(Source: Corbis)
Yea, you dino lovers don't know how to act; this is one big herbivore and that's a fact

Elmer Samuel Riggs was wrong.  That's the conclusion of an extensive phylogenetic analysis of members of the sauropod family (suborder: Sauropodomorpha).

I. A Landmark Find

Hulking herbivores, the Sauropods lumbered about the Earth roughly 150 million years ago during the era in which dinosaurs dominated the terrestrial plane.  With a distinctive long neck and tree-trunk thick quadruped legs, the sauropod was the reptilian equivalent of a super-sized giraffe-elephant hybrid.

Among the most iconic sauropods was the heavy-headed "Brontosaurus".  The name is a proper Greek name -- the bronte bit means thunder, while the more ubiquitous sauros is the Greek word for "lizard."  The first Brontosaurus -- with a genus/species designation Brontosaurus excelsus -- was discovered in the late 1800s at Wyoming's Morrison Formation rocks at Como Bluff when Yale College paleontologist Professor Othniel Charles Marsh (O.C. Marsh) discovered a magnificent most complete specimen preserved in the ancient strata.

Cope vs. Marsh
"The bone wars" pitted the younger, but more prolific publisher Cope (left) against the wily veteran Marsh (right).  It was Professor Marsh who discovered the Brontosaur, gaining a key leg up in the research race. [Image Source: Slate]

At the time of his discovery of the Brontosaur, O.C. Marsh was knee deep in "the bone war"  -- a gentleman's battle with his contemporary, University of Pennsylvania Professor Edward Drinker Cope.

Marsh would eventually win the bone war discovering 80 species of dinosaur compared to the 56 found by Cope.  That loss would compel Cope to much bitterness in his later years.  But in reality both men stand as incomparable, archetypal giants of science.  Both Marsh and Cope share in the glory of being the forefathers of modern paleontology.

Prominent 19th century naturalist painter, Charles R. Knight offered up this imaginative depiction of the Brontosaur. [Image Source: Wikimedia Commons]

This week part of that glory was restored when a trio of top European dino researchers -- Professors Emanuel Tschopp (Universidade Nova de Lisboa ("NOVA") (Portugal); Museu da Lourinhã (Museum of Lourinhã) (Portugal); and Università di Torino ("Unito") (Italy)), Octávio Mateus (NOVA; Museu da Lourinhã), and Roger B.J. Benson (University of Oxford) -- published a lengthy review arguing fairly conclusively for the restoration of the Brontosaurus as a distinct genus.  Their work was published in the peer-reviewed journal PeerJ and is being haled as the most exhaustive analysis to date.

II. Fall From Grace

The degradation of the long-necked dinosaur took place in 1903 when Riggs wrote a compelling commentary arguing that the specimen was part of an already discovered genus.  At the time Riggs was working as a mid-level researcher at the Andrew Carnegie-funded American Museum of Natural History (AMNH) in New York City, but already held substantial sway.  Reviewing Marsh's restored "Brontosaurus" skeleton he concluded that it was only mildly different from the already discovered Apatosaurus.  

The Brontosaurus (seen in green) was shorter and stockier than the previously discovered Apatosaurus ajax (orange). [Image Source: Wikimedia Commons]

In a commentary in the Geological Series of the Field Columbian Museum he concluded:

In view of these facts the two genera [Brontosaurus and Apatosaurus] may be regarded as synonymous. As the term 'Apatosaurus' has priority, 'Brontosaurus' will be regarded as a synonym.

In effect, he was arguing that Marsh had goofed up in claiming the discovery of the new genus.  The argument stuck, in part, because of Riggs' rise in prominence (he would later become curator of the Field Museum of Natural History in Chicago, Illinois).  And with that the Brontosaurus was downgraded from its own genus to the species name Apatosaurus excelsus.

Marsh's sketch of the Brontosaurus was remarkably accurate and insightful.
[Image Source: O.C. Marsh/Wikimedia Commons]

The Apatosaurus was, as it turns out, was also a discovery of Marsh.  In 1877 he had unearthed from the Morrison formation the first member of the genus, Apatosaurus ajax, two years prior to his Brontosaurus discovery.  Two years later, in 1879, Marsh would find the Brontosaurus (Brontosaurus excelsus) in the same formation.

