Brachiosaurus stands as one of the most recognizable long-necked dinosaurs, an herbivore from the Late Jurassic Period. Its towering stature, characterized by forelegs longer than its hindlegs, gave it a giraffe-like appearance and a unique body plan.
The Groundbreaking North American Discovery
The discovery of Brachiosaurus occurred in western North America. The first partial skeleton of Brachiosaurus altithorax, the type species, was unearthed in 1900 near Grand Junction, Colorado, USA. Elmer S. Riggs and his team from the Field Columbian Museum made this find. The site is located within the Morrison Formation.
Riggs named the dinosaur Brachiosaurus altithorax in 1903. The name translates to “arm lizard with a deep chest,” referencing its long forelimbs and tall torso. This original specimen, though incomplete, established it as a distinct sauropod. Additional Brachiosaurus remains have since been found in other North American locations within the Morrison Formation, including Utah, Wyoming, and Oklahoma.
The African Relative and Its Discovery Site
A common source of confusion regarding Brachiosaurus stems from the discovery of a closely related but distinct dinosaur in East Africa. Large brachiosaurid fossils were discovered in the Tendaguru Formation in Tanzania during major German expeditions between 1909 and 1912. These expeditions, led by paleontologists like Werner Janensch, recovered extensive material, including several partial skeletons and skulls.
Initially, these African specimens were classified as a species of Brachiosaurus, specifically Brachiosaurus brancai. For many decades, the more complete African fossils served as the primary model for reconstructions of Brachiosaurus, including the famous mounted skeleton in Berlin. However, further scientific analysis revealed significant anatomical differences between the North American Brachiosaurus altithorax and the African specimens. Consequently, in 1988, these African dinosaurs were reclassified into their own distinct genus, Giraffatitan, meaning “titanic giraffe,” with the species now known as Giraffatitan brancai. While closely related, Giraffatitan is now recognized as a separate lineage from the North American Brachiosaurus.
Unearthing Ancient Habitats
The fossil sites where Brachiosaurus and Giraffatitan were discovered offer insights into their ancient environments. The Morrison Formation in North America, where Brachiosaurus altithorax was found, dates to the Late Jurassic Period, approximately 157 to 150 million years ago. This vast geological formation spans much of the western United States and represents an ancient landscape dominated by meandering rivers, extensive floodplains, and seasonal lakes. The presence of ferns, cycads, and conifers indicates a lush, forested environment along these river systems, providing abundant vegetation for large herbivores.
Similarly, the Tendaguru Formation in southeastern Tanzania, the source of Giraffatitan fossils, also dates to the Late Jurassic, around 157 to 145 million years ago. This formation preserves evidence of a coastal plain environment, characterized by tidal flats, lagoons, and vegetated inland areas. The sedimentary rocks show shifts between shallow marine and tidal flat conditions, suggesting a dynamic environment influenced by sea-level changes. Both formations offer a glimpse into the diverse, well-vegetated ecosystems that supported these colossal long-necked dinosaurs.