Australian megafauna

From Wikipedia, the free encyclopedia

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

 

Marsupial lion skeleton in Naracoorte Caves, South Australia.

Australian megafauna comprises a number of large animal species in Australia, often defined as species with body mass estimates of greater than 45 kg (100 lb) or equal to or greater than 130% of the body mass of their closest living relatives. Many of these species became extinct during the Pleistocene (16,100±100 – 50,000 years BC).

There are similarities between prehistoric Australian megafauna and some mythical creatures from the Aboriginal dreamtime.

Causes of extinction

The cause of the extinction is an active, contentious and factionalised field of research where politics and ideology often takes precedence over scientific evidence, especially when it comes to the possible implications regarding Aboriginal people (who appear to be responsible for the extinctions). It is hypothesised that with the arrival of early Australian Aboriginals (around 70,000~65,000 years ago), hunting and the use of fire to manage their environment may have contributed to the extinction of the megafauna. Increased aridity during peak glaciation (about 18,000 years ago) may have also contributed, but most of the megafauna were already extinct by this time.

New evidence based on accurate optically stimulated luminescence and uranium-thorium dating of megafaunal remains suggests that humans were the ultimate cause of the extinction of megafauna in Australia. The dates derived show that all forms of megafauna on the Australian mainland became extinct in the same rapid timeframe—approximately 46,000 years ago—the period when the earliest humans first arrived in Australia (around 70,000~65,000 years ago). Analysis of oxygen and carbon isotopes from teeth of megafauna indicate the regional climates at the time of extinction were similar to arid regional climates of today and that the megafauna were well adapted to arid climates. The dates derived have been interpreted as suggesting that the main mechanism for extinction was human burning of a landscape that was then much less fire-adapted; oxygen and carbon isotopes of teeth indicate sudden, drastic, non-climate-related changes in vegetation and in the diet of surviving marsupial species. However, early Australian Aborigines appear to have rapidly eliminated the megafauna of Tasmania about 41,000 years ago (following formation of a land bridge to Australia about 43,000 years ago as Ice Age sea levels declined) without using fire to modify the environment there, implying that at least in this case hunting was the most important factor. It has also been suggested that the vegetational changes that occurred on the mainland were a consequence, rather than a cause, of the elimination of the megafauna. This idea is supported by sediment cores from Lynch's Crater in Queensland, which indicate that fire increased in the local ecosystem about a century after the disappearance of megafaunal browsers, leading to a subsequent transition to fire-tolerant sclerophyll vegetation.

Chemical analysis of fragments of eggshells of Genyornis newtoni, a flightless bird that became extinct in Australia, from over 200 sites, revealed scorch marks consistent with cooking in human-made fires, presumably the first direct evidence of human contribution to the extinction of a species of the Australian megafauna. This was later contested by another study that noted the too small dimensions (126 x 97 mm, roughly like the emu eggs, while the moa eggs were about 240 mm) for the Genyornis supposed eggs, and rather, attributed them to another extinct, but much smaller bird. The real time that saw Genyornis vanish is still an open question, but this was believed as one of the best documented megafauna extinction in Australia.

"Imperceptive overkill"; a scenario where anthropogenic pressures take place; slowly and gradually wiping the megafauna out; has been suggested.

On the other hand, there is also compelling evidence to suggest that (contrary to other conclusions) the megafauna lived alongside humans for several thousand years. The question of; if (and how) the megafauna died before the arrival of humans is still debated; with some authors maintaining that only a minority of such fauna remained by the time the first humans settled on the mainland. One of the most important advocates of human role, Tim Flannery, author of the book Future Eaters, was also heavily criticized for his conclusions.

Living Australian megafauna

The term "megafauna" is usually applied to large animals (over 100 kg (220 lb)). In Australia, however, megafauna were never as large as those found on other continents, and so a more lenient criterion of over 40 kg (88 lb) is often applied.

