Raphiophoridae


Raphiophoridae is a family of small to average-sized trilobites that first occurred at the start of the Ordovician and became extinct at the end of the Middle Silurian.

Anatomy

All raphiophorids are blind, with headshields that are triangular to subcircular, and many carry long, trailing genal spines, a forward-directed rapier-like spine on the central raised area, or both, with the glabella often inflated and the natural fracture lines of the cephalon coinciding with its margin. The thorax typically has five to seven segments. As mentioned before, all raphiophorids are blind. Many, if not most, genera have no eyes whatsoever, though a few, such as Lehnertia, have vestigial tubercles that correspond to the compound eyes of their ancestors.

Distribution

Raphiophoridae currently includes two officially recognized subfamilies. The nominal subfamily Raphiophorinae originated from the Upper Tremadocian and died out during the Lower Ludlow, and has 217 species assigned to it divided over 26 genera. The subfamily Endymioniinae occurred from the Floian or possibly from the Lower Tremadocian to the Upper Katian and contains 36 species in 13 genera. The time of the first occurrence depends on whether the inadequately known monotypic genus Typhlokorynetes from the Lower Tremadocian of Laurentia is considered an endymioniin. Raphiophorids are generally
found in deep-water sediments, and have a cosmopolitan distribution from the Floian to the Ordovician–Silurian extinction events with diversity peaking from the Darriwilian to the Sandbian. Raphiophorus survived into the Silurian.

Taxonomy

The subfamily Taklamakaniinae was erected to bring together the genera Nanshanaspis, Pseudampyxina, and Taklamakania, on the basis that they all have only three thoracic segments. Analysis of adult anatomy of these genera and larval stages of other raphiophorids showed they most probably developed through paedomorphosis from three different ancestors, so provide an example of parallel evolution. Nanshanaspis closely resembles young Globampyx, Pseudampyxina strongly looks like juvenile Raymondella, and Taklamakania is almost identical to early stages of Ampyxina. Since the three genera of the Taklamakaniinae have been demonstrated to be unrelated to each other, this subfamily is regarded as polyphyletic, and has been synonymized with the Raphiophorinae.

Genera

These genera are assigned to the Raphiophoridae:

Subfamily Raphiophorinae Raphiophorus Angelin, 1854Ampyx Dalman, 1827 Ampyxella Dean, 1960 Ampyxina Ulrich, 1922Ampyxoides Whittington, 1965Bulbaspis Chugaeva, 1956Cnemidopyge Whittard, 1955Damghanampyx Ghobadi Pour, Vidal & Hosseini-Nezhad, 2007Edmundsonia Cooper, 1953Globampyx Fortey, 1975Kongqiaoheia Zhang, 1988Lonchodomas Angelin, 1854Mendolaspis Rusconi, 1951Nanshanaspis Chang & Fan, 1960Pseudampyxina Ju, 1983Raymondella Reed, 1935Rhombampyx Fortey, 1975Taklamakania Zhang, 1980
Subfamily EndymioniinaeEndymionia Billings, 1865 Ampyxinella Koroleva, 1959Ampyxinops Zhang 1979Anisonotella Whittington, 1965Carinocranium Dean, 1989Edmundsonia Cooper 1953Jiuxiella Zhou et al. 1977Lehnertia Vaccari, et al, 2006Malongullia Webby, Moors & McLean, 1970Miaopopsis Lu et al. 1965, synonym = SinampyxinaMiboshania Zhang 1979Pytine Fortey, 1975Salteria Thomson, 1864