The Paleobiology of Indricotheres
Publication Year: 2013
Written for everyone fascinated by the huge beasts that once roamed the earth, this book introduces the giant hornless rhinoceros, Indricotherium. These massive animals inhabited Asia and Eurasia for more than 14 million years, about 37 to 23 million years ago. They had skulls 6 feet long, stood 22 feet high at the shoulder, and were twice as heavy as the largest elephant ever recorded, tipping the scales at 44,100 pounds. Fortunately, the big brutes were vegetarians. Donald R. Prothero tells their story, from their discovery just a century ago to the latest research on how they lived and died.
Published by: Indiana University Press
Download PDF (83.6 KB)
Download PDF (93.4 KB)
Download PDF (28.1 KB)
Download PDF (80.0 KB)
This book is the culmination of over thirty-five years’ worth of research on fossilrhinoceroses, beginning with my first introduction to the Frick and American Mu-seum collections in 1976. I thank Dr. Earl Manning for introducing me to the fos-sil rhino collections at the American Museum and Dr. Michael O. Woodburneand the late Drs. Malcolm C. McKenna and Richard H. Tedford for all they havetaught me over the years. I thank my colleagues Drs. Spencer Lucas, Pierre-Olivier Antoine, Mikael Fortelius, Kurt Heissig, Claude Guérin, and Deng Taofor all their help and efforts in understanding rhinoceros evolution and Drs. BrianKraatz and Jonathan Geisler for their new insights into Gobi stratigraphy.The idea for this book emerged from discussions with Dr. James Farlow. Ithank Bob Sloan, Angela Burton, Mary Blizzard, and Michelle Sybert at IndianaUniversity Press for all their help in producing the book. I thank Carl Buell forhis gorgeous cover art. I thank many colleagues for lending me images; they areacknowledged in the appropriate places throughout the book. I thank Pierre-Oliver Antoine, Mikael Fortelius, James Farlow, Spencer Lucas, and Juha Saari-nen for their helpful reviews of the manuscript. The author designed and laid outthe entire book in QuarkXpress 9.3.1 software.Finally, I thank my amazing wife, Dr. Teresa LeVelle, and my wonderful sons,Erik, Zachary, and Gabriel, for their love and support during the writing of thisbook on my sabbatical in 2011. Donald R. ProtheroLa Crescenta, California August 2012Figure 1.1. The American Museum Mongolian expedition, with its Dodge cars and hundreds ofcamels, near the Flaming Cliffs of Mongolia. (From Andrews, 1932, Plate LV.)...
Download PDF (399.8 KB)
...“The New Conquest of Central Asia”In 1922, the American Museum of Natural History in New York City spon-sored one of the most ambitious scientific expeditions ever attempted. Led by thelegendary explorer Roy Chapman Andrews (1884–1960), the expedition traveledto China and Mongolia with a huge caravan of seventy-five camels (each carrying180 kg or 400 pounds of gasoline and other supplies), three Dodge touring carsand two Fulton trucks, and a large party of scientists, guides, and helpers (Fig.1.1).The party included not only Andrews, but also paleontologist Walter Granger(1872–1941), a veteran of many fossil-hunting expeditions in the U.S. and else-where, who had prior experience hunting fossils in China. There were also twogeologists (Charles P. Berkey and Frederick K. Morris) and many other assistantsto drive the trucks and cars and camels, cook the food and set up the camp, andact as guides and interpreters.The expedition was sent by famous paleontologist and American MuseumDirector Henry Fairfield Osborn (1857–1935) to find important fossils from Cen-tral Asia. Osborn believed that Asia was the center of origin of most mammalgroups, including humans, and could contain the legendary “Missing Link” thatwas long predicted by biologists and paleontologists. Osborn used this argumentnot only to authorize the expedition, but also to raise funds from his many richfriends who were donors or trustees of the Museum. Osborn told Andrews, “Thefossils are there. I know they are. Go and find them.”Andrews provided a colorful and detailed account of all the expeditions inhis massive volume with a very un-politically correct imperialist title, The NewConquest of Central Asia. One of the most incredible finds of all occurred in thethird field season (1925), as described by Andrews (1932, pp. 279–280):The credit for the most interesting discovery at Loh belongs to one ofour Chinese collectors, Liu Hsi-ku. His sharp eyes caught the glint of awhite bone in the red sediment of the steep hillside. He dug a little andthen reported to Granger who completed the excavation. He was amazedto find the foot and lower leg of a Baluchitherium STANDING UP-RIGHT, just as if the animal had carelessly left it behind when he tookanother stride. Fossils are so seldom found in this position that Grangersat down to think out the why and wherefore. There was only one pos-sible solution. Quicksand! It was the right hind limb that Liu had found;therefore, the right front leg must be farther down the slope. He took thedirection of the foot, measured off about nine feet, and began to dig.Sure enough, there it was, a huge bone, like the trunk of a fossil tree,also standing erect. It was not difficult to find the two limbs of the otherside, for what had happened was obvious. When all four legs were ex-cavated, each one in a separate pit, the effect was extraordinary [Fig.1.2]. I went up with Granger and sat down upon a hilltop to drift in fancyback to those far days when the tragedy had been enacted. To one whocould read the language, the story was plainly told by the great stumps.Probably the beast had come to drink from a pool of water covering thetreacherous quicksand. Suddenly it began to sink. The position of theleg bones showed that it had settled slightly back upon its haunches,struggling desperately to free itself from the gripping sands. It must havesunk rapidly, struggling to the end, dying only when the choking sedi-ment filled its nose and throat. If it had been partly buried and died ofstarvation, the body would have fallen on its side. If we could have foundthe entire skeleton standing erect, there in its tomb, it would have beena specimen for all the world to marvel at.I said to Granger, “Walter, what do you mean by finding only thelegs? Why don’t you produce the rest?” “Don’t blame me,” he answered,“it is all your fault. If you had brought us here thirty-five thousand yearsearlier, before that hill weathered away, I would have the whole skeletonfor you!” True