Seraphs chilophorus ( Cossmann, 1889 )

Caze, Bruno, Merle, Didier, Pacaud, Jean-Michel & Saint Martin, Jean-Paul, 2010, First Systematic Study using the Variability of the Residual Colour Patterns: The Case of the Paleogene Seraphsidae (Mollusca, Gastropoda, Stromboidea), Geodiversitas 32 (3), pp. 417-477 : 440-442

publication ID	https://doi.org/ 10.5252/g2010n3a4
persistent identifier	https://treatment.plazi.org/id/03A69848-FF80-1E46-FD3A-FF2AFBB0F970
treatment provided by	Marcus
scientific name	Seraphs chilophorus ( Cossmann, 1889 )
status

Treatment

Seraphs chilophorus ( Cossmann, 1889) View in CoL ( Figs 15 View FIG A-I; 16; 17)

Terebellum (Seraphs) chilophorum Cossmann, 1889: 98 View in CoL , pl. 3, figs 5, 6;

Terebellum (Seraphs) chilophorum View in CoL – Cossmann 1904: 45, pl. 2, fig. 6. — Cossmann & Pissarro 1911: pl. 32, fig. 158-5. — Korobkov 1955: 260, pl. 57, fig. 3. — Glibert 1963: p. 39.

Seraphs chilophorus View in CoL – Jung 1974: 22, pl. 5, figs 12-21, text-fig. 15-16. — Dolin et al. 1980: 28. — Savazzi 1991: 324, fig. 13I, J. — Le Renard 1992: 6. — Le Renard & Pacaud 1995: 112. — Pacaud & Le Renard 1995: 162. — Merle et al. 2008: 198, pl. 25, figs 1a, b, 2.

TYPE LOCALITY. — Fontenay-en-Vexin, Bois du But (Eure, France), Lutetian (Middle Eocene).

TYPE MATERIAL. — Th e illustrated syntype (Bourdot coll., sample Bernay) of Cossmann (1889) has been selected unambiguously by Jung (1974:22) as lectotype, using wrongly the term holotype: “Cossmann’s original figure […]. This specimen is the holotype ”. In accordance with article 74.5 of the ICZN (1999) this mention, made before 2000, constitutes a valid lectotype designation. Unfortunately, the type material of this species has not been found in the Bourdot collection, now deposited at UCBL. A neotype designation is needed to clarify the taxinomic status of this species. A neotype from the locality of Fontenay-en-Vexin ( MNHN A25009 View Materials , Fig.16 View FIG C-E) is accordingly chosen here. This initiative conforms to the rules specified by the ICZN (1999: art. 75), as regards the designation of a neotype.

OTHER MATERIAL EXAMINED. — See Appendix 1.

DESCRIPTION

Shell

Shell up to 28 mm in height and 8 mm in diameter, moderately slender with acute apical part. Aperture long and narrow. Callus of the inner lip well developed and well delineated, continuing adapically on the spire and forming a narrow band parallel to the outer lip ( Fig. 15C View FIG ). Columella bent backwards near the base. Outer lip, slightly thickened and sinuous in labral view, near the adapical end of the aperture. Outer lip extending to the apex and continuing on the opposite side of the apex for a short distance ( Fig. 15G, I View FIG ). Jung called this apical part of the outer lip, the apical canal. Siphonal notch moderately deep on the dorsal side. Surface sculpture of narrow oblique grooves near the base ( Fig. 15H View FIG ).

Colour pattern

The colour pattern is composed of two different dark elements on a lighter background: thick rows of patches nearly perpendicular to the line of growth and tiny dots located between these rows.

