Flightless bird

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Flightless_bird

 

Penguins are a well-known example of flightless birds.

 

Ostriches are the largest extant flightless birds as well as the largest extant birds in general.

 

Flightless birds are birds that through evolution lost the ability to fly. There are over 60 extant species, including the well known ratites (ostriches, emu, cassowaries, rheas and kiwi) and penguins. The smallest flightless bird is the Inaccessible Island rail (length 12.5 cm, weight 34.7 g). The largest (both heaviest and tallest) flightless bird, which is also the largest living bird, is the ostrich (2.7 m, 156 kg). Ostriches are farmed for their decorative feathers, meat and their skins, which are used to make leather. 

Many domesticated birds, such as the domestic chicken and domestic duck, have lost the ability to fly for extended periods, although their ancestral species, the red junglefowl and mallard, respectively, are capable of extended flight. A few particularly bred birds, such as the Broad Breasted White turkey, have become totally flightless as a result of selective breeding; the birds were bred to grow massive breast meat that weighs too much for the bird's wings to support in flight.

Flightlessness has evolved in many different birds independently. There were families of flightless birds, such as the now extinct Phorusrhacidae, that evolved to be powerful terrestrial predators. Taking this to a greater extreme, the terror birds (and their relatives the bathornithids), eogruids, geranoidids, gastornithiforms, and dromornithids (all extinct) all evolved similar body shapes – long legs, long necks and big heads – but none of them were closely related. Furthermore, they also share traits of being giant, flightless birds with vestigial wings, long legs, and long necks with some of the ratites, although they are not related.

Origins of flightlessness

Divergences and losses of flight within ratite lineage occurred right after the K-Pg extinction event wiped out all non-avian dinosaurs and large vertebrates 66 million years ago. The immediate evacuation of niches following the mass extinction provided opportunities for Palaeognathes to distribute and occupy novel environments. New ecological influences selectively pressured different taxon to converge on flightless modes of existence by altering them morphologically and behaviorally. The successful acquisition and protection of a claimed territory selected for large size and cursoriality in Tertiary ancestors of ratites. Temperate rainforests dried out throughout the Miocene and transformed into semiarid deserts, causing habitats to be widely spread across the growingly disparate landmasses. Cursoriality was an economic means of traveling long distances to acquire food that was usually low-lying vegetation, more easily accessed by walking. Traces of these events are reflected in ratite distribution throughout semiarid grasslands and deserts today.

Gigantism and flightlessness are almost exclusively correlated. This is mostly observed in islands lacking predators and competition. However, ratites occupy environments that are mostly occupied by a diverse number of mammals. It is thought that they first originated through allopatric speciation caused by breakup of the supercontinent Gondwana. However recent evidence suggests this hypothesis first proposed by Joel Cracraft in 1974 is incorrect. Rather ratites arrived in their respective locations via a flighted ancestor and lost the ability to fly multiple times within the lineage.

Gigantism is not a requirement for flightlessness. The kiwi do not exhibit gigantism, along with tinamous, even though they coexisted with the moa and rheas that both exhibit gigantism. This could be the result of different ancestral flighted birds arrival or because of competitive exclusion. The first flightless bird to arrive in each environment utilized the large flightless herbivore or omnivore niche, forcing the later arrivals to remain smaller. In environments where flightless birds are not present, it is possible that after the K/T Boundary there were no niches for them to fill. They were pushed out by other herbivorous mammals.

New Zealand had more species of flightless birds (including the kiwi, several species of penguins, the takahe, the weka, the moa, and several other extinct species) than any other such location. One reason is that until the arrival of humans roughly a thousand years ago, there were no large land predators in New Zealand; the main predators of flightless birds were larger birds.

Independent evolution of flightlessness in Paelaeognathes

Ratites belong to the superorder Palaeognathae, which include the volant tinamou, and are believed to have evolved flightlessness independently multiple times within their own group. Some birds evolved flightlessness in response to the absence of predators, for example on oceanic islands. Incongruences between ratite phylogeny and Gondwana geological history indicate the presence of ratites in their current locations is the result of a secondary invasion by flying birds. It remains possible that the most recent common ancestor of ratites was flightless and the tinamou regained the ability to fly. However, it is believed that the loss of flight is an easier transition for birds rather than the loss and regain of flight, which has never been documented in avian history. Moreover, tinamou nesting within flightless ratites indicates ancestral ratites were volant and multiple losses of flight occurred independently throughout the lineage. This indicates that the distinctive flightless nature of ratites is the result of convergent evolution.

Morphological changes and energy conservation

Two key differences between flying and flightless birds are the smaller wing bones of flightless birds and the absent (or greatly reduced) keel on their breastbone. (The keel anchors muscles needed for wing movement.)

