Thericium crenulosum
Creators: name: Sacchetti, Claudia
name: Landau, Bernard
name: Ávila, Sérgio P.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Neotaenioglossa
Cerithiidae
Thericium
Thericium crenulosum

description: Thericium crenulosum (Bronn, 1862)
Plate 1 F 1 -F 2
* Cerithium crenulosus Bronn in Reiss 1862: 30, pl. 1, fig. 12.
Cerithium crenulosus Bronn — Mayer 1864: 64: 6, fig. 43 (in text fig. 46; lapsus).
Cerithium crenulosum Bronn, 1862 — Dávid et al. 2021: 5.
Type material. Single specimen height 22.0 mm, width 6.5 mm, Pinheiros, Santa Maria Island, Azores; whereabouts unknown (Beu 2017: 165).
Santa Maria material examined. Maximum height 10.0 mm, width 6.0 mm. One specimen from LNEG collection, (unnumbered), Ponta do Norte lighthouse, Santa Maria Island, Azores, Touril Complex, Lower Pliocene.
Original description. “ Einige unvollständige Exemplare von 1¼-1½" Länge und kaum ̧ber ¼ so viel Dicke, rein Kegel f̂rmig, mit Ausnahme eines beim stärksten Individuum vorhandenen älteren Mundwulstes und des schiefen wulstigen und nach hinten etwas verlängerten Vorsprungs, den die äussere Lippe selbst bildet. Umgänge 10-12. Naht wenig vertieft. Im Übrigen ist die Art von andern hauptsächlich durch ihre Streifung verschieden, welche durch viele dichte abwechselnd etwas ungleiche sehr tief und scharf eingeschnittene Spirallinien und durch eine oft nur wenig schwächre, aber ebenfalls mehr als geŵhnlich dichte scharfe und etwas gebogeue ZuwachsStreifung gebildet wird. Die Zahl dieser Spiralstreifen beträgt auf den Umgängen des Gewindes 5 stärkere und eben so viele abwechselnd feinere, die mitunter ausbleiben; auf dem letzten Umgange steigt deren Gesammtzahl bis auf 25, von welchen manche noch etwas zweitheilig sind. Sie bilden mit dem Zuwachs-Streifen gemeinsam eine sehr fein, aber scharf gek̂rnelte Oberfläche. Der hinterste dieser eingeschnittenen Streifen ist stärker, mehr und weniger von der Naht entfernt, und schneidet so ein hinteres ebenfalls queer und selten noch einmal längsgestreiftes Band ab, das an manchen Exemplaren knotig wird, mit 20 Knoten auf dem Umgang. Zuweilen ist auch noch ein älterer Mundwulst sichtbar. (Das Innere der M̧ndung ver. deckt.) Der Kanal kurz, schwach. Steht der Wiener Varietät des C. crenatum und einer neuen Art aus dem Aquitanien von Saucats am nächsten [Some incomplete specimens of 1¼-1½" [inches?] length and barely more than ¼ as much wide, cone-shaped, with the exception of an apertural bulge present in the largest individual and the crooked posterior bulge and elongated protrusion formed at the outer lip. Ten-twelve whorls. Suture slightly deepened. This species is different from others mainly by its striation, which are formed by many dense, very deep, sharply incised, slightly unequal, alternating spiral lines and by an often only slightly weaker, but also more than usually dense sharp and somewhat curved growth lines. The number of these spirals on the whorls is 5 stronger ones and as many alternately finer ones, which are sometimes missing; on the last whorl, their total number rises up to 25, of which some are even a bit divided. Together with the growth lines, they form a very fine, but sharply granular surface. The subsutural is stronger, slightly distant from the suture, and thus cuts off the posterior also oblique and rarely also the longitudinally striped band, which becomes tubercular on some specimens, with 20 tubercles per whorl. Sometimes the apertural bulge is also visible. (The inside of the aperture is obscured.] The siphonal canal short, weak. The species is closest to the Vienna variety of C. crenatum and to a new species from the Aquitanian of Saucats.]” (Bronn in Reiss 1862: 30).
Latin description. “ Testa turrita, subulata; anfractibus10-12,marginatis,raro varicosis, zona suturali nodulosa, succinctis, transversim sulcatis, sulcis angustis, profundis, impressis, irregulariter alternantibus, majoribus 6-8; striis incrementi tenuibus, decussato-subgranulosis; apertura satisparva, rotundato-quadrangulari.” (Mayer 1864: 64).
Revised description. Shell small for genus, cerithiform, with tall regularly conical spire. Protoconch not preserved. Teleoconch of nine almost straight sided whorls with periphery at abapical suture. Suture linear weakly impressed. Sculpture of low, narrow, slightly arcuate, opisthocline ribs cut by numerous fine spiral cords, giving surface finely beaded appearance. Subsutural cord slightly wider and stronger abapically. Last whorl 43% of total height, weakly convex in profile, with varix placed opposite aperture, subsutural cord poorly defined, numerous spirals forming finely beaded sculpture, including three spirals over the subsutural cord. Aperture pyriform (medial side of aperture and siphonal fasciole obscured by matrix), outer lip thickened, columellar and parietal calluses strongly thickened, forming relatively broad callus rim.
Discussion. Thericium crenulosum (Bronn, 1862) is characterized by its very small size for the genus and finely beaded spiral sculpture. The specimens at hand do not seem juvenile, as the outer lip is fully thickened. They are more similar to T. crenatum (Brocchi, 1814) but are much smaller and the sculpture is even finer. The spirals in T. crenulosum are of sub-equal strength, whereas in T. crenatum they are of distinctly primary to tertiary strength and more coarsely beaded.
Distribution. Lower Pliocene: Atlantic, Santa Maria Island, Azores (Bronn in Reiss 1862; Mayer 1864).
description: Published as part of Sacchetti, Claudia, Landau, Bernard & Ávila, Sérgio P., 2023, The Lower Pliocene marine gastropods of Santa Maria Island, Azores: Taxonomy and palaeobiogeographic implications, pp. 1-150 in Zootaxa 5295 (1) on pages 28-29, DOI: 10.11646/zootaxa.5295.1.1, http://zenodo.org/record/7965273