Classification

Domain
The Aratus pisonii is in the Eukaryote domain.  A characteristic that places the tree crab into the Eukaryote domain would be its membrane bound organelles.  This includes organelles within the boundary of the cell membrane including the nucleus and mitochondria.  Eukarya covers a very wide range of organisms including plants, animals and fungi as well as a variety of protozoa including Pyrocystis fusiformis. 

Major Clade
The major clade Opisthkonta plays host to the Aratus pisonii.  The major characteristic represented by the tree crab that places it into this clade is its rear-mounted flagellum.  Fungi, such as Morchella esculentoides, are another member of this clade.

Kingdom
The tree crab falls into the Kingdom Animalia.  Characteristics that make this true include the lack of a cell wall and the absence of chloroplasts.  The tree crab is also heterotrophic, as it does not fix its own carbon.

Phylum
Arthropoda is the phylum to which the tree crab belongs too.  Major characteristics for this include the presence of an exoskeleton, jointed legs and appendages, bilateral symmetry, and a body divided into distinct parts.  Another member of this phylum is Xylocopa virginica, or the eastern carpenter bee.  The tree crab also falls into the subphyla of the Crustaceans.  Synapomorphies of this group include two body regions, five or more pairs of legs, two pairs of antennae, and the ability to reside in both aquatic and terrestrial habitats (Arizona, 1997).

This phylogenetic tree is representing the phyla within the Kingdom Animalia.  The mangrove tree crab is in Kingdom Animalia and falls into the Arthropod  phylum.

Class
The mangrove tree crab falls into the Malacostraca class.  In being in this class, the crab exhibits three main sections including the abdomen, thorax, and the head.  It also has about 19-20 jointed body systems.  Another characteristic of this class is the presence of an open circulatory system (New Hampshire Public Television, 2014).

Order
The order of the tree crab is Decapoda.  Classification here includes the presence of ten legs, as well as a well-developed carapace (Decapod Crustaceans, 1999). 

Family
The tree crab belongs to the family Sesarmidae.  The distinguishing characteristic for this would be the ability of the crab to climb trees in the terrestrial environment (Cumberlidge et al, 2009).

Genus
Aratus pisonii is currently the only species in the genus Aratus.  It characteristic here is the lack of lateral spines on its carapace (Smithsonian, 2009).

Illustrated is a phylogenetic relationship displaying the genera of the family Sesarmidae. (Shubert et al, 2006)

Species
Once again, the tree crab is the only species within its genus, so its distinguishing characteristic separating it from other members of its family is the lack of lateral spines on its carapace (Smithsonian, 2009).

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