Brachiosaurus

*Brachiosaurus altithorax*

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**Brachiosaurus** was a sauropod that lived in the late Jurassic. *Brachiosaurus* had a proportionally long neck, small skull, and large overall size, all of which are typical for sauropods. However, the proportions of *Brachiosaurus* are unlike most sauropods. It was an extremely tall dinosaur and as a member of the brachiosaur group was one of few sauropods that could actually have their necks vertical. It also had very long front legs that give it its name, which means "arm lizard". Its tail was shorter compared to its body than most sauropod's, but it was still long and muscular and could be used to deliver a nasty lash to predators.

*Brachiosaurus* is the namesake genus of the family Brachiosauridae, which includes a handful of other similar sauropods. Much of what is known by laypeople about *Brachiosaurus* is in fact based on *Giraffatitan brancai*, a species of brachiosaurid dinosaur from the Tendaguru Formation of Tanzania that was originally described by German paleontologist Werner Janensch as a species of *Brachiosaurus*. Recent research shows that the differences between the type species of *Brachiosaurus* and the Tendaguru material are significant enough that the African material should be placed in a separate genus. Several other potential species of *Brachiosaurus* have been described from Africa and Europe, but none of them are thought to belong to *Brachiosaurus* at this time.

## Description

    Like all sauropod dinosaurs, *Brachiosaurus* was a quadrupedal animal with a small skull, a long neck, a large trunk with a high-ellipsoid cross section, a long, muscular tail and slender, columnar limbs. The skull had a strong, wide snout and thick jaw bones, with spoon–shaped teeth. As in *Giraffatitan*, there was an arch of bone over the snout and in front of the eyes that encircled the nasal opening, although this arch was not as large as in its relative. Large air sacs connected to the lung system were present in the neck and trunk, invading the vertebrae and ribs, greatly reducing the overall density. Unusually for a sauropod, the forelimbs were longer than the hind limbs. The upper arm bone was lightly built for its size, measuring (6.7 ft) in length in the type specimen. The thigh bone of the type specimen was only 6.7 ft long. Unlike other sauropods, *Brachiosaurus* appears to have been slightly sprawled at the shoulder joint, and the ribcage was unusually deep. This led to the trunk being inclined, with the front much higher than the hips, and the neck exiting the trunk at a steep angle. Overall, this shape resembles a giraffe more than any other living animal.

### Size

Since "Brachiosaurus" *brancai* (*Giraffatitan*) is known from much more complete remains than *B. altithorax*, most size estimates for *Brachiosaurus* are actually for the African form. Over the years, the mass of *B. altithorax* has been estimated between 30 and 50 tons. In the first and last cases, the authors also provided estimates for *Giraffatitan*, and found that genus to be somewhat lighter (31.5 metric tons for Paul [1988] and 23.3 metric tons for Taylor [2009]). The length of *Brachiosaurus* has been estimated at 85 ft.

## Classification

*Brachiosaurus* is the namesake genus of Brachiosauridae. Through the years some sauropods have been assigned to Brachiosauridae, such as *Astrodon*, *Bothriospondylus*, *Dinodocus*, *Pelorosaurus*, *Pleurocoelus*, and *Ultrasaurus*, but most of these are now viewed as dubious or of uncertain placement. A phylogenetic analysis of sauropods published in the description of *Abydosaurus* found that genus to form a clade with *Brachiosaurus* and *Giraffatitan* (included in *Brachiosaurus*). A more recent analysis focused on possible Asian brachiosaurid material found a clade including *Abydosaurus*, *Brachiosaurus*, *Cedarosaurus*, *Giraffatitan*, and *Paluxysaurus*, but not *Qiaowanlong*, the claimed Asian brachiosaurid. Related genera include *Lusotitan* and *Sauroposeidon*. Brachiosauridae is placed at the base of Titanosauriformes, a group of sauropods that also includes the titanosaurs.

According to the revised diagnosis by Taylor *Brachiosaurus altithorax* is diagnosed by a plethora of characters, many to be found on the back vertebrae. Among the characters playing it in the family Brachiosauridae are the upper arm bone being at least close to as long as the thigh bone), and a very flattened femur shaft (ratio ≥1.85).

