Community College (LRCCD)

Geology & Earth Science Instructor: Arthur Reed, P.G.



Happy Fossil Friday!

Friday April 9, 2021




Who developed sight first, the Hunter or the Hunted?


Complex animals first showed up in the fossil record beginning in the Cambrian, that time in geologic history known for the ‘explosion of life’. A particular predator at the time is speculated to have developed eyesight far exceeding other contemporary creatures. Additionally, this creature, named Anomalocaris’ briggsi, was an apex predator that was in an evolutionary race.  Those creatures that developed better sight would be the hunters, those with lesser or no sight would be the hunted.


Following is a summary of research published last year in the Journal of Science Advances


This ancient bottom feeder could have ‘invented’ modern sight.

If you like seeing defined shapes, you should thank this little fellow.

Alexandru Micu by Alexandru Micu


 December 4, 2020


A new paper examines how life first developed advanced eyes and sight, and how this led to an “evolutionary arms race” around 500 million years ago. The findings rely on radiodont fossils, a group of arthropods that were abundant in the ocean at the time.


Artist’s reconstruction of ‘Anomalocaris’ briggsi., Sea Monster


The radiodont order, meaning “radiating teeth”, is comprised of many species with a similar body layout — a head and a pair of segmented limbs that would capture prey. They had circular mouths with sharp, serrated teeth, and were roughly squid-shaped. They likely inhabited the deeper layers of the ocean, at around 1000 meters in depth. Due to the low light levels there, they evolved large, sophisticated eyes in order to catch prey. But this ‘sensor’ upgrade would send ripples throughout life on the planet, the authors explain, making vision a driving force in evolution as it pitted predator against prey.

See food, eat food

“Our study provides critical new information about the evolution of the earliest marine animal ecosystems,” said Professor John Paterson from the University of New England’s Palaeoscience Research Centre, lead author on the study.

“In particular, it supports the idea that vision played a crucial role during the Cambrian Explosion, a pivotal phase in history when most major animal groups first appeared during a rapid burst of evolution over half a billion years ago.”

The development of complex eyes allowed animals to perceive their surroundings better than ever before, which also helped predators spot prey more easily. But sight can also warn the hunted of the hunter, so it became a very powerful driver of evolution — after all, the one with poorer sight might not make it through the day. It has retained its importance up to today when virtually every ecosystem and ecological interaction on the planet is shaped by sight.



Acute zone–type eye of ‘A.’ briggsi. Image credits John R. Paterson, Gregory D. Edgecombe, and Diego C. García-Bellido, (2020), Science Advances.


The fossils used in this study were first unearthed around a century ago at Emu Bay Shale on South Australia’s Kangaroo Island and were comprised of isolated body parts. However, initial attempts to reconstruct the animals based on their fossils were quite unsuccessful and resulted in several “Frankenstein’s monsters”, the authors note. Over the decades, as more radiodont material was discovered, including whole bodies, we’ve gained a better understanding of these animals, their body structure, diversity, even possible lifestyles. Still, the specimens from Emu Bay Shale had some unique properties.

“The Emu Bay Shale is the only place in the world that preserves eyes with lenses of Cambrian radiodonts. The more than thirty specimens of eyes we now have, have shed new light on the ecology, behavior, and evolution of these, the largest animals alive half-a-billion years ago,” says Associate Professor Diego García-Bellido from the University of Adelaide and South Australian Museum, a co-author of the paper.

The team worked with these fossils before. They published two papers describing the fossilized eyes recovered from the site. The first one looked at isolated eye specimens of up to one centimeter in diameter, which remain unassigned to a species up to now. The second paper analyzed the eyestalks of Anomalocaris, a top predator in its day that grew up to one meter in length. The current paper, according to the authors, identifies that first, unknown species: ‘Anomalocaris’ briggsi, a new genus that “is yet to be formally named,” Prof. Paterson said.


Acute zone–type eye of ‘A.’ briggsi. Image credits John R. Paterson, Gregory D. Edgecombe, and Diego C. García-Bellido, (2020), Science Advances.


“We discovered much larger specimens of these eyes of up to four centimeters in diameter that possess a distinctive ‘acute zone’, which is a region of enlarged lenses in the center of the eye’s surface that enhances light capture and resolution.”

The large lenses of these animals suggest that they could work in the dim light of the deep sea, and were likely very similar to those of modern amphipod crustaceans (a type of prawn-like creature). Anomalocaris briggsi primarily hunted plankton by filtration through its appendages; its eyes helped it spot its meals from the bottom of the ocean.




Top of Form

























Flag Counter