Callixylon wendtiisp. nov., a new species of archaeopteridalean progymnosperm from the Late Devonian of Anti-Atlas, Morocco

Abstract

Archaeopterid trees were the main components of most Late Devonian forests. Their aerial axes characterised by a eustele with mesarch primary xylem strands, leaf traces departing radially from cauline bundles and secondary xylem tracheids with radial pits arranged in groups, are referred to the genus Callixylon Zalessky. The nineteen species of Callixylon described to date from North America, North Africa, Europe, Xinjiang and several parts of Russia range from the late Givetian to the Mississippian. In this paper, we describe a new species of Callixylon from two specimens collected in the Famennian locality of Mader el Mrakib in eastern Anti-Atlas. Callixylon wendtii sp. nov. is characterised by the presence of sclerotic nests in the pith, a new character for the genus. Its wood shows narrow rays of variable height, with unevenly distributed ray tracheids. Small vascular traces crossing the wood within the two innermost growth rings are interpreted as evidence for short-lived leaves. This discovery adds to the diversity of the genus Callixylon in an area of northern Gondwana that may have been favourable to the establishment of a diverse community of archaeopterid trees.

Stem Anatomy Confirms Tingia unita Is a Progymnosperm

“…However, the anatomical information of its stem is quite different from T. unita . For example, Callixylon as the fossil stem of Archaeopteris has eustelic vascular system, one critical feature of Callixylon is that the circular bordered pits are grouped together in radially aligned rows and are multiseriate on the radial tracheid walls of secondary xylem, and the adjacent groups of pits are separated by unpitted areas [ 21 , 54 , 55 , 56 ]. Whereas, the pitting of T. unita is mainly scalariform, uniseriate, and continuous, distributing on the radial tracheid walls of secondary xylem.…”

A Late Devonian plant assemblage from New South Wales, Australia: Diversity and specificity

“…Callixylon woods with narrow rays characterized by ray tracheids that are lacking or rare are affiliated to the informal "Trifilievii" group of Orlova and Iurina (2011), which includes C. trifilievii and several junior synonyms, C. brownii and C. whiteanum. Woods referrable to this group are known from all the paleocontinents were Callixylon has been reported (Tanrattana et al, 2019). Without any information on its stelar characters, the Barraba log cannot be referred to a particular species.…”

“…To address these issues, recent efforts have been made to document more systematically Gondwanan floras of Late Devonian-Early Carboniferous age from low and high paleolatitudes. These studies have focused on localities in South America (Prestianni et al, 2015), Africa (Decombeix and Galtier, 2017;Gess and Prestianni, 2018;Prestianni and Gess, 2019;Tanrattana et al, 2019) and Australia (Galtier et al, 2007;Decombeix et al, 2011b;Evreïnoff et al, 2017;Champreux et al, 2020;Meyer-Berthaud et al, 2021). The plant locality discovered at Barraba (New South Wales) in January 1964 by an amateur geologist, Mr. John Irving, is a rare Late Devonian locality in Australia yielding permineralized specimens associated with adpressions.…”