Cambridge University Press apologizes for an error that appears in the published version of this article (Bicknell et al., Reference Bicknell, Smith, Howells and Foster2022).
Due to an error during corrections, the published version of Figure 2.1 is an older version that is, due to a graphics creation error, partially obscured by a black overlay. The correct newest version of the figure appears on the following page.
Figure 2. Malformed Ogygiocarella debuchii (Brongniart, 1822) and Zacanthoides sp. indet. (of Walcott, 1888): (1, 2) Ogygiocarella debuchii from the Llanfawr Mudstones (Middle Ordovician, Darriwilian), AM F128230: (1) complete specimen; (2) detail of abnormality in box in (1) showing W-shaped indentation on the left side of the pygidium; (3, 4) Zacanthoides sp. indet. from the Half Moon Mine, Chisholm Formation (Miaolingian, Wuliuan), FHPR 17618: (3) complete specimen; (4) detail of abnormality in box in (3) showing abnormally developed pleural spine (white arrow). All specimens coated. All images converted to grayscale.