Потребителски вход

Запомни ме | Регистрация
Постинг
18.12.2015 16:12 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part1 Mammals ch.11 Camels and Litopterans
Автор: valentint Категория: Забавление   
Прочетен: 6016 Коментари: 0 Гласове:
0

Последна промяна: 23.05 22:58


Camels, Llamas, Guanacos, Alpacas, and Vicuсas
image

1. Camelops 2. Oxydactylus 3. Aepycamelus 4. Alticamelus 5. Stenomylus

Camels are mammals with long legs, a big-lipped snout and a humped back. There are two types of camels: dromedary camels, which have one hump, and Bactrian camels, which have two humps. Camels" humps consist of stored fat, which they can metabolize when food and water is scarce.

In addition to their humps, camels have other ways to adapt to their environment.
They have a third, clear eyelid that protects their eyes from blowing sand. Two rows of long lashes also protect their eyes. Sand up the nose can be a problem, but not for camels. They can shut their nostrils during sand storms.
image

The earliest known camel, called Protylopus, lived in North America 40 to 50 million years ago (during the Eocene).It was about the size of a rabbit and lived in the open woodlands of what is now South Dakota.By 35 million years ago, the Poebrotherium was the size of a goat and had many more traits similar to camels and llamas.The hoofed Stenomylus, which walked on the tips of its toes, also existed around this time, and the long-necked Aepycamelus evolved in the Miocene.
image

The direct ancestor of all modern camels, Procamelus, existed in the upper Miocene and lower Pliocene.Around 3–5 million years ago, the North American Camelidae spread to South America as part of the Great American Interchange via the newly formed Isthmus of Panama, where they gave rise to guanacos and related animals, and to Asia via the Bering land bridge.Surprising finds of fossil Paracamelus on Ellesmere Island beginning in 2006 in the high Canadian Arctic indicate the dromedary is descended from a larger, boreal browser whose hump may have evolved as an adaptation in a cold climate.This creature is estimated to have stood around nine feet tall.
The last camel native to North America was Camelops hesternus, which vanished along with horses, short-faced bears, mammoths and mastodons, ground sloths, sabertooth cats, and many other megafauna, coinciding with the migration of humans from Asia.



The largest camel that ever lived was the Megacamelus merriami. image

.It was 3,7 m in length, 370 cm in height, 1,748 - 3,695 kg of weight
image

Megacamelus is an extinct genus of terrestrial herbivore in the family Camelidae, endemic to North America from the Miocene through Pliocene 10.3—4.9 mya, existing for approximately 5.4 million years.
This was the largest species of camelid to roam the Earth, Megacamelus weighed upto 3.7 tonnes.
Four specimens were examined for estimated body mass by M. Mendoza, C. M. Janis, and P. Palmqvist. These specimens were estimated to weigh:

3,695.7 kg (8,100 lb)
3,059.8 kg (6,700 lb)
2,246.8 kg (5,000 lb)

1,747.9 kg (3,900 lb)



Gigantocamelus
and Titanotylopus from North America, both possibly reached 2,485.6 kg (5,480 lb) and a shoulder height of over 3.4 m (11 ft).
image
Gigantocamelus is an extinct genus of terrestrialherbivore the family Camelidae,endemic to North America from the Pliocene through Pleistocene 4.9 mya—300,000 years ago existing for approximately 4.68 million years. It was the 2nd largest known species of Camelid to roam the Earth.
Gigantocamelus was named by Barbour and Schultz (1939). Its type is Gigantocamelus fricki. It was synonymized subjectively with Titanotylopus by Webb (1965) and Kurten and Anderson (1980). It was assigned to Camelidae by Barbour and Schultz (1939), Harrison (1985), Dalquest (1992) and Honey et al. (1998).
Two specimens were examined for estimated body mass by M. Mendoza, C. M. Janis, and P. Palmqvist. These specimens were estimated to weigh:

2,485.6 kg (5,500 lb) and 1,669.5 kg (3,700 lb)


Titanotylopus spatulus
image
Titanotylopus is an extinct genus of terrestrial herbivore the family Camelidae, endemic to North America from the Miocene through Pleistocene 10.3 mya—300,000 years ago, existing for approximately 10 million years.
Titanotylopus is distinguished from other early large camelids by its large upper canines and other distinguishing dental characteristics, and absence of lacrimal vacuities in the skull. Unlike the smaller, contemporaneous Camelops, Titanotylopus had relatively broad second phalanges, suggesting that it had true padded "cameltoes," like modern camels.

