Apatosaurinae

Lore & Background

The first apatosaurine fossils were discovered in 1877 by Arthur Lakes and Henry C. Beckwith in Morrison, Colorado. Lakes sent specimens to Othniel Charles Marsh, who named Apatosaurus ajax in November 1877, the name derived from Greek words meaning 'deceptive lizard' because the chevron bones resembled those of some other reptiles, though not specifically mosasaurs. Marsh also named Brontosaurus excelsus in 1879 from a nearly complete skeleton found at Como Bluff, Wyoming. For decades, Brontosaurus was considered a synonym of Apatosaurus after a 1903 study by Elmer Riggs, but a 2015 paper by Emmanuel Tschopp argued they are separate genera, though some authors still consider them synonyms.

Reader's Guide

Apatosaurines are significant for their well-preserved fossils, which provide a comprehensive view of sauropod anatomy. They were nonselective low-browsers feeding on ferns, cycadoids, and horsetails, with rapid growth rates reaching adult size in about ten years. Their long, whip-like tails may have been used for defense or touch, and their robust neck vertebrae suggest possible intraspecific fighting. The subfamily is a key part of the Morrison Formation's sauropod biodiversity, which included over 16 genera, and their discovery during the Bone Wars highlights the intense rivalry between Marsh and Edward Drinker Cope. The taxonomic debate over Brontosaurus versus Apatosaurus remains unresolved, illustrating ongoing scientific revision.

Did You Know?

• The name Apatosaurinae comes from Greek words meaning 'deception lizard'.
• Apatosaurines could gain up to 5,000 kg in a single year during rapid growth.
• Brontosaurus was considered a synonym of Apatosaurus from 1903 until a 2015 study.

Taxonomy & the Brontosaurus Question

For over a century, the identity of Brontosaurus hung in the balance. In 1903, paleontologist Elmer Riggs published a study declaring Brontosaurus a mere synonym of Apatosaurus, a conclusion that dominated the field for more than a hundred years. That consensus shattered in 2015 when Emmanuel Tschopp and colleagues published a paper arguing the two were genuinely distinct genera. Under Tschopp's framework, apatosaurines comprise six valid species: three assigned to Brontosaurus and two to Apatosaurus. Yet the debate is far from settled; some authors continue to treat the names as interchangeable. The subfamily's membership beyond these two genera remains uncertain. Amphicoelias, described by Cope in 1877 from dorsal vertebrae, a femur, and a pubis collected near Cañon City, Colorado, may belong here, as might a species of Atlantosaurus. The name Apatosaurinae itself derives from the Greek apatē, meaning "deception," and saûros, meaning "lizard," echoing the etymology of Apatosaurus.

The Bone Wars Discovery

The story of apatosaurines begins in the spring of 1877, when local miner Arthur Lakes and his friend Henry C. Beckwith stumbled upon fossils in Morrison, Colorado, nestled in the eastern foothills of the Rocky Mountains. Lakes wrote to both Othniel Charles Marsh at Yale and Edward Drinker Cope in Philadelphia, and the two men raced to claim the specimens. Marsh hired Lakes; Cope's offer was turned down. The rivalry, known as the Bone Wars, meant that descriptions of new taxa were rushed and often incomplete. Marsh named Apatosaurus ajax in November 1877, based on a well-preserved partial postcranial skeleton and braincase. He chose the name "deceptive lizard" because the chevron bones resembled those of mosasaurs rather than other dinosaurs. Two years later, Marsh announced Brontosaurus excelsus, "thunder lizard," from a remarkably complete skeleton collected by William Harlow Reed at Como Bluff, Wyoming. The type specimen preserved many of the fragile cervical vertebrae, making it one of the most complete sauropod skeletons known at the time.

Anatomy & Feeding Ecology

Apatosaurines set themselves apart from their diplodocine relatives through a stockier, more robust body plan and proportionally shorter necks. Their boxy, heavily built cervical vertebrae have led researchers to hypothesize that these necks served as weapons in intraspecific combat between individuals. At the front end, their peg-like teeth were suited to a nonselective, low-browsing diet of ferns, cycadoids, and horsetails, essentially stripping vegetation close to the ground without much discrimination. Growth was astonishingly rapid: studies indicate apatosaurines reached full adult size in roughly ten years, with one study suggesting a peak annual weight gain of around 5,000 kilograms. Like their diplodocine cousins, both Apatosaurus and Brontosaurus carried long, whip-like tails. The function of these tails remains debated, but they may have served as defensive weapons or as tactile organs for touch. Several fairly complete specimens are known, providing a comprehensive picture of apatosaurine anatomy that continues to refine our understanding of these animals.

The Morrison Formation Sauropod Supermarket

Apatosaurines did not roam an empty landscape. Their Late Jurassic home, the Morrison Formation of the American West, dating between 157 and 146.8 million years ago, was a hotspot of sauropod biodiversity with over sixteen recognized genera. Apatosaurines shared their world with the long-necked Diplodocus, the towering Barosaurus, and the high-browsing Brachiosaurus. The herbivorous ornithischian community included Stegosaurus, Dryosaurus, and Nanosaurus, while the predatory niche was occupied by theropods such as Allosaurus, Marshosaurus, and Ceratosaurus. With so many large herbivores competing for the same plant resources, researchers have proposed that niche partitioning was essential. Different sauropods specialized in different feeding heights, body sizes, and dietary preferences to reduce direct competition. The robust, low-browsing apatosaurines likely occupied a distinct ecological niche, their stocky builds and shorter necks positioning them as ground-level grazers in a landscape teeming with giants.

Gallery