Ca23 - Spinosaurus aegyptiacus neotype

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23rd caudal vertebra of the Spinosaurus aegyptiacus neotype, FSAC-KK 11888.

At Ca23, the centrum is smaller than in more proximal caudals, but the neural spine is much more elongate. However, as the neural spines, from Ca11–12 onwards, are inclined distally at an angle of 45°, the dorsoventral depth of the distal portion of the tail is similar to that of the proximo-medial portion - about 70 cm. The chevrons in this region of the tail are as elongate, or even slightly more elongate than those for more proximal caudals. Conversely, the transverse diameter of the tail is much narrower, with centrum 23 being only seven cm in width.

The specimen is housed in the palaeontological collections of the Université Hassan II, Aïn Chock, Casablanca, Morocco.

Reference: Ibrahim N. et al. (2020). Tail-propelled aquatic locomotion in a theropod dinosaur. Nature, doi.org/10.1038/s41586-020-2190-3.