Cretaceous sea and sea monsters

Nowadays, it's calm and peaceful in Tykarp and Ignaberga. It was different 80 million years ago...

The inhabitants of the Cretaceous sea.

Once upon a time, long ago...

Imagine traveling 80 million years back in time; you now find yourself in the Cretaceous period! Tykarp and Ignaberga were covered by a warm shallow sea, with many small islands scattered throughout. These islands were inhabited by small dinosaurs, while the sea teemed with oysters, crabs, turtles, octopuses, and sharks. Here, sea monsters clashed, such as dragon-like mosasaurs and long-necked plesiosaurs!

Even today, we can see remnants of this ancient sea and its inhabitants, although it looks a bit different now. What was once inhabited by animals and plants is now a limestone ridge stretching from Ignaberga and Tykarp to Kristianstad and beyond Bromölla; this area is known as the Kristianstad Cretaceous basin. The limestone is rich in fossils, and with luck and patience, you can find fossils of octopuses and even shark teeth!

In fact, all the limestone from the Kristianstad area contains staggering amounts of fossils! Scientists have discovered remains of apex predators like sharks, mosasaurs, and plesiosaurs, as well as fossils from many other creatures. It seems that this area, with its islands, bays, and lagoons, served as a nursery for these predators. The waters were relatively calm, providing an abundance of food for the large sea creatures. In these tranquil waters, offspring were born, allowing them to grow and learn to hunt before venturing into more dangerous waters.

Fossils and limestone are incredibly exciting, and the stone is also very useful. Here in Tykarp and Ignaberga, there is a long tradition of limestone quarrying, dating back to the 12th century and continuing to this day. In the past, limestone was used for mortar in construction. Today, limestone is mined in open-pit quarries and used in agriculture and iron production. Calcium carbonate, derived from limestone, is also found in many everyday items, such as toothpaste, glass, and toilet paper.

So when you visit Tykarpsgrottan, you're actually visiting the Cretaceous sea! Everywhere - on the ceiling, walls, floor, and pillars - you'll find limestone filled with fossils of the animals and plants that lived in the sea 80 million years ago. It doesn't get much cooler than that!

Kristianstad Cretaceous basin. The checkered area shows the remains of the Cretaceous sea preserved as limestone.
Mosasaurs - the kings of the sea.

Mosasaurs - the kings of the sea!

Mosasaurs, or sea dragons, were marine reptiles that lived during the Cretaceous period about 80 million years ago. They are preserved as fossils where bones and teeth have been found around the world, including in the limestone layers in Skåne (Bromölla and Tykarp/Ignaberga). In Holland and the USA, researchers have even found complete skeletons!

Bones that scientists have found indicate that mosasaurs evolved from land-dwelling to marine creatures. Around 100 million years ago, they were 1-2-meter-long lizards that hunted in the sea and laid eggs on land. Over the next millions of years, they evolved into large predators that ruled the seas, giving birth to live young in the water instead of laying eggs on land.

Mosasaurs could get big! The largest known species is called Mosasaurus Hoffmani. It could grow up to 15 meters long, about the length of a large bus! Like other mosasaurs, Mosasaurus Hoffmani had a powerful weapon: its jaws! Their jaws could reach up to 150 cm in length and were filled with 6-8 cm long teeth that gripped onto their prey. They didn't have particularly sharp teeth and couldn't tear or shred their prey like sharks do. However, with the help of their powerful and hinged lower jaw, they could pull their prey down their throat and swallow it whole without chewing it!

When researchers have found fossils of mosasaurs, they have sometimes found fossilized food remnants in their stomachs but also fossilized feces. The contents of their stomachs and feces indicate that they enjoyed eating sea turtles, octopuses, sharks, fish, swimming birds, pterosaurs, and even other mosasaurs.

They were also quite adept swimmers, using their long and powerful tails to propel themselves through the water. This swimming style allowed them to swim and accelerate rapidly, but they probably couldn't sustain top speed for long distances. In addition to their tails, they also had fins that helped them steer through the water.

