For the first exhibit in Blathers’ Expanded Museum, we have a Cambrian mystery animal: Anomalocaris.
“Anomalocaris lived in the water long before the dinosaurs and are known for their, er, “distinctive” look. Flat bodies over three feet in length, bulging eyes like a…dragonfly, antennae like shrimp tails… They looked so peculiar that people originally thought they were multiple fossils stacked on top of each other! As a delightful side note, “anomalocaris” means “abnormal shrimp.” Obviously this animal has a certain reputation in the scientific community!” — Blathers, Animal Crossing: New Horizons
What’s a shrimp, a sea cucumber, a sponge, and a jellyfish all rolled into one animal? Not Anomalocaris, but I’d like to see what you come up with…
Anomalocaris is an extinct genus of animals that lived in the Cambrian period — about 530 million years ago. As Blathers says, it is known in the paleo community for its bizarre appearance and a history of being misidentified. After many different theories, we now know Anomalocaris was actually a group of some of the largest animals of the Cambrian, and likely included some of the earliest apex predators. Coming face to face with one would have given you quite a scare! Besides its startling looks, some species reached lengths as great as 2 metres. Definitely not something I would want to encounter on my beach holiday.
There are several species of Anomalocaris identified, but all look fairly similar. Based on the fossil in the New Horizons, I would guess that Blathers is displaying a nearly complete specimen of Anomalocaris canadensis. This was the first species of Anomalocaris that was identified, named, and described. The fossil in the game shows the grasping claws hanging down at the front, the stalked eyes, body lobes, and part of the tail vanes.
Anomalocaris didn’t have a shell, but was a soft bodied animal (like a fish). The feeding claws and mouth were likely the hardest parts of the body, which explains why they are the most frequently found: they were preserved when the rest of the body decomposed or was eaten. Anomalocaris have been found in the Canadian Rockies, Australia, the USA and China, suggesting that they had a wide range in the early seas.
For many years it has been thought that Anomalocaris was a specialized hunter of trilobites, the photogenic pillbugs of the Cambrian and beyond. More recent studies have focused on the claws and mouthparts of the different species of Anomalocaris, and suggest that their feeding habits were more varied. Some argue that it is unlikely they hunted shelled creatures such as trilobites, as they lacked mouthparts hard enough to crush the shells. These researchers suggest Anomalocaris probably hunted soft-bodied swimmers, or slurped burrowers out of the sediment on the seafloor. Other paleontologists point to variations in the feeding arms and mouth shape, suggesting that some species were filter feeders. Well developed eyes with colour vision in some specimens support the idea that other Anomalocaris species were apex predators.
We know a lot about it now, but when people first discovered Anomalocaris fossils they had no idea what to make of them. A bit here, a part there… it was like finding single pieces of a puzzle. Without the picture on the lid of the box, and with many puzzles mixed up together in several different bags, it’s no wonder that people put the pieces together incorrectly, or missed that there was a larger picture at all. Parts of Anomalocaris fossils have been variously misidentified as shrimp, jellyfish, sea cucumbers, and the combined fossil of a jellyfish and a sponge.
Anomalocaris gets its name, “unlike other shrimp”, from fossils of the “antennae” (as Blathers describes them) identified in 1892 . These “antennae” are actually grasping arms joined to the head near the mouth. In the first fossils found, these appendages were preserved without the rest of the body, and were misidentified as the headless bodies of phyllocarids (a subclass of shrimp-like creatures). Even then, Joseph Whiteaves, the paleontologist who described and identified these fossils, noticed something off and named them for their dissimilarity to other phyllocarids. When more specimens were available another paleontologist, Derek Briggs, took it further, and suggested that these fossils were not the headless bodies of a small animal, but actually the legs of some larger, unidentified arthropod.
When the paleontologist Charles Walcott first saw Anomalocaris jaws in the fossils his team brought back from the Rocky Mountains in the early 1900s, he thought it looked like the underside of a squashed jellyfish, trailing tentacles. He called this theoretical jellyfish Peytoia. This identification made sense with the information he had available; what we know today as Anomalocaridids belonged to the order Radiodonta, meaning “radiating teeth”. Their jaws were round, and look a bit like a slice of cored pineapple (or a squashed jellyfish) in the fossil record. It wasn’t until they were seen in better preserved fossils that these fossils could be correctly identified.
