Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 75. (Budapest 1983)
Szabó, J.: Lower and Middle Jurassic Gastropods from the Bakony Mountains (Hungary). Part V.: Supplement to Archaeogastropoda; Caenogastropoda
Genus MATUR/FUSUS gen. n. Type species: Maturifusus densicostatus sp. n. — Derivatio nominis: maturus(Lat.) = early (figuratively); fusus (Lat.) — spindle. Diagnosis : fusiform shell with moderately high spire, convex whorls and deep suture. The periphery is rounded, the base is concave along the columella. The aperture is axially elongated, with a connected rather long siphonal canal. In the parietal and columellar region a thin callus, appearing in a narrow zone, may occur. The ornament consists of strong collabral ribs or folds, and spiral cords and threads. The intersections of the two differently directed ornamental elements may bear tiny tubercles. The shell-structure and the embryonal shell are unknown. Distribution — France. Montreuil-Bellay ; Bakony Mts. : Middle Jurassic. Remarks — The majority of the similarly-shaped genera belongs into the family Buccinidae, of which most similar are forms in the Pleistocene to Recent Plicifusus and itssubgenera. Naturally, the great temporal distance makes any closer relation unprobable, the similarity can be regarded rather as a subjective basis for the arrangement of Maturifusus. Further material and studies are needed to determine the exact systematic position and tounderstand the early evolution of the siphonostom caenogastropods (Neogastropoda). Cymatiidae is an other family comprising similar genera, but most of these bear columellar teeth and folds, usually together with thick parietal and/or columellar callus. These features are missing in the here described new genus. Apart from the type species, Maturifusus piettei (HÉBERT et DESLONGCHAMPS, 1860> certainly belongs into this genus. The generic arrangement of other fusiform species occurring more or less continuously from the Upper Triassic to the Middle Cretaceous needs further investigations. Maturifusus densicostatus sp. n. (Plate III: fig. 14) H o 1 o t y p u s : Plate III : fig. 14. — Locus typicus: Bakonybél, Somhegy. — Stratum t y p i c u m : limestone infilling horizontal fissure. — Derivatio nominis: dense (Lat.) = close, dense; costa (Lat.) = rib. Diagnosis : closely-situated sharp ribs suture to suture; spiral cords, between them spiral threads on the whorls and only spiral threads on the base; tiny tubercles on the intersecting points of the ribs and cords; thin, membranaceous parietal and columellar callus. Measurements H HL HA D W A Plate III: fig. 14. — — — 11 5 57-37° Material — Two damaged specimens with shell. Shape— Dextral, high, fusiform shell with cyrtoconoid spire. The whorls are convex, the outline of the base is concave along the columella. The aperture is elongated, and, on the basis of one cross-section, the ca. one-third of its height is formed by the siphonal canal. Along the inner lip a thin lamella covers the previously-built shell-parts, and this lamella does not hide the unevennesses caused by the former ornament, either. Non-umbilicated. Ornament — The whorls and the adapical margin of the base is covered by spiral cords with spiral threads running in between. Only these latters occur in the narrow subsutural zone, and on the lower part of the base. The transverse ornament is formed by strong ribs running parallel to the prosocyrt growth lines, which reach suture to suture and on the last whorl to the upper margin of the base. On the edges of the ribs, where the spiral cords are intersected, tiny tubercles can be seen. Embryonal shape and ornament — The shape of the earliest whorl does not differ from that of the other ones, and the difference in the ornament appears only as the decreased number of the elements. This is the second whorl at most, in the case of same coiling on the embryonal shell and the teleoconch, thus could be a one-whorl different portion altogether. If the coiling was different from that of the preserved shell parts, greater differences could have been present. Distribution — Bakony Mts.. Somhegy : condensed Subfurcatum and Garantiana Zones. Subclass uncertain Remarks — Maturifusus piettei (HÉBERT et DESLONGCHAMPS, 1860) is closely similar, but differs in having non-cyrtoconoid spire, lower whorls, smaller number of ribs per whorl, ribs, which are nearly straight and are rather undulatious, blunt, non-tuberculate, and equal spiral sculpture, while in Maturifusus densicostatus sp. n. cords and threads, alternate.
