Fossils are the remains of animals which have died millions of years ago. They occur when animal remains are preserved under layers of earth and water over millennia. The pressure and temperature of the soil need to be just right in order for the remains to become fossilised. Fossils are normally found in the sedimentary layer of the soil, when clay, mud and rocks accumulate on the top and compress the soil in the bottom.
There are 3 types of fossils on the planet – Body fossils which include the hard parts of an animals body such as teeth, nails, scales, shells, feathers and fur; Trace fossils which are physical signs that an animal was living/present in a particular place, for example footprints, prints of nest, faeces, egg shells and tracks; Plant fossils which are fossilised remains of plants and which include seeds, flowers, leaves, roots and shoots.
The oldest fossils on Earth are approximately 3.7 billion years old. They are fossils of stromatolites– which are mounds or sheets of mud that preserve cyanobacteria – the earliest bacteria that developed on Planet Earth. Apart from the bacteria themselves, the stromatolites also contain chemical by-products produced by the bacteria too. This gives us a glimpse into how the Earth was geographically and chemically billions of years ago.
Fossil fuels aren’t made from actual fossilised dinosaurs or plants. Fossil fuels like oil, coal and natural gas were formed when microscopic algae-like creatures called diatomsdied in massive numbers and which over time were fossilised. The intense soil pressure on these fossil remains converted the carbon inside the diatom remains into fuels.
Scientists determine the age of fossils using two processes. The first is called the “carbon-14 dating” which involves studying the time it takes for the carbon present in the animals’ bodies to decay over time. The other process is called the “molecular genetic clock” which involves comparing the DNA and physiology of fossilised remains to animals that are alive today.
Sometimes, when animals and plants get trapped inside tree sap or resin, over time, they fossilise completely intact – feathers, fur, bones, teeth, bodily fluids, roots etc. – to form a product called “amber“. The fossils preserved in amber are the most significant finds for any scientist or paleontologist, since these fully-intact fossils offer researchers a look at how animals really looked like millions of years ago and whether these species have changed over time or not. Take a look at this article to see the 10 strangest things to fossilise in amber.
What happens when you roam the seas for 400 million years? Why you become a Coelacanth of course! Meet the fish that have baffled scientists with their unexpected return from the dead.
10 mind-blowing facts about the Coelacanth
They were thought to be extinct
Up until 1938, it was assumed that Coelacanths were extinct. The handful of the specimen caught by fishermen was all dead and the rest were fossils; but, in 1938, a live specimen was caught off the coast of South Africa. As of today, there are two known species of Coelacanths in the wild – one near the Comoros Islands, Africa and the other in Sulawesi, Indonesia.
Coelacanths are endangered species. Research suggests that there are just between 230 & 650 coelacanths in the wild today.
They are the key piece in the puzzle about the Earth’s first terrestrial vertebrates
Fossil records of Coelacanths show that they originated during the Devonian Period which ended 419.2 million years ago. This was the era in evolution when the first terrestrial animals made an appearance.
The Coelacanths’ physiological characteristics resemble in part those traits we observe in land-based creatures today. Scientists believe that Coelacanths may be the missing link that might point us to the exact moment in evolution when the world’s first underwater vertebrates made their foray to the land.
They have some very unique organs and some vestigialones
While Coelacanths may be the clue to the evolution of terrestrial vertebrates, they don’t have a vertebral column themselves. Instead, they have a hollow, oil-filled tube called the notochord. The notochord is the embryonic vertebral column that evolves into a full-fledged spinal cord when the embryo develops.
They are also one of the only animals today that have an intracranial joint in their skull, which allows them to unhinge their jaws from the rest of the skull and consume prey almost three times their own size.
While on the one side these fish can’t do without their notochord and intracranial joint, on the other, they canlive without their lungs. Coelacanths’ are the only known fish to have lungs and these lungs develop normally (as in vertebrates) as embryos. But as they grow older, the lungs become smaller and finally stop working, becoming completely useless. To breathe, the fish uses the scaly plates on its body as gills.
Their brains contain more fat than actual brains
Coelacanths give the term ‘small-minded’ a completely new meaning. Only 1.5% of their cranial cavity constitutes their brain matter. The rest of the cavity is made of fat. Scientists are still unsure what these fish do with the fat in their cranial cavity. But it has been observed that younger Coelacanths have larger brains and lesser fat and this proportion inverts as they age.
They are nocturnal
Coelacanths spend most of their days in cool and dark caves sleeping. They only come out at night to feed. They are drift-feeders, meaning they let the current drift them along the ocean floor. They hunt fish and cephalopods like squids, nautilus, cuttlefish and more. They aren’t very competitive when it comes to territory and food and are quite willing to share their belongings with fellow Coelacanths.
They use an electrosensory system to navigate the seas
Coelacanths possess a rostral organ in their snouts just like Anchovy which is a gel-filled cavity surrounded by a layer of adipose fat tissue. This organ is extremely sensitive to underwater electromagnetic signals and Coelacanths use this organ to navigate the seas, find prey and avoid obstacles.
The females are one-man women during the mating season
Female Coelacanths are serial monogamists and mate with just one select mate during breeding season. This mate may or may not change across the seasons and may or may not be shared between two females.
Once, the gender ratio in the world of Coelacanths was so off balance, it was noticed that the young of two females living in close quarters were sired by the same father.
They give birth to live young
Coelacanths are the only fish in the world to have live births. In 1975, researchers at the American Museum of Natural History dissected a dead specimen to find it pregnant with five embryos. The embryos resembled full-grown Coelacanths in shape and scale-texture, with just a few differences that they were smaller in size and the embryos had a small yellow film covering their bodies and a large yolk sack protruding from their pelvic fins. It’s believed that Coelacanths’ eggs hatch within the mother’s womb and the ‘pups’ are then birthed live.
They aren’t dinner-table worthy
Coelacanths are foul tasting, to say the least. Their scales secrete copious amounts of mucous and their bodies contain toxic oils, urea and wax compounds which are both inedible and harmful to the human body. So don’t be in a hurry to get one on your plate.
They are the only species of fish to have an operetta to their name
Remember the dead Coelacanth with the five embryos in her womb? Well, as it turns out, she was the muse to a musically-inclined scientist’s operetta.
Dr Charles Rand, a haematologist from Long Island produced his quirky ode to the pregnant fish in an operetta entitled Quintuplets at 50 Fathoms Can Be Fun, also called A Coelacanth’s Lament. It was set to the music of the Gilbert and Sullivan song ‘Tit Willow’ and is one of the American Museum of Natural History’s best creations.
Now that you know so much about the coelacanth, it’s time to meet one in person.