Securininae

Baeza-Carratalá, José F. & Joral, Fernando García, 2014, Crural bases position as a structural criterion for supraspecific diagnosis of Early Jurassic zeilleriid brachiopods, Acta Palaeontologica Polonica 59 (3), pp. 651-661 : 658

Subfamily Securininae nov.

Type genus: Securina Vörös, 1983 .

Diagnosis. — Medium to large-sized shells with triangular outline, biconvex valves, anterior commissure commonly rectimarginate and rarely sulcate, ventral (and frequently dorsal) umbones with extended and sharp beak ridges, demarcating well-developed concave planareas, small pedicle foramen mesothyrid; dental plates relatively long; cardinal process absent; thin and long dorsal median septum connected to a V-shaped septalium, crural bases pendent on the dorsal side of hinge plates; the transversal band of the loop is usually rounded in cross-section.

Stratigraphic and geographic range. — Betic Ranges, Saharan Atlas, Sicily, Apennines, southern Alps, northern calcareous Alps, Hungary, western Carpathians. Sinemurian–Late Pliensbachian (earliest Toarcian?).

Fig. 5. Microphotographs of acetate peels showing hinge plates and crural bases relationship in selected specimens belonging to Bakonyithyris Vörös , → 1983, Aulacothyris Douvillé, 1879 , and Plesiothyris Douvillé, 1879 . A. Bakonyithyris gastaldii ( Parona, 1880) , JdC O-VI-SE-3-4, Pliensbachian, Eastern Subbetic (South-East Spain), section at 1.60 mm from the apex ( A 1), detailed view of the crural bases position ( A 2). B. Aulacothyris resupinata ( Sowerby, 1816) , DPUCM 1-Ar.52.1, Lower Toarcian, Iberian Range (North-East Spain), sections at 2.40 mm ( B 1) and 2.70 mm ( B 2, B 3) from the apex. C. Plesiothyris verneuili ( Deslongchamps, 1863) , DPUCM P.Ve-Cr-1, Pliensbachian, Iberian Range (North-East Spain), sections at 3.80 mm ( C 1) and 5.10 mm C 2, C 3) from the apex. Note, that although the crural bases give place to a conspicuous dorsal thickening, they emerge from a position ventral to the hinge plates (see the detailed views A 2, B 3, C 3).