This generic name was instituted by Stiehler[1290] for impressions of bipinnate sterile fronds, presumably ferns, from Lower Cretaceous rocks near Quedlinburg. The same type of leaf from English Wealden beds had previously been referred by Mantell and other authors to Pecopteris, and by Brongniart to his genus Lonchopteris[1291]. It is, however, advisable to follow Nathorst’s example[1292] and restrict the latter name to Palaeozoic species. As already suggested, it would obviate confusion to substitute a new generic designation for Lonchopteris in the case of Triassic species which are probably members of the Osmundaceae. The type-species of Stiehler, Weichselia Ludowicae[1293], does not differ in any important character from Weichselia Mantelli, the species originally described by Stokes and Webb from the Wealden of England as Pecopteris reticulata.
Weichselia Mantelli (Brongn.)[1294]. Fig. 333.
| 1824. | Pecopteris reticulata, Stokes and Webb, Trans. Geol. Soc. [2]. Vol. I. p. 423, Pls. XLVI. XLVII. |
| 1828. | Lonchopteris Mantelli, Brongniart, Prod. p. 6; Hist. vég. foss. p. 369, Pl. CXXXI. |
| 1894. | Weichselia Mantelli, Seward, Wealden Flora, Vol. I. p. 114. Pl. X. fig. 3. |
| 1899. | Weichselia reticulata, Fontaine, in Ward, Ann. Rep. U. S. Geol. Surv. p. 651. |
Frond bipinnate, rachis broad; pinnae very long, of uniform breadth and with prominent axes; pinnules crowded, entire, with obtuse apex, usually oblong but more or less triangular or rounded towards the distal ends of the pinnae. The pinnules, which may reach a length of 9 cm., are characterised by a fleshy lamina attached by the whole breadth of the base; the two rows of segments on each secondary rachis are usually inclined towards one another so that they form with the axis of the pinna a wide-open V instead of lying in one plane ([fig. 333], C). From a median rib are given off numerous anastomosing branches ([fig. 333], B).
Fig. 333. Weichselia Mantelli.
- Part of a frond from the Wealden of Sussex, England. (British Museum; v. 2630. ¾ nat. size.)
- Pinnule from Bernissart, Belgium (× 3).
- Weichselia erratica, Nath. Section of pinna. (After Nathorst.)
This characteristic Wealden species is recorded from England, Germany, France, Belgium, Austria, Russia, Bornholm, North America, and Japan. It is by no means certain that Weichselia Mantelli is a true fern: no satisfactory evidence of fructification has been adduced.
The broad and strong rachis is comparable with that of a Cycadean leaf and the thick lamina suggests a plant of xerophilous habit. I have retained the specific name Mantelli on the ground of long established usage instead of following Fontaine in his adherence to strict priority.