Much is being made of Brontosaurus. Brontosaurus is a genus name for a large dinosaur, known to watchers of “Land Before Time” as “Long-Necks.” That generic name dates to the 19th century, but in the early 20th century it was eliminated as a proper Linnaean term and replaced with Apatosaurus. This made us sad. Most people discover dinosaurs and learn all about a select handful of the iconic ones, including Brontosaurus, then later learn that Brontosaurs is a bogus name. And become sad.

But perhaps this sadness is all for naught, because a very recent study seems to require the resurrection of Brontosaurus (the name, not the actual beast), and that is happy, sad-killing news. Here, I’ll give you a bit of background and some thoughts on this. Don’t worry, I’m not going to tell you that you need to remain sad for some reason. In fact, I’ll argue that you never really had to be sad.

Naming Names: Apatosaurus vs. Brontosaurus

The title of this post is borrowed from Stephen Jay Gould’s essay published in his book of the same name in 1991, from which I draw quite a bit of the information for this first part.

In 1877, paleontologist O. C. Marsh published a skeletally brief description of a new genus of dinosaur found in the “Jurassic Formation” (properly called the Morrison Formation) in Colorado. He called it Apatosaurus ajax (“Notice of New Dinosaurian Reptiles from the Jurassic Formation,” American Journal of Science, 1877). Two years later, Marsh described a different find, a similar but larger dinosaur, which he named Brontosaurus (“Notice of New Jurassic Reptiles,” American Journal of Science, 1879). Both dinosaurs were quadrupedal, large, herbivorous beasts, differentiated primarily by size with Apatosaurus being about fifty feet long and Brontosaurus being about 80 feet long. (Note: The actual size of these dinosaurs varies in the literature. It will turn out that for dinosaurs, size probably matters but there is some disagreement about what exactly matters about it.)

From a public relations point of view, Brontosaurus had some advantages. It was much larger. In popular media bigness is best for a lot of things, especially dinosaurs. Brontosaurus as reported had a more complete set of bones, and it was mounted in a famous museum. (Eventually some form of it was mounted in all the famous dinosaur-focused museums that mattered, generally with that label: Brontosaurus). Marsh and others used Brontosaurus in major scientific overviews and popular commentary and reconstructions of the age. In his highly influential publication, “Dinosaurs of North America” (Sixteenth Annual Report of the US Geological Survey, 1895), Marsh penned:

The best-known genus of the Atlantosauridae is Brontosaurus, described by the writer in 1879, the type specimen being a nearly entire skeleton, by far the most complete of any of the Sauroiioda yet
discovered. It was found in the Atlantosaurus beds, near Lake Como, Wyoming, and the remains were nearly in the position in which they were left at the death of the animal. This fortunate discovery has done much to clear up many doubtful points in the structure of the whole group Sauropoda., and the species Brontosaurus excelsus may be taken as a typical form, especially especially of the family Atlantosauridae.

Marsh made the claim that Apatosaurus and Brontosaurus were separate but closely related genera. Remember that.

Decades after the initial discoveries of these extinct dinosaurs, Elmer Riggs of the Field Museum had a closer look at the accumulated material and, contributing to an emerging pattern of “lumping” species previously generated by the earlier generation of paleontological “splitters” (including Marsh), he sank Apatosaurus and Brontosaurus into one genus. He wrote, in 1903,

The genus Brontosaurus was based chiefly upon the structure of the scapula and the presence of five vertebrae in the sacrum. After examining the type specimens of these genera, and making a careful study of the unusually well-preserved specimen described in this paper, the writer is convinced that the Apatosaur specimen is merely a young animal of the form represented in the adult by the Brontosaur specimen.… In view of these facts the two genera may be regarded as synonymous. As the term “Apatosaurus” has priority, “Brontosaurus” will be regarded as a synonym.

And by “synonym” he means, sadly, extinct as a Linnaean term.

