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Extent of Western Interior Seaway during Late Turonian. Rectangle defines the study area. Paleogeographic map modified from Roberts and Kirschbaum (1995).
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ABSTRACT: During the mid-Cretaceous (about 100 million years before present), one vegetational transition involved the rise to dominance of angiosperms (flowering plants). By this time, the adaptive radiation of angiosperms had already developed major lineages at the level of order and probably some families. As published by Lesquereux, the Dakota...
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... the mid-Cretaceous a vast seaway, the Western Interior Seaway (WIS), occupied the Western Interior of North America (Figure 2). In the United States, the seaway extended about 1,000 miles from central Utah to Minnesota when the sea level was at its highest position. ...
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... the United States, the seaway extended about 1,000 miles from central Utah to Minnesota when the sea level was at its highest position. The seaway existed within an asymmetric foreland basin that was bordered on the west by the Columbian-Sevier orogen and flanking foredeep and on the east by the stable cratonic platform (Figure 2) (Kauffman, 1984). ...
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... parlatorii Fontaine 1889 (Figure 17, 1-6; Figure 17, 10; Figure 18, 1-11; Figure 23, 1) Rogersia lottii Wang sp. nov. ...
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... Figure 26, Klucking, 1987), Litsea ferruginea Bl. (Klucking, 1987), Nectandra lanceolata Nees ( Klucking, 1987), and Neolitsea cambodiana Lec. var. ...
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... trilobus is trilobed and has secondary veins, which are more widely spaced and originate from primary veins at more obtuse angles. Yangia glandifolium has a strong primary vein, numerous and thinner secondary veins, finer teeth on margin and oil glands all over the lamina (Figure 29, 2). ...
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... Figure 23, 5 Description. Leaf length over 10 cm, width at least 4 cm; apex missing; base normal, obtuse; basal portion of petiole missing. ...
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... Figure 24, Discussion. This species differs from other Dakota Formation angiosperm species in having integrading intersecondary, tertiary, and quaternary veins; randomly reticulate venation; margins thinly reinforced. ...
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... Leaf compound, with three (Figure 63, 1; Figure 66, 1, 66, 7-8) or four leaflets ( Figure 67, 2); most commonly three leaflets closely arranged on the rachis on the distal portion, occasionally with one leaflet attached on rachis at a certain distance away proximally; leaflets of 2 or 4 closely arranged on distal portion of rachis also observed; rachis thin, at least 3 cm long by 1 mm wide. Whole leaflet lamina and base asymmetrical, lorate, L/W > 6:1, always curved abaxially (downward); apex attenuate; base normal acute; petiolule varies from lacking (lateral leaflets) to up to 1.5 cm long (medial leaflet); margin entire, usually revolute. ...
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... venation actinodromous; primary vein moderate in thickness; lateral primary veins diverging at a point about 1 cm from the petiole base. Secondary venation craspedodromous ( Figure 69, 2); secondary veins moderate in thickness, subopposite or alternate; typically 4 to 5 pairs; secondary vein spacing irregular and decreasing distally; between medial and lateral primary veins, there are two or three pairs of veins of tertiary order originating from the medial primary vein; secondary veins originating from primary vein at moderate acute angles (±45°), each extending to the apex of a lobe; sinuses rounded, depth varying from slightly wavy to ½ distance from margin to primary vein; on lobed margin, veins originating from adjacent secondary veins (tertiary veins) form a series of inverted 'V's below sinus and brochidodromous above sinus, these tertiary order loops may be enclosed by one, two or more series of loops formed by veins of higher orders; along the wavy margin, tertiary veins tending to be percurrent or form inverted 'V's but with irregular course and spacing (Figure 69, 2). Quaternary veins (Figure 69, 2) in the excostal region and below sinus between secondary veins predominately percurrent, course straight or curved. ...
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... venation actinodromous; primary vein moderate in thickness; lateral primary veins diverging at a point about 1 cm from the petiole base. Secondary venation craspedodromous ( Figure 69, 2); secondary veins moderate in thickness, subopposite or alternate; typically 4 to 5 pairs; secondary vein spacing irregular and decreasing distally; between medial and lateral primary veins, there are two or three pairs of veins of tertiary order originating from the medial primary vein; secondary veins originating from primary vein at moderate acute angles (±45°), each extending to the apex of a lobe; sinuses rounded, depth varying from slightly wavy to ½ distance from margin to primary vein; on lobed margin, veins originating from adjacent secondary veins (tertiary veins) form a series of inverted 'V's below sinus and brochidodromous above sinus, these tertiary order loops may be enclosed by one, two or more series of loops formed by veins of higher orders; along the wavy margin, tertiary veins tending to be percurrent or form inverted 'V's but with irregular course and spacing (Figure 69, 2). Quaternary veins (Figure 69, 2) in the excostal region and below sinus between secondary veins predominately percurrent, course straight or curved. ...