enough, we had missed our opportunity by just about thatmargin. As the entombing sediment was eroded away, the bones wereworn off bit by bit and now lay scatted on the valley floor in a thousanduseless fragments. There must have been great numbers of baluchitheresin Mongolia during Oligocene times, for we were finding bones andfragments wherever there were fossiliferous strata of that age.Although Andrews’ storytelling skills are vivid, his account of the quicksandis a bit too much like the Hollywood movie version, rather than one based on re-ality. Fake quicksand in movies sucks the victim down in minutes until he or sheis completely submerged. Real quicksand is a slurry of sand and water that re-mains fairly firm and solid until you disturb it. Then the water between the sandgrains is mobilized, and it becomes what is known as a fluidized sedimentaryflow. The disturbed water from the pores between the sand grains pushes the sandgrains apart so they flow freely, and you can sink down into the slurry. When youstop moving and disturbing the grains, the water also stops moving, and the entiremixture solidifies like concrete—unless you thrash around again and liquefy themixture. Because a mixture of sand and water is actually denser than water alone,any body (human or animal) will float until it reaches its point of neutral buoy-ancy. Thus, it is impossible to sink into quicksand above your head. Even if youthrash around in a panic and keep it liquefied so you sink as low as possible, youwill still float at the top even higher than you would float in water alone.The real problem with quicksand is that it is sticky and holds your limbsdown so you can’t get out easily, and the more you struggle, the deeper you sinkuntil finally you are floating at your point of neutral buoyancy. People or animalstrapped in quicksand do not die because they sink down below their head, butbecause they become exhausted and thirsty since they cannot pull themselves outand remain trapped until they die. If you grab a branch or a rope or any other firmanchor outside the quicksand, you can pull yourself out quite easily—but mostcreatures trapped in quicksand have no way to pull themselves out. If you shouldever become trapped yourself, the best advice is to try to lie flat in it as you wouldFigure 1.2. Four indricothere limbs, standing vertically just as they were buried in quicksand.Walter Granger works in the background. (Image number 285735; courtesy American Museumof Natural History Library.)when you float in water and pull yourself out with a stick or rope or any otherform of anchoring.In the case of this trapped indricothere rhino, it probably was mired down toits legs (as they found it), but the rest of the body would not have sank muchdeeper. Contrary to what Andrews wrote, it would not have toppled sideways ifit were half-buried, since the quicksand was thick and stiff enough to trap its legsin an upright pose without allowing the body to lean sideways, let alone escapefrom it. Instead, with its legs trapped, the indricothere died either of starvation orby being eaten or scavenged by predators taking advantage of the helpless crea-ture. Once it became trapped and could no longer struggle to liquefy the sand, itsexposed upper body was easy pickings for predators and scavengers, which iswhy none of its other bones were there.Quicksand can be tricky. I’ve seen a caravan of four-wheel-drive trucks reacha sandy wash where the first vehicle drove across easily. However, its weight dis-turbed the water and fluidized the saturated sand on the creek bottom, so thatwhen the second truck rolled over it, the sand was mobilized, and the second ve-hicle sank in to its axles. It became really stuck, requiring trucks on both sideswith tow cables and winches to pull it out—after everyone had dug out its wheelswith a shovel....
Download PDF (559.9 KB)
Pilgrim’s ProgressBefore we look further into the life of indricotheres, we need to discuss the placeswhere they have been found and the nature of the fossils discovered so far. Thisnaturally leads into a story of the paleontologists who have taken great risks totravel to remote and dangerous places, from central Asia to Mongolia to Chinato regions of what is now Pakistan (Fig. 2.1). As we saw with Andrews’ accountof the American Museum Mongolian expeditions, almost all of these discoverieswere made at great risk and after enduring much hardship. The rugged individualsand pioneering paleontologists who made these discoveries are just as colorfuland interesting as the extinct creatures they found.The story of the discovery of indricotheres begins with just such a colorfulpioneering paleontologist, Henry Guy Ellcock Pilgrim (Fig. 2.2), whose careerwas described by Lewis (1944). Born on Christmas Eve 1875 at his family’s colo-nial mansion in Barbados, Guy Pilgrim began his education at Harrison Collegeon the island. Unable to get the education there that he needed to further his careergoals, he traveled to England and transferred to University College, London.There he finished his B.S. degree in 1901 and eventually earned his D.Sc. degreein 1908.However, right after he earned his B.S. degree he began his remarkable careeras a geologist and paleontologist in the Middle East and southern Asia. In 1902,he was appointed to a post at the Geological Survey of India, then a Britishcolony. From that position the ambitious young man traveled widely over south-ern Asia and the Middle East, doing geological mapping and reconnaissance forthe Crown Colonies and finding numerous fossils. This work was truly ground-breaking because almost no real geologic mapping or research had ever been con-ducted over this wide region before. Pilgrim was a true pioneer. His travels tookhim to Arabia, Persia (now Iran), Baluchistan (now part of southern Pakistan),Bhutan in the Himalayas, and the Punjab and Simla Hills in British India. By1905, he was also appointed as a paleontologist at the Geological Museum ofCalcutta, eventually making the post of curator in 1909 after he finished his doc-torate. Within a few years he began to publish his travels and research, startingwith two memoirs on the geology of the Persian Gulf and the Arabian Peninsula,the first published in 1908 and the second later in 1924. Later, oil geologists usedhis pioneering mapping to discover the oil wealth of the Persian Gulf, where mostof the world’s oil is still produced. Pilgrim was the first European to visit TrucialOman, and the first geologist to