### Species

#### *Brachiosaurus altithorax*

The holotype of both the genus *Brachiosaurus* and the species *B. altithorax*, consists of the right upper arm bone, the right thigh bone, the right hip bone, the right shoulder bone, the fused vertebrae of the hip, the last seven trunk and two tail vertebrae, and a number of ribs. Riggs described the coracoid as from the left side of the body,. Riggs described the shoulder bone as from the left side of the body, ur". Science 13 (327): 549–550. doi:10.1126/science.13.327.549-a. PMID 17801098.</ref> but restudy has shown it to be a right shoulder bone.

#### Other assigned species

* *"B." atalaiensis*: First described by de Lapparent and Zbyszewski, in 2003, it was placed in its own genus *Lusotitan* by Antunes and Mateus.
* *B." brancai*: Found in Africa by Janensch in the Tendaguru site  It includes, among other bones, several trunk vertebrae, both shoulder bones, both breastbones, both upper arm bones, both lower arm bones, a right hand, a partial left hand, both hip bones and the right thigh bone. A re-assessment of the relation between the African and American brachiosaur material shows that a separate generic name is warranted for the former, which means that it's now considered to belong to *Giraffatitan*.
* *"B." fraasi*: built by Janensch in 1914, but later synonymized with *"B." brancai*; this material now belongs to *Giraffatitan*.
* *"B." nougaredi*: This species is known from incomplete remains found in the Sahara. de Lapparent, who described and named the material in 1960, said it lived in the Late Jurassic  but more recent review assigns it to the early Cretaceous. Upchurch, Barrett and Dodson (2004) doubted its assignment to Brachiosaurus, and listed it as an unnamed brachiosaurid. The hip vertebrae is of notable size, with a length of 51 in for four vertebrae compared to 37 in for five vertebrae in *B. altithorax*.

### Separation from Giraffatitan

When describing the brachiosaurid material from Tendaguru in 1914, Janensch listed several differences and similarities between them and *B. altithorax*. In three more publications in 1929, 1950
 and 1961 Janensch compared the two species in more detail, listing 13 supposed shared characters. Of these, however, only four appear to be valid, while six pertain to more inclusive groups than Brachiosauridae, and the rest are either hard to judge or refer to material that is not *Brachiosaurus*.

In 1988, Gregory Paul published a new rebuilding of the skeleton of "B." brancai, pointing out several differences in proportion between it and B. altithorax. Chief among them is a difference in the way the trunk vertebrae vary: they are quite uniform in B. altithorax but vary widely in the African material. Paul thought that the limb and girdle elements of both species were very similar, and so he suggested to separate them not at genus, but only at subgenus level.

*Giraffatitan* was raised to genus level by Olshevsky without comment. A detailed study of all material, including the limb and girdle bones, by Michael Taylor in 2009 found that there are significant differences between *Brachiosaurus altithorax* and the Tendaguru material in all elements known from both species. Taylor found 26 distinct osteological (bone-based) characters, a larger difference than that between, e.g., *Diplodocus* and *Barosaurus*, and therefore argued that the African material should be placed in its own genus, *Giraffatitan*, as *G. brancai*. An important difference between the two genera is the overall body shape, with *Brachiosaurus* having a 23% longer dorsal (trunk) vertebrate series and a 20 to 25% longer and also taller tail.

## History of discovery

The genus Brachiosaurus, and type species B. altithorax, are based on a partial postcranial skeleton from Fruita, in the valley of the Colorado River of western Colorado. This specimen was collected from rocks of the Brushy Basin Member of the Morrison Formation in 1900 by Elmer S. Riggs and his crew from the Field Columbian Museum (now the Field Museum of Natural History) of Chicago. Riggs and company were working in the area as a result of favorable correspondence between Riggs and S. M. Bradbury, a dentist in nearby Grand Junction. In 1899 Riggs had sent inquiries to rural locations in the western United States concerning fossil finds, and Bradbury, an amateur collector himself, reported that dinosaur bones had been collected in the area since 1885. The locality, Riggs Quarry 13, was found on a small hill later known as Riggs Hill; it is marked by a plaque. Additional Brachiosaurus fossils are reported on Riggs Hill, but other fossil finds on the hill have been vandalized. Riggs published a short report in 1901, noting the unusual length of the humerus compared to the femur and the extreme overall size and the resulting giraffe-like proportions, as well as the lesser development of the tail, but did not publish a name for the new dinosaur. Riggs followed his 1903 publication that named *Brachiosaurus altithorax* with a more detailed description in a monograph in 1904.

