The oldest fossil embryos were discovered among approximately 100 dinosaur eggs recently found in the area around Lourinha, a small town about 37 miles (60 kilometers) north of Lisbon, Portugal. The embryos—identified as those of theropods—were dated at approximately 140 million years old. They are the oldest embryos to date, and the only ones currently known from the Jurassic period. Until this finding, all other fossilized dinosaur embryos came from the Cretaceous period, with the oldest being approximately 80 million years old.