User:Abyssal/Pooleyichnus

Pooleyichnus

In 1886, a man named C. Pooley discovered a fossil footprint near Burford, England. The specimen was a well-preserved impression left by some small five-toed animal in a piece of rock from the Stonesfield Slate. While the Stonesfield Slate is not actually slate in the strictest sense, it is a stratigraphic unit composed of sedimentary rocks that were laid down during the Middle Jurassic epoch. In addition to the Pooley track, its sediments preserve ancient dinosaurs, mammals, and pterosaurs. In 1975, nearly a century after the track was initially discovered, ichnologist Bill Sarjeant formally described Pooley's track as a new ichnospecies, Pooleyichnus burfordensis. Sarjeant was puzzled trying to identify what kind of animal could have made the track. The only footprints then known from the Jurassic period small enough to be in the size range of Pooleyichnus were some Middle Jurassic carnivorous dinosaur footprints and some Late Jurassic pterosaur tracks, both from North America. Sarjeant guessed that Pooleyichnus may have been left by a mammal, or mammal-relative, since mammal fossils are among those preserved in the Stonesfield Slate. However, authors Lockley and Meyer have noted that the Stonesfield also shares traits that might be expected from the track of a large lizard or pterosaur. They also note that if Sarjeant's identification was correct, Pooleyichnus would be one of the largest Mesozoic mammal tracks ever discovered. The vast majority of Mesozoic mammal footprints are only a centimeter or two long.

http://www.nmnaturalhistory.org/assets/files/Curators/Lucas/Lucas2009_JurassicTetrapodBiochron.pdf