Will the Real Brachiosaurus Please Stand Up?

On a fossil-finding trip around Grand Junction, Colorado, in the year 1900, paleontologist Elmer Riggs and his assistant, H. William Menke,came acrossa very large — and very incomplete — sauropod skeleton.

Sauropods were a diverse group of herbivorous dinosaurs. Generally, they had long necks, small heads and column-like legs. Many species were flat-out enormous. Indeed, thebiggest land animalto ever draw breath was undoubtedly a sauropod.

TheskeletonRiggs and Menke unearthed was missing several pieces. All that remained were some ribs and vertebrae, a partial hip and an incomplete shoulder blade. There were also two gigantic limb bones.

Obviously, this animal was another sauropod. But it had weird proportions. Most sauropods found before the year 1900 had forelimbs that looked much shorter than their hindlimbs.

Yet the situation was reversed here. Riggs was fascinated by the right humerus — or upper arm bone — that came with the skeleton. At 6 feet (2 meters) in length, it wasslightly longerthan the dinosaur's right upper leg bone (i.e., femur), which was also preserved.

In a1901 articlein the journal Science, Riggs said the "extraordinary length of the humerus" and some other bones "suggests an animal whose shoulders would rise high above the pelvic region, giving the body something of a giraffe-like proportion."

Two years later, in 1903, he named the "new" animalBrachiosaurus altithorax. The genus name,Brachiosaurus, means "arm lizard" whilealtithorax— the dino's species name — roughly translates to "deep-chested." Nice and descriptive.

Time for a plot twist. Between 1909 and 1913, German scientists working in East Africaremoved225 tons (or 204 metric tons) of fossils from Tanzania's Tendaguru Formation. (Mainland Tanzania was part of a German colony back then.)

Thepièce de resistance? Another massive sauropod skeleton.

Unlike the decapitated Colorado specimen, this individual came with a (partial) skull. Plus, most of the ribs and vertebrae were recovered. Dinosaur specialistWerner Janenschidentified the bones asBrachiosaurusmaterial. Eventually, these fossils were assigned to a new species:Brachiosaurus brancai.

That Old World giant stretched over 82 feet (25 meters) long — and could've carried its head almost 44 feet (13.3 meters) off the ground!

Crucially,Brachiosaurus brancaigavepaleoartistsmore fossils to work with than North America'sBrachiosaurus altithoraxever did. The effects team behind "Jurassic Park" modeled theirBrachiosaurusdesignon the African species. Other artists did likewise over the years.

Then things got complicated. Gregory S. Paul, a renowned dinosaur illustrator, pointed out some anatomical differences betweenBrachiosaurus altithoraxandBrachiosaurus brancai在1988年。他声称这两个蜥脚类动物s were so distinct from each other that they really didn't belong in the same genus.

A 2009 study written by Michael P. Taylor of the University of Portsmouth (England) Paleobiology Research Group, published in the Journal of Vertebrate Paleontology,concurred.Brachiosaurus brancaihas since been reclassified and renamed; it's now known asGiraffatitan brancai.

Now that we've met Graffatitan, let's get to know the real Brachiosaurus, shall we?

Because of all the naming drama,Brachiosaurus altithorax— the dinosaur Elmer Riggs described in 1903 — is the onlyBrachiosaurusspecies experts currently recognize.

Brachiosaurushad a tail that was both longer and taller thanGiraffatitan's. Also, as Taylorwrotein 2009, it "carried a greater proportion of its mass on the forelimbs." Hey, if you've got extra-large arms, you might as well use 'em.

There's no doubt thatBrachiosauruswas a hefty beast. One2017 paperpublished in the journal "Palaeontology" gave a mass estimate of 64 tons (58 metric tons) forBrachiosaurus.Other researchers think the dinosaur was lighter, perhaps tipping the scales at 44 tons (40 metric tons) or so.

Judging by the known fossils,Brachiosauruswas probably around 80 feet (24.5 meters) long. At the shoulder, it may have stood 20 feet (6.2 meters) tall, though its head could be lifted much, much higher.

The exactshapeof that head is debatable. ApossibleBrachiosaurusskull在科罗拉多州中部出现在1880年代。豪ver, apart from a single neckbone (which was accidentally destroyed), the head was found in isolation. So as of this writing, there's no way to be sure if it belonged to aBrachiosaurusor some altogether different sauropod.

BesidesBrachiosaurus, there were loads of other long-necked dinos stamping around North America during the Late Jurassic Period.

Prehistory buffs should be well-acquainted with theMorrison Formation. Internationally famous for its rich fossil record, this is a geologic sequence of 155 to 148-million-year-old shales, sandstones and limestones.

The Morrison runs all the way from Montana and the Dakotas to New Mexico and Arizona.Brachiosaurus altithoraxis just one of the many sauropods that've been found in these rocks.

By some counts, about 30 distinctive sauropod species lived in what’s now the Morrison Formation. These included the whip-tailedDiplodocus carnegii, the boxy-skulledCamarasaurus lewisiandBrontosaurus excelsus, aka: the 'Thunder Lizard.'

It's fun to think about how such giant animals could've coexisted — although you should know that not all of the sauropods represented in the various Morrison deposits lived at the exact same time.

As forBrachiosaurus, the good old "arm lizard" still makes headlines now and then.

A juvenile sauropod found at a Wyoming quarry wastentatively identifiedas a youngBrachiosaurusin 2012. Measuring around 6 feet (2 meters) long, the little tyke would've been a far cry from the Colorado titan Riggs and Menke discovered. Like they say, big things have small beginnings.