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... relationship of these two extinct genera with the modern family Platanaceae was indicated not only by characters of leaf architecture (Schwarzwalder and Dilcher, 1981;Schwarzwalder, 1986Schwarzwalder, , 1991 "Sassafras" (Araliopsis) cretaceum var. obtusum Lesquereux, 1874, The Cretaceous Flora, p.80, pl. 7, Figure 2; p.80, pl. 8, Figure 1. Description. ...
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... venation simple craspedodromous, with all of the secondaries and their branches terminating at the margin, giving rise to glandular projections; secondaries thick relative to primary vein; two prominent basal secondaries depart from primary vein at extreme base of lamina; secondaries arising from primary vein at moderate acute angles, opposite to subopposite, decurrent; secondaries Description. Leaf symmetrical; orbiculate or wide ovate to very wide ovate, L/W 1 to 1.1, lamina 6 to 12 cm long by 6 to 12 cm wide (estimated minimum and maximum length); apex rounded, emarginate or mucronate; base predominately cordate in overall shape but decurrent on the petiole, occasionally cuneate; margin entire, slightly wavy; petiole inflated ( Figure 55, 2 as indicated by arrow) at base, 1.1 to 4.5 cm long by 0.6 to 0.8 mm wide. Primary venation pinnate; primary vein weak (less than 1.25%), straight, multistranded. ...
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... Figure 52, 3) Specific diagnosis. Leaf narrow elliptic; apex acuminate, base decurrent; petiole region with decurrent wing of lamina tissue; distal 1/3 portion of leaf margin toothed, proximal portion entire; tooth typically straight-straight (B-2) or occasionally convex- straight (B-1), regularly spaced, sinus smooth. ...
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... interpretation of environments for the Dakota Formation localities varies, but predominantly lake or swamp (Table 1), e.g., Braun's Ranch, Kansas (Figure 72), fresh water lake on an alluvial floodplain (Retallack and Dilcher, 1981;Farley and Dilcher, 1986); Hoisington III, Kansas (Figure 73), fresh-water lake or brackish water lagoon environment with river influence (Retallack and Dilcher, 1981;Dilcher, 1992, 1994); Rose Creek I, Nebraska (Figure 74), a coastal swamp with periods of inundation with brackish water and tidal influences (Farley and Dilcher, 1986;Upchurch and Dilcher, 1990). Leaves of different sizes are exquisitely preserved without any orientation ( Figure 75) indicating no sorting mechanism was involved. ...
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... example, the percentage of species with entire-margined leaves tends to increase with increasing temperature, while leaf size tends to increase with increasing precipitation ( Bailey and Sinnott, 1915;Wolfe, 1979;Givnish, 1987;Wolfe, 1993;Wilf, 1997Wilf, , 1998Wilf and Wing, 1998;Wilf et al., 1999). Many angiosperm species from the Dakota Formation, i.e., Eoplatanus serrata (Figure 13, 1; Figure 13 (Figure 55, 2), have leaves that possess a distinctive swollen petiole base and/or with stipules (The original function of stipules is unknown, but may have been involved as protection for the emerging leaf buds). Leaves of many species possess very large leaf sizes. ...
Citations
... Their fossil record starts from the Early Cretaceous, and is widely distributed in Greenland, Europe, North America, and Asia [10,11,13,. The oldest record goes back to the Aptian [36], but the records become abundant since the Albian [9,17,22,23,[29][30][31][32][33]35,37]. The ubiquitous presence of the Platanaceae in the Early-Middle Cretaceous floras is in line with its basal position in Eudicots. ...
... The ubiquitous presence of the Platanaceae in the Early-Middle Cretaceous floras is in line with its basal position in Eudicots. Sometimes platanaceous leaves may constitute the dominant species in some megafloras of the Dakota Formation [35]. ...