In this manner, Brontosaurus disappeared, although Brontosaurus lived on. The official genus Brontosaurs was no longer considered valid because of the rule of priority. The first name applied to a specimen is, under the rule of priority, chosen when it is discovered that more than one name is being used to describe the same genus or species. However, Brontosaurus (not italicized) managed to hang on and was widely used in museum exhibits and popular literature (both popular science and fiction), and eventually, film. One could argue that there is nothing wrong with this. A genus of dinosaur has a scientific name, but it can also have one or more popular names. The genus Apatosaurus could be said to have a couple of popular names, non-italicized “Brontosaurs” being one, another being “Long-Neck,” and maybe there are others.

But, since Brontosaurus and Brontosaurus have exactly the same spelling, one could also be concerned that science is being messed with here. The old extinct genus name should not only be set aside because of Rigg’s science, but the use of this term in any other context is an offense to rational thinking. How dare you use the term Brontosaurus! You must be a Creationist or something!

That problem, the fetishizing of the names, is apparently what gave Stephen Jay Gould the impetus for writing his essay Bully for Brontosaurus. He wrote the essay at the time that the United States Post Office issued its famous dinosaur stamps, which were artistic reconstructions by the famous John Gurche. I remember meeting Gurche at that time, after his stamps had been accepted for use but before they were printed, which was also about the time John was becoming famous for his Smithsonian reconstructions of early human ancestors. John had developed to an art the science of building up.

You start with a cast of a skull, then using a detailed and expert knowledge of anatomy, you add the muscle, fat, connective tissue, and eventually skin. Only the skin will be seen in the final product, even though the underlying tissues were all built with anatomical precision. The artist as anatomist does not really know in advance what the result will be, but when flesh is added in this manner to bone, the final product is arguably the best possible reconstruction that can be made. Skin color or markings and hair or fur are at that point largely conjectural, but the surface of the skin on down to the bone is based on the best available science.

Gurche’s stamps were important for several reasons. First, this was science on stamps, not a habit of the United States Post Office. Second, it was paleo-science on stamps, which is extra cool. Third, the stamps represented reconstructions of dinosaurs based on newly emerging science and method applying to both what we think dinosaurs were, and how we reconstruct extinct forms generally. Fourth, these stamps joined an all too small collection of US produced stamps that were not terribly boring to look at.

The stamps were also important for two other reasons, not quite as positive. First, the four dinosaur stamps included three dinosaurs and a Pteranodon. Pteranodons are not dinosaurs. Second, the giant sauropod (and of course there had to be a giant sauropod along with the large carnivorous thing and the roundish spiky thing, to represent the most popular groups of dinosaurs) was Apatosaurus but labeled Brontosaurus. And, yes, Brontosaurus, on the stamp, is in italics. It is not clear that this was proper Linnaean typography or just an artistic choice.

Following Gould, the first thing you need to now about the sinking of Brontosaurs into Apatosaurus is that it did not need to happen. If you troll around the Internet and read the stories about the resurrection of Brontosaurs (the name, not the beast) you will find the Rule of Priority cited again and again as the reason for that decision. But there are actually a few different “rules” that have applied to the naming of names in the Linnaean system, and Priority is only one of them. Read Gould’s essay for rich detail on this. Here I’ll just note that there is another rule that can apply: Plenary Powers. This comes into play when someone brings up a good reason (there are no rules about what the reason should be, just that it be a good one) to pick a certain name that may not have priority for a given genus or species. This is done in the plenary context of the governing body for animal names, the International Commission of Zoological Nomenclature. The commission consists of a largish number (about thirty) of zoologists. They hear the argument (much of this is done on paper) and vote. Gould cites a classic example.

The protozoan species Tetrahymena pyriforme has long been a staple for biological research, particularly on the physiology of single-celled organisms. John Corliss counted more than 1,500 papers published over a 27-year span—all using this name. However, at least ten technically valid names, entirely forgotten and unused, predate the first publication of Tetrahymena. No purpose would be served by resurrecting any of these earlier designations and suppressing the universally accepted Tetrahymena. Corliss’s petition to the commission was accepted without protest, and Tetrahymena has been officially accepted under the plenary powers.

Gould also cites the example of Boa constrictor, but I won’t cover that here. Go read the essay.