Adapting to a cursorial lifestyle causes two inverse morphological changes to occur in the skeleto-muscular system: the pectoral apparatus used to power flight is paedorphically reduced while peramorphosis leads to enlargement of the pelvic girdle for running. Repeated selection for cursorial traits across ratites suggests these adaptions comprise a more efficient use of energy in adulthood. The name "ratite" refers to their flat sternum that is distinct from the typical sternum of flighted birds because it lacks the keel. This structure is the place where flight muscles attach and thus allow for powered flight. However, ratite anatomy presents other primitive characters meant for flight, such as the fusion of wing elements, a cerebellar structure, the presence of a pygostyle for tail feathers, and an alula on the wing. These morphological traits suggest some affinities to volant groups. Palaeognathes were one of the first colonizers of novel niches and were free to increase in abundance until the population was limited by food and territory. A study looking at energy conservation and the evolution of flightlessness hypothesized intraspecific competition selected for a reduced individual energy expenditure, which is achieved by the loss of flight.

Some flightless varieties of island birds are closely related to flying varieties, implying flight is a significant biological cost. Flight is the most costly type of locomotion exemplified in the natural world. The energy expenditure required for flight increases proportionally with body size, which is often why flightlessness coincides with body mass. By reducing large pectoral muscles that require a significant amount of overall metabolic energy, ratites decrease their basal metabolic rate and conserve energy. A study looking at the basal rates of birds found a significant correlation between low basal rate and pectoral muscle mass in kiwis. On the contrary, flightless penguins exude an intermediate basal rate. This is likely because penguins have well-developed pectoral muscles for hunting and diving in the water. For ground feeding birds, a cursorial lifestyle is more economical and allows for easier access to dietary requirements. Flying birds have different wing and feather structures that make flying easier, while flightless birds' wing structures are well adapted to their environment and activities, such as diving in the ocean.

A number of bird species appear to be in the process of losing their powers of flight to various extents. These include the Zapata rail of Cuba, the Okinawa rail of Japan, and the Laysan duck of Hawaii. All of these birds show adaptations common to flightlessness, and evolved recently from fully flighted ancestors, but have not yet completely given up the ability to fly. They are, however, weak fliers and are incapable of traveling long distances by air.

Continued presence of wings in flightless birds

Although selection pressure for flight was largely absent, the wing structure has not been lost except in the New Zealand moas. Ostriches are the fastest running birds in the world and emus have been documented running 50 km/hr. At these high speeds, wings are necessary for balance and serving as a parachute apparatus to help the bird slow down. Wings are hypothesized to have played a role in sexual selection in early ancestral ratites and were thus maintained. This can be seen today in both the rheas and ostriches. These ratites utilize their wings extensively for courtship and displays to other males. Sexual selection also influences the maintenance of large body size, which discourages flight. The large size of ratites leads to greater access to mates and higher reproductive success. Ratites and tinamous are monogamous and mate only a limited number of times per year. High parental involvement denotes the necessity for choosing a reliable mate. In a climactically stable habitat providing year round food supply, a male's claimed territory signals to females the abundance of resources readily available to her and her offspring. Male size also indicates his protective abilities. Similar to the emperor penguin, male ratites incubate and protect their offspring anywhere between 85–92 days while females feed. They can go up to a week without eating and survive only off fat stores. The emu has been documented fasting as long as 56 days. If no continued pressures warrant the energy expenditure to maintain the structures of flight, selection will tend towards these other traits.

The only known species of flightless bird in which wings completely disappeared was the gigantic, herbivorous moa of New Zealand, hunted to extinction by humans by the 15th century. 

List of flightless birds

Many flightless birds are extinct; this list shows species that are either still extant, or became extinct in the Holocene (no more than 11,000 years ago). Extinct species are indicated with a dagger (†). A number of species suspected, but not confirmed to be flightless, are also included here. 

Ratites

Common ostrich

 

North Island brown kiwi

• Ostriches
  • Common ostrich, Struthio camelus
  • Somali ostrich, Struthio molybdophanes
  • Asian ostrich, Struthio asiaticus †
• Emus
  • Emu, Dromaius novaehollandiae
    • King Island emu, Dromaius novaehollandiae minor †
    • Kangaroo Island emu, Dromaius baudinianus †
    • Tasmanian emu, Dromaius novaehollandiae diemenensis †
• Cassowaries
  • Dwarf cassowary, Casuarius bennetti
  • Southern cassowary, Casuarius casuarius
  • Northern cassowary, Casuarius unappendiculatus
• Moa (Dinornithiformes) †, several species
• Elephant birds (Aepyornithiformes) †
• Kiwis
  • Southern brown kiwi, Apteryx australis
  • Great spotted kiwi, Apteryx haastii
  • North Island brown kiwi, Apteryx mantelli
  • Little spotted kiwi, Apteryx owenii
  • Okarito kiwi, Apteryx rowi
• Rheas
  • Greater rhea, Rhea americana
  • Darwin's rhea, Rhea pennata

Anseriformes (waterfowl)

