The ground squirrels are members of the squirrel family of rodents which live on or in the ground, rather than trees. The term is most used for the medium-sized ground squirrels, as the larger ones are more known as marmots or prairie dogs, while the smaller and less bushy-tailed ground squirrels tend to be known as chipmunks. Together, they make up the "marmot tribe" of squirrels and the large and ground squirrel subfamily Xerinae, containing six living genera. Well-known members of this Holarctic group are the marmots, including the American groundhog, the chipmunks, the susliks, the prairie dogs, they are variable in size and habitus, but most are remarkably able to rise up on their hind legs and stand erect comfortably for prolonged periods. They tend to be far more gregarious than other squirrels, many live in colonies with complex social structures. Most Marmotini are rather short-tailed and large squirrels, the alpine marmot is the largest living member of the Sciuridae, at 53–73 cm in length and weighing 5–8 kg.
The chipmunks of the genus Tamias spend time in trees. Closer to typical squirrels in other aspects, they are considered a tribe of their own; the ground squirrel is renowned for its tendency to rise up on its hind legs. It does this when it must see over tall grasses; the squirrel curls its paws flat against its chest and sends a screeching call to warn other family members about the presence of predators. Palaeosciurus from Europe is the oldest known ground squirrel species, it does not seem to be close to any of the two to three living lineages of Marmotini; the oldest fossils are from the Early Oligocene, more than 30 million years ago, but the genus persisted at least until the mid-Miocene, some 15 mya. It is not clear; the subtribes diverged in the early to mid-Oligocene, as primitive marmots and chipmunks are known from the Late Oligocene of North America. The fossil record of the "true" ground squirrels is less well known, beginning only in the mid-Miocene, when modern susliks and prairie dogs are known to have inhabited their present-day range already.
Whether the Marmotini dispersed between North America and Eurasia via "island-hopping" across the Bering Straits or the Greenland region—which both at that time were temperate habitat—and from which continent they dispersed to which, or if both continents brought forth distinct subtribes which spread to the other, is not known and would require more fossil material to be resolved. In any case, that the comprehensive fossil record of Europe—at the relevant time separated from Asia by the Turgai Sea—lacks ancient Marmotini except the indeterminate Palaeosciurus might be taken to indicate an East Asian or western North American origin with trans-Beringia dispersal is the more satisfying hypothesis of it; this is supported by the enigmatic Chinese genus Sciurotamias, which may be the most ancient living lineage of this group, or—if the chipmunks are not included here—close to the common ancestor of the Tamiini and the Marmotini sensu stricto. In any case, expansion of the Marmotini to Africa was prevented by competitive exclusion by their close relatives the Protoxerini and Xerini—the native terrestrial and palm squirrels of that continent—which must have evolved at the same time as the Marmotini did.
Open areas including rocky outcrops, fields and sparsely wooded hillsides. Ground squirrels live in grassy areas such as pastures, golf courses and parks. Ground squirrels are omnivorous, will not only eat a diet rich in fungi, nuts and seeds, but occasionally insects and other small animals, they are known to eat mice several times their size. Basal and incertae sedis genera Palaeosciurus Sciurotamias Subtribe Tamiina: chipmunks Eutamias Neotamias Nototamias TamiasSubtribe Marmotina: marmots Arctomyoides Miospermophilus Paenemarmota Palaearctomys Protospermophilus Marmota Ictidomys: Thirteen-lined ground squirrel and related speciesSubtribe Spermophilina: true ground squirrels Spermophilinus Ammospermophilus Cynomys Spermophilus Below is a cladogram of ground squirrels derived from maximum parsimony analysis. Squirrel Tree squirrel Richardson's ground squirrel Helgen, Kristofer M.. "Generic Revision in the Holarctic Ground Squirrel Genus Spermophilus". Journal of Mammalogy. 90: 270–305. Doi:10.1644/07-MAMM-A-309.1.
