Title photo by Dotted Yeti

Travel back in time to the Cambrian Era, a period famous for the diversity of its life forms!

Lasting approximately 53.4 million years from the end of the preceding Ediacaran period 538.8 million years ago (mya) to the beginning of the Ordovician period 485.4 mya. It is a period where the atmosphere had elevated concentrations of oxygen, and the global temperature increased-creating a temperate world

Geological timescale from here

Scientists believe that the higher oxygen levels, and warmer climate contributed to the incredible diversity of life that occurred in the oceans.

However, on land it was mostly barren…complex lifeforms were non-existent and would have been restricted to mollusks and arthropods emerging from the water to feed on microbes in slimy biofilms

The Cambrian is unique as it had unusually high deposits of Lagerstätte sedimentary deposits, these sites offer exceptional preservation of ‘soft’ organism parts, as well as their harder shells which means that the study and understanding of the fossilized life forms surpasses some of later periods

(above, from my previous post on Aysheaia)

Anomalocaris means ‘unlike other shrimp’ or ‘abnormal shrimp’ and is an extinct Cambrian arthropod belonging to the radiodonts (meaning, radius ‘spoke of a wheel’ and odoús ‘tooth’) and is thought to have been one of the top predators for it’s time

The fossils that were discovered in The Burgess Shale in 1886 were of incomplete segments and were initially thought to be 3 separate individual species. The frontal appendages were thought to be the bodies of shrimp-like crustaceans.

Above, ‘named Anomalocaris (“strange shrimp”) by Walcott’

The circular mouth part was thought to be a jellyfish as it showed the same radial symmetry

Above, ‘circular fossil from the Burgess Shale formation was described and named Peytoia’

In 1966 a comprehensive revision of the Burgess Shale fossils began, along with additional misinterpretations which proposed that the feeding appendages were legs, and the mouth parts were part of a sponge…

However, during the cleaning of one of the fossils a layer of stone was removed which linked the feeding appendages and the mouth parts as belonging to the same animal. Later specimens showed how the feeding appendages could be curled around prey and directed to the circular mouth part, as well as eyes on flexible stalks…It had taken over 100 years of misinterpretations to finally meet Anomalocaris

Above, previously thought as the ‘body of a shrimp was one of a pair of spiny grasping arms…the rim of the mouth shows partially, as does one of the large eyes’ source

Above, ‘appendages could curl, enfolding around prey, which was pinned by the arm spines. The captured prey was then placed into the mouth, which was under the head between the eyes. The eyes were at the ends of flexible stalks.’ source

In 2021 the compound eyes made up of 16,000 lenses were discovered, proving that Anomalocaris was definitely an arthropod, and indicating that complex eyes has evolved before jointed legs or exoskeletons

Above photo by John Paterson, ‘One of the stalked eyes of Anomalocaris from South Australia with arrows pointing to the boundary between the stalk and visual surface, plus the intricate lenses preserved’

The Anomalocaris would have been huge for the Cambrian maybe up to 1 metre in length. It would have been able to swim through the water by undulating the flexible flaps on the sides of it’s body chasing down prey. The compound eyes would have given it a ‘high degree of visual acuity, and a well-developed brain to process that information’ source

Above, Anomalocaris size via wikipedia

It’s unusual mouth parts made of wrinkled structures and sharp teeth, plus grasping appendages would have been ideal to catch and eat soft bodied animals like worms or comb jellies

Above, Radiodonta oral cones wikipedia…looking rather like an anus with teeth, imo

Above image by Junnn11

Anomalocaris fossils have been discovered in Canada (Burgess Shale), Australia (Emu Bay Shale), China and the US and include species

-A. canadensis Whiteaves, 1892

=A. whiteavesi Walcott, 1908

=A. gigantea Walcott, 1912

=A. cranbrookensis Resser, 1929

-A. daleyae Paterson, García-Bellidob & Edgecombe, 2023 wikipedia

Plus 8 other species including

  • Anomalocaris saron, from the Chengjiang lagerstatten in China source

Above, Anomalocaris saron, a Radiodonta from the Chengjiang Biota, China

The Anomalocaris died off towards the end of the Cambrian, during the Great Permian Extiction along with up to 90% of all other life forms

Above image by Dotted Yeti

All info from wikipedia, and also here, here and here

As always, I am not an expert, I just enjoy learning and sharing interesting things…Any mistakes- leave a comment and I’ll edit my post