Ippolitov, A.P., Vinn, O., Kupriyanova, E.K. and Jäger, M. 2014. Written in stone: history of serpulid polychaetes through time. Memoirs of Museum Victoria 71: 123-159.Although the fossil record of annelids in general is poor, calcareous tube-building Serpulidae are a notable exception. The "stumbling block" of understanding the serpulid fossil record is obtaining reliable taxonomic interpretations of fossil tubes based on morphology. Luckily, serpulid tubes demonstrate high variety of ultrastructures and nonuniform mineralogical composition, which can be used as new tools for decrypting the fossil record. Ancient Late Ediacaran (580-541 Ma) and Paleozoic (541-252 Ma) rocks contain diverse tubicolous fossils that have often been erroneously interpreted as annelids, and serpulids, in particular. Palaeozoic to Middle Jurassic coiled spirorbiform tubes, often referred to as Spirorbis, had been shown to be microconchids, a group of probable lophophorate affinity. The most ancient records of unequivocal serpulids date back to the Middle Triassic (~244 Ma) of the Mesozoic, and from the Earliest Jurassic (~200 Ma) fossil serpulids become common. From the latest Jurassic (~146 Ma) serpulids colonised hydrocarbon seep environments and possibly also penetrated the deep sea. Concerted efforts of paleontologists and zoologists are needed for further understanding of serpulid evolutionary history. The serpulid fossil record can become a valuable instrument for calibration of "molecular clocks" in polychaetes, which would allow dating not only divergence events in serpulids, but also in annelid groups that lack a representative fossil record.

Tube structure, ultrastructure and mineralogy support serpulid affinities of the problematic worm fossil ‘Serpula’etalensis from the Lower Jurassic of Germany. The original tube mineralogy of ‘Serpula’etalensis is purely aragonitic and is preserved in Upper Pliensbachian specimens from eastern Germany. ‘Serpula’etalensis represent the earliest record of aragonitic mineralogy for serpulids. The tube is formed of irregularly oriented prismatic crystals that are 3–6 µm in length and 0.5–1.0 µm in diameter. Calcitic specimens of ‘Serpula’etalensis from Upper Sinemurian of southwestern Germany were recrystallized during the diagenesis and lack the original tube ultrastructure.

Like other secondary soft‐bottom dwellers, serpulid and sabellid tube worms used particular strategies in order to cope with their earlier loss of mobility. This is expressed by the transition from irregular to genomically programmed morphologies of their calcareous shells that guarantee a stable horizontal resting position. In contrast to permanent recliners, however, this attitude was probably only the starting position for active resurrection after the muddy tail of storm sediments had settled on top of the displaced animal.

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