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17.12.2015 14:07 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part1 Mammals ch.6 Rodents,Erinaceomorphs and Lagomorphs
Автор: valentint Категория: Забавление   
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Rodents (Rodentia)
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The single largest group of mammals is the Rodentia. Most non-flying mammals are rodents: there are about 1,500 living rodent species (out of about 4,000 living mammals overall). Most people are familiar with mice, rats, hamsters, and guinea pigs, which are commonly kept as pets. The Rodentia also includes beavers, muskrats, porcupines, woodchucks, chipmunks, squirrels, prairie dogs, marmots, chinchillas, voles, lemmings, and many others.
Some molecular clock data suggest modern rodents (members of the order Rodentia) had appeared by the late Cretaceous, although other molecular divergence estimations are in agreement with the fossil record.
Rodents are thought to have evolved in Asia, where local multituberculate faunas were severely affected by the Cretaceous–Paleogene extinction event and never fully recovered, unlike their North American and European relatives. In the resulting ecological vacuum, rodents and other Glires were able to evolve and diversify, taking the niches left by extinct multituberculates. The correlation between the spread of rodents and the demise of multituberculates is a controversial topic, not fully resolved. American and European multituberculate assemblages do decline in diversity in correlation with the introduction of rodents in these areas, but the remaining Asian multituberculates co-existed with rodents with no observable replacement taking place, and ultimately both clades co-existed for at least 15 million years.
The history of the colonization of the world"s continents by rodents is complex. The movements of the large superfamily Muroidea (including hamsters, gerbils, true mice and rats) may have involved up to seven colonizations of Africa, five of North America, four of Southeast Asia, two of South America and up to ten of Eurasia.
During the Eocene, rodents began to diversify. Beavers appeared in Eurasia in the late Eocene before spreading to North America in the late Miocene.Late in the Eocene, hystricognaths invaded Africa, most probably having originated in Asia at least 39.5 million years ago.From Africa, fossil evidence shows that some hystricognaths (caviomorphs) colonized South America, which was an isolated continent at the time, evidently making use of ocean currents to cross the Atlantic on floating debris. Caviomorphs had arrived in South America by 41 million years ago (implying a date at least as early as this for hystricognaths in Africa),and had reached the Greater Antilles by the early Oligocene, suggesting that they must have dispersed rapidly across South America.
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Nesomyid rodents are thought to have rafted from Africa to Madagascar 20–24 million years ago. All 27 species of native Malagasy rodents appear to be descendents of a single colonization event.
By 20 million years ago, fossils recognizably belonging to the current families such as Muridae had emerged.By the Miocene, when Africa had collided with Asia, African rodents such as the porcupine began to spread into Eurasia.Some fossil species were very large in comparison to modern rodents and included the giant beaver, Castoroides ohioensis, which grew to a length of 2.5 m (8 ft 2 in) and weight of 100 kg (220 lb).The largest known rodent was Josephoartigasia monesi, a pacarana with an estimated body length of 3 m (10 ft).
The first rodents arrived in Australia via Indonesia around 5 million years ago. Although marsupials are the most prominent mammals in Australia, many rodents, all belonging to the subfamily Murinae, are among the continent"s mammal species.There are about fifty species of "old endemics", the first wave of rodents to colonize the country in the Miocene and early Pliocene, and eight true rat (Rattus) species of "new endemics", arriving in a subsequent wave in the late Pliocene or early Pleistocene. The earliest fossil rodents in Australia have a maximum age of 4.5 million years,and molecular data is consistent with the colonization of New Guinea from the west during the late Miocene or early Pliocene followed by rapid diversification. A further wave of adaptive radiation occurred after one or more colonizations of Australia some 2 to 3 million years later.
Rodents participated in the Great American Interchange that resulted from the joining of the Americas by formation of the Isthmus of Panama, around 3 million years ago in the Piacenzian age.In this exchange, a small number of species such as the New World porcupines (Erethizontidae) headed north.However, the main southward invasion of sigmodontines preceded formation of the land bridge by at least several million years, probably occurring via rafting.Sigmodontines diversified explosively once in South America, although some degree of diversification may have already occurred in Central America before the colonization.Their "head start" has relegated other North American rodent groups (sciurids, geomyids, heteromyids and nonsigmodontine cricetids) to a minor presence in the contemporary South American fauna.


