Kiaeroceras urgense, Kröger, 2025

Kröger, Björn, 2025, The Lyckholm acme of cephalopods - Review of the late Katian (Vormsi-Pirgu regional stages) Ordovician cephalopods of Estonia, European Journal of Taxonomy 978, pp. 1-169 : 110

Kiaeroceras urgense sp. nov.

urn:lsid:zoobank.org:act:4B0FA1B5-E540-4E9C-B93B-AEC7648EF1A2

Figs 31B , 35I

Diagnosis

Kiaeroceras with CHI of ca 1.1, a relatively long mature body chamber (RBL ca 1.7) and a mature conch height of ca 50 mm.

Etymology

Referring to the type locality.

Type material

Holotype

ESTONIA • Urge quarry; Kõrgessaare Formation, Vormsi Regional Stage; TUG 103-75 .

Paratypes

ESTONIA • 2 specs; Hiimuaa Island , Paluküla quarry; Moe Formation, Pirgu Regional Stage; TAM G136 :33, TAM G432 :727 • 1 spec.; same data as for preceding; TUG 47-864 .

Description

The holotype (Fig. 35I) is a relatively well-preserved part of a nearly complete mature body chamber and phragmocone. The conch surface is nearly smooth, ornamented with partly distinct, irregularly spaced growth lines or rugae ( Fig. 31B ). At the base of the body chamber, the conch height and width are 48 mm and 45 mm, respectively (CHI = 1.07). Hence, the conch cross section is slightly compressed. At the aperture, the conch cross section is not fully preserved, and a measurement of the conch width is not possible. The apertural height is 52 mm. With its total length of ca 80 mm, the body chamber is nearly tubular and straight. In cross section, the prosiphuncular side is more narrowly rounded, drop-shaped. In lateral view, the margins are almost straight.

The phragmocone is slightly endogastrically curved with a conch height increasing from 36 mm to 47 mm over a length of 60 mm (angle of expansion = 11°). A conspicuous constriction occurs at ca 30 mm adapically of the base of the body chamber with a conch height of ca 38 mm. At the adapical end of the specimen, the conch height is 33 mm, the corresponding width is 32 mm. The sutures are nearly transverse at the adapical end of the specimen and with shallow lateral lobes near the base of the mature body chamber. The septal foramen is close to the conch margin on the concave side of the conch. It has a diameter of ca 3 mm (RSH = 0.09). Traces of expanded siphuncular segments are preserved.

A second specimen (TUG 47-864) is a poorly preserved, slightly curved, fragment of a phragmocone and body chamber with a length of ca 130 mm of which only half of the conch is preserved. The siphuncle is missing, and the septa are fragmentary. The conch, however, shows the irregular constrictions of the phragmocone present in the holotype. The base of the body chamber has a height of 44 mm. The conch height expands with angles of expansion between 13° (heights 37 mm to 42 mm) and 22° (heights 30 mm to 37 mm).

Comparison

This species has a smaller adult size than K. frognoyense (mature body chamber height 68 mm), it has a less compressed conch cross section than K. heryoense Strand, 1934 (CHI = 1.15), and a longer body chamber than K. (?) ormsoense sp. nov. (mature body chamber height = 54 mm, RBL = 1).

Figures

Fig. 31. Details of shell ornamentation of cephalopods of the Vormsi–Pirgu regional stages, Estonia. A. Piersaloceras (?) sp., specimen TUG 1827-163, from Sutlema old quarry, Vormsi Regional Stage. B. Kiaeroceras urgense sp. nov. holotype TUG 103-75, from Urge quarry, Vormsi Regional Stage. C–D. Strandoceras sphynx (Schmidt, 1858). C. Specimen TAM G432:68, from Niibi hillock, Pirgu Regional Stage. D. Specimen TUG 1672-29, from Saxby village, Pirgu Regional Stage. E. Strandoceras sulevipoegi sp. nov., paratype TUG 899-55, from Saxby shore, Vormsi Regional Stage. Scale bar = 5 mm in all figures, same scale in A–B, and in C–E.