The arms of Therizinosaurus–as yet, the rest of the dinosaur is missing. Photo by FunkMonk, image from Wikipedia.

The most famous set of arms in the history of dinosaurs belong to Deinocheirus–eight foot long appendages from a huge ornithomimosaur that roamed Mongolia around 70 million years ago. But the immense ostrich-mimic wasn’t the only giant omnivore of its time, nor the only one made famous by its imposing arms. About 20 years before the discovery of Deinocheirus, a joint Soviet-Mongolian expedition found extremely long, tapering claws and a few other bones from a gigantic reptile. The identity of this animal took decades to untangle.

Paleontologist Evgeny Maleev described the paltry remains in a 1954 paper. Based on rib fragments, a bone from the hand, and three claws, Maleev believed that he was looking a gargantuan turtle. He named the creature Therizinosaurus cheloniformis–roughly, the “turtle-like scythe lizard.”

The animal’s claws played a key role in the identification. No terrestrial animal had such claws, he argued. Such armaments “may have been originally used by the animal for cutting aquatic vegetation or for another function, constrained by movement and acquiring food.” And even though Maleev only had pieces to work with, he proposed that Therizinosaurus was about 15 feet long with claws at least three feet long. This aquatic, apparently armor-less turtle lived in a time of hadrosaurs, tyrannosaurs, and sauropods.

Therizinosaurus wasn’t recognized as a dinosaur until 1970. In that year, paleontologist Anatoly Konstantinovich Rozhdestvensky published a re-evaluation of Maleev’s fossils that found the rib to be from a sauropod dinosaur, but the hand bone and the claws to be from some as-yet-unknown theropod. This recognition only spawned a new mystery–what sort of theropod dinosaur was Therizinosaurus, and what was the creature doing with such fearsome claws?

More complete forelimb and shoulder material described by Rinchen Barsbold in 1976 showed that Therizinosaurus had extraordinarily robust arms–quite a departure from the trend seen in large carnivorous dinosaurs, in which the arms seemed to become smaller as skulls became more heavily-built. At a time when theropod was generally considered to be synonymous with “carnivorous dinosaur”, it’s not surprising that experts speculated that Therizinosaurus was a monstrous predator who used claws, rather than teeth, to slice up the hadrosaurs and sauropods of its time. That’s the way I encountered the dinosaur in the books I read as a kid–a little-known, Cretaceous hadrosaur-shredder.

What researchers didn’t recognize was that Therizinosaurus represented an entirely new variety of theropod dinosaur. More complete skeletons of related forms such as Segnosaurus, Erlikosaurus, Alxasaurus, and Beipiaosaurus revealed the presence of a previously-unknown group of dinosaurs with long necks, beaked mouths, fat bodies, and stout arms tipped with ludicrously-long claws. These were omnivorous or herbivorous dinosaurs, not carnivores, although paleontologists didn’t immediately agree on what lineage they belonged to. Some thought they might be aberrant ornithischians–on the opposite side of the dinosaur family tree from theropods–or strange variations on the sauropod theme. By the mid-90s, however, paleontologists recognized that these truly were theropods, and ones belonging to the maniraptoran group that also encompasses the strange alvarezsaurs, beaked and crested oviraptorosaurs, the sickle-clawed deinonychosaurs, and birds. This group of tubby, feathery dinosaurs became known as the therizinosaurs.

Although Maleev didn’t recognize it when he named Therizinosaurus, he had found one of the most spectacular dinosaurs of all time–a giant, fluffy, omnivorous dinosaur that challenged what we thought we knew about theropods. Still, our image of Theriziniosaurus relies on the skeletons of more complete, closely-related dinosaurs. So far, we only really know what the arms of this dinosaur looked like, and the hindlimb elements described in the 1980s may or may not belong to another creature. We’re still waiting for the true nature of this undoubtedly bizarre dinosaur to come into focus.

References:

Barsbold, R. 1976. New data on Therizinosaurus (Therizinosauridae, Theropoda) [translated]. In Devâtkin, E.V. and N.M. Ânovskaâ (eds.), Paleontologiâ i biostratigrafiâ Mongolii. Trudy, Sovmestnaâ Sovetsko−Mongol’skaâ paleontologičeskaâ kspediciâ, 3: 76–92.

Maleev, E.A. 1954. “New turtle−like reptile in Mongolia [translated].” Priroda, 1954, 3: 106–108.

Zanno, L. 2010. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology. 8, 4: 503–543.

An illustration showing the only known bones from Genyodectes. Art in Woodward, 1901, image from Wikipedia.

Paleontologists are naming new dinosaurs at an astonishing rate. In fact, they’re only just begun to skim the diversity of dinosaurs preserved in the world’s Mesozoic formations–hundreds of unknown dinosaur species are undoubtedly hiding in stone. But even among dinosaurs that have a formalized identity, there are many that we know relatively little about. Among them is Genyodectes serus, a carnivorous dinosaur known from the tip of its fearsome jaws and little else.

Though it’s far from being a household name, Genyodectes holds a significant place in the history of South American paleontology. Aside from a tooth found a few years before, the incomplete fossil snout of a Genyodectes was the first definitive non-avian theropod dinosaur found on the continent. As described by paleontologist A.S. Woodward in 1901, the remains of Genyodectes mostly consisted of pieces from the lower jaw, as well as the premaxillary bones and fragments of the maxillary bones in the upper jaw, all of which sported frighteningly long, curved teeth.

There was never any question that Genyodectes was a theropod dinosaur. All the principally carnivorous dinosaurs that we know of fell among various branches of this group. But what sort of theropod dinosaur was it? During the 20th century, different paleontologists proposed that it was a megalosaurid (then a generalized term for big predatory dinosaurs), a tyrannosaur or, after additional theropod remains started to come out of South America, one of the stubby-armed abelisaurids.

After the specimen was given a fresh cleaning, paleontologist Oliver Rauhut reexamined Genyodectes with an eye towards what the dinosaur was and where it came from. Based on notes and geological details, Rauhut proposed that the dinosaur was found in Cañadón Grande in Argentina’s Chubut province in a Cretaceous deposit that probably dates to around 113 million years old. And, based on the limited remains, Rauhut hypothesized that Genyodectes was a later, southern cousin of North America’s Ceratosaurus. While the only known specimen of Genyodectes was cracked and damaged by erosion, the size and the anatomy of the dinosaur’s teeth most closely resembled that of Ceratosaurus–especially in having extremely long teeth in the maxilla. Given this relationship, we might expect that Genyodectes had some kind of skull ornamentation like the nasal and eye horns of its cousin, but we need more fossils to be sure.

Reference:

Rauhut, O. 2004. Provenance and anatomy of Genyodectes serues, a large-toothed ceratosaur (Dinosauria: Theropods) from Patagonia. Journal of Vertebrate Paleontology. 24, 4: 894-902

Thanks to a row of huge bony plates, Stegosaurus remains one of the strangest dinosaurs ever found. Photo by the author at the Utah Field House of Natural History in Vernal, Utah.

