Baring it all: undressing Cambrian ‘Orsten’ phosphatocopine crustaceans using synchrotron radiation X-ray tomographic microscopy

Abstract

, M. 2016: Baring it all: undressing Cambrian 'Orsten' phosphatocopine crustaceans using synchrotron radiation X-ray tomographic microscopy. Lethaia, Vol. 49, Synchrotron radiation X-ray tomographic microscopy (SRXTM) was used to virtually dissect and peel the shields off of the microscopic, bivalved phosphatocopine crustaceans in the Cambrian 'Orsten' type of preservation of Sweden. Doing so opened up for an array of concealed internal structures to be observed in a fully enclosed specimen of Hesslandona ventrospinata and a semi-enclosed specimen of Hesslandona angustata. For comparison, also a head-larva stage specimen of H. angustata, with shields in 'butterfly position', was analysed. The X-ray tomographic data sets revealed excellently preserved structures, such as labrum, sternum, antennae, mandibular and post-mandibular limbs with their minute setae, all of which were more or less disguised by the enclosing shields. This, moreover, allowed assignment to growth stages of the specimens, which is impossible based solely on external morphology and size. Micro-spherules observed inside the shields of the semi-enclosed H. angustata specimen may represent remains of food particles, and the feeding biology of phosphatocopines is discussed in detail. Our analyses suggest that phosphatocopines were particle feeders. The SRXTM technique offers the ability to three-dimensionally reconstruct the morphology in high resolution, construct virtual serial sections and study concealed structures. The resulting data allow for new structures to be revealed for previously known taxa and for new taxa to be identified, with the added benefit of not destroying the specimens in the process.

First record of Cyanobacteria in Cambrian Orsten deposits of Sweden

“…; Eriksson et al . , ). Also the material studied here shows signs of taphonomic processes variably affecting the specimens, as is evident by the different appearances of tube morphology, trichome articulation, cell morphology and surface texture.…”

“…17.3; Eriksson et al . , ). The sheaths of filamentous cyanobacteria consists largely of cross‐linked polysaccharides and may contain variable amounts of phenolic elements (Garcia‐Pichel & Castenholz ; Robbins ), whereas the cellular material of the trichome is composed of peptidoglycans, lipopolysaccharides and various proteins (Brock & Madigan ).…”

Palaeozoic ‘conodont pearls’ and other phosphatic micro-spherules

“…), whereas the remainder were attached to a low light‐refractive fishing line (0.3 mm in diameter) in accordance with the technique described by Eriksson et al . ().…”

“…The technical set‐up for this analysis largely follows that of Eriksson et al . (, ). Two specimens were stacked vertically in thin‐walled, low X‐ray scattering, capillary glass tubes (see Eriksson et al .…”

“…Our analyses were performed at the TOMCAT beamline of the Swiss Light Source, Paul Scherrer Institute, Switzerland (Stampanoni et al 2006). The technical set-up for this analysis largely follows that of Eriksson et al (2012Eriksson et al ( , 2015. Two specimens were stacked vertically in thin-walled, low X-ray scattering, capillary glass tubes (see Eriksson et al 2012), whereas the remainder were attached to a low lightrefractive fishing line (0.3 mm in diameter) in accordance with the technique described by Eriksson et al (2015).…”