Soft-tissue anatomy of an Orsten-type phosphatocopid crustacean from the Cambrian Furongian of China revealed by synchrotron radiation X-ray tomographic microscopy

Abstract

Fossils of Orsten-type preservation represented by Skara and Phosphatocopida have been reported from the Cambrian Furongian of Western Hunan, China. Their taxonomy and external morphology are well known, but their internal soft-tissue anatomy has not been revealed yet. With the application of synchrotron radiation X-ray tomographic microscopy, here we describe the internal soft-tissue anatomy of an Orsten-type preserved phosphatocopid crustacean assigned to Hesslandona angustata. The internal organs and tissues of this specimen were collapsed after death to form a visceral mass situated within the labrum and underneath the sternal cuticle. The visceral mass contains the digestive system, including digestive tract and possible digestive glands. The digestive tract starts from the mouth, followed by oesophagus (foregut) and midgut, whereas the hind gut and anus are unknown due to incomplete preservation. Two bilaterally symmetric knob-like structures beside the midgut may be digestive glands (midgut diverticula). The visceral mass also contains other structures that may be related to nerve tissues and/or muscles, but identification as specific organs or tissues is uncertain.