Undoubtedly familiar to any dinosaur fan, Stegosaurus remains one of the strangest dinosaurs ever discovered. Even among others of its kind, the iconic Jurassic herbivore looks like an oddball. Many other stegosaur species sported long rows of spikes and short plates, but the flashy Stegosaurus had an alternating row of huge bony plates along its back and a relatively modest set of four tail spikes. How could such a strange arrangement of adornments have evolved?

From the arms of tyrannosaurs to the necks of sauropods and the armor of stegosaurs, bizarre dinosaur structures have frequently made paleontologists wonder “What was that for?” There had to be a reason for the deviations in form, and, paleontologists believe, the immediately recognizable plates on the back of Stegosaurus must have had some function. There has been no shortage of hypotheses. Off-the-wall ideas about flying stegosaurs aside, researchers have proposed that the plates along the spine of Stegosaurus protected the dinosaur from attack, were the Jurassic equivalent of solar panels or acted as sexy billboards to attract the attention of potential mates.

Although Stegosaurus certainly had much to fear from the contemporary Morrison Formation predators Allosaurus, Torvosaurus and Ceratosaurus, the dinosaur’s defensive weapons were its tail spikes (called a “thagomizer” by some). If Stegosaurus was anything like its spikier cousin Kentrosaurus, it could swing its tail with deadly force, and a damaged Allosaurus bone suggests that the “roof lizard” did just that. But the keratin-covered plates of Stegosaurus probably didn’t provide the herbivore with much additional protection. The immobile structures jutted upwards, leaving the dinosaur’s flanks exposed to attack. To call the plates “armor” isn’t quite right.

When I was a kid, though, Stegosaurus plates were more often said to help the dinosaur regulate its body temperature. Presuming that Stegosaurus was an ecothermic animal–that is, had a body temperature determined by the surrounding environment–the plates could have helped the dinosaur heat up by turning broadside in the morning and shed heat by turning toward the sun during midday. Using models of plates in wind tunnel experiments, paleontologist James Farlow and colleagues reported in 1976 that the plates could very well have been used to dissipate heat. This doesn’t mean that the plates evolved for that function, though.

In 2010, Farlow and coauthors followed up on the work by comparing the plates of Stegosaurus to the bony armor along the backs of modern crocodylians. While stegosaur plates might have played some passive role in regulating body temperature, they concluded, there was no indication that Stegosaurus plates evolved for that reason, or even were principally used as thermoregulatory equipment. (Not to mention the fact that we now know that dinosaurs were not lizard-like reptiles whose internal physiology was primarily dictated by the temperature outside.) If Stegosaurus plates made any difference in managing body temperature, it was a happy little quirk that rode along with the principal function of the plates.

At present, it appears that the impressive bony fins on the back of Stegosaurus evolved as display structures. A 2005 study by Russell Main and  collaborators, which focused on the microstructure of stegosaur plates, couldn’t find any evidence that the structures were used to radiate heat. Indeed, if stegosaurs truly required such radiators, it’s surprising that Stegosaurus seems unique in its plate arrangement–if plates were really used to regulate body temperature, you’d expect to see the same arrangement in many closely related species. Instead, much like the horns of ceratopsid dinosaurs, the plates and spikes of stegosaurs varied greatly between species. This suggests that visual display was driving the evolution of these structures. Being recognized as a member of a particular species, or displaying an individual’s maturity and vigor during mating season, probably drove the divergence in form among stegosaur ornaments. The question is whether stegosaur plates made any difference in the mating season or they simply served to help species recognize members of their own kind. That debate–over the sexiness of plates, spikes, horns, crests, sails and domes–is just heating up.

References:

Farlow, J., Thompson, C., Rosner, D. 1976. Plates of the dinosaur Stegosaurus: Forced convection heat loss fins? Science. 192,4244: 1123-1125

Farlow, J., Hayashi, S., Tattersall, G. 2010. Internal vascularity of the dermal plates of Stegosaurus (Ornithischia, Thyreophora). Swiss Journal of Geosciences. 103, 2: 173-185

Hayashi, S., Carpenter, K., Watabe, M., McWhinney, L. 2011. Ontogenetic histology of Stegosaurus plates and spikes. Palaeontology. 55, 1: 145-161

Main, R., de Ricqlès, A., Horner, J., Padian, K. 2005. The evolution and function of thyreophoran dinosaur scutes: implications for plate function in stegosaurs. Paleobiology. 31, 2: 291-314

Padian, K., Horner, J. 2010. The evolution of “bizarre structures” in dinosaurs: biomechanics, sexual selection, social selection, or species recognition? Journal of Zoology. 283,1: 3-17

The upper and lower jaws of Duriavenator, illustrated when they were thought to belong to Megalosaurus, in A History of British Fossil Reptiles Vol. II. Image from Wikipedia.

If you have been following the Dinosaur Alphabet series so far, you may have noticed a pattern among the first four entries. At one time or another, all the dinosaurs I’ve selected so far were thought to be different animals. The horned Agujaceratops was originally named as a species of Chasmosaurus, the distinctive high-spines of Becklespinax gave Richard Owen’s dopey Megalosaurus its hump, the sauropod Cetiosaurus was originally envisioned as a giant crocodile, and the armored Dyoplosaurus was lumped in with its cousin Euoplocephalus before being split back out again as a distinct genus. I didn’t intend this trend, but it struck me when I came across  one of the rejected candidate for yesterday’s entry for the letter D. Had it not shared much of its story with Becklespinax, I would have picked Duriavenator:

Megalosaurus was a mess. Even though this Jurassic carnivore has been a prehistoric icon ever since it was named by William Buckland in 1824, it has been one of the most confounding of all dinosaurs. That’s because generations of researchers attributed dozens of fragments and isolated bones to the dinosaur, creating a monstrous composite of animals from different places and times. Dinosaurs were unfamiliar animals–the name itself only coined in 1842–and 19th-century naturalists didn’t have the kind of geologic resolution their intellectual descendants rely on to properly constrain when particular species lived. Sometimes researchers named too many species on the basis of scrappy, non-overlapping material, and other times they applied the same name ad infinitum to roughly similar fossils.

Eventually, though, it became apparent that Megalosaurus was unstable. No one could say what the dinosaur really looked like or what bones could accurately be attributed to the predator.  The situation was so bad that, in 2008, paleontologist Roger Benson and colleagues stripped the name Megalosaurus from everything save for the fragment of jaw originally used to name the animal. Whether the rest of the fossils really belonged to Megalosaurus remained to be seen, and, as Benson demonstrated later the same year, at least one other theropod had been improperly obscured behind the famous name.

