Tendaguru! It is a name that carries with it a sort of magic in the story of the search for dinosaurs. It is a name to be linked with two other names that epitomize the excitement and the romance of the hunt of giant dinosaurs—Como Bluff and Dinosaur Monument. For at Tendaguru there were found, in almost overwhelming abundance, the bones of gigantic Jurassic dinosaurs, some of them the same as the dinosaurs excavated at Como Bluff and Dinosaur Monument…. Tendaguru is a record of an extension south of the equator of the same dinosaurian life that had dominated the Northern Hemisphere during the final years of Jurassic history.
—EDWIN COLBERT, MEN AND DINOSAURS
Mention Tendaguru to dinosaur enthusiasts and their eyes are likely to sparkle.
—DAVID SPAULDING, DINOSAUR HUNTERS
OUT OF AFRICA
In the late 1800s, the major powers of Europe stampeded in a land grab to colonize the “backward” regions of Africa. Some people went to Africa because they felt they must be missionaries to the heathens, others because they thought Africa should be “civilized” like Europe, and others because Africa offered enormous riches and potential for wealth and power. A few countries, such as South Africa, had been colonized much earlier by the British and by the Dutch (whose descendants are known as the Boers) because South Africa was crucial to ships traveling around the continent and also wealthy in gold and diamonds and other resources. But much of Africa remained unclaimed by the large European powers and was under the rule of local chieftains and sultans.
Much of eastern and southern Africa was taken by the British, western Africa was largely under French or Spanish dominion, and the Congo was ruled by Belgium. Germany came very late to this imperialistic frenzy because it had neither the strength nor the leadership to become a colonial empire until the 1870s when Otto von Bismarck consolidated all the small independent kingdoms into one country. By the 1880s, however, Germany was jostling with the other European empires to get their share. They sent five warships to point their guns on the palace of the Sultan of Zanzibar, who was forced to surrender most of what became Tanzania to them. Southwestern Africa (now Namibia) was also a German colony, as was Rwanda in central Africa, plus Cameroon, Togoland, and a few other parts of western Africa.
Most of the early German colonials were soldiers, hunters, missionaries, government officials, and people exploiting the mineral wealth or ivory market. There were even slave traders as the Germans didn’t abolish slave trading in their colonies, although they tried to check its spread. The German colonial empire thrived until they lost World War I in 1918. After the war, they were forced to give up all of their territories as part of the Treaty of Versailles, and other countries (mainly Great Britain) snapped them up.
Germany was one the world’s leaders in science and technology in the late 1800s and early 1900s. Their archeologists were at the top of the profession, with Karl Richard Lepsius pioneering modern Egyptology, Heinrich Schliemann finding the ruins of Troy in 1873 and also ancient Mycenae in Greece, and many other major expeditions. The Pergamon Museum in Berlin is filled with some of the best artifacts from Egypt, Babylonia, and Assyria, and many ancient Greek treasures.
Germany’s natural historians were equally significant, dating back to the late 1700s when geology and paleontology began with Alexander von Humboldt (1769–1859), Abraham Gottlob Werner (1749–1817), Leopold von Buch (1774–1583), and extending into the 1800s with paleontologists Christian Erich Hermann von Meyer (1801–1869) and Karl Alfred von Zittel (1839–1904), and pioneering embryologists such as Karl Ernst von Baer (1792–1876) and Ernst Haeckel (1834–1919). Both Cope and Marsh spent years learning paleontology in Germany in the 1860s, as did Henry Fairfield Osborn and William Berryman Scott in the 1880s. These Americans listened to lectures by the giants of the field, studied fossil collections, and received the equivalent of a Ph.D.-level education (that degree was not yet offered in the United States).
