Onychites from Polish Jura and Their Functional Morphology

Przemysław Sztajner

doi:10.3390/min11111207

Abstract

Onychites aff. barbatus is excessively rare in the Polish Jura. This paper describes a recent find from the basal middle Oxfordian. The specimen is preserved in a manner typical for other finds of this kind in platy limestones, i.e., as compressed and flattened imprints with remnants of carbonized organic matter. Excellent preservation of the surfaces enables a precise reconstruction of the original structure. Accordingly, I hypothesize on the attachment to soft parts and the function of the belemnite onychites. The high diversity of known onychites, especially from Europe (NW Tethys), indicates that they served a variety of purposes.

Highlights

Onychites were first reported by Fraas [1], who described a single species that he named Onychoteuthis barbata
It is supposed that onychites were a sexual feature, found probably in mature males who may have used it for competition among one another or for mating, analogous to various arm modifications in the present-day cephalopods
Onychites are almost exclusively found separated from rostra that serve as the basis for belemnite systematics

Summary

Introduction

Onychites were first reported by Fraas [1], who described a single species that he named Onychoteuthis barbata. Out of 27 specimens of belemnites with preserved arms including arm-hooks known from Europe (mostly Germany), only two bear onychites [5]. It is supposed that onychites were a sexual feature, found probably in mature males who may have used it for competition among one another or for mating, analogous to various arm modifications in the present-day cephalopods. The find of a relatively well-preserved onychite in a fine-grained platy limestone, albeit separated from the remainder of the body, may shed new light on the mechanics of their work and, probable function in the living organism, and as a sexual feature on mating habits

Geological Setting

Methods

Remarks on Functional Morphology

Geographic Variation of Published Onychite Morphologies and Functions

Conclusions