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18.12.2015 19:00 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part2 Birds Ch.4 Penguins
Автор: valentint Категория: Забавление   
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Penguins (Sphenisciformes)
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1. Palaeeudyptes 2. Pachydyptes 3. Platydyptes 4. Anthropornis 5. Waimanu
Penguins are flightless, marine birds belonging to the order
Sphenisciformes in the family Spheniscidae. They have existed since the beginning of the Cenozoic with roots possibly dating back to the late Cretaceous, and they appear to have always been restricted to the Southern Hemisphere; both modern penguins and their extinct relatives are distributed along the coasts of decades with numerous new taxa having been described during that time, with argueably the most interesting discoveries coming out of New Zealand. Although the penguin lineage is believed to have split away from other birds as early as the late Cretaceous (71mya), the earliest-known and most basal penguins date back to the early to middle Paleocene (62 to 58mya) and belong to the genus Waimanu from New Zealand. The South American genus Perudyptes and a slightly older, unnamed taxon, demonstrate that penguins had expanded their range to encompass the entire southern Pacific Ocean by the middle Eocene and were probably present throughout the Atlantic Ocean as well. There are four accepted penguin subfamilies (discussed below), only one of which is still alive today.
The Palaeeudyptinae, or “giant penguins”, are the most well-studied of the extinct penguin subfamilies. The earliest known member, Crossvallia unienwillia, lived during the late Paleocene (59.2–56mya) in what is now Antarctica, and therefore would have coexisted with basal penguins like Waimanu. Antarctica, Australia, New Zealand, sub-Saharan Africa, and South America.
The Paleogene fossil record of penguins has been intensively studied in the last few The group persisted throughout the Paleogene and until the late Oligocene, and potentially even lasting until the middle Miocene if the tentatively placed Anthropodyptes proves to be a true member. Palaeeudyptines differ from modern penguins in a number of aspects. For example, the forelimb had not yet developed into a rigid flipper and would have retained a degree of flexibility. The beak also differs from those of modern penguins in being relatively long and spear-like, similar to that of a heron.
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By far the most frequent topic addressed when discussing members of Palaeeudyptinae, is body size. True to their colloquial name, these early Cenozoic penguins were quite large by modern standards; the 20 species of modern penguin range in size from the 40cm tall and 1kg Little Blue Penguin (Eudyptula minor), up to the 110cm tall and 35kg Emperor Penguin (Aptenodytes forsteri). The early palaeeudyptine Crossvallia unienwillia was only slightly larger than an Emperor Penguin with much larger penguins, with body lengths of over 130cm, occurring from the middle Paleocene to the late Oligocene. Due to the often fragmentary and incomplete nature of penguin fossils, physical aspects such as body size and mass must be calculated by measuring individual bones and scaling them against modern specimens. Through this method, lengths of 180cm and 160cm have been calculated for Anthropornis nordenskjoeldi and Palaeeudyptes klekowskii respectively, both being widely regarded as the largest penguins known to have ever lived (the latter even being given the common name of “Colossus Penguin”).
Giant penguins appear to have become extinct early in the Neogene. The reason for their disappearance is not currently understood, although a likely explanation may be a combination of climatic changes and feeding competition from pinnipeds (seals, sea lions, and walruses) which were undergoing an adaptive radiation at the time these giant penguins had declined.

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1. Pinguinus impennis 2. Waimanu manneringi 3. Pachydyptes ponderosus 4. Icadyptes salasi 5. Inkayacu paracasensis 6. Anthropornis nordenskjoeldi
Smaller than the large-bodied palaeeudyptines with whom they coexisted for a time, the Palaeospheniscinae and Paraptenodytinae may have been the ecological analogues of the modern spheniscine penguins, though they were probably not directly ancestral to them. Both subfamilies are relatively poorly understood at the timing of this blog post. Palaeospheniscines, also known as “slender-footed penguins”, contain five species within the genus Palaeospheniscus. They were small to medium-sized penguins that ranged in body length from 50 to 75cm, and occurred from the early Miocene to early Pliocene of southern Africa and South America. Paraptenodytines, also known as the “stout-footed penguins”, contains four known species within the genera Arthrodytes and Paraptenodytes. These occurred from the late Eocene to the middle Miocene of South America.
The group containing all modern penguins, all of which belong to the subfamily Spheniscinae, arose during the late Paleogene and recognizable members of today’s genera began to appear during the middle Miocene (14 to 13mya). The radiation of this group appears to correspond to two episodes of global climatic cooling.
Among modern penguins, the genus Aptenodytes (“great penguins”) are the most basal, with DNA evidence showing that these birds split from other spheniscines around 40mya. The earliest known fossil evidence for this genus comes from the early Pliocene of New Zealand and ascribed to the species A. ridgeni. The two modern members of the genus are characterized by yellow-orange neck, breast, and beak patches. Chicks are almost naked upon hatching and brooding adults incubate their eggs on their feet beneath a specialized fold of skin.
The genus Pygoscelis (“brush-tailed penguins”) are the next to diverge with DNA evidence showing that a split occurred at about 38mya and are said to most closely resemble the common ancestor of the Spheniscinae in physical form. Fossils from the genus date to the late Miocene of South America and New Zealand. There are three modern species which breed in Antarctica and southern South America.
The oldest fossils of the genus Spheniscus (“banded penguins”) date back to the middle Miocene. There are four modern species distributed through southern Africa and the southern and western coasts of South America up to the equatorial islands of Galapagos. Members of the genus are characterized by a single band of black that runs around their bodies bordering their black dorsal coloring, black beaks with a small vertical white band, distinct spots on their bellies, and a small patch of unfeathered or thinly feathered skin around their eyes that can be either white or pink. All members of this genus raise their young in nests situated in burrows or natural depressions in the earth. They are also renowned for their loud, braying vocalizations which earn them the nickname of the "jack-ass penguins".
The genus Eudyptula (“little penguins”) contains three modern species which are distributed through southern Australia and New Zealand. They are burrow-nesters distinguished by their small body size and iridescent dorsal plumage which gives them a bluish-black appearance.
Members of the genus Eudyptes (“crested penguins”) are characterized by their hair-like yellow ornamental head feathers and their reddish-colored beaks. This is the most specious of the modern penguin genera, containing eight species. These form a clade with the New Zealand endemic genus Megadyptes, which has a single living species and one recently extinct after first contact with the Maori. The two genera apparently diverged from each other during the middle Miocene (15 or 14mya) and the modern species of Eudyptes all radiated between the late Miocene and late Pliocene (about 8 to 3mya).

