Taxonomic revision of the J . Vicente collection dicotyledon leaves from the lower Maastrichtian of Isona ( northeastern Iberia )

The lower Maastrichtian plant megafossil site of Isona (Lleida, Catalonia, NE Spain) was discovered in 1979 and its first detailed study was published by Joan Vicente i Castells in 2002. The collection, of around 400 fossils, kept in the Museu de Geologia – Museu de Ciències Naturals de Barcelona (MGB-MCNB). In a recent study, the Vicente collection was partially revised resulting in 15 different morphotypes of dicot leaves of which only three could be assigned to the angiosperm families Lauraceae, Betulaceae and Celastraceae. In the present study, morphotypes are compared with cleared leaves of extant angiosperms and taxonomical hypotheses are proposed for most of them. Among the 17 morphotypes of dicotyledons currently distinguished in the fossil plant collection of Isona, likely members of Laurales, Proteales, Eurosids and Asterids have been identified. In addition, three new species of dicot leaves are described suggesting that the fossil flora from Isona could be more singular than previously thought.


INTRODUCTION
In the spring of 1979, the amateur geologist Enric Sunyer discovered a plant megafossil site at the edge of an unpaved trail being opened south of the Isona village (Lleida province, Catalonia, NE Spain).The discoverer communicated the finding to Mr. Joan Vicente i Castells and colleagues from the Institut d'Estudis de la Natura del Barcelonès Nord (Santa Coloma de Gramenet, Catalonia).During the following years, the team collected numerous plant megafossils in this site (the so called Isona-sud) and in up to five other outcrops (Isona-nord-est, Isona-est, Isona-Comiols, Isona-oest and Isona-sud-oest) near the village (Vicente, 2002).The Isona-sud site was firstly announced to science in the IV ème Conférence de l'Organisation Internationale de Paléobotanique held in Paris, by Barrón & Diéguez (1992).These authors identified members of Taxodiaceae (now included within Cupressaceae), Lauraceae, Hamamelideae and Arecaceae among the specimens previously collected by Joan Vicente and colleagues.In addition, they suggested that the plant fossils from Isona were latest Cretaceous or earliest Paleocene in age.
Twenty years after the discovery, Joan Vicente published (Fig. 1) a monograph describing the plant megafossils from the Isona sites (Vicente, 2002).He assigned a late Maastrichtian age to the sites and across the 450 specimens, identified a total of 132 species belonging to fungi, algae and vascular plants.Dicot leaves were the most abundant and were attributed to 66 species, nine of which were described for the first time.Vicente compared the specimens from Isona with plant fossil remains quoted from the Upper Cretaceous-Paleogene of Europe (Heer, 1855(Heer, -1859;;Velenovský, 1882Velenovský, -1887;;Krasser, 1896) and North America (Bullock, 1916;Berry, 1916Berry, , 1925Berry, , 1930;;Knowlton, 1922;Hollick, 1930;Bell, 1957Bell, , 1963;;Brown, 1962).However, as noticed by Marmi et al. (2014), diagnoses and descriptions provided by Vicente (2002) were mostly incomplete or ambiguous and many of his taxonomic assignments appeared to be incorrect.When Vicente performed his work, the potential application of leaf architecture to palaeobotany and plant systematics was not yet fully developed (Ellis et al., 2009).Moreover, angiosperm phylogeny was not updated making difficult to understand the phylogenetic significance of leaf characters.Like palaeobotanists of the nineteenth and twentieth centuries, he based his classification on similarities on gross morphology (leaf shape, primary and secondary vein courses or marginal outline) and related most of fossil specimens to extant genera.Vicente was unable to access the modern techniques of morphotyping and ignored the possibility of convergence in leaf structures among unrelated lineages (Doyle, 2007;Little et al., 2007).
The Isona-sud site was excavated again in the summer 2010 and 116 plant fossils as well as pollen samples were collected.This campaign provided relevant data for sedimentology and taphonomy, indicating that the plant fossil assemblage of Isona-sud was parautochthonous and allochthonous and deposited in a distal floodplain (Villalba-Breva et al., 2015).Pollen samples were collected from the different plant beds within one meter thick series and showed a relative abundance of fern spores.Plant remains likely came from different source plant communities growing in fluvial settings.Taphonomical data suggested that some riparian communities could be composed of alderlike trees (Dicot type 7 in Marmi et al., 2014; Eudicot form 2 in Villalba-Breva et al., 2015) with a diversity of ferns growing in the understory.The age of the site was restricted to Early Maastrichtian based on chrono-and biostratigraphic data (Villalba-Breva et al., 2015 and references therein).
Extant angiosperms are mostly identified and classified based on comparative analysis of reproductive characters.However, reproductive structures, such as flowers, are usually scarce in the plant fossil assemblages, which in many cases are exclusively composed of leaf fossils.Frequently, leaf fossils are the only source of data to know the diversity of angiosperms in the past.As mentioned above, structures in angiosperm leaves may be highly homoplasic.However, phylogenetic evidence can be detect ed if leaf architecture is accurately analysed, especially in angiosperms with net-venation (Ellis et al., 2009 and references therein).One of the first attempts to elucidate phylogenetic signatures from the leaf characters of dicots were carried out by Hickey & Wolfe (1975).These authors listed a number of architectural features of great importance in assessing systematic affinities at the higher taxonomic levels: 1) Simple vs compound organisation, 2) entire vs toothed margins, 3) features of teeth, 4) major vein configuration and 5) features of intercostal venation.Recent research has confirmed or refined many of the patterns noted by these authors (Doyle, 2007;Wilf, 2008 and references therein).Hickey & Wolfe based their conclusions on the classification systems of Takhtajan (1966Takhtajan ( , 1969) ) and Cronquist (1968), which are now outdated.In fact, many of the patterns recognised by Hickey & Wolfe (1975) are even more consistent with modern molecular phylogenies than they were in the Takhtajan-Cronquist systems (Doyle, 2007).Besides generic or higher taxonomic levels, leaf characters may also be diagnostic among closely related taxa (e.g.Sajo & Rudall, 2002;Espinosa et al., 2006;Doyle, 2007).Thus, it is well demonstrated that leaf architecture has a great potential to explore the taxonomic relationships of extinct flowering plants from which only the leaves are known.
