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Leaves are the most abundant and visible plant organ, both in the modern world and the fossil record. Identifying foliage to the correct plant family based on leaf architecture is a fundamental botanical skill that is also critical for isolated fossil leaves, which often, especially in the Cenozoic, represent extinct genera and species from extant families. Resources focused on leaf identification are remarkably scarce; however, the situation has improved due to the recent proliferation of digitized herbarium material, live-plant identification applications, and online collections of cleared and fossil leaf images. Nevertheless, the need remains for a specialized image dataset for comparative leaf architecture. We address this gap by assembling an open-access database of 30,252 images of vouchered leaf specimens vetted to family level, primarily of angiosperms, including 26,176 images of cleared and x-rayed leaves representing 354 families and 4,076 of fossil leaves from 48 families. The images maintain original resolution, have user-friendly filenames, and are vetted using APG and modern paleobotanical standards. The cleared and x-rayed leaves include the Jack A. Wolfe and Leo J. Hickey contributions to the National Cleared Leaf Collection and a collection of high-resolution scanned x-ray negatives, housed in the Division of Paleobotany, Department of Paleobiology, Smithsonian National Museum of Natural History, Washington D.C.; and the Daniel I. Axelrod Cleared Leaf Collection, housed at the University of California Museum of Paleontology, Berkeley. The fossil images include a sampling of Late Cretaceous to Eocene paleobotanical sites from the Western Hemisphere held at numerous institutions, especially from Florissant Fossil Beds National Monument (late Eocene, Colorado), as well as several other localities from the Late Cretaceous to Eocene of the Western USA and the early Paleogene of Colombia and southern Argentina. The dataset facilitates new research and education opportunities in paleobotany, comparative leaf architecture, systematics, and machine learning.

Thirteen intact cynipine galls (Cynipidae) are identified from the significant late Pleistocene locality of Rancho La Brea, mostly within the range of approximately 30,000 to 48,000 14C yr BP. Late Cenozoic cynipids have a poor fossil record; it is thus of great interest that the provisional dates for this fossil gall collection establish that these insects and their hosts were an important part of the late Pleistocene ecosystem in and around Rancho La Brea. Cynipine host specificity both verifies, as well as augments, the proportionally low record of plants recovered at Rancho La Brea in comparison to records of mammals, birds, and other fauna. Because galler and hosts represent extant species, their climate and habitat restrictions offer a good basis for making paleoecological inferences. In particular, they imply that many of the diverse habitats found in California today, or, at least plant associations with similar environmental restrictions, some presently a distance from the Rancho La Brea Tar Pits, existed in the vicinity of this locality during the late Pleistocene. This material also includes previously undescribed species, several of which are morphologically similar to extant comparative material that exhibits a “jumping” behavior, previously believed to be unique to Neuroterus saltatorius Edwards.

Premise of research. Fossils of asymmetrically winged samaras, informally referred to as Acer negundoides MacGinitie (Sapindaceae), from the late Eocene–early Oligocene Badger’s Nose flora (∼34 Ma) of northern California, are described as Deviacer pidemarmanii Myers and Erwin sp. nov. The genus Deviacer Manchester is emended and attributed to the family Polygalaceae.Methodology. The morphological features of more than 40 samaras exquisitely preserved as compressions in lacustrine siltstone of the Badger’s Nose member of the Steamboat Formation were compared to similar extant and fossil-winged fruits.Pivotal results. Deviacer includes compressions of nonschizocarpic asymmetrical samaras with a small dorsal projection. Similar projections characterize the fruits of extant Securidaca (Polygalaceae) and the extinct genus Paleosecuridaca Pigg, Devore, and Wojciechowski, but Acer L. (Sapindaceae) fruits lack these structures. Morphologically, Deviacer is indistinguishable from the anatomically preserved fruits ...

