THE DINOSAUR WITH A THUMB ON ITS NOSE

-Jack R. Holt

A GIFT

Frenzy yourself into sickness and dizziness – Christmas is over and Business is Business.  -Franklin Pierce Adams

        Just before Christmas in the early 1960’s my parents took me to one of the best bookstores in Tulsa and asked me to pick out a book as one of my gifts.  I looked around for a short while but my eyes kept coming back to a large formatted book filled with color, sepia, and black and white plates.  The book was called Prehistoric Animals by Joseph Augusta, illustrated by Zdenek Burian.  Of course, it was one of the most expensive books in the place, and my parents indicated that I should not get my hopes up.  Anyway, I did and dreamed of that book until Christmas morning.  I remember sneaking down in the wee hours of that morning to look at the tree.  There, in anticipation of my action and to buy a little more sleep for themselves, my parents had placed the book with a note on it, “ You can open this now.”  I did.  By morning, I had read the whole thing (there is not much text) and studied all of the plates.  One of them illustrated a kangaroo-like Iguanodon plodding across the page (see Figure 1).

FIGURE 1. An illustration of Iguanodon by Zdenek Burian.

        This was the standard reconstruction of most bipedal dinosaurs then.  They stood upright with their tails dragging on the ground and their heads on a gracefully curved neck.  The reconstruction of animals like Iguanodon had a history that went back nearly 200 years.  Then, like today, their posture, behavior, etc. were based on similar animals that are alive today.  This came from the then fledgling discipline of comparative vertebrate anatomy.  Georges Cuvier (1769-1832), the most celebrated scientist of his day, was the principal architect of the comparative method that supported the study of dinosaurs from their discovery to the present.

CUVIER’S METHOD

I got into Cuvier’s sanctum sanctorum yesterday, and it is truly characteristic of the man.  In every part it displays that extraordinary power of methodizing which is the grand secret of the prodigious feats which he performs annually without appearing to give himself the least trouble…-Charles Lyell

        Georges Cuvier was born to a Huguenot family near Stuttgart in 1769.  He showed early promise as a natural historian and was sent to university by the Duke of Wurtenberg.  After working as a tutor in Normandy, his work on marine animals attracted the attention of the scientific elite in Paris.  Cuvier accepted a research position in Paris and spent the rest of his professional life working on the anatomy of animals, particularly vertebrate animals there.

        In 1795, just months after he arrived in Paris, the skeleton of an elephant was discovered in the Gypsum mines of Monmartre (this was the source of the original Plaster of Paris).  Elephants in Paris!  Some assumed that the presence of the animals could be explained easily.  For example, the elephants were part of Hannibal’s army and just got lost on their way to Rome.

        Cuvier examined the bones and realized that they did not conform to the bones of the two known elephant species, the African or the Indian Elephant.  They were so big that he called the new elephant Mammothus.  He also supposed that the mammoths were no longer alive anywhere on the earth because they were just too big to remain unnoticed.  The only other alternative was that the elephants from the gypsum quarry represented a species, which was no longer alive.  This was a bold statement and set the stage for the acceptance of the concept of extinction.

        Soon, Cuvier began to be brought a wide assortment of fossil bones.  It became clear to him that the bones represented many species, which are no longer alive.  Also, they seemed to fall into particular periods of time.  Extinct mammals were found in younger rocks than extinct reptiles, etc.  He explained the succession of fossils as a series of creations each of which was destroyed to prepare for the next creation (much like the Biblical Flood).

        Cuvier realized that each major group of animals had its own distinctive architecture.  From that he defined the principle of “the correlation of parts” which stated that the anatomy of every bone, muscle and bodily organ was interrelated.  Thus, a reconstruction of an extinct animal could be made by comparing its remains to the structure of similar living animals.  Because of his encyclopedic knowledge of comparative anatomy, Cuvier was able to reconstruct almost any animal from fragmentary remains by applying his principle of the correlation of parts.

IGUANAS, ELEPHANTS, & KANGAROOS

The Megalosaurs and Iguanodons rejoicing in those undeniably most perfect modifications of the Reptilian type, attained the greatest bulk, and must have played the most conspicuous parts, in their respective characters as devourers of animals and feeders upon vegetables, that this earth has ever witnessed in … cold-blooded animals.  -Richard Owen

        Thus, an English physician named Gideon Mantell (see Figure 2) took some fossil bones to Cuvier in 1823.  Mantell had found the fossil bones, teeth, and a curious horn-like structure in the south downs of England over a 5 year period.  He was convinced that the bones represented an extinct animal of enormous proportions.  When he showed them in England, Geologists said that the fossils were not very important.  Even Cuvier disputed their age and said that they were nothing more than a collection of extinct hippopotamus and rhinoceros bones.

