|Title||Identifying patterns of diversity of the actinopterygian fulcra|
|Publication Type||Journal Article|
|Year of Publication||2009|
|Journal||Acta Zoologica (Copenhagen)|
|Keywords||Chordata: general and systematic - Pisces 63000, Geological periods - Devonian 64720, Geological periods - Jurassic, Integumentary system - Physiology and biochemistry 62510, integumentary system integumentary system Osteichthyes  Chemical Coordination and Homeostasis Integumentary System Paleobiology fin rays scutes ridge scales fulcra Pisces Vertebrata Chordata Animalia 18504, Paleobiology 64712, Paleozoology 64500|
Fin rays, scutes or ridge scales, and fulcra have been traditionally interpreted as modified scales, but their diversity has been almost ignored. Based on results presented here, revised definitions of these elements are provided. At least two patterns of basal fulcra are found in actinopterygians: in Pattern I all or most basal fulcra are paired elements, whereas in Pattern II, a series of unpaired basal fulcra that are bifurcated proximally, and whose forking gradually becomes larger caudad, are followed by a series of paired elements. Basal fulcra are commonly present on unpaired fins of lower actinopterygians, including basal neopterygians. Among living fish they are absent in polypteriforms, Amia and teleosts. Fringing fulcra are always paired. Three patterns of fringing fulcra series are described: the series of fringing fulcra in basal actinopterygians is formed by expanded terminal segments of marginal lepidotrichia (Pattern A). Another series is formed by a combination of slightly expanded or modified terminal segments of rays and independent spiny, small elements (Pattern B). The third series is formed of small, spiny ossified elements positioned along the leading marginal fin ray(s) (Pattern C). Other patterns of basal and fringing fulcra remain to be investigated, along with their phylogenetic implications.