The centrum walls, laminae, septae, and struts that comprised the vertebrae were primarily made of compact bone (Reid, 1996). The null hypothesis is that the long cervical ribs of theropods and sauropods functioned similarly to the short cervical ribs and long tendons of birds, as the insertions of long hypaxial muscles. Tall neural spines increase mechanical advantage of muscles when the vertebrae are held horizontally, but this is unlikely to have been a common posture for sauropods (Taylor, Wedel & Naish, 2009). In fact, Diplodocus is the longest dinosaur known from a complete skeleton. Even if this were so, however, it is difficult to see the benefit in Apatosaurus excelsus Marsh, 1879a of cervical ribs held so far below the centrum – an arrangement that seems to make little sense from any mechanical perspective, and may have to be written off as an inexplicable consequence of sexual selection or species recognition. But 150 million years of evolution did not suffice for them to exceed a relatively modest 2.5 m. Neck elongation occurs in many extant clades and is also found in many extinct groups. Mineralization or ossification reduces the extensibility of a tendon, and can allow a long, thin tendon to behave more like a short, thick one. Structure and relationships of opisthocoelian dinosaurs. The cervical architecture is rather different in crocodilians, and in non-archosaurian diapsids such as lizards, snakes, ichthyosaurs and plesiosaurs: there are no epipophyses, and the main epaxial neck muscles are the Mm. In a skeletal reconstruction of the therizinosauroid Nanshiungosaurus Dong, 1979 by Paul (1997, p. 145), the neck is 2.9 times the length of the humerus. This family of dinosaurs, however, wasn't always so gigantic. In this respect, sauropod osteology is intermediate between the conditions of crocodilians and birds – so the widely recognized similarity of sauropod cervicals to those of birds (e.g., Wedel & Sanders, 2002; Tsuihiji, 2004), while significant, should not be accepted unreservedly. In fact, there are several likely reasons. 7.3); but their presence in other titanosaurs such as Rapetosaurus Curry & Forster, 2001  (Curry & Forster, 2001, figure 3A), and Saltasaurus Bonaparte & Powell, 1980 (Powell, 1992, figure 5) and in outgroups such as Giraffatitan (Fig. (The same effect would also have caused some bending of cervical ribs, but the lower stresses in ventral musculature would have reduced the effect.). In conclusion, while some ligament was undoubtedly present within the trough formed by the metapophyses of bifid neural spines, much of the space was probably filled with pneumatic diverticula. The air space proportion (ASP) of a bone is the proportion of its volume taken up by pneumatic cavities (Wedel, 2005). Diplodocus had the standard sauropod body plan: a long tail, a large body supported by four pillar-like legs, and a long neck. A lower limit to neural spine length is imposed by the volume of muscle needed to produce the range of motion. This is within 6% of Leidy’s (1870) estimate of “almost twenty-two feet”, or about 6.7 m, and approximately equal to the 7-m neck length reported for Albertonectes by Kubo, Mitchell & Henderson (2012). These lengths are 3.60, 4.04 and 4.06 times the lengths of their respective C5s. If these vertebrae are tentatively assigned lengths intermediate between those that preceded and succeeded them (i.e., 43.4 and 32.8 cm) then the total length of all seven centra is 254.9 cm, more than 30% longer than the illustrated length. Even in taxa that do have bifid spines, they are rarely split through the whole series: for example, the first eight cervicals of Barosaurus do not have bifid spines (McIntosh, 2005; MJW, pers. 7.4) and Camarasaurus (Osborn & Mook, 1921, plate LXVII, figure 9; McIntosh et al., 1996a, figure 29) indicates that their absences in Malawisaurus and Isisaurus, if not due to damage to the material, represent secondary losses. It didn’t rain much in the Morrison Formation. The neural spines and epipophyses of sauropods both anchored epaxial muscles, but as they were differently developed in different taxa, they were probably of varying mechanical importance in different taxa. But as noted above, sauropod vertebrae were very pneumatic, typically consisting of 60% air. Their huge size was likely a … TypoMissing or incorrect metadataQuality: PDF, figure, table, or data qualityDownload issuesAbusive behaviorResearch misconductOther issue not listed above. But life restorations of sauropods going back to the 1800s have been unanimous that this cannot have been the case in sauropods, as such over-muscled necks would have been too heavy to lift; and the various published reconstructions of sauropod neck cross sections (e.g., Paul, 1997, figure 4; Schwarz, Frey & Meyer, 2007, figure 7, 8A, 9E) all agree in making the total diameter including soft-tissue only 105–125% that of the vertebrae alone. It has often been assumed that in sauropods with bifid cervical spines, the intermetapophyseal trough housed a large ligament analogous to the nuchal ligament of artiodactyl mammals (e.g., Janensch, 1929, plate 4; Alexander, 1985, pp. None of them. As is frequently the case with sauropods, no