Rooting portions of a young pseudosporochnalean from the catskill delta complex of New York

Premise of research. Pseudosporochnales (Cladoxylopsida) were conspicuous elements of the Earth’s earliest forests. Recent evidence has done much to clarify basic aspects of the pseudosporochnalean architecture, but important questions remain about the developmental processes responsible for growth from juvenile individuals to trees of sometimes considerable size. Methodology. Presented here is combined compression/permineralization evidence of a young member of the group from a late Devonian (early Frasnian) locality also containing Eospermatopteris (Wattieza), currently the largest reconstructed pseudosporochnalean tree. Standard pyrite preparations were made and analyzed with reflected light. Pivotal results. The anatomically preserved portion of the trunk with an expanded base lacking a central vascular column shows abundant evidence of appendages with apparent rooting function supplied by traces comprised of primary and often secondary xylem. Traces arise within parenchyma near the trunk center and follow lax courses with multiple divisions outward and downward to the surface, finally enveloping the plant base for some distance. In the upper portion of the specimen, likely near the transition between the base bearing rooting appendages and the aerial shoot, the traces form a vascular plexus toward the periphery of the stem, with the bulk of vascular tissues comprising secondary xylem. Similar but differently oriented vascularization also occurs near the base. Conclusions. Here we hypothesize a unique form of “bipolar” development in this specimen, and potentially all pseudosporochnaleans, by means of a trunk base bearing an appendicular system of positively geotropic rooting appendages. In addition, we hypothesize that diffuse meristematic activity of the base plus the vascular plexus may have a previously unrecognized role in the development of pseudosporochnaleans from the small specimen observed here to large body size. We also suggest that this tissue offers an explanation for the enigmatic genus Xenocladia known from tissue fragments of large size found in coeval marine sediments of New York State. Given current incomplete understanding of development within the Pseudosprochnales, considering the rooting system as sui generis confers the advantage of adequate description of this organ, without necessarily specifying correspondence or homology with other groups

Surprisingly complex community discovered in the mid-Devonian fossil forest at Gilboa

The origin of trees by the mid-Devonian epoch (398–385 million years ago) signals a major change in terrestrial ecosystems with potential long-term consequences including increased weathering, drop in atmospheric CO2, modified climate, changes in sedimentation patterns and mass extinction1, 2, 3. However, little is known about the ecology of early forests or how changes in early terrestrial ecosystems influenced global processes. One of the most famous palaeontological records for this time is the ‘oldest fossil forest’ at Riverside Quarry, Gilboa, New York, USA, discovered in the 1920s4, 5. Hundreds of large Eospermatopteris sandstone casts, now thought to represent the bases of standing cladoxylopsid trees6, were recovered from a horizon that was originally interpreted as a muddy swamp. After quarry operations ceased, relatively minor outcrops of similar fossils at nearby localities have provided limited opportunities to evaluate this pervasive view using modern methods7, 8. In 2010, removal of the quarry backfill enabled reappraisal of the palaeoecology of this important site. Here we describe a 1,200 m2 map showing numerous Eospermatopteris root systems in life position within a mixed-age stand of trees. Unexpectedly, large woody rhizomes with adventitious roots and aerial branch systems identified as aneurophytalean progymnosperms run between, and probably climb into, Eospermatopteris trees. We describe the overall habit for these surprisingly large aneurophytaleans, the earliest fossil group having wood produced by a bifacial vascular cambium. The site also provides evidence for arborescence within lycopsids, extending the North American range for trees in this ecologically critical group. The rooting horizon is a dark grey sandy mudstone showing limited root penetration. Although clearly belonging to a wetland coastal plain environment9, the forest was probably limited in duration and subject to periodic disturbance. These observations provide fundamental clarification of the palaeoecology of this mixed-group early forest, with important implications for interpreting coeval assemblage data worldwide

Surprisingly complex community discovered in the mid-Devonian fossil forest at Gilboa

The origin of trees by the mid-Devonian epoch (398–385 million years ago) signals a major change in terrestrial ecosystems with potential long-term consequences including increased weathering, drop in atmospheric CO2, modified climate, changes in sedimentation patterns and mass extinction1, 2, 3. However, little is known about the ecology of early forests or how changes in early terrestrial ecosystems influenced global processes. One of the most famous palaeontological records for this time is the ‘oldest fossil forest’ at Riverside Quarry, Gilboa, New York, USA, discovered in the 1920s4, 5. Hundreds of large Eospermatopteris sandstone casts, now thought to represent the bases of standing cladoxylopsid trees6, were recovered from a horizon that was originally interpreted as a muddy swamp. After quarry operations ceased, relatively minor outcrops of similar fossils at nearby localities have provided limited opportunities to evaluate this pervasive view using modern methods7, 8. In 2010, removal of the quarry backfill enabled reappraisal of the palaeoecology of this important site. Here we describe a 1,200 m2 map showing numerous Eospermatopteris root systems in life position within a mixed-age stand of trees. Unexpectedly, large woody rhizomes with adventitious roots and aerial branch systems identified as aneurophytalean progymnosperms run between, and probably climb into, Eospermatopteris trees. We describe the overall habit for these surprisingly large aneurophytaleans, the earliest fossil group having wood produced by a bifacial vascular cambium. The site also provides evidence for arborescence within lycopsids, extending the North American range for trees in this ecologically critical group. The rooting horizon is a dark grey sandy mudstone showing limited root penetration. Although clearly belonging to a wetland coastal plain environment9, the forest was probably limited in duration and subject to periodic disturbance. These observations provide fundamental clarification of the palaeoecology of this mixed-group early forest, with important implications for interpreting coeval assemblage data worldwide