Campbell teal

• Auckland Island teal, Anas aucklandica
• Campbell teal, Anas nesiotis
• Steamer ducks
  • Fuegian steamer duck, Tachyeres pteneres
  • Falkland steamer duck, Tachyeres brachypterus
  • Chubut steamer duck, Tachyeres leucocephalus
• Amsterdam wigeon, Anas marecula †
• Bermuda flightless duck, Anas pachyscelus †
• Finsch's duck, Chenonetta finschi †
• New Zealand merganser, Mergus australis †
• Turtle-jawed moa-nalo, Chelychelynechen quassus †
• Small-billed moa-nalo, Ptaiochen pau †
• O'ahu moa-nalo, Thambetochen xanion †
• Maui Nui large-billed moa-nalo, Thambetochen chauliodous †
• Nēnē-nui, Branta hylobadistes † (possibly flightless or very weak flier)
• Mihirung, Genyornis newtoni †
• California flightless sea-duck, Chendytes lawi †
• Kaua'i mole duck, Talpanas lippa †
• New Zealand geese, Cnemiornis †

Galliformes (game birds)

• New Caledonian giant scrubfowl, Sylviornis neocaledoniae †
• Noble megapode, Megavitornis altirostris †
• Viti Levu scrubfowl, Megapodius amissus †

Podicipediformes (grebes)

• Junin grebe, Podiceps taczanowskii
• Titicaca grebe, Rollandia microptera
• Atitlán grebe, Podilymbus gigas † (reportedly flightless)

Pelecaniformes (pelicans, cormorants and allies)

Flightless cormorant

• Flightless cormorant, Phalacrocorax harrisi
• Jamaican ibis, Xenicibis xymphithecus †
• Apteribis, A. glenos and A. brevis †

Sphenisciformes (penguins)

• King penguin, Aptenodytes patagonicus
• Emperor penguin, Aptenodytes forsteri
• Adélie penguin, Pygoscelis adeliae
• Chinstrap penguin, Pygoscelis antarctica
• Gentoo penguin, Pygoscelis papua
• Little blue penguin, Eudyptula minor
  • White-flippered penguin, Eudyptula minor albosignata
• Magellanic penguin, Spheniscus magellanicus
• Humboldt penguin, Spheniscus humboldti
• Galapagos penguin, Spheniscus mendiculus
• African penguin, Spheniscus demersus
• Yellow-eyed penguin, Megadyptes antipodes
• Waitaha penguin, Megadyptes waitaha †
• Fiordland penguin, Eudyptes pachyrhynchus
• Snares penguin, Eudyptes robustus
• Erect-crested penguin, Eudyptes sclateri
• Rockhopper penguin, Eudyptes chrysocome
• Royal penguin, Eudyptes schlegeli
• Macaroni penguin, Eudyptes chrysolophus
• Chatham penguin, Eudyptes sp. †

Gruiformes (cranes, rails, and coots)

Weka

• Cuban flightless crane, Grus cubensis †
• Red rail, Aphanapteryx bonasia †
• Rodrigues rail, Erythromachus leguati †
• Woodford's rail, Nesoclopeus woodfordi (most likely flightless)
• Bar-winged rail, Nesoclopeus poecilopterus † (probably flightless)
• Weka, Gallirallus australis
• New Caledonian rail, Gallirallus lafresnayanus (likely †)
• Lord Howe woodhen, Gallirallus sylvestris
• Calayan rail, Gallirallus calayanensis
• Pink-legged rail, Gallirallus insignis
• Guam rail, Gallirallus owstoni
• Roviana rail, Gallirallus rovianae (flightless, or almost so)^[22]
• Tahiti rail, Gallirallus pacificus †
• Dieffenbach's rail, Gallirallus dieffenbachii †
• Chatham rail, Cabalus modestus †
• Wake Island rail, Gallirallus wakensis †
• Snoring rail, Aramidopsis plateni
• Inaccessible Island rail, Atlantisia rogersi
• Laysan rail, Porzana palmeri †
• Hawaiian rail, Porzana sandwichensis †
• Kosrae crake, Porzana monasa †
• Ascension crake, Mundia elpenor †
• Henderson crake, Porzana atra
• Invisible rail, Habroptila wallacii
• New Guinea flightless rail, Megacrex inepta
• Lord Howe swamphen, Porphyrio albus †
• North Island takahē, Porphyrio mantelli †
• Takahē, Porphyrio hochstetteri
• Samoan woodhen, Gallinula pacifica
• Makira woodhen, Gallinula silvestris
• Tristan moorhen, Gallinula nesiotis †
• Gough Island moorhen, Gallinula comeri
• Tasmanian native hen,Tribonyx mortierii
• Giant coot, Fulica gigantea (adults only; immature birds can fly)
• Hawkins' rail, Diaphorapteryx hawkinsi †
• Snipe-rail, Capellirallus karamu †
• Adzebills, Aptornis otidiformis and A. defossor †

Charadriiformes (gulls, terns, auks)

Great auk

• Great auk, Pinguinus impennis †

Psittaciformes (parrots)

• Kakapo, Strigops habroptilus
• Heracles inexpectatus †^[24]

Columbiformes (pigeons, doves)

