Families of Class Mammalia Part 1: Eutherians I

Golden moles

21

Their eyes are non-functional and covered with furred skin. seldom seen elsewhere among living mammals, they have three forearm long-bones, hyoid-mandible articulation, and a hypertrophied malleus, adapted for the detection of seismic signals.

Otter shrews

3

They have dense, water repellent fur. They move through the water by undulating their tail in a side-to-side motion similar to the motions made by a crocodile swimming.

Tenrecs

23

From Madagascar, Tenrecs are wildly diverse; as a result of convergent evolution some resemble hedgehogs, shrews, opossums, rats, and mice. They have a low body temperature, sufficiently so that they do not require a scrotum to cool their sperm as do most other mammals.

Elephant shrews or sengis

20

They are in fact more closely related to elephants than to shrews. Although the size of the trunk varies among species, all are able to twist it about in search of food.

Aardvarks

1

Their unique type of teeth and other morphological characteristics had made it clear that aardvarks are not closely related to any other living mammals. Their teeth have a "tubulidentate" microstructure, lacking enamel, and are just rounded structures of dentine. Another unique trait is that their small milk teeth are lost before the animal is born.

Elephants

3

It is believed that the common ancestor of Proboscidea, Sirenia and Hyracoidea was some kind of large amphibious hyracoid. One hypothesis is that these animals spent most of their time under water, using their trunks like snorkels for breathing.

Dugongs

1

It also contains the recently extinct species Steller's sea cow (Hydrodamalis gigas). Unlike manatees, a dugong's tail is fluked, similar in shape to that of a whale.

Manatees

3

The manatee has prehensile lips; the upper lip pad is split into left and right sides which can move independently to manipulate and tear at plants. The manatee does not have front teeth, however, behind the lips, on the roof of the mouth, there are dense, ridged pads.

Hyraxes or dassies

5

Hyraxes share several unusual characteristics with mammalian orders Proboscideaand Sirenia, like the males having their testicles tucked up in their abdominal cavity next to the kidneys, and the females having a pair of teats near their armpits.

Silky anteaters or pygmy anteaters

7

The ribs are broad and flat, overlapping to form an internal armoured casing that protects the chest.

Giant anteaters, tamanduas

3

They have no teeth, but produce a large amount of sticky saliva to trap the insects, as well as backward-pointing spines on their tongues. Ants and termites are almost their only food in the wild, and their primary source of water. They have such sharp claws that they cannot touch their young without causing injury.

Three-toed sloths

4

The muscles that sloths use to grip and produce a pulling motion are much more prominent than those that produce a pushing motion, so they struggle to support their body weight when walking on all four limbs. The abdominal organs close to their diaphragm are attached to their lower ribs by fibrinous adhesions, which prevent the weight of these organs from compressing their lungs when hanging, making inhalation easier.

Two-toed sloths

2

They have three digits on their hindlimbs. When they cannot find food, they have been known to eat the algae that grow on their fur for nutrients. Food can take up to a month to digest due to their slow metabolism. Depending on when in the excretion cycle a sloth is weighed, urine and feces may account for up to 30% of the animal’s body weight.

Long-nosed armadillos

7

They are unable to roll into a complete ball due their excessive number of dermal plates, but have a unique ability to build up an oxygen debt and hold their breath for up to six minutes.

Fairy armadillos, hairy armadillos, giant armadillos, three banded armadillos, pichis

14

They include the extinct genus Glyptodon.

Rabbits, hares and jackrabbits

 

They are coprophagous, as they pass food through their digestive systems twice, first expelling it as soft green feces, called cecotropes, which they then reingest, eventually producing hard, dark fecal pellets. They are induced ovulators (ovulate during mating).

Pikas

37

They resemble rabbit, but with short, rounded ears. Rather than hibernate during winter, pikas forage for grasses and other forms of plant matter and stash these findings in protected dens in a process called "haying".

Scaly-tailed squirrels

6

They have evolved membranes between their front and hind legs independently from flying squirrels, and have two rows of pointed, raised scales on the undersides of their tails, thought to prevent slipping when at rest while climbing.

Springhares

2

They look like a peculiar, large, rabbit- or kangaroo-like rodent, and inhabit arid lands of southern Africa. They have enlarged hind feet and a long, heavy tail.

