Conus torulosus

Conus torulosus (Millet, 1866)

Descrizione originale del Conus torulosus:

Coq.de moyenne taille, à spire élevée, conique, composée de 11-12 tours creusés en gouttière et bordés chacun d’un cordonnet arrondi; le dernier tour présente à sa base, 7-8 petits sillons placés obliquement. Longueur: 25-26 millimètres; diamèter: 13-14 millimètres, Th, Sc.’ (Millet, 1865, p. 586).

Discussion – This small Conilithes species was identified as Conus dujardini Deshayes, 1845 by Brébion (1964, p. 630), which was shown to be a junior synonym of C. exaltatus Eichwald, 1830 by Harzhauser & Landau (2016, p. 52). It has the same type of tall multispiral protoconch. However, the French Tortonian shells are half the usual size for C. exaltatus, the spire is not as tall or scalate and the siphonal canal is shorter. The tubercles present on the neanic whorls of C. exaltatus do extend more than the first 3-4 teleoconch whorls, whereas in the French species they persist onto the 6-7 whorl. The spiral grooves cover more of the base in C. exaltatus, whereas in the French species they are only present over the lower third of the last whorl. Finally, few shells from Assemblage I preserve any sort of colour pattern, even under UV light.

This French cone is an exception with a broad light horizontal band placed mid-whorl on the last whorl enhanced under UV light. This pattern is different from that seen in C. brezinae (Hoernes & Auinger, 1879) that has narrow interrupted horizontal stripes (Harzhauser & Landau, 2016, fig. 5H1). They are nevertheless closely affiliated species; the couple of fine spiral grooves below the carina on the last whorl described by Harzhauser & Landau (2016) in C. exaltatus can also be seen in this species (Pl. 1, fig. 2). Conilithes exaltatus is widely distributed in the Miocene Paratethys (Harzhauser & Landau, 2016), and is also present Miocene eastern Atlantic frontage and Proto-Mediterranean, although these records need to be revised as there is confusion in the literature between the various Conilithes species such as C. brezinae.

Conilithes brezinae differs from C. exaltatus in having a stronger shoulder, which is less sharp and placed lower, a wider subsutural ramp on the last whorl, spiral grooves confined to the base, and a shorter siphonal canal that s less constricted. The French species shares with C. brezinae the shorter base and the grooves confined to this area, but differs in having a much shorter spire than either C. exaltatus or C. brezinae, and the tubercles on the early spire whorls persist longer than in either of the other two species. Conilithes brezinae is also widely distributed in the Miocene Paratethys (Harzhauser & Landau, 2016), and may also be present in the Miocene eastern Atlantic frontage and Proto-Mediterranean, but a revision of the group is required ⁽¹⁾.

Questa piccola specie di Conilithes è stata identificata come Conus dujardini Deshayes, 1845 da Brébion (1964, p. 630), che è stato dimostrato essere un sinonimo junior di C. exaltatus Eichwald, 1830 da Harzhauser & Landau (2016, p. 52). Ha lo stesso tipo di protoconca alta multispirale. Tuttavia, le conchiglie del Tortoniano francese sono la metà delle dimensioni abituali del C. exaltatus, la guglia non è così alta o scalata e il canale sifonale è più corto. I tubercoli presenti sui verticilli neanici del C. exaltatus si estendono oltre i primi 3-4 verticilli della teleoconca, mentre nelle specie francesi persistono sui 6-7 verticilli. I solchi a spirale ricoprono maggiormente la base nel C. exaltatus, mentre nelle specie francesi sono presenti solo nel terzo inferiore dell'ultimo giro. Infine, alcuni gusci di Assemblage I conservano qualsiasi tipo di motivo di colore, anche sotto la luce UV.

Questo cono francese è un'eccezione con un'ampia fascia orizzontale chiara posta a metà della spirale sull'ultima spirale evidenziata dalla luce UV. Questo modello è diverso da quello osservato nel C. brezinae (Hoernes & Auinger, 1879) che ha strisce orizzontali interrotte (Harzhauser & Landau, 2016, fig. 5H1). Sono tuttavia specie strettamente affiliate; in questa specie è riscontrabile anche la coppia di sottili solchi a spirale sotto la carena sull'ultimo giro descritti da Harzhauser & Landau (2016) nel C. exaltatus (Tav. 1, fig. 2). Conilithes exaltatus è ampiamente distribuito nel Miocene Paratethys (Harzhauser & Landau, 2016), ed è presente anche sulla facciata dell'Atlantico orientale del Miocene e Proto-Mediterraneo, anche se queste registrazioni necessitano di essere riviste in quanto vi è confusione in letteratura tra le varie specie di Conilithes come C. brezinae.

