2. Naming the New Genus

In 1986, nearly a year after our Father's Day excavation, I was awarded a grant from the Smithsonian Institution. Its "short-term visitor" program encourages scientists to study the Smithsonian collections. At the Smithsonian I studied the sauropod dinosaurs and accumulated critical measurements for comparison of Diplodocus and other dinosaurs with the bones of Sam. I extended the travel on that grant to include the American Museum of Natural History (New York City) and the Carnegie Museum of Natural History (Pittsburgh), where the most important specimens of the sauropods Diplodocus, Apatosaurus, and Barosaurus are on display and in study collections.

The information I gathered on this extended travel proved instrumental in my determining the uniqueness of the new bones from New Mexico, and it gave me a firm basis for making size comparisons. According to all comparisons I could make with Diplodocus and Apatosaurus, Sam would be considerably longer, and probably larger in all dimensions. I thus knew we faced a colossal excavation if the bone fragment indeed marked the position of the tail and would lead to the remainder of the skeleton.

Among dinosaurs, sauropods were both the largest and the most conservative. With long necks, long tails, capacious rib cages, and legs like pillars, sauropods changed little physically from the time of their first appearance more than two hundred million years ago (early Jurassic) until their extinction, along with all the other dinosaurs, sixty-five million years ago (end of Cretaceous). They were always enormous and they were all plant eaters. A 1990 summary by J. S. McIntosh lists most of the currently accepted genera of sauropods, along with their ages, principal localities, and comments concerning distinguishing features. (Seismosaurus was not included in that list because its formal description had not then been published.)

Sauropods like Sam flourished in the Jurassic and reached their zenith in diversity at the end of that period, roughly one hundred fifty million years ago. Sam was one of many kinds of sauropods that lived in the late Jurassic. Skeletons of late Jurassic sauropods occur in (relative) profusion in western North America, principally in the Morrison Formation, and in eastern Africa in the Tendagaru beds of Tanzania. The Jurassic Period could well be called the Age of Sauropods.

Sauropods never recovered from a decline that began in the early Cretaceous when angiosperms (flowering plants) began to replace the conifers, cycads, and ferns that had dominated earlier landscapes. Perhaps sauropods survived in the ever-dwindling archaic habitats, while other herbivores with adaptations better suited to feeding on angiosperms replaced them as the dominant plant-eaters of the Cretaceous. Their ultimate disappearance at the end of the Cretaceous scarcely affected the course of history, for their abundance and diversity had diminished so severely that their scant contribution to the dinosaur world at the time of the great extinction could be easily overlooked.

More than 90 genera and 150 species of sauropods have been named, but only a few are relatively well known scientifically. Typical among the Jurassic sauropods was the genus Camarasaurus , a stout animal with relatively short neck and tail. Apatosaurus (as Brontosaurus  has been renamed) and Diplodocus belong in another family, differing in their exceptionally long necks and tails and more delicate skulls. All these giants lived in the western United States, likely roaming in herds and feeding constantly on conifers, cycads, and ferns. The weight of most sauropods typically approached twenty tons, with the heavily built Apatosaurus weighing considerably more. Barosaurus, a close relative of Apatosaurus and Diplodocus, had an exceedingly long tail, sometimes described as a whiplash.


The type locality of Seismosaurus in the Ojito Wilderness Study Area northwest of Albuquerque, New Mexico, and the Dry Mesa Quarry southeast of Delta, Colorado--the type locality of Ultrasaurus macintoshi,  Supersaurus viviani,  and Dystylosaurus edwini.

Skeletons of the giants (Camarasaurus, Apatosaurus, Diplodocus, Barosaurus) suitable for display in the great museums were among the trophies sought by collectors during the rush for dinosaurs in the American West during the late 1800s and early 1900s. Casts of Diplodocus were traded to museums around the world, making it one of the most well-known dinosaurs. Today, visitors can see partially articulated skeletons of these and other dinosaurs on display in situ, locked into the sandstone from the Jurassic river bed in which they were buried. This spectacular demonstration of dinosaur bones at Dinosaur National Monument, on the border of Utah and Colorado, documents one of the most productive sites for Jurassic dinosaurs in the world.


Skeletal reconstruction of Diplodocus carnegii,  probably the closest known relative of Seismosaurus.  This slender sauropod is known from essentially complete skeletons from the Morrison Formation. Its skeletal anatomy is well established, and it formed the basis for most comparisons with Sam's skeleton.

