Lituites fallax Remele 1890
Creators: name: Aubrechtová, Martina
name: Korn, Dieter
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Cephalopoda
Orthocerida
Lituitidae
Lituites
Lituites fallax

description: Lituites fallax Remelé, 1890
Fig. 46, Table 9
Lituites fallax Remelé, 1890: 59, pl. 5 fig. 1.
Diagnosis
Species of the genus Lituites with coiled conch diameter of ca 40 mm; whorl expansion rate 1.70. Shell surface of the coiled part of lirae (0.5–1.0 mm apart), raised in ca 2 mm wide intervals. Deep, rounded ventral sinus, very low dorsal projection; lirae straight laterally, direction rectiradiate.
Type material
Lectotype (designated herein) GERMANY • Brandenburg, Heegermühle; Ordovician (late Lasnamägi Regional Stage, late Darriwilian), Upper Grey Orthoceratite Limestone; Ramann Coll.; previously illustrated by Remelé (1890: pl. 5 fig. 1), re-illustrated here in Fig. 46; MB.C.11672.2.
Description
Lectotype MB.C.11672.2 (Fig. 46) is a fragment of a third of the last whorl of the coiled part (40 mm estimated diameter; WER ah ~ 1.70) of a conch. The ornament consists of sharp lirae (0.5–1.0 mm apart), raised in more or less regular intervals (every ca 2 mm); the lirae are straight on the flanks, with a narrow ventrolateral projection. The ventral sinus is deep and rounded, dorsal projection is very low with a shallow dorsolateral sinus.
Remarks
The lectotype of Lituites fallax is incompletely preserved and therefore, it cannot be excluded that it represents a morphological variant of some other species of the genus Lituites. Most similar to L. fallax are L. kruegeri sp. nov. and L. cf. kruegeri, both of which differ from L. fallax in having a smaller conch diameter (33 and 28 mm, respectively) and a higher WER ah (2 and 2.30, respectively). Also, L. fallax is ornamented with lirae, which are straight on the flanks, while prorsiradiate lirae and flat annuli are developed in L. kruegeri sp. nov. (Fig. 8) and also in L. cf. kruegeri. Some specimens of L. perfectus have a large conch diameter (39 mm in the neotype MB.C.30544) and a low WER ah (1.9 in MB.C.30544 and MB.C.30545) as L. fallax but the former species differs in the shell ornament of the coiled part; it consists of growth lines and rectiradiate annuli or ribs instead of sharp lirae. With only the holotype MB.C.11672.2 at hand, it is therefore not possible to confidently synonymise L. fallax with any other species of the genus Lituites.
Remelé (1890: pl. 1 fig. 3) assigned a second specimen (MB.C.11673.2) from coeval strata to Lituites fallax? but in this specimen nothing of the coiled part is preserved and hence its correspondence to the holotype cannot be validated. Holm (1891) and Sweet (1958) argued that the specimen probably represents Trilacinoceras discors. Indeed, this specimen is similar in ornament, expansion angle and general adult size to T. discors. However, the specimen is still chambered and its whorl profile is circular. Its identity is thus left unresolved herein; the holotype remains the only specimen unequivocally attributable to L. fallax.
description: Published as part of Aubrechtová, Martina & Korn, Dieter, 2022, Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician), pp. 1-108 in European Journal of Taxonomy 799 (1) on pages 68-69, DOI: 10.5852/ejt.2022.799.1681, http://zenodo.org/record/6341270