In 1883, anatomist Richard Owen described a partial theropod skull found on Dorset, England, as another piece of Megalosaurus “bucklandi.” The sharp-toothed dinosaur was only represented by parts of the upper and lower jaws, but, given how little was known about Megalosaurus to start with, Owen’s assignment was reasonable. Nearly a century later, paleontologist Michael Waldman proposed that these fossils represented a previously unknown species of the dinosaur he called Megalosaurus hesperis. Other researchers weren’t sure that the bones really belonged to Megalosaurus, but it wasn’t until Benson’s reexamination that the fossils were split out as a different dinosaur. While the dinosaur was a close cousin of Megalosaurus bucklandii, Benson was able to pick out subtle anatomical characteristics that distinguished the fragmentary skull. In Benson’s analysis, what once was Megalosaurus took on a new life as Duriavenator hesperis.

Benson’s reconstruction of Megalosaurus, with known elements in white and reconstructed portions in grey. While Duriavenator was older and anatomically distinct, the dinosaur would have been similar in form to Megalosaurus. From Benson, 2010.

Unfortunately, we don’t know very much at all about Duriavenator. The dinosaur lived about 170 million years ago in Jurassic England and was a large carnivore of comparable size to the 20-foot-plus Megalosaurus, but that’s where the evidence gives out. Perhaps other Duriavenator specimens are resting in museum collections, but until the discovery of a nearly complete skeleton allows paleontologists to connect the jaws to a body, the dinosaur will be an enigma. But here Megalosaurus itself gives us reason to hope. The Duriavenator paper was just part of Benson’s effort to rehabilitate Megalosaurus, and in 2010 he published a refined, revised reconstruction of the dinosaur’s skeleton based on material collected from Stonesfield, Oxfordshire–the locality where the original jaw came from. Perhaps, with a little detective work in the lab and in the field, paleontologists might also be able to fill out the form of Duriavenator and other Middle Jurassic mysteries.

References:

Benson, R., Barrett, P., Powell, H., Norman, D. 2008.  The taxonomic status of Megalosaurus bucklandii (Dinosauria, Theropoda) from the Middle Jurassic of Oxfordshire, UK. Palaeontology, 51, 2: 419-424.

Benson, R. 2008.  A redescription of “Megalosaurus” hesperis (Dinosauria, Theropoda) from the Inferior Oolite (Bajocian, Middle Jurassic) of Dorset, United Kingdom. Zootaxa 1931: 57-67

Benson, R. 2010. A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods. Zoological Journal of the Linnean Society 158: 882. doi:10.1111/j.1096-3642.2009.00569.x.

Waldman, M. 1974. Megalosaurids from the Bajocian (Middle Jurassic) of Dorset. Palaeontology 17, 2:325-339.

Fossil teeth, found by Ferdinand Hayden in Montana, which Joseph Leidy attributed to the dinosaur “Trachodon.” From Leidy, 1860, image from Wikipedia.

More than 150 years ago, a young naturalist picked up a collection of isolated teeth and bones weathering out of the ground in what is now northern Montana. These weren’t the remains of any living animals but vestiges of Cretaceous life that naturalists had only just begun to recognize and categorize. Even the young explorer who picked them up, Ferdinand Hayden, didn’t know what they were, and so he sent them back east for identification. As the Philadelphia-based polymath Joseph Leidy later determined, some of Hayden’s scrappy finds were dinosaurs–among the earliest recorded dinosaur discoveries in the American West.

Hayden wasn’t the first person to discover fossils in North America. First Nations peoples were familiar enough with strange fossil bones that the prehistoric remnants inspired their legends, and naturalists such as Thomas Jefferson puzzled over what was left of Ice Age mammals such as mastodons and giant ground sloths. Dinosaurs got a relatively early start, too, although naturalists didn’t always realize what they had found. Even though he misidentified the fossil as part of a giant fish, explorer Meriwether Lewis found part of a dinosaur rib in the vicinity of what is now Billings, Montana, when he passed through the area in 1806 on his famous expedition with William Clark. And starting in the 1830s, the Amherst geologist Edward Hitchcok described scores of Early Jurassic dinosaur tracks, which he attributed to prehistoric birds.

All the same, the bits and pieces Hayden found showed that the wilds of the western territories harbored dinosaurs and were a portent of the “Bone Wars” that would later unfold among the badlands of Montana, Wyoming and Colorado. Now, the Great Falls Tribune reports, paleontologist Kristi Curry Rogers and her geologist husband Ray Rogers believe that they have located the place where Hayden stumbled across the Cretaceous tidbits.

Even though Hayden did not keep detailed field notes, a brief mention in a technical paper of the area in which he found the fossils helped the Rogers team narrow down their search area. From there, they followed game trails and looked for sites that would have produced the kinds of fossils Hayden picked up. They can’t be entirely certain that their site is the very same Hayden sampled, and they are wary of divulging the exact location given how often fossil sites are vandalized, but the Rogers have placed Hayden’s stop somewhere in Montana’s Missouri River Breaks north of Winifred. With assistance from the Bureau of Land Management, they want the area to be placed in the National Register of Historic Places–a testament to Hayden’s lasting contribution to American paleontology.

A mount of Cetiosaurus at the New Walk Museum in Leicester. While the neck of this sauropod is almost completely known, no skull has ever been described. Photo by Flickr user Paul Stainthorp.

Sauropods were magnificent dinosaurs. These long-necked, small-headed titans were unlike anything that has evolved before or since, and they were so strange that paleontologists are still debating the basics of how Apatosaurus and kin actually lived. As iconic as their skeletons are now, though, the first sauropod ever described was initially envisioned as a very different sort of creature. The great Cetiosaurus was originally seen as a gargantuan, plesiosaur-crunching crocodile.

In 1841, the British anatomist Richard Owen described a curious collection of limb bones and vertebrae found at various locations in England. The limb elements reminded Owen of the same bones in crocodiles, and the vertebrae were reminiscent of those in whales. The scattered elements seemed to correspond in structure to aquatic animals, and since function was dictated by skeletal form, Owen believed that Cetiosaurus–the “whale lizard”–must have been a marine predator larger than anything that had been found before.

The following year, in his massive Report on British fossil reptiles, Part II, Owen reassessed the various prehistoric reptiles from his country. This was the landmark monograph in which Owen coined the term “Dinosauria,” but he didn’t include Cetiosaurus within the newly named group. The animal seemed vastly different from Megalosaurus, Iguanodon and Hylaeosaurus. Dinosaurs, in Owen’s view, were terrestrial animals with upright limbs, and he saw Cetiosaurus as a marine carnivore. Owen grouped the poorly known animals with crocodiles, instead.

It wasn’t until 1869 that Cetiosaurus was formally recognized as a dinosaur. Thomas Henry Huxley, Owen’s chief academic rival, proposed that Cetiosaurus was a close relative of Iguanodon, although he later changed his mind and suggested that the puzzling animal was an oddball that didn’t belong with crocodiles or dinosaurs. Other researchers were more confident that Cetiosaurus belonged among the dinosaurs. John Phillips, in an 1871 monograph, proposed that Cetiosaurus was an herbivorous dinosaur, and in 1875 Owen conceded that his creature was a huge, aquatic dinosaur.