Frequently, current palaeobotanists classify fossil leaves in morphotypes instead of assigning them to extant taxa.Leaf morphotypes derive from vouchered specimens and are subject to review by later researchers (Wilf, 2008).Although leaf morphotypes are not necessarily named entities, they comprise a parataxonomy for fossil floras and play a major role in many studies of regional biodiversity through time (e.g.extinction, recovery or response to climate change) (Wilf, 2008 and references therein).Morphotypes derived from specimens of the Vicente collection were coded as dicot types 1 to 15 by Marmi et al. (2014).In the same locality, morphotypes from newly collected specimens in the 2010 campaign were coded as eudicot forms 1 to 6 by Villalba-Breva et al. (2015).These coding systems may become tedious and difficult to interpret if they are repeatedly used.In the present study, dicot leaf morphotypes from the lower Maastrichtian of the Isona-sud site (Isona i Conca Dellà municipality, Lleida province, Catalonia, NE Spain) are compared with cleared leaves of extant angiosperms.This allows proposing hypotheses on the botanical affinities of morphotypes and suggests a binomial parataxonomy when possible.

GEOLOGICAL SETTING
All the specimens studied here come from the Isonasud site.It is located in the Pont del Molí trail, which crosses road C-1412 just south of Isona (Lleida province, Catalonia) village.Plant bearing beds were found within one meter thick section dominated by dark grey lutites interbedded with thin, laminated silstone layers (Villalba-Breva et al., 2015).It belongs to the Xullí unit, which corresponds to the uppermost portion of the Grey unit of the Tremp Formation (Mey et al., 1968;Rosell et al., 2001;Villalba-Breva et al., 2015).The studied section was interpreted by these latter authors as deposition of overbank, suspension-load sediments in fluvio-deltaic floodplains.For further details, readers may look up to Vicente (2002), Marmi et al. (2014) and Villalba-Breva et al. (2015).

MATERIAL AND METHODS
The Vicente collection is currently housed at the Museu de Geologia -Museu de Ciències Naturals de Barcelona under the acronym MGB.One hundred eleven specimens from the Vicente collection were previously examined by Marmi et al. (2014) following the methods of Ellis et al. (2009), resulting in a total of 15 morphotypes.In the present paper, leaf features of these morphotypes are des cribed with more detail and compared with cleared leaves of the National Cleared Leaf Collection-Wolfe (NCLC-W; http://clearedleavesdb.org/) (Das et al., 2014).This database contains up to 18,126 cleared leaf images representing most of extant angiosperm families.In a first screening, pictures of the cleared leaf specimens most resembling a given morphotype from Isona were selected based on general shape, major venation and margin features.In the next step, fossil specimens belonging to each morphotype were compared in detail with selected cleared leaf images taking into account features related to secondary veins (spacing, angle), tertiary to quinternary vein framework, terminal veins and tooth shape and density when applicable.The inclusion of leaf morphotypes from Isona to suprageneric taxonomic categories (i.e.orders, families) or clades depended on the phylogenetic position of extant species whose cleared leaves were the most similar to such morphotypes.Finally, those morphotypes including the best preserved material were assigned to form-genera and species based on compari sons with leaf fossils from the Upper Cretaceous of Europe and North America.
Description.Leaves are simple, petiolate and microphyllous.The petiole-lamina attachment is marginal (Fig. 2F).Laminae are incomplete, lanceolate to linear, symmetrical and entire-margined (Fig. 2).They are 20.0-119.8mm long and 12.7-24.8mm wide.Based on the most complete blades (e.g.Fig. 2F), the length/width ratio ranges from 7 to 8. Lamina bases are symmetrical, acute and cuneate (Fig. 2C-D, F; Fig. 3A, C-D, F).Apices are narrow, acute and straight (Fig. 2A, E-F; Fig. 3A, E-F).There are three basal veins (Fig. 2C-D; Fig. 3A-D, F).The midvein is straight and two to three times wider than the basal secondary veins.The latter arise from or near the base at very acute angles (11º-13º) and run parallel to the midvein at least up to the middle of the lamina.They may be eucamptodromous or attach to the following secondary vein.Distal secondary veins are brochidodromous and excurrently attached to the midvein (Fig. 2E; Fig. 3E).The secondary vein spacing abruptly increases towards the base.Tertiary veins are not preserved except for MGB 38220 that shows a few, blurred percurrent tertiaries.