The species Titanotylopus spatulus was characterized by broad, spatula-like incisors. It has been found at Grand View, Red Light, Hudspeth County, Texas, Donnelly Ranch, White Rock, Mullen II (Kansas), Sandahl Local Fauna (Nebraska) and Vallecito Creek, Colorado, 111 Ranch, Arizona in North America.
Titanotylopus possessed long and massive limbs, a comparatively small braincase, and a convex slope between the eyes. Its average height was 3.5 metres. Like modern camels, it possessed a hump for fat storage; evidence for this is provided by the long neural spines on its thoracic vertebrae.

 

Camelus moreli (Syrian camel)
image

It was 3 meters (9.8 feet) at the shoulder and 13 feet tall. The Syrian camel, Camelus moreli, is an extinct species of camel from Syria. It has been discovered in the Hummal area of the western Syrian desert. Found to have existed around 100,000 years ago, the camel was up to 3 metres (10 feet) tall at the shoulder, and 4 metres (13 feet) tall overall. The first of the fossils were discovered late in 2005, and several more were discovered about a year later. The new camelid was found together with Middle Paleolithic human remains.



Litopterans

image

 

1.Macrauchenia patachonica 2.Theosodon garretorum 3.Diadiaphorus caniadensis

This order, known only from South America and Antarctica,was common and varied in early faunas and persisted, in decreasing variety, into the Pleistocene. Early forms are near the condylarths, to such an extent that the litopterns might be considered merely as surviving and diversely specialized condylarths. They are suspected of being descended from South American condylarths, and therefore to have the same source as the latter. However, an opposing view has been that litopterns (together with other South-American ungulates) originated independently from other ungulates and thus are unrelated to condylarths. A proposed clade containing these groups is the Meridiungulata. Together with Neolicaphrium, Macrauchenia was among the youngest genera of litopterns, and these two appear to have been the only members of the group to survive the Great American Interchange; they became extinct at the end of the Pleistocene. Those that died out during this faunal exchange are presumed to have been driven to extinction at least in part by competition with invading North American ungulates.
The Litopterna, like the notoungulates and pyrotheres, are examples of ungulate mammals that arose relatively independently in "splendid isolation" on the island continent of South America. Like Australia, South America was isolated from all other continents following the breakup of Gondwana. During this period of isolation, unique mammals evolved to fill ecological niches similar to other mammals elsewhere. The Litopterna occupied ecological roles as browsers and grazers similar to horses and camels in Laurasia.
Sequencing of mitochondrial DNA recently extracted from an Macrauchenia patachonica fossil from a cave in southern Chile indicates that Litopterna is the sister group to Perissodactyla, making them true ungulates. The estimated divergence date is 66 million years ago.Analyses of collagen sequences obtained from Macrauchenia and the notoungulate Toxodon have led to the same conclusion, and add notoungulates to the sister group clade
.This contrasts with the results of some past morphological analyses which favoured them as afrotherians. It is consistent with some more recent morphological analyses which suggested they were basal euungulates. Panperissodactyla has been proposed as the name of an unranked clade to include perissodactyls and their extinct South American ungulate relatives.


