Sequence alignments and phylogenetic analysis

Cytochrome oxidase I, 16S, and concatenated sequences were aligned using MUSCLE (Edgar 2004) in Geneious version 9.0.5 (Kearse et al. 2012). Optimal nucleotide substitution models were determined for each gene under the corrected Akaike information criterion (AIC_c) in jModeltest 2.1.4 (Darriba et al. 2012). The HKY + I model was applied to 16S; HKY + G to COI; and GTR + I + G to concatenated 16S‐COI. Phylogenetic analyses using Bayesian inference in Mr. Bayes 3.1.2 (Ronquist and Huelsenbeck 2003); two independent parallel runs of four incrementally heated Metropolis‐coupled Monte Carlo Markov chains, sampling every 1000 generations with a burn‐in of 25%. Trees were visualized in FigTree v1.3.1 (Rambaut 2009). Outgroups and other Nautilus sequences were obtained from GenBank. Numbers of variable and informative sites were generated using PAUP* version 4.0b10 (Swofford 2002).