The earliest evidence of dinosaurs Lineage
The earliest evidence of the lineage of dinosaurs on which it is reported, namely a set of fossilized footprints in Poland, has been the subject of a meticulous analysis, whose results have just been submitted.
One or two million years after the mass extinction of the Permian-Triassic, and was a member of that lineage. A specimen of this species, characterized inter alia by a body size less than a domestic cat, walked a fine clay ground in what is now Poland. This set of fossilized footprints shows that the closest relatives of dinosaurs existed between 5 and 9 million years earlier than suggested by the oldest fossilized skeletons discussed above.
The closest cousins of the dinosaurs arose immediately after the worst mass extinction. The greatest crisis in the history of life has also created a major opportunity for evolution, the empty stage and allow the entry of new actors on stage, the dinosaurs, such as Stephen Brusatte, Division of Paleontology of American Museum of Natural History.
The research team analyzed three sets of footprints, each in a different place in a mountainous area of central Poland. These three sources of trace fossils are windows on three distinct ecosystems, because they correspond to different times. The set of prints from Stryczowice is the oldest, 250 million years old. That of Baranow is the latest, with 246 million years, while the intermediate has an antiquity Wiory.
Because tracks are only an impression in the mud left by a small part of the body, identification of animals that produced them is often difficult. Fortunately, the dinosaurs have a very distinctive gait, especially when compared with that of their relatives diapsidos (the evolutionary group that includes birds, reptiles and some extinct lineages) such as crocodiles and lizards. While alligators and crocodiles walk with their legs wide apart from each other, dinosaurs walked keeping their feet closer.
The tracks in the three sites show that Poles gait and other indisputable characteristics of dinosaurs, including three prominent middle fingers on the legs and two children outside a parallel alignment of these three fingers, and other telltale traits.
Because all of these features are seen in the footsteps of the oldest site, Brusatte and his colleagues have concluded that traces of Stryczowice, only a few centimeters in length, are the oldest evidence of the lineage of the dinosaurs.