By the early twentieth century, German dinosaur paleontology was led by Friedrich von Huene (see chapter 6), Erich von Reichenbach Stromer (see chapter 13), and Werner Ernst Martin Janensch (figure 9.1). Born in 1878, Janensch was the fossil reptile specialist at the Museum für Naturkunde in Berlin in 1901. As his fame grew, he received the Leibniz Medal from the Prussian Academy of Sciences in 1911, appointment to the professorship at the Friedrich-Wilhelms-Universität in 1913, and was a founding member of the Paläontologische Gesellschaft in 1913. His most famous accomplishment, however, was to lead a great expedition to Africa.
Figure 9.1
Werner Janensch with African workers and a giant dinosaur leg bone. (Courtesy of Wikimedia Commons)
In 1906, a German pharmacist, chemist, and mining engineer, Bernhard Wilhelm Sattler, was on his way down a path to a mine south of the Mbemkure River in German East Africa (now Tanzania) and banged his shin on some enormous bones weathering out of the path near the base of the hill. The hill was called tendaguru (steep hill) in the local Wamwera language. Sattler reported the news to German paleontologist Eberhard Fraas, who happened to be visiting nearby, and together they excavated two gigantic skeletons. They shipped the skeletons to the Royal Natural History Collection in Stuttgart where Fraas was a curator, and they were described as Gigantosaurus robustus and Gigantosaurus africanus in 1908. Unfortunately for Fraas, the name “Gigantosaurus” had already been used by British paleontologist Harry Gover Seeley in 1869 to name some fragmentary dinosaur bones from England (whose correct genus cannot be determined today). So the name “Gigantosaurus” was invalid, not diagnostic, and could not be used. Today Fraas’s dinosaurs have been renamed Janenschia robusta and Tornieria africana. Fraas contracted dysentery while he was in Africa, which made him sickly and killed him in 1915.
Other German scientists were impressed with Fraas’s finds and were told that there was much more to be obtained there. The director of the Berlin Museum, Dr. Wilhelm von Branca, was desperate to send another field expedition to obtain bones for his museum. He formed a committee with the Duke Mecklenberg, Regent of Brunswick, and together they raised money from the German Imperial Government, the City of Berlin, the Academy of Learning, and hundreds of private citizens. Altogether they raised about 230,000 marks, or about US$50,000, a considerable sum for 1909.
Once the funds were obtained, Janensch was appointed to lead the expedition as the curator of fossil reptiles for the Berlin Museum. His second in command was Edward Henning of the museum. In 1909, the expedition reached Tendaguru and transformed the quiet little area of forest into a busy village. Hundreds of Africans (170 in the first year, and 500 by the third year) were doing all the heavy manual labor, digging the holes, and carrying the gigantic bones out. All these hard-working Africans came with their families, so a small village of huts sprang up filled with women and children. Because domestic animals would require constant protection against predators such as lions, most of the food had to be brought in from the seaport of Lindi, a four-day march. Photographs of the expedition show long caravans of people carrying enormous loads on their heads to bring supplies from Lindi to Tendaguru (figure 9.2). On the return trip, the men carried the immense bones covered in plaster jackets and suspended between poles. Often as many as four of them were required to carry just one fossil. In just the first three years, thousands of loads of bones were carried out in 5,400 trips, packed in 800 boxes in Lindi, that weighed over 180,000 kilograms (400,000 pounds) or about 180 metric tonnes (200 tons).
