Janthina krejcii, Beu, 2017

Beu, Alan G., 2017, Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae), Records of the Australian Museum (Rec. Aust. Mus.) 69 (3), pp. 119-222 : 173-175

Janthina krejcii sp. nov.

Figs 26A–N

Hartungia typica Bronn. – Bronn, 1862: 32–33 (in part misidentified as H. typica Bronn, 1861 ).

Janthina typica (Bronn) .– Krejci-Graf et al., 1958: 336, pl. 3, fig. 6, pl. 4, fig. 11 (misidentification).

Type material. Holotype SMF 10135a ( Figs 26A–B, D–E ), with two paratypes SMF 10135b–c ( Figs 26C, F–H ), labelled “ Azoren, Santa Maria, Wegknick [road bend] bei Praia, K. Krejci-Graf,” 23 April 1955, in SMF. The type locality is the upper, seaward-directed hairpin bend on the road descending from Almagreira to the beach at Praia, Santa Maria Island , illustrated by Krejci-Graf et al. (1958: fig. 4) (a lower, landward-directed hairpin bend is in the underlying volcanic rocks). The writer visited the pale grey outcrop labelled “ Janthina find-point alongside the collectors” in fig. 4 of Krejci-Graf et al. (1958) with Bernard Landau on 28 Feb 1998, but found no calcareous fossils. The matrix proved non-calcareous, and is not datable by microfossils; it lacks Foraminifera, Radiolaria, calcareous nannofossils and dinoflagellate cysts. Evidently Krejci-Graf’s party sampled a last small pocket of calcareous rock, probably between volcanic blocks at the base of the outcrop. However, a new lookout, the Miradouro de Macela, was being constructed during Feb 1998 to overlook the beach at Praia, at the seaward extremity of the bend, across the road and behind the photographer in Krejci-Graf et al.’s (1958: fig. 4) photograph. The soft, fawn, non-calcareous, tuffaceous sandstone in the foundations of the lookout was found to contain numerous moulds of Janthina krejcii sp. nov. Ten of these are here designated as paratypes ( GNS WM 18973 ; the two most complete illustrated, Figs 26I–N ), and three others are incomplete. Colom (in Krejci-Graf et al., 1958: pls 5–6) illustrated planktonic foraminiferans in a sample from quarries near Figueiral on the south side of Pico do Facho, near the Miradouro de Macela , including Globoconella puncticulata ( Deshayes, 1832) , Hirsutella cf. margaritae (Bolli & Bermudez, 1965) and Globigerinoides sacculifer ( Brady, 1877) (reidentified by M. Crundwell, GNS, pers. comm. 17 Sep 2012), a diagnostic Zanclean fauna. The age of the type locality of Janthina krejcii has not been determined in detail but, as it is at a similar elevation to the quarries sampled by Krejci-Graf et al. (1958) and the Cré locality described by Janssen et al. (2008), is likely to be a similar age within Zanclean time. Only the type material has been observed.

Distribution. The writer has seen specimens of Janthina krejcii sp. nov. only from the type locality and the outcrop across the road from it, at the lookout (Miradouro de Macela) on the road descending from Almagreira to Praia, Santa Maria Island, Azores Islands. Bronn (in Reiss, 1862: 33) noted that one of his specimens of Janthina typica from near Praia was crushed but lacked spiral folds, so his material seems to have included a specimen of J. krejcii sp. nov. from the type locality. He discussed whether it might be a distinct species, but concluded this was individual variation. As with all other relevant early collections, the present location of Reiss’s material is not known to the writer. Mayer (1864: 93, 101) also recorded a single specimen of “ Janthina hartungi ” from Praia, but as it is not mentioned in the list of material following his description ( Mayer, 1864: 63), he presumably merely repeated Bronn’s record. However, Mayer (1864: 63) also recorded a specimen of “ Janthina hartungi ” without spiral folds from Pinheiros, a locality a short distance northeast of Cré, Santa Maria Island. As the writer has not seen material from Pinheiros, it is possible that J. krejcii sp. nov. occurs more widely on Santa Maria Island than the present record indicates.

