Fig. 3

Histology of vertebral centra of the thalattosauroid from Oregon. A, Transverse section of a middle dorsal centrum (MNCH F71616) in normal light. Note the overall spongious structure and very thin cortex surrounding the centrum. Rectangles mark the enlarged area depicted in B and C. B, Detail of the thin outer cortex and the spongious inner structure of MNCH F71616 in normal light. C, Enlargement of the thin cortex of MNCH F71616 in normal light. D, Sagittal section of a posterior dorsal centrum (MNCH F70662) in normal light. Rectangles mark the enlarged area depicted in E, F, and G. E, Detail of the anterior/posterior margin of MNCH F70662 depicting collapsed trabeculae and a matrix of cartilage (greyish–blackish) in normal light. F, Primary trabeculae reaching into the outer cortex in MNCH F70662. G, Detail of primary trabeculae in MNCH F70662 in normal light. H, Sagittal section of a middle caudal centrum (MNCH F64330) in normal light. Rectangles mark the enlarged area depicted in I–L. I, Anterior or posterior bone side depicting a spongious structure in the inner and a more compact area towards the outer cortex of the middle caudal centrum MNCH F64330 in normal light. J, Boundary between the periosteal tissue to the left and the endochondral, much more finely structured tissue to the right in MNCH F64330 in normal light. K, Detail of parallel-fibred periosteal tissue in the centrum MNCH F64330 in polarized light. L, Detail of the anterior/posterior margin depicting globuli ossei and a cartilage matrix below the articular surface of MNCH F64330 in normal light. Abbreviation: nc neural canal