And see also the followup:
- Taylor, Michael P. 2014. Quantifying the effect of intervertebral cartilage on neutral posture in the necks of sauropod dinosaurs. PeerJ 2:e712. doi:10.7717/peerj.712 [PDF]
Taylor and Wedel (2013c: Figure 1). The world’s biggest mounted skeleton: the sauropod Giraffatitan brancai. Mounted skeleton of Giraffatitan brancai paralectotype MB.R.2181 at the Museum für Naturkunde Berlin, Berlin, Germany. Lead author for scale, by the skeleton’s elbow. This is the largest mounted skeleton in the world based primarily on real remains rather than sculptures. It is 13.27 m tall, and represents an animal that probably weighed about 20–30 tonnes (Taylor 2009). Much larger sauropods existed, but they are known only from fragmentary remains.
Taylor and Wedel (2013c: Figure 2). Cervical vertebrae of a turkey and a sauropod. Representative mid-cervical vertebrae from a turkey (top) and the sauropod Giraffatitan brancai (bottom), not to scale. Each vertebra is shown in left lateral view (on the left) and posterior view (on the right). Articular surfaces, where each vertebra meets its neighbour, are highlighted in red (for the centra) and blue (for the zygapophyses). Articular surfaces that are concealed from view are cross-hatched: prezygapophyses face upwards and inwards, so that the facets are inclined towards the midline. In sauropods, the centra have ball-and-socket joints. In birds, the joints are saddle-shaped, and the anterior articular surface is hidden in lateral view. Despite numerous differences in detail, the bird and sauropods vertebrae strongly resemble each other in fundamentals.
Taylor and Wedel (2013c: Figure 3). Articulated sauropod vertebrae. Representative mid-cervical vertebra of Giraffatitan brancai, articulating with its neighbours. The condyle (ball) on the front of each vertebra’s centrum fits into the cotyle (socket) at the back of the preceding one, and the prezygapophyses articulate with the preceding vertebra’s postzygapophyses. These vertebrae are in Osteological Neutral Pose, because the pre- and postzygapophyseal facets overlap fully.
Taylor and Wedel (2013c: Figure 4). Intervertebral articular discs of an ostrich (not to scale). Left: first sacral vertebra in anterior view, showing articular disc of joint with the last thoracic vertebra. Right: posterior view view of a cervical vertebra, with probe inserted behind posterior articular disc. The cervical vertebra is most relevant to the present study, but the the sacral vertebra is also included as it shows the morphology more clearly. These fibrocartilaginous articular discs divide the synovial cavity, like the articular discs in the human temporomandibular and sternoclavicular joints, and should not be confused with the true intervertebral discs of mammals and other animals, which consist of a nucleus pulposus and an annulus fibrosus.
Taylor and Wedel (2013c: Figure 5). Intervertebral gaps in camel necks. Head and neck of dromedary camels. Top: UMZC H.14191, in right lateral view, posed well below habitual posture, with apparently disarticulated C3/C4 and C4/C5 joints. Photograph taken of a public exhibit at University Museum of Zoology, Cambridge, UK. Bottom: OUMNH 17427, in left lateral view, reversed for consistency with Cambridge specimen. Photograph taken of a public exhibit at Oxford University Museum of Natural History, UK. Inset: detail of C4 of the Oxford specimen, showing articulations with C3 and C5. The centra are separated by thick pads of artificial ‘‘cartilage’’ to preserve spacing as in life.
Taylor and Wedel (2013c: Figure 6). Range of motion in a vertebral joint. Range of Motion (ROM) illustrated schematically for a single intervertebral joint of Giraffatitan brancai. The grey-scale vertebrae are shown in Osteological Neutral Pose. The red vertebra has been rotated upwards (“extended”) until its postzygapophyseal facet overlaps 50% with the prezygapophyseal facet of the succeeding vertebra, in accordance with the assumption of Stevens and Parrish. Similarly, the blue vertebra has been rotated downwards (“flexed”) until 50% zygapophyseal overlap is achieved. Because the zygapophyseal articulations in the neck of Giraffatitan are some way anterior to the those of the centra, the relative movement of the articulating zygapophyseal facets is anteroventral–posterodorsal; in taxa such as the turkey in which the zygapophyseal articulation are directly above those of the centra, relative movement is anterior-posterior.