Dodo

• Dodo, Raphus cucullatus †
• Rodrigues solitaire, Pezophaps solitaria †
• Viti Levu giant pigeon, Natunaornis gigoura †
• Saint Helena dove, Dysmoropelia dekarchiskos †
• Henderson ground dove, Gallicolumba leonpascoi †

Strigiformes (owls)

• Cuban giant owl, Ornimegalonyx spp. † (possibly flightless)
• Cretan owl, Athene cretensis † (probably flightless)
• Andros Island barn owl, Tyto pollens † (possibly flightless)

Passeriformes (perching birds)

• Lyall's wren, Xenicus lyalli †
• Long-billed wren, Dendroscansor decurvirostris †
• North Island stout-legged wren, Pachyplichas jagmi †
• South Island stout-legged wren, Pachyplichas yaldwyni †
• Long-legged bunting, Emberiza alcoveri †

Feathered dinosaur

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Feathered_dinosaur

 

Fossil of Microraptor gui includes impressions of feathered wings (see arrows)

Since scientific research began on dinosaurs in the early 1800s, they were generally believed to be closely related to modern reptiles, such as lizards. The word "dinosaur" itself, coined in 1842 by paleontologist Richard Owen, comes from the Greek for "fearsome lizard". This view began to shift during the so-called dinosaur renaissance in scientific research in the late 1960s, and by the mid-1990s significant evidence had emerged that dinosaurs were much more closely related to birds, which descended directly from the theropod group of dinosaurs and are themselves a subgroup within the Dinosauria. 

Knowledge of the origin of feathers developed as new fossils were discovered throughout the 2000s and 2010s and as technology enabled scientists to study fossils more closely. Among non-avian dinosaurs, feathers or feather-like integument have been discovered in dozens of genera via direct and indirect fossil evidence. Although the vast majority of feather discoveries have been in coelurosaurian theropods, feather-like integument has also been discovered in at least three ornithischians, suggesting that feathers may have been present on the last common ancestor of the Ornithoscelida, a dinosaur group including both theropods and ornithischians. It is possible that feathers first developed in even earlier archosaurs, in light of the discovery of highly feather-like pycnofibers in pterosaurs. Crocodilians also possess beta keratin similar to those of birds, which suggests that they evolved from common ancestral genes.

History of research

 Early

The Berlin Archaeopteryx

Shortly after the 1859 publication of Charles Darwin's On the Origin of Species, British biologist Thomas Henry Huxley proposed that birds were descendants of dinosaurs. He compared the skeletal structure of Compsognathus, a small theropod dinosaur, and the 'first bird' Archaeopteryx lithographica (both of which were found in the Upper Jurassic Bavarian limestone of Solnhofen). He showed that, apart from its hands and feathers, Archaeopteryx was quite similar to Compsognathus. Thus Archaeopteryx represents a transitional fossil. In 1868 he published On the Animals which are most nearly intermediate between Birds and Reptiles, making the case. The first restoration of a feathered dinosaur was Thomas Henry Huxley's depiction in 1876 of a feathered Compsognathus to accompany a lecture on the evolution of birds he delivered in New York in which he speculated that the aforementioned dinosaur might have been in possession of feathers. The leading dinosaur expert of the time, Richard Owen, disagreed, claiming Archaeopteryx as the first bird outside dinosaur lineage. For the next century, claims that birds were dinosaur descendants faded, with more popular bird-ancestry hypotheses including 'crocodylomorph' and 'thecodont' ancestors, rather than dinosaurs or other archosaurs.

'Dinosaur renaissance'

In 1969, John Ostrom described Deinonychus antirrhopus, a theropod that he had discovered in Montana in 1964 and whose skeletal resemblance to birds seemed unmistakable. Ostrom became a leading proponent of the theory that birds are direct descendants of dinosaurs. Further comparisons of bird and dinosaur skeletons, as well as cladistic analysis strengthened the case for the link, particularly for a branch of theropods called maniraptors. Skeletal similarities include the neck, the pubis, the wrists (semi-lunate carpal), the 'arms' and pectoral girdle, the shoulder blade, the clavicle and the breast bone. In all, over a hundred distinct anatomical features are shared by birds and theropod dinosaurs. Other researchers drew on these shared features and other aspects of dinosaur biology and began to suggest that at least some theropod dinosaurs were feathered.

At the same time, paleoartists began to create modern restorations of highly active dinosaurs. In 1969, Robert T. Bakker drew a running Deinonychus. His student Gregory S. Paul depicted non-avian maniraptoran dinosaurs with feathers and protofeathers, starting in the late 1970s. In 1975, Eleanor M. Kish began to paint accurate images of dinosaurs, her Hypacrosaurus being the first one shown with its camouflage.

Before the discovery of feathered dinosaur fossils, the evidence was limited to Huxley and Ostrom's comparative anatomy. Some mainstream ornithologists, including Smithsonian Institution curator Storrs L. Olson, disputed the links, specifically citing the lack of fossil evidence for feathered dinosaurs. By the 1990s, however, most paleontologists considered birds to be surviving dinosaurs and referred to 'non-avian dinosaurs' (all extinct), to distinguish them from birds (Avialae).