Archived from the original on 2011-10-22. Steppan, Scott J.. L. & Hoffmann, R. S.: "Nuclear DNA phylogeny of the squirrels and the evolution of arboreality from c-myc and RAG1". Mol. Phyl. Evol. 30: 703–719. Doi:10.1016/S1055-790300204-5 PDF fulltext Thorington, R. W. & Hoffmann, R. S.: Family Sciuridae. In: Mammal Species of the World—A Taxonomic and Geographic Reference: 754–818. Johns Hopkins University Press, Baltimore. About California Ground Squirrels
The fox squirrel known as the eastern fox squirrel or Bryant's fox squirrel, is the largest species of tree squirrel native to North America. Despite the differences in size and coloration, they are sometimes mistaken for American red squirrels or eastern gray squirrels in areas where the species co-exist; the squirrel's total body length measures 45 to 70 cm, tail length is 20 to 33 cm, they range in weight from 500 to 1,000 grams. There is no sexual dimorphism in appearance. Individuals tend to be smaller in the west. There are three distinct geographical phases in coloration: In most areas the animals upper body is brown-grey to brown-yellow with a brownish-orange underside, while in eastern regions such as the Appalachians there are more strikingly-patterned dark brown and black squirrels with white bands on the face and tail. In the south can be found isolated communities with uniform black coats. To help with climbing, they have sharp claws, developed extensors of digits and flexors of forearms, abdominal musculature.
Fox squirrels have excellent vision and well-developed senses of smell. They use scent marking to communicate with other fox squirrels. "Fox squirrels have several sets of vibrissae, hairs or whiskers that are used as touch receptors to sense the environment. These are found above and below their eyes, on their chin and nose, on each forearm." The dental formula of S. niger is 22.214.171.124.0.1.3 × 2 = 20 The fox squirrel's natural range extends throughout the eastern United States, north into the southern prairie provinces of Canada, west to the Dakotas and Texas. They are absent in New England, New Jersey, most of New York, as well as northern and eastern Pennsylvania, they have been introduced to both northern and southern California, Idaho, Montana and New Mexico. While versatile in their habitat choices, fox squirrels are most found in forest patches of 40 hectares or less with an open understory, or in urban neighborhoods with trees, they thrive best among oak, hickory and pines, storing their nuts for winter.
Western range extensions in Great Plains regions such as Kansas are associated with riverine corridors of cottonwood. A subspecies native to several eastern US states is the Delmarva fox squirrel. Fox squirrels are most abundant in open forest stands with little understory vegetation. Ideal habitat is small stands of large trees interspersed with agricultural land; the size and spacing of pines and oaks are among the important features of fox squirrel habitat. The actual species of pines and oaks themselves may not always be a major consideration in defining fox squirrel habitat. Fox squirrels are observed foraging on the ground several hundred meters from the nearest woodlot. Fox squirrels commonly occupy forest edge habitat. Fox squirrels have two types of shelters: tree dens, they may have a tree cavity and a leaf nest. Tree dens are preferred over leaf nests for raising young; when den trees are scarce, leaf nests are used year-round. Leaf nests are built during the summer months in forks of deciduous trees about 30 feet above the ground.
Fox squirrels use natural crotches as tree dens. Den trees in Ohio had an average diameter at breast height of 21 inches and were an average of 58.6 yards from the nearest woodland border. About 88% of den trees in eastern Texas had an average d.b.h. of 12 inches or more. Dens are 6 inches wide and 14–16 inches inches deep. Den openings are circular and about 2.9 to 3.7 inches. Fox squirrels may make their own den in a hollow tree by cutting through the interior. Crow nests have been used by fox squirrels. Fox squirrels use leaf nests or tree cavities for litter rearing. Forest stands dominated by mature to over mature trees provide cavities and a sufficient number of sites for leaf nests to meet the cover requirements. Overstory trees with an average d.b.h. of 15 inches or more provide adequate cover and reproductive habitat. Optimum tree canopy closure for fox squirrels is from 20% to 60%. Optimum conditions understory closure occur. Fox squirrels are tolerant of human proximity, thrive in crowded urban and suburban environments.
