Ibyka Amphikoma, Gen. Et Sp. N., a New Protoarticulate Precursor From the Late Middle Devonian of New York State

Abstract

Ibyka gen. n. is described from late Middle Devonian compressions and petrifactions collected in eastern New York State. It is a robust plant of which three orders of branching and ultimate appendages (leaves) are known. The latter dichotomize up to five times, are arranged spirally on all orders of branching, are three‐dimensional, and all orders are terete in cross section. Fertile appendages, homologous with the sterile, are terminated by sporangia. The protostele has five or six arms, the maturation is mesarch, and the protoxylem disintegrates leaving lacunae at the tips of the arms. Traces to appendages are terete and arise spirally from the tips of the arms. The primary xylem consists of tracheids only, the phloem of thin‐walled cells and probable tanniniferous cells. The cortex consists of parenchyma and groups of sclereids. Secondary xylem is lacking. Ibyka is placed in a new order, Ibykales, close to the Hyeniales (protoarticulates) and to the Pseudosporochnales all three of which probably evolved from Trimerophytina.

Land plant evolutionary timeline: Gene effects are secondary to fossil constraints in relaxed clock estimation of age and substitution rates

“…The earliest fossil occurrence of ferns corresponds to Ibyka , a possible stem relative of Equisetum (Kenrick and Crane, 1997) from the Middle Devonian (Givetian; ca. 392–385 Myr; Skog and Banks, 1973). The age interval here estimated for ferns (401–385 Myr) closely corresponds to the Middle Devonian, with the mean age (392 Myr) falling in the Eifelian.…”

Overcoming among‐lineage rate heterogeneity to infer the divergence times and biogeography of the clubmoss family Lycopodiaceae

“…The euphyllophyte crown node was assigned a minimum age of 385 Ma based on Ibyka, dating to the Middle Devonian (Skog & Banks, 1973), which has affinities to the fern lineage (Kenrick & Crane, 1997). The divergence of the Equisetales from the remainder of the ferns was given a minimum age of 346 Ma, given the occurrence of the Equisetalean Archaeocalamites in the Lower Carboniferous (Bateman, 1991).…”

Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences

“…The Late Devonian to Early Carboniferous cladoxylopsids (e.g., Iridopteridales and Pseudosporochnales), which have characteristics of both ferns and horsetails, are almost certainly among the stem groups (Fig. 2) of the monilophytes (Skog and Banks, 1973;Stein et al, 1984;Berry and Stein, 2000;Hilton et al, 2003).…”