The paleontological literature is a showcase for tragedy — it’s a graveyard of long-dead species, all snuffed out millions and millions of years before any human was around to appreciate them, and all we can do is look in awe at their fossilized corpses. In particular, fans of the Cambrian fauna can only pine for magnificently weird creatures that have been extinct for hundreds of millions of years, and represent entire exotic lineages that have left no descendants today. Two of the strangest are Anomalocaris and Opabinia.
Two of the most peculiar Burgess Shale animals, Anomalocaris and Opabinia, illustrate the complicated history of research of many Cambrian soft-bodied taxa – a result of their unfamiliar morphologies compared to the occupants of modern oceans. Both Anomalocaris and Opabinia possess compound eyes, lateral swimming flaps, filamentous setal structures, and a tail fan. Recent work has revealed that Anomalocaris and its relatives, the radiodonts, are united by the presence of paired sclerotized protocerebral frontal appendages and mouthparts composed of plates of multiple sizes, forming a diverse group containing over 20 taxa. Radiodonts range in age from the early Cambrian to at least the Devonian, and have been recovered from numerous palaeocontinents. Meanwhile, the most celebrated animal from the Burgess Shale, Opabinia regalis, with its head bearing five stalked eyes and a proboscis, remains the only opabiniid species confidently identified and is only known from a single quarry in the Burgess Shale. Myoscolex ateles from the Emu Bay Shale was proposed as a possible close relative, though this interpretation was hotly contested, and other authors have proposed a polychaete affinity.
The radiodonts (arthropods with mouths containing plates arranged in a wheel, that irised open and closed) are diverse and notorious. For a time, they were the largest predators on the planet, with their paired long spiky Great Appendages extending from the front of their head. Like the quote says, the opabiniiids are known from one location and one species, but they are weird. A similar array of swimming flaps like Anomalocaris, but then having 5 eyes on stalks and a long snout with a mouth on the end of it…it’s heartbreaking that they no longer exist. Spiders are cool and all, but I’d love to have schools of anomalocariids or opabiniids swarming in our local lakes.
At least one new opabiniid species has been identified, though. This cutie:
For perspective, here’s where they fall on the phylogenetic tree.
Tardigrades and velvet worms and mantis shrimp are certainly wonderful and interesting animals, but I have to yearn to see more of that glorious radiation of interesting forms in between. All gone, though. If gods were real, they’d never have let them die off.
Still have my copy of Wonderful Life around here somewhere. I’ll have to crack it open again.
John Harshman says
Wonderful Life is now so way out of date as to be nearly useless in describing the Cambrian radiations. I suggest The Cambrian Explosion, by Doug Erwin and Jim Valentine. It’s much more technical but, I think, not out of reach for the interested layman. It’s also very expensive, but that’s what libraries are for.
Also this fine and quite readable paper, even though it’s 20 years old: Budd G.E., Jensen S. A critical reappraisal of the fossil record of the bilaterian phyla. Biological Reviews 2000; 75:253-295. Sadly, I can’t find it free on the web anywhere.
For that matter:
And thus, a review of :
Wonderful Life blew my mind when I read as a teenager 20 years ago. Just recently I got around to reading Crucible of Creation, and then some Wikipedia bits on more recent research on Cambrian radiodonts.
I also recently ran into a Twitter account by some specialist on Cambrian radiodonts. Apparently, there are memes on this topic.
Sadly, weirdness is not an adaptive trait (well, it might be now, but probably not then). Five eye stalks are fine until someone comes along and does just as well with three or four. It doesn’t work like disposable razors.
John Harshman says
Graham Budd is a gift that keeps on giving.
@ PaulBC, # 5: Of course, eight would be ideal.
Reginald Selkirk says
Isn’t that what CPAC is for?
Joe Felsenstein says
I suggest that you are letting unfamiliarity bias you toward forms like Opabina. And that there is a principle of Conservation of Weirdness according to which all eras have an equal percentage of weird forms. As evidence I offer the duckbill platypus, Welwitschia, the venus flytrap, Mola (the ocean “sunfish”), the narwhal, the axolotl, the giant anteater, sloths, and oh yes, Homo sapiens.
Darren Naish has famously proclaimed the weirdness of rabbits. Others weird tetrapods could probably be listed.
I feel like weirdness, like art, is created at least as much by the viewer as by the thing itself. If the lines of arthropods that developed into insects and arachnids had died out, and Opabinia and its kin had undergone evolutionary radiation in their place, they would seem as familiar to us as a spider or a beetle does- and a hypothetical imagining of a spider or a beetle would strike us as bizarre. Familiarity may or may not breed contempt, but it undeniably breeds familiarity.
SC (Salty Current) says
Peter Godfrey-Smith mentions Anomalocaris in a section about arthropods in Metazoa. From the text leading up to its appearance:
(Quoted mainly because I enjoyed the choice of “exuberant” and the sentence “Add some spatulas to your head.”)
Ray Ceeya says
If gods were real we’d all be cephalopods.
It’s always worked for me!
I saw that picture of an opabinia and immediately the Pokemon theme song started playing in my head.
“I want to be, the very best! Like no one ever was! Something-something, blah-blah-blah, the power that’s inside!
Doo-doo-doo-doo-doo, something with me and you! Our courage will pull us through! You teach me and I’ll teach you!
I had to search for radiodonts to get images of the oral cones….that’s a whole different sort of animal, all right. Amazing diversity.
If species never died off, can you imagine how crowded this world would be?
Author here – thanks for reading our paper! I share your sentiments completely and actually, I became a scientist because of reading Wonderful Life as a kid. The idea of Opabinia’s descendants becoming a dominant lifeform has been explored in fiction – Neal Shusterman’s short story “Opabinia” and Robert J. Sawyer’s novels “Fossil Hunter” and “Foreigner”.
But that’s not why I’m here!
The artist (Franz Anthony) of this cute picture has asked for the following: There’s a worrying trend where people are mass-stealing art from twitter & selling them on the cryptomarket. This not only lets random users illegally profit from artists’ work, but also has a huge carbon footprint that we can’t tolerate. While the clean, unwatermarked artwork is available to view on the paper, please DO NOT post the clean version anywhere on the internet—at least until this trend dies down.
I posted a watermarked version on Twitter: https://twitter.com/jopabinia/status/1370088306558439426
PZ, if you could please replace with this, it would be most appreciated, thanks.