The new species from Isona is very similar in shape and venation to Caryodaphnopsis tonkinensis (Lecomte) Airy Shaw and Sparattanthelium macusiorum Smith, which are members of Lauraceae and Hernandiaceae, respectively, within Laurales (Fig. 7A-B).However, these species have three basal primary veins and exmedial thinner primary veins are completely replaced by brochidodromous secondary veins.The venation of specimen MGB 38256 strongly resembles Bixa excelsa Gleason & Krukoff, included within Malvales (Fig. 7C).However this species has wide and rounded leaf bases.Ginalloa cumingiana Bentham & Hooker, a member of Santalales, has five basal veins but, unlike the studied specimens, the admedial primary veins are acrodromous (Fig. 7D).Several species within family Melastomataceae have also five basal veins as well as acrodromous admedial primary veins (e.g.Tristemma incompletum Brown or Barthea chinensis Hooker) (Fig. 7E-F).Based on the following characters (entire margins, palmate venation, secondary veins brochidodromous) and strong similarities with the extant Caryodaphnopsis tonkinensis and Sparattanthelium macusiorum, the new species from Isona is attributed to Laurales and the form-genus Cinnamomophyllum.This form-genus is assigned to leaves showing pseudo-palmate venation with a pair of admedial veins departing nearly to the petiole, parallel to and thicker than secondary veins, and thinner marginal veins (cf.Hill, 1986).

B C D E F G A
sented by a drawing of a partial leaf with pinnate camptodromous venation lacking more details (Capellini & Heer, 1867: pl. 1, fig. 5).A detailed description of A. parlatorii was provided by Berry (1914) with the following characters shared with the Isona specimens: cuneate or slightly decurrent base; midvein stout; secondaries, numerous, thin, subparallel, arising from the midvein at acute angles and camptodromous; tertiary veins mostly straight transverse.However, leaves belonging to A. parlatorii are longer (about 10-12 cm) and wider (3 cm).Extant species of Andromeda are included within Ericaceae.Marmi et al. (2014) assigned leaves from Isona to Dicot type 3 but did not resolve their botanical affinities.However, these authors found similarities among these specimens and Salix assimilis de Saporta, 1894 from the upper Albian from Nazareth (Portugal) ( de Saporta, 1894: pl. XXXVI, fig. 8;pl. XXXVII, figs. 2-3, 6, 13).Nevertheless, in some specimens drawn in the work by G. de Saporta, secondary veins were brochidodromous unlike the specimens from Isona (e.g. de Saporta, 1894: pl. XXXVII, fig. 13).The leaf fossils from Isona-sud named as Eudicot form 1 by Villalba-Breva et al. (2015) are very similar to the leaves herein described and likely belong to the same taxon (fig.3D, fig. 4A-B in Villalba-Breva et al., 2015).

Clade EUROSIDS I Order MALPIGHIALES?
Family SALICACEAE?Genus Saliciphyllum Fontaine, 1889 Type species.Saliciphyllum longifolium Fontaine, 1889 by original designation (p. 302, pl. 150, figs. 17-19).Saliciphyllum serratum n. sp.Description.Leaves are simple, microphyllous and lanceolate to linear (Fig. 11A).The apex is acuminate (Fig. 11D).Blades are partially preserved and, in some specimens, they are slightly curved (Fig. 11A).Laminae are medially symmetrical, 21.9-59.5 mm long and 6.4-15.1 mm wide.Margins are slightly serrate, bearing small, simple, triangular or hook-like teeth (Fig. 11A-C; Fig. 12) 0.3-0.4mm long and regularly spaced.There are three to four teeth per cm, separated by shallow, broad and rounded sinuses (Fig. 11B-C; Fig. 12).The venation is pinnate and mostly brochidodromous (Fig. 11A-C; Fig. 12A-B).The midvein is prominent and secondary veins are very thin.The secondary veins are regularly spaced and are excurrently attached to the midvein (Fig. 11A-B; Fig. 12A).The angles between secondary veins and the midvein slightly decrease towards the apex, ranging from 45º to 26º (Fig. 11A; Fig. 12A).A single intersecondary vein is present between some pairs of secondary veins (Fig. 11B).These veins run parallel to the major secondary veins and are at least half as long as the subjacent secondary vein.Details of higher order venation are not preserved in any of the specimens.
Small, elongate leaves with serrated margins and teeth similar to the studied leaves from Isona are found in different species within the genus Salix: S. alba Linnaeus (Fig. 13A), S. hindsiana Bentham (Fig. 13B), S. interior Rowke (Fig. 13C), S. melanopsis Nuttal (Fig. 13D) and S. purpurea Linnaeus (Fig. 13E).The secondary vein framework in these species is variable, including brochidodromous, semicraspedodromous and camptodromous secondary veins (Fig. 13).Based on these features, the new species from Isona is tentatively assigned to Salicaceae.In the upper Maastrichtian locality of Molí del Baró-1, the new Salix-like species Saliciphyllum gaetei Marmi et al., 2015, was described.It consisted of linear leaves with pinnate eucamptodromous to brochidodromous venation but having the margins entire instead of serrate (figs.5 and 6 in Marmi et al., 2015).Accordingly, the specimens from Isona are attributed to a different species within the genus Saliciphyllum.Description.Leaves are simple, petiolate and microphyllous.The petiole is long (21.5-23.6 mm long and 1.8-2.0mm wide), straight and marginally attached to the lamina (Fig. 14A-C).Laminae are incomplete, medially symmetrical and likely oblong (Fig. 14C; Fig. 15C), 20.9-58.1 mm long and 15.7-25.8mm wide.Margins are
Discussion.Most of the studied specimens were assigned to Rhamnus herendeensis [sic] Hollick 1930 by Vicente (2002), but MGB 38411 was classified as Acer (Rulac) quercifolium (Hollick) Vicente ( 2002) n. comb.by the same author.Both species were described by A. Hollick from the Upper Cretaceous of Alaska, USA.Rhamnus herendeenensis strongly resembles the specimens from Isona in general shape and venation (Hollick, 1930: pl. 78, figs. 8-10).On the contrary, Acer (Rulac) quercifolium has deeply crenate margins instead of entire margins (Hollick, 1930: pl. 77, figs. 1-10).Marmi et al. (2014) assigned these specimens to Dicot type 5 and compared them to Cornus sp. from the Upper Cretaceous of Vale de Madeira, Portugal.However, leaves of Cornus sp.seem more elongate than the leaves from Isona (Teixeira, 1950: pl. IV, figs. 8-8a).Like in the specimens from Isona, secondary veins of Cornus sp. are strongly bent toward the apex.However in the middle of the lamina, up to four secondary veins run parallel to the midvein (Teixeira, 1950: pl.IV, fig.8), a feature not observed in the studied leaves.
