English: Figure 3. Morphological reconstruction and phylogenetic position of Isoxys curvirostratus. a, Lateral view. b, Detail of the frontal appendage. c, Morphology of anterior batch of biramous appendages (a1–a4). d, Morphology of posterior batch of biramous appendages (a5–a14). e. Simplified strict consensus of maximum parsimony under implied weights (1 MPT, 699 steps, CI: 0.496, RI: 0.866). f. Simplified strict consensus of maximum parsimony under equal weights (12 MPTs, 705 steps, CI: 0.492, RI: 0.864). g. Majority rule consensus tree retrieved with Bayesian inference. h. Treespace analysis comparing the distribution of topologies favoring isoxyids versus Kylinxia as the outgroup to other deuteropods. See Extended Data Figs. 5 and 6 for detailed results and support values. Abbreviations: an, the nth ventral appendage; as, anterior spine; en, endopod; ey, eye; fa, frontal appendage; fn, podomeres of the frontal appendage from the distal to proximal; la, lamellae of exopod; pf, proximal part of the frontal appendage; ps, posterior cardinal spine of carapace; pps, paired posterior spines on endopod; sp, spines. Numbers indicate endopod podomeres.