Preternatural History

Nerding out about animals and stuff since 2026

[sexy-hallucigenia]

Hellooooo

I like natural history. This is a place for me to document whatever creature I'm currently obsessed with and felt like researching. If you are a fellow nerd you may enjoy <3

[amnhnyc]

This cute little critter isn’t AI-generated. Meet the hairy horned dorid (Acanthodoris atrogriseata.). Found in intertidal habitats in the Northern Pacific, including Washington state’s Puget Sound, this species grows about 1.1 in (2.7 cm) long. The hairy horned dorid is a nudibranch—and it’s just one of the more than 2,000 known species of these soft-bodied marine molluscs!

Photo: Paul Norwood, CC BY-NC 4.0, iNaturalist

[sexy-hallucigenia]

Hallucigenia

Of course, I had to have my first post be about the creature this blog is named for. Look at this horrible worm.

This thing is so weird, even amongst the weirdness of the Cambrian, that scientists were unsure of which part was the head and which was the tail, or for that matter which set of appendages it used to walk.

They belong to the clade Panarthropoda which includes modern arthropods, tardigrades, and velvet worms, but is part of an extinct group of worms in this clade called lobopodians. Lobopodians are all pretty weird, essentially being described as marine worms with stubby legs. In fact we spent so much time trying to figure out just what this thing is, we still don't know that much about how it lived, other than educated guesses.

It's possible that the little tentacle appendages near its face would pick up particles to pass to the mouth, or possibly hollow tubes on each tentacle were themselves individual mouths connected to the gut.

I do think it's aptly named, appearing as something you might see while on acid, but being only 1-2 inches long, it's not quite as terrifying as some of my other favorite specimens from the Cambrian explosion. I think I like it so much because I'm just tickled by the image of a couple paleontologists looking at this fossil and going "which part is the head and which is the butt?" and having that be an entire topic of research.