Taylor and Wedel (2013c: Figure 7). Measurement rig for necks. Measurement rig for intact turkey necks, constructed from Duplo bricks and baseboard. The neck is pushed into the angle between the back wall (yellow) and the left wall (red), and held straight along the back wall. The marker brick (blue) abuts the end of the neck: the distance between the left wall and the marker brick is the length of the neck between perpendiculars.
Taylor and Wedel (2013c: Figure 8). Cervical vertebra 7 from a turkey. Anterior view on the left; dorsal, left lateral and ventral views in the middle row; and posterior on the right.
Taylor and Wedel (2013c: Figure 9). Functional length of a cervical vertebra. Functional centrum length of a cervical vertebra of a turkey. The measurement is taken between the inflection points of the saddle-shaped articulations at each end of the centrum, shown here by the blue arrow connecting the red lines that mark the position of the saddle points.
Taylor and Wedel (2013c: Figure 10). Modified calipers for measuring functional vertebral length. Modified calipers used to measure functional length of a turkey vertebra. The tooth glued to the left jaw protrudes into the transverse concavity of the anterior articular surface and the dorsoventral concavity of the posterior articular surface straddles the right jaw.
Taylor and Wedel (2013c: Figure 11). Fifth and partial sixth cervical vertebrae of Sauroposeidon. Photograph and x-ray scout image of C5 and the anterior portion of C6 of Sauroposeidon OMNH 53062 in right lateral view. The anterior third of C5 eroded away before the vertebra was collected. C6 was deliberately cut through in the field to break the multi-meter specimen into manageable pieces for jacketing (see Wedel and Cifelli 2005 for details). Note that the silhouettes of the cotyle of C5 and the condyle of C6 are visible in the x-ray.
Taylor and Wedel (2013c: Figure 12). CT slices from fifth cervical vertebrae of Sauroposeidon. X-ray scout image and three posterior-view CT slices through the C5/C6 intervertebral joint in Sauroposeidon OMNH 53062. In the bottom half of figure, structures from C6 are traced in red and those from C5 are traced in blue. Note that the condyle of C6 is centered in the cotyle of C5 and that the right zygapophyses are in articulation.
Taylor and Wedel (2013c: Figure 13). Joint between sixth and seventh cervicals vertebrae of Sauroposeidon. X-ray scout image of the C6/C7 intervertebral joint in Sauroposeidon OMNH 53062, in right lateral view. The silhouette of the condyle is traced in blue and the cotyle in red. The scale on the right is marked off in centimeters, although the numbers next to each mark are in millimeters.
Taylor and Wedel (2013c: Figure 14). Geometry of opisthocoelous intervertebral joints. Hypothetical models of the geometry of an opisthocoelous intervertebral joint compared with the actual morphology of the C5/C6 joint in Sauroposeidon OMNH 53062. A. Model in which the condyle and cotyle are concentric and the radial thickness of the intervertebral cartilage is constant. B. Model in which the condyle and cotyle have the same geometry, but the condyle is displaced posteriorly so the anteroposterior thickness of the intervertebral cartilage is constant. C. the C5/C6 joint in Sauroposeidon in right lateral view, traced from the x-ray scout image (see Figure 12); dorsal is to the left. Except for one area in the ventral half of the cotyle, the anteroposterior separation between the C5 cotyle and C6 condyle is remarkably uniform. All of the arrows in part C are 52 mm long.