The Fruita skeleton was not the first discovery of *Brachiosaurus* bones, although it was the first to be recognized as belonging to a new and distinct animal. In 1883, a sauropod skull was found near Garden Park, Colorado, at Felch Quarry 1, and was sent to Othniel Charles Marsh (of "Bone Wars" fame). Marsh incorporated the skull into his skeletal restoration of "Brontosaurus" (now *Apatosaurus*). It eventually became part of the collections of the National Museum of Natural History, as USNM 5730. In the 1970s, when Jack McIntosh and David Berman were working on the issue of the true skull of *Apatosaurus*, they reevaluated the Garden Park skull as more similar to *Camarasaurus*. It was described and recognized as a *Brachiosaurus* skull in 1998 by Kenneth Carpenter and Virginia Tidwell, intermediate in form between *Camarasaurus* and *Giraffatitan brancai* (then still considered to be *B. brancai*). Because there are no overlapping parts between this skull and FMNH P 25107, it cannot be confidently assigned to a species, so it is classified as *Brachiosaurus* sp.

Additional discoveries of *Brachiosaurus* material in North America have been uncommon and consist of a handful of bones. Material has been described from Colorado, Oklahoma, Utah, and Wyoming, and undescribed material has been mentioned from several other sites. One of these specimens, a shoulder blade from Dry Mesa Quarry, Colorado, is one of the specimens at the center of the *Supersaurus*/*Ultrasauros* issue of the 1980s and 1990s. In 1985, James A. Jensen described disarticulated sauropod remains from the quarry as belonging to several taxa, including the new genera *Supersaurus* and *Ultrasaurus*, the latter renamed *Ultrasauros* shortly thereafter because another sauropod already had the name. Later study showed that the "ultrasaur" material mostly belonged to *Supersaurus*, although the shoulder blade did not. Because the holotype of *Ultrasauros*, a back vertebra, was one of the specimens that was actually from *Supersaurus*, the name *Ultrasauros* is a synonym of *Supersaurus*. The shoulder blade is now assigned to *Brachiosaurus*, but the species is uncertain. In addition, the Dry Mesa "ultrasaur" was not as large as had been thought; the dimensions of the shoulder bone indicate that the animal was smaller than Riggs' original specimen of *Brachiosaurus*.

## Paleobiology

### Feeding ecology

Brachiosaurus is thought to have been a high browser, feeding on foliage well above the ground. Even if it did not hold its neck near vertical, and instead had a straighter neck, its head height may still have been over 30 ft above the ground. It probably fed mostly on foliage above 16 ft. This does not preclude the possibility that it also fed lower at times, between 9.8 to 16 ft up. Its diet likely consisted of ginkgoes, conifers, tree ferns, and large cycads, with intake estimated at 440 to 480 pounds of plant matter daily. However, more recent studies estimate that 530 pounds of plant matter would have been sufficient to feed a 70 metric ton sauropod, so *Brachiosaurus* may have required only about 260 pounds of fodder a day. Brachiosaur feeding involved simple up–and–down jaw motion. The teeth were arranged to shear material as they closed, and were probably used to crop and/or nip vegetation.

### Neck position

In contrast to most other sauropods, brachiosaurids had a sloped back, due to their long front legs. So, if the neck exited the body in a straight line, it already pointed up.

## JPInstitute.com Description

Until recently, Brachiosaurus was the largest known dinosaur, and made famous by the movie "Jurassic Park". It is very tall (40 feet!) and very heavy - more than 12 elephants! Unlike most of the other long-necked dinosaurs, Brachiosaurus was specifically designed to reach high into treetops to gather its meals. It had front legs that were longer than its hind legs which pointed its long neck upward. It had a shorter tail than most other big long-necked dinosaurs.

