Buzz
Approximately 540 million years ago, a remarkable event unfolded—a burst of creativity rather than destruction. This era, referred to as the “Cambrian explosion,” represents a short but transformative period when life diversified into countless new forms.
During this time, many recognizable life forms appeared, but it was also a period of bold evolutionary experimentation. Unique and unusual body structures emerged, though many of these oddities eventually vanished. Today, their preserved remains can be found in Canada’s Burgess Shale.
The Burgess Shale holds immense scientific significance, not just due to its ancient age but also because of the extraordinary fossils it contains. Unlike most fossil sites, which primarily preserve hard structures like bones or shells, this location captures much more.
Remarkably, the Burgess Shale fossilized even the most delicate and perishable parts of organisms. This occurred as mudslides from an underwater cliff buried sea creatures, preserving them in exquisite detail for millions of years.
Below are 10 of the most peculiar creatures unearthed in the shale.
10. Aysheaia
Aysheaia is a tiny creature lacking any hard body structures. Without the exceptional preservation conditions of the Burgess Shale, it’s improbable that we would have any fossil evidence of this fascinating organism. Measuring about 5 centimeters (2 inches) long, it featured 10 pairs of short, spiky legs.
Despite its small size, Aysheaia was a predator. Its fossils are frequently discovered alongside sponge remains, suggesting it lived on sponges and hunted other creatures inhabiting them. It may have also used sponges for shelter, as larger predators roamed the seas 505 million years ago.
This worm-like creature is closely linked to a modern group of animals. Onychophora, or velvet worms, now inhabit land in various regions worldwide. It appears that Aysheaia’s descendants were among the earliest animals to transition to terrestrial life.
9. Nectocaris
Even with the exceptional preservation of Burgess Shale fossils, there’s often debate among paleontologists about the true nature of the creatures they uncover. Soft-bodied organisms buried under layers of mud can become so distorted that their fossilized forms bear little resemblance to their original appearance. This was the case with Nectocaris.
Initially, the sole Nectocaris fossil led scientists to believe they were examining a type of swimming shrimp (as its name suggests). Others speculated it might be more closely related to vertebrates. However, recent research suggests it was something far more unusual.
The identification of 91 additional Nectocaris fossils allowed researchers to conclude that this creature was the earliest known cephalopod, akin to modern squids or octopuses. Its peculiar front appendages are now recognized as tentacles, and its head featured stalked eyes. A cone-shaped structure underneath likely functioned as a propulsion system, enabling quick bursts of speed by expelling water.
8. Marrella
Marrella splendens is arguably the most stunning organism discovered in the Burgess Shale. Its name reflects its beauty—splendens translates to “beautiful” in Latin.
Marrella demonstrates that extraordinary things can come in tiny forms. This delicate lace crab measures just 25 millimeters (1 inch) in length. Its antennae consist of approximately 30 segments, while its body has 26, each adorned with large spines. Every body segment features a pair of legs equipped with gills, allowing the creature to breathe by moving its legs.
Scientists believe Marrella either preyed on smaller organisms or fed on organic debris that settled on the seafloor. Its most distinctive feature, the large curved spikes, likely served as a defense mechanism against predators. If a predator couldn’t fit Marrella into its mouth, it couldn’t consume it.
7. Canadia
The fossils of Canadia resemble a feather boa trapped in wet mud. In reality, this creature likely looked like a swimming feather boa during its lifetime.
This small, bristled worm measured about 4 centimeters (1.6 inches) in length. Its body was covered in bristles known as setae, which functioned like paddles to help Canadia swim by undulating its body.
At the front of the organism, a pair of tentacles allowed Canadia to explore its surroundings. Beneath its head was a proboscis, which it likely used to consume food.
The proboscis was created by a section of the gut extending outward from the organism. Canadia might have been a flamboyant predator, but it likely consumed both living and dead animals that came within reach of its tentacles.
Concealed beneath its bristles were short limbs, enabling Canadia to crawl along the seabed.
6. Pikaia
Meet one of your earliest relatives. Pikaia is among the first organisms identified with a structure resembling a backbone. This suggests that Pikaia, or a similar creature, is likely the ancestor of all chordates (animals with spines), including fish, reptiles, and mammals. Its elongated, eel-like body is marked by muscular bands, a characteristic shared by chordates.
