Peter R. Crane

Societal Impact Statement: Food plants are vital to human and planetary health, but their diversity is threatened, making food security, nutrition, and environmental goals more difficult to achieve. Food plant diversity conservation, research, and education can be enhanced through collaboration between sectors, including genebanks and botanic gardens, which possess complementary strengths but have historically tended to work in isolation. We describe a vision for conserving and promoting food plant diversity through closer cross‐sectoral collaboration, offering examples of recent successes and announcing the launch of the Global Conservation Consortium for Food Plants. Summary: Food plant diversity is essential to food security and human nutrition and to productive, resilient, and sustainable food systems. Genebanks and botanic gardens hold large and varied collections of this diversity but have historically tended to work in isolation from each other on conservation, research, and education. We describe a vision for conserving and promoting food plant diversity by leveraging the complementary strengths of these sectors. To catalyze a more integrated global system for the conservation and sustainable use of food plant diversity, essential steps include better understanding and documenting the multiple dimensions of this diversity, conserving it, positioning it for broader use, and raising awareness about it, all of which require greater coordination around information, policies, and actions. We offer examples of recent efforts that have increased collaboration between these sectors and announce the launch of the Global Conservation Consortium for Food Plants.

The fossil seed, Decaturospermum macrocarpum (Lesquereux) gen. nov. et comb. nov., is described based on specimens of latest Albian to mid-Cenomanian age (mid-Cretaceous) from the Dakota Formation of Nebraska, and Kansas, USA, which were previously named Laurus macrocarpa Lesquereux; and from the Woodbine Formation of Texas, USA, which were previously named Laurocarpum tetragonale MacNeal. All specimens are molds and casts lacking cellular details, but light microscopy and micro-CT scanning reveal key structural features. Combined information from eight specimens indicates that D. macrocarpum is a seed with an outer covering comprised of four valves. The four valves are reflected in the cast of the seed cavity, which has a quadrangular transverse section with four rounded edges. Each valve has a smooth outer surface covering a decay-susceptible outer layer that was replaced by sediment early during fossilization. Sediment filling the space left by the decaysusceptible outer layer preserves an impression of a distinctive dendritic reticulate system of longitudinal and transverse ribs on its inner surface, which reflects the outer surface of a decay-resistant inner layer, now seen only as a cavity. The inner surface of the decay-resistant inner layer is smooth, as is the outer surface of the cast filling the seed cavity. Below the seed cavity a downward extension of the decay-resistant layer forms a prominent swollen-cylindrical flange around the seed base. Decay-susceptible tissues inside the swollen flange are replaced by sediment but preserve the distinctive sinuous course of four vascular bundles. The position of each bundle suggests that it entered a valve in a near median position. Comparison of Decaturospermum macrocarpum with other seeds of Cretaceous age indicates that the two-layered, four-valved outer covering is the envelope of a chlamydospermous seed, which was most likely produced by plants closely related to extant Gnetales.

Sphenophyllales is an extinct clade related to horsetails whose members were important ground-cover and understory components of the vast tropical Carboniferous peat swamps of Euramerica. These plants exhibited extreme anisophylly and heterophylly, complicating the development of whole-plant concepts within the group. Here, we describe a new species of a small sphenophyll cone—Hexaphyllostrobus negauneeana sp. nov.—using computed tomography of three remarkably well-preserved cones from the Pennsylvanian Mazon Creek flora of Illinois, USA. We also briefly review the broader diversity of sphenophylls present in the Mazon Creek flora as a step towards developing new whole-plant concepts within Sphenophyllales.

Premise: The archipelago of New Caledonia contains one of the world's most distinctive biotas. The presence of notable paleoendemics in this biota suggests that Gondwanan vicariance may have played an important role in its formation, but geological evidence indicates that New Caledonia was submerged until the Oligocene and that its flora formed from more recent long‐distance dispersal events. The lack of a fossil record contributes to uncertainties inherent in both interpretations, but newly discovered fossil plant assemblages may help clarify the origins of the New Caledonian flora.Methods: We used standard paleobotanical techniques to prepare and describe leafy conifer shoots from an early Miocene deposit (age ~19 Ma) on the Pindaï Peninsula of western New Caledonia. To determine affinities of the fossil material, we compared it to herbarium collections of extant New Caledonian conifers and the broader macrofossil record.Results: Fossil leaves contain cellular‐level details of leaf morphology and epidermis anatomy consistent with the conifer family Podocarpaceae, in particular the extant genus Dacrycarpus. However, stomata in the fossils are arranged in crowded complexes unlike those of any described Podocarpaceae taxon, and therefore we assign this material to a new extinct genus: Dacrycarpoides.Conclusions: New Caledonia is a hotspot of modern conifer biodiversity and was home to now extinct lineages as well. The presence of extinct conifers on Miocene New Caledonia is consistent with floras from neighboring landmasses and highlights the role of extinction in shaping the modern flora of New Caledonia and other Australasian landmasses.