Mounted skeletons of sauropods now grace the halls of museums around the world. Increasingly, these skeletons are replicas made from original reconstructions. And original reconstructions themselves are not the real thing; they are most often a potpourri, a single skeleton made from isolated bones--often from several individuals. Reconstructions of skeletons are not the same as restorations. These two terms have very different meanings. For example, John Harris distinguishes them in this way: "the term reconstruction  is used in the sense of piecing together the original but often fragmentary fossilized parts of extinct animals, whereas restoration  is used to describe the depiction of their original appearance--muscles, flesh, skin, and all." Thus, a reconstruction is a skeleton, and a restoration is the animal in the flesh, as though living. Animated restorations, which depict dinosaurs in their flesh-and-blood glory with movements controlled by computers, draw huge crowds. Artists' paintings, meanwhile, have long re-created the living animals in their habitats--giving them a lifelike quality that is sometimes so realistic that they seem to be photographs taken by a camera loaded with fast, color-saturated film.

But the real nuts-and-bolts of the dinosaur world is skeletons and the sites from which the skeletons have been recovered. The real natural history of dinosaurs resides there, in the bones and the collecting localities, the only sources for the raw material of dinosaur studies. The Smithsonian grant gave me the opportunity to study the real bones of some of Sam's relatives. This award was pivotal in the project, and it led to the other, larger grants that made excavation beyond the discovery stage possible.

Before I went to the Smithsonian, I thought Sam was a member of the genus Diplodocus, a well-known and widespread dinosaur in the Morrison Formation of Utah, Colorado, and Wyoming. But I had trouble matching the eight tail vertebrae we had collected during our initial excavation to known tails of Diplodocus. The proportions were off, the dimensions were too large, and the anatomical details were different enough to question the identification of Sam as Diplodocus. The possibility surfaced: maybe it's a new dinosaur. The fact that the site is hundreds of miles from other Diplodocus localities in the Morrison Formation added to the uncertainty.

Eventually I came to believe that Sam could not be Diplodocus or kin such as Barosaurus or Apatosaurus. The tail bones of Apatosaurus do not have a deep concavity on their undersurface. The tail bones of Barosaurus have the deep concavity, like Sam's, but the vertebrae are relatively short. The closest resemblance was to Diplodocus, but the differences were still too great. Notably, Sam's vertebrae are proportionally longer and taller, and the dorsal spines are nearly erect, quite in contrast to the tail vertebrae of Diplodocus. When I consulted with other sauropod specialists, they were unable to offer any new information or interpretations that I had not already considered. I thus concluded that Sam belonged to a hitherto unrecognized species of dinosaur.

When the New Mexico Museum of Natural History decided to announce the existence of this new and impressive dinosaur to the public later in 1986, I faced a dilemma. We needed a name for the skeleton, and I could not assign it a name based on any known dinosaur.

The paleontologist who first describes a fossil as a new species has the singular responsibility and honor of selecting the name. By international convention, the name should be latinized according to a universal standard adopted by all zoologists, The International Code of Zoological Nomenclature.  Its contents read like a legal document, and issues related to naming of animals resemble court cases.


Muscular anatomy of Diplodocus carnegii . This kind of drawing is a prerequisite for producing a reasonable in-the-flesh restoration. Seismosaurus was similar, but had more massive hips, stouter (but not longer) legs, and a tail that differed in some important ways.

The choice of name--the technical name--for a dinosaur, or any fossil organism, is as important to a paleontologist as naming a newborn is to a parent. We cannot take the matter lightly, because the technical name will stay with the species forever. Sam and all Sam's kind would be known by the technical name. The name should have meaning; ideally it should also be easy to remember and pronounce. And it should be constructed using the agreed-upon rules designed just for this purpose. In some ways the honor of coining the name is the most pleasant of our responsibilities.

That summer, before the press conference organized by our museum staff, I lay awake at night in my cabin in the mountains east of Albuquerque, deliberating. I pored over my dictionary of scientific names, seeking an appropriate root to combine with -saurus  in keeping with the tradition of Apatosaurus, Barosaurus, Camarasaurus, and dozens of other dinosaurs named under this convention.

After several weeks of searching for a name, I made a decision. I chose Seismosaurus. Seismo  is the Latin root for "shaking." It is familiar in words like seismic  and seismology , all relating to ground-shaking generated by earthquakes or underground blasts. Sam would be the earth-shaking dinosaur. I searched the technical literature to ensure that this name had not already been taken; if so, the name would have been "preoccupied" and not available for any newly discovered species.