explore Bahrain. His discovery of the domedstructure there eventually led to the great discoveries of oil in Bahrain and otherPersian Gulf countries.However, his greatest paleontological contribution came from mapping andfossil collecting in the Siwalik Hills of what is now Pakistan, which is consideredone of the most complete and fossiliferous continuously exposed sequences ofMiocene and Pliocene rocks anywhere in Asia. Earlier paleontologists, such asHugh Falconer, Proby Cautley, and Richard Lydekker, had already made the firstcollections there, roughly mapped some of the geology, and described some ofthese fossils when they reached Britain, but their work was preliminary and in-Figure 2.1. Index map of some of the early indricothere localities in Asia, with their politicalboundaries as of 1923 (Osborn, 1923a.) 1 is Dera Bugti, Baluchistan, Pakistan; 2 is the locationof the first Indricotherium specimens north of the Aral Sea, Kazakhstan; 3 are the Hsanda Goland Loh formations, Mongolia; 4 is Iren Dabasu, Mongolia.complete. Pilgrim mapped and collected the area in much greater detail and re-alized that the Siwalik sequence spanned a great deal of time with many differentsuccessive faunas showing remarkable evolutionary change. Since the 1970s somuch research has been done on dating the Siwalik sequence and studying itsmammals that it is considered the “gold standard” for understanding the last 23million years of climate and evolution in Asia. According to Lewis (1944), thelegendary paleontologist W. D. Matthew wrote: “The admirable later work of Pil-grim was the first to make clear the distinctions between the successive faunas,and added very largely to the faunas.” Edwin H. Colbert (who worked on Siwalikmammals himself in his early career before turning to dinosaurs) wrote: “Dr. Pil-grim virtually opened the field in the discovery and study of Lower Siwalik ver-tebrates.” Pilgrim’s first publication on the topic was Preliminary Note on theRevised Classification of Tertiary Freshwater Deposits of India (1910) followedby The Correlation of the Siwaliks with Mammal Horizons in Europe (1913).When World War I broke out, the British Army was busy in the Middle Eastdefending its colonies and battling the Turkish Army, which was allied with Ger-many and Austria. This was the same British Army portrayed in the movieLawrence of Arabia. In the movie, and in real life, the British needed T. E.Lawrence to help them unify and forge alliances with the Arabs of the region tofight the Turks. As one of the most educated and widely traveled British scientistsin southern Asia and the Middle East at the time, Guy Pilgrim also served as avaluable resource to the Army. Although the details of his service are not fullydisclosed, after the war he was decorated for his war service in Persia andMesopotamia (now Iran and Iraq).Figure 2.2. Guy Pilgrim. (Image courtesy RoyalSociety of London.)...
Download PDF (1.2 MB)
Beasts of BaluchistanThe first indricothere fossils were found in the Baluchistan (also spelled Balochis-tan) region of what was then British India (Fig. 2.1) and now part of southernPakistan. A soldier named Vickary brought back the first specimens in 1846, butthey were so fragmentary that no one knew what they were. The geological andpaleontological research there started with William Thomas Blanford in 1882–1883, Guy Pilgrim’s work in 1907–1908 (Pilgrim, 1908, 1910), and ForsterCooper’s expedition to Dera Bugti in 1909 and 1910 (Forster Cooper, 1911,1913a, 1913b, 1923a, 1923b, 1934). Very little detailed geologic mapping of theregion was done by these pioneers, since they were still conducting reconnais-sance geological investigations without the time or resources to complete detailedmodern maps or stratigraphic sections of the fossil-bearing beds. Blanford (1883)and Pilgrim (1910) published only minimal descriptions of the Bugti beds, andForster Cooper (1911, 1913a, 1913b, 1923a, 1923b, 1934) made almost no men-tion of the geology at all in his many publications on the fossils found there. AfterForster Cooper’s last expedition to the region in 1911, almost no further collectingor research was done in the area until the late 1970s and 1980s, and the geologicalstory of this region was still poorly known and confusingly interpreted. What an-cient environments were represented in the Bugti beds where these creatureslived? What other fossil mammals were found with the indricotheres, and whatdo they tell us about the ancient environments? How old were the deposits? Someclaimed they were early Miocene, while others placed them in the Oligocene.Fortunately, new geological research and paleontological collecting at DeraBugti has been conducted by French and local Baluchi workers, beginning withthe efforts of Jean-Loup Welcomme and his colleagues in 1995 and 1996. Thishas resulted in a large volume of research as well as new specimens, better strati-graphic control of the fossils, and a much clearer idea of their age. They are sum-marized by Welcomme et al (1997, 2001), Welcomme and Ginsburg (1997), andMétais et al. (2009).The current understanding of the section is shown in Figures 3.1 and 3.2.The Dera Bugti beds occur in a large folded sequence of rocks, with anticlinalridges (Zin Koh Range and Bambore Range) that exposed middle-upper Eocenebeds and synclines (Dera Bugti, Gandoï), which are filled with Oligocene,Miocene, Pliocene, and Quaternary deposits (Fig. 3.2). At the base of the se-quence is the marine Eocene Kirthar Formation, first described by Blanford in1879 (Fig. 3.3). It contains marine vertebrates (mainly shark teeth), a rich mol-Figure 3.2. Structural cross-section showing the anticlines and synclines of the Dera Bugti re-gion. (Courtesy P.-O. Antoine.)Figure 3.1. Index map of the Dera Bugti localities in the Baluchistan region of Pakistan.(Courtesy P.-O. Antoine).luscan fauna (especially scallops and oysters), and the coin-sized foraminiferansknown as nummulitids, whose rapid evolution and great abundance all acrossAsia, northern Africa, and Europe make them the preferred index fossils for theEocene. The Kirthar Formation is divided into several distinct members that ap-pear to span the middle and late Eocene.Overlying the Kirthar Formation is the Chitarwata Formation, which is ap-proximately 70 m thick and appears to span the early Oligocene to the earlyMiocene in age. The lower or basal part of the Chitarwata Formation is calledthe “Nari Formation” in some references. According to Welcomme et al. (2001),...