It is possible that some specimens of Brachiosaurus reached heights exceeding 50 feet and weighed as much as 80 tons; in fact, it may never have stopped growing as long as it lived, which may have been over 100 years! It had, like other typical sauropods, peg-like teeth in a head that seemed very small for such a large creature. Studies about how much these creatures needed to eat and how such a small head could ingest enough food to fuel such a large body have concluded that a full grown Brachiosaurus would have needed to eat 440 pounds (200 kg) of food every day - if it was warm-blooded as many scientists believe. Some scientists have stated that these huge, small-headed creatures would have needed to eat every waking moment in order to provide enough food to keep such a large body alive. Brachiosaurus, like other sauropods, seemed to have every adaptation needed for continuous eating, including having nostrils on the top of its head, so breathing would not interfere with eating.

In order to facilitate the processing of food, which it could not chew with its teeth, Brachiosaurus swallowed stones that the dinosaur kept in its gizzard similar to that found in a chicken. The tough plant fibers would spend time in the gizzard stewing and being ground up by the stones. It probably traveled in herds, the sheer size of the adults protecting the young from predators. This creature is known from two fairly complete skeletons, one of which is on display in Berlin, Germany and the other in Chicago, USA.

## Dinosaur Field Guide Description

Brachiosaurus ("arm lizard") one of the most spectacular dinosaur ever seen. It gets its name from the great height of its humerus, or upper arm bone--which is longer than most humans are tall! Originally discovered 1900 in Colorado, Brachiosaurus was named in 1903 by Elmer Riggs of the Field Museum in Chicago. For almost a century, Brachiosaurus was considered the tallest of all dinosaurs. It was over 50 feet (15 m) tall, and no other animal came close. Imagine going to the fifth floor of a building an looking down at the sidewalk. Now imagine your feet are at streetlight and this is how call you are! Get the idea? Today, however, there is a new contender for the title of tallest dinosaur. It is Sauroposeidon, named in 2000. Scientists believe it would stand 60 feet (18 m) tall! New studies by computer specialists suggest that Brachiosaurus may not have carried its neck angled up as high as was once thought. It may have carried the neck more at 45 to 60 degree angle. Although this changes its height, it does not change its length--or our wonder at this gigantic, graceful dinosaur.

### Fun Facts

Brachiosaurus lived in both the United States and Africa during the Jurassic. Because Brachiosaurus would have been a terrible swimmer, this shows scientists that Africa and North America were connected during the Jurassic.

### Trivia

Brachiosaurus was one of the few dinosaurs that was literally too big to attack!

## Appearance in other media

### *The Land Before Time*

The Land Before Time X:The Great Longneck Migration, a young green Brachiosaurus named Shorty.

### *We're Back! A Dinosaur's Story*

It appears in Pet Dinosaur: An Owner's Manual Your Pet Dinosaur: An Owner's Manual.

## Links

http://web.archive.org/web/20040214165526fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_brach.html
https://web.archive.org/web/20080706160410/http://kids.yahoo.com/dinosaurs/8--Brachiosaurus

