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Ray-finned bony fish (ranging from cod to guppies) and lobe-finned bony fish (lungfish, coelacanths and the ancestors of the land vertebrates) were clearly once close relatives, but a large morphological gulf still separates fossils of both groups dating from times when they looked much more similar than they do now. A fossil of a primitive lobe-finned fish that combines many features found in both groups has now been discovered in the Yumman fossil beds in China, and this new species offers a bridgehead between the two distinct lines of fishy descent. A primitive fossil species of lobe-finned fish combines many histological features found in both ray-finned bony fishes and lobe-finned bony fishes. Osteichthyans, or bony vertebrates, include actinopterygians (teleosts and their relatives) and sarcopterygians (coelacanths, lungfishes and tetrapods). Despite features found in basal actinopterygians (for example, Dialipina and Ligulalepis)1,2,3 and basal sarcopterygians (for example, Psarolepis and Achoania)4,5, the morphological gap between the two lineages remains wide and how sarcopterygians developed a dermal surface covering known as cosmine (composed of a pore–canal network and a single layer of odontodes and enamel) is still poorly known6,7,8,9,10. Here we describe a primitive fossil fish, Meemannia eos gen. et sp. nov., that possesses an actinopterygian-like skull roof and a cosmine-like dermal surface combining a pore–canal network (found in various fossil sarcopterygians) with superimposed layers of odontodes and enamel (previously known in actinopterygians and some acanthodians11,12,13). This 405-million-year-old fish from the Lower Devonian of Yunnan (China) demonstrates that cosmine in many fossil sarcopterygians arose step by step through the acquisition of a pore–canal network followed by the subsequently developed ability to resorb previous generations of odontodes and enamel. Meemannia provides key characters for studying deep osteichthyan phylogeny and indicates a possible morphotype for the common ancestor of actinopterygians and sarcopterygians.

Global energy consumption is expected to grow by 50% by 2030, squeezing already scarce water resources. Mike Hightower and Suzanne A. Pierce recommend ways to integrate water and energy planning. Over a billion people around the world lack access to safe drinking water and over two billion have little or no sanitation. Do we have the resources — and the will — to provide the water to support a booming population? This issue of Nature (see introduction, p. 269 and Editorial, p. 253) tackles the science, economics and politics of the global water crisis. Climate scientists say that unreliable rains and drier summer soils will become more common: Quirin Schiermeier reports on water strategies for a drier world. The pressure is on farmers to get maximum crop yields with minimum water use. As Emma Marris reports, the collaboration between plant breeders, agronomists and geneticists to that end has been far from smooth. As the population of India grows, the demand for water keeps rising. Daemon Fairless investigates an ambitious plan to redistribute the country's water supplies by linking rivers in a vast canal network. Jamie Bartram says it is time to improve the global targets for access to water and sanitation to make them relevant to all. In most countries, crop irrigation accounts for most freshwater use — more than drinking water and domestic consumption — but water use in energy production is catching up fast. Mike Hightower and Suzanne Pierce describe the measures being developed to economize on water use in the energy sector. The need for research into water purification is pressing. In an extensive Review Article, Mark Shannon et al. highlight the developing technologies that — it is hoped — can provide our drinking water in the decades ahead. Water is (almost) everywhere, yet physicists still trade theory and counter theory to explain its structure: Phil Ball explains. And Books & Arts looks at a documentary on water security, and at art inspired by water's surprising patterns. Go to http://www.nature.com/news/specials/water/index.html for the on-line start-page.

All-or-nothing targets for global access to basic amenities such as drinking water and sanitation are outdated. The time has come, says Jamie Bartram, for a more fluid approach. Over a billion people around the world lack access to safe drinking water and over two billion have little or no sanitation. Do we have the resources — and the will — to provide the water to support a booming population? This issue of Nature (see introduction, p. 269 and Editorial, p. 253) tackles the science, economics and politics of the global water crisis. Climate scientists say that unreliable rains and drier summer soils will become more common: Quirin Schiermeier reports on water strategies for a drier world. The pressure is on farmers to get maximum crop yields with minimum water use. As Emma Marris reports, the collaboration between plant breeders, agronomists and geneticists to that end has been far from smooth. As the population of India grows, the demand for water keeps rising. Daemon Fairless investigates an ambitious plan to redistribute the country's water supplies by linking rivers in a vast canal network. Jamie Bartram says it is time to improve the global targets for access to water and sanitation to make them relevant to all. In most countries, crop irrigation accounts for most freshwater use — more than drinking water and domestic consumption — but water use in energy production is catching up fast. Mike Hightower and Suzanne Pierce describe the measures being developed to economize on water use in the energy sector. The need for research into water purification is pressing. In an extensive Review Article, Mark Shannon et al. highlight the developing technologies that — it is hoped — can provide our drinking water in the decades ahead. Water is (almost) everywhere, yet physicists still trade theory and counter theory to explain its structure: Phil Ball explains. And Books & Arts looks at a documentary on water security, and at art inspired by water's surprising patterns. Go to http://www.nature.com/news/specials/water/index.html for the on-line start-page.

Over a billion people around the world lack access to safe drinking water and over two billion have little or no sanitation. Do we have the resources — and the will — to provide the water to support a booming population? This issue of Nature (see introduction, p. 269 and Editorial, p. 253) tackles the science, economics and politics of the global water crisis. Climate scientists say that unreliable rains and drier summer soils will become more common: Quirin Schiermeier reports on water strategies for a drier world. The pressure is on farmers to get maximum crop yields with minimum water use. As Emma Marris reports, the collaboration between plant breeders, agronomists and geneticists to that end has been far from smooth. As the population of India grows, the demand for water keeps rising. Daemon Fairless investigates an ambitious plan to redistribute the country's water supplies by linking rivers in a vast canal network. Jamie Bartram says it is time to improve the global targets for access to water and sanitation to make them relevant to all. In most countries, crop irrigation accounts for most freshwater use — more than drinking water and domestic consumption — but water use in energy production is catching up fast. Mike Hightower and Suzanne Pierce describe the measures being developed to economize on water use in the energy sector. The need for research into water purification is pressing. In an extensive Review Article, Mark Shannon et al. highlight the developing technologies that — it is hoped — can provide our drinking water in the decades ahead. Water is (almost) everywhere, yet physicists still trade theory and counter theory to explain its structure: Phil Ball explains. And Books & Arts looks at a documentary on water security, and at art inspired by water's surprising patterns. Go to http://www.nature.com/news/specials/water/index.html for the on-line start-page.