Emarginula coralliora Lundgren, 1867

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 59-60

Emarginula coralliora Lundgren, 1867

Figs 19 I–K

1867 Emarginula coralliorum Lundgren : 19–20, pl. 1, figs 5a–b.

1902 Emarginula coralliorum Lundgren—Ravn : 213, pl. 1, fig. 1.

1903 Emarginula coralliorum Lundgren—Ravn : 394–395, 416–17.

1940 Emarginula sp. I—Rosenkrantz: 512.

1940 Emarginula sp. II—Rosenkrantz: 512.

2004 Emarginula (s.s.) coralliora Lundgren, 1867 —Pacaud: 599, fig. 10.

2014 Emarginula (Emarginula) coralliora Lundgren, 1867 —Hansen & Surlyk: 339, fig. 5: 16–17, tab. 3.

2014 Emarginula coralliora Lundgren 1867 —Lauridsen & Schnetler: 36, fig. 2.

Diagnosis. Species of Emarginula characterised by a strongly recurved apex typically situated close to posterior margin, a raised selenizone forming distinct keel with bordering flanges, coarsely cancellate sculpture and by approximately 28 primary radial riblets intercalated with the same number of secondary riblets. Interstices simple pit-like, at least sometimes divided into a pair by a microlirule.

Material. The Højerup Member at Stevns Klint is represented by MGUH 33083, ØSM.10042-189, ØSM. 10042- 334-b–c, together with 16 specimens with informal numbers (SH.9, SS.62.A–B, SR.730, SR.733.A–B, SR.738, SR.744, SR.806, SR.908.A–B, SR.922, SR.940, SR.992.B, SR.1002, SR.1061.A–B, SR.1062, SR.1075.C and SR.1118) and eight specimens lacking numbers in the collections of the Natural History Museum of Denmark. The Cerithium Limestone Member is represented by specimen MGUH 33084 .

Type stratum and type locality. The holotype LO 180T ( Lundgren 1867: fig. 5a) stored at the Department of Geology, Lund University, Sweden, was collected from the Danian limestone at Limhamn, Sweden.

Occurrence. In Denmark E. coralliora ranges from the Højerup Mb. of the upper Maastrichtian Tor Formation at Stevns Klint and up into the lower Danian Stevns Klint Fm. and middle Danian Faxe Formation at Faxe ( Ravn 1902). Based on the museum collections and newly collected material, it appears to be extremely rare in the Rødvig Formation (only one specimen). Outside Denmark it is known from the Danian of Belgium, France, Germany, Sweden and Ukraine and from the Thanetian of the Carpathians ( Pacaud 2004).

Description. Shell patelliform with elongate-oval base. Relative height strongly variable, but typically corresponding to between 40 and 55 % of length. Apex posterior, strongly recurved, situated close to or above posterior margin. Anterior slope broadly convex. Posterior slope concave to nearly straight below apex. Sides of shell nearly straight. Protoconch minute, more or less overhung by succeeding shell. Selenizone raised, forming distinct keel with bordering flanges. Slit short and narrow, length in dorsal view approximating 15 % of anterior slope. Sculpture coarsely cancellate with approximately 28 primary radial riblets intercalated with equal number of weak secondary riblets. Raised concentric ridges reaching around half the thickness of primary radial riblets, but usually markedly stronger than secondary radials. Interstices simple pit-like rectangular, at least sometimes divided into a pair by a microlirule. Margin weakly crenulated by rib extensions.

Measurements. The largest specimen from the Danish Cretaceous-Palaeogene boundary is approximately 13 mm long, 7.4 mm wide and 5.7 mm high. It was collected by S. B. Andersen (05.06.1970) from the top of the Højerup Member of the upper Maastrichtian Tor Formation at Holtug, Stevns Klint.

Remarks. As already noted by Ravn (1902) the specimens from the Cretaceous-Palaeogene boundary differ from the typical E. coralliora from slightly younger strata by a generally relatively lower shell, though the variation inside the two stratigraphic populations is considerable. Except for this one feature there appear to be no differences. The size also appears unchanged.

Figures

FIGURE 19. A–C. Acmaea selandica n. sp. A. Inner mould of holotype MGUH 33077. Length 5.9 mm. B. Paratype MGUH 33078. Length 2.6 mm. C. Internal mould of paratype MGUH 33079. Length 4.45 mm. D–E. Acmaea? sp. Wax cast of now lost specimen MGUH 33080. Length 19.7 mm. F–G. Cocculina? sp. Silicone cast of MGUH 33081. Exposed length 5.7 mm. H. Symmetrocapulus? sp., external mould MGUH 33082. Length 2.4 mm. I–K. Emarginula coralliora Lundgren, 1867. I–J. Silicone cast of MGUH 33083. Length 2.9 mm, height 1 mm. K. Inner mould of MGUH 33084. Length 7.8 mm. L–Q. Cranopsis cretacea n. sp. L–O. Silicone cast and inner mould of holotype MGUH 33085. Length 3.6 mm, width 2.6 mm. P–Q. Silicone cast and inner mould of paratype MGUH 33086. Length 2.1 mm. R–S. Palaeoloxotoma sp., Silicone cast of MGUH 33087. Length 17.2 mm.