Josephoartigasia monesi was the largest rodent of all time, approximately 3 metres (9.8 feet) long and 1.5 metres (4.9 feet) tall and weighing an estimated 1 tonne.

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Josephoartigasia monesi, an extinct species of South American caviomorph rodent, is the largest rodent known, and lived from approximately 4 to 2 million years ago during the Pliocene to early Pleistocene. The species is one of two in the Josephoartigasia genus, the other being J. magna. J. monesi is sometimes called the giant pacarana, after its closest living relative, the pacarana (Dinomys branickii) in the family Dinomyidae. The species may have weighed a ton, considerably larger than its closest living relative, the pacarana.
The skull of the holotype is 53 cm (21 in) long, and the remaining incisor is more than 30 cm (12 in) in length. The total estimated body length is 3 m (10 ft), with a height of 1.5 m (5 ft).
There is no dispute that J. monesi replaces Phoberomys pattersoni, a related and somewhat older species that lived in Venezuela during the Late Miocene, as the largest rodent. However, size comparisons are difficult because previous estimates of 400 and 700 kg (880 and 1,540 lb) for P. pattersoni were based on forelimb and hindlimb elements, which are not present in the J. monesi specimen.

By comparing the skull with various extant species of rodent, the authors of the original paper estimated a mass between 468 and 2,586 kg (1,032 and 5,701 lb), with a median estimate of 1,211 kg (2,670 lb).A later researcher revisited the numbers and came up with a more conservative estimate of 350 to 1,534 kg (772 to 3,382 lb), with a median of 900 kg (2,000 lb).
J. monesi is known from an almost complete skull, which was recovered from the San Josй Formation on the coast of Rнo de la Plata in Uruguay. Discovered in 1987, but not scientifically described until 2008, the specimen is preserved in Uruguay"s National History and Anthropology Museum. Josephoartigasia monesi was named after the paleontologist, Alvaro Mones, for his study on the rodent in 1966.
The rodent"s fearsome front teeth and large size may have been used to fight over females for breeding rights and may also have helped defend against predators, including carnivorous marsupials, saber-toothed cats, and terror birds.

The rodent may have lived in an estuarine environment or a delta system with forest communities, and may have eaten soft vegetation.It has been stated that J. monesi probably fed on aquatic plants and fruits, because its molars are small and not good for grass or other abrasive (vegetation). Larger mammals also have the advantage of access to low-quality food resources, such as wood, that smaller species are unable to digest.
Finite element analysis was used to estimate the maximum bite force of J. monesi.This study concluded that the bite of J. monesi possibly generated up to 4165 N of force, three times as powerful as predicted for modern day tigers. The study also speculated that J. monesi behaved similarly to elephants, utilizing it"s incisors like tusks for digging or defense.
Before the discovery of Josephoartigasia monesi, another giant rodent was known, Phoberomys insolita, but it was known from only a few fragments, so its real size is unknown.


A slightly smaller relative, Phoberomys pattersoni, was found, which was 4.5 meters long,1.5 meters tall and weighed around 700 kilograms.
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The description of an almost complete Phoberomys pattersoni in 2000 led to worldwide headlines of Ratzilla (after the Japanese kaiju Godzilla). These rare remains allowed for one of the most accurate size estimates of this genus which led to it being considered as one of the largest rodents ever to live, although despite the more popular name of Ratzilla, Phoberomys is thought to have been more like a guinea pig than a rat. The high crowned molars of Phoberomys indicate that it was a grass grazer rather than a browser of vegetation.
Phoberomys was many times bigger than the largest rodent alive today, the capybara (Hydrochoerus hydrochaeris). It is speculated however that Phoberomys may have been semi aquatic like the capybara, although the water would have been a very dangerous place to be since giant crocodiles like
Purussaurus are known to have lived in South America during the Miocene. Additional threats could have come from the larger and more powerful phorusrhacid birds like Brontornis and Kelenken. Smaller predators such as the sabre-toothed marsupial Thylacosmilus would have been more of a threat to smaller juvenile Phoberomys.
Although we can accurately reconstruct P. pattersoni, the earlier species P. insolita may have actually been bigger, although the lack of total remains for this species makes it hard to be certain. Today another rodent called
Josephoartigasia is considered to be even bigger than Phoberomys.
An almost complete skeleton was discovered in Urumaco, Venezuela in 2000. The new species was later classified with the name Phoberomys pattersoni in honor of palaeontologist Brian Patterson.From the fossil, researchers have been able to reconstruct its size and probable lifestyle. It was 3 m (9.8 ft) long, with an additional 1.5 m (4.9 ft) tail, and probably weighed between 250 kg (550 lb) and 700 kg (1,500 lb)), making it for some years the largest known rodent for which a good size and weight estimate was possible. Its congenerPhoberomys insolita was a bit larger still, but it is not known from any reasonably complete remains and thus its size cannot be estimated more precisely.


