The new encrusting microproblematicum <i>Circumpodium enigmaticum</i> and its attachment trace <i>Circumpodichnus serialis</i> from the Middle Jurassic of Normandy (France)
<p>A single specimen of an enigmatic new attachment etching, together with an unknown calcareous encruster partly preserved in situ, has been identified on a belemnite rostrum from the Marnes de Dives Formation (Callovian, Middle Jurassic) of the Falaises des Vaches Noires in Normandy, France....
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Pensoft Publishers
2019-10-01
|
| Series: | Fossil Record |
| Online Access: | https://www.foss-rec.net/22/77/2019/fr-22-77-2019.pdf |
| Summary: | <p>A single specimen of an enigmatic new attachment etching,
together with an unknown calcareous encruster partly preserved in situ, has
been identified on a belemnite rostrum from the Marnes de Dives Formation
(Callovian, Middle Jurassic) of the Falaises des Vaches Noires in Normandy,
France. The trace fossil, here established as the new ichnotaxon
<i>Circumpodichnus serialis</i> igen. et isp. n., is a uniserial arrangement of very shallow depressions,
oval to fusiform in outline, with peripheral pouches and central pits.</p>
<p>The trace maker has a morphology unlike any other known calcareous epibiont,
fossil or recent, and is consequently described as the new
microproblematicum <i>Circumpodium enigmaticum</i> gen. et sp. n. Its calcitic skeleton is composed of a
chain of segments with perforate basal and lateral walls, anchored to the
attachment trace in the substratum by vertical protrusions in the centre and
feet-like protrusions in the periphery. The hypothetical upper wall of the
segments was either organic-walled and has decayed or it was calcitic and
has been abraded.</p>
<p>Based on morphological criteria and the capacity to bioerode, <i>C. enigmaticum</i> can best be
compared to encrusting bryozoans and foraminiferans. Candidate bryozoans are
aberrant arachnidiid ctenostomes, early cheilostomes, or stomatoporid
cyclostomes. Among the foraminiferans, webbinellid or ramulinid
polymorphinids are closest in their characters. In addition, tintinnid or
folliculinid ciliophorans are considered as an alternative interpretation,
and similarities to the Palaeozoic microproblematicum <i>Allonema</i> are discussed.</p> |
|---|---|
| ISSN: | 2193-0066 2193-0074 |