December 11, 2012
Dinosaurs are often thought of as kid’s stuff. In America, at least, going through a “dinosaur phase” is just another part of childhood, and somewhere along the way we’re expected to stop acting like walking encyclopedias to Mesozoic life. Yet this narrow view of dinosaurs as nothing more than pre-teen kitsch obscures the essential truths these animals can share with us about evolution, extinction, and survival.
As paleontologist Michael Novacek argues in the video above, the history of dinosaurs is also our history–our mammalian ancestors and relatives snuffled and scurried through a dinosaur-dominated world for more than 150 million years. We can’t understand where we came from without considering dinosaurs. And, says paleontologist Matt Bonnan, “Dinosaurs put our place in the world into perspective.” By asking questions about dinosaurs–when did they live and what was the world like then?–the history of life on Earth comes into focus, and the answers to these queries help us better understand the pervasive forces of evolution and extinction through time.
These critical aspects of nature can be difficult to detect on the timescales of our lives, but become much more apparent when we can peek into deep time by sifting through the remains of creatures that roamed the Earth long ago. An individual dinosaur discovery might not have any practical use or even significantly change our understanding of the past, but when considered together with the ever-growing body of research about dinosaurs, it can help us understand how we came to be on this planet and may even give us some clues about the future–how species emerge and decline, how creatures adapt, and how life evolves after catastrophic extinction events.
What do you think is the best case for the importance of studying dinosaurs?
October 29, 2012
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.
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.
October 11, 2012
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]
Pennycuick, C. 1986. Mechanical Constraints on the Evolution of Flight. Memoirs of the California Academy of Sciences. 8, 83-98
September 19, 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.
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
July 30, 2012
We will never know the identity of the first person to discover a fossilized dinosaur. Sure, the British naturalist William Buckland described Megalosaurus in 1824, now regarded to be the first dinosaur to be scientifically named, but people were finding dinosaurs long before Buckland puzzled over his “great lizard.” As Adrienne Mayor and other geohistorians have documented, people all over the world have been recognizing and wondering about dinosaurs and other fossilized creatures for centuries – from the Greeks to Native Americans. In fact, as paleontologist Ken McNamara has argued, prehistoric people may have even picked up fossils and fashioned them into tools or decorations, imbuing them with special significance. Fossilized dinosaur eggshell fragments have even been used in necklaces, although who made the jewelry and why is unknown. The point is, we have a long, deep history with dinosaur bones.
Strangely, prehistoric and ancient people with a pre-scientific understanding of nature had a better handle on what fossils represented than western scholars and naturalists of the 16th, 17th, and 18th centuries who considered fossils to simply be an attempt by rock to imitate life. While many ancient and aboriginal cultures considered dinosaur bones to be the remains or real creatures, western savants often passed off fossils as weird “sports of nature” that were created by supernatural forces within the earth. After all, religious dogma dictated that the world was only a few thousands of years old, and that the whole earth was created as is within that compressed timeframe. There was no room in biblical chronologies for fossils, so, therefore, the shark teeth, clam shells, mammal skeletons, and dinosaur bones had to be intricate fakes that could too-easily trick the unwary. It took decades of research, discovery, and re-discovery of older ideas before naturalists realized that fossils were true vestiges of prehistoric life, and that extinction was a reality. By 1800, at the latest, a scientific understanding of prehistory was finally forming.
Although giant ground sloths, mammoths, and mosasaurs were among the first fossil celebrities, European naturalists started to pick up the trail of dinosaurs around the same time. They just didn’t know what they were looking at. Remember that it wasn’t until 1842 that the British anatomist Richard Owen even coined the word “dinosaur”, so, prior to that time, dinosaur bones were often thought to be the remains of reptiles and other large creatures. The fragmentary nature of the earliest dinosaur finds further obscured the true identity of the fossils.
Science historians David Spalding and William Sarjeant cataloged some of the earliest recorded dinosaur finds in their contribution to The Complete Dinosaur. These were cryptic fossils – we can recognize them as dinosaurs now, but researchers at the time only had the slightest idea of what they were looking at. The most famous example is the end of a fossil femur described by the British naturalist Robert Plot in 1677. In a listing of geological curiosities – including what he believed to be petrified eyes and other oddities – Plot mentioned the end of the thigh bone as “a real Bone, now petrified”, and the fossil’s size led him to suggest that the bone had come from an elephant brought to Britain by the Romans some centuries earlier. By looking back to illustrations of the bone – sadly lost a long time ago – paleontologists suspect that the femur fragment belonged to Megalosaurus, or a similar dinosaur.
Plot wasn’t the only one to figure and describe dinosaur fossils. In 1699, naturalist Edward Lhuyd misidentified several dinosaur teeth for fossil fish teeth, and other naturalists continued to write about the strange bones and teeth that they acquired for their museums and personal collections. Spalding and Sarjeant provide the full listing in their account, but the accumulated, misapprehended dinosauriana included a theropod limb collected by John Woodward in the early 1700s, vertebrae and a femur found in France, a large dinosaur limb bone found in southwestern New Jersey in 1787, so-called “turkey tracks” found in the Connecticut Valley during the early 1800s, and a spinosaur tooth mistaken for a crocodile fossil and called Suchosaurus by Richard Owen in 1824. And I have to make a special mention of one of my favorite examples. In 1806, Meriwether Lewis – of the legendary Lewis and Clark expedition through the Louisiana Purchase – noticed a large bone in a cliff near what is now Billings, Montana. He thought the bone belonged to an enormous fish, but, based upon his notes and description, paleontologists are confident that Lewis had actually spotted a dinosaur rib in Montana’s fossil-rich Hell Creek Formation.
Naturalists in Europe and North America most certainly cataloged and collected dinosaur bones, but the rare, fragmentary nature of the fossils led researchers to attribute the bones to familiar animals, albeit of giant size. Even William Buckland, who described Megalosaurus, thought his animal was akin to a giant monitor lizard, and it wasn’t until Owen coined the word “dinosaur” that the various, scattered, enigmatic remains started to come together within a peculiar group of hitherto unknown animals. (And it was several more decades, still, before discoveries of partial skeletons began to reveal the true form of dinosaurs.) Despite some hiccups caused by reliance on religious authority about the history of the world, our species has been wondering about the lives of the animals we now call dinosaurs for centuries. Dinosaurs have been with us, in one form or another, far longer than the word dinosaur itself.