#doryaspis

results of this week's #Paleostream flocking

today we sketched Tusciziphius, Cyrtograptus, Callawayia, and Doryaspis

Flocking Together #111

Tusciziphius/Cyrtograptus

Cambrian baby

Devonian baby

Triassic baby

🐟 fossil fish gang 🐟

While Doryaspis nathorsti here looked a bit like a weird prehistoric sawfish, it was actually an ancient jawless fish more closely related to modern lampreys and hagfish.

Measuring just 15cm long (6"), this odd little fish lived in the shallow seas of what is now the Arctic Svalbard archipelago, around 407 million years ago during the early Devonian period when the region was located in much more tropical latitudes.

It was part of a group called the heterostracans, a lineage of jawless fish with heavy armor covering the fronts of their bodies. They had no paired fins and relied solely on their powerful tails for propulsion, and some like Doryaspis also developed large stiff wing-like projections from the sides of their armor that acted like hydrofoils to provide extra lift while swimming.

But the strangest feature of Doryaspis is that pointy serrated saw-like "snout" – which wasn't actually a snout at all, but instead formed from a part of its jawless mouth roughly equivalent to the lower lip and chin.

It's unclear what the purpose of this appendage was, but it might have been used for prey detection, probing around the muddy seafloor in a similar manner to sawfish or the big-chinned porpoise Semirostrum.

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Doryaspis

Artwork by Franz Anthony / @franzanth

A long projection that sprouted out under its mouth gave this fish its name, which means “Dart Shield.” It’s also known for having tough head armor, scaly tail, and a pair of side plates that look like airplane wings.

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Dart Shield (Doryaspis nathorsti and Doryaspis arctica)-

This armored, jawless fish was discovered in Spitsbergen, Norway. They lived during the Devonian period, about 350 million years ago. Its most definitive feature is the large armored shield that covers most of its body.  The main difference between the D. nathorsti and D. arctica is that the D. nathorsti (pictured above) toothy spikes running along its snout and the front of its extended lateral spines (branchial plates). The D. arctica is smaller and has no spikes.

This prehistoric fish had a long bony protrusion near its mouth, possibly to disrupt sediment to suction up whatever was hidden underneath. The saw-like “snout” ( the pseudorostrum) was actually an extension of its “chin” plate, rather than its “nose” (the rostrum), as seen on a modern day sawfish. It had a long, flexible tail with thick scales. Its downward curving branchial plates were thought to help it maintain level swimming.