Conasprella paupera (Harzhauser et. al., 2018)

 Descrizione

Diagnosis:

Small Conasprella species with broad, stout shell, low spire, beaded shoulder, and sculpture of well-developed spiral cords separated by broad grooves, with strong, opisthocyrt growth lines visible in grooves. Subsutural flexure shallow, symmetrically curved.

Description:

Shell small, solid, squat, broad biconic, with moderately low spire. Protoconch missing or largely abraded. Teleoconch comprising up to 8.5 whorls with narrow, weakly concave subsutural ramp, periphery placed just above  suture, exposing well-defined, rounded to slightly spirally elongate beads at shoulder. Spire whorls with three or four finely granulated spiral cords on subsutural ramp, axial sculpture covering spiral cords and interspaces. Subsutural flexure shallow, symmetrically curved. Last whorl angular at shoulder, slightly convex below, hardly constricted at base, bearing about 20 flattened spiral cords separated by relatively wide interspaces, crossed by densely spaced, opisthocyrt growth lines that are strongest in interspaces, but in some specimens override spiral cords. Siphonal fasciole short, not delimited, weakly recurved. Aperture narrow with parallel margins. Spiral cords slightly lighter coloured than interspaces under UV light, especially beaded cord along periphery.

Remarks:

Martin and Beets identified this taxon as Conus acutangulus (Lamarck, 1810) and Nuttall in Sandal (1996) figured a specimen from the Seria Fm. at Penanjong beach under the same name. Conasprella acutangulus is an extant species well represented also in the SE Asian Miocene. It is much larger and juveniles the size of the Seria Fm. specimens are much narrower with a higher more pointed spire and have spiral grooves instead of relatively wide interspaces.

Conasprella gembacana Martin, 1884 from unnamed Miocene beds at Ngembak in Java is more slender, has a higher straight-sided spire, has larger nodes on the shoulder, has spiral cords with nodes and lacks the spiral furrows.

Distribution:

Only known from the Middle Miocene of Sarawak and the late Miocene of Brunei Darussalam.

Stratum typicum: Seria Fm.

Type locality: Ambug Hill, Brunei Darussalam.

Age: Late Miocene, Tortonian.

Name: Referring to the small size of the species.

Auch diese Art, obwohl etwas verdruckt, ist wegen ihrer charakteristischen Sculpturen nicht zu verkennen. Die flachen Umgange des kegelformigen Gewindes sind gekront; ausserdem tragen sie sechs bis sieben Reihen feiner Knotehen. Die Schlusswindung ist seharf geknickt und in ihrer ganzen Ausdehnung mit tief eingeschnittenen Quer-Furchen bedeckt, in deren Zwischenraumen eine feine Langsstreifung sichtbar wird ⁽²⁾.

Exemplare von Banka und den  Molukken stimmen bis ins kleinste Detail hiemit uberein ⁽²⁾.

Ein einziges fossiles Individuum  ist vorhanden.  Fundort: 0 ⁽²⁾.

This type, although somewhat printed, cannot be missed because of its characteristic sculptures. The flat edges of the conical thread are crowned; They also have six to seven rows of fine knotted knots. The final turn is sharply bent and covered over its entire extent with deeply cut transverse furrows, in the spaces between which a fine longitudinal striation is visible ⁽²⁾.

Specimens from Banka and the Moluccas agree with this down to the smallest detail ⁽²⁾.

A single fossil individual is present. Location: 0 ⁽²⁾.

Conus acutangulus (Lamarck, 1810)

A single specimen from the Pleistocene marls of Santo, New Hebrides (station SM242), is referred to C. acutangulus. The fossil is larger than the average Holocene shells but shows well-developed nodes along the shoulder of the whorls. The figured specimen from the New Hebrides (pl. 25, figs. 5, 6) measures: length 29.7 mm, diameter 14.5 mm. A shell was also identified from the Miocene of Fiji (pl. 25, figs. 3, 4). It (USNM 214321) measures 15.5 mm in length. C. acutangulus lives in abundance today in the Philippines and has been collected in Hawaii and in the Society Islands ⁽³⁾.

According to Vlerk (1931, p. 213)⁽⁴⁾, it has been reported from the upper Miocene and Pliocene in several parts of Indonesia ⁽³⁾:

Conus acutangulus Chemn. ⁽⁴⁾

Upp. Mioc. (Tjilanang-beds) Java, Bibl. 30, p. 48 and Bibl. 59, p. 13;

Upp. Mioc. S. Sumatra, Bibl. 84,p. 105;

Plioc. Timor, Bibl. 74, p. 17;

Plioc. Seran, Bibl. 14,p. 105;

Plioc. N. Sumatra, Bibl. 62, p. 13;

recent

14. Fischer, P. J. Beitrag zur Kenntnis der Pliozan-Fauna der Molukken-inseln Seran und Obi. Palaontologie von Timor, Lief. XV, Abh. 25, 1927, p. 1—179, mit 6 Tafeln.

30. Martin, K. Paleontologische Ergebnisse von Tiefbohrungen auf Java, nebst allgemeineren Studiën über das Tertiaer von Java, Timor und einiger anderer Insein. Samml. Geol. Reichsmus. LeioYn, Ser. I, Bd. III, 1883—1887, p. 1—380, mit 15 Tafeln (= Jaarb. Mjjnw. 1883, Wet. Ged., p. 371—412, 1884, Wet. Ged., p. 77—216, 1885, Wet. Ged., p. 5—108, 1887, Wet. Ged., p. 253—342).

59. Martin, K. Die Fossilien von Java. Samml. Geol. Eeichsmus. Leiden, Neue Folge, Bd. I, 1891—1922, p. 1—538, mit 63 Tafeln (p. 446—470 = Bibl. 57).

62. Martin, K. Mollusken aus dem Neogen von Atjeh in Sumatra. Wet. Meded. Dienst Mijnbouw, No. 10, 1928, p. 1—35, met 1 pi.

74. Tesch, P. Jungtertiare und quartare Mollusken von Timor. In: J. Wanner, Paleontologie von Timor: 1. Lief. V; 2. Lief. VIII, 1915 und 1920, p. 1—68, mit 10 Tafeln und p. 41—121, mit 10 Tafeln

84. Zwierzycki, J. Voorloopig onderzoek van fossielen, afkomstig van eenige vindplaatsen op Sumatra. Jaarboek Mijnwezen Nederlandsch Oost-Indie, 1913, Verh. p. 101 —129.

Bibliografia

• (1) - Late Miocene gastropods from northern Borneo (Brunei Darussalam, Seria Formation) by Mathias Harzhauser, Han Raven, Bernard M. Landau, László Kocsis, Asiqqin Adnan, Martin Zuschin, Oleg Mandic & Antonino Briguglio

• (2) - Die tertiarschichten auf Java – Martin 1879

• (3) - CENOZOIC FOSSIL MOLLUSKS FROM WESTERN PACIFIC ISLANDS; GASTROPODS (EULIMIDAE AND VOLUTIDAE THROUGH TEREBRIDAE) By HARRY S. LADD

• (4) - Caenozoic Amphineura, Gastropoda, Lamellibranchiata, Scaphopoda by I.M. Van Der Vlerk