They exploit human habitations for sources of food and nesting sites, being as happy nesting in an attic as they are in a hollow tree. Food habits of fox squirrels depend on geographic location. In general, fox squirrel foods include mast, tree buds, tubers, roots, bird eggs, seeds of pines and spring-fruiting trees, fungi. Agricultural crops such as corn, oats and fruit are eaten. Mast eaten by fox squirrels includes turkey oak, southern red oak, blackjack oak, bluejack oak, post oak, live oak. In Illinois, fox squirrels rely on hickories from late August through September. Pecans, black walnuts, osage orange fruits, corn are important fall foods. In early spring, elm buds and seeds are the most important food. In May and June, mulberries are used. By early summer, corn in the milk stage becomes a primary food. During the winter in Kan
Chipmunks are small, striped rodents of the family Sciuridae. Chipmunks are found in North America, with the exception of the Siberian chipmunk, found in Asia. Chipmunks may be classified either as a single genus, Tamias, or as three genera: Tamias, of which the eastern chipmunk is the only living member; these classifications are arbitrary, most taxonomies over the twentieth century have placed the chipmunks in a single genus. However, studies of mitochondrial DNA show that the divergence between each of the three chipmunk groups is comparable to the genetic dissimilarity between Marmota and Spermophilus. So the three genera classification has been adopted here; the common name may have been spelled "chitmunk", from the native Odawa word jidmoonh, meaning "red squirrel". The earliest form cited in the Oxford English Dictionary is "chipmonk", but "chipmunk" appears in several books from the 1820s and 1830s. Other early forms include "chipmuck" and "chipminck", in the 1830s they were referred to as "chip squirrels" in reference to the sound they make.
In the mid-1800s, John James Audubon and his sons included a lithograph of the chipmunk in their Viviparous Quadrupeds of North America, calling it the "chipping squirrel hackee". Chipmunks have been referred to as "striped squirrels", "timber tigers", "ground squirrels". Chipmunks have an omnivorous diet consisting of seeds and other fruits, buds, they commonly eat grass and many other forms of plant matter, as well as fungi and other arthropods, small frogs and bird eggs. Around humans, chipmunks can eat cultivated grains and vegetables, other plants from farms and gardens, so they are sometimes considered pests. Chipmunks forage on the ground, but they climb trees to obtain nuts such as hazelnuts and acorns. At the beginning of autumn, many species of chipmunk begin to stockpile nonperishable foods for winter, they cache their foods in a larder in their burrows and remain in their nests until spring, unlike some other species which make many small caches of food. Cheek pouches allow chipmunks to carry food items to their burrows for either storage or consumption.
Eastern chipmunks mate in early spring and again in early summer, producing litters of four or five young twice each year. Western chipmunks breed only once a year; the young emerge from the burrow after about six weeks and strike out on their own within the next two weeks. These small mammals fulfill several important functions in forest ecosystems, their activities harvesting and hoarding tree seeds play a crucial role in seedling establishment. They consume many different kinds of fungi, including those involved in symbiotic mycorrhizal associations with trees, are an important vector for dispersal of the spores of subterranean sporocarps which have co-evolved with these and other mycophagous mammals and thus lost the ability to disperse their spores through the air. Chipmunks construct expansive burrows which can be more than 3.5 m in length with several well-concealed entrances. The sleeping quarters are kept clean as feces are stored in refuse tunnels; the eastern chipmunk hibernates in the winter, while western chipmunks do not, relying on the stores in their burrows.
