interlocking ends. Such ribs gave great strength to the lumbar region, and are perhaps analogous to the greatly expanded transverse processes of the crocodiles.
Fig. 89. Plesiosaur vertebrae: Polycotylus. Cervical vertebrae from the side and behind, and dorsal vertebrae from in front: az, anterior zygapophysis; pz, posterior zygapophysis; r, r, r, cervical ribs; d, articulation of dorsal rib.
Fig. 90. Vertebrae of gavial from the side (cervical), and from in front (dorsal): az, anterior zygapophysis; pz, posterior zygapophysis; d, diapophysis; r, cervical rib; c, articulation for head; t, for tubercle of dorsal rib.
The first four to six ribs of the Cotylosauria, and rarely also of the Theromorpha, are progressively flattened and dilated, sometimes, as in Diadectes and Limnoscelis (Fig. 95), remarkably so, for the direct support of the short and broad scapula. Not only are these ribs so remarkably dilated in Diadectes, but, continuing the expansion backward, there are three flat dermal plates overlying the following ribs.
The cervical ribs of the Crocodilia (Fig. 90) and Dinosauria are