Figure 9.2
Images of African workers: (A) excavating huge dinosaurs; (B–C) carrying loads between Lindi and Tendaguru. (Courtesy of Wikimedia Commons)
The excavations continued throughout 1910 and 1911, forcing the crews to dig larger and larger pits and to shore up the sides with wooden walls. Most of the specimens were not only huge and heavy but also broken, and most were scattered around rather than being found as partial skeletons such as the finds in the American Rockies. One shoulder blade, for example, was 1.8 meters (6 feet) long but broken into 80 pieces and required 160 hours to clean, piece together, and harden. A single vertebra might consume 450 hours of labor to prepare. Henning wrote:
The remains of our giants, that is the bones of the legs, vertebrae, and the teeth, were almost without exception strewn around confusedly in the embedding rock. Whenever we thought we were gradually assembling parts of an animal, some saurian goblin would play us a trick: three like thighbones, two pelvises, or something of the sort would almost always suggest the presence of the same species on one spot—but for ever so long the skull, which we particularly wanted, would not turn up. Gradually however, the legendary creature beginning to arise from the graves became stranger and stranger; they kept us constantly in suspense. Thus several elements of legs appeared, and before we could properly free the joints they looked like strong femurs. After days of widening the shaft, a considerably larger piece would be added, and then it would turn out that what we had been dealing with was only the metacarpal bone. Quite a glove those hands would have worn! These bones would now be joined by the tibia. Then after a while the humerus belonging to the same animal would turn up.
After three years (1909–1911), most of the German scientists—Janensch, Henning, and the others—returned to Berlin to begin work on the fossils. They put 26-year-old Hans Reck in charge of the excavation, and he spent 1912 recovering another 45 metric tonnes (50 tons) of bones. Reck would later become famous as the first to find human fossils at Olduvai Gorge. By this time, the excavations spanned a strip over 5.6 kilometers (3.5 miles) long in the north-south direction, and 2.4 kilometers (1.5 miles) wide in the east-west axis. There were 50 separate excavations with sauropod bones and at least 13 with stegosaur fossils. The expeditions formally ended after 1912; war broke out only two years later, making any further work impossible—especially after German East Africa became British Tanganyika in 1919.
In Berlin, however, Janensch and the others were busy writing up the immense reports on the fossils, which were published in a variety of journals over the next decade. They noted that the fossils had been found interbedded with marine beds full of shells. One skeleton was found with marine fossils that had washed inside it. In other places, the huge sauropods were found with their limbs buried upright, as if trapped in water-logged sediment, while the rest of their bones were scattered nearby, probably after having been torn apart by scavengers or washed away as they rotted. Most of the dinosaurs appeared to have been trapped on sand bars and river mouths near the ocean, where they sank into river sediments after they died, then were covered by the next flood of sediments from the river, or by occasional rises in sea level drowning the coastline.
The Tendaguru fauna that lived along this African shoreline during the Jurassic was remarkable. In addition to the gigantic brachiosaur Giraffatitan (figure 9.3A) discussed in the next section, there was also a diplodocoid called Dicraeosaurus (figure 9.3B), just about half the size of Diplodocus. It had an extremely long tail and a relatively short neck, reaching 13 meters (43 feet) in length and weighing about 5.9 metric tonnes (6.5 tons). Another specimen originally called “Gigantosaurus,” but renamed Tornieria in 1911, was also a diplodocoid.
Figure 9.3
Sauropods from Tendaguru in the Museum für Naturkunde, Berlin: (A) current mount of the Giraffatitan; (B) the small diplodocine Dicraeosaurus, dwarfed by Giraffatitan next to it. (Courtesy of M. Wedel)
The Tendaguru stegosaur known as Kentrosaurus had two rows of spikes along its back and only a few smaller plates, but otherwise it was closely related to the American Stegosaurus (see chapter 20). There were also spikes sticking out from the hips (or possibly the shoulder) and from the end of the tail. Kentrosaurus reached about 4.9 meters (16 feet) in length and was about 25 percent smaller than Stegosaurus. One locality produced the disarticulated remains of about 50 individuals in a pit that was 15–18 meters (50–60 feet) deep and over 915 meters (3,000 feet) across. Another find, described by Rudolf Virchow in 1919, was Dysalotosaurus, a small ornithischian dinosaur closely related to American Dryosaurus.
These herbivores were preyed upon by numerous typical Late Jurassic predators, including animals similar to Allosaurus and possibly Ceratosaurus (both known from the Morrison Formation in the Rockies). There was also a small relative of Ceratosaurus called Elaphrosaurus. A number of other theropod dinosaur groups are represented by fragmentary remains that cannot be assigned to a genus.