Download PDF (928.7 KB)
Rhinos without HornsBefore we look at the gigantic indricotheres in greater detail, we need to placethem in the context of the evolution of the various types of rhinos (both extinctand surviving). Where did indricotheres come from? What were their closest rel-atives? What features allows us call these huge creatures without horns rhinoc-eroses?The last question is the first misconception that we need to clarify. Horns occurin all five living species of fossil rhino, but they are only rarely found in a fewlineages of fossil rhinos. This comes as a shock to most people who think “hornequals rhino” when they see one in the zoo or on TV and never notice the manyother features that make rhinos distinct. What is up with that horn, anyway?A rhino horn is not like that of a cow or sheep or antelope. Those creatures(the ruminants) have a horn made of a solid bony core surrounded by a sheathmade from the same protein (keratin) found in your fingernails and hair. Nor arerhino horns like the ossicones of giraffes (which are solid bone with only a fleshycovering), nor like the antlers of deer (which are solid bone, but are grown andshed each year). A rhinoceros “horn” is actually made of dense fibers of hair gluedtogether—there is no true bone within it at all. Thus, it grows throughout therhino’s life as does your hair or fingernails and breaks and wears down andabrades quite easily. Because it has no bone inside it, only perishable keratin, wealmost never find the horn preserved on fossil rhinos. (The exceptions are thefew examples of mummified woolly rhinos, which are preserved not only withcomplete horns, but even stomach contents, skin, and fur.) Instead, we must inferthe size and shape of the horn from the roughened area on the top of the skull(nose or forehead or both). This indicates the point where the hairs of the hornglued in to the skull. We can see this pattern quite clearly on both living rhinosand also the extinct rhinos that had horns. Because the size of roughened area in-dicates where a horn was once present, we are pretty sure that most extinct rhinoshad no horn whatsoever. Since the horn is not a crucial feature in recognizing arhino, we must look at other parts of the anatomy.Rhinos diverged into a wide variety of sizes and body shapes as they adaptedto a wide range of lifestyles (Fig. 4.1). Some were the size of a small dog, whilethe indricotheres were larger than most elephants. Some had typical rhino pro-portions, while others had long legs for running, and still others had short legsand squat hippo-like bodies for living in the water. Most rhinos had no horns, butsome had a single horn on the nose (the living Indian rhino and many extinctforms), or a huge horn only on the forehead (a group called elasmotheres). Somehad a pair of horns on the nose side-by-side (evolved independently in two dif-ferent lineages), while others had horns in tandem, one behind the other on thenose and forehead (the living African rhinos). Some had a trunk or proboscis likea tapir or mastodont (with or without horns). In many parts of North Americanand Eurasia, rhinos are among the most common mammal fossils. Except whenthere were mastodonts or mammoths around, they were among the largest mam-mals on the landscape.So if neither horns nor any rhino body shape are diagnostic of a fossil rhino,how can we tell if it’s a rhino in the first place? There are many distinctive featuresof the skull and skeleton that allow a paleontologist to recognize a rhino, but theeasiest and most distinctive features to recognize are its teeth. More than anyother anatomical structure, mammalian paleontologists study and use teeth toFigure 4.2. Occlusal view of the second and third left upper molars in different rhinocerotoidtaxa (side view of lower molars below each pair). A. Amynodon, a hippo-like rhinocerotoid. B.Hyracodon, a running rhinocerotoid. C. Hyrachyus, the most primitive known rhinocerotoid.Note how the second molars are shaped like the Greek letter p, and the third molars (on the rightof figure 4.2B-C) lose the back outer crest (the metastyle), resulting in crests with a more V-shaped pattern. (From Radinsky, 1966.)identify mammal fossils. This is because teeth are covered with enamel (the hard-est substance in your body), and are much more durable and likely to be preservedthan any other part of the skeleton. In addition, teeth have a distinctive pattern ofcrests and cusps in nearly every group of mammals, reflecting their ancestry froma particular group with a unique tooth pattern. Superimposed on this basic inher-ited tooth pattern of their ancestors is the influence of what they ate as well. Theteeth of carnivorous mammals are usually sharp blades for slicing meat or stab-bing, pointed teeth for grabbing prey, while those of the herbivores have differentdistinctive patterns of crests for shredding tough vegetation. The teeth of omni-vores have the primitive pattern of simple rounded cusps on the corners of thecrown of the cheek teeth for processing a wide variety of food, from meat to veg-etation.In the case of rhinos, they adopted a cheek-tooth pattern that became stereo-typed very early in their evolution about 50 Ma. Most rhinos have upper molars(the last three cheek teeth that erupt without replacing a “baby tooth”) with threecross-crests forming a Greek letter pi (p) (Fig. 4.2). In addition, most advancedrhinos have premolars (the first three or four cheek teeth, which replace the babyteeth when the animal grows up) that also have a pi (p) pattern, or something thatapproaches it. By contrast, the lower molars have crown pattern that looks like aset of the letter L attached to one another (Fig. 4.3). There are details of the cross-crests, as well as the presence or absence of additional crests or cusps, the shapeand angle of the crest, narrow shelf-like structures (“cingula”) around the baseof the tooth, and so on that help a paleontologist recognize specific rhinos, butthe general pattern is pretty consistent within the entire group.There are other details of the skull region (especially the base of the skull andFigure 4.3. Rhino lowermolars in crown view,showing the typical "L"-shaped crest pattern. (FromLucas and Sobus, 1989;courtesy S. Lucas.)...