... The enlarged petiole base is a feature shared among Arthollia dayangshuensis, P. fraxinifolia and P. neptuni [15], suggestive of the presence of intrapetiolar axillary bud in these taxa. This feature is a proxy of deciduous habit and seasonal climate [35]. Fossil leaves of nymphaealean affinity (in progress) associated with Arthollia dayangshuensis suggest that Arthollia dayangshuensis may be a tree living in a niche not far away from water body, which may be common in this region at that time, a landscape quite different from the current prairie. ...
Angiosperms and insects are two most diverse groups of macroscopic organisms, and their relationship plays an important role in the current ecosystem. An angiosperm is usually attacked by multiple insects in the current ecosystem, which is a proxy of the complication of the ecosystem. However, such a complicate relationship appears lacking in the ecosystem for early angiosperms, which are usually attacked by only one type of insects. Therefore, when the complicate angiosperm-related ecosystem emerged is an important unanswered question. Here we document a new platanaceous species, Arthollia dayangshuensis gen. et sp. nov from the Nenjiang Formation (late Santonian-early Campanian, Late Cretaceous) with three different kinds of damages, suggesting that the ecological relationship between angiosperms and insects was already complicate in the Santonian. This surprising discovery implies that angiosperm-related ecosystem has already existed in the Late Cretaceous. To this date, this is the first sign of such a complicating process.
... Flower specimens were collected during the 1970s and 1980s by D. Dilcher and colleagues and are stored at the Florida Museum of Natural History, in Gainesville, Florida. The localities are distributed along a younger to older north-northeast to south-southwest transect [11] (electronic supplementary material, figure S1). The localities were deposited along the eastern coast of the North American Mid Cretaceous Seaway that extended from the Gulf of Mexico to the Canadian Arctic [12,13]. ...
... Lithological facies within the Dakota Formation are dominated by shales and sandstones of the upper Janssen Clay Member and subjacent claystones of the lower Terra Cotta Clay Member [11,13]. Dakota depositional environments are represented by brackish estuaries, freshwater swamps, low energy channels, floodplain ponds and ox-bow lakes (electronic supplementary material, table S1). ...
... Dakota depositional environments are represented by brackish estuaries, freshwater swamps, low energy channels, floodplain ponds and ox-bow lakes (electronic supplementary material, table S1). These biotic environments consisted of humid forests and woodland [11,13]. The Rose Creek I locality, where most of the flowers were deposited, represented a mangal-like marsh similar to extant communities in southeast Asia [14]. ...
Florivory (flower consumption) occurs worldwide in modern angiosperms, associated with pollen and nectar consumption. However, florivory remains unrecorded from fossil flowers since their Early Cretaceous appearance. We test hypotheses that earliest angiosperms were pollinated by a diverse insect fauna by evaluating 7858 plants from eight localities of the latest Albian Dakota Formation from midcontinental North America, in which 645 specimens (8.2%) were flowers or inflorescences. Well-preserved specimens were categorized into 32 morphotypes, nine of which displayed 207 instances of damage from 11 insect damage types (DTs) by four functional-feeding groups of hole feeding, margin feeding, surface feeding and piercing-and-sucking. We assessed the same DTs inflicted by known florivores on modern flowers that also are their pollinators, and associated insect mouthpart types causing such damage. The diverse, Dakota florivore–pollinator community showed a local pattern at Braun's Ranch of flower morphotypes 4 and 5 having piercing-and-sucking as dominant and margin feeding as minor interactions, whereas Dakotanthus cordiformis at Rose Creek I and II had an opposite pattern. We found no evidence for nectar robbing. These data support the rapid emergence of early angiosperms of florivore and associated pollinator guilds expressed at both the local and regional community levels.
... The fossil Platanus has commonly been recorded in Upper Cretaceous sediments of the North-Hemisphere, particularly in the Cenomanian of North America and Far Eastern Russia (Fontaine, 1889;Ablaev, 1974;Guo, 1986;Herman, 2002;Wang, 2002;Wang and Dilcher, 2006). The first report of Platanus in the Cretaceous from the eastern Heilongjiang was published by Zhang (1981) in the Houshigou Formation from the Mudanjiang area (Fig. 1a), including Platanus subnobilis Zhang, P. pseudoguillelmae Krasser, and P. sp. ...