Summary: Recent paleobotanical discoveries have renewed interest in the distinctively recurved, seed‐bearing cupules of Mesozoic plants, which are important for understanding seed plant phylogeny and the origin of the second integument of the angiosperm ovule. Reanalysis of the enigmatic seed‐bearing organ Dordrechtites elongatus from the Triassic of South Africa, the type species of the genus, combined with information from similar material from Antarctica, Argentina and Australia, indicates that Dordrechtites is a highly modified lateral branch of a seed cone. Short lateral projections from a primary cone axis each bear several Dordrechtites units. Each unit consists of a long stalk bearing a straight to sometimes recurved cupule with a long distal extension beyond the cupule apex. Each cupule is flattened in a plane perpendicular to the stalk and distal projection and contains up to two seeds. Structural similarities between Dordrechtites and the cupules of Doyleales indicate that they are homologous, providing new evidence for a close relationship. The persistent cupule stalk and apical extension of Dordrechtites, combined with the flattened cupule, suggests modification for wind and water dispersal.

Premise: The Aptian–Albian (121.4–100.5 Ma) was a greenhouse period with global temperatures estimated as 10–15°C warmer than pre‐industrial conditions, so it is surprising that the most reliable CO₂ estimates from this time are 2 during a warm period implies a very high Earth‐system sensitivity in the range of 6 to 9°C per CO₂ doubling between the Aptian‐Albian and today.Methods: We applied a well‐vetted paleo‐CO₂ proxy based on leaf gas‐exchange principles (Franks model) to two Pseudotorellia species from three stratigraphically similar samples at the Tevshiin Govi lignite mine in central Mongolia (~119.7–100.5 Ma).Results: Our median estimated CO₂ concentration from the three respective samples was 2132, 2405, and 2770 ppm. The primary reason for the high estimated CO₂ but with relatively large uncertainties is the very low stomatal density in both species, where small variations propagate to large changes in estimated CO₂. Indeed, we found that at least 15 leaves are required before the aggregate estimated CO₂ approaches that of the full data set.Conclusions: Our three CO₂ estimates all exceeded 2000 ppm, translating to an Earth‐system sensitivity (~3–5°C/CO₂ doubling) that is more in keeping with the current understanding of the long‐term climate system. Because of our large sample size, the directly measured inputs did not contribute much to the overall uncertainty in estimated CO₂; instead, the inferred inputs were responsible for most of the overall uncertainty and thus should be scrutinized for their value choices.

Premise: We studied the 3D morphology of a small, well‐preserved cone from the Pennsylvanian Mazon Creek Lagerstätte to characterize its structure and determine its systematic affinity. Previously tentatively assigned to the enigmatic Tetraphyllostrobus, we show that it differs in key respects from that genus as described.Methods: We systematically compared the new fossil with relevant Paleozoic cone genera and employed advanced imaging techniques, including scanning electron microscopy, Airyscan confocal super‐resolution microscopy, optical microscopy, and X‐ray microcomputed tomography to visualize and reconstruct the fossil cone in 3D.Results: The analyses demonstrate unequivocally that the sporophylls of the new Mazon Creek cone are arranged in whorls of six and have characters typical of Sphenophyllales, including epidermal cells with undulatory margins and in situ spores assignable to Columinisporites. The combination of characters, including sporophyll arrangement, anatomy, and spore type, supports the establishment of Hexaphyllostrobus kostorhysii gen. et sp. nov. within Sphenophyllales. Furthermore, we show that Tetraphyllostrobus, although originally described as possessing smooth monolete spores, actually possesses Columinisporites‐type spores, indicating that it, too, was most likely a sphenophyll.Conclusions: The recognition of Hexaphyllostrobus contributes to our knowledge of Pennsylvanian sphenophyll diversity, and in particular increases the number of species with in situ Columinisporites‐type spores. Attribution of Hexaphyllostrobus to Sphenophyllales calls into question current interpretations of Tetraphyllostrobus suggesting that future research on better‐preserved macrofossil material may demonstrate a sphenophyllalean relationship.

Premise: Fossil seeds recovered from the Early Cretaceous of Mongolia and Inner Mongolia, China, are described and assigned to Mongolitria gen. nov., a new genus of gymnosperm seed.Methods: Abundant lignitized seeds along with compression specimens isolated from the matrix were studied using a combination of scanning electron microscopy, anatomical sectioning, light microscopy, synchrotron radiation X‐ray microtomography, and cuticle preparations. A single permineralized seed was examined by light microscopy of cellulose acetate peels and X‐ray microtomography.Results: Two species are recognized, Mongolitria friisae sp. nov. and Mongolitria exesum sp. nov. Both seeds are orthotropous with a short apical micropyle and a small, basal, circular attachment scar. The thick sclerenchymatous integument has a consistently three‐parted organization and about 20 conspicuous longitudinal ribs on the surface. Mongolitria exesum differs from M. friisae primarily in its much larger size and thicker seed coat, which also preserves clear evidence of insect damage.Conclusions: Mongolitria is similar to other fossil seeds that have been assigned to Cycadales, but displays a unique combination of characters not found in any living or extinct cycadaceous plant, leaving its higher‐level systematic affinities uncertain. Germination apparently involved splitting of the integument into three valves. Mongolitria was prominent among the plant parts accumulating in peat swamps in eastern Asia during the Early Cretaceous.