The largest beaver was the giant beaver of North America.
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It grew over 8 ft (2.4 m) in length and weighed roughly 60 to 100 kg (130 to 220 lb), also making it one of the largest rodents to ever exist. Castoroides, also known as giant beavers, were much larger than modern beavers. Their average length was approximately 1.9 m (6 ft), and they could grow as large as 2.2 m (7 ft). The weight of the giant beaver could vary from 90 kg (198 lb) – 125 kg (276 lb). This makes it the largest known rodent in North America during the Pleistocene and the largest known beaver.

The hind feet of the giant beaver were much larger than in modern beavers, while the hind legs were shorter. The tail was longer but may have been narrower. However, because soft tissues decay, it is not known whether its tail resembled the tails in modern beavers, and it can only be assumed that its feet were webbed like in modern species. The skull structure of the giant beaver shows that it presumably participated in extended underwater activity, thanks to the ability to take in more oxygen into its lungs.
One of the defining characteristics of the giant beaver were their incisors, which differ in size and shape than those of modern beavers. Modern beavers have chisel-like incisor teeth for gnawing on wood, while the teeth of the giant beaver were bigger and broader, and grew to about 15 cm (6 in) long. These incisors were not as efficient at cutting wood, therefore it is possible that the giant beaver did not construct dams.
One other major difference between the giant beaver and the modern beaver is that the size of its brain was proportionally smaller. As a result, giant beavers may have had inferior interactions in its environment as well as less complex patterns of thoughts and behavior.
The Casteroides fossils were discovered in 1837 in a peat bog in Ohio, hence its species epithet ohioensis. Catalogue no.1195, Mus. North. Ind. Hist. Soc. Well- preserved skull of Castoroides ohioensis but with the mandibles lost, both zygomatic arches missing, and the facial portions of the maxillae broken away; dental series complete and in good condition. Castorrides had cutting teeth up to 15 cm-long with prominently-ridged outer surfaces.These strong enamel ridges would have acted as girders to support such long teeth. Further, the deep masseteric fossa of the lower jaw suggests a very powerful bite. Perhaps their teeth could have acted as both wood-cutters and gouges.There is no clear evidence that the giant beaver felled trees or built dams, but a possible lodge was discovered near New Knoxville, Ohio about 1912. Part of a giant beaver skull and the lodge were located in a peaty layer surrounded by loam. In Ohio, there have been claims of a possible giant beaver lodge four feet high and eight feet in diameter, formed from small saplings. The recent discovery of clear evidence for lodge building in the related genus Dipoides indicates that the giant beaver probably also built lodges.

Fossils of Casteroides are concentrated around the midwestern United States in states near the Great Lakes, particularly Illinois and Indiana, but specimens are recorded from Alaska and Canada to Florida. In Canada, fossils of this species are commonly found in the Old Crow Basin, Yukon, and single specimens are known from Toronto, Ontario and Indian Island, New Brunswick. A hitherto overlooked 1891 record of a Casteroides skull from near Highgate, Ontario is the earliest for Canada. In Old Crow region, Casteroides fossils occur in deposits of the Sangamonian interglacial.
The discovery of giant beaver remains in New Brunswick add significantly to the Quaternary terrestrial mammal fauna of New Brunswick and suggest that the terrestrial fauna was probably richer than earlier evidence indicated. The know North American distribution of giant beaver is not significantly changed by this occurrence. Specimens from Florida have been placed in a subspecies, Castoroides ohioensis dilophidus, based on differences in premolar and molar features. Castoroides, the giant beaver, is recorded from 25 Pleistocene localities in Florida, 23 of Rancholabrean age, one possibly of Irvingtonian age, and one of late Blancan age.
Castorides leiseyorum specimens were unearthed in Florida and South Carolina. The latter site (Cooper River) was dated at 1.8 million—11,000 years ago. The Florida specimens were dated by John Alroy, Ph.D. using appearance event ordination for an age of 2.1 million years ago (Mya). Castoroides leiseyorum was named by S. Morgan and J. A. White in 1995 for the Leisey family, phosphatequarry-owners who found the first skull.Specimens were found in Leisey Shell Pit 1A and 3B, Hillsborough County, Florida, in paleontological sites about 2.1 Mya. Specimens were also found at the Strawberry Hill site, (Cooper River dredging) Charleston County, South Carolina from about 1.8 Mya to 11,000 years ago.