Finally, there were several fragments of pterosaurs that resembled Pterodactylus and Rhamphorhynchus from the Upper Jurassic Solnhofen Formation of Bavaria, and crocodilians, turtles, and even a toothless jaw of a very primitive mammal (one of the earliest known) called Brancatherulum.
Many scientists noted how similar most of the Tendaguru fossils were to dinosaur beds of the same age from America’s Morrison Formation: allosaurs, stegosaurs, and dryosaurs, but especially the huge sauropods including diplodocoids and brachiosaurs. For a long time, they were puzzled by how such similar dinosaurs could have traversed the Atlantic Ocean to travel between East Africa and Wyoming. They even postulated land bridges across Antarctica. But the answer to the puzzle became clear when plate tectonics came along in the late 1960s. Although these localities were thousands of miles away from one another, they were still on the supercontinent of Pangea in the Late Jurassic, which was just beginning to break up. Most of the Jurassic faunas elsewhere in the world, whether in the Northern or Southern Hemisphere, look very similar, with only some small regional differences.
Like many other famous German fossils (see chapter 20), some of the huge Tendaguru bones were destroyed by Allied bombers in World War II. Fortunately, the spectacular mounted brachiosaur skeleton has survived, as have many other specimens scattered in other museums (although some in other German museums were also destroyed by bombing). There are also replicas of the German specimens in many other museums around the world. In addition, the British recovered specimens when they reopened the Tendaguru quarries when Tanganyika became a British colony after World War I—although most of those bones have still not been formally described or published.
THE “ARM LIZARD”
The most spectacular and abundantly preserved of Tendaguru dinosaurs were the enormous brachiosaurs, which were the largest dinosaurs known in the world for most of the twentieth century (recently surpassed by Argentinian titanosaurs; see chapter 10). The African fossils were immediately compared to an American genus, Brachiosaurus, “arm lizard,” so-called because they had unusually long arms and short hind legs that raised their shoulders high and elevated their heads (already at the end of long necks). Brachiosaurs are now famous thanks to their appearance as “veggie-saurs” in the first Jurassic Park movie, being featured in the TV show Walking with Dinosaurs, and through numerous mounted replica skeletons found in many museums.
However, the original Brachiosaurus specimen was much less impressive. It was named and described by Elmer Riggs of the Field Columbian Museum (now the Field Museum of Natural History) in Chicago when he was working in the Morrison Formation in what is now Fruita, Colorado. In 1899, S. M. Bradbury, a local dentist, wrote to tell Riggs of dinosaur bones (figure 9.4A) near Grand Junction, Colorado, which brought out the Field Museum scientists. The original Brachiosaurus specimens were found by Riggs’s field assistant, H. W. Menke, on the Fourth of July, 1900, when prospecting around a hill that became Riggs Quarry 13 (there is now a monument at the spot). The specimen was only 20 percent complete, consisting of a right humerus (upper arm bone), right femur (thighbone), ilium (upper part of the pelvis), coracoid (shoulder bone), sacrum (fused vertebrae of the hip), seven trunk vertebrae, two tail vertebrae, and some ribs, but the enormous vertebrae gave an indication that it was larger than any sauropod then known. Even though the rest of the dinosaur was missing, Riggs could tell that it had long forelimbs, high shoulders, and short hind limbs. He published the original description in 1903, naming it Brachiosaurus altithorax (Greek for “tall chest,” in recognition of the tall chest cavity suggested by the bones), and published a more detailed description in 1904.
