Monomorphichnus Crimes, 1970

Diagnosis.—Series of straight to sigmoidal, parallel or intersecting, laterally repeating striations in isolated or grouped sets; typically preserved in convex hyporelief (Crimes, 1970b; Fillion & Pickerill, 1990; Keighley & Pickerill, 1998).

Description: Clusters of five to six, elongate, straight to sigmoidal, striations that are approximately 5 to 6 mm long and are separated by 1.5 mm (Fig. 3G). The striations overlap in some cases but do not occur in paired parallel rows or lobes.
Remarks: Monomorphichnus consists of clusters of striations. Dimorphichnus is a similar ichnogenus that consists of a row of elongate striations and a parallel row of shorter striations. The distinction between these two ichnogenera is contended with Seilacher (1985) observing that the type material of the type ichnospecies of Monomorphichnus, M. bilinearis, preserves a faint row of shorter striations and therefore belongs within Dimorphichnus. However, Fillion and Pickerill (1990) state that such features are not present in the type material of M. bilinearis. Mángano et al. (2005) further suggested that Monomorphichnus should be retained, at least pending a full revision, even if M. bilinearis turns out to belong to Dimorphichnus because the other established ichnospecies of Monomorphichnus would not be able to be referred to Dimorphichnus without substantial emendation of the diagnosis.