A new remarkable Early Cretaceous nelumbonaceous fossil bridges the gap between herbaceous aquatic and woody protealeans.

Dating back to the late Early Cretaceous, the macrofossil record of the iconic lotus family (Nelumbonaceae) is one of the oldest of flowering plants and suggests that their unmistakable leaves and nutlets embedded in large pitted receptacular fruits evolved relatively little in the 100 million years since their first known appearance. Here we describe a new fossil from the late Barremian/Aptian Crato Formation flora (NE Brazil) with both vegetative and reproductive structures, Notocyamus hydrophobus gen. nov. et sp. nov., which is now the oldest and most complete fossil record of Nelumbonaceae. In addition, it displays a unique mosaic of ancestral and derived macro- and micromorphological traits that has never been documented before in this family. This new Brazilian fossil-species also provides a rare illustration of the potential morphological and anatomical transitions experienced by Nelumbonaceae prior to a long period of relative stasis. Its potential plesiomorphic and apomorphic features shared with Proteaceae and Platanaceae not only fill a major morphological gap within Proteales but also provide new support for their unexpected relationships first suggested by molecular phylogenies.

Vegetation and climate change at the southern margin of the Neo-Tethys during the Cenomanian (Late Cretaceous): Evidence from Egypt.

Changes in terrestrial vegetation during the mid-Cretaceous and their link to climate and environmental change are poorly understood. In this study, we use plant macrofossils and analysis of fossil pollen and spores from the Western Desert, Egypt, to assess temporal changes in plant communities during the Cenomanian. The investigated strata have relatively diverse sporomorph assemblages, which reflect the nature of parent vegetation. Specifically, the palynofloras represent ferns, conifers, monosulcate pollen producers, Gnetales, and a diverse group of angiosperms. Comparisons of both, dispersed palynoflora and plant macrofossils reveal different characteristics of the palaeoflora owing to a plethora of taphonomical and ecological biases including the depositional environment, production levels, and discrepancies between different plant organs. A combination of detailed records of sporomorphs, leaves, and charcoal from the studied successions provide new understandings of the palaeoclimate and palaeogeography during the Cenomanian and Albian-Cenomanian transition in Egypt. The mixed composition of the palynofloral assemblages reflects the presence of different depositional situations with a weak marine influence, as evidenced by a minor dinoflagellate cysts component. The local vegetation comprised various categories including herbaceous groups including ferns and eudicots, fluvial, open environments, and xeric arboreal communities dominated by Cheirolepidiaceae and perhaps including drought- and/or salt-tolerating ferns (Anemiaceae) and other gymnosperms (Araucariaceae, Ginkgoales, Cycadales, and Gnetales) as well as angiosperms. The presence of riparian and freshwater wetland communities favouring aquatic and/or hygrophilous ferns (of Salviniaceae and Marsileaceae), is noted. The wide variation of depositional settings derived from the palynological data may be attributed to a prevalent occurrence of producers in local vegetation during the early Cenomanian of Egypt. For the purpose of this work on the studied Bahariya Formation and its equivalent rock units, where iconic dinosaurs and other fossil fauna roamed, we attempt to improve the understanding of Egypt's Cenomanian climate, which is reconstructed as generally warm and humid punctuated by phases of considerably drier conditions of varying duration.

First evidence of ranunculids in Early Cretaceous tropics.

Early Cretaceous floras containing angiosperms were described from several geographic areas, nearly from the Arctic to the Antarctic, and are crucial to understand their evolution and radiation. However, most of these records come from northern mid-latitudes whereas those of lower paleolatitude areas, such as the Crato Fossil Lagerstätte in NE Brazil, are less studied. Here, we describe from this region of northern Gondwanan origin, two fossil-species of eudicots belonging to a new extinct genus Santaniella gen. nov. Together with several vegetative axes and leaves, anatomically well-preserved fruits with seeds and persistent perianth-like organs allowed us to reconstruct its potential affinities with ranunculids, and presumably Ranunculaceae. Previous records putatively assigned to Ranunculales are all from mid-latitudes, and their first unequivocal occurrence in a low-latitude area supports further the hypothesis of a widespread radiation of the earliest diverging eudicot lineage by this early age.

Fossil evidence of core monocots in the Early Cretaceous.

All the major clades of angiosperms have a fossil record that extends back to more than 100 million years ago (Early Cretaceous), mostly in agreement with molecular dating. However, the Early Cretaceous record of monocots is very poor compared to other angiosperms. Their herbaceous nature has been invoked to explain this rarity, but biogeography could also be an explanation. Unfortunately, most of the Early Cretaceous angiosperm record comes from northern mid-latitudes. The Crato plattenkalk limestone offers a unique window into the Early Cretaceous vegetation of the tropics and has already yielded monocot fossils. Here, we describe a whole monocotyledonous plant from root to reproductive organs that is anatomically preserved. The good preservation of the fossils allowed the evaluation of reproductive, vegetative and anatomical characteristics of monocots, leading to a robust identification of this fossil as a crown monocot. Its occurrence in Northern Gondwana supports the possibility of an early radiation of monocots in the tropics.

Montsechia, an ancient aquatic angiosperm.