Like many other early dinosaur finds, the identity of Cetiosaurus was obscured by a lack of material and the unfamiliarity of the Mesozoic curiosities. When O.C. Marsh, E.D. Cope and other North American paleontologists began to uncover relatively complete skeletons of dinosaurs such as Diplodocus and “Brontosaurus” from the American West during the late 19th century, a more accurate vision of Cetiosaurus as a sauropod started to come into focus. All the same, researchers named multiple species of this dinosaur from various sites of different ages. Cetiosaurus became a taxonomic wastebasket for numerous scrappy sauropods found in England.

Paleontologists Paul Upchurch and John Martin sorted out the mess in 2003. Out of 13 different species named from bones belonging to different kinds of sauropods that lived millions of years apart, Upchurch and Martin recognized only one valid taxon–Cetiosaurus oxoniensis. This sauropod trod Jurassic England around 170 million years ago. And even though our knowledge of this dinosaur’s skeleton isn’t yet complete, discoveries both old and new have helped paleontologists outline what this historically significant dinosaur was like.

In 1868, quarry workers at Bletchingdon Station (near Oxford, England) uncovered a Cetiosaurus bonebed containing a trio of skeletons, one being much larger than the others. These bones formed the basis of Phillips’ study of the dinosaur, and, as Upchurch and Martin noted, “potentially represents one of the best preserved sauropods from the Jurassic of Europe.” A century later, in 1968, workers at Williamson Cliffe Brickworks in Rutland discovered bones in their quarry, and some of the remains were briefly described by M.D. Jones in 1970. Upchurch and Martin reexamined the Rutland material as part of their bigger Cetiosaurus project and found that the individual dinosaur is represented by an almost complete neck, various parts of the spinal column and limb elements, making it one of the best-preserved Cetiosaurus ever found.

Altogether, the bones of Cetiosaurus indicate that the sauropod was medium to large in size, though exactly how big this dinosaur was isn’t clear. (Estimating the length and mass of incompletely-known dinosaurs is a difficult task.) What makes Cetiosaurus of special interest to paleontologists, though, is that it was a relatively archaic form of sauropod. Most of the famous sauropods–Diplodocus, Camarasaurus, Brachiosaurus and their ilk–belong to lineages within a big group called the neosauropoda. Cetiosaurus seems to fall just outside this group, and so the dinosaur might clue paleontologists in to what sauropods were like just before the fantastic radiation of neosauropods during the Late Jurassic. It took three decades to change the animal from a crocodile to a dinosaur, and a century more for the sauropod’s identity to be untangled, but, now that the dinosaur has a definite name and evolutionary identity, paleontologists can start to investigate the biological secrets locked inside Cetiosaurus bones.

Check out previous entries in the Dinosaur Alphabet here.

References:

Naish, D. 2009. The Great Dinosaur Discoveries. Berkeley: University of California Press. pp. 30-31

Upchurch, P., Martin, J. 2003. The Anatomy and Taxonomy of Cetiosaurus (Saurischia, Sauropoda) from the Middle Jurassic of England. Journal of Vertebrate Palaeontology 23 (1): 208–231

Upchurch, P., Martin, J. 2002. The Rutland Cetiosaurus: the anatomy and relationships of a Middle Jurassic British sauropod dinosaur. Palaeontology, 45: 1049–1074.

Wilson, J. 2005. Overview of sauropod phylogeny and evolution, pp. 15-49  in Curry Rogers and Wilson (eds.), The Sauropods: Evolution and Paleobiology, Berkley: University of California Press.

The peculiar, high-spined specimen that represents Becklespinax (left), and two possible restorations of the dinosaur by Darren Naish (right). From Naish and Martill, 2007.

Poor, neglected Becklespinax. Although this gaudy, sail-backed theropod was an impressive predator at the time it strode across England around 140 million years ago, the fragmentary remains of this dinosaur have a tangled history only recently highlighted by the discovery of a more completely-known relative. In the history of paleontology, Becklespinax the tale is a tragedy.

The bones of Becklespinax were among the earliest spate of dinosaur discoveries in England, before anyone really understand just how many dinosaurs there were and how widely they varied in form. No surprise, then, that when the British anatomist Richard Owen illustrated a strange set of three high-spined vertebrae in 1855, he assigned them to the carnivorous dinosaur Megalosaurus. After all, Megalosaurus was already a hodgepodge of theropod remains from different eras, so it’s no altogether surprising that Owen considered the strange vertebrae as part of the same animal. He was confident enough in his assessment that when Owen schooled the artist Benjamin Waterhouse Hawkins in dinosaur anatomy for the famous Crystal Palace reconstructions, the anatomist instructed the sculptor to give Megalosaurus a hump between the shoulders on account of the elongated neural spines in the one specimen.

Along with teeth and other bits, the strange sting of vertebrae were thrown together into the species Megalosaurus dunkeri by researchers such as Richard Lydekker. No one found any complete skeleton–just scattered pieces. Then, in 1926, paleontologist Friedrich von Huene proposed that the spines and teeth of this “Megalosaurus” were so different from others of its type that it deserved its own genus–”Altispinax.” So scientists kicked the name Altispinax around for awhile, but this was another hodgepodge dinosaur consisting of various specimens from different places and time periods. In 1991, dinosaur fan George Olshevsky suggested that the set of three vertebrae carry the name Becklespinax altispinax, and, so far, that name has stuck.

But just what sort of dinosaur was Becklespinax? Paleontologist and prolific blogger Darren Naish addressed this question a few years back. The dinosaur was clearly a relatively large theropod, probably over 20 feet long. But, during the late 19th and early 20th centuries, there was no other dinosaur quite like it. Without a more complete skeleton, it was impossible to tell. And even after other big theropods with elongated spines on their backs were discovered–such as the croc-snouted Spinosaurus from the Late Cretaceous of Africa and the deep-skulled Acrocanthosaurus from the Early Cretaceous of North America–the anatomy of Becklespinax didn’t match those forms.

Even worse, the extremely limited material confounded paleontologists who attempted to figure out what the back of Becklespinax looked like. Were those elongated spines a sign of a high sail that ran most of the length of the dinosaur’s back, as in Spinosaurus? Or did it indicate a short, high ornament near the hips? Naish illustrated both possibilities in a 2007 paper he wrote with colleague David Martill. The first vertebral spine contained yet another puzzle. This bone was shorter than the following two. This might have been a pathology, or even because the bones came from the front part of the sail as it was building to its full height. No one knew for sure.

Then along came Concavenator. In 2010, paleontologist Francisco Ortega and colleagues named this carnivorous dinosaur on the basis of a gorgeous, 130-million-year-old skeleton found in Spain. A cousin of the high-spined Acrocanthosaurus from North America, Concavenator also had a weird backbone–the carcharodontosaur had a high, shark-fin-shaped sail just in front of the hips.