Macrauchenia patachonica
image

Macrauchenia (name meaning "long llama", based on the now superseded Latin term for llamas, Auchenia, from Greek terms which literally mean "big neck") was a long-necked and long-limbed, three-toed South Americanungulatemammal, typifying the order Litopterna. The oldest fossils date back to around 7 million years ago, and M. patachonica disappears from the fossil record during the late Pleistocene, around 20,000-10,000 years ago. M. patachonica was the best known member of the family Macraucheniidae, and is known only from fossil finds in South America, primarily from the Lujan Formation in Argentina. The original specimen was discovered by Charles Darwin during the voyage of the Beagle. In life, Macrauchenia resembled a humpless camel with a short trunk, though it is not closely related to either camels or proboscideans.
Macrauchenia had a somewhat
camel-like body, with sturdy legs, a long neck and a relatively small head. Its feet, however, more closely resembled those of a modern rhinoceros, and had three hoofs each. It was a relatively large animal, with a body length of around 3 metres (9.8 ft) and a weight up to 1043 kg.
One striking characteristic of Macrauchenia is that, unlike most other mammals, the openings for nostrils on its skull were atop the head, leading some early scientists to believe that, much like a whale, it used these nostrils as a form of snorkel. Soon after some more recent findings[citation needed], this theory was rejected. An alternative theory is that the animal possessed a trunk, perhaps to keep dust out of the nostrils. Macrauchenia"s trunk may be comparable to that of the modern Saiga antelope.
One insight into Macrauchenia"s habits is that its ankle joints and shin bones may indicate that it was adapted to have unusually good mobility, being able to rapidly change direction when it ran at high speed.

Macrauchenia is known, like its relative Theosodon, to have had a full set of 44 teeth.
Macrauchenia was a herbivore, likely living on leaves from trees or grasses. Carbon isotope analysis of M. patachonica"s
tooth enamel, as well as analysis of its hypsodonty index (low in this case; i.e., it was brachydont), body size and relative muzzle width suggests that it was a mixed feeder, combining browsing on C3 foliage with grazing on C4 grasses. Scientists believe that, because of the forms of its teeth, Macrauchenia ate using its trunk to grasp leaves and other food. It is also believed that it lived in herds like modern-day wildebeest or antelope, the better to escape predators.
When Macrauchenia first arose, it would have been preyed upon by the largest of native South American predators,
terror birds such as Andalgalornis, and carnivorous sparassodontids such as Thylacosmilus. During the late Pliocene/Early Pleistocene, the Panama Isthmus formed, allowing predators of North American origin, such as the cougar, the jaguar, the South American giant short-faced bear, and the saber-toothed cat, Smilodon, to emigrate into South America and replace the native forms.
It is presumed that Macrauchenia dealt with its predators primarily by outrunning them, or, failing that, kicking them with its long, powerful legs, much like modern-day
vicuсa or camels[citation needed]. Its potential ability to twist and turn at high speed could have enabled it to evade pursuers. Macrauchenia appeared in the fossil record some 7 million years ago in South America (in the Miocene epoch). It is likely that Macrauchenia arose from either Theosodon or Promacrauchenia. Notoungulata and Litopterna were two ancient orders of ungulates which occurred only in South America. Most of these species became extinct through competition with invading North American ungulates during the Great American Interchange, after the establishment of the Central American land bridge. The litopterns Macrauchenia and Xenorhinotherium and the large notungulates Toxodon and Mixotoxodon were among the only South American ungulate genera to survive the Interchange. These last endemic South American hoofed animals died out at the end of the Lujanian (10,000-20,000 years ago) at roughly the time of arrival of humans at the end of the Pleistocene, along with numerous other large animals on the American continent (such as American proboscideans, horses, camelids, bears, and cats). As Macrauchenia was the last of the litopterns, the genus" extinction marks the close of the South American ungulate dynasty.
An analysis based on collagen sequences obtained from Macrauchenia and Toxodon found that litopterns along with notoungulates form a
sister group to perissodactyls, making them true ungulates 














 

 




Гласувай:
0
0



Няма коментари
Търсене

За този блог
Автор: valentint
Категория: Политика
Прочетен: 922507
Постинги: 225
Коментари: 18
Гласове: 16
Календар
«  Юли, 2020  
ПВСЧПСН
12345
6789101112
13141516171819
20212223242526
2728293031