The early diversification of angiosperms in diverse ecological niches is poorly understood. Some have proposed an origin in a darkened forest habitat and others an open aquatic or near aquatic habitat. The research presented here centers on Montsechia vidalii, first recovered from lithographic limestone deposits in the Pyrenees of Spain more than 100 y ago. This fossil material has been poorly understood and misinterpreted in the past. Now, based upon the study of more than 1,000 carefully prepared specimens, a detailed analysis of Montsechia is presented. The morphology and anatomy of the plant, including aspects of its reproduction, suggest that Montsechia is sister to Ceratophyllum (whenever cladistic analyses are made with or without a backbone). Montsechia was an aquatic angiosperm living and reproducing below the surface of the water, similar to Ceratophyllum. Montsechia is Barremian in age, raising questions about the very early divergence of the Ceratophyllum clade compared with its position as sister to eudicots in many cladistic analyses. Lower Cretaceous aquatic angiosperms, such as Archaefructus and Montsechia, open the possibility that aquatic plants were locally common at a very early stage of angiosperm evolution and that aquatic habitats may have played a major role in the diversification of some early angiosperm lineages.

Rise to dominance of angiosperm pioneers in European Cretaceous environments.

The majority of environments are dominated by flowering plants today, but it is uncertain how this dominance originated. This increase in angiosperm diversity happened during the Cretaceous period (ca. 145-65 Ma) and led to replacement and often extinction of gymnosperms and ferns. We propose a scenario for the rise to dominance of the angiosperms from the Barremian (ca. 130 Ma) to the Campanian (ca. 84 Ma) based on the European megafossil plant record. These megafossil data demonstrate that angiosperms migrated into new environments in three phases: (i) Barremian (ca. 130-125 Ma) freshwater lake-related wetlands; (ii) Aptian-Albian (ca. 125-100 Ma) understory floodplains (excluding levees and back swamps); and (iii) Cenomanian-Campanian (ca. 100-84 Ma) natural levees, back swamps, and coastal swamps. This scenario allows for the measured evolution of angiosperms in time and space synthesizing changes in the physical environment with concomitant changes in the biological environment. This view of angiosperm radiation in three phases reconciles previous scenarios based on the North American record. The Cretaceous plant record that can be observed in Europe is exceptional in many ways. (i) Angiosperms are well preserved from the Barremian to the Maastrichtian (ca. 65 Ma). (ii) Deposits are well constrained and dated stratigraphically. (iii) They encompass a full range of environments. (iv) European paleobotany provides many detailed studies of Cretaceous floras for analysis. These factors make a robust dataset for the study of angiosperm evolution from the Barremian to the Campanian that can be traced through various ecosystems and related to other plant groups occupying the same niches.

Fossil evidence for Cretaceous escalation in angiosperm leaf vein evolution.

The flowering plants that dominate modern vegetation possess leaf gas exchange potentials that far exceed those of all other living or extinct plants. The great divide in maximal ability to exchange CO(2) for water between leaves of nonangiosperms and angiosperms forms the mechanistic foundation for speculation about how angiosperms drove sweeping ecological and biogeochemical change during the Cretaceous. However, there is no empirical evidence that angiosperms evolved highly photosynthetically active leaves during the Cretaceous. Using vein density (D(V)) measurements of fossil angiosperm leaves, we show that the leaf hydraulic capacities of angiosperms escalated several-fold during the Cretaceous. During the first 30 million years of angiosperm leaf evolution, angiosperm leaves exhibited uniformly low vein D(V) that overlapped the D(V) range of dominant Early Cretaceous ferns and gymnosperms. Fossil angiosperm vein densities reveal a subsequent biphasic increase in D(V). During the first mid-Cretaceous surge, angiosperm D(V) first surpassed the upper bound of D(V) limits for nonangiosperms. However, the upper limits of D(V) typical of modern megathermal rainforest trees first appear during a second wave of increased D(V) during the Cretaceous-Tertiary transition. Thus, our findings provide fossil evidence for the hypothesis that significant ecosystem change brought about by angiosperms lagged behind the Early Cretaceous taxonomic diversification of angiosperms.

Extreme longevity in trees: live slow, die old?

We have examined the extreme longevity displayed by trees in relation to a theory mainly developed in animals, namely, the controversial rate of living (ROL) theory of aging which proposes that longevity is negatively correlated to metabolic rate. Plant metabolism implies respiration and photosynthesis; both are susceptible to negatively impact longevity. The relationship between longevity and metabolism was studied in leaves and stems of several species with the aim of challenging the ROL theory in trees. Leaf and stem life spans were found to be highly correlated to metabolism (R(2) = 0.97), and stems displayed a much lower metabolism than leaves. Analysis of covariance (ANCOVA), with metabolism as the covariate, revealed no difference between mean leaf and stem life spans, which would appear to conform to the expectations of the ROL theory. Consequently, the extremely high longevity of trees may be explained by the lower metabolism displayed by the stems. These results clearly reflect different energy allocation and energy expenditure rate strategies between leaves and stems, which may result in different senescence rates (and life spans) in these organs. They also suggest that, in contrast to animals, the ROL theory of aging may apply to woody plants at the organ level, thereby opening a promising new line of research to guide future studies on plant senescence.