In over a century and a half, no one has ever found a better or more complete specimen of the English dinosaur, yet Concavenator offered a glimmer of what Becklespinax might have looked like. Both were sail-backed theropods that lived in the Early Cretaceous of Europe. And while our knowledge of Becklespinax is frustratingly incomplete, the resemblance of the dinosaur’s known remains to the corresponding parts in Concavenator suggest that Becklespinax, too, was a sail-backed carcharodontosaur. Their relationship may even go deeper. While the two dinosaurs lived about 10 million years apart, Naish pointed out, it’s possible that both dinosaur species belong to the same genus. Concavenator corcovatus might, in fact, be rightly called Becklespinax corcovatus. Without a fuller view of what the skeleton of Becklespinax looked like, though, it’s impossible to tell.

Whatever Becklespinax is, paleontologists have almost certainly found other scraps from this dinosaur. The trick is correctly identifying and assembling the scattered pieces. It takes years to untangle the history and form of dinosaurs found during the 19th century, as paleontologist Roger Benson did with Megalosaurus. A skeleton–even a partial one–would be even better. Such a discovery would go a long way towards outlining the nature of the frustratingly-incomplete Becklespinax, although other questions would certainly remain.

Between Acrocanthosaurus, Becklespinax and Concavenator, the massive carcharodontosaurs of the Early Cretaceous were apparently well-decorated predators that bore distinctive ridges and sails on their backs. Why? What good would such ornaments be to large predators? Were they signals of dominance, advertisements of sexual desirability or even just easily-seen markers that an individual belonged to this species and not that one? No one knows. As debates about sexual selection and dinosaur ornamentation heat up, even rapacious carnivores will have a role to play.

Previous posts in this series:

A is for Agujaceratops

Reference:

Naish, D., and Martill, D. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, 164 (3), 493-510 DOI: 10.1144/0016-76492006-032

Ortega, F., Escaso, F., and Sanz, J. 2010. A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain Nature, 467 (7312), 203-206 DOI: 10.1038/nature09181

Stovall, J., & Langston, W. 1950. Acrocanthosaurus atokensis, a new genus and species of Lower Cretaceous Theropoda from Oklahoma. American Midland Naturalist, 43 (3): 696–728. doi:10.2307/2421859

Pennycuick’s hypothetical Archaeopteryx ancestor, with membranes between the fingers and no feathers. From Pennycuick, 1986.

How dinosaurs took to the air is one of the longest-running debates in paleontology. Ever since the first skeleton of Archaeopteryx was discovered in 1861, researchers have wondered what the archaic bird might tell us about how flight evolved and how the feathery creature connected its reptilian ancestors with modern birds. Even now, when we know that birds are a feathered dinosaur lineage, the origins of flight remain a contentious issue constrained by the available fossil evidence and our ability to reconstruct how prehistoric creatures moved.

Before paleontologists confirmed that birds are dinosaurs, though, various researchers came up with speculative schemes to explain how birds originated. Naturalist William Beebe, for one, proposed that bird ancestors started off as parachuting reptiles that benefited from expanded scales (his conception of protofeathers). Other scientists came up with their own ideas, imagining everything from seagoing protobirds to gliding reptiles.

When ornithologist Colin Pennycuick wrote his paper “Mechanical Constraints on the Evolution of Flight” in 1986, however, paleontologists were warming to the idea that Archaeopteryx spanned the evolutionary space between living birds and dinosaurs like Deinonychus. This narrowed down the list of early flight scenarios to hotly debated “ground up” or “trees down” hypotheses for the origin of flight, and raised the possibility that feathers evolved among non-avian dinosaurs first. Within these debates, Pennycuick put forward his own idiosyncratic proposal.

Pennycuick believed that birds took to the air by way of the trees. Bird ancestors progressively shrunk in size over time, he believed, and started gliding before they could actually fly. He couldn’t envision that birds evolved from a running, leaping ancestor, as other researchers suggested. For Pennycuick, flight was a gradual extension of gliding.

But what did the ancestor of Archaeopteryx look like? Pennycuick assumed that feathers and flight were closely tied together–something that is not true at all and had already been pointed out by paleontologist John Ostrom in his work on bird origins. Feathers are important for display and insulation and were only later co-opted for flight. All the same, Pennycuick needed a gliding–but featherless–ancestor for Archaeopteryx to make his idea work. So he conjured something really weird.

Pennycuick was puzzled by the clawed fingers of Archaeopteryx. Why would a bird have differentiated fingers? Rather than look at the fingers as just a holdover from dinosaurian ancestry, Pennycuick assumed that they had some kind of flight function. The fingers of Archaeopteryx, he proposed, “could have supported a small, batlike hand-wing.” Such a structure would have been inherited from the featherless ancestor of Archaeopteryx, he proposed, “constituting the main wing area in the stage before feathers were developed.”

Where the feathers of Archaeopteryx came from, Pennycuick couldn’t say. He mused on the need for feathers in the transition from gliding to flight, but he didn’t offer an explanation for how feathers evolved. He only mentioned that “The development of down feathers as thermal insulation is a separate process that may or may not have preceded the development of flight feathers.”

The fuzzy dinosaur Sinosauropteryx proved Pennycuick wrong a decade later. Paleontologists like Ostrom and artists such as Gregory S. Paul had long suspected that feathers were a widespread trait among bird-like theropod dinosaurs, and a flood of exceptional fossils has shown that feathers and their precursors have a deep, deep history. Dinofuzz, or structurally similar body coverings, might even go back to the root of the Dinosauria. How evolutionary forces molded those adornments, however, and what drove the evolution of flight feathers, remain as aggravatingly contentious as ever.

[Hat-tip to paleontologist Victoria Arbour for bringing this paper to my attention]

Reference:

Pennycuick, C. 1986. Mechanical Constraints on the Evolution of Flight. Memoirs of the California Academy of Sciences. 8, 83-98

Few things in paleontology generate as much speculation, and ridicule, as the arms of Tyrannosaurus rex. In a culture where “bigger” is confused with “better,” we can’t seem to get our heads around why such a large predator would have such small forelimbs. Most puzzling of all is that the dinosaur’s arms were not vestigial–they were muscular appendages that must have had some function. But what?

Our understanding of tyrannosaur arms is constrained by what we think that dinosaurs were capable of. The trick is parsing the difference between what T. rex could do and what it actually did. Even though it appears that the forelimbs of the tyrant dinosaurs became smaller as they developed heavier heads capable of crushing bites, this doesn’t necessarily tell us what T. rex and kin used their arms for, if anything.

When I was a kid, though, there was one possibility that popped up in the dinosauriana I loved to browse. As seen in the clip above, from the documentary Dinosaur!, some paleontologists thought that tyrannosaurs could have used their arms to raise themselves off the ground after resting or–as in this case–embarrassingly being knocked to the ground by an Edmontosaurus. For a creature with such tiny arms, researchers speculated, T. rex might have been surprisingly skilled at push-ups.

The idea goes back to Barney Newman, a paleontologist who worked at what is now London’s Natural History Museum. In 1970, after overseeing a reconstruction of T. rex at the museum, Newman wrote a short paper on the posture of the famous dinosaur. Not only did the tyrant have a more bird-like posture than previously thought, Newman wrote, but he finally found a use for those short arms. The heavy construction of the dinosaur’s arms and shoulder girdle showed that the chest and arms of T. rex were surprisingly beefy, and, in Newman’s view, all that muscle and bone acted as a set of brakes.

