Table 2 in Late Viséan (late Mississippian) ammonoids from the Barnett Shale, Sierra Diablo Escarpment, Culberson County, Texas, USA

Table 2. Conch ontogeny of Girtyoceras meslerianum (Girty, 1909); based on material from Jackfork Creek, Oklahoma (Fig. 7).
dmConch shapeWhorl cross section shapeAperture1.5 mmthickly discoidal; subevolutemoderately depressed; moderately embracinglow(ww / dm = 0.45–0.60; uw / dm = 0.40–(ww / wh 1.80–2.00; IZR = 0.20–0.25)(WER ∼ 1.65)0.45)5 mmthickly discoidal; evolutestrongly depressed; moderately embracinglow(ww / dm = 0.55–0.50; uw / dm = 0.50–(ww / wh = 2.25–2.50; IZR = 0.25–0.30)(WER = 1.50–1.60)0.55)10 mmthickly discoidal; subevoluteweakly depressed; strongly embracingmoderate(ww / dm = 0.50; uw / dm = 0.35)(ww / wh = 1.25; IZR = 0.35–0.40)(WER = 1.75–1.90)20 mmthinly discoidal; subinvoluteweakly compressed; strongly embracinghigh(ww / dm ∼ 0.45; uw / dm ∼ 0.20)(ww / wh = 0.80; IZR ∼ 0.40)(WER ∼ 2.10)