The point is, Rigg’s effort to sink Brontosaurus, presumably well intentioned and arguably appropriate, could have been overruled. But remember, Riggs reclassification happened in 1905, and while Brontosaurus as a term was well on the way to postage stamp level status, the cultural centrality of the term was probably not as well established as it would eventually become. It seems nobody came to bat for Brontosaurus. There are probably a number of reasons for that. They are probably mostly not very interesting.

The Post Office Vindicated?

Let’s look at the new study, “A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)” by Emanuel Tschopp, Octávio Mateus, and Roger Benson. It was published yesterday in the journal PeerJ.

“Diplodocidae” are the Long-Necks. This Linnaean family was called the Amphicoeliidae (by Cope, Marsh’s famous rival) in 1878, and the Atlantosauridae by Marsh (Cope’s famous rival) in 1877. (The story of these family names and the dinosaurs to which they refer is rather complicated, not covered here).

The study, hundreds of pages long, looked at 81 “operational taxonomic units” (OTUs) distributed among something over a dozen probable species dating to the Late Jurassic and Early Cretaceous. The research team examined a whopping 477 features. The OTUs consist of “name-bearing type specimens previously proposed to belong to Diplodocide” and other material. This approach starts out making very few assumptions about which bones belong which species, allowing the analysis to start out with less bias than otherwise possible. This is a modern cladistic analysis. This involves measuring or observing a large number of traits that are presumed to reflect the underlying genetics, and grouping corresponding bones based on similarity or equivalence of these traits. The result is one or more cladograms that should do a good job of representing a sort of family tree of probable species. I oversimplify.

Here is the key graphic representing the Brontosaurus related results, supplied by PeerJ:

The main result pertaining to the present discussion (though there are many other results from this important study) is that the specimens Riggs sank into one genus, thus setting aside Brontosaurus, are distinct. This requires that the term Brontosaurus be revived and applied. The iconic Long-Neck lives again (as a name, not an actual living dinosaur).

Does this vindicate Marsh and the US Post Office? As to the latter, probably not. It is highly unlikely that the US Post Office or those involved in making the Dinosaur stamps anticipated a revision of sauropod taxonomy. They were right to use the term Brontosaurus only in the way a stopped watch is right twice a day. But what about Marsh? That is a little more complicated. Marsh was working with a fraction of the material now available, and using that material, he separated Brontosaurus and Apatosaurus but did he do so correctly, based on the character differences that, if we take the new study as valid, turn out to matter?

Marsh distinguished Brontosaurus and Apatosaurus on the basis of a number of differences, but one of them was the overall robusticity of the animal, especially in the vertebrae. In “The Dinosaurs of North America” he wrote, Brontosaurus …

… aside from its immense size, is distinguished by the peculiar lightness of its vertebral column, the cervical, dorsal, and sacral vertebrae all having very large cavities in their centra. The first three caudals, also, are lightened by excavations in their sides, a feature first seen in this genus, and one not observed in the other families of this group.

The recent analysis does the same. Charles Choi, writing for Scientific American and quoting the study’s lead author, notes:

“Generally, Brontosaurus can be distinguished from Apatosaurus most easily by its neck, which is higher and less wide,” says lead study author Emanuel Tschopp, a vertebrate paleontologist at the New University of Lisbon in Portugal. “So although both are very massive and robust animals, Apatosaurus is even more extreme than Brontosaurus.”

In some details, Marsh may have been a stopped watch, but clearly not the important details. The old guy got it right, we can say. Cope would probably disagree on personal grounds, of course.

The lying lizard gets its due

People seemed to care that “Brontosaurus”, the name, be preserved, which implies preference over “Apatosaurus”. But why? Does one role off the tongue more easily than the other? Is one more poetic than the other? The main reason for sadness when learning that Brontosaurus is wrong is almost certainly, as has been pointed out by many, because the term was already so much in use that it is usually learned first and nobody likes to unlearn things. But it is interesting to ask of the etymology of the terms. In another essay (or two) Stephen Jay Gould laments the demise of a different genus name, Eohippus. Eohippus means “Dawn horse” and was applied to an early horse fossil. What a great, and appropriate, name! But other remains of that same extinct form had previously been named Hyracotherium. Hyracotherium is an affront to the poetry of paleontology for three reasons, when compared to Eohippus. First, it sounds ugly. Second, it is an example of a cool name (“Dawn Horse”) being tossed out. Third, Hyracotherium is wrong. The term comes from the belief that those particular early remains were a form of hyrax, which is not a horse. Tossing out Eohippus and replacing it with Hyracotherium may have been correct by the Rule of Priority but a third rule, not previously mentioned here, could have saved the day: The Rule of Appropriateness. Hardly invoked and considered these days arcane, that rule simply stands up for a name that makes sense over a name that does not, clearly the case with the early horse.

