Smirnov, R. V. 2008. Morphological characters and classification of the subclass Monilifera (Pogonophora) and the problem of evolution of the bridle in pogonophorans. Russian Journal of Marine Biology, 34(6), 359-368.
Morphological characters and classification of the subclass Monilifera (Pogonophora) and the problem of evolution of the bridle in pogonophorans
Russ J Mar Biol
World Polychaeta Database (WPolyDb)
This paper presents the results of the revision of the subclass Monilifera (Pogonophora) based on an analysis of all currently known morphological features. The most important diagnostic characters of Monilifera are the presence of two tentacles without pinnules, a neurotroch on the forepart, a fragmented bridle, a transparent rigid tube, the lack of postannular region, and spermatophores. A few characters are newly proposed for the systematics of Monilifera: the length of tentacles, cephalic lobe, and forepart relative to the forepart diameter, average forepart diameter, paired coelom I, the presence of multicellular glands in the prefrenular region of first segment, the lack of muscular ridges of girdles, unfolded and nonconcave opisthosomal growth zone, teethed opisthosomal setae being arranged in four transverse rows or in a circle on each setigerous segment. The modified and expanded differential diagnoses of subclass Monilifera, order Sclerolinida, family Sclerolinidae, and genus Sclerolinum are given. Archeolinum gen. n. is erected to accommodate all moniliferan species, except for Sclerolinum sibogae Southward, 1961, on the basis of bridle and tube structure, as well as the most important morphometric parameters of forepart. All data on the morphology and evolution of the bridle as one of the most peculiar organs of pogonophorans are systematized. A complete series of transformations of the bridle structure is proposed: from plesiomorphic simple cuticular plaques scattered on the forepart dorsal surface to regular plaques with a thickened edge, ridge, and rodlike bodies. The merging of individual cuticular plaques and the reduction of their membranes resulted in the formation of a fused bridle. However, the traces of rodlike bodies and their derivates (the so-called blocks) can be found in many apomorphic bridles. Finally, total reduction of all elements of the initial cuticular plaque, except the thickened edge, led to the formation of a homogenous bridle, which is characteristic of most pogonophorans