Chipmunks play an important role as prey for various predatory mammals and birds but are opportunistic predators themselves with regard to bird eggs and nestlings, as in the case of eastern chipmunks and mountain bluebirds. Chipmunks live about three years although some have been observed living to nine years in captivity. Chipmunks in captivity are said to sleep for an average of about 15 hours a day, it is thought that mammals which can sleep in hiding, such as rodents and bats, tend to sleep longer than those that must remain on alert. Genus Eutamias Siberian chipmunk, Eutamias sibiricusGenus Tamias Eastern chipmunk, Tamias striatus †Tamias aristusGenus Neotamias, sometimes considered subgenus Allen's chipmunk, Neotamias senex Alpine chipmunk, Neotamias alpinus Buller's chipmunk, Neotamias bulleri California chipmunk, Neotamias obscurus Cliff chipmunk, Neotamias dorsalis Colorado chipmunk, Neotamias quadrivittatus Durango chipmunk, Neotamias durangae Gray-collared chipmunk, Neotamias cinereicollis Gray-footed chipmunk, Neotamias canipes Hopi chipmunk, Neotamias rufus Least chipmunk, Neotamias minimus Lodgepole chipmunk, Neotamias speciosus Long-eared chipmunk, Neotamias quadrimaculatus Palmer's chipmunk, Neotamias palmeri Panamint chipmunk, Neotamias panamintinus Merriam's chipmunk, Neotamias merriami Red-tailed chipmunk, Neotamias ruficaudus Siskiyou chipmunk, Neotamias siskiyou Sonoma chipmunk, Neotamias sonomae Townsend's chipmunk, Neotamias townsendii Uinta chipmunk, Neotamias umbrinus Yellow-cheeked chipmunk, Neotamias ochrogenys Yellow-pine chipmunk, Neotamias amoenus Baack, Jessica K. and Paul V. Switzer.
"Alarm Calls Affect Foraging Behavior in Eastern Chipmunks." Ethology. Vol. 106. Dec. 2003. 1057–1066. Gordon, Kenneth Llewellyn; the Natural History and Behavior of the Western Chipmunk and the Mantled Ground Squirrel. Oregon: 1943 Wildlife and Nature – Chipmunk at the Wayback Machine
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya. Its subdivisions, its base, are somewhat in flux; the period was established by Adam Sedgwick, who named it after Cambria, the Latin name of Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells; as a result, our understanding of the Cambrian biology surpasses that of some periods. The Cambrian marked a profound change in life on Earth. Complex, multicellular organisms became more common in the millions of years preceding the Cambrian, but it was not until this period that mineralized—hence fossilized—organisms became common; the rapid diversification of life forms in the Cambrian, known as the Cambrian explosion, produced the first representatives of all modern animal phyla.
Phylogenetic analysis has supported the view that during the Cambrian radiation, metazoa evolved monophyletically from a single common ancestor: flagellated colonial protists similar to modern choanoflagellates. Although diverse life forms prospered in the oceans, the land is thought to have been comparatively barren—with nothing more complex than a microbial soil crust and a few molluscs that emerged to browse on the microbial biofilm. Most of the continents were dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia; the seas were warm, polar ice was absent for much of the period. Despite the long recognition of its distinction from younger Ordovician rocks and older Precambrian rocks, it was not until 1994 that the Cambrian system/period was internationally ratified; the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. The use of Treptichnus pedum, a reference ichnofossil to mark the lower boundary of the Cambrian, is difficult since the occurrence of similar trace fossils belonging to the Treptichnids group are found well below the T. pedum in Namibia and Newfoundland, in the western USA.
The stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, in Spain. The Cambrian Period was followed by the Ordovician Period; the Cambrian is divided into ten ages. Only three series and six stages are named and have a GSSP; because the international stratigraphic subdivision is not yet complete, many local subdivisions are still used. In some of these subdivisions the Cambrian is divided into three series with locally differing names – the Early Cambrian, Middle Cambrian and Furongian. Rocks of these epochs are referred to as belonging to Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian; each of the local series is divided into several stages. The Cambrian is divided into several regional faunal stages of which the Russian-Kazakhian system is most used in international parlance: *Most Russian paleontologists define the lower boundary of the Cambrian at the base of the Tommotian Stage, characterized by diversification and global distribution of organisms with mineral skeletons and the appearance of the first Archaeocyath bioherms.
