Brontosaurus is Back!

Bulletin: Heads-up - Ol' Bronto is back!

For Real? What does that really mean? How "back" IS Brontosaurus?

There has been much ado about Brontosaurus lately. Namely, the news of a recent large survey of sauropod dinosaur fossils, published April 7, 2015 by Emanuel Tschopp​, Octávio Mateus and Roger B.J. Benson in the open-access journal PeerJ. This study led its researchers to reassess the demotion of Brontosaurus to invalid status over 100 years ago. Although not accepted by all paleontologists, this recent study determined that Brontosaurus is, in fact, a valid genus after all, distinct from Apatosaurus. Result: Brontosaurus should not have been relegated to being a subspecies of Apatosaurus, but is a distinct genus. 

The naming protocol in naming dinosaur species and genera is that the first name has precedence over subsequent names: if it's determined that two differently named genera or species are actually the same genus or species, then the first-named genus or species sticks and applies to both. 

That's what happened to Brontosaurus, which was originally named in 1879 by its discoverer, Othniel Charles Marsh, as a distinct genus, Brontosaurus excelsus. However, Marsh previously named another discovery two years before this, Apatosaurus ajax, in 1877. In 1903, it was decided that Brontosaurus was actually a subspecies of Apatosaurus - in other words the two dinosaurs were essentially synonymous - one and the same. Apatosaurus was named first, so had precedence and won-out over Brontosaurus in the battle of the names. Henceforth, officially considered a species of Apatosaurus, Brontosaurus lost it's name - until further notice. And, in the process, Ol' Bronto lost it's head - literally. And it turns out the battle was more than in "name" only...

Camarasaurus skull and head life restoration = original but incorrect head of Brontosaurus 

(pre 1970s)

Apatosaurus skull and head life restoration = still the correct head of Brontosaurus 

(1970s-current)

In 1905 - just two years after being officially reclassified as Apatosaurus, Brontosaurus became the first-ever mounted skeleton of a sauropod, exhibited by the American Museum of Natural History (AMNH). Ironically, this great institution decided to label the exhibit Brontosaurus - to capitalize on the famous and popular name - despite Apatosaurus being the newly scientifically accepted name.

To complete the skeleton mount, bones were combined from multiple sauropod specimens, with most of the bones belonging to the namesake of the exhibit: Brontosaurus excelsus. But this nearly-complete skeleton lacked a key ingredient: a head. Since no confirmed skull existed for Brontosaurus, the museum had to improvise for the head. It was not known what the head of a brontosaur actually looked like. So the exhibit designers guessed. Brontosaurus was a very heavy, stoutly-built sauropod - in contrast to its relatively slender yet longer cousin, Diplodocus. Consequently, they assumed that the skull must have been equally stout and sturdy - unlike the elongated "delicate" head of Diplodocus. Therefore, the museum hand-sculpted a custom-designed skull based on the best available reference: the thickly-built, robust, blunt-nosed Camarasaurus skull found nearby the source site of the exhibit's brontosaur skeleton. It was a considered a safe bet that the features of the Camarasaurus skull would be similar to whatever skull Brontosaurus really had. Thus, the original head used in the first-ever brontosaur exhibit actually belonged to another, quite different, sauropod, Camarasaurus. Although incorrect, this went on to become the model for Brontosaurus going forward. The rest is history, as far as "Bronto" in pop culture is concerned.

Meanwhile, in 1909 an Apatosaurus skull was apparently found by the Carnegie Museum at Dinosaur National Monument (Eastern Utah/Western Colorado). The skull was found near a skeleton identified as the new species Apatosaurus louisae. The skull was very similar to the skull of Diplodocus - elongated with a narrow, flattened snout - unlike the stout, short-faced skull of Camarasaurus that was incorrectly hijacked by Brontosaurus. Interestingly, the new, Diplodocus-like skull was not used on the Carnegie Museum mount of Apatosaurus louisae, which was left headless, pending yet further proof.  In fact, the Carnegie mount was eventually crowned with - of all things - yet another incorrect, old-school, Camarasaurus skull in 1934 (virtually repeating the mistake made by the original AMNH Brontosaurus exhibit!), by misguided museum staff.

Much time passed without definitive apatosaur-brontosaur head upgrades. Finally, the Apatosaurus skull was formally referenced scientifically in the 1970s, when John Stanton McIntosh and David Berman redescribed the skulls of Diplodocus and Apatosaurus. They determined that the 1909 slender Diplodocus-like skull was accurately attributed to Apatosaurus; and in fact, many Diplodocus skulls may actually belong to apatosaurs. In 1979, the first true, slender Diplodocus-like, skull was mounted on an Apatosaurus skeleton, at the Carnegie Museum. In 2011, the first specimen of Apatosaurus was found articulated with a skull and its cervical vertebrae intact; comprised of an elongated, Diplodocus-like head and sharing a majority of skeletal features with those of the original, apatosaur "type-specimen", Apatosaurus ajax, discovered by Marsh in 1877. Apatosaurus was finally confirmed as possessing the elongated, flat-snouted head similar to Diplodocus. 

Throughout this journey, ever since being reassigned as Apatosaurus in 1903, the head of Brontosaurus has shared the fate of Apatosaurus. The mighty Brontosaurus was similarly verified as having the elongated, flat-snouted skull of Apatosaurus - not the old-school, stout, blunt-headed skull of Camarasaurus, that once was the hallmark of Ol' Bronto. And so things have remained, in name and form, until the study and status upgrade of 2015. As a result of this study, the Brontosaurus-as-Apatosaurus designation is called into question. The mighty Brontosaurus is back and "lives" again - sort-of...

Dino fans familiar with the classic, original image of the "Bronto" as a long necked sauropod with the stout, blunt-head cheered the resurrection of Brontosaurus as a valid genus. However, in key respects, the new "Bronto" is still not the same brontosaur portrayed in countless old-school life restorations in movies, TV cartoons, books - even the famous Sinclair gas station logo. The main difference between the original, "classic" brontosaur; and the newly, resurrected version, is all in the head....

There are many varieties of sauropods - all share the most basic morphological features of having proportionally long necks and tails, mounted on hefty torsos supported by four pillar-like legs. However, among the most distinguishing features differentiating species are the differences in the SHAPE of their HEADS...

The new 2015 study does nothing to restore the "classic" short-nosed, bluntly box-shaped head of the "classic" Brontosaurus familiar to generations of dinosaur fans. In fact, the "new" Brontosaurus is still firmly classified squarely in the same general group as Apatosaurus (family = Diplodocidae / subfamily = Apatosaurinae). So even if the newly resurrected classification of Brontosaurus sticks, it still won't LOOK like the original, familiar Brontosaurus possessing a stout, blunt-headed Camarasaurus head - the incorrect head attached to the original Brontosaurus mount that forever established the appearance of Brontosaurus in the public eye (despite having the incorrect head). Now - flying in the face of all the "Bronto is back" buzz - the newly resurrected brontosaur retains not the familiar (yet incorrect) stout-faced head of Camarasaurus, but the more elongated, flattened-snout head morphology of Apatosaurus - the very same Apatosaurus that bumped Brontosaurus from valid status back in 1903. Hence, since the head is among the most obvious, distinguishing characteristics differentiating sauropod dinosaurs, for all practical, empirical purposes - in terms of appearance - the newly resurrected Brontosaurus still remains more Apatosaurus than "Brontosaurus" - and according to some paleontologists, still actually IS Apatosaurus.