        Undaunted, Mantell believed that the fossils were the remains of an extinct reptile.  He spent many hours in the Hunterian Museum in London where he compared his fossils with the bones and teeth of living reptiles.  Finally, he met Samuel Stutchbury who was doing research on iguanas.  Stutchbury recognized the teeth as similar to those of certain Central American iguanas.  Mantell was thrilled and called his new animal Iguanodon (iguana tooth).

FIGURE 2. Gideon Mantell and his wife Ann who is credited with finding the first Iguanodon tooth.

        He applied Cuvier’s principle to the reconstruction of the extinct animal.  If it was an iguana, the bones and teeth suggested that Iguanodon must have been more than 60 feet long!  The animal walked on all four legs, was a herbivore and had a large horn on its nose.

FIGURE 3. Mantell’s reconstruction of Iguanodon.

        Mantell presented his work to the Royal Society in London and published the report in 1825.  There he presented his new animal as a member of huge reptiles that lived on the earth long before mammals.  This time his report was accepted because an eminent British Geologist, William Buckland, had published on the remains of another large, extinct reptile which he called Megalosaurus (big lizard). However, Buckland’s monster was a carnivore.  Upon reviewing the evidence, Cuvier magnanimously admitted his own errors and agreed with the interpretations of Mantell and Buckland.

FIGURE 4. Richard Owen’s reconstruction of Iguanodon and Megalosaurus locked in mortal combat.

        It was not long before other giant prehistoric lizards were found.  Richard Owen (1804-1892), a British anatomist and paleontologist, began to study the enormous reptiles and realized that they were very different from lizards.  In 1841 he noted several unifying features that defined them as a separate group within the reptiles.  Although he called them Dinosauria (terrible lizards), Owen explained that his intent was to label them as the “fearfully great lizards”.

        A lost world of giant lizards fired the imagination of Victorian society.  Owen reconstructed the animals and had the monetary support to hire Benjamin Waterhouse Hawkins to make life-sized models of many Dinosaurs including Megalosaurus and Iguanodon for London’s Crystal Palace in 1854.  At the opening of the exhibition, a legendary dinner party was held.  The guests were seated within one of the Iguanodon models.  The point was that these animals were big!

        Owen used elephants and large mammals as models for his reconstructions.  Instead of the splayed legs of a lizard, he had given them large column-like legs.  Owen’s Megalosaurus resembled a scaly bear with a long lizard-like head.  The Iguanodon also had a heavy rhinoceros-like body, complete with the horn on its nose (see Figure 4).  By 1881 Richard Owen became the first curator of the British Museum of Natural History.  The star attraction was (and still is) its collection of dinosaur fossils.  Ironically, in 1880, several dozen complete skeletons of Iguanodon were found in a coal mine in Bernissart, Belgium. 

        The task of mounting the Iguanodons of Bernissart for the Belgian Royal Museum fell to a young French mining engineer named Louis Dollo (1857-1931).  His first task was to remove the fossil bones of 40 Iguanodons that had been taken from the mines.  Then he had to prepare them for exhibit.  He immersed himself in the task so completely that he did not take a vacation for 22 years (the first mounted skeletons took 25 years to complete).

        Figure 1 illustrates Dollo’s reconstruction of Iguanodon.  This time, the animal looked more like a kangaroo with a dragging tail and an upright stance.  His Iguanodon was a far cry from Owen’s rhinoceros.  The most important result was that Iguanodon stood upright on its strong hind legs.  Also, it had a horny beak like a turtle or a bird.  Its pelvis was birdlike as well.  The spike which had been interpreted as a horn for the past 60 years turned out to be a highly modified thumb.  Dollo interpreted a fissure in the skull as support for a very large tongue.  So, he assumed that the animal ate much like a giraffe with a long, prehensile tongue.  He assumed that the tail, flattened laterally, would have made it a powerful swimmer in avoiding predators. 

        The Natural History Museum of Paris attempted to acquire a skeleton of one of the Bernissart Iguanodons at the turn of the 20th century.  However, the public outcry against exporting their national treasures forced Paris to accept a plaster cast, the plaster cast that I saw.  The Dollo reconstruction remained the last word in Iguanodon structure, appearance, and behavior.  Dinosaurs remained big, slow, cold-blooded animals that moved through swamps in slow motion.  Indeed, in the face of the arrival of mammals, dinosaurs seemed destined to extinction.  Indeed, Dollo himself suggested that the dinosaurs became extinct because their brains were not sufficient to allow them to compete with mammals.  This view of progress in evolution (a view that Darwin did not have) has been challenged by new ideas about how dinosaurs lived and became extinct.