Taylor and Wedel (2013c: Figure 15). First and second dorsal vertebrae of Apatosaurus CM 3390. Articulated first and second dorsal vertebrae of Apatosaurus CM 3390. A. Digital model showing the two vertebrae in articulation, in left lateral (top) and ventral (bottom) views. B-G. Representative slices illustrating the cross-sectional anatomy of the specimen, all in posterior view. B. Slice 25. C. Slice 31. D. Slice 33. E. Slice 37. F. Slice 46. G. Slice 61. Orthogonal gaps are highlighted where the margins of the condyle and cotyle are parallel to each other and at right angles to the plane of the CT slice. ‘Zygs’ is short for ‘zygapophyses’, and NCS denotes the neurocentral synchondroses.
Taylor and Wedel (2013c: Figure 16). Dorsal vertebrae of Apatosaurus CM 11339. Articulated middle or posterior dorsal vertebrae of Apatosaurus CM 11339. A. X-ray scout image showing the two vertebrae in articulation, in left lateral view. B–D. Slices 39, 43 and and 70 in posterior view, showing the most anterior appearance of the condyles and cotyles.
Taylor and Wedel (2013c: Figure 17). Effect on neutral pose of including cartilage on ONP. Effect on neutral pose of including cartilage. Top: dorsal view of a turkey cervical vertebra: vertical red line indicates the position of the most anterior part of the midline of the anterior articular surface, which is obscured in later view. Second row: two such vertebrae arranged in osteological neutral pose, with the articular surfaces of the centra abutting and the zygapophyseal facets maximally overlapped. The anterior vertebra is inclined by about 16° relative to the posterior. Third row: two such vertebra, with the centrum of the more posterior one elongated by 6.46% to allow for intervertebral cartilage (shown in blue), and the more anterior positioned with its centrum articulating with the cartilage and the zygapophyses maximally overlapped. The anterior vertebra is inclined by about 31°. The inclusion of cartilage has raised neutral posture by 15°. Green lines represent a horizontal baseline, joining the most ventral parts of the anterior and posterior ends of the vertebrae.
Taylor and Wedel (2013c: Figure 18). Cartilage in the neck of a rhea. Joint between cervicals 11 (left) and 10 (right) of a rhea, sagittally bisected. Left half of neck in medial view. The thin layers of cartilage lining the C11 condyle and C10 cotyle are clearly visible.
Taylor and Wedel (2013c: Figure 19). Alligator head and neck. Sagittally bisected head and neck of American alligator, with the nine cervical vertebrae indicated. Inset: schematic drawing of these nine vertebrae, from Frey 1988: figure 1, reversed.
Taylor and Wedel (2013c: Figure 20). Horse head and neck. Sagittally bisected head and anterior neck of a horse. The first four cervical vertebrae are complete, but the posterior part of the fifth is absent. Note that the condyles are deeply embedded in their cotyles.
Taylor and Wedel (2013c: Figure 21). Camel neck in X-ray. X-ray image of a camel, with tracing to highlight the centra of cervical vertebrae 2–7. (C1 and the anterior part of C2 are obscured by the skull.) Note that most of the condyles do not even reach the posterior margins of their corresponding cotyles, let alone embed deeply within them.
Taylor and Wedel (2013c: Figure 22). Dog neck in X-ray. Neck of a dog (dachsund), in X-ray, with the seven cervical vertebrae indicated. This photo has been used with permission from the Cuyahoga Falls Veterinary Clinic.
Taylor and Wedel (2013c: Figure 23). Neck of a young juvenile giraffe. Neck of a young juvenile giraffe, in various states of dissection, to scale. Top, the neck as received, skinned and stripped of skin, oesophagus and trachea. Second, the neck with most muscle removed and the nuchal ligament stretched out. Third, the vertebrae cleaned of soft tissue and cartilage, laid out with equal intervertebral spacing to attain the same total length as when intact (51 cm). Fourth, the vertebrae in the same condition but articulated as closely as possible, forming a misleading cervical skeleton measuring only 41 cm. Top image in left lateral view; second in right lateral view, reversed; third and fourth in left dorsolateral.
The following paper are cited in the captions of the figures above: