In the heat of the rather suitably named Death Valley, researchers think they may have uncovered one of the earliest ever mass animal strandings. Preserved in the rock for some 540 million years, the remains of the smack of jellyfish could provide us with a better understanding about what life was like not in the oceans, but rather on land back then.
When the jellyfish found themselves in their awkward predicament, Death Valley was not the scorching desert it is today, but instead an intertidal zone. The fact that in the modern day this habitat is exploited by a massive range of animals from all major groups reflects its importance to life. Yet fossil evidence of this environment is rare and hard to come by, meaning that those that are found provide an incredible window into the paleobiology of these regions.
When researchers found a small meter-squared section of rock containing the remains of 13 jellyfish frozen in time, the significance was not lost on them. As reported in Geological Magazine, it appeared to show how a group of Cambrian medusozoa, or “jellyfish”, got swept up and out of the shallow sea as waves lapped them closer to the beach and left them stranded on the shoreline.
This in itself indicates that the jellyfish cruising the seas hundreds of millions of years ago behaved in a similar way to those that continue to do so today, aggregating in groups as they bob around looking for plankton to feed upon. But the remains also hint at what things were like above the water.
The fascinating thing about these fossils is how they came about in the first place. The preservation of soft-bodied organisms are rare enough in itself due to the fragility of such animals and the intensity of the fossilization process. However, if a load of jellyfish were to be washed onto a beach in modern times, it is unlikely anything would be left behind to be fossilized in the first place, as scavengers would more than likely pick them apart and eat them.
So how did a baker’s dozen of jellyfish come to be stuck in time to be dug up 540 million years later? Well the researchers suspect that it is because there were simply few or even no terrestrial animals about at the time to destroy them. In addition to that, they also think that the beaches were likely covered in thick microbial mats that would also have helped form a crust around the jellyfish, aiding the chance they would eventually be preserved.
[H/T: New Scientist]