9949 Brontosaurus
This minor planet was named after Brontosaurus, a gigantic quadruped sauropod dinosaurs, which walked on all four legs and lived in the Upper Jurassic. Adult individuals measured up to 20 meters and had a weight of up to 20 tons. Many Fossils have been found in the United States. Brontosaurus is one of the best-known dinosaurs. The official naming citation was published by the Minor Planet Center on 20 November 2002 ().
Brontornis
Possibly, the fossils described as "B. platyonyx" represent another species; they are about one-third smaller than the largest "Brontornis" bones. It is much more likely, however, that they represent sexual dimorphism. In today's hawks and owls, females are usually considerably larger than the males; this prevents overutilization of one size class of prey. It is not known whether phorusrhacid males or females would have been larger, but the fossils of the North American phorusrhacid "Titanis" also show considerable variation in size, suggesting that there was indeed at least a tendency for differently sized sexes.
Recent work has cast doubt on the hypothesis that "Brontornis" is a phorusrhacid. "Brontornis" may actually represent an anseriform, with other genera traditionally assigned to Brontornithinae ("Physornis" and "Paraphysornis") being true phorusrhacids. The subfamily containing the latter two had been proposed to be renamed to Physornithinae, with "Physornis fortis" as the type. If these conclusions are valid, this would mean that there are three groups of giant basal anseriformes, in chronological order of divergence: the gastornithids ("Gastornis" and kin), "Brontornis", and finally the mihirungs of Australia. However, other analyses have also argued that "Brontornis" exhibits thoracic vertebrae diagnostic of phorusrhacids, supporting its placement within that group.