embryonic development occurred outside the body of female dinosaurs. This discovery was made in 2005 by the Dutch amateur fossil-hunter Aart Walen at the Lourinhã Formation in Western Portugal, in fluvial overbank sediments that are considered to be from the Tithonian stage of the Jurassic Period, approximately 152 to 145 million years ago. This discovery is significant paleontologically for a number of reasons: (a) these are the most primitive dinosaur embryos known; (b) these are the only basal theropod embryos known; (c) fossilized eggs and embryos are rarely found together; (d) it represents the first evidence of a one-layered eggshell for theropod dinosaurs; and (e) it allows researchers to link a new eggshell morphology to the osteology of a particular group of theropod dinosaurs. The specimen is housed at the Museu da Lourinhã, in Portugal. As the eggs were abandoned due to unknown circumstances, it is not known if Torvosaurus provided parental care to its eggs and young or abandoned them shortly after laying. However, the eggshells are highly porous, allowing efficient gaseous exchange between the external and internal media, and thus indicative of eggs buried for incubation within the substrate, in a manner similar to modern seaturtles. This is also corroborated by the undisturbed taphonomic setting and low-energy geological context. All documented Torvosaurus specimens from the Morrison Formation are from similarly sized, likely adult individuals, and the lack of immature individuals may be explained by many factors, none of which are mutually exclusive. For one thing, the formation is known to preserve large vertebrates better than smaller ones. Immature individuals may also have occupied a different ecological niche from adults in habitats where their remains were likely to preserve as fossils, and they may have been the prey of choice of larger predators as well. Torvosaurus may also have experienced Type B1 population survivorship as has been found in other dinosaurs, with mortality increasing after sexual maturity was achieved leading to an abundance of mature individuals in the fossil record. A final possibility is that immature Torvosaurus remains could be misidentified due to having different proportions compared to the very large and robust adults. Paleoecology Provenance and occurrence The type specimen of Torvosaurus tanneri BYU 2002 was recovered in the Dry Mesa Quarry of the Brushy Basin Member of the Morrison Formation, in Montrose County, Colorado. The specimen was collected by James A. Jensen and Kenneth Stadtman in 1972