Fig. 14. A. Hypothesized morphogenetic pathway for derivation of the bivalved stenothecoid scleritome from a multisclerite, tubular, organocalcitic, eccentrothecimorph ancestor via a hypothetical organocalcitic tannuolinid. Eccentrothecimorph slightly modified from Skovsted et al. (2011: text-fig. 17). Tannuolinid modified from Skovsted et al. (2014). B. A possible cladogram that assumes an organocalcitic scleritome is primitive for the Pan-Brachiopoda. In this view, organophosphatic mineralogy evolved independently several times and the Stenothecoida evolved a bivalved scleritome independently of the Brachiopoda + Micrina clade.

Published as part of Johnston, Paul A. & Streng, Michael, 2021, Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation, pp. 723-751 in Acta Palaeontologica Polonica 66 (4) on page 747, DOI: 10.4202/app.00928.2021, http://zenodo.org/record/12196229