The Cambrian explosion, which occurred around 542 million years ago, is one of the most “impressive” events in the history of life on our planet. A select few species were naturally selected to survive this period, laying the genetic foundation for many current species. Some organisms discovered by researchers from this distant historical stage of Earth still exist today and are considered so bizarre that one might think they could be the work of some mad surrealist artist.
Most Unusual Ancient Creatures
The Cambrian Explosion marks the beginning of the Paleozoic Era (from 542 to 250 million years ago), which is also one of the most exciting and least understood stages in natural history.
There is no doubt that it is a significant moment in natural history; it is even referred to as the “Big Bang of Life”. However, we are still not entirely sure whether it was a singular event. It signifies the time when organisms began to evolve hard body parts like shells, greatly increasing their chances of survival compared to their soft-bodied ancestors, and the fossil record has become much more complete since this time.
Currently, we can only speculate about what might have occurred before this period, and we can only know about these organisms if we find exceptionally well-preserved fossil evidence of them from before the Cambrian explosion. The Cambrian-Ordovician mass extinction event at the end of the Cambrian period (about 488 million years ago) would conclude this experimental era, leaving a relatively small number of living organisms to fight another day.
You are likely eager to see the strangest creatures that evolved during this time. Below is a list of species selected by researchers as the most special organisms.
1. Hallucigenia
This creature is believed to be an early invertebrate.
This cleverly named species was a bizarre form of life that once roamed our planet. It resembles a “hybrid” between a pair of comb teeth and a long-legged worm, and today it truly appears alien, as if it were meant to exist in its time.
This organism was first discovered by Charles Doolittle Walcott over a century ago; he was baffled by its appearance and thought he was experiencing a “hallucination.” Perhaps its name, Hallucigenia (meaning hallucination), could not be more fitting.
Specimens left behind measure only about 0.5 cm to 5.5 cm, living approximately 505 million years ago. Believed to be an early invertebrate, it has 7 to 8 spindly legs with some sharp spines along its back. Specimens of this species have been found in the Burgess Shale of Canada and China from the Cambrian period, some well-preserved or only partially remaining as spines. Initial reconstructions suggested these creatures used spines like some forms of stilts, but paleontologists now believe the spines stood upright from its back.
For decades, naturalists have debated whether Hallucigenia represented a completely new animal from the Cambrian, classifying it in the taxonomic unit called “problematica.” However, this creature is thought to be a member of the extinct lobopodian phylum or a distant ancestor of modern onychophorans.
2. Anomalocaris
This animal was first discovered by Joseph Whiteaves in 1892.
One of the strangest creatures to evolve during this time is the mysterious Anomalocaris. Its name translates roughly to “abnormal or strange shrimp”; this creature was a top predator in its time over half a billion years ago. It is classified as a member of the extinct radiodont genus, an order closely related to modern arthropods. Discovered first by Joseph Whiteaves in 1892, it has a very peculiar shape and body design, yet retains some features we can observe in modern animals today. For instance, its segmented body and its primitive front limbs are not too different from those of modern arthropods.
During its time, Anomalocaris was a true “giant,” reaching lengths of up to 1.83 meters. It was likened to a very skilled swimmer, capable of propelling itself by undulating small flexible fins along the length of its body.
The relatively large front limbs were likely used for hunting and bringing prey into its unusual disc-shaped mouth located on the underside of its head. Compared to its contemporaries, this creature had exceptional vision, utilizing complex compound eyes capable of viewing like modern dragonflies.
The mouth of Anomalocaris was made up of 32 overlapping plates that researchers believe could easily crush prey. Several specimens have been found with fossilized remains of trilobite crustaceans in their stomachs, a clear indication of its predatory and carnivorous capabilities.
3. Kerygmachela
Kerygmachela lived about 520 million years ago and had a rather frightening appearance.
Kerygmachela is likened to the “more beautiful” cousin of Anomalocaris. It lived about 520 million years ago and had a rather frightening shape. It resembles a gilled lobster found in the Buen Formation of the Sirius Passet Lagerstätte in Greenland in 1993. Its unique body shape led scientists to classify it as a relative of other organisms like Anomalocaris, and it might be a distant ancestor of true arthropods today.
Its name relates to its rather elegant and exaggerated front appendages. These appendages end with a series of rather unpleasant-looking spines believed to be used for capturing its prey. It is predicted to have had stalkless compound eyes or slit-like eyes located just behind the point where its large appendages connect to its “head.” Its small mouth would face forward and lie beneath its head, equipped with a pair of structures resembling environmental sensing devices.
This creature may also have had a swimming style similar to Anomalocaris. A notable feature of this animal is its long tail spine, long thought to be a type of sensory organ called cerci, though there are ongoing debates about what this organ was actually used for.
4. Marrella
Marrella resembled a small animal, measuring about 2 cm long.