High diversity and endemism in the California Floristic Province (CFP) are an alleged response to the late Cenozoic advent of Mediterranean-type climate in this region. Ceanothus comprises two divergent subgenera with centers of diversity in the CFP. We reconstruct the evolution of Ceanothus by using DNA sequence data from the nuclear gene nitrate reductase. We find that the timing of diversification events is related to geological and climatic history. In both subgenera, diversification is characterized by recent divergence of extant taxa and geographically structured phylogenetic relationships. A strong north-south divergence of subgenus Cerastes across the Transverse Ranges indicates that phylogenetic relationships may be structured by climatically divergent regions of the CFP. Divergence-time estimation suggests that the age of extant diversification in both subgenera is ∼6 Ma. This agrees with the fossil record but predates the hypothesized Quaternary (2-Ma) origin of Mediterranean-type climate in th...

Mid-19th century reports of “immense” coal outcrops in the Middle Fork Eel River (MFER) drainage near Round Valley in California's northern Coast Ranges fueled the early geological interest in this area, with mine development the primary focus of many studies. It was not until Samuel G. Clark's 1940 “Geology of the Covelo District, Mendocino County, California,” that the coal was placed in its regional geologic context and assigned to the Miocene, a determination that relied primarily on a Desmostylus hesperus molar found in shale overlying the coal and an associated equivocal, though Miocene-compatible, marine molluscan fauna. Our investigation of the MFER coal-bearing beds has provided new data from foraminifera, marine mollusks, fish remains, and the first reported fossil plants, which as a whole support Clark's Miocene age assignment. We also present an updated stratigraphy proposing under modern-day stratigraphic protocols that the informal name Sand Bank beds (SBb) be used in place of the Temblor Formation to refer to the SBb coal-bearing fluvial-marine unit. Analysis of the SBb stratigraphy and sedimentology reveals the presence of a fluvial system that flowed from a distal upland region southward toward the paleocoast of California. An abundant diverse palynoflora containing lycophytes, ferns, conifers, and mesic, thermophillic herbaceous and woody angiosperms indicates the drainage flowed through a coastal swampy forested bottomland and estuarine environment before emptying into a coastal basin. Presence of Taxodium -like wood, foliage, pollen, and other “hydrophiles” suggests the MFER coal was a local mire buried by the progradation of the SBb fluvial system during a regressive phase, an interpretation to be tested with future field work and detailed compositional analysis of the coal.

We reconstruct ancient temperature and elevation gradients across the early Eocene (52– 49 Ma) northern Sierra Nevada (California, United States) using organic molecular proxies that record atmospheric and ground-level effects of topography. Paleoelevation was determined by reconstructing the change in the hydrogen isotopic composition of precipitation (Δδ ΔδD precip ) and mean annual temperature (ΔT GDGT ) (glycerol dialkyl glycerol tetraethers) from the isotopic composition of fossil angiosperm leaf n-alkanes and the distribution of microbially produced soil tetraethers preserved in leaf-bearing sediments. Organic molecular data produce equivalent range-scale (δD n-alkane ) and channel (T GDGT ) paleoelevation estimates that show the northern Sierra Nevada was a warm (>6–8 °C warmer than modern), high-elevation (>2 km), and moderate- to low-relief landscape at the Eocene Climatic Optimum. Modern northern Sierra Nevada topography likely refl ects post-Paleocene reduction of mean surface elevation and late Cenozoic increases in relief.

Two leaves of Quercus simulata Knowlton from the Miocene of Oregon each show a new type of cynipid gall. Antronoides cyanomontanus n. sp. is described from six elongate and narrowly spindle-shaped galls, 7.0 mm long, and 2.0 mm wide tapering to a narrow tip. They have expanded rim-like bases with most galls scattered throughout the midsection adjacent to or partially straddling a secondary vein. Antronoides oregonensis n. sp. is known from 20 galls, 4.0–5.0 mm long, 1.8–2.0 mm wide and weakly clavate, appearing C-shaped with a rounded apex and circular to oval-shaped base. Galls occur primarily in the basal third of the leaf in a single file along each side of the midrib. Contrary to previous studies, we found A. schorni Waggoner and Poteet, A. polygonalis Waggoner, and A. cyanomontanus to be morphologically closer to Cynips cornifex Hartig on Q. pubescens (European white oak), whereas the new gall A. oregonensis most closely resembles X. clavuloides. The presence of Antronoides indicates the evo...

