Can the True Brachiosaurus Reveal Itself?

Essential Insights

Achieving true recognition in our chaotic world is evident when astronomers decide to name a celestial object after you. On April 8, 1991, researchers at the European Southern Observatory (ESO) discovered a new asteroid orbiting between Mars and Jupiter, which they aptly named 9954 Brachiosaurus.

Brachiosaurus, a herbivorous dinosaur with an elongated neck and forelimbs, thrived in North America approximately 155 to 150 million years ago during the Late Jurassic Period.

Even today, this dinosaur remains a prominent figure in popular culture, though its fame is somewhat nuanced.

The Brachiosaurus left a lasting impression in the original "Jurassic Park" film and tugged at heartstrings in the 2018 sequel "Jurassic World: Fallen Kingdom." However, these iconic depictions were primarily modeled after another dinosaur, Giraffatitan brancai.

An Arm and a Leg

During a fossil-hunting expedition near Grand Junction, Colorado, in 1900, paleontologist Elmer Riggs and his assistant, H. William Menke, discovered an enormous yet incomplete sauropod skeleton.

Sauropods, a varied group of plant-eating dinosaurs, typically featured elongated necks, compact heads, and pillar-like legs. Many of these species reached colossal sizes, with the largest terrestrial creature ever to exist undoubtedly being a sauropod.

The skeleton uncovered by Riggs and Menke was far from complete, with only a few ribs, vertebrae, a partial hip, a fragmentary shoulder blade, and two massive limb bones remaining.

Clearly, this creature was a sauropod, but its proportions were unusual. Prior to 1900, most sauropods discovered had forelimbs noticeably shorter than their hindlimbs.

However, this specimen was the opposite. Riggs was particularly intrigued by the right humerus, or upper arm bone, which measured 6 feet (2 meters) and was marginally longer than the preserved right femur, or upper leg bone.

In a 1901 article published in the journal Science, Riggs noted that the "remarkable length of the humerus" and certain other bones "indicate an animal with shoulders towering above the pelvic area, giving it proportions akin to a giraffe."

By 1903, Riggs had christened the "new" creature Brachiosaurus altithorax. The genus name, Brachiosaurus, translates to "arm lizard," while altithorax, its species name, means "deep-chested"—a fitting and vivid description.

Brachiosaurus Versus Giraffatitan

Here’s where the story takes a turn. Between 1909 and 1913, German researchers in East Africa extracted 225 tons (or 204 metric tons) of fossils from Tanzania's Tendaguru Formation, which was part of a German colony at the time.

The centerpiece of their findings? Another colossal sauropod skeleton.

Unlike the headless Colorado specimen, this one included a (partial) skull, along with most of its ribs and vertebrae. Paleontologist Werner Janensch classified the remains as belonging to Brachiosaurus, and they were later designated as a new species: Brachiosaurus brancai.

This colossal creature from the Old World measured over 82 feet (25 meters) in length and could lift its head nearly 44 feet (13.3 meters) above the ground!

Importantly, Brachiosaurus brancai provided paleoartists with far more fossil material than North America's Brachiosaurus altithorax. The "Jurassic Park" effects team based their Brachiosaurus design on the African species, a practice followed by many artists over the years.

The situation grew more complex when Gregory S. Paul, a celebrated dinosaur artist, highlighted anatomical distinctions between Brachiosaurus altithorax and Brachiosaurus brancai in 1988. He argued that the two sauropods were so different that they shouldn’t be classified under the same genus.

A 2009 study by Michael P. Taylor from the University of Portsmouth’s Paleobiology Research Group, published in the Journal of Vertebrate Paleontology, agreed. As a result, Brachiosaurus brancai was reclassified and renamed to Giraffatitan brancai.

Hunting for Clues

Now that we’ve introduced Giraffatitan, it’s time to familiarize ourselves with the true Brachiosaurus, don’t you think?

Due to the naming controversy, Brachiosaurus altithorax — the species Elmer Riggs identified in 1903 — remains the only Brachiosaurus species officially recognized by experts today.

The tail of Brachiosaurus was both longer and taller than that of Giraffatitan. Additionally, as Taylor noted in 2009, it "bore a larger portion of its weight on its forelimbs." After all, if you have oversized arms, why not put them to good use?

There’s no question that Brachiosaurus was a massive creature. A 2017 study in the journal "Palaeontology" estimated its weight at 64 tons (58 metric tons). However, other experts believe it was lighter, possibly weighing around 44 tons (40 metric tons).

Based on the available fossils, Brachiosaurus likely measured about 80 feet (24.5 meters) in length. It may have stood 20 feet (6.2 meters) tall at the shoulder, though its head could reach far greater heights.

The precise shape of its head remains uncertain. A potential Brachiosaurus skull was discovered in central Colorado during the 1880s. However, with only a single neck bone (later destroyed) accompanying it, there’s no definitive proof it belonged to a Brachiosaurus or another sauropod entirely.

Jurassic Ecology

In addition to Brachiosaurus, numerous other long-necked dinosaurs roamed North America during the Late Jurassic Period.

Enthusiasts of prehistoric life are likely familiar with the Morrison Formation. Renowned worldwide for its abundant fossils, this geological formation consists of shales, sandstones, and limestones dating back 155 to 148 million years.

Stretching from Montana and the Dakotas down to New Mexico and Arizona, the Morrison Formation has yielded fossils of many sauropods, including Brachiosaurus altithorax.

Estimates suggest that around 30 unique sauropod species inhabited the area now known as the Morrison Formation. Among them were the whip-tailed Diplodocus carnegii, the boxy-skulled Camarasaurus lewisi, and Brontosaurus excelsus, also known as the 'Thunder Lizard.'

While it’s fascinating to imagine how these colossal creatures coexisted, it’s important to note that not all sauropods found in the Morrison Formation lived simultaneously.

The iconic Brachiosaurus, often referred to as the "arm lizard," continues to capture attention with occasional new discoveries.

In 2012, a juvenile sauropod unearthed at a Wyoming quarry was provisionally classified as a young Brachiosaurus. At just 6 feet (2 meters) long, this small specimen was a stark contrast to the colossal creature Riggs and Menke found in Colorado. As the saying goes, even the mightiest giants start small.