Monteiroconus girondicus ( Peyrot, 1931 )

Harzhauser, Mathias & Landau, Bernard, 2016, A revision of the Neogene Conidae and Conorbidae (Gastropoda) of the Paratethys Sea, Zootaxa 4210 (1), pp. 1-178 : 108-109

Monteiroconus girondicus ( Peyrot, 1931)

Figs 25 C1–C3, 25D1–D3, 17R

Conus (Dendroconus) betulinoides Lamarck mut. girondicus nov. mut—Peyrot 1931: 98, nr. 1170, pl. 3, figs 4–6.

Type material. Holotype illustrated in Peyrot (1931, pl. 3, fig. 5), Aquitaine Basin, Salles (Debat), France; middle Miocene, Serravallian.

Studied material. Bad Vöslau ( Austria): 1 spec. NHMW 2010 /0004/1569a, 1 spec . NHMW 2010/0004/1569b 3 spec. NHMW 2010/0004/1569c, 4 spec. NHMW 2010/0004/1568a–2010/0004/1568d, 2 spec. NHMW 2010/ 0004/1571a–2010/0004/1571b, 1 spec. NHMW 2010/0004/1572.

Illustrated material. Figs 25 C1–C3, 17R: Bad Vöslau ( Austria): SL: 127 mm, MD: 79.5 mm, NHMW 2010/ 0004/1569a; Figs 25 D1–D3: Bad Vöslau ( Austria): SL: 108.6 mm, MD: 62 mm, NHMW 2010/0004/1569b.

Description: Very large and solid species; strongly depressed, nearly flat spire; spire whorls striate with deep concavity in adapical half, becoming more prominent during ontogeny; abapical half of spire whorls bulging; spiral whorls increase regularly in width, last spire whorl not exceptionally broad. Suture impressed. Strongly shouldered with rounded periphery; position of maximum diameter just below shoulder. Subsutural flexure deep, strongly curved, strongly asymmetrical. Last whorl moderately elongate, regularly conical below periphery, not constricted. Slightly allometric growth, fully grown specimens being more elongate than subadults. Weak spiral cords on base and prominent prosocline, straight growth lines on last whorl; fasciole raised, rather narrow, covered by prominent growth lines. Inner lip broad, twisted, glossy well demarcated from fasciole. Aperture moderately wide, only weakly widening abapically; siphonal canal wide, short and straight. No colour pattern preserved.

Shell measurements and ratios. n = 12: largest specimen: SL: 127.0 mm, MD: 79.5 mm, mean SL: 85.9 mm (σ = 5.3), mean MD: 54.4 mm (σ = 10.7), spire angle: µ = 154. 9° (σ = 11.1), last whorl angle: µ = 38.6° (σ = 1.98), LW: µ = 1.6 (σ = 0.08), RD: µ = 0.67 (σ = 0.03), PMD: µ = 0.86 (σ = 0.03), RSH: µ = 0.06 (σ = 0.02).

Discussion. This species is among the largest cone shells of the Paratethys and it is morphologically quite clearly defined. Nevertheless, all specimens were labelled in the NHMW collection as Conus betulinoides Lamarck, 1810 and Conus mercati miocaenicus Sacco, 1893 (= Monteiroconus mojsvari ). In respect to the inventory history, none of the specimens was probably known to Hörnes (1851) and Hoernes & Auinger (1879) and later curators followed a rather broad species concept. A separation from Kalloconus betulinoides ( Lamarck, 1810) is based on the nearly flat spire with deeply concave spire whorls and the comparatively narrow last spire whorl. Monteiroconus mojsvari ( Hoernes & Auinger, 1879) differs in its more conical spire, the shallower concavity on spire whorls and especially in the less prominent shoulder; its fasciole is weaker and the inner lip much narrower. Monteiroconus antiquus ( Lamarck, 1810) , which is of comparable size, differs in its elongate slender outline and basal constriction. Monteiroconus daciae ( Hoernes & Auinger, 1879) can attain a comparable size and also has an almost flat striate spire, but the spire whorls do not have the deep concavity in the adapical half seen in M. girondicus ( Peyrot, 1931) and M. daciae has a shorter, wider last whorl (RD 0.73 vs. 0.67).

Paleoenvironment. All specimens derive from offshore clays in Bad Vöslau, whereas Monteiroconus mojsvari and M. antiquus are typically found in nearshore deposits. This suggests also an ecological separation of these species.

Distribution in Paratethys. Badenian (middle Miocene): Vienna Basin: Bad Vöslau ( Austria).

Northeastern Atlantic : Serravallian (middle Miocene): Aquitaine Basin: Salles (Debat, Minoy) ( Peyrot 1931).

Figures

FIGURE 25 A 1 – A 3. Monteiroconus daciae (Hoernes & Auinger, 1879), Lăpugiu de Sus (Romania), NHMW 1858 / 0043 / 0002, syntype. 25 B 1 – B 3. Monteiroconus daciae (Hoernes & Auinger, 1879), Ritzing (Austria). NHMW 1930 / 0006 / 0034. 25 C 1 – C 3. Monteiroconus girondicus (Peyrot, 1931), Bad Vöslau (Austria), NHMW 2010 / 0004 / 1569 a. 25 D 1 – D 3. Monteiroconus girondicus (Peyrot, 1931), Bad Vöslau (Austria), NHMW 2010 / 0004 / 1569 b. 25 E 1 – E 2,. Monteiroconus mojsvari (Hoernes & Auinger, 1879), Pötzleinsdorf (Austria), NHMW 1847 / 0037 / 0024. 25 F 1 – F 2. Monteiroconus mojsvari (Hoernes & Auinger, 1879), Gainfarn (Austria), NHMW 1853 / 0010 / 0001, syntype.