... was found in thick yellow sandstone intercalated with siltstones and conglomerate, and attributed to the uppermost Houshigou Formation (K 1-2h ), according to the BGMRHP (1993) and Jia (2016). The new Platanus fossils are comparable with Cenomanian Platanus recorded in the middle Dakota Formation of North America (Newberry, 1898;Wang, 2002;Wang and Dilcher, 2006), and the records of this form from Mudanjiang in China (Zhang, 1981(Zhang, , 1985. The Platanus-bearing yellow sandstones are conformably overlain by varicolored volcanic rocks belonging to the Songmuhe Formation (K 2s ; Hao et al., 2000), from which samples were collected for radiometric dating. ...
... Comparison: The characters of the new species are trilobate, entire with some undulation in the leaf margin, with sub-rounded sinuses in some marginal parts, and in this way this species is different from all known species reported in the Heilongjiang region of China (Zhang, 1981(Zhang, , 1985Sun et al., 2000Sun et al., , 2007Sun et al., , 2014. Comparing with the other known species, only a few taxa can be compared in terms of gross morphology to the present new species, e.g., Platanus latiloba Newberry (Newberry, 1898) and Pabiana groenlandica (Heer) Hongshan (Wang, 2002), both from the Cenomanian beds in the Dakota Formation in Nebraska, USA. However, the former American taxon has obtuse or abruptly acuminate lobes, and with some bigger teeth; the latter has palinactinodromous venations, and its secondary veins are opposite from the primary veins, festooned brochidodromous in type, all different characteristics to the new species described here. ...
The stratigraphic division and sequence of the Upper Cretaceous sediments in eastern Heilongjiang Province, China, have been ambiguous and controversial, mainly due to a lack of biostratigraphically useful fossils and related radiometric dating. A new species of angiospermous fossil plant, Platanus heilongjiangensis sp. nov., from Qitaihe in eastern Heilongjiang has been found in sediments conformably above which zircons from a rhyolitic tuff has been dated by U–Pb radiometric methods as 96.2 ± 1.7 Ma, indicating that the Upper Houshigou Formation is of Cenomanian age. This discovery not only provides new data to improve our stratigraphic understanding of the Houshigou Formation, but also shows that Platanus flourished in the early Late Cretaceous floras of the region. This new study also indicates active volcanism taking place in the eastern Heilongjiang region during the Cenomanian of the Late Cretaceous. © 2018 China University of Geosciences (Beijing) and Peking University
... None of Lesquereux's species occur in the Cenozoic (LaMotte 1952). Wang (2002) reviewed the angiosperm leaf record of the Dakota Formation, but offered few synonymies and updates of Lesquereux's material. The only Quercusrelated occurrence he discussed is that of the leaf type Quercophyllum tenuinerve Fontaine. ...
The evolution of plant ecosystems during the Cenophytic was complex and influenced by both abiotic and biotic factors. Among abiotic forces were tectonics, the distribution of continents and seas, climate, and fires; of biotic factors were herbivores, pests, and intra- and interspecific competition. The genus QuercusL. (Quercoideae, Fagaceae) evolved in this context to become an established member of the plant communities of the Northern Hemisphere, commencing in the Paleogene and spreading to a diverse range of environments in the later Cenozoic. Its palaeontological record, dominated by leaves and pollen, but also including wood, fruits and flowers, is widespread in Eurasia and North America. Consequently, a great number of species have been described, from the 19th century to the present day. Although Quercus is currently an ecologically and economically important component of the forests in many places of the Northern Hemisphere and Southeastern Asia, no comprehensive summary of its fossil record exists. The present work, written by an international team of palaeobotanists, provides the first synthesis of the fossil history of the oaks from their appearance in the early Paleogene to the Quaternary.
... The Potomac Group (Aptian-Cenomanian) of eastern North America preserves wood fragments, conifer cones and seeds, and angiosperm leaves and fruits (Crane et al., 1986;Doyle and Hickey, 1976;Fontaine, 1889;Hickey and Doyle, 1977;Hochuli et al., 2006;Jud and Hickey, 2013;Upchurch Jr. et al., 1994). The Dakota Formation (Cenomanian) of the Western Interior of North America preserves an abundant and diverse compression flora (Lesquereux, 1891(Lesquereux, [1892 ;Upchurch Jr. and Dilcher, 1990;Wang, 2002;Wang and Dilcher, 2006). In addition, smaller compression floras from the late Early Cretaceous and early Late Cretaceous have been reported from South Carolina (Lupia et al., 1999). ...
