Dorsetensia? sp., 1892

Sandoval, José, 2022, Sonniniidae Ammonitina, Middle Jurassic from Southern Spain: taxonomic, biostratigraphical and palaeobiogeographical analysis, Geodiversitas 44 (27), pp. 801-851 : 842-843

Dorsetensia? sp. [M]

( Fig. 14T )

MATERIAL EXAMINED. — JAC22.57.3 .

MEASUREMENTS. — See Table 27.

DESCRIPTION

Moderately evolute, whorl section compressed subrectangular with a low umbilical wall that almost matches the rounded umbilical edge. The flanks are gently convex and the ventral area is weakly tabulated with a moderately developed keel. The ribs, arising near the umbilical edge, somewhat irregular in thickness, are mainly simple but some tend to join in pairs near their base. Radial or only barely sinuous, they bend forward at the ventral edge. The ribbing weakens but does not disappear in the BC. The suture is not preserved.

REMARKS

The specimen described above displays common characters with Witchellia gr. laeviuscula (J. de C. Sowerby, 1824) and some primitive Dorsetensia such as D. pinguis ( Roemer, 1836) , D. hannoverana ( Hiltermann, 1939) , and D. hebridica Morton. W. laeviuscula has a similar ribbing style, but is more involute and has greater whorl expansion. Also, the section is subtriangular instead of subrectangular. Dorsetensia gr. pinguis specimens have similar coiling, but usually have more developed ribbing.

DISTRIBUTION

This specimen is from the upper part of the Laeviuscula Zone, and is therefore older than D. gr. pinguis , from the JAC22 section, Campillo de Arenas (Jaén Province).

Figures

FIG. 14. — A-E, Witchellia peleka (Buckman, 1923) [m]: A, TT.76.1, Ovale? Zone, Sierra de Alta Coloma;B, JA13.34.2,Ovale Zone, Sierra de Alta Coloma (JAC13 section); C, JAQ1.(-15).1, Ovale Zone, Barranco de Agua Larga (JAQ1 section); D, JSP1, Ovale Zone, Sierra de San Pedro, Jaén province; E, MOD.R.1, Ovale Zone?, Montillana, (MOD section); F-I, Witchellia macer (Buckman, 1889) [m]; F, FAa.4.1, Laeviuscula Zone?, Sierra de Alta Coloma área; G, JVM.42, bed with ammonite of the Laeviuscula and Propinquans zones, La Martinica section; H, JST.93.6, Laeviuscula Zone, Sierra del Trigo, Jaén province; I, JAC22.49.1, Laeviuscula Subzone, Sierra de Alta Coloma (JAC22 section); J, Witchellia minima (Hiltermann, 1939) [m], JAC22.43.26, Laeviuscula Zone, Trigonalis Subzone, Sierra de Alta Coloma (JAC22 section); K-O, Witchellia moisyi (Brasil, 1893) [m]; K, JAC11.6?.7, Laeviuscula Zone?, Sierra de Alta Coloma, (JAC11 section); L, M, JAC6.R.14, JAC6.R.7, Propinquans Zone, Sierra de Alta Coloma área, (JAC6 section); N, O, JAQ1.67.2, JAQ1.67.1, Propinquans Zone, Barranco de Agua Larga (JAQ1 section);P, Q, Dorsetensia liostraca Buckman,1892 [M], JGa8.32.4,JGa8.32.2,Humphriesianum Zone,Romani Subzone,Sierra de Gaena (sections, JGa2);R, S, Dorsetensia hebridica Morton,1972 [M];R, JAC3.118.4,Propinquans Zone,Hebridica Subzone,Sierra de Alta Coloma (JAC3 section);S, JAC3’.22.44,