Similar leaf architecture features have been observed in extant members of Lauraceae and core eudicots.Cryptocarya kurzii (Hooker) Kostermans belongs to Lauraceae and resembles specimens from Isona in shape as well as in primary and secondary vein framework (Fig. 16A).However, in C. kurzii, tertiary veins are mixed percurrent and their spacing is wider.On the contrary, Couepia calophlebia Standley, within Chrysobalanaceae, has densely packed percurrent tertiary veins but secondary veins are more numerous and straight instead of curved towards the apex (Fig. 16B).The leaves of Scorodocarpus borneensis (Baillon) Beccari (Olacaceae) (Fig. 16C), Aulacocalyx jasminiflora Hooker (Rubiaceae) (Fig. 16D), Huodendron biaristatum (Smith) Rehder (Styracaceae) (Fig. 16E), Actinidia latifolia (Gardner & Champion) Merrill (Actinidiaceae) (Fig. 16F) and Afrocrania volkensii (Harms) Hutchinson (Cornaceae) (Fig. 16G), are elliptical or oblong, entire-margined and their venation is almost identical to that of the studied specimens.All these taxa are members of the Asterids or of their sister taxa (e.g.Santalales).Because of the similarities with Rhamnus herendeenensis as well as Cornus sp. from the Upper Cretaceous of Alaska and Portugal and taking into account that genus Cornus belongs to Asterids, the new combination Cornophyllum herendeenensis is proposed for the Isona leaf fossils.Etymology.From the village of Isona, head of the municipality in which the fossils were found.terminate at the margins (Fig. 17B; Fig. 18A-C).Quaternary and quinternary veins are reticulate, forming well-developed areoles (Fig. 17B-C; Fig. 18).Within areoles, once branched freely ending veinlets can be observed in the best preserved specimens (Fig. 17C).The marginal ultimate venation is looped (Fig. 17B; Fig. 18A).
Discussion.Vicente (2002) assigned most of the specimens to Carya heerii Ettingshausen, 1854.However, this species has dentate leaf margins instead of entire (cf.Heer, 1855-1859: pl. CXXXI, figs. 8-17).Specimen MGB 38390 was assigned to Eucalyptus geinitzii Heer, 1885 and MGB 38222 to Cinnamomum affine Lesquereux, 1868 by the same author.The former species has pinnate venation (cf.fig.1375 in Dana, 1896) and the lamina of the latter species is elliptic (cf.Knowlton, 1922: pl.VIII, fig.4).The venation in the middle of the lamina of the studied specimens closely resembles that of a partial leaf from the Upper Maastrichtian of Molí del Baró, in the same basin (figs.7A, 8A in Marmi et al., 2015) that was assigned to cf.Cocculophyllum sp. by the authors.However, in Cocculophyllum, exmedial primary veins connect with secondary veins which are brochidodromous (fig.1N in Kvaček, 1983).
Discussion.Vicente (2002) assigned the specimens to Caesalpinites ripleyensis Berry, 1925, Caesalpinites wilcoxensis Berry, 1930and Gleditsiophyllum preovatum Berry, 1925.These three taxa resemble the specimens from Isona in size and shape but, among them, they show remarkable differences in secondary venation.For instance, in C. ripleyensis secondary veins are simple brochidodromous (Berry, 1925: pl.XI, fig.6), while in G. preovatum, they are festooned brochidodromous (Berry, 1925: pl. XI, figs. 11-12).Marmi et al. (2014) assigned the specimens to Dicot type 8 and compared them with other leaf fossils from the Cretaceous of the Dakota Group (Kansas) and the Laramie Formation (Denver Basin) in the United States.
Leaves of similar shape with stout primary veins and short petioles are found in extant Eurosids orders Myrtales (Fig. 24D) and Sapindales (Fig. 24E-F) as well as in Asterids orders Ericales (Fig. 24G-H) and Gentianales (Fig. 24I-J).Based on these evidences, the parent plant of the fossil leaves from Isona likely belonged to Core Eudicots but, because of the lack of higher venation details, a more precise classification is not possible.Description.In all cases, the leaf lamina is partially preserved and the general shape is unknown.However, specimens likely correspond to microphyllous to notophyllous leaves.Teeth are lacking in all preserved margins suggesting that leaves were entire-margined.In general, venation is pinnate brochidodromous, becoming occasionally semicraspedodromous (Fig. 22D-F; Fig. 23D-F).Secondary veins are alternate.Intersecondary veins, if present, are perpendicular to the midvein and run parallel to major secondary veins (Figs.22E, G; Fig. 23E, G).Tertiary veins are prominent.Intercostal tertiary veins are straight, opposite percurrent and form obtuse angles compared to the midvein (Figs.22D-I; Fig. 23D-I).The epimedial tertiary veins are opposite percurrent, with a proximal course perpendicular to the midvein and the distal course basiflexed (Fig. 22D-F, H-I; Fig. 23 D-F, H-I).Exterior tertiary veins are simple brochidodromous (Figs.22H; Fig. 23H).In MGB 38213, quaternary and quinternary veins are preserved showing a reticulate framework and well-developed areoles (Fig. 22D; Fig. 23D).
