Ovulate Cones of Schizolepidopsis ediae sp. nov. Provide Insights into the Evolution of Pinaceae

Abstract

Premise of research. The extinct conifer genus Schizolepidopsis is characterized by deeply bilobed ovuliferous scales bearing two adaxial seeds. Although it is frequently placed in Pinaceae, the evidence for a close relationship with the family is mixed. Resolving the affinities of Schizolepidopsis has important implications for the age of Pinaceae because putative reports of the genus extend into the Late Permian. We describe a new species, Schizolepidopsis ediae sp. nov., based on specimens from the Lower Cretaceous of Mongolia and Inner Mongolia, China, that represent the first anatomically preserved occurrences of Schizolepidopsis.Methodology. Specimens were studied using light microscopy, cellulose acetate peels, and X-ray micro-computed tomography. To test relationships between Schizolepidopsis and Pinaceae, we performed conifer-wide phylogenetic analyses that included 10 previously described fossil conifers using DNA sequence data and a new morphological matrix of ovulate reproductive characters. Analyses were performed using Bayesian total evidence and parsimony backbone approaches.Pivotal results. Schizolepidopsis ediae possesses key characters of Pinaceae, including those related to pollination biology. Most analyses placed S. ediae in crown group Pinaceae (abietoid clade), with all other Schizolepidopsis species forming a grade along the Pinaceae stem. Uncertainty in the data indicates that stem group affinities of S. ediae are also possible.Conclusions. Schizolepidopsis ediae provides the first conclusive evidence linking Schizolepidopsis with extant Pinaceae. The phylogenetic relationships between extant Pinaceae and Schizolepidopsis suggest that seed wings evolved along the Pinaceae stem and not with the crown group and that, in combination with developmental genetic evidence, the simple ovuliferous scales of Pinaceae likely evolved from bilobed ovuliferous scales like those of Schizolepidopsis. More broadly, this study provides evidence of a Mesozoic Pinaceae stem group that might extend into the Paleozoic, helping to reconcile the ancient stem divergence of Pinaceae with its relatively recent crown age.

A permineralized Early Cretaceous lycopsid from China and the evolution of crown clubmosses

“…These observations suggest that Lycopodicaulis was an upright plant of terrestrial habitats. It was preserved not as whole plants, but as fragments swept into an allochthonous peat along with other plant debris, including fragments of wood, roots, ferns, corystosperm cupules and cones and leaves of conifers (see Matsunaga et al ., 2021; G. Shi et al ., 2021).…”

New genus of Cupressaceae from the Upper Cretaceous of Patagonia (Argentina) fills a gap in the evolution of the ovuliferous complex in the family

“…8). A similar type of OCs is present in the Araucariaceae (Stockey, 1982; Farjon, 2010; Andruchow‐Colombo et al, 2018), Pinaceae (Farjon, 2005; Matsunaga et al, 2021), and some members of the Podocarpaceae (e.g., Saxegothaea ; Andruchow‐Colombo, 2021), but in these families, each OC bears a single (Araucariaceae and Podocarpaceae) or two (Pinaceae) seeds. We here defined the pseudopeltate OC morphology as more tridimensional than the foliate and tending to have a proportionally longer and thinner stalk, with seeds positioned in a distal widened portion of the complex that culminates with a generally lignified cap (Hollick & Jeffrey, 1906, 1909; Harris, 1953; Farjon, 2005; Mays & Cantrill, 2019; Figs.…”

Early Cretaceous abietoid Pinaceae from Mongolia and the history of seed scale shedding

“…Lepidocasus mellonae grew together with several other species of early Pinaceae in the Tevshiin Govi flora, including two species of Schizolepidopsis (Leslie et al, 2013; Matsunaga et al, 2021) as well as Picea farjonii and Pityostrobus stockeyae (Herrera et al, 2016). The disarticulating mature bract–scale complexes of L. mellonae differ from those of P. farjonii and P. stockeyae , which are spreading/flexing cones, in being prominently ribbed and tomentose instead of smooth and glabrous (Figure 6B, C).…”

“…Lepidocasus mellonae grew together with at least four other species of Pinaceae in the Tevshiin Govi swamp, making pinaceous conifers the most diverse component of the paleoflora (Leslie et al, 2013; Herrera et al, 2016; Matsunaga et al, 2021). The remarkable abundance of pinaceous fossils in the lignite also suggests that the local vegetation was dominated by this group of conifers.…”

“…206–188 mya) (Leslie et al, 2018; Ran et al, 2018), significantly before the earliest well‐documented fossil evidence of the family from the Late Jurassic (Rothwell et al, 2012). Nevertheless, fossils of probable stem group Pinaceae are known from the Triassic and Early Jurassic based on seed cones of Schizolepidopsis (see Zhang et al, 2011; Leslie et al, 2013; Domogatskaya and Herman, 2019; Matsunaga et al, 2021), and there are other putative pinaceous fossils of Jurassic age that have been assigned to several different genera: Pityolepis for cone scales, Pityospermum for winged seeds, Pityocladus for vegetative shoots, and Pityophyllum for detached leaves (Seward, 1919). Many of these isolated, early, potentially pinaceous fossils are based only on compressions/impressions, making it hard to evaluate their relationships.…”