Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Anomura
Superfamily: Paguroidea, Latreille, 1802

    * Coenobitidae
    * Diogenidae
    * Lithodidae
    * Paguridae
    * Parapaguridae
    * Pylochelidae
    * Pylojacquesidae

Pargurus History

McLaughlin et al. (2004) provides a comprehensive analysis of evolution in the Infraorder Anomura.  They refute the long-withstanding claim that Pagurus was the ancestoral for of lithodids (King Crab, see picture), the notion comically characterized as “the lowly hermit to the majestic king”.  They generated a Cladogram (not shown) obtained from analysis of “postlarval” semaphoront, which gave a possible relation of the families with the Infraorder.  A notable feature is the seperation of the genus pagurus and lithodes, which invalidates the assertion that hermits were ancestral to king crabs. 

Shell-Selection HistoryKing Crab

Furthermore the Lopholithodes, Paralomis and Lithodes share heavy calcification as a common trait, with the sister family Hapalogaster being less calcified; Pagurus is characterized by very little calcification.  Calcification is an important feature because its absence may explain the rise of inhabitation of an exogenous gastropod shells (McLaughlin et al., 2004).  Figure 2 shows different genuses separated in light of varying levels of calcification.  The authors note that all the relevant data do not show whether evolution is happening towards or away from hermit crabs.  Thus, it is unclear whether exogenous shells or calcium-fortified bodies are preferred by natural selection.

Figure 1. Picture of Two King Crabs

Figure 2. Cladogram for Infraorder Anomura with emphasis on the evolutionary seperation of King Crabs and Hermit Crabs. The Cladogram was generated based on level of calcification of crab bodies.