Internal anatomy of the Late TriassicEquisetocaulisgen. nov., and the evolution of modern horsetails

Origin of Equisetum: Evolution of horsetails (Equisetales) within the major euphyllophyte clade Sphenopsida

“…190–140 Ma), these minimum ages for the Equisetum crown group are far older than the previously estimated mid‐Paleogene (i.e., Cenozoic) divergence calculation ( ~ 40 Ma; Des Marais et al., ). They are also far more consistent with age estimates suggested by studies that also consider the character configurations of extinct and extant members of the group (Stanich et al., ; Channing et al., ; Rothwell and Ash, ).…”

“…Fortunately, our understanding of Equisetum evolution has been enriched in the past years by the discovery of several fossils of successively more recent ages that display progressively larger numbers of putative crown group features (Stanich et al., ; Channing et al., ). The initial studies of those fossils suggested that the origin of the group may have been considerably older than previously calculated, perhaps as old as the mid‐Mesozoic (Stanich et al., ; Channing et al., ; Elgorriaga et al., ; Rothwell and Ash, ), interpretations that still need to be tested in a phylogenetic framework.…”

A new technique to prepare hard fruits and seeds for anatomical studies

“…The wafers are then cleaned, dried, and affixed to a traditional microscope slide using any standard mountant typically used to affix fossil wafers to slides (e.g., Manchester, 1994 [Elmer’s epoxy; Elmer’s Products Inc., Westerville, Ohio, USA]; Pigg et al, 2004 [UV-cured adhesive, UV-154; T.H.E. Company, Lakewood, Colorado, USA]; Rothwell and Ash, 2015 [Devcon 5 Minute Epoxy; ITW Devcon, Danvers, Massachusetts, USA]). The specimens are then photographed to document general morphology and three-dimensional features that could be lost when grinding specimens for transmitted microscopy.…”

“…These wafers are then mounted onto a microscope slide, ground and polished, and observed using reflected or transmitted light when the specimen is ground thin enough (<1 mm; Benedict et al, 2008 ). Results of this technique show fine anatomical details of a variety of fossil organs from various ages and sediments (e.g., Manchester, 1994 ; Hass and Rowe, 1999 ; Pigg et al, 2004 , 2008 , 2014 ; Rothwell and Ash, 2015 ).…”

“…Various research laboratories use differing mounting mediums to attach fossil wafers to glass slides (e.g., Manchester, 1994 [Elmer’s epoxy; Elmer’s Products Inc.]; Pigg et al, 2004 [a UV-cured adhesive, UV-154; T.H.E. Company, Lakewood, Colorado, USA]; Rothwell and Ash, 2015 [Devcon 5 Minute Epoxy; ITW Devcon, Danvers, Massachusetts, USA]). The author has not done an exhaustive search of adhesives, but two general notes would be to: (1) avoid any heat-cured medium that requires >60°C, due to the risk of damaging cells or cell contents, and (2) avoid a highly viscous two-part epoxy that may produce air bubbles when mixed (e.g., Loctite Epoxy Quick Set; Henkel, Düsseldorf, Germany).…”