Rabbits, hares, and pikas (Lagomorpha)
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Mammals assigned to this Order superficially resemble rodents, but lagomorphs differ from rodents in several essential features. One of these is the peculiar tandem arrangement of the front (incisor) teeth, with a large tooth in front on each side and a small peglike tooth directly behind it. Also, the number of premolars is 2/2 or 3/2 (2/1 or 0/0 in rodents), so that the total number of teeth is 26 or 28 and never as few as the 16 to 22 found in rodents.
This group of mammals is largely diurnal or crepuscular in habit; the food is almost entirely vegetable matter — grasses, forbs, bark of trees and shrubs, and so forth. Because of their usually large size and food predilections, lagomorphs frequently come into conflict with grazing, agriculture, and forestry interests. No lagomorphs hibernate.
The evolutionary history of the lagomorphs is still not well understood. Until recently, it was generally agreed that Eurymylus, which lived in eastern Asia and dates back to the late Paleocene or early Eocene, was an ancestor of the lagomorphs.More recent examination of the fossil evidence suggests that the lagomorphs may have instead descended from Anagaloidea, also known as "mimotonids", while Eurymylus was more closely related to rodents (although not a direct ancestor).The leporids first appeared in the late Eocene and rapidly spread throughout the Northern Hemisphere; they show a trend towards increasingly long hind limbs as the modern leaping gait developed. The pikas appeared somewhat later in the Oligocene of eastern Asia. Lagomorphs were certainly more diverse in the past than in the present, with around 75 genera and over 230 species represented in the fossil record and many more species in a single biome. This is evidence that lagomorph lineages are declining.
Recent finds suggest an Indian origin for the clade, having possibly evolved in isolation when India was an island continent in the Paleocene.


The largest prehistoric lagomorph is Minorcan giant lagomorph (Nuralagus rex) at 23 kg (50 lbs).
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N
uralagus rex, occasionally called the Minorcan giant lagomorph, is an extinct rabbit that lived in the island of Minorca from the Messinian until around the middle of the Pliocene, when it became extinct (5 to 3million years ago) when Majorca and Minorca were united as one island, letting the goat-like ungulateMyotragus balearicus colonize Nuralagus"s habitat.
Nuralagus rex was very different from modern rabbits. With a height of half a meter and an estimated weight of 12 kg (26 lb), the species differed in size from all other noted fossils, and currently existing leporids. Nuralagus rex was six times the weight of the extant European rabbit (Oryctolagus cuniculus) and could weigh up to 23 kg (51 lb) It had a comparatively small skulland small sensory receptors. The small eyes and ears of this species are unlike those of modern rabbits. Nuralagus rex had a short stiff spine which resulted in low mobility and inability to jump. Due to the absence of predators on Minorca, this rabbit experienced what has been called the “island rule”. This rule states that big animals living on an island with no predators tend to evolve smaller and small animals living with no predators tend to evolve larger.
Nuralagus rex entered land constituting Minorca during the Messinian Salinity Crisis 5.3 million years ago. During this event, the desiccation of the Mediterranean Sea connected the island to mainland Spain, allow Nuralagus’ ancestor to colonize the area. The subsequent Zanclean flood then led to the Mediterranean’s return to its original sea levels, isolating the ancestor of Nuralagus on Minorca. Nuralagus’ divergence from its ancestor corresponds to the general increase in leporid diversity found in the Pliocene. Although the time of its extinction is uncertain, it possibly coincided with the general decrease in leporid diversity found in the Holocene.

