Macronaria

Macronaria is a major clade of sauropod dinosaurs within the group Sauropoda, one of the two principal lineages of Neosauropoda alongside Diplodocoidea. The clade is defined as the most recent common ancestor of Camarasaurus lentus and Brachiosaurus altithorax and all its descendants. The name macronaria is associated with the relatively large external nares (nostril openings) found in many members of this lineage, a feature that historically helped distinguish the group.

The Macronaria include some of the best-known and largest sauropods, notably the brachiosaurids (such as Brachiosaurus and Giraffatitan) and the camarasaurids (such as Camarasaurus). It also encompasses the Titanosauriformes, a diverse lineage that gave rise to the titanosaurs and related forms. This broad assemblage spans a wide range of morphologies and ecological roles, from medium to extremely large herbivores with long necks and tails.

Fossil evidence for Macronaria is widespread, with records dating from the Early Jurassic to the Late Cretaceous. Their remains are found on multiple continents, reflecting a broad geographic distribution that included both Laurasian and Gondwanan landmasses. Titanosauriforms, in particular, became globally widespread in the Late Cretaceous, and titanosaurs dominated sauropod faunas in many regions before the end of the era.

In contemporary classifications, the precise internal relationships of Macronaria have varied as new phylogenetic analyses have emerged. Nonetheless, the clade is generally recognized as a key branch of Sauropoda that includes some of the most iconic and ecologically successful long-necked dinosaurs in the fossil record.