Archaeopteris macilenta, Anatomy and Morphology of Its Frond

Abstract

The stem, rachides, and pinnae of Archaeopteris macilenta, formerly considered to be a fern of Devonian age, comprise a branch system in which the ultimate divisions heretofore referred to as pinnules are the leaves. The primary vascular system of the "frond" is a lobed siphonostele from which leaf traces arise in a,spiral sequence. The anatomy of the "rachis" and of the "pinnae" is shown to be similar to that of the stem, Callixylon, which bore these "fronds." Branching, epidermal pattern and stomates are described for the spirally arranged leaves (fertile pinnules). Attachment and dehiscence of sporangia as well as their stomates are reported. Archaeopteris is retained in the Class Progymnospermopsida which includes plants with gymnospermous anatomy and pteridophytic reproduction. It is suggested that Actinopodium, Svalbardia and Siderella are related closely to Archaeopteris and that this group of genera shows evolutionary stages in webbing of leaves and planation of branch systems. The opportunities for ontogenetic studies of the arborescent genus Archaeopteris are pointed out.

Anatomical reinvestigation of Archaeopteris macilenta from the Upper Devonian (Frasnian) of South China

“…The axes of A. macilenta bear abundant vegetative and/or fertile leaves, which are preserved as impressions, compressions, and limonitic permineralizations in white-gray silty mudstone. New York, West Virginia (USA); Bear Island (Norway); Moresnet, Booze-Trembleur, Evieux, Durnal (Belgium); Altai-Sayan (Russia); Anhui, Guangdong (China) Radchenko, 1962;Carluccio et al, 1966;Phillips et al, 1972;Li et al, 1984;Cai et al, 1987;Kenrick & Fairon-Demaret, 1991;Fairon-Demaret et al, 2001;Osborne et al, 2004;Gutak et al, 2011 A. hibernica Kiltorcan (Ireland); New York (USA); Southeastern Mountainous Altay (Russia) Carluccio et al, 1966;Dawson, 1871;Gutak et al, 2011 A. obtusa New York (USA); Ellesmere Island (Canada) Carluccio et al, 1966;Gensel & Andrews, 1984 A. macilenta (A. fimbriata)…”

“…New York, West Virginia (USA); Calgary (Canada); Bear Island (Norway); Heist-op-den-Berg (Belgium); Southeastern Mountainous Altay (Russia); Jiangsu, Hubei (China) Arnold, 1936;Carluccio et al, 1966;Andrews, 1970;Beck, 1971;Phillips et al, 1972;Scheckler, 1978;Wu et al, 1982;Cai, 1981;Feng, 1984;Hao & Mei, 1987;Yang, 1987;Yang, 2005;Osborne et al, 2004;Gutak et al, 2011 A. sphenophyllifolia New York (USA); Heilongjiang (China) Carluccio et al, 1966;Cai, 1981 A. fissilis Ellesmere Island (Canada); Southeastern Mountainous Altay (Russia) Gensel & Andrews, 1984;Osborne et al, 2004;Gutak et al, 2011A. howitti Australia White, 1986 Eastern Cape (South Africa) Anderson et al, 1995 Archaeopteris sp. America; China; Canada; Columbia; Russia; Venezuela Beck, 1971;Cai, 1981;Osborne et al, 2004 Note: This Two permineralized axes, ca.…”

“…Many species of Archaeopteris have been documented (Table 1) and their identification depends on morphology (especially vegetative leaves), although this method has, to a certain extent, been doubted (Carluccio et al, 1966;). Archaeopteris roemeriana from Europe is very similar to A. halliana from North America in morphological characters, for example, spiral arrangement of leaves, entire and slightly uneven vegetative leaves, and non-laminated fertile leaves (Arnold, 1939;Stockmans, 1948;Phillips et al, 1972;Kenrick & Fairon-Demaret, 1991), despite that the anatomy of A. halliana is presently unknown.…”

“…Kräusel & Weyland (1941) and Fairon-Demaret et al (2001) proposed that these two species are synonymous. In addition, A. macilenta and A. fimbriata are gathered under a single species and the former specific epithet has priority (Carluccio et al, 1966).…”

“…In previous studies, the anatomy of lateral axes of Archaeopteris is entirely based on A. macilenta, A. roemeriana, and some specimens identified as A. sp. (Carluccio et al, 1966;Beck, 1971;Scheckler, 1978;Kenrick & Fairon-Demaret, 1991). Concerning A. macilenta, most ultimate axes contain protostele, whereas the penultimate axes usually have eustele and secondary xylem (Carluccio et al, 1966;Beck, 1971;Scheckler, 1978).…”