Mammals

Red kangaroo

• The red kangaroo (Macropus rufus) grows up to 1.8 m (6 ft) tall and weighs up to 85 kg (187 lb). Females grow up to 1.1 m (3 ft 7 in) tall and weigh up to 35 kg (77 lb). Tails on both males and females can be up to 1 m (3 ft 3 in) long.
• Eastern grey kangaroos (Macropus giganteus). Although a male typically weighs around 66 kg (145 lb) and stand almost 2 m (6 ft 7 in) tall, the scientific name Macropus giganteus (gigantic large-foot) is misleading, as the red kangaroo living in the semi-arid inland is larger.
• The antilopine kangaroo (Macropus antilopinus), sometimes called the antilopine wallaroo or the antilopine wallaby, is a species of macropod found in northern Australia at Cape York Peninsula in Queensland, the Top End of the Northern Territory, and the Kimberley region of Western Australia. can weigh as much as 47 kg (104 lb) and grow over 1 m (3 ft 3 in) long.
• Common wombats (Vombatus ursinus) can reach 40 kg (88 lb). They thrive in Eastern Australia and Tasmania, preferring temperate forests and highland regions.

Birds

Cassowary

• The emu (Dromaius novaehollandiae)
• The southern cassowary (Casuarius casuarius)

Reptiles

Perentie

• Goanna, being predatory lizards, are often quite large or bulky, with sharp teeth and claws. The largest goanna is the perentie (Varanus giganteus), which can grow over 2 m (6 ft 7 in) in length. Not all goannas are gargantuan though: pygmy goannas may be smaller than a man's arm.
• A healthy adult male saltwater crocodile (Crocodylus porosus) is typically 4.8–7 m (15 ft 9 in–23 ft 0 in) long and weighs around 770 kg (1,700 lb)), with many being much larger than this. The female is much smaller, with typical body lengths of 2.5–3 m (8 ft 2 in–9 ft 10 in). An 8.5 m (28 ft) saltwater crocodile was reportedly shot on the Norman River of Queensland in 1957; a cast was made of it and is on display as a popular tourist attraction. However, due to the lack of solid evidence (other than the plaster) and the length of time since the crocodile was caught, it is not considered "official".
• Freshwater crocodile (Crocodylus johnsoni) The freshwater crocodile is a relatively small crocodilian. Males can grow to 2.3–3 m (7 ft 7 in–9 ft 10 in) long, while females reach a maximum size of 2.1 m (6 ft 11 in). Males commonly weigh around 40 kg (88 lb), with large specimens up to 53 kg (120 lb) or more, against the female weight of 20 kg (44 lb). In areas such as Lake Argyle and Katherine Gorge there exist a handful of confirmed 4 m (13 ft) individuals.

Extinct Australian megafauna

The following is an incomplete list of extinct Australian megafauna (monotremes, marsupials, birds and reptiles) in the format:

• Latin name, (common name, period alive), and a brief description.

Monotremes

Monotremes are arranged by size with the largest at the top.

• Zaglossus hacketti was a sheep-sized echidna uncovered in Mammoth Cave in Western Australia, and is the largest monotreme so far uncovered.
• Obdurodon dicksoni was a platypus up to 60 cm (2 ft) in total length, fossils of which were found at Riversleigh.
• Megalibgwilia ramsayi was a large, long-beaked echidna with powerful forelimbs for digging.

Marsupials

Marsupials are arranged by size, with the largest at the top.

The diprotodon was a hippopotamus-sized marsupial, most closely related to the wombat.

 

1,000–3,000 kilograms (2,200–6,610 lb)

• Diprotodon optatum is not only the largest-known species of diprotodontid, but also the largest-known marsupial to ever exist. Approximately 3 m (10 ft) long and 2 m (7 ft) high at the shoulder and weighing up to 2,780 kg (6,130 lb), it resembled a giant wombat. It is the only marsupial known, living or extinct, to have conducted seasonal migration.^[24]
• Zygomaturus trilobus was a smaller (bullock-sized, about 2 m (7 ft) long by 1 m (3 ft) high) diprotodontid that may have had a short trunk. It appears to have lived in wetlands, using two fork-like incisors to shovel up reeds and sedges for food.
• Palorchestes azael (the marsupial tapir) was a diprotodontoid similar in size to Zygomaturus. It had long claws and a longish trunk. It lived during the Pleistocene.^[3]
• Nototherium was a diprotodontoid relative of the larger Diprotodon.