The Thunder Mountain paleoflora from the middle Eocene (46–45 Ma) of central Idaho represents an upland flora dominated by conifers. However, because many of the conifer species recognized at Thunder Mountain include a mixture of detached organs from different localities of different ages it is unclear which conifer taxa are present in or absent from the flora. Reexamination of the megaflora suggests Pseudotsuga and Cephalotaxus are equivocal, Thujopsis is not present, and the holotype ovulate cone of Larix leonardii does not show definitive features to justify its placement in Larix . The species Chamaecyparis edwardsii , Picea deweyensis and Abies deweyensis are based on fragmentary organs identifiable only to genus. Pinus baileyi is not closely related to P. longaeva (subgenus Strobus, subsection Balfourianae ) but is an excentromucronate hard pine with affinities to members of subgenus Pinus, cf. subsection Pinus . Revision of the Thunder Mountain conifer megafossil assemblage is a step toward clarifying the species present in the flora to provide further understanding of the diversity, evolutionary relationships and phytogeographic history of conifers during the Tertiary.

The Rancho La Brea Tar Pits is the world's richest and most important Late Pleistocene fossil locality and best renowned for numerous fossil mammals and birds excavated over the past century. Less researched are insects, even though these specimens frequently serve as the most valuable paleoenvironemental indicators due to their narrow climate restrictions and life cycles. Our goal was to examine fossil material that included insect-plant associations, and thus an even higher potential for significant paleoenviromental data. Micro-CT scans of two exceptionally preserved leafcutter bee nest cells from the Rancho La Brea Tar Pits in Los Angeles, California reveal intact pupae dated between ∼23,000-40,000 radiocarbon years BP. Here identified as best matched to Megachile (Litomegachile) gentilis Cresson (Hymenoptera: Megachilidae) based on environmental niche models as well as morphometrics, the nest cells (LACMRLP 388E) document rare preservation and life-stage. The result of complex plant-insect interactions, they offer new insights into the environment of the Late Pleistocene in southern California. The remarkable preservation of the nest cells suggests they were assembled and nested in the ground where they were excavated. The four different types of dicotyledonous leaves used to construct the cells were likely collected in close proximity to the nest and infer a wooded or riparian habitat with sufficient pollen sources for larval provisions. LACMRLP 388E is the first record of fossil Megachile Latreille cells with pupae. Consequently, it provides a pre-modern age location for a Nearctic group, whose phylogenetic relationships and biogeographic history remain poorly understood. Megachile gentilis appears to respond to climate change as it has expanded its distribution across elevation gradients over time as estimated by habitat suitability comparisons between low and high elevations; it currently inhabits mesic habitats which occurred at a lower elevation during the Last Glacial Maximum ∼21,000 years ago. Nevertheless, the broad ecological niche of M. gentilis appears to have remained stable.

A new type of pteridosperm ovulate fructification has been recovered from Carboniferous sediments on the Paracas peninsula of Peru, South America. Co-occurring in a monospecific assemblage with the ovulate fructification are fragments of microsporangiate branch systems that display a progymnosperm-like grade of organization. The ovulate branch system together with hundreds of dispersed seeds are described and named Oclloa cesariana gen. et sp. nov/ Oclloa ovules are acupulate, up to 11.0 mm long, 4.0 mm wide, and borne singly on the slender forked ultimate branchlets of primary laterals that are alternately arranged along a central axis. The integumentary lobes are fused laterally and to the nucellus in the basal one-half to two-thirds of the seed. At levels just below the pollen chamber, the integument separates distally into a whorl of 5–9 free, tentacle-like lobes. Minute projections line the margins and possibly inner surfaces of the free apical lobes. Internally, megasporangia display a pollen chamber, short lagenostome, and remnants of the central column; all features indicative of hydrasperman reproduction. Morphologically, Oclloa closely resembles the genus Physostoma, but our observations of the acupulate nature and other structural features distinguish it from this taxon. Oclloa is the first well documented acupulate lagenostomalean seed found outside of tropical Euramerica. Moreover, it provides the first positive evidence that not all ovules modified for hydrasperman reproduction were produced by cupulate branch systems. Found exclusively associated with Oclloa are microsporangiate branch systems that bear groups of 2–4 unfused, banana-shaped sporangia that are similar to Zimmermannitheca. However, based on differences in shape and number of sporangia per cluster, cluster symmetry, and branch system morphology, the specimens are assigned to the new taxon Obandotheca laminensis gen. et sp. nov.

