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Ottoia

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Ottoia was a stem-group archaeopriapulid worm that lived during the Cambrian period.

Ottoia tricuspida ROM 63057
Ottoia tricuspida ROM 63057

This ancient organism was a predator that lived on the ocean floor. It is famous today because of its many well-preserved fossils. Most of these large fossils come from the Burgess Shale in British Columbia, Canada. While some fossils are found in China, the clearest examples are from this Canadian site. Studying Ottoia helps scientists understand how early animals hunted and lived in ancient seas.

The body of Ottoia had a very specific structure. It was bilaterally symmetrical, meaning its left and right sides were mirror images. However, the front end, or anterior, showed radial symmetry.

Ottoia sclerites - schematic
Ottoia sclerites - schematic

A tough outer layer called a cuticle protected the animal and limited its size. The main part of the body, the trunk, was divided into 70 to 100 rings called annulations. These rings changed in spacing depending on how the worm moved or contracted. An internal nerve chord ran down the entire length of the organism.

Ottoia had a specialized way of eating using an eversible proboscis. An eversible part is something that can be pushed outward from the body. This proboscis was located at the front end of the worm. It was covered in an armature of sharp teeth and hooks.

Ottoia prolifica teeth NMNH 198591
Ottoia prolifica teeth NMNH 198591

Scientists have identified two different species based on these teeth: Ottoia tricuspida and Ottoia prolifica. At the base of the pharynx, a ring of spines sat near the teeth. Behind that, a series of hooks and spines were arranged in a quincunx pattern. This pattern looks like the five dots on a single die.

The worm used its body to live a very active life in the sediment. It was a burrower that likely lived in a U-shaped burrow.

Ottoia burrowing
Ottoia burrowing

To move through the mud, it used a series of hooks at its posterior, or back end. These hooks acted as anchors to hold the worm in place while it dug. From the safety of its burrow, it could extend its proboscis to find food. Inside the trunk, a gut ran from the anus to the mouth. A dense group of gut muscles functioned as a gizzard to help process food.

Ottoia was a fierce predator and a scavenger. Fossil evidence shows it often hunted a shelled animal called Haplophrentis. The worm typically swallowed these prey items head-first.

Ottoia burrowing
Ottoia burrowing

Gut contents also show that Ottoia practiced cannibalism. This means they sometimes ate other members of their own species. This behavior is still seen in modern priapulid worms today. By eating both other animals and their own kind, they played a major role in their ecosystem.

We know so much about Ottoia because of how it was preserved. The Burgess Shale was located at the foot of a high limestone reef. Underwater mud avalanches could slide down from the cliffs.

Ottoia tricuspida ROM 63057
Ottoia tricuspida ROM 63057

These slides would quickly bury the worms living on the bottom. This rapid burial prevented them from decaying and kept them intact. In the Greater Phyllopod bed, 677 specimens have been found. In that specific community, Ottoia made up 1.29% of the total animals.

Scientists have found many specimens in various collections. The University of Northern British Columbia (UNSM) holds at least 1,000 specimens. Other large collections exist at the Royal Ontario Museum (ROM). While some reports place Ottoia in places like Spain or Nevada, these are not considered secure. The only truly verified large fossils come from the Burgess Shale. However, tiny microfossils of their teeth are found throughout the Western Canada Sedimentary Basin. These tiny clues help map where these worms once traveled.

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🖼️ Images & Media (4)
File:Ottoia tricuspida ROM 63057.jpg
Ottoia tricuspida ROM 63057.jpg
File:Ottoia sclerites - schematic.png
Ottoia sclerites - schematic.png
File:Ottoia prolifica teeth NMNH 198591.jpg
Ottoia prolifica teeth NMNH 198591.jpg
File:Ottoia burrowing.jpg
Ottoia burrowing.jpg
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