100–1,000 kilograms (220–2,200 lb)

• Euowenia grata
• Euryzygoma dunense
• Phascolonus gigas
• Ramsayia magna
• Procoptodon goliah (the giant short-faced kangaroo) is the largest-known kangaroo to have ever lived. It grew 2–3 metres (7–10 feet) tall, and weighed up to 230 kg (510 lb).
• Procoptodon rapha, P. pusio and P. texasensis
• Protemnodon a form of giant wallaby with 4 species.^[25]
• Palorchestes parvus
• Macropus pearsoni and M. ferragus
• Thylacoleo carnifex (the marsupial lion) is the largest-known carnivorous mammal to have ever lived in prehistoric Australia, and was of comparable size to female placental-mammal lions and tigers

10–100 kilograms (22–220 lb)

Simosthenurus pales

Sthenurus tindalei and S. atlas

Phascolarctos stirtoni was a koala similar to the modern form, but one third larger.

Phascolomys medius

Lasiorhinus angustidens

Thylacinus cynocephalus (the thylacine or Tasmanian tiger)

Congruus congruus a wallaby from Naracoorte.

Troposodon minor

Sthenurus oreas

Simosthenurus occidentalis (another sthenurine) was about as tall as a modern eastern grey kangaroo, but much more robust. It is one of the nine species of leaf-eating kangaroos identified in fossils found in the Naracoorte Caves National Park.

• Zygomaturus trilobus
• Simothenurus brownei
• Propleopus oscillans (the carnivorous kangaroo), from the Pliocene and Pleistocene epochs, was a large (about 70 kg (150 lb) rat-kangaroo with large shearing and stout grinding teeth that indicate it may have been an opportunistic carnivore able to eat insects, vertebrates (possibly carrion), fruits, and soft leaves. Grew to about 1.5–3 m (5–10 ft) in height.
• Simothenurus maddocki
• Sthenurus andersoni
• Thylacoleo carnifex, (the marsupial lion), was the size of a leopard, and had a cat-like skull with large slicing pre-molars. It had a retractable thumb-claw and massive forelimbs. It was almost certainly carnivorous and a tree-dweller.
• Vombatus hacketti
• Macropus thor
• Macropus piltonensis
• Macropus rama
• Simothenurus gilli
• Warrendja wakefieldi a wombat from Naracoorte.
• Sarcophilus harrisii laniarius was a large form of the Tasmanian devil.
• Thylacinus megiriani

Birds

Dromornis stirtoni

• Family Dromornithidae: this group of birds was more closely related to fowl than modern ratites.
  • Dromornis stirtoni, (Stirton's thunder bird, or "The Demon Duck of Doom") was a flightless bird 3 m (10 ft) tall that weighed about 500 kg (1,100 lb). It is one of the largest birds so far discovered. It inhabited subtropical open woodlands and may have been carnivorous. It was heavier than the moa and taller than Aepyornis.
  • Bullockornis planei was another huge member of the Dromornithidae. It was up to 2.5 m (8 ft) tall and weighed up to 250 kg (550 lb); it was probably carnivorous.
  • Genyornis newtoni (the mihirung) was related to Dromornis, and was about the height of an ostrich. It was the last survivor of the Dromornithidae. It had a large lower jaw and was probably omnivorous.
• Leipoa gallinacea (formerly Progura) was a giant malleefowl.