 

The largest penguin of all time was Palaeeudyptes klekowskii
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Palaeeudyptes klekowskii was a species of the extinctpenguingenus Palaeeudyptes. It was until recently thought to have been approximately the size of its congener Palaeeudyptes antarcticus, which would mean it was somewhat larger than the modern emperor penguin, but a new study shows it was in fact almost twice as tall. It is known from an extensive collection of fossil bones from the Late Eocene (34-37 MYA) of the La Meseta Formation on Seymour Island, Antarctica. P. klekowskii was at first not recognized as a distinct species, and despite the coexistence of two so closely related species of similar size as Palaeeudyptes gunnari and P. klekowskii seeming somewhat improbable, the amount of fossil material suggests that the two species are indeed diagnosably different.


Other largest penguin was Anthropornis nordenskjoeldi of New Zealand and Antarctica.
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It stood 1.7 meters (5 feet 7 inches) in height and was 90 kilograms (200 pounds) in weight. Anthropornis is a genus of giant penguin that lived 37-45 million years ago, during the Late Eocene and the earliest part of the Oligocene.It reached 1.7 m (5 ft 7 in) in height and 90 kg (200 lb) in weight. Fossils of it have been found on Seymour Island off the coast of Antarctica and in New Zealand. By comparison, the largest modern penguin species, the emperor penguin, is just 1.2 m (3 ft 11 in) tall.

The type species, Anthropornis nordenskjoldi, had a bent joint in the wing, probably a carryover from flying ancestors.


Similar in size were the New Zealand giant penguin (Pachydyptes pondeorsus) with a height of 1.4 to 1.6 m (4.6 to 5.2 ft) and weighing around 80 to possibly over 100 kg

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Pachydyptes is an extinct genus of penguin. It contains the single species Pachydyptes ponderosus, the New Zealand giant penguin. This taxon is known from a few bones from Late Eocene (37 to 34 MYA) rocks in the area of Otago.

With a height of 140 to 160 cm (about 5 ft) and weighing around 80 to possibly over 100 kg, it was the second-tallest penguin ever, surpassed only by Anthropornis nordenskjoeldi in height, but probably not in weight.
Pachydyptes was slightly larger than Icadyptes salasi, the best-identified of the giant penguins.


Icadyptes salasi
at 1.5 m (4.9 ft) tall.

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The fossilised remains of the penguin, which lived 36 million years ago, were found in the coastal desert of Peru by the team of North Carolina State Universitypalaeontologist Dr. Julia Clarke, assistant professor of marine, earth and atmospheric sciences. Its well-preserved fossil skeleton was found on the southern coast of Peru together with an early Eocene species Perudyptes devriesi (comparable in size to the living King penguin), and the remains of three other previously undescribed penguin species, all of which seem to have preferred the tropics over colder latitudes. Perudyptes devriesi is named after the country, and Thomas DeVries, a Vashon Island High School science teacher who has long worked in Peru.
Icadyptes salasi and Perudyptes devriesi appear to have flourished at warmer latitudes at a time when world temperatures were at their warmest over the past 65 million years. Only a few modern-day penguins, such as the African and Galapagos penguins prefer such a balmy climate.
The discovery of the fossils has caused a re-evaluation of penguin evolution and expansion. Previously, scientists believed that penguins evolved near the poles in Antarctica and New Zealand, and moved closer to the equator around 10 million years ago. Since Icadyptes salasi lived in Peru during a period of great warmth, penguins must have adapted to warm climates around 30 million years earlier than previously believed.

















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Автор: valentint
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