Fossil discoveries

One of the earliest discoveries of possible feather impressions by non-avian dinosaurs is an ichnofossil (Fulicopus lyellii) of the 195-199 million year old Portland Formation in the northeastern United States. Gierlinski (1996, 1997, 1998) and Kondrat (2004) have interpreted traces between two footprints in this fossil as feather impressions from the belly of a squatting dilophosaurid. Although some reviewers have raised questions about the naming and interpretation of this fossil, if correct, this early Jurassic fossil is the oldest known evidence of feathers, almost 30 million years older than the next-oldest-known evidence.

Sinosauropteryx fossil, the first fossil of a definitively non-avialan dinosaur with feathers

 

After a century of hypotheses without conclusive evidence, well-preserved fossils of feathered dinosaurs were discovered during the 1990s, and more continue to be found. The fossils were preserved in a Lagerstätte—a sedimentary deposit exhibiting remarkable richness and completeness in its fossils—in Liaoning, China. The area had repeatedly been smothered in volcanic ash produced by eruptions in Inner Mongolia 124 million years ago, during the Early Cretaceous epoch. The fine-grained ash preserved the living organisms that it buried in fine detail. The area was teeming with life, with millions of leaves, angiosperms (the oldest known), insects, fish, frogs, salamanders, mammals, turtles, and lizards discovered to date.

The most important discoveries at Liaoning have been a host of feathered dinosaur fossils, with a steady stream of new finds filling in the picture of the dinosaur–bird connection and adding more to theories of the evolutionary development of feathers and flight. Turner et al. (2007) reported quill knobs from an ulna of Velociraptor mongoliensis, and these are strongly correlated with large and well-developed secondary feathers.

A nesting Citipati osmolskae specimen, at the AMNH

 

Behavioural evidence, in the form of an oviraptorosaur on its nest, showed another link with birds. Its forearms were folded, like those of a bird. Although no feathers were preserved, it is likely that these would have been present to insulate eggs and juveniles.

Not all of the Chinese fossil discoveries proved valid however. In 1999, a supposed fossil of an apparently feathered dinosaur named Archaeoraptor liaoningensis, found in Liaoning Province, northeastern China, turned out to be a forgery. Comparing the photograph of the specimen with another find, Chinese paleontologist Xu Xing came to the conclusion that it was composed of two portions of different fossil animals. His claim made National Geographic review their research and they too came to the same conclusion. The bottom portion of the "Archaeoraptor" composite came from a legitimate feathered dromaeosaurid now known as Microraptor, and the upper portion from a previously known primitive bird called Yanornis.

In 2011, samples of amber were discovered to contain preserved feathers from 75 to 80 million years ago during the Cretaceous era, with evidence that they were from both dinosaurs and birds. Initial analysis suggests that some of the feathers were used for insulation, and not flight. More complex feathers were revealed to have variations in coloration similar to modern birds, while simpler protofeathers were predominantly dark. Only 11 specimens are currently known. The specimens are too rare to be broken open to study their melanosomes, but there are plans for using non-destructive high-resolution X-ray imaging.

In 2016, the discovery was announced of a feathered dinosaur tail preserved in amber that is estimated to be 99 million years old. Lida Xing, a researcher from the China University of Geosciences in Beijing, found the specimen at an amber market in Myanmar. It is the first definitive discovery of dinosaur material in amber.

In March 2018, scientists reported that Archaeopteryx was likely capable of flight, but in a manner substantially different from that of modern birds.

Current knowledge

Non-avian dinosaur species preserved with evidence of feathers

Fossil of Sinornithosaurus millenii, the first evidence of feathers in dromaeosaurids

 

Cast of a Caudipteryx fossil with feather impressions and stomach content

 

Fossil cast of a Sinornithosaurus millenii

 

Jinfengopteryx elegans fossil

Several non-avian dinosaurs are now known to have been feathered. Direct evidence of feathers exists for several species. In all examples, the evidence described consists of feather impressions, except those genera inferred to have had feathers based on skeletal or chemical evidence, such as the presence of quill knobs (the anchor points for wing feathers on the forelimb) or a pygostyle (the fused vertebrae at the tail tip which often supports large feathers).

Primitive feather types

Integumentary structures that gave rise to the feathers of birds are seen in the dorsal spines of reptiles and fish. A similar stage in their evolution to the complex coats of birds and mammals can be observed in living reptiles such as iguanas and Gonocephalus agamids. Feather structures are thought to have proceeded from simple hollow filaments through several stages of increasing complexity, ending with the large, deeply rooted feathers with strong pens (rachis), barbs and barbules that birds display today.