Conilithes brezinae differisce da C. exaltatus per avere una spalla più forte, meno affilata e posta più in basso, una rampa subsuturale più ampia sull'ultimo giro, solchi spirali confinati alla base e un canale sifonale più corto che è meno ristretto. La specie francese condivide con C. brezinae la base più corta e i solchi confinati in quest'area, ma differisce per avere una spira molto più corta sia di C. exaltatus che di C. brezinae, e i tubercoli sui primi giri della spira persistono più a lungo che in entrambi. delle altre due specie. Conilithes brezinae è ampiamente distribuito anche nel Miocene Paratethys (Harzhauser & Landau, 2016), e potrebbe essere presente anche nella facciata miocenica dell'Atlantico orientale e nel Proto-Mediterraneo, ma è necessaria una revisione del gruppo ⁽¹⁾.

Fortunately, Millet (1854, 1865) recognised this upper Miocene French form to be distinct and erected the name C. torulosus (1854, p. 160; nomen nudum), later validated by a description (Millet, 1865, p. 586). We therefore resurrect Millet’s name for this French fossil species; Conilithes torulosus (Millet, 1865).

The specimens from the Atlantic middle Miocene Langhian of the Loire Basin illustrated by Glibert (1952a, pl. 12 figs 11a-c) as C. dujardini (= C. exaltatus) are problematic and may represent two species. His figure 11a shows a form similar to C. torulosus with a relatively low spire and short last whorl and might represent this species. The Loire Basin specimens illustrated by Vaessen (2010, figs 2-4) are almost certainly C. torulosus. Glibert (1952a, figs 11b, c) shows a shell with a scalate spire, strongly beaded carina persisting onto the last whorl and relatively long last whorl of which at least the lower two-thirds are spirally grooved ⁽¹⁾. This shell is more like a small form of C. antidiluvianus.

Other European Miocene congeners such as C. allioni (Michelotti, 1847), C. eichwaldi Harzhauser & Landau, 2016 and C. sceptophorus (Boettger, 1887) can be separated by their more rounded shoulder, and hence more pyriform shape. The type species, C. antidiluvianus (Bruguière, 1792) is a much larger shell with an elongated last whorl, strongly scalate spire consisting of angular whorls and the strong carina is beaded to the last whorl in most specimens.

As mentioned earlier, this group outside the Paratethys needs revision. It may well be that under closer scrutiny this group consists of allied species rather than one or two variable ones as interpreted by previous authors (i.e.

Glibert, 1952a; Vaessen, 2010).

We therefore provisionally restrict C. torulosus to the middle and upper Miocene of NW France. In Assemblage I it occurs at all localities (Renauleau, Sceaux-d’Anjou, Thorigné, St-Michel, St-Clément-de-la-Place, Beaulieu, les Pierres Blanches; Brébion, 1964, p. 631).

Distribution – Middle Miocene: Atlantic (Langhian), Loire Basin (Glibert, 1952a; Vaessen, 2010). Upper Miocene (Tortonian): Atlantic, NW France (Millet, 1854, 1865; Brébion, 1964).

Figure 1. Principal components analysis (PCA) based on shell measurements of specimens of four Conilithes species (NHMW collection + Table 1). A: shell ratios, B: shell measurements. A separation of C. torulosus, C. antidiluvianus, C. exaltatus and C.brezinae is evident in both analyses. For measurement abbreviations see legend Table X (adapted from Harzhauser & Landau, 2016, fig. 7).

Plate 1. Conilithes torulosus (Millet, 1865); ⁽¹⁾

1. NHMW 2016/0103/1297, height 24.2 mm, width 11.7 mm, 1d, detail of subsutural flexure;

NHMW 2016/0103/1230 (juvenile), detail of protoconch (SEM image). Le Grand Chauvereau, St-Clément-de-la-Place.
NHMW 2016/0103/1886, height 28.4 mm, width 12.8 mm;
NHMW 2016/0103/1887, height 25.1 mm, width 11.2 mm;
NHMW 2016/0103/1888, height 23.1 mm, width 10.6 mm;
NHMW 2016/0103/1889, height 20.4 mm, width 9.0 mm;

7. NHMW 2016/0103/1890, height 21.1 mm, width 9.9 mm.

Renauleau, Maine-et-Loire, NW France, Tortonian, upper Miocene.

Le località indicate per il Conus torulosus, indicato come sinonimo del Conus dujardini, sono Genneteil, la Beurelière e Breil-de-Foin

A – B. PCA based on shell measurements of specimens of 3 Conilithes species (NHMW collection, Table 1). A: shell ratios, B: shell measurements. A separation of C. antidiluvianus, C. exaltatus and C. brezinae is evident in both analyses. The measurements for the lectotype of C. dujardini and the syntype of C. exaltatus were taken from the illustrations in Eichwald (1952) and Dubois de Montpéreux (1831). SL = shell length, AH = apertural height, HMD: height of maximum diameter, SA = spire angle, LWA = angle of the last whorl, LW = length width ratio, RD = relative diameter, RSH = relative height of spire. ⁽⁴⁾