skull has yet been found. CM 584 (Fig. However, in one clade – birds – an elongate trachea is not unusual, having evolved in swans (Banko, 1960), cranes (Johnsgard, 1983), moas (Worthy & Holdaway, 2002), birds-of-paradise (Frith, 1994) and several other groups. Whatever mechanical barriers prevented the evolution of truly long necks in other terrestrial vertebrates, sauropods did not just break that barrier – they smashed it. Other elasmosaurs may have had equally long necks. It is greatly exceeded by azhdarchid pterosaurs, among which C5 of Quetzalcoatlus Lawson, 1975 can attain an astonishing 12.4 (measured from Witton & Naish (2008, figure 4c)) and an isolated cervical from the Hell Creek Formation might have achieved 15 (measured from Henderson & Peterson (2006, figure 3)). As noted by Wedel, Cifelli & Sanders (2000b, p. 377), one possible explanation is that, because of their size, sauropods were under strong selection for larger feeding envelopes, which drove them to evolve longer necks. However, they did not evolve necks as long as those of sauropods with similar mass, probably in part for this reason: the increased moment caused by neck elongation in a biped must be counteracted by an equal moment caused by a longer or more massive tail, increasing the physiological cost. Although sauropods shared a common bauplan, their morphological disparity was much greater than has usually been assumed (Taylor & Naish, 2007, pp. Measured from the skeletal reconstruction of Xu et al. 11.1), the neural spine is very large and anchors essentially all of the large multisegment epaxial muscles (Tsuihiji, 2005, figure 2), and there are no epipophyses at all. So sauropods inherited as their primitive state necks that were already more elongated, and heads that were proportionally smaller, than in most animals. (Raising the neck is work, and while the force exerted by a muscle is proportional to its cross-sectional area, the work it can do varies with volume, so shorter muscles need a correspondingly larger cross-sectional area.). Characteristic of diplodocids, this primitive, four-legged, plant-eater had a long, whip-like tail. They can be taken only as indicative, not as reliable figures. Many years ago, scientists speculated that sauropods spent most of their time in water to support their enormous weight. The typical length of the neck of the ostrich is only 1.0 m (sum of vertebral lengths in Dzemski & Christian (2007), Table 1, plus 8% to allow for intervertebral cartilage – see Cobley, 2011, p. 16). In extinct animals, except in a very few cases of exceptional preservation, only the fossilized bones are available: but using extant animals as guides, osteological features can be interpreted as correlates of the absent soft tissue, so that the ligaments and musculature of the extinct animal can be tentatively reconstructed (Bryant & Russell, 1992; Witmer, 1995). Many groups of animals seem to be constrained as to the number of cervical vertebrae they can evolve. The trend is opposite in Erketu, in which the epipophyses increasingly dominate neural spines anteriorly. Also, longer trachea and blood vessels cause physiological difficulties: weight support is only one of the problems imposed by a long neck. One of the best-known sauropods, Diplodocus was a large long-necked four-legged animal, with a long, whip-like tail. Specifically, the epipophyses are osteological correlates of the M. longus colli dorsalis and M. cervicalis ascendens epaxial muscles, which must therefore have been present in sauropods, although we can not conclude from this that they were necessarily the dominant epaxial muscles as they are in birds. and potential for large body size. Therizinosaurus cheloniformis Maleev, 1954 is a bizarre, long-necked giant theropod, known from incomplete remains. "Moreover we found that the enamel of the teeth of Bagualia was about 7 times thicker than those of the other herbivores that went extinct. But this hypothesis is badly flawed – see Wedel, Cifelli & Sanders, 2000b, p. 379–380; Klein, Christian & Sander, 2012). You can also choose to receive updates via daily or weekly email digests. Diplodocus is among the most easily identifiable dinosaurs, with its typical sauropod shape, long neck and tail, and four sturdy legs. They had very long necks and tails, relatively small skulls and brains, and erect limbs reminiscent of the limbs of elephants. Reasoning by analogy with modern giraffes, most paleontologists believe sauropods evolved their ultra-long necks in order to reach the high leaves of trees. Scientists such as Kent Stephens have used this to argue that sauropods like Diplodocus did not raise their heads much past shoulder level, but studies to come showed that all tetrapods seem to hold their necks at the maximum possible vertical extension when in a normal, alert posture, and argued that the same would hold true for sauropods with unknown, unique traits that set the soft tissue form of their … Think of the word "dinosaur," and two images are likely to come to mind: a snarling Velociraptor hunting for grub, or a giant, gentle, long-necked Brachiosaurus lazily plucking the leaves off trees. 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