Euconodont hard tissue: preservation patterns of the basal body

Abstract

Conodont elements, consisting of crown and basal tissue are the well‐known fossilized hard parts of Conodonta (extinct marine chordates), but the taphonomic processes leading to decomposition or remineralization of the basal tissue are not well understood. Here we focus on the taphonomy of basal tissue, reviewing the published record and describing new material from Asia and Europe (248 occurrences globally). These include crown and basal tissue in conjunction, and isolated basal bodies showing different stages of preservation. Some isolated specimens resemble phosphate rings similar to those assigned to Phosphannulus universalis. High‐resolution biostratigraphy indicates that the lamellar type of conodont basal tissue is found in all facies and depositional environments. Other basal tissue types, described in the literature as tubular, mesodentine, spherulitic or lamellar with canalules, are limited to the early Palaeozoic and found exclusively in siliciclastic deposits (with the exception of spherulitic tissue). Although the stratigraphic record of basal tissue spans the range of Euconodonta (Cambrian–Triassic), this study shows that most of the isolated plate and ring‐like structures are derived from early Palaeozoic coniform conodonts. Basal tissue of platform‐type elements has a much more fragile shape and is therefore rarely preserved as a recognizable isolated unit.

Byronids and similar tubular fossils from the Devonian of the Barrandian area (Czech Republic)

“…Byroniids from the Devonian of Central Bohemia prove that Phosphannulus is, at least in part (for different interpretation see Suttner & Kido 2020), the attachment structure of byronids. Co-occurrence of attachment discs with more tubular thecate fossils indicates that byronids, sphenothallids and conulariids utilised various substrate for firm and stable attachment (see Van Iten et al .…”

“…Recently, Suttner & Kido (2020) concluded a possibility of rings belonging to Phosphannulus to be a taphonomic artefact of basal parts of conodonts. No doubt some of them are really of the conodont origin; however, new material from the Barrandian area of the Czech Republic brings additional evidence about the byronid origin and adhering function of most of those rings.…”