Pithocerithium gilyandense ( Iljina, 1993 )

Pithocerithium gilyandense ( Iljina, 1993)

Figs 32A–D View FIGURE 32

Cerithium (Thericium) vulgatum Bruguière, 1789 View in CoL — Iljina 1993: 78 (pars), pl. 10, fig. 1 [non Thericium vulgatum (Bruguière, 1792) View in CoL ].

* Cerithium (Thericium) gilyandense L. Iljina View in CoL , sp. nov. — Iljina 1993: 80, pl. 10, figs 9–12.

Cerithium (Thericium) gilyandense View in CoL L. Il’jina, sp. nov.— Iljina 1994: 37, pl. 1, figs 13–14.

Type material. Holotype, PIN 4450/218, Paleontological Institute, Russian Academy of Sciences, Moscow, SL: 18.8 mm, MD: 8 mm; ravine Kiyandy (spelled as ravine Gilyandy in Iljina 1993, 1994) ( Kazakhstan), Middle Miocene, late Konkian, Figs 32A View FIGURE 32 1 –A View FIGURE 1 2 View FIGURE 2 . Paratypes: PIN 5904/63, SL: 20.4 mm, MD: 7.8 mm; ravine Kiyandy ( Kazakhstan), Middle Miocene, late Konkian, Figs 32C View FIGURE 32 1 –C View FIGURE 1 3 View FIGURE 3 . PIN 5904/64, SL: 14.7 mm, MD: 5.4 mm; well Molakuduk ( Kazakhstan), Middle Miocene, late Konkian, Fig. 32D View FIGURE 32 .

Illustrated material. PIN 4450/210, SL: 22.7 mm, MD: 8.1 mm (illustrated in Iljina 1993, pl. 10, fig. 1, as Cerithium (Thericium) vulgatum ), well Molakuduk ( Kazakhstan), Middle Miocene, late Konkian, Fig. 32B View FIGURE 32 .

Description. Medium sized, moderately slender, conical shell of 11 teleoconch whorls, attaining 20–22 mm in height; apical angle ~33–35°. Protoconch unknown. Earliest preserved whorl with two more prominent (probably primary) cords, upper cord delimits angulation at mid-whorl, lower cord runs in the middle between suture and upper cord. Next four to five whorls with close-set spiral cords overrunning prominent axial ribs without distinct nodes, maximum strength mid-whorl, coinciding with adapical primary spiral cord. Primary cords weaken on later whorls, bearing numerous broad secondary spiral bands, separated by narrow grooves, no axial ribs. Three spiral bands with rounded nodes may occur or may be largely reduced. Last whorl high, attaining 47–50% of total height, weakly convex, moderately constricted, typically with five spiral bands intercalated by two to four spiral cords and threads. Large varix opposite the outer lip (position slightly variable); rarely up to three varices or none. Base with two slightly more prominent, smooth cords and numerous narrow cords and threads. One peribasal cord and second stronger cord mid-base.Aperture ovate, not very wide. Columella excavated. Columellar callus forming thick, broad rim, sharply delimited from base. Anal canal distinctly incised, moderately wide, with prominent parietal denticle. Outer lip solid, slightly flaring, without varix. Siphonal canal short, moderately wide, slightly deflected to the left.

Discussion. Sculpture of late teleoconch whorls is highly variable. Few shells develop axial ribs throughout ontogeny, with nodes mid-whorl resulting in a Thericium -like profile. Such shells were erroneously described by Iljina (1993) as Cerithium (Thericium) vulgatum (Bruguière, 1792) ( Fig. 32B View FIGURE 32 ). The morphotype, represented by the holotype, lacks axial ribs but bears numerous low, rounded nodes. This morphotype is dominant in samples from ravine Kiyandy. Morphotypes with reduced nodes and with comparatively more numerous and narrower spirals bands often dominate in samples collected in vicinity of well Molakuduk ( Figs 32C View FIGURE 32 1 –C View FIGURE 1 3 View FIGURE 3 ). These samples yield also strongly sculptured shells [C. (T.) vulgatum sensu Iljina 1993 ] and shells with aberrant sculpture. These shells have two to three angled early teleoconch whorls with densely spaced subequal cords and prominent axial ribs without nodes and pass into late teleoconch whorls covered only by numerous, low, subequal cords ( Fig. 32D View FIGURE 32 ).

Pithocerithium longiuscatum ( Sacco, 1895) , from the Badenian of the Central Paratethys Sea, is superficially similar, but differs in its slightly cyrtoconoid spire and the much larger tubercles.

Iljina (1993) cited Dzhgali ( Georgia) as locality of the species. Three shells with such label are still present in the Paleontological Institute of the Russian Academy of Sciences in Moscow, but the investigations of the Konkian of Dzhgali by A.G. revealed that neither such fauna nor such preservation occur at that locality. The preservation of the shells is the same as from the Ustyurt region and the label is most probably erroneous.

Paleoenvironment. Shallow marine, inner neritic based on the associated fauna (own data A.G.).

Distribution. Late Konkian of the Eastern Paratethys Sea.

Eastern Paratethys. Late Konkian (Middle Miocene): Ciscaucasia : Privol’nyi (Stavropol Krai, Russia); Transcaspian Region: Aksengir Mountain, ravine Kiyandy, near well Molakuduk, Selmidy River (Mangystau Region, Kazakhstan) ( Iljina 1993, hoc opus).