ABSTRACT
Thecideide phylogeny has been investigated by constructing a matrix of 54 characters (some multistate, all unordered, equal weight) and up to 46 ingroup taxa (at least one per genus). Terebratulide, strophomenate, and spire-bearing outgroups were used, together and separately, to polarize the characters and root the trees. Most terebratulide-rooted trees have the Jurassic genus Eudesella basal, and many distal clades were stratigraphically inverted, with the oldest members in derived positions. Trees constructed using other outgroups placed many Triassic taxa, for instance Thecospira, at or near the root and showed better agreement with the stratigraphic record. One common feature of all trees, supported by the presence of a broad median septum and ramuli, was the appearance of a derived Lacazella clade that includes many of the Thecideidae.
