Cardiopteris.
Schimper[1382] applied this generic name to Lower Carboniferous fronds of a simple-pinnate habit which had previously been described as species of Cyclopteris. Cardiopteris frondosa may serve as a typical example. This species, originally described by Goeppert as Cyclopteris frondosa ([fig. 350]), is recorded from Lower Carboniferous rocks in the Vosges district[1383] in Silesia, Moravia[1384], and Thuringia[1385]. The pinnules, which are attached in opposite pairs to a broad rachis, vary in length from 2 to 10 cm. and have a breadth of 2 to 8 cm.; in manner of attachment and venation they agree with those of Neuropteridium validum. The venation is very clearly shown in a drawing of some large pinnules figured by Stur[1386].
The specimen of Cardiopteris frondosa, a portion of which is shown in [fig. 350] on a slightly reduced scale, was originally figured by Schimper from an unusually good example in the Strassburg Museum. Schimper’s drawing hardly does justice to the original specimen.
A frond bearing rather narrower pinnules, alternately placed on the rachis, which Fritsch has described as Cardiopteris Hochstetterii var. franconica from the Culm of Thuringia, bears a close resemblance to Neuropteridium validum but differs in the entire margin of the pinnules. An Upper Carboniferous species from Russia described by Grigoriew[1387] as Neuropteris, cf. cordata var. densineura, represents another form of similar habit.
Fig. 350. Cardiopteris frondosa (Goepp.). (¾ nat. size. After Schimper.)
Schuster[1388] has recently proposed a new generic name Ulvopteris for a fragment of a pinna from the Coal-Measures of Dudweiler in Germany bearing large pinnules, which he compares with those of Cardiopteris and species of Rhacopteris. The specimen appears to be indistinguishable from some of those already referred to as conforming to Neuropteridium, and it is difficult to recognise any reason for the creation of a new generic name.
We cannot hope to arrive at any satisfactory decision in regard to the precise affinity between Neuropteridium validum and species referred to Cardiopteris and other genera so long as portions of sterile fronds are the only tests at our disposal. It is difficult to determine whether a specimen consisting of an axis bearing pinnules represents a large pinna of a bipinnate frond or if it is a complete pinnate leaf. There is, however, no adequate reason for supposing that the presumably pinnate fronds from the Gondwana Land rocks are generically distinct from the Lower Carboniferous European species Cardiopteris frondosa. Granting the probability that both genera are Pteridosperms and closely allied to one another, the two generic names may be retained on the ground of long usage and in default of satisfactory evidence confirmatory of generic identity. Cardiopteris would thus stand for a type of frond characteristic of the Lower Carboniferous strata of Europe, while Neuropteridium is retained for the Southern species N. validum, and for others from the Trias of the Vosges.