Laggania cambria is a fossil Walcott originally interpreted as a sea cucumber (it showed a round jaw and a sack-like body), but was later reinterpreted as a compound fossil of a Peytoia (the jellyfish/jaws) and a sponge, superimposed in death and looking like one creature. Later specimens showed without doubt that the two parts belonged together, but it was going to take more information to realize what the parts preserved in these fossils actually were.
So how did all the parts come together? In 1981, nearly 100 years after the original fossil parts were found and described, a paleontologist working at the Royal Ontario Museum found a fossil that put the parts together. Harry Whittington was describing and preparing a fossil of an unknown appendage found in the Canadian Rockies. When he uncovered the entire fossil, he discovered an already-assembled part of the puzzle of Anomalocaris. The shrimp-thing then known as Anomalocaris was connected to a head, with another Anomalocaris-shrimp on the other side of the head. Peytoia also made an appearance — positioned like a circular jaw, not a jellyfish at all.
For a picture of the fossil he uncovered, visit the ROM’s online fossil gallery. It’s designated GSC#75535.
I can’t imagine how exciting that must have been. Probably much like scratching a lottery card and, one at a time, uncovering winning number after winning number (though I’ve never done that, either). Whittington then went back to other fossils Walcott had collected from the same area, and uncovered portions that had been obscured by rock. He found well preserved bodies and heads of this new creature, allowing him and Briggs to form a picture of Anomalocaris similar to what we know today.
Since then many more fossils have been found, including complete and nearly complete specimens. Our models of Anomalocaris now include the round jaws with radiating teeth on its underside, the grasping claws on the front of its head that probably hung back near the head until extended in a hunt, and the segmented body with gilled, fin-like lobes. Computer models and robotic recreations of the animal show us that it likely moved the overlapping lobes in a wave-like pattern to swim, much like the way a cuttlefish’s fin moves. Its tail had flat vanes, splaying out from the posterior. We also know that Anomalocaris had well-developed and complex eyes: well preserved specimens discovered in 2014 show over 16,000 lenses in a single eye, rivaling modern arthropods like dragonflies.
Putting together all the pieces into a (we think) complete picture, we can now say Anomalocaris was a large swimming animal. It was fast and maneuverable, with very sharp eyes and wicked grasping claws at its front. It’s classified as an euarthropod (it was an arthropod before being an arthropod was cool) meaning that it’s like a really early, really big lobster, or maybe a giant waterbug. Whether they hunted swimming things, crawling shelled things, or filtered water for plankton, these creatures are some of the weirdest and fiercest-looking of the early ocean.
References:
ROM. “Anomalocaris – Fossil Gallery – Burgess Shale.” The Burgess Shale, ROM, 2011, https://burgess-shale.rom.on.ca/en/fossil-gallery/view-species.php?id=1&m=5&&ref=i. Accessed 13 January 2021.
Collins, Desmond. “The ‘Evolution’ of Anomalocaris and Its Classification in the Arthropod Class Dinocarida (Nov.) and Order Radiodonta (Nov.).” Journal of Paleontology, vol. 70, no. 2, 1996, pp. 280–293. JSTOR, http://www.jstor.org/stable/1306391.
Paterson, J., García-Bellido, D., Lee, M. et al. Acute vision in the giant Cambrian predator Anomalocaris and the origin of compound eyes. Nature 480, 237–240 (2011). https://doi.org/10.1038/nature10689
Lee, M., Jago, J., García-Bellido, D. et al. Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia. Nature 474, 631–634 (2011). https://doi.org/10.1038/nature10097
Gon III, Sam. Anomalocaris homepage. website. Accessed January 14, 2021. http://www.trilobites.info/anohome.html
Van Roy, P., Daley, A. & Briggs, D. Anomalocaridid trunk limb homology revealed by a giant filter-feeder with paired flaps. Nature 522, 77–80 (2015). https://doi.org/10.1038/nature14256
Vinther, J., Stein, M., Longrich, N. et al. A suspension-feeding anomalocarid from the Early Cambrian. Nature 507, 496–499 (2014). https://doi.org/10.1038/nature13010
Images:
Junnn11, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
Image of Anomalocaris fossil from Animal Crossing: New Horizons Nintendo
James St. John, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
Charles Doolittle Walcott, Public domain, via Wikimedia Commons
Gaetan Lee from London, UK, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
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