According to Prum's (1999) proposed model, at stage I, the follicle originates with a cylindrical epidermal depression around the base of the feather papilla. The first feather resulted when undifferentiated tubular follicle collar developed out of the old keratinocytes being pushed out. At stage II, the inner, basilar layer of the follicle collar differentiated into longitudinal barb ridges with unbranched keratin filaments, while the thin peripheral layer of the collar became the deciduous sheath, forming a tuft of unbranched barbs with a basal calamus. Stage III consists of two developmental novelties, IIIa and IIIb, as either could have occurred first. Stage IIIa involves helical displacement of barb ridges arising within the collar. The barb ridges on the anterior midline of the follicle fuse together, forming the rachis. The creation of a posterior barb locus follows, giving an indeterminate number of barbs. This resulted in a feather with a symmetrical, primarily branched structure with a rachis and unbranched barbs. In stage IIIb, barbules paired within the peripheral barbule plates of the barb ridges, create branched barbs with rami and barbules. This resulting feather is one with a tuft of branched barbs without a rachis. At stage IV, differentiated distal and proximal barbules produce a closed, pennaceous vane. A closed vane develops when pennulae on the distal barbules form a hooked shape to attach to the simpler proximal barbules of the adjacent barb. Stage V developmental novelties gave rise to additional structural diversity in the closed pennaceous feather. Here, asymmetrical flight feathers, bipinnate plumulaceous feathers, filoplumes, powder down, and bristles evolved.

Some evidence suggests that the original function of simple feathers was insulation. In particular, preserved patches of skin in large, derived, tyrannosauroids show scutes, while those in smaller, more primitive, forms show feathers. This may indicate that the larger forms had complex skins, with both scutes and filaments, or that tyrannosauroids may be like rhinos and elephants, having filaments at birth and then losing them as they developed to maturity. An adult Tyrannosaurus rex weighed about as much as an African elephant. If large tyrannosauroids were endotherms, they would have needed to radiate heat efficiently. However, due to the different structural properties of feathers compared to fur, as well as a larger surface area per cubic square meter, it is extremely unlikely even the largest theropods would suffer overheating issues from an extensive feather coat.

There is an increasing body of evidence that supports the display hypothesis, which states that early feathers were colored and increased reproductive success. Coloration could have provided the original adaptation of feathers, implying that all later functions of feathers, such as thermoregulation and flight, were co-opted. This hypothesis has been supported by the discovery of pigmented feathers in multiple species. Supporting the display hypothesis is the fact that fossil feathers have been observed in a ground-dwelling herbivorous dinosaur clade, making it unlikely that feathers functioned as predatory tools or as a means of flight. Additionally, some specimens have iridescent feathers. Pigmented and iridescent feathers may have provided greater attractiveness to mates, providing enhanced reproductive success when compared to non-colored feathers. Current research shows that it is plausible that theropods would have had the visual acuity necessary to see the displays. In a study by Stevens (2006), the binocular field of view for Velociraptor has been estimated to be 55 to 60 degrees, which is about that of modern owls. Visual acuity for Tyrannosaurus has been predicted to be anywhere from about that of humans to 13 times that of humans. However, as both Velociraptor and Tyrannosaurus have a rather extended evolutionary relationship with the more basal theropods, it is unclear how much of this visual acuity data can be extrapolated.

The idea that precursors of feathers appeared before they were co-opted for insulation is already stated in Gould and Vrba, 1982. The original benefit might have been metabolic. Feathers are largely made of the keratin protein complex, which has disulfide bonds between amino acids that give it stability and elasticity. The metabolism of amino acids containing sulfur can be toxic; however, if the sulfur amino acids are not catabolized at the final products of urea or uric acid but used for the synthesis of keratin instead, the release of hydrogen sulfide is extremely reduced or avoided. For an organism whose metabolism works at high internal temperatures of 40 °C or greater, it can be extremely important to prevent the excess production of hydrogen sulfide. This hypothesis could be consistent with the need for high metabolic rate of theropod dinosaurs.

It is not known with certainty at what point in archosaur phylogeny the earliest simple "protofeathers" arose, or whether they arose once or independently multiple times. Filamentous structures are clearly present in pterosaurs, and long, hollow quills have been reported in specimens of the ornithischian dinosaurs Psittacosaurus and Tianyulong. In 2009, Xu et al. noted that the hollow, unbranched, stiff integumentary structures found on a specimen of Beipiaosaurus were strikingly similar to the integumentary structures of Psittacosaurus and pterosaurs. They suggested that all of these structures may have been inherited from a common ancestor much earlier in the evolution of archosaurs, possibly in an ornithodire from the Middle Triassic or earlier. More recently, findings in Russia of the basal neornithischian Kulindadromeus report that although the lower leg and tail seemed to be scaled, "varied integumentary structures were found directly associated with skeletal elements, supporting the hypothesis that simple filamentous feathers, as well as compound feather-like structures comparable to those in theropods, were widespread amongst the whole dinosaur clade."

Display feathers are also known from dinosaurs that are very primitive members of the bird lineage, or Avialae. The most primitive example is Epidexipteryx, which had a short tail with extremely long, ribbon-like feathers. Oddly enough, the fossil does not preserve wing feathers, suggesting that Epidexipteryx was either secondarily flightless, or that display feathers evolved before flight feathers in the bird lineage. Plumaceous feathers are found in nearly all lineages of Theropoda common in the northern hemisphere, and pennaceous feathers are attested as far down the tree as the Ornithomimosauria. The fact that only adult Ornithomimus had wing-like structures suggests that pennaceous feathers evolved for mating displays.

