Dinosaur models: the good, the bad, and using - Gregory S. Paul

More documents

Recommendations

Info

138 Dinofest
FIGURE7-Front view of 6 tonne Triceratops fitted onto a large Ceratopsipes trackway. Note that although the chest ribs are narrow, and the foreprints are wider gauge than the larger hindprints, forelimb posture is erect. On the lower left are very large trackways that may have been made by oversized ceratopsids. Scale bar equals 1 m. than the front end of the hips. The hips become broader progressing backwards, the reverse of the usual condition. It is extremely peculiar that the transverse processes at the base of the tail are so long that they form a set of functional ribs behind the pelvis. The false ribs' slenderness and dorsally convex are, the posteriorly broad hips, and the absence of chevrons from the tail base suggest that there was a large extension of the digestive tract behind the hips, a rarity among vertebrates. Iguanodonts and Hadrosaurs, Sometimes Bigger Than You Think Big ornithopod heads and necks were moderate in size, bodies were compact and somewhat slab sided (except camptosaurs), tails were moderate in size, and hindlegs were long and powerfully muscled in these running forms. In some iguanodonts, Dinofest.® International Proceedings 139 and all hadrosaurs, the front half of the trunk was strongly downarched (Paul, 1987), which dramatically shortened the trunk and reduced its volume. If ungulate-like nuchal tendons helped support the head and neck in tall spined iguanodonts and in hadrosaurs (Czerkas, 1993) they were narrow and had little influence on mass. The belly was extremely deep in some iguanodonts, and the deep tails were very compressed from side to side. Although the arms were long, they were slender and had little influence upon overall mass. Plump Camptosaurus seems a modest sized dinosaur because many skeletons are juvenile, but some individuals approached 2 tonnes (Erickson, 1988). Large Iguanodon exceeded 3 tonnes, higher values in Colbert (1962) and Alexander (1989) are based on inaccurate models. Also excessive, and often inconsistent, are mass estimates for typical American hadrosaurs as high as 4 tonnes. Colbert estimated that the New York Corythosaurus was heavier than the Anatotitan in the same hall, yet visual comparison on site shows that the latter is the bigger of the two specimens (AppendFigs. 7,8). Most American examples weighed about 2.5-3.0 or more tonnes (the 2.2 tonne estimate by Beland & Russell [1978] differs only in that their models were too hollow bellied). These masses are comparable to big white rhino bulls (AppendFig. 6-8), although the hadrosaurs tend to look larger because of their deeper body profile, large but thin tails, and taller stature. Hadrosaurs are unusually uniform and isometric in body design and proportions regardless of size, and some were surprisingly big. Some American hadrosaurs are two thirds or more longer than the norm (Morris, 1972) and suggest individuals of around 13 tonnes. Asian Shantungosaurus is modeled at 10-13 tonnes. The biggest hadrosaur trackways (Lockley et al., 1983) record individuals with feet about twice as large as those of typical examples, and imply weights as high as 20 to 25 tonnes, World record individuals approaching or exceeding 30 tonnes are probable. Giant hadrosaurs greatly outweighed ceratopsids, at least matched the biggest land mammals, and rivaled many sauropods-quite a feat for animals that bore most of their mass on two legs. Hadrosaurs were longer limbed than sauropods. Example: Shantungosaurus hindlegs were about as long as those of Apatosaurus, but the latter was about a third heavier. Some Very Large Footprints The 1.3 m long Jurassic Gigantosauropus footprints are the largest yet discovered (Mensink & Mertmann, 1984). They are so enormous, and ill defined in shape, that they are difficult to accept at face value. However, they do not show clear signs of distortion, and appear to represent a three toed biped of 20 to 30 tonnes and over 15 m length. No theropod is known to have reached more than a third of this bulk, such masses and dimensions are approached by some ornithopods skeletons and prints, and the prints' short, broad toes are most like those of ornithopods. MASSIVE MISTAKES AND REVELATIONS Many studies of dinosaur biology depend upon accurate mass estimates. Some examples of how mass estimates incorrect and correct can lead to results errant and useful are detailed below. Rocking, Stomping Dinosaurs Alexander (1989) used the inaccurate BMNH commercial models to measure the fore-and-aft mass distribution of dinosaurs. More accurate models would give better results, but there will always be a high degree of uncertainty because it is not possible to precisely restore the internal distribution (especially internal air-spaces) of mass in extinct forms. Just a modest error
Page 1 and 2: Dinofestts International Copyright
Page 3 and 4: .'". .... ~ } ..... '~" ••.....
Page 5 and 6: Dinofest®J International Proceedin
Page 7 and 8: facial muscles. In many dinosaur mo
Page 9: Dinofes~ International Proceedings
Page 13 and 14: CONCLUDING COMMENTS The results of

Dinosaur models: the good, the bad, and using - Gregory S. Paul

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?