Episode 499: The Mystery of Amiskwia

**Further reading:** Cambrian Explosion Month #18: Stem-Gnathifera Ambiguous Amiskwia Amiskwia, possibly \[picture taken from above link]: **!https://strangeanimalspodcast.blubrry.net/wp-content/uploads/2026/08/10-amiskwia-300x142.png** **Show transcript:** Welcome to the Patreon bonus episode of Strange Animals Podcast for May 2025! We’ve talked about a lot of strange and mysterious animals from the Cambrian in past episodes, especially episode 69, but I don’t think we’ve learned about Amiskwia yet. For a long time it was another mystery animal from the Burgess Shale and a few other places, dating back as much as 518 million years ago, but as of only a few years ago the mystery seems to be solved, at least mostly. Amiskwia grew about an inch long, or 2.5 cm, which actually made it one of the larger animals that lived in the Cambrian. It probably looked superficially like a slug, with a slightly flattened body and a pair of short tentacles on its head. It had a paddle-shaped tail and two flaps on its sides that probably acted as fins to help it swim. Its mouth was on the underside of its head and was surprisingly complicated, with two pairs of plates with little spikes on them. We even know about its internal anatomy, since some of the Amiskwia fossils are so well preserved that its insides can be studied too. It had a brain and a simple digestive tract. Amiskwia was described in 1911 by Charles Walcott, who described a lot of the Burgess Shale fossils. Walcott classified it as a type of arrow worm. When scientists gave it a closer look later, not everyone agreed it was related to modern arrow worms. Some suggested it might be a type of ribbon worm, or maybe an early mollusk, while others argued that it was so different from known animals that it belonged in its own phylum. A 2019 study suggested that Amiskwia’s weird mouth plates matched up with the mouth plates in a living animal, and a 2022 follow-up study confirmed the 2019 findings. Not everyone agrees, but as of now, Amiskwia is considered an ancestral gnathiferan. There! Mystery solved! Wait, what do you mean you don’t know what a gnathiferan is? As everyone knows, especially me, I definitely didn’t just learn about this type of animal myself just now, gnathiferans include a lot of different animals with complex jaws—not like your own jaws, but with little plates and spikes and moving parts made of chitin. Most gnathiferans are tiny, microscopic or barely a few millimeters long, so Amiskwia was a giant in comparison. Arrow worms are also generally considered to be gnathiferans, so Wolcott wasn’t too far off in his description of Amiskwia. We don’t know what Amiskwia ate, but it could probably swim pretty well and most likely hunted other animals or scavenged already dead ones. Scientists think it probably spent most of its time swimming well above the sea floor, which is why it’s a relatively rare fossil. Another Cambrian mystery animal that lived even earlier than Amiskwia, around 520 million years ago, and which is probably related to it, is Timorebestia. Its fossils were discovered in Greenland and only described in 2024. It had a pair of long tentacles or antennae, a rounded paddle-like tail, and fins on each side of its wide, flattened body. Its tentacles were around half the length of its body–and if Amiskwia was a giant compared to modern gnathiferans, Timorebestia was a colossus! It grew almost 8 inches long, or over 20 cm, not even counting its tentacles! Some Timorebestia specimens are so well preserved that scientists can identify what they ate right before they died, and it looks like they mostly ate small arthropods. Timorebestia was probably the biggest and strongest predator in the area when it was alive, one of the earliest apex predators discovered. Another similar animal was Nectocaris, which has been discovered in the Burgess Shale of Canada and other Cambrian fossil sites in China and Australia. It was flattened and had a pair of tentacles on its head, and a fin on both sides of its body–but it had a lot of features not found in Amiskwia and Timorebestia, including eyes. It also seems to have had a tube or funnel of some kind that emerged from the underside of the body near the head. It might have been a proboscis of some kind, but some scientists think it was a funnel like the ones found in modern squid, used to jet through the water quickly. Many scientists even think Nectocaris was a precursor to squid and other cephalopods, but other scientists disagree. Some specimens are about one inch long, or around 3 cm, while others are around 4 inches long, or about 10 cm. This might mean there were two species, or that the small ones were juveniles, or that males and females were different sizes. We just don’t know. Small animals, especially ones with mostly soft bodies, don’t fossilize as often as larger and more robust animals. We’re very lucky that we have so many beautifully detailed Cambrian fossils, since so many modern gnathiferans and their close relations aren’t otherwise found in the fossil record at all. Thanks for your support, and thanks for listening!