Proetidae Hawle and Corda, 1847

Feist, Raimund & Lerosey-Aubril, Rudy, 2005, The type species of Cyrtosymbole and the oldest (Famennian) cyrtosymboline trilobites, Acta Palaeontologica Polonica 50 (3), pp. 465-475 : 466

Family Proetidae Hawle and Corda, 1847 Subfamily Cyrtosymbolinae Hupé, 1953

Remarks.— Hahn et al. (1980) regarded the Cyrtosymbolinae as belonging to the Phillipsiidae Oehlert, 1886 , of which they considered them to be the ancestral rootstock, giving rise to a series of evolutionary lineages that together make up what they presumed to be a monophyletic family. However, in their concept of the Phillipsiidae , they included lineages that have characters that we regard as contradictory. This is the case in particular in cyrtosymbolines, of which fundamental traits such as the generally forwardly tapering glabella, the thorax (where known) with only seven or eight segments, and the semicircular pygidium with relatively few axial rings are not shared by the presumed “derived” younger descendants. Another, perhaps more fundamental difference concerns the early development. In phillipsiids the frontal glabellar lobe reaches as far as, or close to the anterior bor− der, and is parallel−sided (e.g., Paladin shunnerensis ( King, 1914) ( Clarkson and Zhang Xi−guang 1991); Ditomopyge scitula ( Meek and Worthen 1865) ( Pabian et al. 1993: fig. 3: 1, 2, 5, 7); Liobole aff. glabra erdbachensis Hahn and Hahn, 1971 ( Gröning 1986: pl. 1: 1) and Liobole glabra proxima Chlupáč, 1966 ( Owens and Tilsley 1995: pl. 4u) or forwardly expanding (e.g., Hentigia bulbops Haas, Hahn and Hahn 1980 : pl. 4: 7a). In equivalent growth stages of cyrtosymbolines (including the type species of Cyrtosymbole ) the frontal lobe of the glabella is narrow and anteriorly pointed, and there is a long preglabellar field bearing a plectrum−like median groove (e.g., Fig. 2A, B herein). These features are shared by the Proetidae , for example Proetus talenti Chatterton, 1971 , and especially dechenellines ( Chatterton et al. 1999: figs. 1–22), of which the last known representative is the early Late Devonian Clavibole Hahn et al. (1982) assigned by these authors to the Cyrtosymbolinae . We believe, therefore, that it is more appropriate to consider the cyrtosymbolines as proetids rather than phillipsiids, although we do not exclude the possibility that some at least of the latter might originate in certain cyrtosymbolines (e.g., by adaptation to a particular feeding mode).