In some, mostly small species of Monogynaspida, 3–4 small (often comma-shaped) structures that refract light can be found under the dorsaldorsal:
relating to the upper or back side; opposed to ventral.
hexagonal region of the podonotal shieldpodonotal shield:
the anterior shield in mesostigmatans with divided dorsal shields. 
. These structures appear to be hypertrophied muscle attachments and are called scleronodules (scleronoduliscleronoduli:
3-4 light refractile structures, sometimes comma-shaped, in the podonotal region of many Rhodacaroidea and the genus Protogamasellus (Ascidae) in the Mesostigmata. 
). They are found in most Rhodacaridae (except Protogamasellopsis), Digamasellidae (except Digamasellus), and some Ascidae (Protogamasellus) and Ologamasidae (rarely in some Gamasellus and undescribed genera). Except in Rhodacarus and Protogamasellus, where the median pair appears to have fused into a single structure, two pairs of scleronoduliscleronoduli:
3-4 light refractile structures, sometimes comma-shaped, in the podonotal region of many Rhodacaroidea and the genus Protogamasellus (Ascidae) in the Mesostigmata. are present.
Author: David E. Walter
Content last updated Sept. 2006, unless indicated otherwise
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