Download PDF (338.7 KB)
What’s in a name? A rose by any other name would smell as sweet.—William Shakespeare, Romeo and JulietSystematics and TaxonomyIn previous chapters, we have seen that the names of some these fossil rhinos areconfusing, controversial, or unsettled. Before we go further, we need to look athow animals and plants are named and what rules must be followed to see whythese disputes arise. The science of classifying is known as taxonomy (Greek,“laws of order”); any named grouping of organisms (a species, a genus, etc.) iscalled a taxon (plural, taxa). Deciding how to name a new species and genus mayseem to be a highly specialized, legalistic dimension of biology and paleobiology,not nearly as glamorous as ecology or behavior or physiology. But taxonomy isnot just naming species, because species and higher taxa reflect evolution. Tax-onomists do much more than label dusty jars in a museum. They are interestedin comparing different species and deciding how they are related and ultimatelyin deciphering their evolutionary history. They look at the diversity of organismsin time and space and try to understand the large-scale patterns of nature. Theylook at the present and past geographic distributions of organisms and try to de-termine how they got there. In short, they look at the total pattern of natural di-versity and try to understand how it came to be. Contrary to stereotypes, they areamong the most eclectic of biologists and paleobiologists.All these various enterprises go beyond conventional taxonomy and are usu-ally given the broader label of systematics. Systematics has been defined as “thescience of the diversity of organisms” (Mayr, 1969, p. 2) or “the scientific studyof the kinds and diversity of organisms and of any and all relationships amongthem” (Simpson, 1961, p. 7). Its core consists of taxonomy, but it also includesdetermining evolutionary relationships (phylogeny) and determining geographicrelationships (biogeography). The systematist uses the comparative approach tothe diversity of life to understand all patterns and relationships that explain howlife came to be the way it is. Put this way, systematics is one of the most excitingand stimulating fields in all of biology and paleobiology.Taxonomists and systematists may not be as numerous or well funded as mo-lecular biologists or ecologists or physiologists or behaviorists, but their laborsare essential. All other disciplines in biology and paleobiology depend upon tax-onomists to give their experimental subjects a name and, more importantly, togive them a comparative context. If a physiologist wants to study the organismthat is most like humans, it is the taxonomist who points to the chimpanzee, ourclosest evolutionary relative. If an ecologist wants to understand how a particularsymbiotic relationship may have developed, or the ethologist wants to understanda peculiar type of animal behavior, they need to know the evolutionary relation-ships and phylogenetic history of each organism, and these are the domain of thesystematist. Systematics provides the framework of understanding and intercon-nection upon which all the rest of biology and paleobiology are based. Withoutit, each organism is a random particle in space, and what we learn about it has norelevance to anything else in the living world.In our present age, taxonomists have become scarce as grant funding dries upand students go into more glamorous specialties that require big, expensive ma-chines. Yet one of the most important issues on this planet today—biodiversity—is within the domain of systematists. Without someone to describe, name, andcount all the species on this planet, how will we know whether we are wipingthem out catastrophically, or whether they are holding their own or even flour-ishing? Without the perspective of past diversity changes on this planet, how canwe decide the severity of human-induced mass extinction? Each time someonesurveys a patch of rainforest, trying to determine how humans have impacted thelife there, his or her first task is taxonomy. Ecologists complain that they cannotfind anyone who has the right training to identify and to describe all the newspecies of insects and birds and plants that are being destroyed even before weget to know them. Without knowing that they are there, how can we decide howimportant they might be? One of these species might hold the cure to some deadlydisease or the solution to the control of a nasty pest, but without systematic andtaxonomic research, these species go extinct before we even encounter them.In the context of paleontology, the situation is analogous. The public may thinkthat collecting big dinosaur specimens in exotic places is exciting, but it is just atiny part of paleontology. Collecting and preparing fossils is a specialized task,often performed by people with little advanced scientific training. Analyzing andunderstanding their taxonomy, geography, and phylogenetic relationships is thedomain of the systematic paleontologist. Without a properly trained paleontologistto correctly identify, name, and analyze the fossils, they are mute stones. Hoursin the laboratory and museum collections spent measuring and describing speci-mens may not seem as glamorous as visiting exotic places, but they are equallyessential. From this naming and description comes the understanding of largerproblems in paleobiology, such as: how is all life interrelated? What is the pasthistory of life? How has diversity on this planet changed? Without the foundationof systematics, these questions cannot even be approached.Rules of the RoadWhen Linnaeus and other early natural historians developed different schemesof classification, there was no general agreement on how it should be done. Lin-naeus’ system became so successful that it soon became the standard in most partsof the world, but still there were no official rules, and chaos reigned. If one sys-tematist didn’t like a particular name for an organism, he might rename it for nogood reason. Another systematist might use a name that had already been usedfor some other animal. Still another might name the species in his native languageor name the species after himself. Some taxa were given more than one name.Systematics became a battleground of natural historians squabbling over propernames, and there were no referees to break up the fights.To bring order out of this chaos, rules were needed. In 1842 Strickland pro-posed the first code for zoology. Over the years these codes have evolved, andthe first international code of zoological nomenclature was published in 1905.The current International Code of Zoological Nomenclature (ICZN) was last re-vised in 2000 (available both in printed form and online at http://iczn.org/code).Taxonomic codes of nomenclature have an important purpose: to enhance sta-bility and improve communication when creating or using taxonomic names andmaking taxonomic decisions. Systematists around the world are bound to followthese rules if they want their taxonomy to be recognized by other scientists. Ifthey fail to do so, their work may not be published because journal and book ed-itors follow the codes strictly. If systematic descriptions or new species are some-how published but do not follow the rules, they may be corrected by someoneelse who does follow the rules. At times, it seems that systematics becomesbogged down in legalistic trivia, but the rules are essential if taxonomists wantto avoid unnecessary squabbles and wasted or duplicated effort. It is comparableto knowing the rules of the road before you take your driver’s test to get your li-cense. The Department of Motor Vehicles doesn’t want you behind the wheel onthe streets if you don’t know the rules that everyone else is following. Similarly,the international community of systematists avoids “collisions” and “mistakes”by following their own internal set of “traffic rules.”Bound in bright green, the most recent edition (2000) of the ICZN runs to 306pages, covering 90 articles and 86 recommendations, with the first 126 pages inEnglish followed by a separate section in the equivalent French. (Except for theFrench, most international zoologists use English in international communicationand publication.) The arbitrary starting point of the code is 1758, which is whenthe tenth edition of Linnaeus’ Systema Naturae was published. Names and taxaproposed before that date are not bound by these rules (but may not be recognized,either). The code is built around several basic principles:1. Binomial nomenclature (Article 5)—These are the basic rules by which gen-era and species are created, named, and described. Each binomen (“double name”in Latin) must be based on Latin or latinized words from other languages to en-hance international communication across language barriers. The latinized bino-mial is not always based on actual Latin words, but it must still follow the rulesof Latin grammar. For example, if the species name is an adjective, it must be inthe same gender (masculine, feminine, or neuter) as the genus name that it mod-ifies. (Although few scientists know Latin these days, it is still useful in surprisingways.) The new taxon must be adequately diagnosed, described, illustrated,named, and published in a recognized scientific journal that is widely distributedand available to most systematists. This does not include unpublished disserta-tions and local newsletters with limited circulation. In addition to a clear defini-tion and description, the author must also indicate the geographic or stratigraphicrange of the taxon and list any relevant measurements or statistics. The originand meaning, or etymology, of the new name, is also usually indicated (althoughthis is not required). You can base names on any word as long as it is properlylatinized, except that you cannot name a taxon after yourself. (You can, however,name it after a friend, and have your friend do the same for you with a differentspecies.) Once a name has been used (even if it later proves to be invalid), it cannever be used again for another animal.The criterion of Greek or Latin roots and latinization of names has becomemore relaxed as fewer and fewer scientists are learning the classical languages.Less than a century ago, a knowledge of Latin and Greek was the standard for allscholars. I feel very fortunate that I took six years of Latin and three years ofGreek in high school and college, because this knowledge has given me a greatadvantage in remembering, spelling, and deciphering taxonomic names. It hasalso been valuable in helping me to translate century-old paleontology mono-graphs and in enabling me to correctly compose taxonomic names (and to correctthe mistakes made by others). Knowledge of Greek and Latin is becoming lessimportant now that much work is being done in China, Japan, Russia, India, LatinAmerica, and other less western European-influenced scientific communities.Consequently, scientists have gotten more and more creative with their names,often erecting names that are silly or hard for others to use. For example, mam-malian paleontologist J. Reid Macdonald (1963) gave names based on the Lakotalanguage to a number of specimens recovered from the Lakota Sioux reservationland near the old site of the Wounded Knee Massacre in South Dakota. Most non-Lakotans find them difficult to pronounce or spell. Try wrapping your tonguearound Ekgmowechashala (iggi-moo-we-CHA-she-la), which means “little catman” in Lakota. It is a very important specimen of one of the last fossil primates...
