Nodes and internodes in particular are diagnostic. The features that can be observed in feather barbule fragments are: shape of nodes, distance between nodes, presence and shape of prongs, and pigmentation.In some groups of birds, the characteristics of downy feather barbules can be used to identify order, family, and sometimes even species (Dove and Koch 2010 Dove and Peurach 2002).Downy barbules are found in the plumulaceous region at the base of wing, tail, contour, and semiplume feather types, and throughout the length of down feathers. The downy barbule is a long subunit of the feather structure with tiny branches.Note radii grooves radiating out from central focus, and concentric circuli Fish scales were diagnostically identifiable with VLM.įigure 22: Cycloid scale from a tench ( Tinca tinca) present on flint used to descale the fish, reference collection.Thus, another flake from a wider reference collection created by SC containing scales is illustrated instead (Figure 22), showing a similar species of Cyprinid fish scale (tench, Tinca tinca) scale on a flake.
Unfortunately, no scales were found on the reference collection flint flake used on the Cyprinid fish.Only a cycloid type of scale was examined.( 2013) state that a feature of fish scales is that they are birefringent in normal light and non-birefringent under cross-polarised light. Fish species determination from a scale may be possible based on knowledge of species present in the geographical area of the site in conjunction with consultation of fish-scale reference collections.Ctenoid scales are similar to cycloid but additionally have posterior projections, such as a stiff-comb, cilia, or tubercles, modifications which are collectively called granulation (Elliott 2000, 102). Cycloid scales are circular, thin, smooth, and flat. The diagnostic features of cycloid and ctenoid scales are: focus, calcified concentric ridges called circuli, and radii grooves radiating from centre focus (Lagler 1947). It has been argued that cycloid and ctenoid scales contain enough morphological features to be used for identification purposes in archaeology (Casteel 1974, 560).Ganoid scales are typically rhomboid or diamond-shaped and have articulating peg and socket joints between them.Shark placoid scales have a raised pedestal and winged keel that reduces drag during swimming. Placoid scales, also known as dermal denticles, are platelike and have a rectangular base and spines.Most freshwater fish have Cycloid scales (Casteel 1974, 557). Cycloid and ctenoid scales are found in the majority of bony fishes (superclass Osteichthyes) (Elliott 2000, 100).Ganoid scales are found in the gars, bichirs, bowfin, and the caudal regions of sturgeons and paddlefishes.Placoid scales are found in the cartilaginous fishes (class Chondrichthyes).There are three main types of extant fish scales: placoid, ganoid, and cycloid and ctenoid, which are considered together because they are both derived from ganoid scales (Helfman et al.
0 kommentar(er)