Dimensions. See Table 4 . Most paratype moulds are too incomplete or too distorted to measure. The largest fragmentary paratype in WM18973 is 34 mm wide, but is compressed significantly; a maximum diameter of c. 32 mm is likely.

Diagnosis. Teleoconch moderately large, short and wide (D/H 1.2–1.35), spire very low to almost flat, whorls evenly convex; completely covered with fine, straight, acline axial ridges, but without obvious spiral sculpture. Outer lip straight, acline; sinus small, moderately deep, semicircular to weakly V-shaped, situated at base of lip.

Description. Teleoconch moderate-sized for genus, reaching c. 32 mm in diameter and 25 mm in height, wide (D/H 1.2–1.35), very low-spired, with c. 3.5 evenly and strongly convex teleoconch whorls; without obvious spiral sculpture. Spire little elevated above last whorl; suture appressed.Axial sculpture of many closely spaced, straight, thin, acline, low lamellae with flat-bottomed interspaces, extending from suture to umbilical hollow over entire teleoconch, c. 1 mm apart at periphery on last whorl. Aperture large, tall, almost vertical, with thin lips; columellar area and umbilical hollow poorly preserved in all material, apparently similar to those of Janthina typica and J. chavani . Outer lip sinus against base of columella, moderately large, semicircular to weakly V-shaped as in J. chavani , visible in only two paratype moulds in WM18973. Protoconch not seen.

Remarks. Janthina krejcii sp. nov. resembles J. typica and J. chavani in its uniform sculpture of fine, closely spaced, straight axial ridges over the entire teleoconch and in its semicircular to shallowly V-shaped outer-lip sinus situated at the base of the lip. However, it differs from them both in its consistently very low to almost flat spire, so that width is significantly greater than height in all specimens, and in its complete lack of obvious spiral sculpture. It also reaches a markedly smaller maximum diameter than J. chavani , although similar in width to J. typica . Were only K. Krejci-Graf’s original specimens available they might be thought aberrant specimens of J. typica , but all 10 reasonably complete moulds and several additional fragments from the Miradouro de Macela (GNS WM18973) are consistent with Krejci-Graf’s specimens in their low spire and in completely lacking spiral folds. With 15 consistent specimens available, it must be concluded that this is a previously unrecognized species of Janthina . Apparently J. krejcii sp. nov. occurs also at Pinheiros, a short distance NW of Cré, Santa Maria Island, but this locality requires re-collecting. It is not clear as yet whether J. krejcii sp. nov. represents a restricted Atlantic species or, as seems more likely, it happened to live during a late Zanclean time interval that is otherwise not represented by facies suitable for the preservation of Janthina fossils. It is intermediate between J. chavani and the living Janthina species in having consistent axial ridges but lacking spiral folds. Only the collection of J. krejcii at further localities will clarify its time and geographical ranges and its position in the phylogeny of Janthina species.

Etymology. The new species is named in honour of Dr Karl Krejci-Graf, formerly of Universität Frankfurt am Main, who collected the type material and advised the present writer about its locality.

Time range. Zanclean, c. 4.8–4.3 Ma; the older limit is poorly constrained, but the upper limit on Santa Maria Island cannot be younger than 4.32 Ma ( Sibrant et al., 2015).

Figures

Figure 26. Specimens of Janthina krejcii sp. nov., all from Miradouro de Macela, road descending from Almagreira to Praia, Santa Maria I., Azores, Zanclean. (A–B, D–E) holotype, SMF10135a; C, F, paratype, SMF10135c; G–H, paratype, SMF10135b; all from road cut opposite Miradouro de Macela, coll. K. Krejci-Graf. (I–N) 2 paratype moulds, GNS WM18973, sandstone in foundations of Miradouro de Macela. Scale bar 10 mm.