The Giant's Little Brother
For a long time, the small dinosaur skeletons discovered in the Oker in Lower Saxony since 1998 were thought to be the young of the giant sauropods. But bone examinations now paint a different picture: the dinosaurs were dwarfs - trapped on an island that formed giants into midgets.
When hobby archaeologist Holger Lüdtke came across the fossil remains of a sauropod in the Langenberg quarry near Oker on the northern edge of the Harz Mountains in 1998, that alone was a minor sensation. Because dinosaur finds are rare in Germany. During the Jurassic period 140 to 200 million years ago, when the giant lizards conquered the prehistoric world, almost everything in our latitudes was under water.
Only a few regions rose above sea level at that time. The area around Oker near Goslar was one of them - and therefore soon became one of the most productive excavation sites in Germany. An international team of paleontologists has now recovered and prepared almost a thousand dinosaur fossils there, including the remains of more than ten different sauropod specimens.
The sauropod group includes the largest species of dinosaurs that have ever lived. Sauroposeidon proteles, for example, which probably owes its name to the frightening thunder of its heavy steps, measured a good 30 meters from the head to the long neck to the tail, which served as a counterweight. The brachiosaurs, whose backbone formed a 25 meter long slide thanks to their rather upright neck position compared to their conspecifics, were also among the giants among the lizards.
However, the fossils that paleontologist Martin Sander and his colleagues found in the Harz Mountains were much smaller than usual: The largest sauropod specimen that they reconstructed from the remains measured just six meters, the smallest was with 1.70 meters no taller than most of today's Europeans - even the femur of some sauropod species could exceed this size. So had the researchers encountered a group of young animals? Everything pointed to it.
But then Martin Sander examined the bones of the supposed teenagers for so-called growth marks, which, like the annual rings on trees, allow conclusions to be drawn about the growth of the animals: If these are far apart, this indicates that the lizard is still growing was in growth. However, if the outermost rings are close together, the animal was probably adult. The smaller of the Harz dinosaurs all had markers that were far apart from each other - so they are really still young animals. The largest, however, had a small number of closely spaced rings - it was young but already fully grown. The researchers had encountered Lilliputian sauropods.
To further complicate the mystery of the Oker dinosaurs, phylogenetic studies of the skeletons also revealed a close relationship with the camarasaurs, which also includes the brachiosaurs. An unusual family: Parents and siblings are towering giants - and next to them a comparatively tiny little brother.
The Europasaurus holgeri, now named after its discoverer Holger Lüdtke, probably owes its unusual body size to the constantly rising water level in the Jura. The remaining islands in the north-west German basin provided little food. Smaller animals that got by with less food probably had better chances of survival, explains Nils Knötschke from the Dinosaur Open-Air Museum in Münchehagen, who led the excavations in the Harz quarry and also prepared more than 80 percent of the fossils found. If the food supply is limited, such a decrease in size can occur extremely quickly, confirms Martin Sander. Sometimes ten to twenty generations were enough.
The best example of this was provided by the English, who once released deer on the Shetland Islands, which developed into dwarf forms in a very short time. The meanwhile extinct dwarf elephants, which with their body size of only 90 centimeters fell victim to the appetite of the Indonesian Komodo dragons and other unpleasant environmental conditions, are said to have developed due to such island isolation. However, it remains controversial as to whether the "hobbit" Homo floresiensis also arose through similar evolutionary conditions.
In any case, the dwarf dino went the exact opposite way of its relatives with its insular-related shrinkage: While it got smaller, its cousins developed into true giants. What evolution once separated, research has now reunited into a large family reunion: From the skull of one of the lizards found, the paleontologist Thomas Laven reconstructed the appearance of the midgets, which can now be admired as lifelike models in the Dinopark Münchehagen.