Marrella is another monster of nature, existing around 520 million years ago, it is an extinct genus of arthropods. Marrella is one of the most commonly found organisms in the Burgess Shale, first discovered in 1909.
Marrella resembles a small animal, measuring about 2 cm long, and is one of the “better” preserved animals from this period. This creature carries a pair of antennae and spines at its head, directed backward, and has about 25 different body segments, each with its own pair of legs. These are among the few genera from the Cambrian explosion that survived the mass extinction event marking the end of the Cambrian period, continuing to exist until the Devonian period (around 419 to 359 million years ago).
5. Opabinia
Opabinia is believed to be closely related to Anomalocaris.
Opabinia looks like a strange organic vacuum cleaner, with five eyes, a longitudinally split body, and a segmented structure, regarded as one of the strangest evolutionary experiments of the Cambrian explosion. It was first discovered in the Burgess Shale in 1912, measuring about 7 cm in length and living approximately 505 million years ago.
Opabinia is believed to be closely related to the previously mentioned Anomalocaris. According to researchers, this creature would use its bizarre frontal nozzle to funnel food into its backward-facing mouth. This is also one of the less common organisms preserved in the Burgess Shale, and to date, only about 20 identifiable specimens exist. Scientists are also uncertain about the lifestyle of Opabinia, but it is likely that it roamed the ocean floor to hunt smaller creatures, possibly acting as a “scavenger” in the ocean.
6. Habelia
This is a predatory species that migrated throughout the oceans.
Habelia is considered the early ancestor of the formidable sea scorpion, first discovered in 1912 with over 50 specimens collected. This predatory species migrated across the oceans and lived about 508 million years ago in what is now the Rocky Mountains of Canada. For a long time, Habelia represented one of the most difficult specimens to classify until recently.
This peculiar creature is about 2 cm long, surrounded by a sturdy exoskeleton, well-equipped for a hunter’s life. One of its notable features is its large jaws, technically called gnathobases, located beneath its large head shield, along with long dorsal spines on its thorax and a long spine on its tail.
Recent studies and reconstruction efforts of this creature suggest that it had a jaw structure resembling that of a Swiss Army Knife, capable of performing tasks similar to the various teeth found in mammalian jaws. These different tools were an adaptation for feeding on hard-shelled prey.
Examination of specimens shows it had well-developed limbs on its thorax, perfectly adapted for swift movement across the ocean floor. These creatures could hunt and kill smaller or juvenile prey, such as trilobites or other small hard-shelled organisms.
7. Pikaia
This organism existed about 530 million years ago.
Pikaia is truly one of the most peculiar creatures on this list. It is extremely interesting as it is the most primitive vertebrate known, making it the most distant ancestor of all living vertebrates today. Pikaia, first discovered in the Burgess Shale in 1911, is one of the least preserved species from the fossil formation.
This creature existed approximately 530 million years ago and is one of the best-studied among all fossils preserved from this period. Belonging to the phylum Chordata, it resembles the modern lancelet and could swim in a manner similar to eels. It measures about 3.8 cm in length, with an elongated body resembling a fish and a poorly defined head structure.
It also possessed two long, antenna-like tentacles protruding from the front of its “head,” and a series of short appendages beneath that could function as primitive gills. Although it is a creature from the most primitive times, Pikaia demonstrates the essential prerequisites for vertebrates, including a notochord—a flexible “rod” found in chordates that later develops into the spine of vertebrates. Specimens also show a nervous system and circulatory system, other critical structures of vertebrates.
During its existence, Pikaia would resemble a leaf-shaped creature with an expanded tail fin. Its flattened body is divided into pairs of segmented muscle blocks, which could be regarded as faint vertical lines. The modern Branchiostoma is thought to be the closest relative to Pikaia.
8. Wiwaxia
It resembles a dome covered in armored plates with protruding blades.
Wiwaxia appears to be like half a coconut covered in spines, one of the particularly strange organisms from this period. It looks like a dome covered in armored plates with protruding blades resembling swords. The relatively small specimens provide sufficient evidence for scientists regarding the life stages of this creature. There remains some debate over whether to classify it as an ancient worm or a type of mollusk.
9. Aysheaia
Aysheaia measures between 1 to 6 cm in length.
Aysheaia resembles a terrifying parasitic creature, existing between 570 to 500 million years ago, measuring between 1 to 6 cm in length. It belongs to the phylum Onychophora and has some common features with velvet worms and tardigrades. Its entire body has ten pairs of limbs filled with spines and claws, along with a ring of appendages resembling fingers around its mouth and two appendages on its head. It is believed to have fed on sponges during its lifetime or evaded predators by living among sponge colonies. Its appearance also bears similarities to modern lampreys, which are omnivorous creatures.
It is evident that the Cambrian explosion was one of the strangest periods in Earth’s natural history and laid the foundation for many species of animals that still exist today. And surely, with the images you see of these creatures from this period, they appear as alien as they do strange.
