The subphylum Hexapoda, known for a common body structure consisting of the famous three pairs of legs, abdomen, thorax and head, is divided into two taxonomic groups: the Entognatha and the the Ectognatha (Sasaki et al., 2013). Within the Entognatha there are the orders Diplura, Collembola and Protura (Sasaki et al., 2013). These are all wingless orders (Sasaki et al., 2013). Entognathas are characterized by entognathia, which is seen as their mouthparts located further inside the head, being enclosed by extensions of the head (Reiger et al., 2004). Within the Ectognatha is the class Insecta (Sasaki et al., 2013). This is further divided into the orders Pterygota, Zygentoma, and Archaeognatha (Sasaki et al., 2013). Ectognathas are classified based on ectognathia, which is the presence of exposed mouths (Sasaki et al., 2013). The relationships between each class and order within the two taxonomic groups are not concrete due to much controversy. After sequencing the ribosomal RNA of the orders Diplura, Protura, and Collumbola, Diplura was found to be closely related to Protura, making them sister groups (Luan et al., 2005). Together, these orders are called “Nonoculata,” referring to their lack of ocular structures (Luan et al., 2005). Collembola have also been found to be closely related to Nonoculata, even making them sister groups (Luan et al., 2005). Based on a study (Nardi et al., 2003) using amino acid sequencing data, the subphylum Hexapoda was considered diphyletic or split into two major taxa (Reiger et al., 2004). These are the taxonomic group Entognatha and the class Insecta (Reiger et al., 2004). Using this sequence data, the class Insecta was found to be most closely related to the subphylum Crustacea...... middle of paper ...... red due to the abundance of marine fossils of early Crustacea (Grimaldi, 2010). Despite this gap in the fossil record, the molecular evidence demonstrating the evolutionary relationship between Hexapoda and Crustacea proves convincing and consistent (Grimaldi, 2010). Molecular and morphological data have been shown to be influential in determining the phylogenetic relationship of Hexapoda and Crustacea. its role in the scheme of evolution. However, when comparing different characteristics of organisms, such as morphology and molecular sequences, many different phylogenies can be created from data analysis (Reiger et al., 2004; Sasaki et al., 2013). The debate to find the most plausible phylogeny will continue, because several accurate phylogenies can be created depending on the researcher's focus (Reiger et al., 2004; Sasaki et al.., 2013).