At rest, Newman suspected, T. rex sat in a kind of crouch with its legs “folded under the body in much the same way as a hen’s,” lower jaw on the ground and palms flat. When the dinosaur stood up, Newman suggested, “The role of the fore-limbs was that of a brake holding the body, so that the force exerted by the extension of the hind-limbs was transmitted to the pelvic region, thus pushing it upwards.”

Newman didn’t say that T. rex pushed the fore-part of its body off the ground. Artists and filmmakers confused what Newman had hypothesized–that the seemingly overbuilt arms of the dinosaur acted as stabilizers as T. rex extended its legs to stand. But, the T. rex stretch meme aside, there’s no reason to think that the theropod actually behaved as Newman supposed.

In Newman’s reconstruction, the wrists of T. rex make the dinosaur’s hands face palms-down. That would have given the tyrant some grip as it stood. But we know that theropod wrists didn’t articulate this way. As paleontologists frequently point out, theropods were clappers, not slappers–their palms faced inwards, towards each other, and flexed more like bird wrists. A wonderful sitting trace of an Early Jurassic theropod confirms this position, as do other smaller theropod skeletons preserved in the act of nesting or resting. In order to achieve a palms-down grip on the ground, T. rex would have had to swing its arms far out to the sides so that the dinosaur’s hands came into the right position.

Dinosaur traces and roosting skeletons also tell us something else. Newman was right that T. rex, like other theropods, probably sat in a very bird-like position. But, like both avian and other non-avian theropods, there’s no indication that tyrannosaurs needed extra stabilization to stand up. The thick heads and heavy tails of tyrannosaurs were counterbalanced over their hips, and they probably sat down and stood up in the typical theropod manner without the need for brakes. Newman’s hypothesis was a clever one for a long-running paleo problem, but what T. rex used those small, strong arms for remains as contentious as ever.

Reference:

Newman, B. 1970. Stance and gait in the flesh-eating dinosaur Tyrannosaurus. Biological Journal of the Linnean Society, 2. 119-123

Thomas the T. rex, a lovely reconstruction at the Natural History Museum of Los Angeles. Photo by the author.

Recently I was leading friend and fellow-writer Seth Mnookin through the Natural History Museum of Utah’s prehistoric exhibits when he asked a question that has popped up in my own mind from time to time–why is Tyrannosaurus rex so popular? There were stranger carnivores, and journalists love to delight in the announcements that slightly bigger theropods have dethroned the tyrant king. Yet T. rex remains the quintessential dinosaur.

Part of the secret, I think, is cultural inertia. Paleontologist Henry Fairfield Osborn named Tyrannosaurus rex in 1906, during a time when paleontologists were still dealing with a bare bones outline of what dinosaurs were like. Very few species were known from partial skeletons, much less complete ones, but Osborn’s field man Barnum Brown discovered two exquisite T. rex skeletons in rapid succession. The massive carnivore burst onto the scene as the largest carnivorous dinosaur ever found, and the second, more complete skeleton Brown discovered was quickly turned into an iconic mount that inspired many generations of paleontologists.

T. rex remained unchallenged until the mid-1990s. After nearly a century at the top, it was impossible to knock down the heavyweight. No museum display was complete with at least a T. rex tooth, if not a cast of a skeleton, and films such as King Kong and Jurassic Park underscored the savage power of the dinosaur. From the time of its discovery, we have celebrated T. rex as the acme of destructive dinosaurian power. The dinosaur so dominated the cultural landscape that it overshadows all others.

But, as Seth pointed out while I laid out this hypothesis, the dinosaur’s reputation is fully deserved. Some giant carnivores might have been a little longer or heavier–we don’t really know, since they’re not known as completely as T. rex–but there is no question that T. rex was among the top four gargantuan dinosaur predators and the biggest meat-eater in its Late Cretaceous ecosystem. Even though our general image of the tyrant has changed, from changes in posture to the addition of fuzz, T. rex has remained the biggest and baddest dinosaur from America’s badlands. The reputation of T. rex has not been diminished. To the contrary, the more we learn about the paleobiology of the theropod, the more fearsome T. rex becomes. And to that, I say “Long live the king!”

Fossil swim tracks indicate that theropods similar to this Megapnosaurus at least occasionally swam in prehistoric lakes and rivers. Art by Dmitry Bogdanov, image from Wikipedia.

Paleontologist R.T. Bird inspected many dinosaur trackways while combing Texas for the perfect set to bring back to the American Museum of Natural History. During several field seasons in the late 1930s, Bird poked around in the Early Cretaceous rock in the vicinity of the Paluxy River for a set of sauropod footprints that would fit nicely behind the museum’s famous “Brontosaurus” mount. Bird eventually got what he was after but not before poring over other intriguing dinosaur traces. One of the most spectacular seemed to be made by a swimming dinosaur.

Known as the Mayan Ranch Trackway, the roughly 113-million-year-old slab is almost entirely made up of front foot impressions. The semicircular imprints were undoubtedly left by one of the long-necked sauropod dinosaurs. But towards the end of the trail, where the dinosaur’s path makes an abrupt turn, there was a single, partial impression of a hind foot.

At the time Bird and his crew uncovered this trackway, sauropods were thought to be amphibious dinosaurs. Other than their immense bulk, what defense would they have had but to trundle into the water, where theropods feared to paddle? Under this framework, Bird thought he knew exactly how the Mayan Ranch Trackway was made. “The big fellow had been peacefully dog-paddling along, with his great body afloat, kicking himself forward by walking on the bottom here in the shallows with his front feet,” Bird wrote in his memoir. The great dinosaur then kicked off with one of its hind feet and turned.

With the exception of well-defended dinosaurs such as the ceratopsids and stegosaurs, many herbivorous dinosaurs were thought to be at least semi-aquatic. There seemed to be only two options for Mesozoic prey species–grow defenses or dive into the water. In time, though, paleontologists realized that the sauropods, hadrosaurs and other herbivores didn’t show any adaptations to swimming. Our understanding of the ecology of these dinosaurs was based on false premises and faulty evidence.

In the case of the Mayan Ranch Trackway, for example, there’s no indication that the sauropod that made the trackway was swimming. A more likely scenario has to do with evolutionary changes among sauropods. While the sauropods that dominated the Late Jurassic of North America–such as Diplodocus, Apatosaurus and Barosaurus–carried much of their weight at the hips and left deeper hindfoot impressions, the center of mass shifted among their successors–the titanosaurs–such that more of the weight was carried by the forelimbs. Hence, in some trackways, the deeper impressions made by the forefeet are more likely to stand out than those made by the hindfeet, especially if some of the top layers of the rock are eroded away to leave only “undertracks.” What seemed to be evidence of swimming sauropods instead owes to anatomy and the characteristics of the mucky substrate the dinosaur was walking on.

