Theropod Eggshells Discovered in Portugal
The Nests of Jurassic Hunters
The Lourinhã Formation of western Portugal has provided researchers from the New University of Lisbon (Universidade Nova de Lisboa), with not one but two sets of dinosaur eggs to study. Palaeontologists from the University state that the fossilised remains of dinosaur eggs from two locations in the Lourinhã Formation come from two different meat-eating dinosaurs. The crushed and broken nests represent dinosaur remains estimated to be approximately 150 million years old.
Although no evidence of fossilised embryos could be found, the scientists were able to study the size, morphology and texture of the eggs and from this evidence, candidates as to what dinosaurs might have laid these eggs can be proposed. Much of the preliminary work to identify the fossil material was made by University palaeontologist Vasco Riberio, during the Late Jurassic this part of Portugal was a floodplain inhabited by many different types of dinosaur.
The first set of eggs, spherical in shape and approximately 15 centimetres in diameter were very probably laid by a large theropod. It has been suggested, that based on the size of the eggs, their mother was a Torvosaurus. Torvosaurus is a little known Late Jurassic carnivorous dinosaur. It might be a member of the allosaurid family, or perhaps, because of its heavy and robust frame it might be a megalosaur. Fossils are known from Portugal and the Morrison Formation of the western United States. At an estimated length of more than ten metres, it is one of the largest carnivorous dinosaurs known from Portugal.
The eggs found at the second location are slightly smaller and more elongated in shape, it has been speculated that this batch of legs was laid by a Lourinhanosaurus (L. antunesi). Lourinhanosaurus is known from a single partial skeleton and other fragmentary bones including a femur (thigh bone) all found in the Lourinhã Formation on the western coast of Portugal. Previously, a number of fossilised eggs found in the Lourinhã Formation have been ascribed to this species, which is estimated to have grown to lengths of five metres.
An Illustration of the Dinosaur Lourinhanosaurus antunesi
Picture credit: Everything Dinosaur
Abandoned Nest Sites
The scientists are not sure why these two nest sites seem to have been abandoned. It has been suggested that something may have happened to the adults or that the abandonment of eggs once laid was normal behaviour for these types of theropods. Such behaviour, laying eggs and then leaving them to their fate is referred to as precocial behaviour. A number of reptiles lay eggs and then abandon them, reptiles such as tortoises and turtles. Precocial behaviour is also seen in the Aves, with many types of ducks and geese when hatched, are relatively well-developed and can feed themselves.
The dinosaurs that laid these eggs may have simply abandoned the nests, the dinosaurs that hatched would have been mobile almost immediately and would have left the nest shortly after hatching to fend for themselves.
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