The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden Author Kröger, Björn text European Journal of Taxonomy 2013 2013-03-27 41 1 110 journal article http://dx.doi.org/10.5852/ejt.2013.41 386010a0-6da4-4fa3-9d1a-4b3b5427cac5 2118-9773 3814221 A2F1B9ED-870A-466E-B35E-BD5DA782476E Tyrioceras cf. kjaerulfi Strand, 1934 Figs 8A , 10B , 29A, C , 30 Tyrioceras kjaerulfi Strand, 1934: 50 , pl. 6. Tyrioceras kjerulfi – Dzik 1984: 133 , 138, text-fig. 55.5. Diagnosis Tyrioceras with angle of expansion of 11°; compressed conch cross section; ornamented with marked sinuous transverse growth lines that form ventral, lateral, and dorsal sinuses, and relatively deep ventrolateral and dorsolateral salients. (Adopted from Strand 1934 .) Type locality and horizon Furuholmen, Asker District, Norway , Grimsøy Formation (questionable), late Katian, Late Ordovician. Material One specimen from Kallholn, PMU 26897 , Siljan district, Dalarna , Sweden ; Boda Limestone, Boda Core Member, late Katian, Ordovician. Description Specimen PMU 26897 is a portion of a phragmocone 56 mm long with conch height and width increasing from 27 to 41 mm and 25 to 34 mm , respectively. The angles of expansion are 14° and ca. 9°, respectively, whereas the width/height ratio decreases from 0.93 apically to 0.83 adorally ( Figs 8A , 10B ). The relative chamber height is 0.4, and the septal convexity is 0.25 of the corresponding conch height. The siphuncle is subcentrally positioned with a diameter of ca. 0.13 of the conch cross section. The connecting ring is not preserved, but the septal necks are orthochoanitic and relatively long with ca. 0.45 of the chamber height ( Fig. 29A, C ). Heavy epi-, hyposeptal and mural deposits are developed. Adapically, the deposits cover the apical septal necks, forming epichoanitic deposits ( Fig. 30 ). The conch surface is ornamented with transverse lirae, ca. 4–5 in a distance of 1 mm . The spacing of the lirae varies periodically, forming bands with widths of ca. 4 mm . The lirae form a shallow sinus on the prosiphuncular, and a more pronounced sinus on the antisiphuncular side of the conch. Remarks This species is based on a single, probably mature body chamber fragment only. Nothing is known about the ontogenetic and intraspecific variability of characters such as angle of expansion, conch cross section or ornamentation. The specimen PMU 26897 , described above, is similar to Tyrioceras kjaerulfi with respect to the compressed conch cross section and the irregularly spaced transverse ornamentation. However, the type of the species differs in having a comparatively low angle of expansion (11°) and a lower width/height ratio (0.79). The specimens are provisionally interpreted as conspecific. Stratigraphic and geographic range Grimsøy Formation (questionable), Asker District, Norway ; Boda Limestone, Dalarna , Sweden , all late Katian, Late Ordovician.