Fronds large, bipinnate or tripinnate, the main rachis, which may be dichotomously branched, bears long linear pinnae with broadly linear or deltoid pinnules, acute or blunt, attached by the whole of the base; the lower margin of the lamina, which is usually entire and rarely lobed (e.g. Odontopteris osmundaeformis)[1478], is often decurrent on the axis of the pinna. The basal pinnule of each pinna is frequently attached by a contracted base, and the lamina may differ in form from that of the normal segments. Pinnules often occur on the main rachis, and in some species the petiole bears modified pinnules which are larger than the ultimate segments of the pinnae and in some cases Cyclopteroid in shape. The pinnules are traversed by numerous dichotomously branched veins; if a midrib is present it dies out in the basal part of the lamina. In some species (genus Mixoneura) pinnules of the Neuropteroid type, characterised by a well-defined midrib, occur in association with typical Odontopteroid pinnules on the same pinna.
Fig. 365. Odontopteris minor, Brongn. (Rather less than ⅓ nat. size. After Zeiller.) [The pinnules are omitted in the right-hand branch.]
The species represented in [fig. 364], C, D, from the Middle Coal-Measures of Barnsley, Yorkshire, illustrates the form and venation of the Odontopteris type of pinnule. Another species, O. Reichiana Gutb.[1479], is also recorded by Kidston from the Lower Coal-Measures of Lancashire. Some unusually good specimens of the type-species of the genus Odontopteris minor, Brongn., have been figured by Zeiller[1480] from the Coal-Measures of Blanzy ([fig. 365]) which show the dichotomy of the main axis and the occurrence of Aphlebiae on the petiole. The late Dr Weiss[1481] divided Odontopteris into two sections, Xenopteris and Mixoneura, the pinnules of the former having the form shown in [fig. 364], D; while in species of the latter sub-genus some of the pinnules are identical in form and venation with those of Neuropteris except that they are attached by the whole breadth of the base. Zeiller[1482] employs Mixoneura as a generic designation. In an American species O. Wortheni Lesq.[1483] the pinnules bear numerous hairs like those on some species of Neuropteris ([fig. 373], p. 570). The large size of the fronds of Odontopteris suggested to Weiss[1484] that they were borne on the stems of tree-ferns, but Grand’Eury’s[1485] examination of specimens in the Coal-beds of central France led him to picture the plant as bearing a tuft of leaves on a short subterranean stem. Renault and Zeiller[1486], on the other hand, obtained evidence in the Commentry Coal-field of fronds borne on elongated stems which grew on the ground and were supported by stronger plants. Stur[1487] was the first to suggest that Odontopteris should be excluded from the ferns. Grand’Eury’s[1488] supposed fertile pinnules of Odontopteris do not afford any satisfactory evidence of the sporangial nature of the small swellings which he figures at the ends of the veins. This author pointed out several years ago that the petioles of some species of Odontopteris possess the anatomical features of Myeloxylon, a type of leaf-stalk which is now known to belong to Pteridosperms. In a recent paper Grand’Eury[1489] records the association of Odontopteris fronds with small seeds (Odontopterocarpus), a discovery which leaves little or no doubt as to the Pteridospermic nature of the genus. The fronds of Odontopteris are very similar in habit to those of Neuropteris, another Pteridospermic genus.
The similarity between some Odontopteris and Thinnfeldia leaves, to which attention has already been called, is well illustrated by O. genuina Grand’Eury[1490], a pinnule of which is represented in [fig. 366], A. Odontopteris is a fairly widespread genus in Upper Carboniferous and Lower Permian rocks, and is recorded also from Triassic strata: it is represented in the Coal-fields of North America and in several parts of Europe[1491].
In some fronds included in Odontopteris the pinnae are characterised by a broad irregularly lobed lamina which also forms a winged border to the rachis. Examples of this form are afforded by Odontopteris Browni Sew.[1492] from the Burghersdorp Series (Triassic?) of Cape Colony, and O. Fischeri described by Brongniart[1493] from the Permian of Russia. The Russian species would perhaps be more appropriately placed in the genus Callipteris, as Weiss[1494] suggests; the absence of venation in O. Browni renders generic identification unsatisfactory.
Fig. 366.
- Odontopteris genuina (Grand’Eury). (× 2⅝. After Renault and Zeiller.)
- Callipteridium gigas (Gutb.). (× 2⅝. After Zeiller.)
- Callipteris Pellati (Zeill.). (× 1¾. After Zeiller.)
- C. lyratifolia (Goepp.). (× 1¾. After Zeiller.)