## References

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2. ↑ 2.0 2.1 2.2 2.3 Foster, J. (2007). "Brachiosaurus altithorax." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 205–208.
3. ↑ Wedel, M.J. (2003). "Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs." *Paleobiology* **29**:243-255.
4. ↑ Wedel, M.J. (2003). "The evolution of vertebral pneumaticity in sauropod dinosaurs." *Journal of Vertebrate Paleontology* **23**:344-357.
5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 5.19 5.20 5.21 5.22 5.23 5.24 5.25 Taylor, M.P. (2009). "A re-evaluation of *Brachiosaurus altithorax* Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from *Giraffatitan brancai* (Janensh 1914)." *Journal of Vertebrate Paleontology*, **29**(3): 787-806.
6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Riggs, E.S. (1903). "Brachiosaurus altithorax, the largest known dinosaur." American Journal of Science (series 4) 15(88): 299-306.
7. ↑ 7.0 7.1 7.2 7.3 7.4 Paul, G.S. (1988). "The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world's largest dinosaurs" (pdf). Hunteria 2 (3).
8. ↑ 8.0 8.1 8.2 Foster, J.R. (2003). Paleoecological analysis of the vertebrate fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain region, U.S.A.. New Mexico Museum of Natural History and Science Bulletin, 23. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science.
9. ↑ Holtz, T.R. Jr. (2008) *Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages* Supplementary Information
10. ↑ 10.0 10.1 10.2 10.3 Riggs, E.S. (1904). "Structure and relationships of opisthocoelian dinosaurs. Part II. The Brachiosauridae". Geological Series (Field Columbian Museum) 2 (6): 229–247.
11. ↑ Lambert, David; and the Diagram Group (1990). "Brachiosaurids". The Dinosaur Data Book. New York: Avon Books. p. 142. ISBN 0-380-75896-3.
12. ↑ Chure, D.; Britt, B.; Whitlock, J. A.; and Wilson, J. A. (2010). "First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition". Naturwissenschaften 97 (4): 379–391. doi:10.1007/s00114-010-0650-6. PMC 2841758. PMID 20179896.
13. ↑ 13.0 13.1 Ksepka, D. T.; and Norell, M. A. (2010). "The illusory evidence for Asian Brachiosauridae: new material of Erketu ellisoni and a phylogenetic appraisal of basal Titanosauriformes" (pdf). American Museum Novitates 3700: 1–27. doi:10.1206/3700.2.
14. ↑ 14.0 14.1 14.2 14.3 Riggs, E.S. (1091). "The largest known dinosaur". Science 13 (327): 549–550. doi:10.1126/science.13.327.549-a. PMID 17801098.
15. ↑ de Lapparent,A.F. & Zbyszewski, G. (1957). "Les dinosauriens du Portugal". *Mémoire Service géologique Portugal* **2**:1–63.
16. ↑ Antunes, M.; Mateus, O. (2003). "Dinosaurs of Portugal". Comptes rendus. Palévol 2 (1): 77–95. doi:10.1016/S1631-0683(03)00003-4.
17. ↑ 17.0 17.1 Janensch, W. (1914). "Übersicht über der Wirbeltierfauna der Tendaguru-Schichten nebst einer kurzen Charakterisierung der neu aufgefuhrten Arten von Sauropoden." *Archiv fur Biontologie*, **3**: 81–110.
18. ↑ 18.0 18.1 Janensch, W. (1929). "Material und Formengehalt der Sauropoden in der Ausbeute der Tendaguru-Expedition." *Palaeontographica* **(Suppl. 7) 2**:1–34.
19. ↑ 19.0 19.1 de Lapparent, A.F. (1960): "Les dinosauriens du "continental intercalaire" du Sahara central" ("The dinosaurs of the "continental intercalaire" of the central Sahara.") *Mémoires de la Société Géologic de France, Nouvelle Série* **88A** vol.39(1-6):1-57. [in French; a translated version, by Matthew Carrano (pdf, no figures), is available through the Polyglot Paleontologist]
20. ↑ Janensch, W. (1950). "Die Wirbelsäule von *Brachiosaurus brancai*." *Palaeontographica* **(Suppl. 7) 3**:27–93.
21. ↑ Janensch, W. (1961). "Die Gliedmaßen und Gliedmaßengürtel der Sauropoden der Tendaguru-Schichten." **Palaeontographica (Suppl. 7) 3**:177–235.