... Cenomanian-age sediments from the Dakota Formation of Nebraska and Kansas have also yielded floras with taxa in common with Soap Wash. For example, CM01 (Pandemophyllum inaequalis) is reported as one of the most abundant forms at a number of Dakota Formation localities (Upchurch Jr. and Dilcher, 1990;Wang, 2002;Wang and Dilcher, 2006). CM08 (Lesquereux, 1874(Lesquereux, , 1891(Lesquereux, [1892), legume-like leaves similar to CM09 (Lesquereux, 1891(Lesquereux, [1892), bilobed leaves with affinity to CM10 (Newberry, 1868), CM11 (Capellini and Heer, 1866) and CM14 (Wang and Dilcher, 2006) are reported from Dakota Formation localities. ...
Angiosperms first appeared in the fossil record as pollen during the Valanginian–Hauterivian; they spread out of the tropics in the Aptian and Albian, and radiated in the Late Cretaceous. Despite these general patterns, details of the taxonomic, geographic, and ecological evolution of Cretaceous angiosperms are relatively poorly known because only a handful of Early and mid-Cretaceous macrofloras have been reported. This is the first detailed report of a fossil leaf flora from the Cedar Mountain Formation from the mid-Cretaceous of the Western Interior. We describe a flora that is overwhelmingly dominated by angiosperms (152 of 153 identified specimens are angiosperms) from the Albian–Cenomanian transition that is preserved in a clay- and carbonate-rich, lacustrine mudstone from the uppermost Cedar Mountain Formation of Emery County, Utah. We recognize 18 leaf morphotypes, all of which are dicotyledonous angiosperms. The majority of the Cedar Mountain morphotypes have taxonomic affinities with forms of similar age described from the Atlantic and Gulf coastal plains and other localities from the Western Interior. From this, we infer that a relatively diverse angiosperm flora grew along the margins of a small pond on the coastal plain. Palynological preparations of the fossil matrix were barren; however, previous studies of other facies within the formation showed that both conifers and ferns were important components of the regional vegetation during Cedar Mountain time. The effective absence of conifers and ferns in this macroflora and low leaf mass per area values among the angiosperms measured suggests that even at the Early–Late Cretaceous transition, angiosperms had come to dominate some sites, particularly those that were disturbed or seasonally ephemeral, where fast-growth or seasonal deciduousness would have been favored.
... The variation of Late Cretaceous dicotyledonate leaf architecture poses a series of systematic, nomenclatural and descriptive problems, mainly due to the lack of Recent representatives of taxa producing such leaf material. Several papers approached this problem, beginning with Spicer (1986), followed by Upchurch and Dilcher (1990), Wang (2002), and Ellis et al., (2009). In this paper we used the simplest descriptions with the simplest terminology, in order to avoid misunderstandings in terms of description and interpretation of dicot architecture. ...
The Hateg and Rusca Montana basins (South Carpathians, Romania) yield a rich Late Cretaceous
(Maastrichtian) compressive megafloral assemblage represented by ferns, conifers, onocotyledons and dicotyledons. This paper focuses on the dicotyledons of these basins, based on recently collected material as well as on historical collections of the University of Bucharest, including the Dinca and Raileanu collections, and of the Babes¸ Bolyai University of Cluj-Napoca, with the Petrescu and Dusa collection. The dicotyledonate association is represented by Araliaephyllum sp., Credneria denticulata, Ettingshausenia onomasta, Ettingshausenia sp., and five other dicotyledon types, a taxonomically much less diverse assemblage than previously published. Differences with regard to the previous taxa lists of the Hateg and Rusca Montana basins are due to the reinterpretation of the fossil material in the light of recent advances in the field, especially when considering a higher variation of the leaf material, its preservation and its taphonomy.
... The genus Crassidenticulum Upchurch and Dilcher (1990) includes simple or compound leaves with predominately toothed margins from the Albian e Cenomanian of North America (Upchurch and Dilcher, 1990;Wang, 2002;Wang and Dilcher, 2006). Some of them have similarities to the leaves of Puesto Manuel Arce. ...
... Some of them have similarities to the leaves of Puesto Manuel Arce. This is the case of the most dissected trilobate specimens of Crassidenticulum trilobum Wang and Dilcher (2006), including a leaf from Hoisington III locality described by Wang (2002, figure 36.2), and two others specimens from the same locality mentioned by this author as "Crassidenticulum variloba" Wang (2002, figures 34.1 and 36.1). ...