NEW VIEWS OF DINOSAURS

The work of paleontologists – the scientists who work on fossils – is truly a detective story, an unceasing search for new clues to unravel the mysteries of the ancient world.  -David Norman

        When I was a graduate student just completing my degree in Zoology before I went to the Botany-Microbiology Department at the University of Oklahoma, I decided to take a graduate-level vertebrate paleontology course just for fun.  I was a little concerned to learn that I was the only non-geology student in the class.  However, my concern melted away when a 30-something man walked into the room and told us in a heavy accent that he had been a student of Joseph Augusta, the author of my Prehistoric Animals book of many Christmases ago.  It was one of the most enjoyable courses of my graduate career.  He still taught the Dollo version of bipedal dinosaurs.  However, he did hint that there were other interpretations that were being considered.  Since then, for the past 25 years David Norman, Robert Bakker, Jack Horner, and others have found evidence to suggest that dinosaurs were much more active and complex than we were able to believe when they were just big reptiles.  It seems that large herbivores like Iguanodon almost certainly were warm blooded and ran in herds.  They had the complex behaviors which are common to active herd animals.  They probably laid their eggs in rookeries and cared for their young.

FIGURE 5. Reconstruction of Iguanodon by David Norman.

        In his reexamination of the Bernissart skeletons, David Norman, curator of the Sedgewick Museum at Cambridge, has reinterpreted many aspects of Dollo’s reconstructions.  First, the most notable change was that the tail was held stiffly by a tendons such that the animal could not have dragged it.  Also, the structure of the neck, pelvis, etc. all suggest that Iguanodon walked with its body held almost horizontally such that it occasionally dropped to all four feet (this has been borne out by such impressions in Iguanodon trackways).

        Norman also showed that Dollo’s long tongue hypothesis was based on a faulty interpretation of the skulls.  The horny beak likely just clipped the leaves and branches that it fed on.  Also, he suggested that the sides of the mouth were covered with a cheek like mammals and not open like the jaws of a lizard.  Thus, Iguanodon could chew (an adaptation suggested by the battery of hundreds of well-worn and easily replaced molars).

        Were Cuvier, Mantell, Owen, Marsh and others wrong?  Not really; reconstructions based upon fragmentary evidence are always difficult.  Their models of Iguanodon were based on certain ideas about its animal associations.  When dinosaurs were considered lizards, they were reconstructed as lizards (just as Cuvier’s principle of the correlation of parts required).  Then, Iguanodon became a large reptile that stood on its hind legs.  Still, its tail dragged along behind it as it plodded along.   Now, the new interpretation requires a different group of animals to use for comparison.  In the new interpretation of dinosaurs Cuvier’s principle is still valid, but the animal group with which they are compared has changed from reptiles to birds.

Sources which I used to write the essay

Augusta, Joseph and Zdenek Burian. n.d. Prehistoric Animals. Spring Books. London.

Bakker, Robert T. 1986. The Dinosaur Heresies. Zebra Books, Kensington Publishing Corp. New York.

Bakker, Robert T. 1995. Raptor Red. Bantam Books. New York.

Colbert, Edwin. 1983. Dinosaurs, an Illustrated History. Hammond Inc. New York.

Cuvier, Georges. 1863. The Animal Kingdom Arranged According to its Organization. Henry G. Bohn. London.

Desmond, Adrian J. 1975. The Hot-Blooded Dinosaurs, A Revolution in Paleontology. The Dial Press. New York

Figuier, Louis. 1866. The World Before the Deluge. Cassel, Peter, Galpin & Co. New York.

Gould, Stephen Jay. 2002. The Structure of Evolutionary Theory. Belknap. Harvard. Boston.

Horner, John R. and James Gorman. 1988. Digging Dinosaurs. Harper and Row, Publishers. New York.

Lessem, Don. 1992. The Kings of Creation. Simon & Schuster. New York.

Norman, David. 1991. Dinosaur! MacMillan. New York.

Spalding, David A.E. 1993. Dinosaur Hunters. Prima Publishing. Rocklin, CA.

Trefil, James and Robert Hazen. 2000. The Sciences, An Integrated Approach. John Wiley & Sons, Inc. New York.

Wilford, John N. 1985. The Riddle of the Dinosaurs. Vintage Books. New York.