Reptiles

Reconstructed skeleton of the giant extinct Varanus priscus

• Varanus priscus (formerly Megalania prisca) was a giant, carnivorous goanna that might have grown to as long as 7 m (23 ft), and weighed up to 1,940 kg (4,280 lb) (Molnar, 2004). Giant goannas and humans overlapped in time in Pleistocene Australia, but there is no evidence that they directly encountered each other.^[26]
• Wonambi naracoortensis was a non-venomous snake of 5–6 m (16–20 ft) in length. It was an ambush predator living at waterholes located in natural sun traps and killed its prey by constriction.
• Quinkana sp., was a terrestrial crocodile that grew from 5 m (16 ft) to possibly 7 m (23 ft) in length. It had long legs positioned underneath its body, and chased down mammals, birds and other reptiles for food. Its teeth were blade-like for cutting rather than pointed for gripping as with water dwelling crocodiles. It belonged to the mekosuchine subfamily (all now extinct). It was discovered at Bluff Downs in Queensland.
• Liasis dubudingala, lived during the Pliocene epoch, grew up to 10 m (33 ft) long, and is the largest Australian snake known. It hunted mammals, birds and reptiles in riparian woodlands. It is most similar to the extant olive python (Liasis olivacea).
• Meiolania was a genus of huge terrestrial cryptodire turtle measuring 2.5 m (8 ft) in length, with a horned head and spiked tail.

Extinct megafauna contemporaneous with Aboriginal Australians

Monsters and large animals in Dreamtime stories have been associated with extinct megafauna.

The association was made at least as early as 1845, with colonists writing that Aboriginal people identified Diprotodon bones as belonging to bunyips, and Thomas Worsnop concluding that the fear of bunyip attacks at watering holes remembered a time when Diprotodon lived in marshes.

In the early 1900s, John Walter Gregory outlined the Kadimakara (or Kuddimurka or Kadimerkera) story of the Diyari (similar stories being told by nearby peoples), which describes the deserts of Central Australia as having once been "fertile, well-watered plains" with giant gum-trees, and almost solid cloud cover overhead. The trees created a roof of vegetation in which lived the strange monsters called Kadimakara—which sometimes came to the ground to eat. One time, the gum-trees were destroyed, forcing the Kadimakara to remain on the earth, particularly Lake Eyre and Kalamurina, until they died.

In times of drought and flood, the Diyari performed corroborees (including dances and blood sacrifices) at the bones of the Kadimakara to appease them and request that they intercede with spirits of rain and cloud. Sites of Kadimakara bones identified by Aboriginal people corresponded with megafauna fossil sites, and an Aboriginal guide identified a Diprotodon jaw as belonging to the Kadimakara.

Gregory speculated that the story could be a remnant from when the Diyari lived elsewhere, or when the geographical conditions of Central Australia were different. The latter possibility would indicate Aboriginal coexistence with megafauna, with Gregory saying:

If, therefore, the geologist can determine whether the bones of the extinct monsters of Lake Eyre correspond to those described in the aboriginal traditions, he can throw light on several interesting problems. If the legends attribute to the extinct animals characters which they possessed, but which the natives could not have inferred from the bones, then the legends are of local origin. They would prove that man inhabited Central Australia, at the same time as the mighty diprotodon and the extinct, giant kangaroos. If, on the other hand, there is no such correspondence between the legends and the fossils, then we must regard the traditions as due to the habit of migratory peoples, of localising in new homes the incidents recorded in their folklore.

— John Walter Gregory, Dead Heart of Australia

After examining fossils, Gregory concluded that the story was a combination of the two factors but that the environment of Lake Eyre had probably not changed much since Aboriginal habitation. He concluded that while some references to Kadimakara were probably memories of the crocodiles once found in Lake Eyre, others that describe a "big, heavy land animal, with a single horn on its forehead" were probably references to Diprotodon.

Geologist Michael Welland describes from across Australia Dreamtime "tales of giant creatures that roamed the lush landscape until aridity came and they finally perished in the desiccated marshes of Kati Thanda–Lake Eyre", giving as examples the Kadimakara of Lake Eye as well as continent-wide stories of the Rainbow Serpent, which he says corresponds with Wonambi naracoortensis.

Journalist Peter Hancock speculates in The Crococile That Wasn't that a Dreamtime story from the Perth area could be a memory of Megalania.

Rock art in the Kimberley appears to depict a marsupial lion and a marsupial tapir, as does Arnhem land art. Arnhem art also appears to depict Genyornis, a bird that is believed to have gone extinct 40,000 years ago.

An Early Triassic archosauromorph found in Queensland, Kadimakara australiensis, is named after the Kadimakara.

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.