Download PDF (699.0 KB)
Building a GiantDry BonesNow that we have thoroughly explored the geology of the regions that produceindricothere fossils and their evolutionary roots within the rhinocerotoids, let uslook more closely at the monsters that still hold the record for the largest landmammal that ever lived.The most impressive part of the animal is the business end: its immense skull(Figs. 5.1B, 6.1). The nearly complete presumed male skull from Mongolia(American Museum of Natural History, or AMNH 18650) is a truly awesomesight all by itself. It measures about 1.3 meters (52 inches, or almost 5 feet) long,according to Granger and Gregory (1936), 33 cm tall at the back of the skull, 33cm wide at the base of the back of the skull, and is about 61 cm (about 2 feet)wide across the skull at the zygomatic arches. Another partial skull from Mon-golia, AMNH 26165, is even larger than this specimen, measuring about 35 cmwide at the base of the back of the skull and 35.5 cm tall at the back of the skull.An even larger partial skull from Mongolia, AMNH 26167, measures 36.5 cm atthe back of the skull base and 38 cm tall at the back of the skull. The presumedfemale skulls from Dera Bugti (Fig. 5.1A) are almost as large in most of thesedimensions (according to measurements in Forster Cooper, 1923a, 1923b), so faras can be determined from their less complete preservation and subsequent de-formation and distortion.The next thing that you notice about the skull (Fig. 6.1), besides its immensesize, is the large pair of conical upper tusks that point downward and the pair ofshort conical lower tusks that point forward. As mentioned in Chapter 4 (Figs.4.7, 4.13), these teeth are unique among all known rhinos and only occur inUrtinotherium and Paraceratherium (with all its junior synonyms). These tusksoccur at the end of an elongated snout, with a large gap (diastema) between themand the cheek tooth row. Unlike most other groups of primitive rhinos, indri-cotheres have lost all their remaining front incisors as well as the canines thatwould normally erupt right behind the incisor tusks (Figs. 4.7, 4.13). Osborn(1923a, p. 6) argued that these tusks were mainly for defensive purposes, butGranger and Gregory (1936, p. 2) suggested that “their primary function was toassist in the sudden jerking loose of shrubs by downward movements of the headand neck, since they are well placed to act thus as picks and levers, while theskull is braced to resist such stresses through its strong rostrum, down-curved zy-gomata and greatly emphasized basi-occipital eminence.”The next most striking feature is the top of the skull, with the long, smoothdomed forehead and no trace in any specimen of a roughened area that wouldserve as the attachment point for a horn. The bones above the nasal region arelong and delicate, and the opening for the nasal incision goes far back into theskull. This enlarged nasal incision is usually a mark of some kind of trunk or pro-boscis in living mammals, such as tapirs and elephants. Most reconstructions ofindricotheres ignore this feature, but they should show a very long prehensile lip,as occurs in living black and Indian rhinos with a shallower nasal incision, andpossibly even a short proboscis as well. Such a proboscis is extremely useful toleaf-eaters (browsers) like tapirs, which use them to wrap around branches asthey strip off the leaves with their front teeth. Figure 6.2 shows the head musclesand snout-lips reconstruction of Juxia by Qiu and Wang (2007). This creaturewas much smaller with a much smaller nasal incision, so it has a normal rhinoupper lip. A large indricothere would have had an even longer, more proboscis-like snout.Figure 6.1. Skull usually called "Indricotherium" (originally called "Baluchitherium grangeri,"but now Paraceratherium transouralicum) from the Hsanda Gol Formation, Mongolia (AMNH18650), showing its immense size compared to preparator Otto Falkenbach, who reconstructed itfrom many fragmentary parts. (Image number 310387; courtesy American Museum of NaturalHistory Library.)Putshkov and Kulczicki (1995) and Gromova (1959) speculated that indri-cothere tusks were primarily used to break twigs and strip bark, as well as to bendhigher branches. They also suggest that early Oligocene specimens (which theycall Indricotherium) had larger upper incisors, but that later specimens (whichthey call Paraceratherium) had no upper incisors and larger lower incisor tusks,which might have suggested a less leaf-eating and more bark-eating type of diet.However, if Lucas and Sobus (1989) are right, these animals are all in the samegenus, and the alleged difference in tusks may be due to Dera Bugti Parac-eratherium specimens being largely female skulls, while the sole “Indri-cotherium” skull (Fig. 6.1) from Mongolia may come from a male individual. Inaddition, the new geologic dating of the Dera Bugti beds (Chapter 4) shows thatParaceratherium and “Indricotherium” are not earlier or later than one another,but contemporaries through most of the Oligocene.Granger and Gregory (1936, p. 3) noted how low and narrow the back of theskull was, lacking the huge crests across the top (lambdoid crests) and along themidline (sagittal crests) seen in other large animals like brontotheres and ele-phants. However, both of those mammals had large horns or tusks on the front ofthe skull, so they would have needed much stronger muscles to support the skullwhen using their tusks or horns to push or to fight.At the top of the back of the skull is a deep pit for the attachment of the nuchalligament, the thick strong ligament that attaches to the neck vertebrae and holdsthe skull up automatically against the pull of gravity. To make the head benddown, the neck muscles must pull against this “rubber band” ligament that worksto hold the skull up without extra muscle action. When land vertebrates die, thisligament tends to contract and pull the neck backwards in a curve, a characteristicpose for many dead animals and fossil skeletons as well.Even though the back of the skull is low and narrow, Granger and GregoryFigure 6.2. Reconstruction of the muscles of the head of Juxia. (After Qiu and Wang, 2007; usedwith permission.)...
