In 1922, he named Machaeroprosopus andersoni, on the basis of the holotype FMNH UC 396, partial skull. It was probably collected from the Bull Canyon Formation of the Chinle Group or Dockum Group, probably at the Bull Canyon, in the Guadalupe County of New Mexico. This taxon was considered to be a junior synonym of M. buceros by Long and Murry and later authors, although Stocker and Butler treated M. andersoni as a valid species. The holotype is the only known specimen of this species, although there are other specimens from the Bull Canyon Formation that were referred to Arribasuchus buceros by Long and Murry, but not by Stocker and Butler. In 1929, he and Edward Branson described the Metoposauridae Koskinonodon. In 1930, he described Amphekepubis, a genus of mosasaur from the Late Cretaceous of Mexico. Their remains correspond to the holotype specimen UM VP 509, a partial skeleton preserved in three dimensions, comprising the pelvic area, hind limb bones and nine caudal vertebrae, found in the east of Monterrey, in the state of Nuevo Leon, which come frommarine sediments apparently from the San Felipe Formation, which corresponds to the boundary between the ages of Coniacian and Santonian in the early Late Cretaceous. However, it has been suggested that age may be more recent and its remains even might belong to the genus Mosasaurus. In 1931, he erected the new ichnogenus Ignotornis for some bird tracks preserved in the Dakota Group near Golden, Colorado. These were the first scientifically documented Mesozoic bird footprints. The bird in question as interpreted as a "small shorebird or wader". The site would eventually be heavily collected and all of its tracks were presumed removed. In 1932, he and Branson reported the presence of Carboniferous-aged fossil footprints of a new ichnospecies in the Tensleep Formation of Wyoming. They named the tracks Steganoposaurus belli and attributed them to an amphibian nearly three feet in length. Also with Edward Branson, he named a new kind of Late Triassicdinosaur footprint discovered in the Popo Agie Formation of western Wyoming. The new ichnogenus and species was named Agialopus wyomingensis. In 1933, he and Branson described the conodont Wurmiella excavata. In 1934, with Branson, he described the conodont generaPseudopolygnathus and Ancyrognathus. In 1936, he described the new ankylosaur species Nodosaurus coleii. In 1938, he and Branson reviewed the conodont genus Icriodus. In 1941, with Branson, he described the conodont genera Bactrognathus, Doliognathus, Scaliognathus and Staurognathus. In 1944, he described with Branson the conodont genus Siphonodella.