Researchers have not found mosasaur bones in layers younger than the Cretaceous period. They went extinct about 65 million years ago when a meteor struck the Earth. The aftermath was so violent that half of all animal species on Earth died out, including mosasaurs and dinosaurs.

Mosasaur tooth. Foto Filip Lindgren.

Plesiosaurier - the swan lizards! 

Besides mosasaurs, there was another large group of marine reptiles in the Cretaceous sea: plesiosaurs, sometimes called swan-necked lizards. Like mosasaurs, plesiosaurs constituted the top of the food chain in the Cretaceous sea. The imaginative name "swan lizard" comes from the animal's long neck. Scientists previously believed that its neck was flexible and mobile like that of swans, perfect for catching fish and other prey. The oldest findings of plesiosaur fossils date back to the end of the Triassic, about 200 million years ago. They became extinct, like many other species, at the end of

the Cretaceous period 65 million years ago.

Plesiosaurs are divided into two groups, long-necked and short-necked. In the Kristianstad chalk basin,

researchers have found fossils of both groups: the long-necked Scanisaurus and the short-necked Polycotylidae.

The 4–5-meter long Scanisaurus, or Scania lizard, has so far only been found in the Kristianstad area. It

likely hunted in open waters and on the ocean floor, where small fish and even belemnites were on the menu. The most distinctive feature of the long-necked plesiosaurs was their long necks, which could make up more than half of their entire body length. Unlike previously thought, researchers now believe that their necks were stiff, and together with the small triangular-shaped skull with even and sharp teeth, Scanisaurus had a streamlined body silhouette, perfect for movement and hunting in the ocean!

The short-necked Polycotylidae looked somewhat different. Their necks were significantly shorter, and

they had a larger head compared to the long-necked plesiosaurs. They were excellent swimmers, and this, combined with their size, made them formidable predators. A common feature of both long-necked and short-necked plesiosaurs was that they gave birth to live young and lacked gills, breathing through lungs. Therefore, they had to surface to breathe before diving into the sea in search of food. They also had two pairs of fins and swam by flapping one pair while the other was pushed upward by the currents in the water.

Fossils of plesiosaurs have been found in Ignaberga and Bromölla.

Halskota från en plesiosaurie. Foto Filip Lindgren.

Belemnites in abundance!

Belemnites are predators and belong to a group of animals called mollusks, which also include clams and snails. Octopuses are a very ancient animal, the first appearing almost 500 million years ago. There are three groups of octopuses that can be found as fossils:

  • Nautiloids (still exist today)
  • Ammonites (extinct)
  • Belemnites (extinct)
The first octopuses were the kings of the sea! Sharks and larger fish did not yet exist, so octopuses had no direct enemies. They could grow several meters long and floated in the sea with the help of their gas-filled shells. Using their keen eyesight, they hunted for food on the ocean floor. Scientists are not entirely sure what the earliest octopuses fed on, but it is believed they hunted smaller crustaceans and octopuses. Around 420 to 360 million years ago, the first primitive sharks and armored fish appeared, making life more dangerous for octopuses, and their heyday was over.

Around 200 million years ago, ammonites and belemnites appeared in the oceans. Ammonites had outer shells that were often spiral-shaped and very fragile, so they are rarely found in the limestone here in Tykarp, Ignaberga, and Bromölla. Fossils of belemnites, on the other hand, are more commonly found. Belemnites had a shell inside the rear part of their bodies. This internal shell helped the octopus maintain balance in the water.

Fossils of belemnites are sometimes called "devil's fingers" and resemble cigar-shaped rods. They are used as index fossils, which means they can be used to determine the age of the rock in which the fossil was found. Through fossil discoveries, scientists estimate that belemnites could grow up to 3 meters long.

Fossil of the belemnite squid. A common fossil in the area, also known as fairy lights. Foto FIlip Lindgren.