One thing most scholars agree on today is that some criticism of Marsh and Copes' preliminary findings was warranted.  The pair to some extent were blinded by their competition and lust for the prestige of discovery.  Each was known to make some embarassing mistakes and the Brontosaurus naming was hardly the only contentious preliminary opinion published by the pair.  To the dejection of Marsh, the term Brontosaurus might have faded into the mist of memory were it not for a single fateful decision.  

[Image Source: Getty Images]

The difference maker came in an ironic personage-- Professor Henry Fairfield Osborn, a prominent early paleontologist who held positions at Princeton University and Columbia University before becoming curator of vertebrate biology at the American Museum of Natural History, New York.

While Osborn was typically a critic of Marsh's mistakes, when it came to the Brontosaurus he made the unusual decision of bucking the prevailing opinion published by Riggs and chose to label the skeleton "Brontosaurus" not "Apatosaurus".  Given the prominence of the skeleton, the fateful choice ensured the enshrinement of term in popular culture, if not phylogeny.

While scientists long demured the dino as an Apatosaurus, its museum placard read -- "Brontosaurus" and the name was enshrined in popular science culture. [Image Source: Wikimedia Commons]

Riggs downgrade would stand more or less unchallenged for a century, until the recent review.  Looking at 477 anatomical traits the review offered a fresh, quantitative look at not just the Brontosaurus but other questionable Sauropod clades as well.  Looking at 81 sauropod specimens it examined each of the hundreds of anatomical features.  If the the species had at least 20 percent different traits from other specimens it was declared to be a new genus.

III. Call it a Comeback

And lo and behold the Brontosaurus passed the benchmark.  The authors summarize their key proposed changes to the phylogenetic tree, writing:

"Of particular note is that the famous genus Brontosaurus is considered valid by our quantitative approach. Furthermore, 'Diplodocus' hayi represents a unique genus, which will herein be called Galeamopus gen. nov. On the other hand, these numerical approaches imply synonymization of 'Dinheirosaurus' from the Late Jurassic of Portugal with the Morrison Formation genus Supersaurus." 

Under the new proposal, both the Apatosaurus and Brontosaurus would be lumped under a new subfamily -- Apatosaurinae -- but are expected to be considered separate genera.

Brontosaurs specimen
The original Brontosaurus specimen is today housed at Yale's Peabody Museum.
[Image Source: Wikimedia Commons]

The exhaustive analysis didn't carry solely good news for Marsh's legacy.  It did conclude that Marsh's Brontosaurus amplus specimen discovered in 1881 was likely just another specimen of the same Brontosaurus species he discovered two years prior.

On the flipside, an additional upgrade came in the form of a new genera paying homage to the Brontosaur name -- Eobrontosaur.  The upgrade was awarded to the species Apatosaurus yahnahpin, which will now be known as Eobrontosaur yahnahpin.

Brontosaurus Clade diagram
The Brontosaurus is prominently positioned in the newly proposed revised sauropod clade diagram (a phylogenetic "family tree"). [Image Source: Jason Mick/Wikimedia Commons/PeerJ]

Was the comeback a surprise?  Indeed it was.  In an interview with Wired magazine Professor Tschopp observed:

We were very surprised when we got these results that brontosaurus was valid again.

Only time will tell whether the thunder lizard label is here to stay.  But things are looking promising thanks to the exhaustive review in support of the naming comeback.  London Natural History Museum paleontologist Professor Paul Barrett (not a coauthor) told BBC News:

The author finds a number of ways in which the original specimens of brontosaurus and apatosaurus can be separated from each other.

Shakespeare wrote in the play Romeo and Juliet that a rose by any other name would smell as sweet.  But when it comes to the romantic appeal of lumbering extinct reptiles, it's hard to deny that a big part of cachet is carried in a catchy name.  And the Brontosaurus has a catchy one at that.

Sources: PeerJ, Wired, BBC News, via USA Today

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