articulamentum

articulamentum

[är‚tik·yə·lə′men·təm]
(invertebrate zoology)
The innermost layer of a calcareous plate in a chiton.
References in periodicals archive ?
Comparison and remarks: This species was originally placed in the genus Lepidochitona, mainly due to the morphology of the ventral girdle scales and to the characters of the articulamentum, but was later considered as belonging to Chaetopleura (see Rolan 2005; Sirenko 2006).
A unique head valve from ST03 has a shell scar due to injury, which caused the development of a new insertion plate under the older one in the articulamentum.
Canals close to the articulamentum layer curve upward around the layer and run longitudinally parallel to the dorsal surface before curving to the dorsal surface or extending to the anterior margin.
In Euleptochiton spatulatus the articulamentum layer is restricted to narrow triangular areas extending from the apex on the posterior margin of the intermediate plates and the mucro on the tail plate to the anterior margin forming prong-like extensions called sutural laminae (Fig.
In the intermediate and tail plates the presence of the articulamentum layer, which is not penetrated by the canals, causes changes in the canal shape and orientation as they curve around and extend over the articulamentum layer.
In intermediate plates the transverse sections show canals that are slightly curved in the lateral portions of the plates and are more strongly curved beside the articulamentum layer (Fig.
Articulamentum well developed, whitish, apophyses evenly rounded, jugal sinus wide, slit formula of insertion plates 9-10/1/8-10, slits inequidistant, slit rays distinctly punctured, teeth sharp, smooth, eaves solid (Fig.
Articulamentum white, insertion plates well developed, apophyses short and trapezoidal, more triangular in valve ii.
Articulamentum white, strongly developed, forming large insertion plates.