The rows are composed of dark triangular patches (7-8). Th e apex of each of is orientated towards the outer lip. Th e patches are usually disconnected and separated by a small white fluorescent patch. This morphology is called a fishbone pattern ( Fig. 16I, J View FIG ) by Meinhardt (1998: fig. 4.10). The distance between the rows and their width are variable. Sometimes, several rows are adjacent to one another ( Fig. 16F View FIG ). Th e dots are small and more or less triangular ( Fig. 16E View FIG ). As for the patches, the apex is always directed towards the outer lip. Th eir size, distribution and shape are heterogenous and irregular. Above the most adapical row, the density and the size of dots are often greater as is the degree of coalescence ( Fig. 16H View FIG ).

COMPARISONS OF THE SHELL MORPHOLOGY

The morphologies of S. chilophorus and S. peterjungi n. sp ( Fig. 15 View FIG J-N) are very similar with their thickened callus of the inner lip and their narrow band on the adapical part of the shell. Moreover, they share an apical canal ( Fig. 15G, I, L View FIG ), lacking in the other Seraphs .

The shell of S. chilophorus is more slender than those of S. volutatus ( Fig. 6 View FIG A-E) and S. sopitus ( Fig. 6F, G View FIG ). Th is species is generally more slen- der than S. olivaceus , although both can have an acute apex. Also, S. chilophorus clearly differs from S. olivaceus , S. volutatus or S. sopitus by the morphology of its outer lip and its callus of the inner lip.

VARIABILITY OF THE COLOUR PATTERN

Among 163 specimens from various localities (11 from the Lutetian and 1 from the Bartonian), 160 (98.16%) show a residual colour pattern under UV light ( Table 1). Accordingly, these observations provide a good general survey of the intraspecific variability.

The residual pattern of S. chilophorus is quite variable ( Fig. 17 View FIG ) and is often subject to significant distortion of the elements on the shell extremities, especially the apical one ( Fig. 17 View FIG C-F).

The huge variability is visible on every element of the residual pattern. Th e number of spiral rows varies from 0 to 6. Several shells show partially or totally connected rows ( Fig. 17B, D View FIG ). Th e shape of the dark patches can show important variations from triangular ( Fig. 17A, C View FIG ) to completely distorted or shapeless ( Fig. 17F, J View FIG ). Although they are usually separated by a small fluorescent patch, they may be connected with each other ( Fig. 17E View FIG ). The density of dots fluctuates from low values ( Fig. 17A View FIG , D-F) to very high ones ( Fig. 17K View FIG ). In this case, the dots form axial rows more or less coalescent ( Fig. 17 View FIG K- N). Th is coalescence sometimes increases until the dots disappear and only axial segments are observable ( Fig. 17H, M, N View FIG ). Th ere are often some large triangular and coalescent patches near the edge of the outer lip. Finally, there are sometimes small axial segments between the dark patches of the rows ( Fig. 17J View FIG ).

In spite of this variability, we can distinguish three morphological types. Th e most abundant an representative type 1 is composed of spiral rows of dark triangles directed towards the outer lip and small dots between them ( Fig. 17 View FIG A-C, I). Th e type 2 shows some thin and tightened axial segments with, often, remnants of spiral rows of triangular patches ( Fig. 17H, N, O View FIG ). Th e type 3 shows only large and more or less coalescent dark triangles ( Fig. 17D, E View FIG ). Several shells bear a morphology intermediate ( Fig. 18 View FIG ) between types 1 and 2 ( Fig. 17 View FIG J-M), between types 1 and 3 ( Fig. 17F View FIG ), between types 2 and 3 ( Fig. 17G View FIG ). Th e relative abundance of these morphologies is given in Figure 18 View FIG . Figure 17 View FIG illustrates this variability with a certain disparity, but the observation of numerous intermediate specimens suggest that it is impossible to separate one type from another, as different species.

COMPARISONS OF THE COLOUR PATTERN

Seraphs chilophorus ( Fig. 16 View FIG ) bears dots, as S. volutatus , S. sopitus , S. olivaceus and S. leukoleptus ( Figs 7-10 View FIG View FIG View FIG View FIG ). Th e pattern of S. chilophorus is, however, easily distinguishable as the dots are composed of only one residual colour and by the occurrence of broad spiral rows of dark patches.