Figure 7 in Late Viséan (late Mississippian) ammonoids from the Barnett Shale, Sierra Diablo Escarpment, Culberson County, Texas, USA

Figure 7. Girtyoceras meslerianum (Girty, 1909), conch cross sections and ontogenetic trajectories of material from the Caney Shale of Jackfork Creek near Ada, Oklahoma (a–d). (a) Specimen MB.C.25466; × 2.5. (b) Specimen MB.C.25467; × 2.5. (c) Specimen MB.C.25468; × 2.5. (d) Specimen MB.C.25469; × 2.5. (e–g), ontogenetic development of the conch width index (ww / dm), umbilical width index (uw / dm), and WER of the sectioned specimens and type material.