... Some of them have similarities to the leaves of Puesto Manuel Arce. This is the case of the most dissected trilobate specimens of Crassidenticulum trilobum Wang and Dilcher (2006), including a leaf from Hoisington III locality described by Wang (2002, figure 36.2), and two others specimens from the same locality mentioned by this author as "Crassidenticulum variloba" Wang (2002, figures 34.1 and 36.1). ...
The first association of fossil plant impressions in the Chubut Group at the Somuncura-Cañadón Asfalto �
Basin is described herein. The mid-Cretaceous megafloral assemblage from Patagonia, Argentina was
recovered from the Puesto Manuel Arce Formation. The taphocenosis consists mostly of leaves preserved
as impressions, although a variety of cuticle remains are also present. Angiosperms are both quantitatively
and qualitatively the main component of the flora (at least 9 leaf morphotypes recognized). A few
ferns and conifers complete the plant assemblage. The angiosperm leaves exhibit physiognomic heterogeneity
with a variety of well-defined venation patterns. The myrtophyll morphotype (Myrtoidea sp.)
and palmatilobed palinactinodromous leaves (Bamfordphyllum crassivena gen. et sp. nov.) are significant
components of the assemblage. Flora characters are consistent with the Cenomanian e earliest Turonian
age proposed for the Puesto Manuel Arce Formation. Comparisons were made with coeval Patagonian
and extra-regional floras which suggest both local as well as long-distance Gondwanan links.
... The Dakota Formation leaves analysed in this study represent probable relatives of basal lineages and Chloranthales. Probable basal lineages include Longstrethia varidentata, which shows a mosaic of venational and cuticular features found in the families Trimeniaceae and Schisandraceae (Austrobaileyales), and the related Longstrethia aspera [19,40,41]. Possible relatives of Chloranthaceae include Crassidenticulum decurrens, Crassidenticulum landisae, Densinervum kaulii and Reynoldsiophyllum nebrascense [20,21]. ...
Despite more than a century of research, some key aspects of habitat preference and ecology of the earliest angiosperms remain poorly constrained. Proposed growth ecology has varied from opportunistic weedy species growing in full sun to slow-growing species limited to the shaded understorey of gymnos-perm forests. Evidence suggests that the earliest angiosperms possessed low transpiration rates: gas exchange rates for extant basal angiosperms are low, as are the reconstructed gas exchange rates for the oldest known angiosperm leaf fossils. Leaves with low transpirational capacity are vulnerable to overheating in full sun, favouring the hypothesis that early angiosperms were limited to the shaded understorey. Here, modelled leaf temperatures are used to examine the thermal tolerance of some of the earliest angiosperms. Our results indicate that small leaf size could have mitigated the low transpirational cooling capacity of many early angiosperms, enabling many species to survive in full sun. We propose that during the earliest phases of the angiosperm leaf record, angiosperms may not have been limited to the understorey, and that some species were able to compete with ferns and gymnosperms in both shaded and sunny habitats, especially in the absence of competition from more rapidly growing and transpiring advanced lineages of angiosperms.
... Initial analysis of the level of angiosperm species richness suggested that there were 437 distinct species (Lesquereux, 1891), which is an extremely high number and skews diversity curves for this time period (Lidgard and Crane, 1990). Subsequent researchers argued that the species were over-split in the earlier studies, because individual quarries typically preserve only 20 species, a common level for the middle Cretaceous (Wang, 2002;Wang and Dilcher, 2006b). ...
... The Dakota flora from the Eastern side of the Western Interior Seaway provides a good comparison, because it also appears to contain a high degree of compositional heterogeneity. Wang (2002) described 87 species from six localities in Kansas and Minnesota, and the overlap in species composition between sites was less than 25%. The 87 species described by Wang (2002) was far less than the 437 species described by Lesquereux (1891), potentially a function of over-splitting of species by Lesquereux (Lidgard and Crane, 1990). ...
... Wang (2002) described 87 species from six localities in Kansas and Minnesota, and the overlap in species composition between sites was less than 25%. The 87 species described by Wang (2002) was far less than the 437 species described by Lesquereux (1891), potentially a function of over-splitting of species by Lesquereux (Lidgard and Crane, 1990). However, if the true number of species in the Dakota Formation is closer to the number described by Lesquereux (1891) because he studied a greater number of localities, then a large degree of compositional heterogeneity existed on the eastern shoreline of the Western Interior Seaway. ...