22. ↑ 22.0 22.1 Olshevsky, G. (1991). "A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia." *Mesozoic Meanderings* **2**:1-196
23. ↑ 23.0 23.1 Glut, D.F. (1997). "Brachiosaurus". Dinosaurs: The Encyclopedia. McFarland & Company. pp. 213–221. ISBN 0-89950-917-7.
24. ↑ 24.0 24.1 Turner, C.E.; and Peterson, F. (1999). "Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, USA". In Gillete, David D. (ed.). Vertebrate Paleontology in Utah. Miscellaneous Publication 99-1. Salt Lake City, Utah: Utah Geological Survey. pp. 77–114. ISBN 1-55791-634-9.
25. ↑ 25.0 25.1 Chenoweth, W.L. (1987). "The Riggs Hill and Dinosaur Hill sites, Mesa County, Colorado". In Averett, W. R. (ed.). Paleontology and geology of the Dinosaur Triangle. Grand Junction, Colorado: Museum of Western Colorado. pp. 97–100. ISBN 9999790410.
26. ↑ Marsh, O.C. (1891). "Restoration of Triceratops" (pdf). American Journal of Science 41 (244): 339–342.
27. ↑ McIntosh, J.S.; and Berman, D.S. (1975). "Description of the palate and lower jaw of the sauropod dinosaur Diplodocus (Reptilia: Saurischia) with remarks on the nature of the skull of Apatosaurus". Journal of Paleontology 49 (1): 187–199.
28. ↑ 28.0 28.1 28.2 Carpenter, K. and Tidwell, V. (1998). "Preliminary description of a *Brachiosaurus* skull from Felch Quarry 1, Garden Park, Colorado." Pp. 69–84 in: Carpenter, K., Chure, D. and Kirkland, J. (eds.), *The Upper Jurassic Morrison Formation: An Interdisciplinary Study*. *Modern Geology*, **23**:1-4.
29. ↑ 29.0 29.1 Jensen, J.A. (1987). "New brachiosaur material from the Late Jurassic of Utah and Colorado". The Great Basin Naturalist 47 (4): 592–608.
30. ↑ 30.0 30.1 Curtice, B., Stadtman, K., and Curtice, L. (1996) "A re-assessment of Ultrasauros macintoshi (Jensen, 1985)." Pp. 87-95 in M. Morales (ed.), The Continental Jurassic: Transactions of the Continental Jurassic Symposium, Museum of Northern Arizona Bulletin number 60.
31. ↑ Curtice, B.; and Stadtman, K. (2001). "The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae". In McCord, R.D.; and Boaz, D. (eds.). Western Association of Vertebrate Paleontologists and Southwest Paleontological Symposium - Proceedings 2001. Mesa Southwest Museum Bulletin. 8. pp. 33–40.
32. ↑ Bonnan, M.F.; and Wedel, M.J. (2004). "First occurrence of Brachiosaurus (Dinosauria, Sauropoda) from the Upper Jurassic Morrison Formation of Oklahoma". PaleoBios 24 (2): 12–21.
33. ↑ Jensen, J.A. (1985). "Three new sauropod dinosaurs from the Upper Jurassic of Colorado". The Great Basin Naturalist 45 (4): 697–709.
34. ↑ Hummel, J., Gee, C.T., Südekum, K.-H., Sander, P.M., Nogge, G. and Clauss, M. (2008). "In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection". *Proceedings of the Royal Society B*, **275**:1015-1021. doi:10.1098/rspb.2007.1728
35. ↑ Barrett, Paul M.; and Upchurch, Paul (2005). "Sauropodomorph diversity through time". In Curry Rogers, Kristina A.; and Wilson, Jeffrey A.. The Sauropods: Evolution and Paleobiology. Berkeley, CA: University of California. pp. 125–156. ISBN 0-520-24623-3.
36. ↑ Stevens, K. A. and Parrish, M. J. (1999). "Neck posture and feeding habits of two Jurassic sauropod dinosaurs." *Science* **284**:798–800. doi:10.1126/science.284.5415.798
37. ↑ Stevens, K. A. and Parrish, M. J. (2005). "Digital reconstructions of sauropod dinosaurs and implications for feeding." In *The sauropods: evolution and paleobiology* (eds. J. A.Wilson & K. Curry-Rogers), pp. 178–200. Berkeley, CA: University of California Press.
38. ↑ Stevens, K. A. and Parrish, M. J. (2005). "Neck posture, dentition and feeding strategies in Jurassic sauropod dinosaurs." In "Thunder Lizards: The Sauropodomorph dinosaurs" (eds. V. Tidwell & K. Carpenter). Bloomington, IN: Indiana University Press.