Europasaurus

Description

Europasaurus, meaning 'Europe lizard', was a type of early sauropod. These were large, four-legged herbivorous dinosaurs. It lived during the Late Jurassic period, around 154 to 151 million years ago, in what is now northern Germany.

Island Life

This dinosaur is special because it shows a phenomenon called insular dwarfism. This means that the Europasaurus lived on an island in the Lower Saxony basin. Because they were isolated, they grew to be smaller than related dinosaurs elsewhere. Europasaurus is a good example of how animals can change size when they live far away from others of their kind.

Discovery and naming

In 1998, a fossil collector found a tooth from a large plant-eating dinosaur at Langenberg Mountain in Germany. This was the first time scientists found dinosaur bones from the Jurassic period in northern Germany.

More bones were found later, and scientists dug up the area. They found many dinosaur bones stored in rocks. Some rocks had to be broken apart to find the bones inside. By 2001, they had prepared 200 bones, and by 2002, they found the first partial dinosaur skull ever discovered in Europe. A fire in 2003 damaged some of the fossils before they could be studied.

In 2006, scientists named the dinosaur Europasaurus holgeri. They named it after Europe and the man who found the first tooth. The bones were small, so they first thought they were from baby dinosaurs. But later, they learned these were adult dinosaurs that had grown small because they lived on an island with limited food. Scientists have found over 650 bones from at least 20 different individuals.

Description

Europasaurus is a very small sauropod. It measured only 5.7–6.2 m (19–20 ft) long and weighed between 750–2,100 kilograms (1,650–4,630 lb) as an adult. This size was estimated from a partial leg bone, compared to a nearly complete Camarasaurus specimen. Younger individuals ranged from 3.7 m (12 ft) to the smallest juvenile at 1.75 m (5.7 ft).

Europasaurus was a type of small neosauropod. It had several special features that made it different from its close relatives. Compared to Camarasaurus, Europasaurus had a different shape on the top of its head, a shorter connection between certain bones in its skull, a different shape on the back of its head, and its back bones were not split in a certain area.

Most of the bones on the outside of Europasaurus's head have been found, except for a few small bones. One bone in particular, called a maxilla, has a long body with two extended parts.

The neck bones of Europasaurus are the best preserved and most common among its fossils. However, we do not know the whole neck, so the number of neck bones could be between Camarasaurus (12 bones) and Rapetosaurus (17 bones). The neck bones of adult Europasaurus are stretched out and shaped like a ball on the front end, with a notch on the top of the back end.

Fossilized skin impressions, which show what the skin looked like, are only known from a few other dinosaurs besides Europasaurus. The skin types of one of these dinosaurs, Tehuelchesaurus, looks more like that of some other dinosaurs than it does to the young of another dinosaur group called titanosaur embryos from Auca Mahuevo.

Classification

When scientists found Europasaurus, they thought it was a special dinosaur not part of groups called Brachiosauridae or Titanosauromorpha. This meant its small size might be from evolution. Many studies showed that Europasaurus was more advanced than another dinosaur called Camarasaurus. Later studies put Europasaurus close to a group called titanosaurs.

Some scientists thought Europasaurus might belong to the Brachiosauridae group. But it did not have all the needed bones to be sure. Recent studies still place Europasaurus among the brachiosaurids, but scientists are still learning more about its exact position.

Paleobiology

Growth

Scientists studied the bones of Europasaurus and found that it was a small dinosaur on purpose, not just a baby. They looked at many fossils and saw that even the biggest ones were smaller than other similar dinosaurs. This shows that Europasaurus grew slower and stayed small.

Dwarfism

Europasaurus might have become small because its ancestors lived on an island that was too tiny to support big dinosaurs. This is called island dwarfism. Other small dinosaurs lived on islands too, but Europasaurus is special because it shows a big, fast change in size compared to its relatives.

Palaeoecology

The Langenberg locality in Germany shows what life was like on an island during the late Jurassic period. At that time, this area was mostly underwater, but many animals and plants from nearby islands were washed into the area. We can see fossils of sea creatures like clams and fish, but most of the animals and plants found there lived on land.

Scientists have found many dinosaur bones at Langenberg, including over 450 bones from Europasaurus. Besides Europasaurus, fossils from other dinosaurs like stegosaurs and different types of meat-eating dinosaurs have also been found there.

Extinction

Fossil footprints found above the Europasaurus bones suggest a reason why Europasaurus and other small dinosaurs on the island might have gone extinct. These footprints are from much larger meat-eating dinosaurs that arrived on the island after sea levels dropped. The new, larger dinosaurs may have outcompeted the smaller ones for food and space, leading to the end of Europasaurus and other small dinosaur species on the island.