But what about the Long-Neck in question? Gould ends his essay with these words:

Apatosaurus means “deceptive lizard” Brontosaurus means “thunder lizard” — a far, far better name… They have deceived us; we brontophiles have been outmaneuvered. Oh well, graciousness in defeat before all (every bit as important as dignity, if not an aspect thereof). I retreat, not with a bang of thunder, but with a whimper of hope that rectification may someday arise from the ashes of my stamp album.

Well said. But, in the end, not relevant. A better reference than to dignity might be to a very different aphorism, “Don’t get mad. Get even.” It took a while, but Brontosaurus is back.

For now. As great as the new study is, there are a couple of reasons that things may change again. One is our understanding of the relationship between size and form, and actually, growth in dinosaurs. It could be that some features that work to distinguish specimens cladistically are a function of change over time within a given animal, as it grows larger. This, or some other developmental or environmental effect, could knock some of the traits off the pedestal of genetic presumption, and make them invalid cladistic characters, and thus change the analysis. I mention this simply because the main features that result in bringing Brontosaurus back to life (the name, not the actual dinosaur) may be size related. Another possibility is that even though Apatosaurus and Brontosaurus are found in this study to be different, they are still close. If this research team turns out to be splitters and later on lumpers show up with more muscle, some of the now distinct taxa could be recombined, and any two closely aligned forms risk sinking, once again, into the Davy Jones’ Locker of the Linnaean system. Of course if that becomes a threat, there may be grounds, and impetus, for invoking the Plenary Rule.

I’ll end with this, somewhat tangental but I think important. The reason Gould wrote his “Bully” essay was annoyance. Gould was motivated by annoyance, by the way, in many of his popular works. He was annoyed at the way science was often portrayed in watered down form, and he was annoyed at the shallowness of the public discourse. Had he lived longer, he almost certainly would have gotten much, much more annoyed because this has become more, rather than less, of a thing because of the Internet. A simple example of this is the widespread mischaracterization of the Rule of Priority as the only thing governing resolution of naming conflicts. In the case of the “Bully” essay, Gould was annoyed at the annoyance of others with the Post Office stamps. Aping, cynically, classic conspiracy ideation, he wrote:

The Post Office has been more right than the complainers, for Uncle Sam has worked in the spirit of the plenary powers rule. Names fixed in popular usage may be validated even if older designations have technical priority. But now…Oh Lord, why didn’t I see it before! Now I suddenly grasp the secret thread behind this overt debate! It’s a plot, a dastardly plot sponsored by the apatophiles—that covert society long dedicated to gaining support for Marsh’s original name against a potential appeal to the plenary powers. They never had a prayer before. Whatever noise they made, whatever assassinations they attempted, they could never get anyone to pay attention, never disturb the tranquillity and general acceptance of Brontosaurus. But now that the Post Office has officially adopted Brontosaurus, they have found their opening. Now enough people know about Apatosaurus for the first time. Now an appeal to the plenary powers would not lead to the validation of Brontosaurus, for Apatosaurus has gained precious currency. They have won; we brontophiles have been defeated.

But more important than that, Gould underscored the importance of non-shallowness, of context, in understanding problems suffered by the likes of *Brontosaurus” (the name…), and he produced a message that in slightly modified form should go out to all those engaged in discussions of science, history, and other things, which are typically carried out on the slippery surface of very deep intellectual waters. “If you play this dangerous game in real life, remember that ignorance of context is the surest mark of a phony. If you approach me in wild lament, claiming that our postal service has mocked the deepest truth of paleontology, I will know that you have only skimmed the surface of my field.”

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