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. 2015 Oct 7;2(10):150393. doi: 10.1098/rsos.150393

Figure 4.

Figure 4.

Computational model accounts for the third cervical vertebra change between Samotherium (blue) and modern giraffe (red). (a) Aligned C3 of Samotherium and G. camelopardalis show marker placement corresponding to the cranial-most point of the cranial articular facet, caudal-most point of the caudal articular facet, cranial-most point of the cranial bulge, cranial and caudal openings of the foramen transversarium, dorsal-most point of the caudal vertebral body, ventral-most point of the caudal vertebral body, and cranial-most tip of the ventral tubercle. (b) Eight marker positions in aligned lateral views of Samotherium and G. camelopardalis C3. (c) The best fit of a uniform linear ‘stretch’ model applied to the Samotherium fitted to the modern giraffe marker position. The best-fit uniform linear ‘stretch’ coefficient is 2.0 (95% confidence interval (CI) =1.7–2.3). (d) The best fit of stretch–slide model applied to the Samotherium against the modern giraffe marker position. The model predicts that the transition from a modest to marked stretch occurs caudal to the posterior opening of the foramen transversarium 128 mm from the cranial aspect of the bone (95% CI= 92–166 mm) and the corresponding ‘stretch’ coefficients are 1.8 (95% CI= 1.5–2.1) cranial to that point and 2.9 (95% CI=2.5–3.2) caudal to that point (p-value for comparing cranial and caudal elongation coefficients was =0.003). In addition, the model required a 38 mm ‘sliding’ of dorsal with relationship to the ventral vertebra (95% CI=20–58 mm). If no sliding is included in the model, the best predicted values for the transition point and the cranial and caudal ‘stretch’ coefficients are: 122 mm (95% CI=18–226 mm), 1.7 (95% CI=1.0–2.5) and 2.7 (95% CI=1.9–3.5). (e) A schematic of a transformation used in the model. Red rectangle represents the original object. The blue rectangle represents the stretched object, where stretching to the right (caudal) of the vertical line is greater than that to the left of the line. Superposition of horizontal sliding results in the final shape, represented here by the parallelogram.