In 1985, Derek Briggs and Whittington published a major redescription of Anomalocaris, also from the Burgess Shale.[26] Soon after that, Swedish palaeontologist Jan Bergström in 1986 noted on the similarity of Anomalocaris and Opabinia, suggested that the two animals were related, as they shared numerous features (e.g. lateral flaps, gill blades, stalked eyes and specialized frontal appendages). He classified them as primitive arthropods, although he considered that arthropods are not a single phylum.[2]