Figure 9.4
Brachiosaurus altithorax: (A) the bones under excavation near Grand Junction, Colorado; (B) the replica now on display in United Airlines Concourse B at O’Hare Airport in Chicago. (Courtesy of Wikimedia Commons)
Because the skeleton was so incomplete, in 1908 the specimens were displayed as isolated bones in glass cases by the side of the old dinosaur exhibit hall of the Field Museum. Today only the long humerus (upper arm bone) and two dorsal vertebrae are on display in the “Evolving Planet” exhibit. The center of the hallway is occupied by the complete skeleton of Apatosaurus found on a different Field Museum expedition. This was the state of affairs until Janensch described the nearly complete brachiosaur from the Tendaguru. Janensch decided that the African material was also referable to Riggs’s genus Brachiosaurus, but he gave it a different species name, Brachiosaurus brancai, in honor of Dr. Wilhelm von Branca, the head of the Berlin Museum who had made the expedition possible. Now nearly every reconstruction of Brachiosaurus is based on the African fossils on display in Berlin; the original American Brachiosaurus material is too incomplete to create a reconstruction or skeletal mount. In 1994, the Field Museum made molds and fiberglass casts of their own bones, then obtained copies of the African specimens, and created a composite reconstruction of Brachiosaurus. This impressive replica towered above the visitors at the north end of Stanley Field Hall, the high-ceilinged main room in the Field Museum, from 1994 until it was removed in 1999 to make way for the famous Tyrannosaurus rex specimen nicknamed “Sue.” It was moved to the B Concourse of United Terminal 1 at O’Hare Airport (figure 9.4B). Ironically, Sue has since been moved to make way for an even bigger sauropod, the Patagotitan skeleton from Argentina (see chapter 10). A second copy of the Brachiosaurus skeleton was made and placed outside the northwest terrace of the museum.
Janensch himself was not entirely sure that his African specimens were really referable to North American Brachiosaurus. In a series of papers from 1929 to 1950 to 1961, he listed what he thought were 13 unique anatomical features the two dinosaurs had in common. Only four are considered significant now, and the rest are shared with other brachiosaurs, other sauropods, or are difficult to assess as the Colorado specimen consists of only a few bones. The huge skeleton on display in Berlin is also incomplete (see figure 9.3A) and made of a composite of at least two or three different individuals, most of them juveniles. The differences between the two dinosaurs bothered Janensch and several other paleontologists for many years. In 1988, dinosaur artist Greg Paul published the name Giraffatitan as a subgenus (without detailed justification). The African brachiosaur was called Brachiosaurus (Giraffatitan) brancai. In 1994, amateur paleontologist George Olshevsky raised Giraffatitan to the level of genus, again without justification. Most scientists ignored these poorly supported name changes made by amateurs as unjustified. However, a computer programmer and amateur sauropod enthusiast, Mike Taylor, did a rigorous study in 2009 and found evidence that the African fossils were indeed a different genus than the Colorado fossils, and he argued that Giraffatitan is valid. Since then, the name has come to be accepted by most paleontologists.
Since the discovery of Giraffatitan, more and more huge sauropod bones have been found, especially by the late “Dinosaur Jim” Jensen of Brigham Young University. One of his best localities is near Grand Junction, Colorado, and the Colorado National Monument. Known as Dry Mesa Quarry, it has yielded some of the largest bones ever found in the United States (figure 9.5). (I knew Jim well, and he once loaned me the tiny arm bone of a shrew-sized Jurassic mammal from Dry Mesa Quarry to describe, which I coauthored with him and published in 1983.) Some of these bones belonged to a huge sauropod found in 1972 but mentioned in the media numerous times before Jensen formally named it Supersaurus vivianae in 1985. Even though a lot of bones are known (possibly 30 percent of the skeleton), the most diagnostic fossils suggest that it is a diplodocine slightly larger than the largest Apatosaurus.
