Pterocyrtidium was named by Bütschli (1882) [Pterocyrtidium (n.gen). (Pterocanium Ehr. pro partim). The definition of this group is rather difficult. The species examined here can easily be related to the true Eucyrtidiids having 3 segments (figs. 28, 29) by their general structure, but they are distinguished in having a first segment with three or two medium-sized horns related to the internal spines. The problem is that we have attributed a primitive character to the same structure of the three external horns in the two-segmented Lithomelissa, so that these forms could originate from Lithomelissa. In this case, grouping Pterocyrtidium within the Eucyrtidiids (as it is done here) would infer that the three horns of Lithomelissa are extending inside to the collar plate, which is not true. If we consider that the Eucyrtidiid grouping is right, we can, thus, think that the three horns of Pterocyrtidium do not correspond to the three primary spines of the opening that, in our opinion, are developped in the shell wall, but that they are secondary structured issued from the spines growing inside the wall and diverging outside. Until now, I have examined two forms of this kind, one seeming new (fig. 28a-b) that I have named Pterocyrtidium zitteli, n. sp., the second one being Pterocyrtidium barbadense Ehrenberg. These two forms have a cephalis of well-marked zygocyrtid structure. Figure 28a shows a well-preserved primary ring. These two species will probably form a group with Pterocanium sabae (= probably Eucyrtidium ? carinatum Hck.), Pterocanium apis Ehrenberg, ?Pterocanium falciferum Stöhr, and ? Pterocanium bibrachiatum Stöhr. To this group should be added Dictyoceras virchowii with a porous shell that can only be considered as a secondary characteristic. Translation by J.P.C.]] Remarks on original description: [Campbell [1954, p.D87] designates Pterocorys campanula Haeckel, 1887a as the type species of Pterocyrtidium. However, this seems inappropriate as this species was not among those included at the time of the genric definition. Species included at that time are: Lithornithium dictyoceras Haeckel,1860b; Pterodon apis Ehrenberg, 1873a; Pterocytidium zitteli Butschli, 1882b; Pterocanium barbadense Ehrenberg, 1873; P.sabae Ehrenberg, 1872a.]. Its type is Pterocanium barbadense. It was considered monophyletic by Bütschli (1882).

It was assigned to Lophocyrtiidae by Bütschli (1882).