Spatial and temporal variation in statolith and protoconch
trace elements as natural tags to track larval dispersal.
Although Mutvei (1961) did not place his new genus Lyecoceras in a family, the slightly curved cup-like protoconch
that possesses a cicatrix (Mutvei 1957, pl.
elongated, smooth, shining, ~2 whorls; boundary between protoconch
and teleoconch well-defined, orthocline (Fig.
The smooth protoconch
and nature of the ribs appear to be that of Palaeozygopleura.
The main reasons for the assignment of rostroconchs to the molluscs are the presence of a protoconch
, calcareous shell with the growth lines and the prominent muscle scars, which also show growth increments (Pojeta & Runnegar 1976).
size variation along depth gradients in a planktotropic Epitonium.
The taxon was defined on the basis of a few shell characters, namely a spirally sculptured protoconch
, a teleoconch with regularly spaced axial ribs and spiral lines in the interstices, a biconical shell shape, and a paucidentate aperture (Pilsbry 1919).
Diagnosis: A small species of Avakubia, differing from similar-sized congenerics by a combination of conchometrical characters, as well as by the large number of spiral cords on the protoconch
Serpulidae, Sabellidae, Cirratulidae) do not have a bulb-like, closed, embryonic chamber that is characteristic of Palaeozoic tubeworms and which resembles the protoconch
of mollusks and the protoecium of bryozoans (ten Hove & van den Hurk 1993; Taylor & Vinn 2006; Fig.
Shell height and diameter measurements as well as protoconch
dimensions and whorl counts were measured using the methods set out by Herbert and Moussalli (2010).
The dimensions of the protoconch
were measured according to the method set out previously (Herbert 1987).
is more exsert and evidently less strongly sculptured, the juvenile microsculpture sometimes granular rather than vermiform and, at least in H.