Hadimopanella oezgueli Gedik, 1977: a palaeoscolecidan sclerite useless for taxonomic purposes

Abstract

A new assemblage of Hadimopanella oezgueli Gedik, 1977 is described from the middle Caesaraugustan (middle Cambrian) part of the Genestosa Member (Oville Formation) in the Cantabrian Mountains, northern Spain. Sclerites occur disarticulated and display distinct diagenetic processes, with authigenic chlorites occluding primary porosity and secondary fissures. Sclerite distribution was controlled by patchy development of epibenthic multispecies clumps on shell (both carbonate and clayey) substrates. A joint biometric and statistical analysis in both dorsal and lateral views of disarticulated sclerites allows characterization of two distinct morphotypes. These are compared with other occurrences of H. oezgueli sclerites from other margins of Gondwana and the Siberian Platform, as a result of which, another morphotype is identified. Two main inferences can be drawn: (i) different ventral trunk-sided sclerites of a same scleritome comprise different sclerite morphotypes and (ii) one distinct sclerite morphotype occurs in different genera and species. These results emphasize the idea that the diagnostic features that characterize the parataxon H. oezgueli should not be used for (bio) taxonomic classification of palaeoscolecidan scleritomes. Tania Barragán. Centro de Astrobiología (CSIC/INTA), Ctra. de Torrejón a Ajalvir km 4,

Cambrian palaeoscolecids (Cycloneuralia) of southern Scandinavia

“…Barragán et al . ). However, the broad morphological variability observed in many species of Hadimopanella is consistent between different localities with contemporaneous strata supporting their validity as biological species.…”

“…Also, Barragán et al . () doubted the taxonomic value of disarticulated sclerites. After a detailed statistical analysis of the morphology and proportions of Hadimopanella oezgueli and that of purported similar forms, they concluded that Hadimopanella represents a parataxon and morphological characters of isolated sclerites should not be considered for diagnosing scleritome taxa.…”

“…The lack of this distinction is one of the reasons why we consider the outcome of the statistical analysis of Barragán et al . () to be problematic. They analysed and compared the morphological range of H. oezgueli with individual H. oezgueli ‐type sclerites from macroscopic specimens.…”

“…Furthermore, Barragán et al . () included a taxon that had been described as H. oezgueli by Wrona & Hamdi (), which might represent a different species (see above and Geyer et al . ), further compromising their analysis.…”

The Cambrian palaeoscolecidWronascolexfrom the Shipai fauna (Cambrian Series 2, Stage 4) of the Three Gorges area, South China

“…Finally, the taxonomic classification for isolated Hadimopanella ‐type sclerites is likely to be inaccurate (Barragán et al . ), and the current taxa of Wronascolex may not reflect the actual biodiversity. It is clear therefore, that for a more accurate taxonomic treatment of palaeoscolecidans, detailed knowledge of specific scleritomes and the associated microstructures will be very important in order to proceed further.…”