Beloptera longa Naef, 1922

Beloptera longa Naef, 1922

Fig. 4a–c View Fig

Synonymy

1877 Beloptera belemnitoidea de Blainville, 1825 – Edwards & Wood, p. 36, pl. 2, fig. 1, Bartonian of England.

1922 Beloptera longa sp. nov. – Naef, p. 57, text-figs 18a–g, 19, Bartonian of England.

Holotype: Not defined.

Diagnosis: Beloptera with an elongate guard-like sheath that is slightly curved ventrally and with semicircular in outline lateral expansions. The dorsal surface is roof-like, almost smooth with radial grooves on the rostrum; the ventral surface is concave and almost smooth (radial grooves are on the rostrum); the rostrum is nearly triangular in cross-section.

Material: One moderately preserved specimen ( IGS-DYM 01/05) from the Priabonian Mandrykivka Beds of the Rybalsky Quarry, Dnipro.

Description: The specimen IGS-DYM01/05 is a moderately preserved elongated (L 2 /W 2 = 2.44, see Table 1), slightly curved ventrally 26.4-mm-long guard-like sheath with supposedly semicircular in outline lateral expansions inclined towards the venter and gives a convex form to the dorsal surface and a corresponding concavity to the venter. The lateral expansions are thick at the articulation area of the rostrum and sheath and become gradually thinner to the periphery. The dorsal surface is roof-like with a raised narrow medial zone and steep slopes gradually turning into lateral expansions. The rostrum is nearly triangular in cross-section and gradually widens; its apex is rounded in the ventral aspect and slightly pointed in the lateral aspect; the rostrum is slightly curved ventrally and the guard-like sheath is somewhat arched longitudinally. The ventral surface is almost smooth with very fine radial grooves on the rostrum. The dorsal surface is almost smooth with very fine radial grooves are on the rostrum.

dimorphism of B. belemnoidea specimens. However, B. belemnoidea significantly differs from B. curta in the longer and less massive rostrum, as well as an elliptical outline guard-like sheath.

It is rather difficult to compare B. longa with B. konincki Briart and Cornet, 1880 , as I know this species is described from not well preserved material only in Briart & Cornet (1880); images of this species in this work are not of very high quality. Probably, in contrast to B. longa , B. konincki has a rather short guard-like sheath with a more pointed, relatively short rostrum and radial and concentric ornamentation of the ventral surface.

Occurrence: Bartonian of England, Priabonian of Ukraine.

Specimen L 1 L 2 W 1 W 2 L 2 /W 2 IGS-

13.6 26.4 6.7 10.8 2.44 DYM01/05

Remarks: The described specimen does not differ significantly from Beloptera longa figured by Edwards & Wood (1877: pl. 2, fig. 1) and Naef (1922: text-figs 18a– g, 19). B. longa differs from the most morphologically similar species B. belemnoidea de Blainville, 1825 in the following morphological features: (1) the very convex smooth dorsal surface; (2) the greatly curved ventrally guard-like sheath; (3) the nearly triangular in cross-section rostrum; (4) the slightly pointed in the lateral aspect rostrum.

B. longa differs from B. curta ( Cossmann, 1896) in a much longer rostrum (relative to the total length of the guard-like sheath) and a more elongated guard-like sheath. In addition, the sheath of B. curta is rather strongly compressed in the dorsal-ventral direction. Vincent (1901) considered B. curta to be the ”anomaly” of B. belemnoidea , probably referring to the manifestation of intraspecific, probably sexual,