Diagnoza

In icrion of P₁ elements denticles of the middle row weaker than those of lateral rows and alternating with them; cusp transverse to the base

Porównanie

In the earliest Famennian sample Pł-36  P₁ elements of Icriodus are highly variable. Most of them show a fusiform icrion with small tubercles of the middle row. In narrow specimens they tend to disappear. The basal cavity is generally large and wide, although in rare specimens it may be narrower, similar to geologically younger populations of the lineage. Juveniles show small and straight cusp, initially associated with a single ventral denticle that usually merges the central row but frequently it is laterally displaced. With growth, the cusp became prominent and somewhat inclined, which results in development of a ridge along its occlusal surface; the resulting appearance restores to some degree the separation of the cusp from the icrion typical of juveniles. In profile view, the icrion is virtually straight, only slightly convex in some specimens. Contribution of such specimens to the somewhat younger sample J-53a  seems slightly higher. Associated non-platform elements range in shape from triangular to needle-like, with no apparent morphological classes (possible exceptions are the widest and most robust specimens, probably representing P₂ elements). All show sharp edges and relatively flat appearance but in sample Wtr-27 several robust specimens with subquadrate or subtriangular section of the base occur. They differ from elements of much younger Mitrellataxis circularis in their widely expanding basal cone.

Autekologia

Występowanie geograficzne

From the base of the Famennian to the early K. crepida Zone in all studied localities. The species occurs also in the Dębnik area (Baliński 1995).

Zasięg czasowy

Materiały muzealne

10,161 specimens.

Literatura