mussels, these bivalves have been found in marine deposits all around the world.

Their triangular shells had complex internal hinges, and often featured elaborate patterns of ribs and tubercules (which may have been adaptations to increase burrowing efficiency) that made them very visually distinctive. They lived mainly in shallow coastal environments, and in some places their fossils are so common that they must have been very numerous animals in their ecosystems.

Trigonia costata was a species living in Europe during the Early-to-Middle Jurassic (~174-166 mya), around the time when the trigoniidans were exploding in diversity. Usually around 5-7.5cm in length (2-3″), it was one of the longest-lasting individual species of Trigonia and one of the most common at the time.

Along with their other trigoniidan relatives, various Trigonia species continued to evolve throughout the entire rest of the Mesozoic, and while almost all of them went extinct at the end of the Cretaceous a few did manage to hang on into the Cenozoic.

The last record of an actual Trigonia comes from Argentina at the very end of the Paleocene, about 56 million years ago. After a nearly 200-million-year run, this long-lived genus finally disappeared – but although Trigonia itself was gone, that wasn’t quite the end of the trigoniidans altogether.

A single remaining lineage quietly continued on all the way into modern day, either descended from one of the Trigonia species or very closely related to the genus, living in waters off the coast of Australia and Tasmania. Known as Neotrigonia, they’re not quite as elaborately ornamented as some of their ancient relatives, but their complex shell hinges give them away as the only living trigoniidans – and their anatomy can give us some hints about what Trigonia’s soft tissue parts may have looked like, such as the presence of an unusual boot-shaped muscular foot that helps them burrow rapidly into the seafloor.

Almost-Living Fossils Month #12 – The Other Nautiluses

Nautiloids are represented today by just two living genera (Nautilus and Allonautilus), but they have a lengthy evolutionary history going back almost 500 million years.

The peak of their diversity was during the first half of the Paleozoic, with many different shapes of shells from coiled to straight, then they began to decline when their relatives the ammonites and coleoids appeared and began to compete for similar ecological niches. Although a few groups of nautiloids survived through the end-Permian mass extinction, most of them had disappeared by the end of the Triassic, leaving just one major remaining lineage known as the Nautilina (or Nautilaceae).

During the mid-to-late Jurassic (~165 mya) two new groups split away from the ancestors of the modern nautiluses – the cymatoceratids and the hercoglossids.

Cymatoceratids such as Cymatoceras sakalavum here had shells with a ribbed texture. Living during the Early Cretaceous, about 112-109 million years ago, this particular species is known from Japan and Madagascar and could reach a shell diameter of over 15cm (6″).

Hercoglossids, meanwhile, were much more smooth in appearance, but both groups also had more complex undulating sutures between their internal chambers than modern nautiluses do.

These nautiluses made it through the end-Cretaceous mass extinction and had a brief period of renewed success, filling the ecological roles left vacant by the extinct ammonites. But by the end of the Oligocene (~23 mya) both the cymatoceratids and hercoglossids vanished, possibly unable to deal with cooling oceans and the evolution of new predators.

Some of the hercoglossids’ Cenozoic descendants, the aturiids, managed to last a little longer into the Early Pliocene (~5 mya) before another period of cooling seems to have finished them off. Past that point, all that was left of the once-massive nautiloid lineage were their cousins the nautilids, who gave rise to today’s few living representatives.

(It’s also worth noting that the classification of the cymatoceratids seems to be in flux right now. Some paleontologists currently don’t consider Cymatoceras itself to actually be part of the group, instead being a nautilid much closer related to modern nautiluses. If this is the case then the cymatoceratids may not have actually survived past the Late Cretaceous – but the Cymatoceras genus alone still counts as an “almost-living” fossil since its various species ranged from the Late Jurassic to the Late Oligocene.)

Almost-Living Fossils Month #08 – A Lot Of Lobsters

Hoploparia was a type of clawed lobster that first appeared in the fossil record in the Early Cretaceous about 140 million years ago. Many many different species within this genus have been found all over the world – over 100 of them have been described! – with quite a lot of anatomical diversity between them, showing that these lobsters were very good at adapting to a wide range of habitats and climates.

Although the vast majority of Hoploparia species lived just in the Cretaceous period, a small number of them did survive the end-Cretaceous mass extinction 66 million years ago. Hoploparia stokesi here was one of them, known from both the Late Cretaceous and Early Paleocene of Antarctica (~70-61 mya) – and was actually one of the first fossils ever described from the continent.

Specimens of this species are usually about 13cm long (5″), and show an evolutionary shift over time, developing much stronger claws and jaws, suggesting they were adapting their diet towards hard-shelled prey.

Various species of Hoploparia persisted on in North America, Europe, and Antarctica for the first half of the Cenozoic, but they never recovered to anywhere close to their Cretaceous levels of diversity. By the Early Miocene (~23-16 mya) there was just one known species left hanging on in Antarctica, and then they were gone.

(However, some modern lobster genera may in fact have originated from somewhere within the huge Hoploparia lineage back in the Cretaceous, so they might at least still have some close living relatives!)