While many take pride in their ancestors, Pikaia isn’t exactly a creature you’d want to display on your wall. Its head lacks eyes, featuring only two tentacle-like structures for sensing its environment.
While Pikaia likely swam through ancient seas, its gut contained sediment from organic matter found on the seabed. This suggests that all of humanity may have descended from a scavenger that fed on the ocean floor. How times have changed.
5. Opabinia
When a modern reconstruction of Opabinia was unveiled at a 1972 scientific conference, it was met with laughter. The reason is clear: it boasts five eyes on short stalks, a broad, flat head, and a long, flexible proboscis extending from its front.
With its peculiar appearance, Opabinia has become synonymous with the oddities of the Burgess Shale. Its lack of resemblance to any living creature made it difficult for scientists to classify or even hypothesize its lifestyle. Some speculated it might have swum upside down.
The proboscis of Opabinia is four times the length of its head and remarkably flexible. Fossils reveal this appendage in various positions and shapes, with its tip ending in claw-like fingers covered in spines, designed for grasping.
Many creatures likely appeared shocked to meet their death at the hands of such a bizarre animal. Opabinia propelled itself through the water using body fins, capturing soft prey with its proboscis and delivering it to its mouth.
4. Wiwaxia
The primordial oceans teemed with predators, prompting the rapid evolution of defensive traits to help creatures avoid becoming prey.
Wiwaxia resembles a slug, though unlike any modern species. Scientists continue to debate whether it is more closely related to mollusks or worms, but its lifestyle was likely similar to that of a slug.
It likely crawled across the seafloor, feeding on bacterial mats that covered the ocean bed. Wiwaxia had a concealed mouth on its underside, equipped with tough plates for grinding food.
Except for its underside, Wiwaxia’s body was covered in scales and spines, with two rows of spines protruding from its back. These were undoubtedly defensive, though their effectiveness is questionable, as many fossils show broken spines and scales, indicating predators could overcome them.
3. Hallucigenia
Few creatures live up to their name as well as Hallucigenia. Named for its bizarre appearance, this fossil has baffled paleontologists. Measuring 1 centimeter (0.4 inches) long, it features flexible appendages on one side and a double row of conical spikes on the other.
Initially, scientists believed Hallucigenia walked on its spikes, resembling a worm on stilts. However, further examination revealed that the tentacle-like structures on its back were actually its feet, and what was thought to be its back was its underside. The spikes served as protection for this tiny organism.
Another mystery was only recently resolved. After determining how Hallucigenia walked, researchers still needed to identify which end was its head and which was its tail.
What was initially mistaken for its head—a dark mark on the fossil—turned out to be a stain from its guts being expelled after death. The true head was found on the opposite end, featuring a pair of eyes and what appeared to be a playful grin.
2. Anomalocaris
Scientific progress is often challenging and nonlinear. Researchers interpret evidence as best they can, but when evidence is incomplete, their conclusions may be far from accurate. Over time, they refine their understanding by reassessing the facts. Anomalocaris led scientists on a complex journey before they finally understood its true nature.
The name Anomalocaris, meaning “unlike other shrimp,” was given because its initial fossil fragments were mistaken for shrimp tails. Other parts were misidentified as jellyfish. It wasn’t until larger, more complete fossils were discovered that the puzzle was solved.
Anomalocaris was the apex predator of its time. A complete fossil measures 25 centimeters (10 inches), but fragments suggest it could grow up to 1 meter (3 feet) long.
Its body was built for swimming freely in search of prey. The shrimp-like fossils were actually its head appendages, used to grasp other organisms. What was thought to be a jellyfish turned out to be its mouth.
1. Ottoia
Ottoia is the most frequently discovered worm in the Burgess Shale fossils. Research suggests a connection to priapulid worms (also known as penis worms), making Ottoia a particularly formidable example of its kind.
Measuring around 15 centimeters (6 inches) in length, Ottoia featured a retractable proboscis lined with 28 rows of hooks. This structure, formed from its gut, was used to capture and consume prey.
Fossils often depict Ottoia in a U-shape, possibly reflecting its posture while hiding in burrows. Despite this, it was a carnivorous hunter, emerging from its burrow to seek food.
One fossil reveals nine Ottoia feeding on a deceased organism. The preservation is so exceptional that the last meals of some Ottoia can be identified, including one instance where a Ottoia had consumed another of its kind, confirming their cannibalistic nature.