There exists a dearth of knowledge pertaining to the evolutionary history of Nuralagus rex in relation to other lagomorphs. However, similarities between the dental morphology of Nuralagus and Eurasian members of the extinct genus Alilepus have led to speculation that Alilepus is closely related to and, possibly, the ancestor of Nuralagus. The theory that Alilepus gave rise to Nuralagus is apparently contradicted by the fact that Alilepus fossils found in Spain have been dated back to the quaternary period, well after Nuralagus would have been isolated on Minorca. Furthermore, Alilepus remains in areas other than Spain have been determined to be much older than Spanish specimins, implying that the Genus arrived in Spain after its inception. This opposes the idea that an ancestor of Alilepus living in Spain was also the ancestor of Nuralagus. On the other hand, Trischizolagus, an extinct genus of lagomorph thought to be a possible ancestor of the European rabbit, is known to have lived in Iberia between 3 and 6 million years ago, coinciding with the Messinean Crisis.Therefore, it is possible that Trischizolagus is the ancestor of Nuralagus.
Nuralagus’ unique traits were most likely the product of an insular environment containing no natural predators. Physical similarities between Nuralagus rex and Pentalagus furnessi (an extant insular lagomorph which until recently also did not have natural predators) despite the phylogenetic and geographical distance between the two species further supports this inference.


Hedgehogs, gymnures, shrews, and moles (Erinaceomorpha and Soricomorpha)
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1. Mckennatherium  2. Pholidocercus  3. Adunator  4. Macrocranion  5. Diacocherus

The traditional views regarding the mammalian order Insectivora are that the group descended from a single common ancestor and that it is comprised of the following families: Soricidae (shrews), Tenrecidae (tenrecs), Solenodontidae (solenodons), Talpidae (moles), Erinaceidae (hedgehogs and gymnures), and Chrysochloridae (golden moles).
Lipotyphla in turn had been derived by removing a number of groups from Insectivora, the previously used wastebasket taxon. Eulipotyphla comprises the hedgehogs and gymnures (family Erinaceidae, formerly also the order Erinaceomorpha), solenodons (family Solenodontidae), the desmans, moles, and shrew-like moles (family Talpidae) and true shrews (family Soricidae). True shrews, talpids and solenodons were formerly grouped in Soricomorpha; however, Soricomorpha has been found to be paraphyletic, since erinaceids are the sister group of shrews
Erinaceids are a relatively primitive group of placental mammals, having changed little since their origin in the Eocene. The so-called "giant hedgehog" (actually a gymnure) Deinogalerix, from the Miocene of Gargano Island (part of modern Italy), was the size of a large rabbit, and may have eaten vertebrate prey or carrion, rather than insects.


The largest creature of this group was Deinogalerix, measuring up to 60 cm in total length, with a skull up to 20 cm long.
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It occupied the same ecological niche as dogs and cats today. Deinogalerix (from Ancient Greek, "terrible/terror" + "shrew"), was a genus of the order Erinaceomorpha, which lived in Italy in the Late Miocene. The genus was apparently endemic to what was then Gargano Island, today"s Gargano peninsula. The Deinogalerix remains were first described in 1972.

The genus belonged to the subfamily of gymnures or moon-rats, which are not rats at all, but rather hairy, superficially rat-like relatives of the hedgehog lacking quills. Deinogalerix had a long, thin, conical face, small pointed ears, a lengthy, tapering tail and long hairs.
Deinogalerix koenigswaldi"s skull was 20 cm long, and the entire body measured 60 cm. It occupied the same ecological niche as dogs and cats today, except that it had more predators itself - such as the enormous barn owl Tyto gigantea.
It is believed that the species of Deinogalerix were insectivores, mostly feeding off invertebrates like beetles, dragonflies and crickets, and possibly even snails. But the larger species may also have hunted small mammals, reptiles and birds.
In the Late Miocene subepoch, what is at present Italy was mainly a group of small islands and only at a later date did majority of these join with the mainland. It is known that animals on these islands sometimes evolved quite differently from elsewhere. So it is possible that Deinogalerix may have lived exclusively in the Gargano.









 

 




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Автор: valentint
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