Leaves with entire-margins and similar venation to the leaf fossils from Isona are found in several groups of extant Saxifragales (Fig. 25A), Eurosids (Fig. 25B-E) and Euasterids (Fig. 25F-G).This suggests that the studied specimens represent a Core Eudicot.However, because of the similarities with distantly related extant species and that general shape of the leaves is unknown, a more precise parataxonomic assignment is avoided.In fact, the possibility that specimens within Core Eudicot indet. 2 belong to more than a single taxon cannot be ruled out.Description.The specimens consist of three fragments of large, likely mesophyllous leaves the most complete of which (MGB 38368, Fig. 26A; Fig. 27A) is a large lamina base, 73.2 mm long and 140 mm wide, bearing an incomplete petiole 5.2 mm wide.Leaf margins are not preserved in any specimen.Venation is suprabasal actinodromous with five primary veins diverging radially from a single point (Fig. 26A; Fig. 27A).Likely compound agrophic veins are present (Fig. 26A-B; Fig. 27A-B).In MGB 38368, two opposite secondary veins arise from the midvein and some interior secondary veins are partially preserved (Fig. 26A; Fig. 27A).Specimen MGB 38216 is a more apical fragment of leaf showing opposite secondary veins and likely percurrent tertiary veins partially preserved (Fig. 26C; Fig. 27C).Discussion.Vicente (2002) assigned specimen MGB 38216 to Magnolia amplifolia Heer, 1869.However, this specimen is interpreted here as a fragment of a platanoidlike leaf based on the thick midvein and opposite secondary veins, which are similar to those shown in MGB 38368 (see Fig. 26A, C for comparisons).The latter specimen and MGB 38369 were assigned to Platanus aceroides Goeppert, in Lesquereux, 1878 by Vicente (2002).Partial leaves belonging to this species were drawn in Heer (1885: pl. 12, fig.1-5) and show opposite secondary veins diverging from a straight and stout midvein as well as likely compound agrophic veins.However, any of these specimens show clear actinodromous venation but see Hollick (1936: pl. 68, fig. 2).
Venation features observed in the studied specimens are found in species within the extant Platanaceae such as Platanus x acerifolia (Aiton) Willdenow (Fig. 28A) as well as in members of Eurosids (Fig. 28B-C) and Euasterids (Fig. 28D).However, species belonging to these two latter groups used for comparison (Fig. 28B-D) are mostly notophyll instead of mesophyll.Thus, a likely affinity to Platanaceae is proposed for the leaf fossils from Isona.Following Maslova et al. (2005) and Maslova & Herman (2015), the studied Platanus-like leaves are tentatively assigned to the genus Ettingshausenia.Description.Leaves are microphyllous, 32.4-48.6 mm long and 15.4-25-4 mm wide, giving a length/width ratio of 1.9-2.1.Laminae are bi-lobed, heart-shaped and symmetrical (Fig. 26D-E; Fig. 27D-E).The apex is reflex and the base acute, becoming strongly narrow toward the petiole.Margins are poorly preserved but some tiny teeth are visible near the apex of specimen MGB 38396 (Fig. 26F; Fig. 27E).Teeth are 1.5-2.1 mm long and 0.2-0.4mm in width.They are separated each other by rounded sinuses (Fig. 26F; Fig. 27E).The primary vein splits dichotomously into two veins that form the midvein of each lobe (Fig. 26D; Fig. 27D).
Discussion.Vicente (2002) assigned the specimens to the new species Celastrophyllum bilobatum.Genus Celastrophyllum is featured by small sized, elliptic leaves with decurrent bases, dentate margins and brochidodromous venation (Herman & Kvaček, 2010).However, leaves from Isona are bi-lobed and details of secondary venation are not preserved.Marmi et al. (2014) assigned the specimens to Dicot type 11 and compared them to Liriophyllum obcordatum Lesquereux, 1892.This species has the laminae bi-lobed but their margins are entire instead of dentate (Lesquereux, 1892: pl. XXVIII, fig. 7).
Similar bi-lobed leaves have been observed in extant Eurosids within Rosales (Fig. 28E) and Celastrales (Fig. 28F).Based on these evidences and the presence of dentate margins, the leaf fossils from Isona are assigned to Eurosids and the species proposed by Vicente (2002)  Description.The single specimen is an almost entire leaf, elliptic in shape, with a symmetrical lamina 46.8 mm long and 23.8 mm wide (Fig. 26G).It only lacks the basalmost end of the lamina and the petiole.The apex is not completely preserved but seems acuminate (Fig. 26G).Margin is serrate in the middle of the lamina (concave/straight teeth separated each other by rounded sinuses), becoming crenate near the apex (convex/convex teeth separated each other by angular sinuses) (Figs.26G; Fig. 27F).There is only one order of teeth which are regularly spaced giving a density of three to five teeth per centimeter.The primary vein is pinnate, and the secondary veins seem festooned semicraspedodromous (Figs.26G; Fig. 27F).Secondary veins are not regularly spaced and arise from the primary vein forming inconsistent angles.There is less than one intersecondary vein per intercostal area.They are less than half shorter than the subjacent secondary veins and their courses are parallel to major secondary veins.Intercostal and epimedial tertiary veins, as well as quaternary tertiary veins, are reticulate (Figs.26G; Fig. 27F).