Phylogeny and the inference of feathers in other dinosaurs

Cladogram showing distribution of feathers in Dinosauria, as of 2015

 

Fossil feather impressions are extremely rare and they require exceptional preservation conditions to form. Therefore, only a few non-avian feathered dinosaur genera have been identified. All fossil feather specimens have been found to show certain similarities. Due to these similarities and through developmental research, many scientists believe that feathers have only evolved once in dinosaurs. Feathers would then have been passed down to all later, more derived species, unless some lineages lost feathers secondarily. If a dinosaur falls at a point on an evolutionary tree within the known feather-bearing lineages, then its ancestors had feathers, and it is quite possible that it did as well. This technique, called phylogenetic bracketing, can also be used to infer the type of feathers a species may have had, since the developmental history of feathers is now reasonably well-known. All feathered species had filamentaceous or plumaceous (downy) feathers, with pennaceous feathers found among the more bird-like groups. The following cladogram is adapted from Godefroit et al., 2013.

Phylogenetic bracketing can also be used to evidence the lack of feathered integument by inference. For example, the presence of scaly integument in a specific clade would be a strong indicator that members in the clade would share similar integument, as independent evolution of feathers multiple times is unlikely, regardless if fossil evidence is present for all genera within the clade.

Grey denotes a clade that is not known to contain any feathered specimen at the time of writing, some of which have fossil evidence of scales. The presence or lack of feathered specimens in a given clade does not confirm that all members in a clade have the specified integument, unless corroborated with representative fossil evidence within clade members. 

 

Solar still

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Solar_still

Solar still built into a pit in the ground

 

"Watercone" solar still

 

A solar still distills water with substances dissolved in it by using the heat of the Sun to evaporate water so that it may be cooled and collected, thereby purifying it. They are used in areas where drinking water is unavailable, so that clean water is obtained from dirty water or from plants by exposing them to sunlight.

There are many types of solar still, including large scale concentrated solar stills and condensation traps (better known as moisture traps amongst survivalists). In a solar still, impure water is contained outside the collector, where it is evaporated by sunlight shining through clear plastic or glass. The pure water vapour condenses on the cool inside surface and drips down, where it is collected and removed.

Distillation replicates the way nature makes rain. The sun's energy heats water to the point of evaporation. As the water evaporates, water vapour rises, condensing into water again as it cools and can then be collected. This process leaves behind impurities, such as salts and heavy metals, and eliminates microbiological organisms. The end result is pure distilled drinking water. 

History

Condensation traps have been in use since the pre-Incan peoples inhabited the Andes.

Today, a method for gathering water in moisture traps is still taught within the Argentinian Army for use by specialist units expected to conduct extended patrols of more than a week's duration in the arid border areas of the Andes.

Uses

Solar stills are used in cases where rain, piped, or well water is impractical, such as in remote homes or during power outages. In subtropical hurricane target areas that can lose power for days, solar distillation can provide an alternative source of clean water. 

Solar Well

 

Methods

Several methods of trapping condensation exist:

First method

This method was first used by the peoples of the Andes. A pit is dug into the earth, at the bottom of which is placed the receptacle that will be used to catch the condensed water. Small branches are placed with one of their ends inside the receptacle and their other ends up over the edge of the pit, forming a funnel to direct the condensed water into the receptacle. A lid is then built over this funnel, using more small branches, leaves, grasses, etc. The completed trap is left overnight, and moisture can be collected from the receptacle in the morning.

This method relies on the formation of dew or frost on the receptacle, funnel, and lid. Forming dew collects on and runs down the outside of the funnel and into the receptacle. This water would typically evaporate with the morning sun and thus vanish, but the lid traps the evaporating water and raises the humidity within the trap, reducing the amount of water that is lost. The shade produced by the lid also reduces the temperature within the trap, which further reduces the rate of water loss to evaporation.

Modern method

Today, with the advent of plastic sheeting, the moisture trap has become more efficient. 

The method is very similar to that described above, but a single sheet of plastic is used instead of branches and leaves. The greater efficiency of this type of trap arises from the waterproof nature of the plastic, which doesn't let any water vapour pass through it (some water vapour escapes through the leaves and branches of the first method). This efficiency requires a certain amount of diligence of the part of the user, in that the plastic sheet must be firmly attached to the ground on all sides; this is often accomplished by using stones to weight the sheet down and/or covering the edges of the plastic sheet with earth (such as that dug out to make the hole in which the trap sits). Weighting the centre of the plastic sheet down with a stone forms the funnel via which the condensed water will run into the receptacle.

Transpiration method

Water can be obtained by placing clear plastic bags over the leafy branch of a non-poisonous tree and tightly closing the bag's open end around the branch. Any holes in the bag must be sealed to prevent the loss of water vapour.

