Charactoceras sp. A, Strand, 1934

Charactoceras sp. A

Fig. 22C, E View Fig

Material examined

ESTONIA • 1 spec.; Vormsi Island, Hosholm shore ; Adila Formation , Pirgu Regional Stage; GIT 878- 215 View Materials .

Description

The specimen is a fragment of a nearly complete body chamber and one chamber of the phragmocone with a wide, reniform whorl cross section; it is 36 mm high at the aperture and 57 mm wide. At the base of the body chamber, it measures 24 mm in height and 41 mm in width. The body chamber measures ca 90–100° in length. Throughout its entire length, the greatest width of the whorl is reached between mid-flank and dorsum. On the broadly rounded ventral side, a distinct, broad, U-shaped hyponomic sinus is preserved, which has a width of 35 mm and a depth of 20 mm. Around the aperture patches of the outer shell remain, these are smooth, with distinct narrowly and irregularly spaced growth lines.

The two septa at the base of the body chamber are 6 mm distant, and a septal foramen located a few millimeters from the venter is apparent, but is not well enough preserved to measure.

Remarks

This single fragment does not permit species level determination. The position of the siphuncle and the shape of the body chamber, and its aperture show, however, that this specimen is a fragment of a Charactoceras . Its relatively large WWI of 1.71 (see Fig. 22E View Fig ) distinguishes the specimen from C. estonicum and suggests a comparison with C. hercules ( Billings, 1857) from late Katian strata of Anticosti Island, Quebec (e.g., Foerste 1928c). However, with the available material a detailed comparison is impossible as the more apical parts of the phragmocone are not known.