. How did early animals evolve heads? A scientist at the University of Cambridge, England believes that the discovery of an 500 million year-old fossilised brain could provide clues to how early animals evolved their heads. Javier Ortega-Hernandez (a postdoctoral researcher at Cambridge’s Department of Earth Sciences) and his colleagues discovered a crucial point in evolution from soft body to hard body during the early ancestors of the arthropods (the group that includes modern spiders and crustaceans). His findings were published in Current Biology by Dr. Javier Ortega-Hernandez. He examined two kinds of arthropod ancestrals: a bizarre creature that looked almost like a submarine and a soft-bodied trilobite. An arthropod that resembles a submarine, Odaraia Alata from the middle Cambrian Burgess Shale. Image: University of Cambridge. He discovered that their anterior sclerite, a hard plate and the eye-like features on the front of their bodies were linked by nerve traces from the brain’s front. This corresponds to how arthropods view the world. New comparisons were made with large-sized swimming predators from the same period, the anomalocaridids. He found important similarities in the anterior sclerite to a plate on top of the anomalocaridid’s head. This suggests that they had an ancestor. Although most experts agree that anomalocaridids were early arthropod relatives, the bodies of these species are quite distinct. Scientists can recognize the anterior sclerite thanks to preserved brains found in fossil specimens. This bridge is between anomalocaridid’s head and the heads of jointed arthropods that we are familiar with. Transition from soft bodies to hard Dr Javier Ortega Hernandez said that the anterior sclerite is embedded in the body’s anterior sclerite. Similar to modern arthropods, the photoreceptors connect to the brain’s anterior portion. Image from cell.com It is likely that these brains were able to process data in a similar way as modern arthropods and are essential for interfacing with the environment and finding food. Cambrian Explosion Arthropods were formed around 500million years ago. This was during the Cambrian Explosion which is known for rapid evolution and a time of high evolutionary change. The Cambrian Explosion was the first time that animal life on Earth had evolved from soft-bodied organisms, such as jellyfish and algae. The fossils are from the Smithsonian Institution, Washington DC, and Royal Ontario Museum, Toronto. They were found in the Burgess Shale, Western Canada. This is one of the most important fossil resources of that period. It is difficult to understand how brains developed, as they are made up of soft tissue that contain fatty-like substances and do not fossilize well. It is rare to find brain tissue even in areas like the Burgess Shale where there are many soft tissue fossilised specimens. Dr. Ortega Hernandez stated that “heads have become more complicated over time.” What we are seeing is an answer for the question “How arthropods transformed their bodies from soft and hard?” The research was supported by Emmanuel College in Cambridge. Separately, Dr. Martin Smith (Junior Research Fellow, University of Cambridge’s Department of Earth Sciences) announced that his research team has discovered a new type of Penis Worm. It was also found in Burgess Shale. The fossil existed 500 millions years ago. The fossil could open its mouth and reveal a small, toothless throat that resembled a cheese grator. Citation: Javier Ortega Hernande, “Homology in Burgess Shale Euarthropods.” Current Biology. DOI: 10.1016/j.cub.2015.04. 034.
