Just in time for Easter this year, a fossil discovery in Spain provided exciting new data about the similarities between dinosaur eggs from prehistoric times and modern-day bird eggs. Nieves Lopez-Martinez from the Universidad Complutense de Madrid and Enric Vicens from the Universidad Autonoma de Barcelona were surprised to discover an exquisitely preserved fossil egg in an upper Cretaceous sandstone dig in the Spanish Pyrenees. The egg, dating back 70 million years ago, is approximately 2.75 inches long and, according to the two paleontologists, probably belonged to a small carnivorous dinosaur. Because the dinosaur itself was not fossilized, the eggs have been named (technically an “oogenus” and “oospecies”) Sankofa pyrenaica, literally “learning from the past in the Pyrenees.” Not only is the egg an unusual find in that it is were well-preserved and whole; it also shows the close similarities between modern bird eggs and dinosaur eggs. The dino egg doesn’t have the third external layer of shell that modern bird eggs all display (in good enough condition to visualize using scanning electron microscopy), however, its shape and size are uncannily similar to a hen’s egg. Most dinosaur eggs are equally rounded on both ends, but the Sankofa egg, like that of a chicken, is narrower or tapered at one end, producing a teardrop shape. Using a morphospace analysis technique developed to study modern eggs, the Sankofa egg plotted squarely in the middle between other carnivorous dinosaur eggs and modern bird eggs. Paleontologists say that this represents another important step along the ever-stronger-evidenced evolutionary path from dinosaurs to birds.
Light and scanning electron micrographs of the Sankofa eggshell (Nieves Lopez-Martinez/Enric Vicens/Paleontology).
The oldest-known dinosaur eggs are from the Lower Jurassic (190 million years ago) of South Africa.
Read more about the Sankofa egg at Wired.com.
Find the published study in the March 2012 online issue of the journal Paleontology.