Reinvestigation of the holotype and paratypes, as well as four new flowers of Paleorosa similkameenensis Basinger, have provided additional morphological and anatomical features to further characterize this early rosaceous flower. Noted features include the presence of a follicular fruit composed, at least in part, of thick-walled cells, seeds with possible remnants of embryonic tissue and hypostase, and pollen morphology and ultrastructure. The fruit is a follicle enclosed by a non-fleshy floral cup. Based on this fruit type Paleorosa is assigned to the Spiraeoideae. Although fruit morphology strongly supports inclusion of Paleorosa in Spiraeoideae, floral structure such as short, post-chalazal branching of the raphe and pollen morphology show similarities to Maloideae, particularly the genus Pyracantha Roemer. Paleorosa pollen is prolate and tricolporate with indistinct pores. The exine is striate, semi-tectate/columellate, and the sexine is thicker than the nexine. The intermediate characters of Paleorosa add strength to the hypothesis that Spiraeoideae may be ancestral to Maloideae. In addition, these intermediate characters provide further evidence for an important radiation of Rosaceae during the Eocene. This fossil material provides the opportunity to understand the pollen structure of the Rosaceae from the Eocene.

The Middle Eocene Princeton chert flora contains the most diverse collection of silicified monocotyledons recovered from the early Tertiary of western North America. Palm vegetative organs are the most common elements and are represented by five stems up to 9 cm wide with attached petiole bases and roots, plus numerous additional isolated petioles, midribs and laminae. Comparisons with extant palms reveal that fossil stem and leaf anatomy is most similar to two coryphoid genera, Rhapidophyllum and Brahea . However, the fossils differ from these genera in several characters and probably represent a new coryphoid taxon. Two small herbaceous monocot stems, one with attached roots, the other with attached roots and remnants of sheathing leaves, each show a pith surrounded by a vascular cylinder composed of several cycles of bundles. The two stems differ in bundle morphology, vessel characters and root anatomy, thus allowing their recognition as distinct types. In addition, a small petiole, Heleophyton helobieoides Erwin and Stockey, shows aerenchymatous ground tissue with numerous minute bundles arranged in five series, a pattern similar to petioles of the extant genus Echinodorus (Alismataceae), but differs in possessing bundle structure like that found in Butomus (Butomaceae). Vascular bundles display a protoxylem lacuna surrounded by a ring of cells with thickened inner tangential walls, 1–3 thin-walled metaxylem elements and a relatively large problem strand. Presence of these structural features suggests Heleophyton grew either submerged or was emergent. Heleophyton also provides further support for the interpretation that the Princeton chert locality represents an ancient lacustrine ecosystem, a site ideal for the study of early Tertiary monocotyledons.

Small permineralized monocotyledonous rhizomes and aerial stems from the Middle Eocene Princeton chert in British Columbia are described and named Soleredera rhizomorpha gen. et sp. nov. Rhizomes are up to 1.3 cm wide, have a narrow cortex without vascular bundles, and show a central cylinder composed of three or more irregular cycles of primary vascular bundles embedded in compact thick-walled ground tissue. The central cylinder surrounds a hollow or sometimes solid pith and is separated from the cortex by an endodermoid layer. Rhizome vascular bundles are collateral or amphivasal and lack a fibrous bundle sheath. Metaxylem consists of angular tracheids 9-42 μm wide with scalariform, transitional, opposite, or mostly alternate intervascular pitting. Pit apertures are lined with vesture-like projections. Attached to the rhizomes are lateral branches 2-3 mm wide and roots 0.5-1.5 mm wide. Aerial stems differ from the rhizomes in having two to three cycles of collateral bundles, tracheids with mostly scalar...