During photosynthesis plants lose water through a process called transpiration. A clear plastic bag sealed around a branch allows photosynthesis to continue, but traps the evaporating water causing the vapour pressure of water to rise to a point where it begins to condense on the surface of the plastic bag. Gravity then causes the water to run to the lowest part of the bag. Water is collected by tapping the bag and then resealing it. The leaves will continue to produce water as the roots draw it from the ground and photosynthesis occurs.

The vapour pressure of water in the sealed bag can rise so high that the leaves can no longer transpire, consequently when using this method, the water should be drained off every two hours and stored. Tests indicate that if this is not done the leaves stop producing water. 

If there are no large trees in the area, clumps of grass or small bushes can be placed inside the bag. If this is done the foliage will have to be replaced at regular intervals when water production is reduced, particularly if the foliage must be uprooted to place it in the bag.

Efficiency is greatest when the bag receives maximum sunshine at all times. Exposed roots are tested for water content. Soft, pulpy roots will yield the greatest amount of liquid for the least amount of effort.

Condensation trap efficiency

Condensation traps are not in themselves a sustainable source of water; they are sources for extending or supplementing existing water sources or supplies, and should not be relied on to provide a person's daily requirement for water, since a trap measuring 400 mm (16 in) in diameter by 300 mm (12 in) deep will only yield around 100 to 150 mL (3.4 to 5.1 US fl oz) per day. 

One method to increase the water output is to urinate into the pit before placing the receptacle in. This increases the moisture content of the earth, reducing the amount of water vapour that the earth can subsequently absorb. 

Materials

A simple basin-type solar still can be constructed with 2–4 stones, plastic film or transparent glass, a central weight to make a point and a container for the condensate. A cubic hole in moist ground is created of about 300 mm (12 in) on each side. Into the centre of this hole, a collection container is placed. Then a sheet of plastic film is stretched over the hole. Stills can also be made from water bottles or plastic bags.

Variations

Transpiration bag

An alternative method of the solar still is called the transpiration bag. The bag is a simple plastic bag and it folds over a stemmed plant with a corner pointing down to allow the condensate to pool. From there a person can remove the water by taking the bag off and pouring the water out or one can make a tiny incision into the corner to drip water into a cup. Its advantage over the basin type solar still mentioned before is that it only requires a bag like one can get at the grocery store. It doesn't need to be completely transparent. A disadvantage of the transpiration bag is the requirement for a plant in direct sunlight or heat to take the condensate.

In a study performed in 2009, variations to the angle of plastic and increasing the internal temperature of the hole versus the outside temperature made for better water production. Other methods used included using a brine to absorb water from and adding dyes to the brine to change the amount of solar radiation absorbed into the system. During the adjusted tilt angle experiment, the different angles used by the different researchers created different results and it was difficult for any of them to get a definite answer. In the graph, a bell curve is observed with the maximum water output being at 30 degrees angle adjustment. Each brine depth created a different amount of water and it is noted on the graph that about 25 millimetres (1 in) is optimal with a decreasing trend if more is used.

Wick still

This image shows how a wick basin solar still works.

 

The “wick” type solar still is a glass-topped box constructed and held at angle to allow sunlight in. Salt water poured in from the top is heated by sunlight, evaporating the water. It condenses on the underside of the glass and drips to the bottom. A pool of brine in the still is attached to the wicks which separates the water into banks to increase surface area for heating. The distilled water comes out of the bottom and, depending on the quality of construction, most of the salt has been purged from the water. The more wicks, the more heat can be transferred to the salt water and more product can be made. A plastic net can also catch salt water before it falls into the container and give it more time to heat up and separate into brine and water. The wick type solar still is made vapour-tight, as in the vapour does not escape to the atmosphere. To aid in absorbing more heat, some wicks are blackened to take in more heat. Glass's absorption of heat is negligible compared to plastic at higher temperatures. A problem, depending on application, with glass is that it is not flexible if the solar still is not a standard shape.

Practical considerations

The pit still may be inefficient as a survival still, requiring too much construction effort for the water produced. In desert environments water needs can exceed 3.8 litres (1 US gal) per day for a person at rest, while still production may average 240 millilitres (8 US fl oz) per day. Even with tools, digging a hole requires energy and makes a person lose water through perspiration; this means that even several days of water collection may not be equal to the water lost in its construction.

Seawater still

In 1952, the United States military developed a portable solar still for pilots stranded on the ocean, which comprises an inflatable 610-millimetre (24 in) plastic ball that floats on the ocean, with a flexible tube coming out the side. A separate plastic bag hangs from attachment points on the outer bag. Seawater is poured into the inner bag from an opening in the ball's neck. Fresh water is taken out by the pilot using the side tube that leads to bottom of the inflatable ball. It was stated in magazine articles that on a good day 2.4 litres (2.5 US qt) of fresh water could be produced. On an overcast day, 1.4 litres (1.5 US qt) was produced. Similar sea water stills are included in some life raft survival kits, though manual reverse osmosis desalinators have mostly replaced them.

Distilling urine

Using a condensation trap to distill urine will remove the urea and salt, providing one with drinkable water as a result.