Discussion.Vicente (2002) assigned this specimen to Celastrus splendidus de Saporta, 1867.However, in this species the apex is slightly emarginate and tertiary veins percurrent instead of reticulate ( de Saporta, 1867: pl. 8, fig.2).Marmi et al. (2014) pointed out that the specimen from Isona strongly resembles the extant species Celastrus auriculatus Vitman (Fig. 28G).These authors assigned the leaf fossil to Celastrophyllum based on similarities with C. auriculatus as well as the following features that are typical of the form-genus: small size, elliptic shape, dentate to crenate margins, venation pinnate and reticulate tertiary and quaternary veins.Description.The fossils consist of partial laminae except specimens MGB 38340 and MGB 38341, which are complete leaves bearing the petioles marginally attached (Fig. 29A-B; Fig. 30A-B).Leaves are notophyllous, with laminae 76.7-95.9mm long and 41.5-44.7 mm wide.Laminae length/width ratio is 1.9-2.1.The petiole is 38 mm long and 1.2 mm wide in MGB 38341 (Fig. 29A; Fig. 30A).The shape of the lamina is ovate and symmetrical.The lamina base is slightly asymmetrical, convex and acute while the apex is symmetrical, straight and acute (Fig. 29A-C; Fig. 30A-C).The distal two thirds of the margins are slightly dentate.There is one order of regularly spaced teeth, giving a density of 1 to 2 teeth per cm (Fig. 29A-C, F, G; Fig. 30A-D, G).Teeth are generally concave/concave (Fig. 29A, C-

F
G H E D) but, less frequently, they may also be convex/concave (Fig. 29F).They are separated each other by rounded sinuses (Fig. 29A, C-D, F, I; Fig. 30A, C-D, G) and their apices seem mucronate (Fig. 29D).Venation is pinnate craspedodromous.The secondary veins are alternate and not regularly spaced from each other.They arise from the midvein at acute angles, which smoothly decrease proximally, and end at the tooth apices (Fig. 29A, D; Fig. 30A).Intersecondary veins, when present, run parallel to major secondary veins and are less than half the length of the subjacent secondary vein (Fig. 29A, G; Fig. 30A-E).Specimens MGB 38373 and MGB 38375 preserve details of tertiary veins.Intercostal tertiary veins are opposite percurrent (Fig. 29G; Fig. 30E) and epimedial tertiary veins form a chevron or are mixed percurrent (Fig. 29C, E, G; Fig. 30C, E).Epimedial tertiary veins are proximally acute to midvein and distally basiflexed (Fig. 30E).Exterior tertiary veins are straight and terminate at the margin (Fig. 29C, E; Fig. 30C).Likely reticulate quaternary and quinternary veins are weakly preserved in MGB 38375 (Fig. 29D).
Discussion.Vicente (2002) assigned the studied material to four new species: Populus paleomutabilis, P. intermedia, P. rhomboidalis and Betula protopendula.However, Marmi et al. (2014) suggested that the specimens belong to a single leaf morphotype (Dicot type 13) which might represent the same taxon.Specimen MGB 38372 was assigned to Platanus aceroides by Vicente (2002) but it closely resembles the apical end of MGB 38341 in general shape and marginal features (Fig. 29A and I, respectively).Marmi et al. (2014) also compared the specimens from Isona to Viburnum sphenophyllum Knowlton, in Lesquereux, 1892 and Quercus dakotensis Lesquereux, 1892 from the Upper Cretaceous Dakota Group, United States.These species have laminar shapes and tooth features very similar to the studied specimens and also present pinnate craspedodromous venation.However, they lack intersecondary veins and the number of secondary veins is higher than in the fossil leaves from Isona (Lesquereux, 1892: pl. LIII, fig. 4;pl. VII, fig. 4).
The studied specimens share blade shape, venation and dentition features with different taxa included within the clade Eurosids 1 (Fig. 31).The laminar and tooth shapes of specimens from Isona strongly resemble those of the leaves of Fagus grandifolia Ehrhart (Fig. 31E) and Maytenus bilocularis von Mueller (Fig. 31G).However, the latter species has semicraspedodromous instead of craspedodromous secondary veins.Ovate leaves with dentate margins composed of concave/concave teeth separated from each other by rounded sinuses are also typical of species of genus Betula (Fig. 31A-D).Moreover, these leaves have pinnate craspedodromous venation, with secondary veins terminating at the tooth apices, and relatively long petioles as it was observed in the leaf fossils from Isona.However, in some extant species of Betula, two orders of teeth have been observed (e.g.Betula nigra Linnaeus, Fig. 31B; and Betula verrucosa Ehrhart, Fig. 31D).According to similarities with extant species of genus Betula, the studied specimens are assigned to genus Betuliphyllum, which was proposed by Dusén (1899) for naming Betulaceae-like fossil leaves.Description.Specimen MGB 38335 consists of a simple, microphyllous, partially preserved leaf that is 43.6 mm long and 41.2 mm wide (Fig. 32A).The lamina is nearly circular and entire-margined (Fig. 32A; Fig. 33A).The apex and the base are obtuse and rounded.The midvein is straight and stout.Secondary veins are thin and seem brochidodromous (Fig. 32A-B; Fig. 33A).Intercostal tertiary veins are straight opposite percurrent and form obtuse angles compared to the primary vein (Fig. 32B; Fig. 33A).Exterior tertiary veins are also straight and likely terminate at the margin (Fig. 32B; Fig. 33A).Quaternary venation is partially preserved and seems reticulate (Fig. 32B; Fig. 33A).
