Fossils are the key to unlocking Earth’s most fascinating secrets. These prehistoric remnants open a window to the past, giving us a glimpse into an ancient world and its inhabitants. When talking about fossils, most people think of the big dinosaur bones they have seen at the museums. However, fossils come in all forms, shapes, and sizes. They can be a footprint, an insect perfectly preserved in amber, or a leaf imprint on sediment. Each one plays a critical role in uncovering our planet’s evolutionary history. Here, we will take a look at some of the most fascinating fossils that paleontologists have ever discovered.

1 This exquisitely preserved fossil of a nodosaur is roughly 110 million years old. The first of its kind, the fossil shows an armored plant-eater that roamed the Earth up until the late Cretaceous period.

Back in 2011, a Canadian mine worker accidentally uncovered the fossilized remains of a Borealopelta nodosaur, an armored, herbivorous dinosaur belonging to the ankylosaurian family. The 3,000-pound, 18-foot-long behemoth existed sometime between the Late Jurassic and Late Cretaceous periods.

Though the fossil was found in Alberta, this species of dinosaur was common throughout today’s Antarctica, Africa, Asia, Europe, and North America. In fact, scientists consider it as one of the best and most perfectly-preserved dinosaur specimens ever discovered. Its skull still bears tile-like plates and a gray patina of fossilized skins.

Its sheer size aside, the most distinct feature of the nodosaur is its armor. The bony mosaic covers its back and neck, and gray circles contour the individual scales. What looks like a flawlessly chiseled sculpture is the petrified version of an actual dinosaur. From the fossilized skin on the creature’s skull to the scales on the sole, every minute detail makes the fossil unique and incredible.

Scientists have hypothesized that the dinosaur must have been swept up by a flood, and its dead body then ended up in a river. The belly-up, bloated carcass then floated downriver until it reached the seaway. After staying afloat for a week or more, the carcass must have exploded, leaving it to drop down to the seabed. As its back sank deeper into the muddy floor of the ocean, minerals started infiltrating its skin and armor. For millions of years, rocks kept piling on top of it ensuring that the nodosaur’s shape and form remain intact.

The fossil now rests at the Royal Tyrrell Museum where experts have spent over six years and 7,000 hours painstakingly chipping away at the surrounding rocks to fully extricate this gem. (1, 2)

2 The fossilized skeletons of the prehistoric whale were found in the Egyptian Sahara. Known as the “Valley of the Whales,” this section of the desert is a 50-million-year-old treasure chest of fossilized marine life.

The Egyptian Sahara is among the driest sections of the world, and it receives only a few inches of rainfall every year. It’s the last place where you would expect to find the fossilized remains of an aquatic mammal, but that is precisely what has happened. Some 50 million years back during the Mesozoic Era, this part of the world was covered by the ancient Tethys Sea. Naturally, it housed a thriving ecosystem of all kinds of marine life. However, in the Cretaceous Period, the continent broke apart and created the Atlantic and Indian oceans leaving the Tethys Ocean dry and barren.

The now-exposed ocean bed is a treasure trove of ancient fossils. In 1902, paleontologists first discovered what is now named as the “Valley of the Whales” or “Wadi al-Hitan.” Among the most notable findings were the fossilized bones of a 65-feet-long, 37-million-year-old ancient whale. A distant ancestor of today’s whales, this particular species, known as the Archaeoceti, is now extinct. These ancient whales are the oldest forms of the species ever found. These cetaceans were once land-based creatures that walked on legs. Evolution drove them underwater, but some dolphin and whale species still have phantom hip bones that once attached legs.

Some of the whale skeletons found in the Egyptian desert still have legs with toes! They tell us a story of the whale’s evolutionary past when it was still trying to adjust to life in the ocean. Even though the bones were discovered over a century ago, the authorities did not turn Wadi al-Hitan into a conservation area until the 1980s. Now, the iconic location has been turned into a museum where all the fossils from the area are kept. (1, 2)

3 “Big Mama Brooding” is the name given to this 75-million-year-old fossil that depicts an oviraptorid dinosaur protecting its eggs to its last breath.

Who knew the most vicious predators of ancient Earth also had a softer side? However, that is exactly what the “Big Mamma Brooding” fossil tells us. Unearthed back in 1994 in the Mongolian Gobi Desert, the dinosaur fossil is said to be anywhere between 66 and 83 million years old. It shows a female Citipati warming her eggs just as birds do today. It is an oviraptorid theropod species of dinosaur that existed towards the end of the Cretaceous Period in today’s Mongolia.

When the first oviraptor was found in Mongolia all the way back in 1922, experts named it as “egg thief” because the fossil was discovered near a nest that appeared to have Protoceratops eggs. However, in 1993, an American paleontologist named Mark Norell discovered the fossilized remains of an embryo in a similar egg. He soon realized that it was an oviraptor and that the “egg thief” may have actually been a parent.

The following year, with a sheer stroke of luck, Norrel and his team came upon the “Big Mamma.” The fossilized dinosaur was missing its skull, but the rest of the body was intact. Under its skeletal remnants was an egg nest. The dinosaur is thought to have been incubating her eggs when disaster struck in the form of a mudslide or a sandstorm. This fossil shows just how protective this species of dinosaurs were. (1, 2)