Download PDF (377.5 KB)
Paradise LostGreenhouse of the DinosaursFifty-five million years ago (the earliest Eocene Epoch), the planet was in itswarmest phase since the “greenhouse of the dinosaurs” during the latter part ofthe Mesozoic (Prothero, 2009). There were crocodiles in the polar regions, alongwith a wide variety of mammals (including the earliest rhinocerotoid Hyrachyus).The fossil plants found above the Arctic and Antarctic Circles look nothing likethe Arctic tundra or Antarctic ice caps that are found there today, even thoughthey must have experienced six months of darkness. Instead, during the EoceneEpoch there were broad-leaved evergreens, including palm trees and cycads,above 61º north latitude in Alaska, indicating average temperatures around 18ºC(65ºF). There were broad-leaved deciduous forests and even rich coal beds, indi-cating dense forest vegetation. Spitzbergen produced a flora that could not havetolerated freezing. Ellesmere Island in the Canadian Arctic, which today lies at78º north latitude and was not far from that latitude in the early Eocene, producedsimilar fossil plants. It also yields fossil alligators, pond turtles, land tortoises,and monitor lizards, as well as garfish and bowfin fish. Most of these animals aretypical of subtropical climates today, and none can tolerate freezing for long. Al-ligators are limited by a mean coldest month temperature of 10ºC. There is alsoa surprisingly diverse fauna of mammals typical of the late early Eocene in NorthAmerica, including tapirs, horses, brontotheres, primates, rodents, colugos, andrhinos.In the high latitudes of the Southern Hemisphere, the story was the same. InAustralia there was a subtropical-temperate forest dominated by typical SouthernHemisphere conifers, such as Araucaria, which included the Norfolk Island pineand “monkey puzzle tree,” and podocarps, along with flowering plants such asthe Proteaceae (including the familiar flowering shrub Banksia) and laurels. Inthe swampy areas, Nypa palms and tree ferns were common and coals formed.According to Greenwood et al. (2003), the mean annual temperature for this re-gion was 16–22ºC (up to 72ºF), with the coldest mean temperature no lower than10ºC (50ºF), and a mean annual precipitation of more than 150 cm per year.How could the polar regions be so balmy, even though they experienced sixmonths of darkness? When the evidence from Ellesmere Island and other polarlocalities was first discovered in the 1980s, paleoclimatologists struggled for ananswer to this. Paleomagnetic pole positions for Eocene rocks of the high Arcticshow that they have not drifted significantly northward since they formed; so wecan rule that possibility out (McKenna, 1980, 1983). Ellesmere Island, for exam-ple, was at 75º north latitude in the Eocene, not significantly different from itspresent latitude. Creber and Chaloner (1984) re-examined the botanical evidencecited by Wolfe (1980) and concluded that even with six months of darkness, thepolar regions received sufficient sunlight for a seasonally productive forest. Themain limiting factor was temperature. As long as it did not get too cold, the forestscould grow during the “midnight sun” summers and remain dormant during thesix months of darkness. The modern dominance of tundra vegetation in the Arcticis dictated by the cold, dry conditions, not by the six months of darkness. As Idiscussed in my book Greenhouse of the Dinosaurs (2009), all the evidence nowshows that the carbon dioxide levels of the early Eocene were nearly as high asthose of the Cretaceous (perhaps 1000–2000 ppm, compared to about 300 ppmtoday). It was a true “greenhouse planet.”Similar warm and wet subtropical to temperate conditions could be found inregions that are now buried under snow each winter. Fossil plants in Wyoming,North Dakota, and Montana demonstrate that conditions warmed to mean annualtemperatures as high as 21ºC (70ºF), and even the mean annual cold month tem-perature could be no lower than 13ºC (55ºF), because most of the plants are in-tolerant of freezing. These plants also suggest that the climate was very wet, withmean annual rainfall in excess of 150 cm (60 inches). By contrast, western NorthDakota today has a steppe climate. The mean annual temperature is only 5ºC(41ºF), and the spread between daily extremes ranges over 33ºC (over 90ºF). InNorth Dakota or eastern Montana, it is not at all unusual for the temperatures ona hot spring or fall day to start out above 32ºC (90ºF), then drop below freezingin a matter of hours as an Arctic cold front moves in.From the evidence of floras in the Bighorn Basin of Wyoming or the WillistonBasin of Montana and North Dakota, we can visualize a dense tropical forestmuch like that found in modern Panama. Tall trees formed a dense canopy, withvines and lianas growing all around them. The fossil plants include many thetropical groups, including citrus, avocado, cashews, and paw paw trees. Many ofthese plant genera are found today only in the jungles of southeast Asia or tropicalCentral America. In addition to the direct evidence of the plant fossils, there isinformation in the striking color bands that stripe the badlands slopes. Each bandrepresents an ancient soil horizon, and in many places there are hundreds of themstacked on top of each other, representing millions of years of the early Eocene.Each represents another episode of floodplain mud deposition, followed by thedevelopment of plants and a soil horizon, and then another episode of flooding,which buried the old soil. According to Tom Bown and Mary Kraus (1981, 1987),these ancient soils were deposited on broad floodplains bordering meanderingrivers, much like those of the modern Amazon.The same pattern can be seen in other temperate and tropical regions through-out the early Eocene. Even the Pacific Northwest and southern Alaska were rel-atively warm (25ºC) and wet, blanketed with broad-leaved evergreen forests, withabundant vines and lianas, and many plants of tropical Asian affinities.From the London Clay found in the basements of London comes an importantearly Eocene flora. As we saw in Montana, there are mostly tropical trees andshrubs, lianas, including