A re-examination of the unusual Carboniferous lycophyte species Halonia ichthyoderma Lesquereux (comb. nov.)

Abstract

The only known specimen of Lepidophloios ichthyoderma Lesquereux, from the Pennsylvanian of Illinois, is a stem fragment that has numerous unusual large raised tubercles surrounded by smaller scales. The relationship of these structures to each other was unclear. Reinvestigation by cuticular analysis shows the epidermal structure of both the large protuberant tubercles and the small irregularly interposed small leaves share the same epidermal cell morphology and stomatal pitting. Both the tubercles and the leaves appear vegetative as no reproductive structures were recovered and the presence of stomata on these tubercles may also indicate a vegetative role. This combination of vegetative tubercles and leaves leads to a renaming of the specimen as Halonia ichthyoderma comb. nov. and a redefinition of the genus Halonia Lindley and Hutton is given.