SPHENOPSIDA 95 



Hyeniales 



Until 1957 the earliest known representatives of the Sphen- 

 opsida were Hyenia and Calamophyton, both of which are of 

 Middle Devonian age, but in that year Ananiev discovered 

 the remains of a most interesting plant in Lower Devonian 

 rocks of western Siberia. This he named Protohyenia (Fig. 

 1 5 A). Although lacking some of the features which are 

 characteristic of the Sphenopsida, yet, as the generic name 

 suggests, it might well represent an early ancestor of the 

 group. From a creeping axis, erect branches arose at inter- 

 vals, bearing either sterile or fertile appendages in rather 

 indefinite whorls. The sterile appendages forked several 

 times and, although having the appearance of tiny lateral 

 branches, they probably functioned as leaves. The fertile 

 appendages were very similar, but terminated in sporangia. 

 These were unUke those of almost all other members of the 

 Sphenopsida, in that they were not reflexed. 



Hyenia elegans (Fig. 15E) had a similar growth habit, as 

 we now reahze from the work of Leclercq,^^ for it had a stout 

 horizontal rhizome bearing roots and erect aerial stems up to 

 30 cm high, some sterile and others fertile. The sterile axes 

 bore whorls of forking appendages, alternating at successive 

 nodes and, as in the case of Protohyenia, it is difficult to 

 decide whether they should be regarded as leaves or as stems 

 performing the functions of leaves. The fertile axes bore 

 whorls of sporangiophores (Fig. 15F), which were similar to 

 the 'leaves', except that two segments were reflexed and 

 usually terminated in two sporangia each. 



Other species of Hyenia are known, in which the aerial 

 axes were branched and which, therefore, resembled quite 

 closely the other Middle Devonian genus Calamophyton. 

 The illustration of C. primaevum (Fig. 15B) is taken from an 

 early description^^ which emphasizes the articulate nature of 

 the aerial axes, a feature which used to be regarded as 

 essential in defining the genus. However, other species, e.g. 

 C. bicephalum, are not so clearly articulated and it has been 



