When was evidence of the Catopsbaatar first found?
Catopsbaatar
Catopsbaatar is a genus of multituberculate, an extinct order of rodent-like mammals. It lived in what is now Mongolia during the late Campanian age of the Late Cretaceous Period, about 72 million years ago. The first fossils were collected in the early 1970s, and the animal was named as a new species of the genus Djadochtatherium in 1974, D. catopsaloides. The specific name refers to the animal's similarity to the genus Catopsalis. The species was moved to the genus Catopsalis in 1979, and received its own genus (Catopsbaatar, Greek and Mongolian for "visible hero") in 1994. Five skulls, one molar, and one skeleton with a skull are known; the latter is the genus' most complete specimen. Catopsbaatar was a member of the family Djadochtatheriidae.
Aetosaur
A later study by paleontologists Andrew B. Heckert and Spencer G. Lucas in 1999 expanded the number of synapomorphies that diagnose Aetosauria to 18. New synapomorphies included temporal fenestrae, or holes, that opened on the side of the skull rather than the top, lateral osteoderms articulating with the paramedians, and osteoderms covering the limbs. "Aetosaurus" was still found to be the most basal member, but the phylogeny of more derived aetosaurs differed in that "Typothorax" and "Paratypothorax" were split into two different clades with their sister taxa being "Desmatosuchus" and "Longosuchus", respectively. More importantly, a new aetosaur called "Coahomasuchus" was included in the analysis. "Coahomasuchus" was found to be a basal aetosaur closely related to "Stagonolepis", and also appeared early in the fossil record of aetosaurs. Previously, basal members were only known from later times, occurring after more advanced aetosaurs.