Figure 9.5
Jim Jensen lying next to the shoulder blade of Supersaurus as it was found in Dry Mesa Quarry. (Courtesy of Wikimedia Commons)
In addition to Supersaurus bones found in Dry Mesa Quarry, additional large fossils found there were named Ultrasaurus by Jensen in the same 1985 paper. However, this created a huge problem. First, the name Ultrasaurus had already been used by Kim Han Mook in 1983 for a completely different Korean dinosaur, so when Jensen finally published the name (after using it informally in the press for years), it was not available. To get around this, Jensen emended the name to Ultrasauros (with an “o” instead of a “u” before the final “s,” using the Greek rather than Latin spelling of sauros, “lizard”). However, there were still problems. The specimen on which the name Ultrasauros is based (the “type specimen”) turned out to be a backbone vertebra of a Supersaurus, so the name Ultrasauros is probably a junior synonym of Supersaurus.
However, there are bones in the Dry Mesa Quarry that belonged to an even larger dinosaur, including a scapulocoracoid (shoulder blade and shoulder girdle) that come not from a diplodocine but from a brachiosaur slightly larger than Giraffatitan. This is the specimen that most people mean when they say Ultrasauros now, although that name is still not available. If that were not messy enough, Jensen found another backbone vertebra in a nearby quarry that he called Dystylosaurus edwini. Most sauropod specialists think that this is just an additional specimen of Supersaurus vivianae.
Jensen further compounded the confusion by not only releasing his names to the press without naming them properly in the scientific journals but also by telling the press that this composite (called a “chimera”) of a brachiosaur and a diplodocine was an incredibly large sauropod, reaching 30 meters (100 feet) long, 8 meters (25 feet) tall at the shoulder and 15 meters (50 feet) in total height, and weighing 70 metric tonnes (77 tons; estimates has it as large as 150 tonnes/165 tons). Such a huge dinosaur did not exist, and the actual bones show that it is a mix of a large diplodocine plus a very large brachiosaur, not a real animal.
To summarize this complex story, despite all the publicity and multiple names, many of Jensen’s Dry Mesa specimens belong to the diplodocine Supersaurus. There are Apatosaurus and Camarasaurus as well, with Diplodocus being the most common dinosaur at Dry Mesa. But one shoulder girdle belongs to a very large brachiosaur, larger than any known so far, which could be considered just a large Brachiosaurus or maybe Giraffatitan. Whatever it is, it cannot be called Ultrasaurus OR Ultrasauros.
Riggs realized that his original Brachiosaurus has long forelimbs but short hind limbs, suggesting high shoulders and a sloping back. But none of his discoveries gave him any indication of the skull or neck of that animal. Not until Janensch described and mounted a display based on the multiple partial skeletons of Giraffatitan from Tendaguru did we get a clear picture of what this animal looked like, how long it was, and how heavy it might have been. When it was finally mounted and displayed in Berlin, it became the largest dinosaur known from a nearly complete skeleton and remained so until fairly recently when the Argentinian titanosaurs surpassed it as the largest land animal that ever lived (see chapter 10).
Some of the early ideas about brachiosaurs were remarkably naïve and even ridiculous. In the early twentieth century, most dinosaur paleontologists viewed sauropods and many other dinosaurs as slow, sluggish lizards living in swamps, needing the buoyancy of water to support their enormous bulk. According to this outdated notion, many dinosaurs dragged their tails and were barely able to walk, let alone keep their bellies from dragging on the ground. Janensch’s original mount of Giraffatitan had the legs mounted in a sprawling lizard-like posture with its limbs flexed and bowed out sideways instead of with its limbs in the upright vertical posture that we now know they must have had. (The current skeletal mount has corrected this mistake.)
Other paleontologists imagined that the long neck of sauropods was used like a snorkel, allowing them to submerge their bodies and only have their heads above water. Some even put the nostrils on top of their heads to allow them to be almost completely immersed. We now know that the nostrils faced forward, not upward. A famous old painting by the Czech paleoartist Zdenek Burian shows a brachiosaur walking in a deep fjord completely under water except for its head (figure 9.6). This notion is absurd. Any animal this deep below the surface would be subjected to so much water pressure on its body that it could not expand its lungs. Brachiosaurs had no special mechanism for pulling air from the surface down their windpipes against so much hydraulic pressure on the lungs and body. Under so much force, their lungs would have collapsed. In contrast, whales can live deep underwater because they have unique anatomical specializations that enable them to control the air in their lungs under huge pressures. In addition, whales only inhale at the surface, then dive.