I was lucky. Seismosaurus hadn't been used before; my first choice was available. As long as I didn't attach a species name to this informal genus, any publication of the name in print would be safe from technical nullification--provided I was right that Sam was a new genus. I would use this name in the press conference.

Floodlights blinded me, and the array of microphones seemed like menacing tentacles of a giant octopus. Paleontologists are not trained in graduate school for press conferences. I briefly explained what we had found, unveiled the bones, and revealed the new informal name. I reported that this individual of Seismosaurus was probably at least 110 feet long, comparing it with our own mounted skeleton of Camarasaurus (which is only about 50 feet long.) This put Sam in the ranks of the supergiants, not the giants.

I then demonstrated how I made that calculation by direct proportions with Sam's closest relative, Diplodocus. Each vertebra was at least 20 percent longer than corresponding vertebrae in Diplodocus, and with the disproportionately tall neural spines, there was the possibility that the overall length of the tail (and indeed the entire body) was also disproportionately long. Although I had data in hand that indicated a more likely length of 120 feet or more, I chose to conservatively estimate Sam's length at 110 feet--which is longer by 23 feet than the longest specimen of Diplodocus, the previously accepted longest dinosaur. (Later I would revise these figures upward.)

Questions came from all directions as each reporter sought a different angle to develop. Sam's new name, Seismosaurus, caught on immediately, capturing the reporters' imaginations. One reporter asked rhetorically why I didn't select a name like Superdoopersaurus to follow the recently invented names Supersaurus and Ultrasaurus for two supergiant dinosaurs that were discovered in Colorado. That quip lightened up the discussion.


First display of the tail vertebrae at the New Mexico Museum of Natural History, Albuquerque. This vertebra is no. 20, counting from the base of the tail. It was the anterior-most of the original eight excavated in 1985.

We had prepared an exhibit case for the four vertebrae, set beneath the Camarasaurus skeleton for comparison with its tail vertebrae. Comparison with a skeleton of Diplodocus or Apatosaurus would have been more appropriate, since Seismosaurus belongs in the same family with these two familiar dinosaurs, but the Camarasaurus skeleton was the closest comparison we could make with the exhibits available. The corresponding vertebrae in the tail of the Camarasaurus skeleton are ridiculously small by comparison. The display emphasized the extraordinary size of the new dinosaur, even though we had only four bones to present to the public.

The press conference generated a surge of media attention, more than I ever imagined. Sam (rather, Seismosaurus) was spectacular.

My allusion to "earth-shaking" proved ironic, for the next year we would initiate experiments in remote sensing to look for more of Sam's bones hidden deeper in the mesa. Artificially generated sound waves (from a fancy shotgun) would help us "see" bones without digging. That technology was called seismic tomography.


A partially prepared Seismosaurus caudal vertebra. The sandstone in which this bone was encased was so perfectly matched in color and texture that distinguishing bone under ordinary lighting conditions (such as photographed here) was almost impossible.

To formalize the name Seismosaurus I needed to fully describe the eight tail vertebrae on which the determination had been made. This description had to be published in a technical journal. I had to distinguish the bones from all other dinosaurs, including Sam's closest relatives, Diplodocus, Apatosaurus, and Barosaurus. This might appear to be a dry and simple task, but technical descriptions of new species are difficult and demanding. Putting into words the description of a bone or skeleton is an extraordinary challenge of communication in the use of our wonderfully versatile language. To succinctly describe an object that is as irregular as a bone, and to do so in words that others can understand without ever seeing it, is immensely satisfying. I, of course, had a science illustrator draw the bones from various perspectives, but in a scientific journal the words are definitive.

Formal description would not be done overnight. What is more, I knew that if I waited I would almost surely have more bones upon which to base the genus-making description. Publication would therefore wait.

Seismosaurus was not, however, a complete name for formal publication. Living and extinct organisms are given binomial names. The principle of binomial nomenclature is that every organism is given a pair of names: a genus name that is capitalized and a species name that is not. Humans belong to the genus Homo. We share this genus with no living species but with several extinct hominid species--Homo erectus , for example. Our species is sapiens. We are therefore Homo sapiens --presumably, "wise" humans.

The informal name Seismosaurus established at the press conference could not be formalized without a species name to follow it. That left me with another decision: what to call Sam's species in the formal description.

Sometimes a species name is coined for an anatomical feature, or for a locality, or for a person, such as the discoverer or a patron of the project. Several times I half-jokingly offered to name the species after anyone willing to donate half a million dollars to the project, and the genus after anyone willing to donate a million dollars. My circle of friends is not wealthy; I got no takers.

