SONINNIINAE Buckman, 1892

Sandoval, José, 2022, Sonniniidae Ammonitina, Middle Jurassic from Southern Spain: taxonomic, biostratigraphical and palaeobiogeographical analysis, Geodiversitas 44 (27), pp. 801-851 : 808

Subfamily SONINNIINAE Buckman, 1892

DESCRIPTION

Serpenticone, platycone to oxycone macroconchs, sometimes reaching large sizes, microconchs being much smaller. Whorl sections vary from subrectangular, subtriangular, oval to ogival, and the venter has a more or less developed hollow keel persisting to the BC. Ornamentation varies widely from smooth forms, to others with strongly ribbed or ribbed and tuberculate. The innermost whorls can be smooth, whereas later inner whorls have ribs. Many forms have well-developed tubercles or spines. The degree to which the spinose/tuberculate stage persists is highly variable and specimens rarely retain strong ribbing beyond the end of the PH, whereas in others the ornamentation is reduced to the inner whorls and from an early stage are striated or smooth. Complete macroconchs [M] have simple peristomes with plain mouth borders. In microconchs [m], the aperture morphology is variable, but usually they have expanded lateral lappets. Like the corresponding macroconchs, microconchs can have nontuberculate, tuberculate, and even spiny internal whorls. The septal suture is relatively complex, with a ramified deep L, and slightly retracted U 2 -U 5 lobes.

REMARKS

As mentioned above, Asthenoceras , Fontannesia , Newmarracarroceras , and Dorsetensia , all included within Sonniniinae in the new version of the Treatise ( Howarth 2013), should be separated from this subfamily and transferred to Grammoceratinae (the first three) and Witchelliinae (the last). The more common dimorphism of Sonniniinae appears to belong to the aforementioned type 1, i.e. large, “classical” macroconchs associated with relatively small macroconchs (mesoconchs according to Chandler 2019) with plain mouth borders and without lateral lappets. Coexisting with Sonninia [M] and Sonninites [M], microconchiate forms also occur with welldeveloped lateral lappets (aforementioned dimorphism type 2, possibly representing their dimorphic partners. In this case, the two types of dimorphism would be clearly represented in this subfamily.

DISTRIBUTION

Sonniniinae range throughout the Upper Aalenian (Concavum Zone)-Lower Bajocian (Humphriesianum Zone) interval, with a worldwide distribution, except in the Boreal Realm. In the Subbetic domain, they have this stratigraphic range, and occur in the External, Median, and Internal subdomains, being most abundant in the central sector of the Median Subbetic, the origin of most of the specimens studied here.