Discussion.Vicente (2002) assigned the specimen to Cercidiphyllum arcticum Brown, 1962.However, this species has acrodromous venation instead of pinnate venation and their margins are usually toothed (Brown, 1962: pl. 37, figs. 8-9, 13, 15, 17, 20, 22).Leguminosites mucronatus Herman & Kvaček, 2010 from the lower Campanian of Austria is similar in size, marginal features and venation to the studied specimen, although its blade shape is broadly elliptic instead of circular (fig.35 in Herman & Kvaček, 2010).MGB 38335 also resembles the extant Glyptopetalum orbiculare Merrill in shape and venation (Fig. 34A).This species belongs to Celastraceae.Description.Leaves are linear, microphyllous, 62.3-62.8mm long and 14.3-15.2mm wide.In both specimens, the lamina base is lost (Fig. 32C-D).The lamina apex seems acute but its shape is difficult to discern because it is not well preserved in any specimen (Fig. 32C).The lamina is medially symmetrical and the margins are entire (Fig. 32C).The midvein is straight and stout (Fig. 32C, E).A great number of thin secondary veins arise from the midvein at nearly right angles (69º-87º) and terminate at the margins (Fig. 32E-F).Moreover, the secondary veins are very close and run parallel to each other (Fig. 32F).Discussion.Vicente (2002) assigned both specimens to his new species Nilssonia annavilae.Elongated leaves with entire margins showing similar venation are usually found in the cycadalean genus Nilssonia (e.g.fig.19 in Herman & Kvaček, 2010).However, this genus is also featured by lamina ruptures simulating segmentation, which has not been observed in the studied specimens.The particular venation of the leaf fossils from Isona is also found in living angiosperms within the clades Eurosids 1 (Fig. 34B) and Euasterids 1 (Fig. 34C-E).Accordingly, the specimens are tentatively assigned to indeterminate Core Eudicots.MGB 38295,MGB 38359,MGB 38378,MGB 38387,MGB 38389,MGB 38414.Occurrence.Isona-sud site (see Villalba-Breva et al., 2015 for details).
Description.The fossils are fragments of microphyllous, linear leaves that are medially symmetrical and have entire margins (Fig. 32G-K; Fig. 33B-F).The fragments are 28.4-122.6mm long and 4.33-18.5 mm wide.Apex is acute and straight and is preserved in a very few specimens (e.g.Fig. 32H).The venation is pinnate.All specimens show a straight and stout midvein.Secondary veins are very thin and partially preserved in some specimens (Fig. 33B, D-E).They are excurrently attached to the midvein from which they arise forming acute angles (28.5º-43.9º).

DISCUSSION
The new revision of the dicot leaf fossils of the Vicente collection has allowed assigning 131 specimens to 16 taxa.Two of them, Core Eudicot indet.3 and Dicotylophyllum cf.proteoides, were not previously described by Marmi et al. (2014).In addition, these authors assigned several fragments of linear pinnatisect leaves in eight specimens to the Dicot type 15, which was considered dicot foliage of uncertain botanical affinity.This morphotype has not been revised here because of the lack of similar extant dicot leaves in the Cleared Leaf Databases.Thus, the plant fossil assemblage of the Isona-sud site could include up to a total of 17 dicot taxa.Hypotheses on the suprageneric taxonomy of 16 taxa were proposed on the basis of comparisons of leaf architecture features among fossil specimens and cleared leaves of extant taxa.Accordingly, two of them (Daphnogene cf.lanceolata and Cinnamomophyllum vicente-castellum n. sp.) could represent members of Magnoliids and the remaining are included within Eudicots.Within this latter clade, dicot leaves from Isona-sud could represent basal Eudicots such as Proteales (Ettingshausenia sp.) as well as likely members of Eurosids I (Saliciphyllum serratum n. sp., Alnophyllum sp., Celastrophyllum bilobatum, Celastrophyllum sp., Betuliphyllum sp. and Eurosid 1 indet.),Eurosids II (Myrtophyllum) and Asterids (Cornophyllum herendeenensis).Within the clade Rosids, the families Salicaceae, Betulaceae and Celastraceae are tentatively identified.The Salicaceae have a particularly extensive fossil record in the Cenozoic but the only secure Cretaceous record of their inclusive order (the Malpighiales) are the fossil flowers of Paleoclusia (Clusiaceae) (Friis et al., 2011).Similarly, several leaves and seeds assigned to Celastraceae have been described from the Eocene onwards in Europe and North America (Collinson et al., 1993).However, Salix-like and Celastrus-like leaves are common in the Late Cretaceous fossil record.In addition, recent molecular analyses suggest that stem Salicaceae and Celastrales evolved during the Cretaceous (Bell et al., 2010;Xi et al., 2012).On the contrary, the Fagales are well documented in the Late Cretaceous floras (Friis et al., 2011) and are frequent in the sporomorph record of the uppermost Cretaceous of the Iberian Peninsula (Diéguez et al., 2010).Pollen assigned to Fagales was also reported in the plant bearing beds of the Isona-sud site (Villalba-Breva et al., 2015).
