Figure 12A-D. A in A fossil giant tortoise from the Mehrten Formation of Northern California

Figure 12A-D. A. Cross-section of Mehrten carapace with sulcus pressed into bone, UCMP 134832. B. Profile of Gopherus carapace, edges of sulci are perched, MVZ 209313. C. Posterior view of Gopherus agassizi carapace showing shape of pygal and perched sulci, MVZ 209313. D. Ventral view of a Gopherus agassizi plastron showing length of the pectoral scale in the midline relative to total length of the plastron, MVZ 209313.