We have as yet no satisfactory evidence of the existence of the Cyatheaceae in Palaeozoic floras. It is not until we reach the Jurassic period that trustworthy data are obtained. Raciborski[901] has identified as Cyatheaceous fertile Jurassic fronds from Poland, but his figures are inconclusive. In Alsophila polonica it is not clear whether the annulus is vertical or oblique, and in another supposed member of the family, Gonatosorus Nathorsti, in which the indusium is described as bivalvate, there is no proof of affinity to Cyatheaceae.
In attempting to decipher the past history of the Cyatheaceae it is important to remember the close resemblance between the fertile segments of some species of Davallia (Polypodiaceae) and those of Dicksonia ([fig. 229], C, D, p. 294). Unless the sporangia are well enough preserved to show the position of the annulus, it is frequently impossible to feel much confidence in the value of the grosser features, such as the reduced lamina of the fertile segments and the form of the sori. It is, however, probable that the widely-spread Jurassic species Coniopteris hymenophylloides is correctly referred to the Cyatheaceae, but even in the case of this species the evidence of external form needs confirmation by an examination of individual sporangia.
Coniopteris.
This genus was instituted by Brongniart[902] for fossil fronds characterised by pinnules more or less intermediate between the Pecopteris and Sphenopteris type and agreeing in the form of the sori with the leaves of recent species of Dicksonia. It should be noted that Stur included in this genus a species, Coniopteris lunzensis[903] from the Upper Trias of Lunz, which he regarded as a Marattiaceous fern.
Coniopteris hymenophylloides, Brongn. Figs. 271, [272], [275], B.
| 1828. | Sphenopteris hymenophylloides, Brongniart, Hist. vég. foss. p. 189, Pl. LVI. fig. 4. |
| 1829. | S. stipata, Phillips, Geol. York. p. 147, Pl. X. fig. 8. |
| 1835. | Tympanophora simplex, Lindley and Hutton, Foss. Flor. Pl. CLXX. A. |
| — | T. racemosa, ibid. Pl. CLXX. B. |
| — | Sphenopteris arguta, ibid. Pl. CLXVIII. |
| 1836. | Hymenophyllites Phillipsi, Goeppert, Foss. Farn. p. 256. |
| 1849. | Coniopteris hymenophylloides, Brongniart, Tableau, p. 105. |
| — | Coniopteris Murrayana, ibid. |
| 1851. | Sphenopteris nephrocarpa, Bunbury, Quart. Journ. Geol. Soc. Vol. VII. p. 129, Pl. XII. fig. 1. |
| 1876. | Thyrsopteris Murrayana, Heer, Flor. Foss. Arct. Vol. IV. (2) p. 30, Pls. I. II. VIII. |
The above list represents a small selection of the names applied to Jurassic ferns from different localities which there are good grounds for regarding as referable to a single type[904].
Frond tripinnate; pinnae linear acuminate, attached to the rachis at a wide angle; the pinnules vary considerably in size and shape; in some the lamina is divided into a few broad and rounded lobes ([fig. 275], B) while in others the leaflets are dissected into narrow linear segments. The sori are borne at the ends of veins; the fertile pinnules have a much reduced lamina and, in extreme cases, bear a close resemblance to those of Thyrsopteris elegans ([fig. 229], A, p. 294). The sori are partially enclosed in a cup-like indusium and the sporangia appear to have an oblique annulus.
Venation and habit of frond of the Sphenopteris type.
Fig. 271. Coniopteris hymenophylloides (Brongn.). Nat. size. From a specimen in the Manchester Museum.