Seventeen small, staminate flowers, 3.0–4.5 mm long × 1.0–1.5 mm wide, representing two developmental stages of the same type of flower have been recovered from the Middle Eocene Princeton chert locality of British Columbia. Some specimens are immature buds with overlapping perianth parts enclosing the stamens; others represent mature flowers with an open perianth. Flowers are pedicellate with a small flat receptacle bearing a perianth of at least three sepals and up to four petals. Five specimens show a three- to four-lobed rudimentary pistil surrounded by an intrastaminal nectary disk. The 10 stamens are included or barely exserted with nonconnate filaments, 1.2–2.0 mm long, attached by a slender connective to large dithecal anthers up to about 0.9 mm long that open by longitudinal slits. The anther wall is represented by a palisadelike endothecium composed of cells that are thick-walled and radially elongated relative to the long axis of the anther. Abundant in situ pollen is semitectate–columellate, tricolporate, subprolate to prolate, and prominently striated with equatorially bridged colpi. This fossil combines flower and pollen characteristics similar to those of the Sapindaceae, resembling most closely the tribe Dodonaeeae. Key words: Sapindales, Dodonaeeae, Tertiary, permineralization, flowers, pollen.

Oryctoantiquus borealis Ratcliffe and Smith is described as a new genus and new species of fossil dynastine Scarabaeidae from West Branch Creek of the Middle Eocene Clarno Formation (44.6–46.8 Ma) of north-central Oregon, U.S.A. This specimen is the oldest specimen attributable to the subfamily Dynastinae and the largest fossil in the family Scarabaeidae.

Lyonothamnus Gray is a monotypic genus of evergreen trees endemic to California's Channel Islands. There is one species, L. floribundus, with two subspecies, ssp. floribundus and ssp. asplenifolius. Subspecies floribundus has simple and entire-margined leaves, while leaves of ssp. asplenifolius are pinnate and composed of three to seven primary segments. Despite its restricted modern occurrence, three fossil species have been described from Neogene paleofloras in the far western United States. Lyonothamnus mohavensis Axelrod is known from California; L. parvifolius (Axelrod) Wolfe and L. cedrusensis Axelrod, from Nevada. However, the size ranges used to segregate these species were all found to fall within the range of L. parvifolius from Stewart Valley, Nevada. Study of intact leaves reveals that the combination of (1) number of primary segments, (2) length of primary segments, (3) number of medial secondary segments per primary segment, and (4) lengths and widths of medial secondary segments is important in segregating species. Using these characters, L. parvifolius and L. wolfei Erwin et Schorn sp. nov. are recognized from Nevada and Oregon, and two species, L. mohavensis and L. axelrodii Erwin et Schorn sp. nov., from California. This renewed taxonomy within an updated temporal framework provides an important first step toward understanding the evolution, diversity, paleoecology, and paleobiogeographic history of this unusual member of the Rosaceae.

One small monocotyledon petiole, 1.8 × 1.5 mm wide, has been recovered from the Princeton chert in the Middle Eocene Allenby Formation, British Columbia. The petiole, rectangular in transverse outline, shows approximately 36 circular to oval-shaped vascular bundles within aerenchymatous ground tissue that includes tannin cells. The epidermis is underlain by a discontinuous hypodermis of thick-walled, pitted cells. Vascular bundles are in five series: (I) a median U-shaped arc of 11 – 13 bundles; (II) an abaxial arc of 6 bundles located below the main arc; (III) two short abaxial arcs of 3 bundles each; (IV) 2 bundles just below the abaxial surface; and (V) an adaxial series of 7 bundles that show an inverse orientation to those bundles in series I–IV. Larger bundles are collateral, with a protoxylem lacuna encircled by a ring of 9 – 14 thin-walled parenchyma cells, a relatively well-developed phloem strand, and one to three thin-walled metaxylem elements. Based on bundle arrangement, orientation, and morphology, the fossil petiole most closely resembles those of the Butomaceae and Alismataceae. This new species, Heleophyton helobiaeoides Erwin and Stockey gen. et sp.nov., in the Princeton chert flora, documents the presence of the Alismataceae in the Middle Eocene of western North America and provides further evidence that the locality represents an ancient aquatic ecosystem.

Gymnosperm-like stem and frond fragments have been discovered in the same Devonian deposits of West Virginia that yield the most ancient seeds. The vegetative organs exhibit the stem/leaf differentiation and frond structure that are characteristic of seed ferns, but they have a stelar configuration and a protoxylem architecture that are most similar to aneurophytalean progymnosperms. This combination of features supports the hypothesis that aneurophytalean progymnosperms are ancestral to gymnosperms.