Angelinoceras Hyatt, 1894

Aubrechtová, Martina & Korn, Dieter, 2022, Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician), European Journal of Taxonomy 799 (1), pp. 1-108 : 40-41

Genus Angelinoceras Hyatt, 1894

Type species

Lituites latus Angelin, 1880 ; subsequent designation by Sweet (1958).

Diagnosis

Genus of the family Lituitidae with loosely coiled apical part of the conch, 30 to over 50 mm in diameter, and moderately expanded (ca 8°) sigmoidal backcoiled part. Whorl profile compressed throughout (WWI ~ 0.90 at the last whorl). Whorl expansion rate based on whorl height decreases during ontogeny from 3.00 to 2.00. Ornament with regularly spaced narrow annuli/raised lirae and finer lirae in between; annuli with deep ventral sinus, prominent ventrolateral projections, broad and asymmetric lateral sinuses, low dorsolateral projections, and a broad, nearly straight dorsal sinus subdivided, at least in the early stages, by a mid-dorsal projection. Ventral band with ventrolateral ridges may be present (after Sweet 1958; Furnish & Glenister 1964).

Species included

Only the type species.

Remarks

Fang et al. (2021) proposed, among others, to synonymise Angelinoceras with Lituites . The species of the two genera are indeed similar, essentially differing only in the conch size (coiled conch diameters in Angelinoceras may exceed 50 mm). The herein studied material is, however, too incomplete in preservation to make a proper decision on this matter.

The genus Angelinoceras consists only of the type species A. latum . This species is known from the middle Darriwilian strata of mainland Sweden and the Island of Öland, and also from erratics in Germany that derived from Darriwilian rocks of Baltoscandia. With its narrow stratigraphic range, A. latum is a stratigraphically significant taxon in Baltoscandia (e.g., Jaanusson & Mutvei 1953; Evans et al. 2014).

Sweet (1958) described a probable second, stratigraphically younger species from the Ampyx Limestone of the Oslo-Asker district (Sandbian, early Late Ordovician). However, because of its fragmentary preservation, he assigned this specimen as Angelinoceras sp. Aceñolaza et al. (1977) reported Angelinoceras sp. from the San Juan Formation (Middle Ordovician) of the Argentine Precordillera, but that specimen differs in the geometry of the coiled conch part and has a lower expansion rate than characteristic representatives of Angelinoceras . In fact, based on the photograph provided by Aceñolaza et al. (1977: pl. 1g), it seems the specimen might actually belong to the family Estonioceratidae (order Tarphyceratida Flower, 1950 ), rather than the lituitids.

Geographic and stratigraphic occurrence

Norway and Sweden (in situ) and northern Germany and northern Poland (in erratics within Pleistocene gravels); Kunda to early Kukruse regional stages (Middle to early Late Ordovician).