As far as I’m aware, no one has yet found definitive evidence of swimming sauropods or hadrosaurs–the two groups previously thought to rely on water for safety. Stranger still, paleontologists have recently uncovered good evidence that theropod dinosaurs weren’t as bothered by water as traditionally believed. In 2006, paleontologists Andrew Milner, Martin Lockley and Jim Kirkland described swim tracks made by Early Jurassic theropods at a site that now resides in St. George, Utah. Such traces weren’t the first of their kind ever discovered, but the tracksite was one of the richest ever found.

Small to medium-sized theropods made the St. George swim tracks–think of dinosaurs similar to Megapnosaurus and Dilophosaurus. Even better, the large number of smaller-size swim tracks hints that whatever dinosaurs made these tracks were moving as a group as they struggled against the current in the lake shallows. The larger dinosaurs, on the other hand, were a bit taller and able to wade where their smaller cousins splashed around.

A different team of researchers announced additional evidence for swimming theropods the following year. Paleontologist Rubén Ezquerra and co-authors described dinosaur swim traces from Early Cretaceous rock near La Rioja, Spain. Based on the details of the track and their direction, the theropod was swimming against a current that pushed the dinosaur diagonally. Along with other theropod swim tracks, the researchers noted, the discovery meant that paleontologists would have to revise their ideas about the kind of habitats theropods lived in and what carnivorous species would do. Theropod dinosaurs were not so hydrophobic, after all.

Does this mean that dinosaurs like Dilophosaurus were adapted to an amphibious lifestyle? Not at all. As Ezquerra and co-authors pointed out, the swimming strokes of these dinosaurs were exaggerated walking motions. The way the dinosaurs moved on land allowed them to be adequate swimmers while crossing rivers or lakes, but, compared with semi-aquatic animals such as crocodiles and otters, no known dinosaur shows traits indicative of a primarily waterlogged existence. (And dinosaurs found in marine sediments don’t count as evidence, as these were washed out to sea prior to burial. I can’t imagine ankylosaurs taking to life among the high seas, in any case.) Some dinosaurs could swim, but that doesn’t mean that they made the water their home. Still, thanks to special prehistoric traces, we can imagine packs of Megapnosaurus fighting to get ashore, and Dilophosaurus strutting into the shallows, aiming to snatch whatever fish were foolish enough to swim into the carnivore’s shadow.

References:

Bird, R.T. (1985). Bones for Barnum Brown, edited by Schreiber, V. Forth Worth: Texas Christian University Press. pp. 160-161

Ezquerra, R., Doublet, S., Costeur, L., Galton, P., Pérez-Lorente, F. (2007). Were non-avian theropod dinosaurs able to swim? Supportive evidence from an Early Cretaceous trackway, Cameros Basin (La Rioja, Spain) Geology, 40 (10), 507-510 DOI: 10.1130/G23452A.1

Milner, A., Lockley, M., Kirkland, J. (2006). A large collection of well-preserved theropod dinosaur swim tracks from the Lower Jurassic Moenave Formation, St. George, Utah. New Mexico Museum of Natural History and Science Bulletin, 37, 315-328

A reconstruction of an adult and juvenile Thecodontosaurus. From Benton, 2012.

When British anatomist Richard Owen coined the term “Dinosauria” in 1842, there were nowhere near as many dinosaurs known as there are today. And even among that paltry lot, most specimens were isolated scraps that required a great deal of interpretation and debate to get right. The most famous of these enigmatic creatures were Megalosaurus, Iguanodon and Hylaeosaurus–a trio of prehistoric monsters that cemented the Dinosauria as a distinct group. But they weren’t the only dinosaurs that paleontologists had found.

Almost 20 years before he established the Dinosauria, Owen named what he thought was an ancient crocodile on the basis of a tooth. He called the animal Suchosaurus, and only recently did paleontologists realize that the dental fossil actually belonged to a spinosaur, one of the heavy-clawed, long-snouted fish-eaters such as Baryonyx. Likewise, other naturalists and explorers discovered remnants of dinosaurs in North America and Europe prior to 1842, but no one knew what most of these fragments and fossil tidbits actually represented. Among these discoveries was the sauropodomorph Thecodontosaurus–a dinosaur forever connected with Bristol, England.

Paleontologist Mike Benton of the University of Bristol has traced the early history of Thecodontosaurus in a new paper published in the Proceedings of the Geologists’ Association. The story of the dinosaur’s discovery began in 1834, when reports of remains from “saurian animals” started to filter out of Bristol’s limestone quarries. Quarry workers took some of the bones to the local Bristol Institution for the Advancement of Science, Literature and Arts so that the local curator, Samuel Stutchbury, could see them. Yet Stutchbury was away at the time, so the bones were also shown to his paleontologist colleague Henry Riley, and when he returned Stutchbury was excited enough by the finds to ask quarrymen to bring him more specimens. He wasn’t the only one, though. David Williams–a country parson and geologist–had a similar idea, so Stutchbury teamed up with paleontologist Henry Riley in an academic race to describe the unknown creature.

All three naturalists issued reports and were aware of each other’s work. They collected isolated bones and skeletal fragments, studied them and communicated their preliminary thoughts to their colleagues at meeting and in print. In an 1835 paper, Williams even went so far as to suppose that the enigmatic, unnamed animal “may have formed a link between the crocodiles and the lizards proper”–not an evolutionary statement, but a proposal that the reptile slotted neatly into a static, neatly-graded hierarchy of Nature.

Riley, Stutchbury and Williams had become aware of the fossils around the same time in 1834. Yet Stuchbury and Williams, especially, were distrustful of each other. Stutchbury felt that Williams was poaching his fossils, and Williams thought Stutchbury was being selfish in trying to hoard all the fossils in the Bristol Institution. All the while, both parties worked on their own monographs about the animal.

Ultimately, Riley and Stuchbury came out on top. Williams lacked enough material to match the collection Riley and Stutchbury were working from, and he didn’t push to turn his 1835 report into a true description. He bowed out–and rightly felt snubbed by the other experts who had higher social standing–leaving the prehistoric animal to Riley and Stutchbury. No one knows why it took so long, but Riley and Stutchbury gave a talk about their findings in 1836, completed their paper in 1838 and finally published it in 1840. All the same, the abstract for their 1836 talk named the animal Thecodontosaurus and provided a short description–enough to establish the creature’s name in the annals of science.

But Thecodontosaurus was not immediately recognized as a dinosaur. The concept of a “dinosaur” was still six years away, and, even then, Richard Owen did not include Thecodontosaurus among his newly-established Dinosauria. Instead, Thecodontosaurus was thought to be a bizarre, enigmatic reptile that combined traits seen in both lizards and crocodiles, just as Williams had said. It wasn’t until 1870 that Thomas Henry Huxley recognized that Thecodontosaurus was a dinosaur–now known to be one of the archaic, Triassic cousins of the later sauropod dinosaurs. Thecodontosaurus only held the faintest glimmerings of what was to come, though. This sauropodomorph had a relatively short neck and still ran about on two legs.