I considered naming the species for Arthur Loy and Jan Cummings, who together found the bones. In fairness, however, I recognized not only Arthur and Jan as the discoverers but also their friends Frank Walker, who brought the bones to my attention and showed them to me, and Bill Norlander, the fourth member of this fraternity of hiking buddies. I couldn't name the species for all four, and naming it for one wouldn't be fair to the others.

What about geography? The correct latinization of ojito , for the site in the Ojito Wilderness Study Area, would be ojitoensis . The pronunciation would thus be a puzzle to everyone not familiar with Spanish etymology, and I dislike tongue-twister names anyway.

What about anatomy? Most of Sam's anatomical features are subtle and I couldn't find any one trait in particular that would by itself characterize the species. I thought about referring to the size of the new species by using longus  or colossus , but these names didn't seem appropriate either.

I settled on naming the species for the Reverend James Hall, director of the Ghost Ranch Conference Center, and his wife Ruth Hall, an amateur paleontologist who inspired several professional careers by her teaching. Ghost Ranch is in northern New Mexico, a study center owned by the Presbyterian Church in the canyonlands north of Santa Fe made famous by the artist Georgia O'Keeffe. On its 23,000 acres is one of the richest and most spectacular dinosaur sites in the world, a quarry where at least a thousand individuals of the little predatory dinosaur Coelophysis have been excavated. Jim and Ruth together supported paleontology in and around Ghost Ranch and northern New Mexico for a quarter century. I began working there in 1985 and continue with several active projects related to the Coelophysis quarry. Ghost Ranch has since established the Ruth Hall Museum of Paleontology, organized by Lynett Gillette, the museum's first curator.

Seismosaurus would thus bear the simple species name "halli." Seismosaurus halli , or "Hall's earth-shaker dinosaur," it would be.

I now had the name necessary for publication, and soon I had more bones. I submitted my description to the Journal of Vertebrate Paleontology  in 1989. The review process stretched on, however. Scientists are naturally skeptical of claims of new species (and, even more so, genera), and the peer reviewers of my paper took their task seriously. I had to respond to their criticisms; producing acceptable revisions added another year to the publication date. The descriptive paper was finally published in 1991. Prior to that time, I had given a talk at a scientific symposium (1986) and had published a short abstract (1987), referring to Sam as "a giant sauropod" or "a new giant sauropod" from the Morrison Formation of New Mexico. I had also written a popular article on the excavation for the Ghost Ranch Journal . But publication of a formal description and a full scientific name in the Journal of Vertebrate Paleontology  made it official.

To paleontologists the full and correct name for the new species is now "Seismosaurus hallorum  Gillette 1991." My initial name proved to have an incorrect Latin ending of a genitive singular--a mistake recognized by George Olshevsky, a dinosaur classification aficionado. So it was changed to the plural form. I formally assigned it to the family Diplodocidae, the family that includes the giants Diplodocus, Barosaurus, and Apatosaurus and the supergiant Supersaurus, all from the Morrison Formation of western North America.

From my original coining of Seismosaurus to technical publication of the name Seismosaurus halli  (more properly Seismosaurus hallorum ) took five long years. With the formal publication of the name and description of Sam's bones as the basis for the new species, our initial goals had been achieved: we had defined the species, identified its distinguishing characteristics, established the geologic age in which the animal lived (late Jurassic) and the geographic position of the site (the southern end of the Morrison Formation), and presented the data and interpretive calculations that would verify Sam's size--then calculated as between 128 feet and 170 feet, or between 39 and 52 meters--in the technical literature, through the rigors of peer review.

Sam's position in the scheme of classification of animals can be succinctly summarized. The fundamental unit of classification is the species. Taxonomic categories above the species level are increasingly subjective, generally arranged in hierarchical order. For Sam, the full classification using traditional ranks is as follows:

Some paleontologists prefer to separate dinosaurs from the reptiles into a distinct class: Dinosauria. Usually by that convention, Dinosauria includes only dinosaurs, but some paleontologists place birds in the same class, subsuming the traditional class Aves into Dinosauria. At issue are the questions of origins and the philosophy of establishing these evolutionary hierarchies. In recent years applications of the principles of cladistics, and with them a new system of nomenclature, have clarified many questions of ancestry, but the basic unit of classification, the binomial (genus and species) remains largely unaffected.

This naming, this classification, this identification and formal description of Sam depended ultimately on the bones. How does one find more bones hidden, and perhaps scattered, inside a mesa?

Seismosaurus