text: The oldest fossil of the eutherian clade of mammals is a Chinese shrew that has been dated to this period.
full_question: The oldest fossil of the eutherian clade of mammals is a Chinese shrew that has been dated to this period. The Aurornis genus lived during this period. The Sundance Sea existed as an extension of the Arctic Ocean during this period, and sediments along its shores gradually created the fossil-rich Morrison Formation. The Archaeopteryx genus, which is sometimes considered the first bird, lived during this period, in which Allosaurus sometimes preyed upon Stegosaurus. For 10 points, name this period that followed the Carboniferous and preceded the Triassic.
first_sentence: The oldest fossil of the eutherian clade of mammals is a Chinese shrew that has been dated to this period.