The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago and ending at 485.4 million years ago. The lower boundary of the Cambrian was held to represent the first appearance of complex life, represented by trilobites; the recognition of small shelly fossils before the first trilobites, Ediacara biota earlier, led to calls for a more defined base to the Cambrian period. After decades of careful consideration, a continuous sedimentary sequence at Fortune Head, Newfoundland was settled upon as a formal base of the Cambrian period, to be correlated worldwide by the earliest appearance of Treptichnus pedum. Discovery of this fossil a few metres below the GSSP led to the refinement of this statement, it is the T. pedum ichnofossil assemblage, now formally used to correlate the base of the Cambrian. This formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago gained favour, though the methods used to obtain this number are now considered to be unsuitable and inaccurate.
A more precise date using modern radiometric dating yield a date of 541 ± 0.3 million years ago. The ash horizon in Oman from which this date was recovered corresponds to a marked fall in the abundance of carbon-13 that correlates to equivalent excursions elsewhere in the world, to the disappearance of distinctive Ediacaran fossils. There are arguments that the dated horizon in Oman does not correspond to the Ediacaran-Cambrian boundary, but represents a facies change from marine to evaporite-dominated strata — which w
The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles and archosaurs; the world at the time was dominated by two continents known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors; the Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earth's history, in which nearly 96% of marine species and 70% of terrestrial species died out.
It would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian–Triassic extinction event was protracted; the term "Permian" was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Édouard de Verneuil; the region now lies in the Perm Krai of Russia. Official ICS 2017 subdivisions of the Permian System from most recent to most ancient rock layers are: Lopingian epoch Changhsingian Wuchiapingian Others: Waiitian Makabewan Ochoan Guadalupian epoch Capitanian stage Wordian stage Roadian stage Others: Kazanian or Maokovian Braxtonian stage Cisuralian epoch Kungurian stage Artinskian stage Sakmarian stage Asselian stage Others: Telfordian Mangapirian Sea levels in the Permian remained low, near-shore environments were reduced as all major landmasses collected into a single continent—Pangaea; this could have in part caused the widespread extinctions of marine species at the end of the period by reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major landmasses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean, the Paleo-Tethys Ocean, a large ocean that existed between Asia and Gondwana; the Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys Ocean to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic era. Large continental landmass interiors experience climates with extreme variations of heat and cold and monsoon conditions with seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea; such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian. Three general areas are noted for their extensive Permian deposits—the Ural Mountains and the southwest of North America, including the Texas red beds.
The Permian Basin in the U. S. states of Texas and New Mexico is so named because it has one of the thickest deposits of Permian rocks in the world. The climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an ice age. Glaciers receded around the mid-Permian period as the climate warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles. Permian marine deposits are rich in fossil mollusks and brachiopods. Fossilized shells of two kinds of invertebrates are used to identify Permian strata and correlate them between sites: fusulinids, a kind of shelled amoeba-like protist, one of the foraminiferans, ammonoids, shelled cephalopods that are distant relatives of the modern nautilus. By the close of the Permian, trilobites and a host of other marine groups became extinct. Terrestrial life in the Permian included diverse plants, fungi and various types of tetrapods; the period saw a massive desert covering the interior of Pangaea.
The warm zone spread in the northern hemisphere. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals became marginal elements; the Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began; the swamp-loving
Prevost's squirrel or Asian tri-colored squirrel is a species of rodent in the family Sciuridae. It is found in forest in the Thai-Malay Peninsula, Sumatra and nearby smaller islands, with an introduced population in northern Sulawesi, they eat fruits, seeds, flowers and bird eggs. It has been observed feeding on durians such as Durio graveolens; these squirrels drop the seeds when finished with their meal. This seed distribution away from the parent plant increases survival for the fruiting plant species; the "typical" subspecies of Prevost's squirrel are among the most colourful mammals in the world with their black upperparts and tail, reddish-orange underparts, whitish thighs and flanks. The markings in some subspecies are duller, C. prevostii pluto from northeastern Borneo is reddish-orange below and black above. Thorington, R. W. Jr. and R. S. Hoffman. 2005. Family Sciuridae. Pp. 754–818 in Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Johns Hopkins University Press, Baltimore.
Prevost's Squirrel at Animal Diversity Web