Recently, several molecular phylogenies for the myosin superfamily were published. While helpful regarding the evolution of the entire superfamily, they can obscure interesting information from individual organisms. 18 myosins (including 3 partials: F58G4.1, F45G2.2, Y11D7A.14 which Hodge and Cope included in their phylogeny (2000)) from WormBase were used to prepare a molecular phylogeny for C. elegans. BLAST reveals that F58G4.1 and F45G2.2 are striated-like myosin IIs while phylogenetic analysis indicates they evolved before the four muscle myosins. Are they myoepithelial? Y11D7A.14 may be an unconventional myosin. Analysis of gene/protein structure revealed that the position of the first intron is conserved in myosins B, C, and D. In myosins B, C, and D, exon II starts with DQSRAYDSKK (myosin C) with myosins B and D differing by only 1 substitution. The sequence is missing in all of the remaining myosins, and even though phylogenetics link
nmy-1 and
nmy-2 to a common ancestor, their first intron is not conserved. In addition, this analysis revealed the presence of a 15 amino acid sequence found in the N-terminus SH3-like domain (exon I or II) of the striated muscle myosin IIs only. The sequence DNKTHAWVPDAAEGF (F45G2.2) is highly conserved in the remaining five striated myosin IIs in C. elegans but is absent in
nmy-1 or
nmy-2. In addition, a BLAST search using this sequence returned striated myosin II sequences from invertebrates and the amphibian, Xenopus leavis, with the same sequence nearly identically conserved within the first 70 amino acids of the N-terminus. No sequences were returned from Mammalia and visual examination of multiple non-, smooth, and striated sequences confirmed this result. Furthermore, the first 70 amino acids of striated myosin IIs are very highly conserved in 1) flying insects and 2) scallops while nematodes show more divergence. The molecular phylogenetic tree generated revealed the following pairs of myosins shared a common ancestor during the course of their evolution: myosins B and D,
nmy-1 and
nmy-2,
hum-3 and
hum-8,
hum-2a&b,
hum-1 and
hum-5. Of the myosins studied,
hum-4,
hum-6,
hum-7, F45G2.2, F58G4.1, myosin A and Y11D7A.14 are single branches on the phylogenetic tree. F45G2.2 and F58G4.1 are intriguing since neither smooth muscle nor myoepithelial myosin II isoforms are definitively established in C. elegans. This study demonstrates that organismal molecular phylogenies clarify ancestral relationships not easily identified in large phylogenies and make it easier to identify conserved sequences.