... Paleosols were first recognized in the mid-Cretaceous Dakota Formation by soil scientists (Thorp and Reed, 1949;Reed, 1954), but also have attracted geological attention (Retallack and Dilcher, 1981a,b;Joeckel, 1987Joeckel, , 1991Porter et al., 1991). The Dakota Formation has long been known for its sandstone fossil floras, collected initially by George Miller Sternberg (Rogers, 1991) for Leo Lesquereux (1892), and more recently collected for shale floras with preserved cuticles (Dilcher et al., 1976;Dilcher, 1979;Basinger and Dilcher, 1984;Dilcher and Crane, 1984;Dilcher and Kovach, 1986;Dilcher, 1992, 1994;Wang, 2002;Wang and Dilcher, 2006;Dilcher and Wang, 2009;Wang et al., 2011). The Dakota Formation is also rich in fossil pollen (Farley and Dilcher, 1986;Kovach, 1988;Kovach and Dilcher, 1988;Witzke, 1994, 1995;Hu et al., 2008a,b), but poor in fossils other than plants. ...
... These different kinds of paleosols preserve floristically distinct fossil plant assemblages, and thus provide a guide to autochthonous plant communities. Some fossil plant localities (Hoisington, Courtland and Delphos: Wang, 2002;Wang and Dilcher, 2006;Wang et al., 2011) are laminated lake deposits in which plant remains from a variety of distinct communities have been mixed. Other localities include subautochthonous plant remains close to growth position, such as mangal vegetation dominated by Pabiania variloba and Pandemophyllum kvacekii in Makizi pedotype paleosols at Fairbury (Upchurch and Dilcher, 1990), and swamp woodland vegetation of Liriophyllum kansense and Sapindopsis bagleyae in underclay of the Cahli pedotype at Bunker Hill east (Retallack and Dilcher, 1981a,b). ...
... Large leaves, drip tips and vine like leaf shapes of the Fort Harker leaf assemblage have been interpreted as closed canopy multistratal rain forest (Upchurch and Wolfe, 1987), and these authors were prescient in noting that this sandstone flora (of Casmu pedotype at stratigraphic level of Sayela pedotype) may have been of short duration, anticipating discovery here of the basal Cenomanian warm-wet paleoclimatic spike (Fig. 9). Upper Dakota Formation floras are slightly less diverse (87 species, rather than 93 for the Fort Harker sandstone floras), and have variety of features of temperate deciduous woodlands: moderate size leaves with limited insect and fungal damage, and stipules or other protection for leaf buds (Wang, 2002). These floras were a marked advance in diversity and modernization of early angiosperms associated with extensive Early Cretaceous coastal migrations and paleoclimatic changes Dilcher, 1981a, 1986;Wang et al., 2009;Field et al., 2011;Friis et al., 2011). ...
Paleosols of the mid-Cretaceous (late Albian to early Cenomanian) Dakota Formation in Kansas and Nebraska are well exposed in road, river and clay pit exposures, but show systematic overprinting by modern weathering. Examination of deep drill cores reveals that modern weathering effects include (1) oxidation of pyrite to jarosite, (2) reaction of jarosite and calcite to clear selenite, and (3) oxidation of sphaerosiderite and siderite nodules to hematite. Surface oxidation in this region extends no deeper than 2 m from the surface. Hematite nodules and coatings of leaves are found in core only at one stratigraphic horizon, which was not as appears in outcrop, a laterite. Transformed matrix density and photoelectric absorption logs of cores reveal that kaolinite clays are most abundant within deeply weathered paleosols (Sayela pedotype) at this stratigraphic level, near the Albian–Cenomanian boundary, when angiosperm forests were especially diverse and lived in a subtropical humid climate. Other paleosols of the early Cenomanian were less deeply weathered, and fossil plants of this age included temperate humid angiosperm mangal and swamp woodland, but conifer-dominated floodplain forests. This short-lived mid-Cretaceous warm–wet spike has also been recognized in other paleosols of Minnesota, Utah, Nevada, and New Mexico, and coincides with marine black shale of the Breitstroffer event, midcontinental marine transgression, a sequence-stratigraphic boundary, and a marked increase in early angiosperm diversity.