The tale of Thecodontosaurus was not only a story of science. It’s also a lesson about the way class and politics influenced discussion and debate about prehistoric life. Social standing and institutional resources gave some experts an edge over their equally enthusiastic peers. Paleontologists still grapple with these issues. Who can describe certain fossils, who has permission to work on a particular patch of rock and the contributions avocational paleontologists can make to the field are all areas of tension that were felt just as acutely in the early 19th century. Dinosaur politics remain entrenched.

For more information, visit Benton’s exhaustively-detailed “Naming the Bristol Dinosaur, Thecodontosaurus” website.

Reference:

Benton, M. (2012). Naming the Bristol dinosaur, Thecodontosaurus: politics and science in the 1830s Proceedings of the Geologists’ Association, 766-778 DOI: 10.1016/j.pgeola.2012.07.012

In 1938, dinosaurs roamed the streets of Birmingham, England. Sort of. The three monsters–tottering constructions of plywood and car parts–trundled along in a parade meant to celebrate the transformation of the town from its prehistoric origins to a major industrial center. Best of all, io9 has found some footage of the grotesque dinosaurs in action. The clip is short, but you can see the trio of Egbert, Ogbert and Little Sidney taunt the accompanying guard of a hundred anachronistic cavemen. By the time of the “Stone Age,” the non-avian dinosaurs were long gone–humans never met such creatures. All the same, I have to admire the ingenuity of the people who constructed the parade dinosaurs. As io9′s Cyriaque Lamar suggested, organizing a formation of smoke-bellowing dinosaurs “is how every anniversary should be commemorated, regardless of the occasion.”

The skull of a mounted Tarbosaurus. Photo by Jordi Payà, from Wikipedia.

The road home for an illicit Tarbosaurus is bound to be a long one. Earlier this summer, federal agents seized a skeleton of the tyrannosaur Tarbosaurus that had been put up for auction in New York City. The sale price for the dinosaur topped $1 million, but, as was long suspected and was soon made clear, the dinosaur was illegally smuggled into the United States. Even worse, the skeleton itself was almost certainly illegally excavated from Mongolia and subsequently smuggled out of the country. Mongolian officials, professional paleontologists, lawyers, and United States officials moved quickly to prevent the dinosaur from disappearing into the collection of the tyrannosaur’s prospective buyer.

I see these events as a victory. The fossil black market has robbed many countries of their natural history heritage, especially Mongolia and China, and I was glad to see so many concerned activists work together in the hope that the Tarbosaurus might be returned. As expert paleontologists have concluded, the Tarbosaurus undoubtedly came from Mongolia–a country with strict heritage laws about who can collect fossils, what can be collected, and what subsequently happens to the fossils. All the evidence accumulated so far supports to idea that the Tarbosaurus was looted from Mongolia. But the man who assembled the controversial Tarbosaurus doesn’t agree, and has filed a claim on the dinosaur. Eric Prokopi, who obtained the Tarbosaurus and stood to profit from the auction, believes that the dinosaur is rightly his.

As reported by Wynne Parry at LiveScience, Prokopi and his attorney are trying to defend the sale of the Tarbosaurus by drawing a distinction between raw fossils and the reconstructed end product. “We are just trying to create a factual distinction between a fossil which is imported and a finished piece which is what was being sold at the auction,” Prokopi’s attorney Michael McCullough said.

But this strategy entirely misses the point. Prokopi obviously put a great deal of time, money, and effort into the tyrannosaur skeleton, but that does not change the fact that the skeleton was almost certainly illegally excavated and, as customs documents demonstrate, smuggled into the United States through a false description. How hard Prokopi worked is absolutely irrelevant. And, frankly, Prokopi should have known better than to put so much effort into a significant dinosaur specimen when he admittedly had no idea where the specimen came from or how it was collected. The bottom line is quite simple–the Tarbosaurus was illegally removed from its home strata, and it should be returned to its country of origin of soon as possible.

Contrary to a popular myth, Stegosaurus did not a have a butt brain. Photo by the author at the Utah Field House of Natural History in Vernal, Utah.

There’s no shortage of dinosaur myths. Paleontologist Dave Hone recently compiled a list of eight persistent falsehoods over at the Guardian–from the misapprehension that all dinosaurs were huge to the untenable idea that Tyrannosaurus could only scavenge its meals–but there was one particular misunderstanding that caught my attention. For decades, popular articles and books claimed that the armor-plated Stegosaurus and the biggest of the sauropod dinosaurs had second brains in their rumps. These dinosaurs, it was said, could reason “a posteriori” thanks to the extra mass of tissue. It was a cute idea, but a totally wrong hypothesis that actually underscores a different dinosaur mystery.

Dinosaur brain expert Emily Buchholtz outlined the double brain issue in the newly-published second edition of The Complete Dinosaur. The idea stems from the work of 19th-century Yale paleontologist Othniel Charles Marsh. In an assessment of the sauropod Camarasaurus, Marsh noticed that the canal in the vertebrae over the dinosaur’s hips enlarged into an expanded canal that was larger than the cavity for the dinosaur’s brain. “This is a most suggestive fact,” he wrote, and, according to Buchholtz, in 1881 Marsh described a similar expansion in the neural canal of Stegosaurus as “a posterior braincase.”

Sauropods and stegosaurs seemed like the perfect candidates for butt brains. These huge dinosaurs seemed to have pitiful brain sizes compared to the rest of their body, and a second brain–or similar organ–could have helped coordinate their back legs and tails. Alternatively, the second brain was sometimes cast as a kind of junction box, speeding up signals from the back half of the body up to the primary brain. That is, if such an organ actually existed. As paleontologists now know, no dinosaur had a second brain.

There are two intertwined issues here. The first is that many dinosaurs had noticeable expansions of their spinal cords around their limbs–a feature that left its mark in the size of the neural canal in the vertebrae. This isn’t unusual. As biologists have discovered by studying living species, the enlargement of the spinal cord in the area around the limbs means that there was a greater amount of nervous system tissue in this area, and dinosaurs with larger expansions around the forelimb, for example, probably used their arms more often than dinosaurs without the same kind of enlargement. The expansion of the neural canal can give us some indication about dinosaur movement and behavior.

But the so-called “sacral brain” is something different. So far, this distinct kind of cavity is only seen in stegosaurs and sauropods and is different than the typical expansion of the neural canal. There was something else, other than nerves, filling that space. Frustratingly, though, we don’t really know what that something is.

At the moment, the most promising idea is that the space was similar to a feature in the hips of birds called the glycogen body. As sauropod expert Matt Wedel has pointed out, this space stores energy-rich glycogen in the hips. Perhaps this was true for the sauropods and stegosaurs, too. Again, though, we hit a snag. We don’t really know what the glycogen body does in birds–whether it helps with balance, is a storehouse for nutritious compounds that are drawn upon at specific times or something else. Even if we assume that the expansion in dinosaurs was a glycogen body, we don’t yet know what biological role the feature played. Dinosaurs didn’t have hindbrains, but the significant spaces in the hips of stegosaurs and sauropods still puzzle paleontologists.