Williamsonia carolinensis sp. nov. and Associated Eoginkgoites Foliage from the Upper Triassic Pekin Formation, North Carolina: Implications for Early Evolution in the Williamsoniaceae (Bennettitales)

Abstract

Editor: Patrick S. Herendeen Premise of research. Few reproductive organs unequivocally attributable to the important but enigmatic Mesozoic seed plant order Bennettitales have been described from the Triassic of all of North America outside of Greenland. Here, the first ovulate reproductive organs (gynoecia) of the group from the Upper Triassic of eastern North America are described and assigned to a proposed new species, Williamsonia carolinensis, of the family Williamsoniaceae.Methodology. The excellently preserved plant fossils were investigated using cuticular analysis and light, fluorescence, and scanning electron microscopy.Pivotal results. The description is based on 10 specimens from the Late Triassic (Carnian) Pekin Formation of North Carolina. They are interpreted as representing progressive developmental stages. Williamsonia carolinensis lacks a corona (sterile apical projection of the receptacle) and bracts subtending the receptacle. The lack of bracts is particularly unusual and appears to be the original condition and not a preservation artifact based on their absence even on immature specimens. The two largest specimens, interpreted as mature gynoecia, occur together on the same slab in exclusive association with the unusual bennettitalean leaf Eoginkgoites, suggesting that these organs were produced by the same parent plant species.Conclusions. The unique features of W. carolinensis, along with the probable affinity with Eoginkgoites foliage, expands the known diversity of the Williamsoniaceae and supports previous suggestions of remarkably high levels of morphological disparity in the earliest history of the Bennettitales.

Westersheimia pramelreuthensis from the Carnian (Upper Triassic) of Lunz, Austria: More Evidence for a Unitegmic Seed Coat in Early Bennettitales

“…Almost no other Triassic (Carnian-Rhaetian) material resembles Westersheimia. Reports of well-preserved pre-Jurassic ovuliferous cones and other reproductive organs of bennettites are rare (e.g., Nathorst 1902;Harris 1932;Kräusel and Schaarschmidt 1966;Ash 1968;Pedersen et al 1989;Schweitzer and Kirchner 2003;Anderson et al 2007 the organization of the reproductive organs or whole plants (Krasser 1917(Krasser , 1919a(Krasser , 1919bHarris 1932;Kräusel 1948Kräusel , 1949Kräusel and Schaarschmidt 1966;Anderson and Anderson 2003;Schweitzer and Kirchner 2003;Pott et al 2010a;Pott 2014aPott , 2014bPott and Axsmith 2015). Several additional putative bennettitalean reproductive structures have been described from the Lunz flora (Krasser 1919a; Kräusel 1948Kräusel , 1949Kräusel and Schaarschmidt 1966;Pott et al 2010a, unpublished manuscript), but the structure and organization of some are not yet fully understood.…”

“…The Triassic record of bennettitalean reproductive structures primarily consists of isolated parts of reproductive organs and fragmentary compound organs, some of which are only poorly understood (e.g., Krasser 1917Krasser , 1919aKrasser , 1919bHarris 1932;Kräusel 1948Kräusel , 1949Kräusel and Schaarschmidt 1966;Ash 1968;Pedersen et al 1989;Anderson and Anderson 2003;Anderson et al 2007;Pott et al 2010a;Pott 2014a;Pott and Axsmith 2015). The Bennettitales from the Carnian of Lunz are among the oldest representatives of the group (Anderson et al 2007;Pott et al 2008aPott et al , 2010b and are therefore of particular interest in determining the architecture and functionality of early bennettitalean reproductive organs.…”

The diversity of Australian Mesozoic bennettitopsid reproductive organs

“…The AnisianLadinian age attributed to W. eskensis in our study makes this the oldest reproductive structure of Bennettitales yet discovered, and among the oldest fossils that can be confidently attributed to this order. Slightly younger bennettitaleans recognised by diagnostic cuticular characters, reproductive structures or wood anatomy are known from the Molteno Formation, South Africa (Carnian: Anderson 1989, 2003), the Chinle Formation of New Mexico (Carnian : Ash 1968), the Santa Clara Formation of Mexico (Carnian: Weber 2008), the Lunz Formation, Austria (Carnian: Pott et al 2007a, b), the De Geerdalen Formation, Svalbard (Carnian-Norian: Strullu-Derrien et al 2012;Pott 2014b), the Pekin Formation, eastern USA (Carnian: Pott and Axsmith 2015), and the Heiberg Formation, Arctic Canada, (Norian: Vavrek et al 2008). Wachtler and Van Konijnenburg-van Cittert (2000) reported a leaf of Pterophyllum filicoides from the Ladinian of the Dolomites (Italy), which can be assigned to Bennettitales with considerable confidence despite the lack of any epidermal anatomy.…”

“…Detached permineralized cones (usually assigned to Williamsoniaceae) are less common and were initially studied by Wieland (1909Wieland ( , 1911 with re-analysis by Delevoryas and Gould (1973). Watson and Sincock (1992) and Watson and Lydon (2004) studied and revised in detail the cycadeoidacean trunk genera with embedded cones from northwestern Europe, and later Rothwell and Stockey (2002) and Stockey and Rothwell (2003) studied isolated permineralized specimens of both families from North America and reevaluated characters for phylogenetic placement of the fossils (See Pott and Axsmith 2015). Permineralized material from India and Japan have also been studied over a long period, beginning with the works of Sahni (1932) and Sahni and Rao (1934), up to the detailed analyses of Bose (1966Bose ( , 1968, Sharma (1970Sharma ( , 1973Sharma ( , 1975Sharma ( , 1977, Bose et al (1984) and Saiki and Yoshida (1999).…”

New Ginkgophytes from the Upper Triassic–Lower Cretaceous of Spitsbergen and Edgeøya (Svalbard, Arctic Norway): The History of Ginkgoales on Svalbard

“…In contrast, Ginkgo sibirica Heer from the Heiberg Formation of Ellesmere Island in Arctic Canada is very similar to the Svalbard leaf in the shape of the leaf segments and overall outline, but the leaf is much broader, with a basal angle of more than 1807 (Ash and Basinger 1991;Ash 2010). The enigmatic taxon Eoginkgoites Bock, originally described as a ginkgophyte, was later identified as a bennettite (Ash 1976(Ash , 2010Axsmith et al 1995;Pott and Axsmith 2015).…”