Identification Resources

• Shell plates i though to viii need to be observed, and there distance from one another noted (are the separated or touching?)
• The two main layers of the plates need to be closely observed the top layer called the tegmentum and the ventral layer called the articulamentum. In some genres the tegmentum is largely reduced (for example the species Cryptoplax larvaeformis). To measure the degree of reduction in the tegmentum it is important to use the head plate due to is symmetrical nature. The thickness of these layers vary among different species and is also important to note.
• The posterior margins of the head plate are important, and differ between an almost straight margin and a V-shape.
• The tail plate can sometimes be used in isolation to identify a species, as it has a mucro (a center point or an apex). Identification depends on the position of the mucro in relation to the valve length, and whether it is elevated or not.
• Aesthetes are important to the identification of an individual, there are different types of Aesthetes and they reflect the growth of Chitons shell plates, therefore are indicative of genus and species. 

• The girdle of Chitons is adapted to lifestyle, therefore appropriate modifications have been made. These modifications may aid in the identification of an individual.

•  Do the gills of the individual extend along the entire length of the foot, or are they restricted to the posterior half? These states are known as holobranchial and merobrancial respectively are key tools identification.
  
• The direction and extension of the gill rows are important in identification, so to is the the position of the last row of gills in regards to the anus.