cinnamon, figs, magnolias, palms, laurels, citrus, pawpaw, cashews, laurels, and vines such as moonseed, icacina, and grapes. Collinson(1983) and Collinson and Hooker (1987) showed that 92 percent of these plantshave living relatives in the jungles of southeast Asia. Fringing the coasts of thetropical jungles were mangrove swamps full of Nypa palms, also restricted tosoutheast Asia today. From this evidence, the average temperatures in Londonwere about 25ºC (77ºF) compared to the modern average of 10ºC (50ºF). Insteadof the cold, foggy London of Sherlock Holmes, London was as warm and tropicalas Singapore.Anywhere we find fossil floras of early Eocene age in temperate or tropicalregions around the world, we encounter a similar story. Floras from China (Guo,1985), Siberia (Budantsev, 1992), India (Mehrotra, 2003), and southern SouthAmerica (Romero, 1986) all show the same tropical-subtropical patterns, eventhough many of these regions were at fairly high latitudes and inland locations.Naturally, the few floras known from tropical regions, such as Panama, show thatconditions were hot and wet there in the early Eocene, as they are today (Graham,1999).The Big ChillContrast these conditions in the early Eocene with those of the early Oligocene(about 33 Ma), the world of the indricotheres in Asia. The White River Grouprocks of the Big Badlands of South Dakota preserve quite a bit of detail aboutthe history of many kinds of organisms. Retallack (1983) studied the color bandsvisible in the Badlands sections and found that they were paleosols, or ancientsoil horizons. Those from the upper Eocene Chadron Formation were formedunder forests with closed canopies of large trees (the huge root casts are particu-larly conspicuous) with between 500–900 mm (20–35 inches) of rainfall per year.In the overlying lower Oligocene (Orellan) Brule Formation, the paleosols indi-cate more open, dry woodland with only 500 mm (20 inches) of rainfall per year.Emmett Evanoff studied the sediments of eastern Wyoming (Evanoff et al., 1992)and found that the moist Chadronian floodplain deposits abruptly shifted to drier,wind-blown deposits by the Orellan. In the same beds are climate-sensitive landsnails. According to Evanoff et al. (1992), Chadronian land snails are large-shelled taxa similar to those found in wet subtropical regions, like modern CentralAmerica. Based on modern analogues, these snail fossil indicate a mean annualtemperature of 16.5ºC (63ºF) and a mean annual precipitation of about 450 mm(18 inches), very similar to the results obtained by Retallack (1983) for neigh-boring South Dakota. By contrast, Orellan land snails are drought-tolerant, small-shelled taxa indicative of warm-temperate open woodlands with a pronounceddry season. Their living analogues are found today in Baja, California.The amphibians and reptiles suggest similar trends of cooling and drying inthe early Oligocene (Hutchison, 1982, 1992). The Eocene is dominated by aquaticspecies (especially salamanders, pond turtles, and crocodilians) that had beensteadily declining in the middle and late Eocene. Crocodiles were gone by theChadronian, but there are a few fossil alligators that have been recovered fromthe Chadron Formation. By the Oligocene, only land tortoises are common, in-dicating a pronounced drying trend. In fact, these tortoises (Stylemys nebrasken-sis) are so common in the Orellan that these beds were originally called the“turtle-oreodon beds” after their two most common vertebrate fossils.Land plants are not well-preserved in the highly oxidized beds of the BigBadlands (except for the durable hackberry seeds, which are calcified while theyare alive), so we must look to other regions to understand the floral change. Therest of North American floras show a clear trend. Based on leaf-margin analysis,Wolfe (1971, 1978, 1985, 1992) suggested that mean annual temperatures inNorth America cooled about 8–12ºC (13–23ºF) in less than a million years. Thisis by far the most dramatic cooling event of the entire North American floralrecord and was the original basis for the phrase “Terminal Eocene Event” (eventhough revised dating now places it in the early Oligocene). Perhaps Wolfe’s(1971) earlier phrase “Oligocene deterioration” would be a better term.The problem with the earlier analyses published by Wolfe (1971, 1978) wasdue to confusion about dating. Most of these geochronological problems havenow been cleared up (Wolfe, 1992; Myers, 2003), but further refinement of datingis always valuable to test previous hypotheses. The Rocky Mountains of centralColorado yield several important floras that span the Eocene-Oligocene transition.The floras of the famous late Eocene Florissant Formation (Evanoff et al., 2001;Prothero and Sanchez, 2004) are dated at 34.07 ± 0.10 Ma. This Florissant florarecords the final phase of late Eocene warmth in the North American floral cli-matic curve of Wolfe (1978) before the early Oligocene deterioration. Eventhough it was at 2000–3000 m elevation in the Eocene, the Florissant flora is be-lieved to represent warm-temperate climatic conditions of moderate rainfall anda mean annual temperature of 13–14ºC (Meyer, 2003), compared to modern meanannual temperatures of 4ºC. Slightly younger than Florissant is the late EoceneAntero flora. Durden (1966) reported a flora that was not too different from thatof Florissant. As Prothero (2008) demonstrated, there is then a gradual cooling...
Download PDF (87.8 KB)
Download PDF (47.1 KB)
Download PDF (13.0 KB)
DONALD R. PROTHERO has taught college geology and paleontology for 33years at institutions including the California Institute of Technology and Co-lumbia, Pierce, Occidental, Knox, and Vassar Colleges. He is the author ofmore that 35 books (including five geology textbooks) and over 250 scientificpapers. He is a Fellow of the Geological Society of America, the Paleontologi-cal Society, the Linnean Society of London, and in 1988 he was a GuggenheimFellow. In 1991, he received the Charles Schuchert Award of the Paleontologi-cal Society for the outstanding paleontologist under the age of 40....
Page Count: 160
Publication Year: 2013
Series Title: Life of the Past