Figure 9.6
An early reconstruction of a brachiosaur by artist Zdenek Burian, which imagines the long neck was like a snorkel for living deep in the water. This is biologically impossible because the pressure of water at that depth would have collapsed their lungs. (Courtesy of Wikimedia Commons)
This is not the only absurdity of snorkeling brachiosaurs. We now know that nearly all dinosaurs (and birds) have numerous air sacs in their bodies (especially around the backbone), which lighten their weight considerably. This helps decrease the amount of weight they must carry on their limbs (and eliminates the need for them to float in water much), but it would also make them very buoyant and prohibit them from diving into a deep fjord as the old Burian painting suggested.
During the 1970s and 1980s, our view of dinosaurs underwent a huge change, often called the “Dinosaur Renaissance.” The most controversial claim was that all dinosaurs had a physiology like that of birds and mammals: homeothermic (maintained constant body temperature) and endothermic (got their heat from metabolizing food rather than from the outside environment as most reptiles do). This was certainly true of the smaller dinosaurs, but there is still a lot of doubt that huge sauropods were endotherms because their enormous bulk and limited surface area would have made dumping excess body heat very difficult (see chapter 17 for a more detailed discussion). Instead, they are thought to have employed inertial homeothermy or “gigantothermy”: their huge body mass gained and lost heat very slowly without an internal heat source. Inertial homeothermy is a great strategy for living in the globally warm greenhouse climates of the Jurassic and Cretaceous when it never got very cold and snow and ice were virtually nonexistent.
The reexamination of dinosaurs during the 1970s pointed out some other major surprising things about them. The old “sluggish lizard” model could be ruled out because dinosaurs had vertical limbs tucked completely beneath their bodies (as birds and mammals do) and did not sprawl. Numerous track sites of sauropods showed almost no tail drag marks, so sauropods rarely dragged their tails; they held their tails almost straight out behind them, supported by a trusswork of tendons along the spine. And the “swamp” notion was ruled out because detailed sedimentary studies showed that the Morrison Formation (which has most of the American sauropods) was not a swampy environment but a savannah-like setting comparable to modern East Africa, with distinct wet and dry seasons, many tall coniferous forests, and very little standing water.
Most of the outdated notions of sauropods were ruled out by the 1980s, and fortunately the first Jurassic Park novel and movie did not illustrate these notions, so modern audiences did not learn about these old, outdated ideas regarding brachiosaurs. But the brachiosaurs did one thing in that movie that we think is impossible—rearing up on their hind legs to reach high branches. Brachiosaurs are so imbalanced and front-heavy that they may well have lost their balance or broken their legs if they reared up on their relatively small haunches; their hips and hind legs were not large enough to support their entire weight. In any case, brachiosaurs would gain very little advantage by rearing up because (like giraffes) they were naturally the tallest animals in their habitat. With their long vertical necks and the high front end of their body, they already enjoyed a height advantage over all the competing sauropods for treetop fodder.
Paleontologists have done numerous studies to estimate the feeding habits of brachiosaurs. They appear to have been specialists on the highest limbs of trees, which were nearly all conifers in the Late Jurassic. (Flowering plants had not yet evolved.) They could bring their necks down to ground level to feed on ferns and cycads (the only other common types of plants as there were no grasses or flowering shrubs and trees yet), but they would have a disadvantage compared to the shorter-necked animals that lived with them. Their simple, small, spoon-shaped teeth were sufficient only to strip branches and pine needles off intact, and they had no ability to chew their food. Their fodder was gulped down whole and must have been ground up in a large gizzard in their chest, then slowly fermented and digested in a huge intestinal tract that took up most of their body cavity. Paleontologists estimate that they needed about 180–240 kilograms (400–550 pounds) of fodder a day to feed their enormous appetites. That kind of intense browsing would have consumed a lot of conifer trees and ferns in relatively short order, so there could not have been large populations of them in any one area, nor was it likely that they coexisted with many other species of sauropods (see chapter 7). Brachiosaurus was also a relatively rare animal in the Morrison Formation, with only 12 specimens known, compared to 112 Apatosaurus, 179 Camarasaurus, and 98 Diplodocus. However, Giraffatitan specimens greatly outnumber the diplodocoid Dicraeosaurus and other sauropods in the Tendaguru beds.
