What are fossils and what do they tell us?

There was an interesting piece of news reported by several international media houses lately. Back in 2006, a group of summer campers from Hamilton Junior Naturalist Club of New Zealand had gone on a trip to a harbour on North Island, hoping to find some small shellfish fossils. Instead, they discovered a well-preserved skeleton of a new species of giant penguins that used to inhabit the area some 27 to 30 million years ago! Scientists published detailed findings in the Journal of Vertebrate Palaeontology on September 16, 2021, saying that the discovery has traced back the history of penguins to the age of dinosaurs. All this was possible because of the fossil.  

What is a fossil?  
Fossils are geologically altered remains of once-living organism and/or its behaviour. There are two main types of fossils: ones that show all or part of the organism’s body, and another showing evidence of the organism’s behaviour. The study of fossils is called palaeontology, from Greek ‘paleo’ meaning ‘ancient’, ‘onto’ meaning ‘being’, and ‘logy’ meaning ‘study’.  Scientists who study fossils are therefore called palaeontologists. Fossils are very important for geologists as they can help determine the age of a particular rock or identify the environment around.  

How do fossils form? 
All living things, — animal, plant, bacteria or fungus — has the potential to become a fossil. The hardest, most resilient parts of animals and plants become fossils, usually when they die quickly and get buried under snow that turns to ice or volcanic ash, or the bodies remain between rocks that solidify around them, or the body deposits in an underwater environ where the water chemistry helps in preserving bodies. Bones fossilise better than flesh and organs because fewer predators and scavengers eat bones. Besides, they are more resistant to physical and chemical destruction. As a result, organisms like jellyfish, with no hard parts like bones or shells, rarely fossilise. 

Can more than one organism fossilise? 
Occasionally the environment is just right to preserve complete ecosystems. These locations are called lagerstätten, a German word meaning ‘storage place’. These fossil sites are important to scientists as they tell us how the animals and plants lived and died there. Western Australia’s Gogo Formation is co one such lagerstätten zone.