From a phytogeographical point of view, Vicente (2002) estimated that 72% of the taxa from the Isona flora were shared with North American floras and 35% and the 3% with Eurasian and Arctic floras, respectively. 1 Marmi et al. (2014) also suggested that the Isona flora was a mixture of elements from other Creta ceous floras of Europe and North America.This is suported by the presence of the fossil palm Sabalites longirhachis in Campanian-Maastrichtian localities from France, Austria and Romania in addition to the southern Pyrenees.Sabalites palms are also reported from the Upper Cretaceous of North America.Taxodioid conifers are shared with other Upper Cretaceous localities from Portugal, Austria as well as Central and Eastern Europe (see details in Marmi et al., 2014).Current data agree with the previous studies.For instance, Daphnogene sp. and Dicotylophyllum proteoides are common in the Cretaceous and Tertiary of Central Europe (Hably, 1989;Herman & Kvaček, 2010) and Cornophyllum cf.heredeenensis suggests a relationship with Upper Cretaceous floras from North America.However, the three new species described in the present work together with Celastrophyllum bilobatum could reveal some degree of uniqueness in the flora from the Lower Maastrichtian of Isona.This is consistent with the palaeogeography of southern Europe during the latest Cretaceous.Emerged lands of the Iberian Peninsula and southern France formed a large island, the so called Iberoarmorican Domain, in the westernmost edge of the Southern European archipelago (Dercourt et al., 2000).The Iberoarmorican Domain was isolated from landsmasses of Central and Eastern Europe by the Tethys seawaters.However, it is important to note that the Lower Maastrichtian flora of Isona is not coeval to some of the other Cretaceous floras used for comparisons; for instance, those of the Albian of Nazareth (Portugal), the Cenomanian of Bohemia (Czech Republic) or the lower Campanian of Grünbach (Austria).In addition, taxonomic composition of the fossil plant assemblages is strongly influenced by environment and taphonomy.Based on Villalba-Breva et al. (2015), plant remains from Isona were parautochthonous and allochthonous and deposited in a distal floodplain.Although it is likely that most of the parent plants grew somewhere in the floodplain and surronding environments, a more precise habitat was only possible to infer for trees or shrubs bearing Alnophyllum leaves.These alder-like plants probably inhabited river banks or environments close to the overflow point, forming riparian vegetation (Villalba-Breva et al., 2015).

CONCLUSIONS
The paleobotanical collection of Mr. Joan Vicente i Castells is among the most important in Europe.It is composed of around 400 specimens including taxodioid and cheirolepidiacean conifers, likely pandanales, Sabalites palms and a variety of dicotyledoneous foliage.The 131 dicot leaf specimens of this collection have been tentatively assigned to 17 taxa representing Magnoliids, Proteales, Eurosids and Asterids.
In spite of the high convergence among leaf architecture features, the fragmentary nature of most of specimens and the lack of cuticular data, possible members of Salicaceae, Betulaceae and Celastraceae have been identified within the clade Rosids.Family Lauraceae has tentatively been identified within Magnoliids.
The Isona flora shares some taxa with other Upper Cretaceous-Tertiary localities from Europe and North America.However, there are some dicot taxa that seem unique in this Pyrenean locality.Many Cretaceous fossil floras from Europe and North America are pending revision.Among the few examples of revised floras in Europe there is the Grünbach (Austria) lower Campanian one (Herman & Kvaček, 2010).Thus, a better understanding of the diversity of Late Cretaceous floras from Europe and North America depends on a deep taxonomic revision of all the available fossil material in addition to a better knowledge of the taphonomy and geological setting of their original localities.Only then, the uniqueness of some Cretaceous floras, such as that of Isona, will be able to be rigorously evaluated.

ACKNOWLEDGEMEN TS
I dedicate this paper to Mr. Joan Vicente i Castells (1921-2010), a great humanist and enthusiastic naturalist, one of the discoverers of the plant fossil sites from Isona, and one of the people who carried out the first extensive study of this outstanding fossil plant collection.I also thanks Drs.Julio Gómez-Alba ( †) and Vicent Vicedo, curators of at the Museu de Geologia-Museu de Ciències Naturals de Barcelona, for allowing me to study this plant collection.I am very grateful to Ms. Roser Vicente who provided his father's picture Fig. 1A.The study was funded by the Ministerio de Economia y Competitividad, Spanish Government (project CGL2011-30069-C02-01/02).

Fig. 1 .
Fig. 1.A, Picture of Joan Vicente Castells taken at the Isona-sud site in 2003.B, Cover of the monograph on the Isona flora published by J. Vicente in 2002.Fig. 1.A, Fotografía de Joan Vicente Castells tomada en el yacimiento Isona-sud en 2003.B, Portada de la monografía sobre la flora de Isona publicada por J. Vicente en 2002.
honour of Mr. Joan Vicente Castells, enthusiastic amateur palaeobotanist who carried out the first systematic study of the Isona flora.Type locality.Isona-sud site, located along the Pont del Molí trail, 500 metres south of Isona village (Isona i Conca Dellà municipality, comarca (=county) Pallars Jussà, Lleida province, Catalonia, NE Spain).Stratigraphic position.Marly beds belonging to the Xullí unit of the lower part of the Tremp Formation (see Villalba-Breva et al., 2015 for details).Age.Early Maastrichtian as determined by stratigraphic correlation and biostratigraphy (see Villalba Breva et al., 2015 for details).