A T. rex by any other name

Somewhere, in the deep recesses of some closet, I have at least one set of dinosaur-themed U.S. Postal Service 1989 stamps. These little gems may have been forgotten by many, but I can still remember the controversy when they came out (and I faintly remember a TV commercial advertising them, although it could very well be a figment of my imagination). You see, during my childhood one of the names nearly synonymous with the term “dinosaur” was Brontosaurus, the “thunder lizard.” It never failed to make a pop-culture appearance when dinosaurs were involved, even the popular term “the terrible thunder-lizards” owing its origin to Brontosaurus. Then we found out that the skeleton had the wrong head.

Although there is some debate over whether it was O.C. Marsh or Yale professors at the Peabody Museum who made the call, it was reasoned that the mounted skeleton of Brontosaurus was so massive that it could not have had a delicate Diplodocus-like head; the more robust skull of Camarasaurus was thought to be a fitting replacement until the right head was discovered. Such was the beast that I remember fondly from my first visits to the American Museum of Natural History, but it was not to last; eventually it came to light that Brontosaurus was really an Apatosaurus, and a skull-change was in order. This “mix-up” (which was, in reality, essentially a refuted hypothesis) became widely known, and so when the stamps came out depicting a “small-headed” Apatosaurus with the name Brontosaurus, many were quick to criticize the loss of one of the most familiar names in paleontology. Brontosaurus surely was an icon, and the name still is in usage to some extent today, but the mistake was made clear and accuracy in nomenclature had to trump popularity (else Apatosaurus would have been dropped and changed to Brontosaurus, which would completely reverse ICZN methodology).

Sauropods aren’t the only dinosaurs that occasionally suffer from a potential identity crisis, however. It was found that a Megalosaurus bone was re-described under a pseudo-binomial Scrotum humanum (see my post The Dragons of Eden for more on this), but fortunately the ICZN regarded the designation a “forgotten name” and no change was made. The tale of Manospondylus is a little more complicated, however, and threated to give a new moniker to the “king” of the dinosaurs.

In 1917, Henry Fairfield Osoborn published a paper entitled “Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus” in the Bulletin of the American Museum of Natural History, recognizing that two vertebrae (one of which had gone missing) named Manospondylus gigas by Cope in 1892 were likely to be vertebrae from Tyrannosaurus rex. He wrote;

The genotype (Amer. Mus. Cope Coll. 3982) of Manospondylus originally consisted of two dorsal vertebrae, which Cope recorded verbally to Hatcher as from South Dakota. Of these original two dorsal vertebra one was figured by Hatcher and correctly referred to the Theropoda. Unfortunately the remaining vertebra has been misplaced in or lost from the American Museum collections. It most nearly resembles in size and other characters the posterior cervical or first dorsal of Tyrannosaurus rex (Amer. Mus. 5866). This type is so incomplete and so imperfectly preserved that the genus and species which were founded upon it are regarded as indeterminate.

When was Tyrannosaurus rex named? In 1905, by Osborn himself, and so Manospondylus would have priority over Tyrannosaurus if the remains were indeed from the same animal. If there was any conflict, it was largely forgotten, at least until the year 2000 when members of the Black Hills Institute found more material that could have come from the same skeleton Cope had gotten his vertebrae from, leaving little doubt that the animal in question was a Tyrannosaurus. While it is true that Cope’s bit of skeleton was not diagnostic and the name Manospondylus only described a small piece of skeleton, it did come before Osborn named the same animal Tyrannosaurus. It would take a lawyer to successfully unravel the rat’s nest of jargon on the ICZN priority page, but the simple version is that there was essentially no threat to Tyrannosaurus. The name Manospondylus gigas was not widely used (if at all) and Tyrannosaurus rex has more than enough references within the last 50 years to give it an essential “protected status,” and even if it were to be formally challenged I can’t imagine the ICZN overturning one of the quintessential dinosaur names because of one worn piece of vertebra.

While the Manospondylus controversy evoked the most attention, the animal known as Tyrannosaurus rex has been described under other names, especially in the days of Cope and Marsh. While I won’t get into the Tarbosaurus=Tyrannosaurus debate here (have a look at this paper, if you’re interested), there is certainly plenty to talk about. Indeed, in a great case of coincidence, Henry Fairfield Osborn announced Tyrannosaurus rex as a new genus and species in the very same paper that he describes Dynamosaurus imperiosus, which later turned out to be synonymous with Tyrannosaurus. It is important to note, however, that if Osborn described Dynamosaurus before Tyrannosaurus in the paper, we would have a different name for one of our most iconic dinosaurs.

Likewise, two more recent entries Stygivenator and Dinotyrannus (both named by George Olshevsky in 1995) have both been found to by synonymous with Tyrannosaurus, although I have to admit I had never heard of them and it seems that Olshevsky is a little “out-there” judging by his “birds came first” hypothesis of dinosaur evolution.

So why all this confusion? Why are so many tyrannosaurs being synonymized, reshuffled, brought-back, etc.? Part of the problem lies with their teeth, which are far more numerous than the rest of the skeleton. Given the amount of teeth found, plus the propensity to name nearly every fossil as a new species, the diversity of these dinosaurs quickly became inflated, creating a tangle of Deinodon, Dynamosaurus, Gorgosaurus, Dryptosaurus, Aublysodon, and Laelaps that is still giving us some trouble today (while they’re likely synonymous with other named tyrannosaurs, Deinodon [=Gorgosaurus?] and Aublysodon [=various tyrannosaurids?] are still kept separate until more diagnostic features can be found). Just have a look at the AMNH paper or any of the entries for these animals; they comprise a mountain of genus and species names, sometimes indicating how dubious names were folded into other dubious names.

While most of the above mentioned names have caused more headache than actual controversy, skeletal remains of what appeared to be a small tyrannosaur (originally believed to be the skull of an Albertosaurus) caused quite a stir in 1988. Nanotyrannus lancensis seemed to be a pygmy tyrannosaurid, although there was much disagreement about whether it was really a new dinosaur or merely a juvenile of a known species. The controversy heated up again in 2001 with the discovery of “Jane,” another small tyrannosaur that seemed to raise the same questions as the 1988 specimen. While some argued that Jane was a large Nanotyrannus, it became understood that Jane was a juvenile Tyrannosaurus rex. The debate will probably show up again whenever another small tyrannosaurid skeleton comes out of the ground, but I agree with the juvenile T. rex hypothesis more than the Nanotyrannus hypothesis.

There are likely plenty more tyrannosaurids to be found, however, and while the North American genera like Tyrannosaurus, Albertosaurus, Gorgosaurus and Daspletosaurus may be the most familiar, new varieties have been coming to light like Dilong paradoxus and Guanlong wucaii from Asia, Eotyrannus lengi and Aviatyrannis jurassica from Europe, as well as Stokesosaurus clevelandi and Appalachiosaurus montgomeriensis from North America. The discovery of these dinosaurs fill in some gaps in our understanding of tyrannosaurs while creating others, and as more fossils come to light the name game will continue to be played, especially with skeletons where largely incomplete specimens are known. Be that as it may, we can rest assured that the dinosaur that lends its name to the group will remain in place, and Tyrannosaurus will likely continue to be one of the great dinosaur icons for a long time to come.

End Note: If you have not done so, please check out Stephen Jay Gould’s essay “Bully for Brontosaurus” (collected in a book by the same name).

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