The skulls of Brachiosaurus and Giraffatitan are quite different; this is one of the main reasons most people place them in different genera now (figure 9.7). Both had relatively short narrow snouts with arches of bone over the top of the head and eyes, but the arches in Giraffatitan were much higher. At one time paleontologists suggested that their nostrils were on top, like a snorkel, but now that is thought unlikely; instead, the high arches may have supported a resonating chamber for making sounds (as suggested in Jurassic Park). The brain had a volume of only about 300 cubic centimeters, large enough to control their bodies but very small relative to their enormous body mass, so these dinosaurs were not smart. They probably didn’t need to be smart because once partially grown they were too large to fear any predators. They must have had enormous hearts to create the blood pressure to pump all that blood uphill to their heads, and they probably had a series of valves in the veins of their neck (as giraffes do) to keep their blood rushing to their head when they bent down to drink, or rushing away from their brain and making them dizzy or passing out (as can happen to humans) when they raised their heads suddenly.
Figure 9.7
Comparison of the skulls of brachiosaurs: (A) the skull of Giraffatitan from Tendaguru; (B) the Brachiosaurus from Felch Quarry, Colorado. (Courtesy of Wikimedia Commons)
How big were these giants? Estimates vary tremendously because so many of the specimens are incomplete. The nearly complete skeleton of Giraffatitan in Berlin was about 22.5 meters (75 feet) long, and 12 meters (39 feet) tall. Its weight has been estimated as low as 15 metric tonnes (16.5 tons) to as high as 78 tonnes (86 tons), but most estimates now place the likely mass in the 20–40 tonne range (22–44 tons) because brachiosaurs were made much lighter by numerous air sacs throughout their bodies. This is not the limit for Giraffatitan because the mounted skeleton is not fully grown. There is another limb bone of an adult that is 13 percent larger, suggesting that their maximum adult dimensions were considerably larger.
For most of the twentieth century, brachiosaurs were considered the largest land animals that ever lived. But in the past 30 years, amazing discoveries from Argentina have produced even more enormous animals, the titanosaurs, which are discussed in chapter 10.
FOR FURTHER READING
Colbert, Edwin. Men and Dinosaurs: The Search in the Field and in the Laboratory. New York: Dutton, 1968.
Curry Rogers, Kristina, and Jeffrey Wilson. The Sauropods: Evolution and Biology. Berkeley: University of California Press, 2005.
Farlow, James, and M. K. Brett-Surman. The Complete Dinosaur. Bloomington: Indiana University Press, 1999.
Fastovsky, David, and David Weishampel. Dinosaurs: A Concise Natural History, 3rd ed. Cambridge: Cambridge University Press, 2016.
Hallett, Mark, and Mathew J. Wedel. The Sauropod Dinosaurs: Life in the Age of Giants. Baltimore, Md.: Johns Hopkins University Press, 2016.
Holtz, Thomas R., Jr. Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages. New York: Random House, 2011.
Klein, Nicole. Biology of the Sauropod Dinosaurs: Understanding the Life of Giants. Bloomington: Indiana University Press, 2011.
Maier, Gerhard. African Dinosaurs Unearthed: The Tendaguru Expeditions. Bloomington: Indiana University Press, 2003.
Naish, Darren. The Great Dinosaur Discoveries. Berkeley: University of California Press, 2009.
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