Cameroon scaly-tail

1

They have scales like the scaly-tailed squirrels, but no membranes. Their ankles have a tuft of ‘spoon-hairs’, which cover a glandular area of unknown function.

Beavers

2

Their eyes are protected during swimming by a nictating membrane, and their nostrils and ears can be closed by special muscles. Air flows directly from their nares to the trachea without entering the mouth cavity. The back of the tongue is raised and can be fitted tightly against the palate, blocking the passage of water from the mouth, so they can open their mouth to gnaw or carry branches while underwater.

Pocket gophers (true gophers)

41

They are commonly known for their extensive tunneling activities and their ability to destroy farms and gardens. They have large cheek pouches, from which the word "pocket" in their name derives, that are fur-lined, can be turned inside out, and extend from the side of the mouth well back onto the shoulders.

Kangaroo rats, kangaroo mice, pocket mice and spiny pocket mice

59

Kangaroo rats have no need to drink because they are able to extract sufficient water from metabolising their food, obtaining half a gram of water from each gram of seeds eaten.

Gundis or comb-rats

5

They have only four toes on all feet and the middle toes of the hind feet carry comb-like bristles, which earned them the name "comb rat".

Laotian rock rat

1

They are described as a Lazarus taxon due to the 11-million-year gap between the most recent representative in the fossil record and the existence of the sole extant species today.

African mole rats or blesmols

21

Blesmols have very poor vision, although they may use the surfaces of their eyes for sensing air currents. They are also able to close their nostrils during digging to prevent them from clogging with dirt. Most blesmol species dig using their powerful incisors, which are projected forward and protrude from the mouth even when the mouth is closed.

Naked mole-rats or sand puppies

1

They are the only mammalianwith an almost entirely ectothermic (cold-blooded) temperature regulation, and have a complex social structure split between reproductive and non-reproductive castes, making it and the closely related Damaraland mole-rat the only widely recognized examples of eusociality (the highest classification of sociality) in mammals. They lack pain sensitivity in its skin, and have very low metabolic and respiratory rates. It is also remarkable for its longevity and its resistance to cancer and oxygen deprivation.

Old World porcupines

11

Each of their quills is conspicuously marked with black and white bands, and are densely arrayed over the rump and back. They rattle when shaken, serving as a warning to potential predators. If that doesn't work, the porcupine may attempt to charge backwards into the predator.

Dassie rats

1

They live in groups in arid rocky areas, and use a distinctive whistle to warn of predators. They do not require free water, and have a remarkable ability to flatten their bodies, since their ribs are flexible and their skulls are unusually flat, to squeeze into rock crevices when threatened. The females even have their nipples on their sides so that the young can nurse even when their mother is hiding flattened in a crack.

Cane rats

2

Cane rats have broad, deeply orange incisors, each having 3 grooves that run the length of the tooth. They communicate vocally and by foot-stamping.

New World porcupines

19

They are distinguished from the Old World porcupines in that they have rooted molars, complete collar bones, entire upper lips, tuberculated soles, no trace of first front toes, four teats, and a prehensile tail.

Chinchillas, viscachas

7

They are known to clean their fur and skin by taking dust baths, and are also used to study auditory systems, since their hearing range is similar to humans and their tympanic bullae are easily accessible.

Pacaranas

1

The extinct large dinomyids are thought to have occupied ecological niches associated with large grazing mammals due to their ability to compete with the native ungulates of South America, and disappeared after the formation of a connection to North America. The modern pacarana is only modest in size, considerably smaller than the capybara.

Cavies, maras, guinea pigs and capybaras

19

The domestic guinea pig, Cavia porcellus, now found worldwide in captivity, has been bred for meat for more than three thousand years in South America. During the period of the Inca Empire, from 1200 to 1532, selective breeding resulted in many strains of the guinea pig. Since the mid-1800s this animal has been used for laboratory research.

Agoutis and acouchis

13

Agoutis have a very short tail, while that of acouchis is longer. They are fast and manueverable runners, resembling small antelope in some ecological and behavioral traits.

Pacas, gibnuts or majás

3

Pacas originated in South America and are one of the few mammal species that successfully emigrated to North America after the Great American Interchange, 3 million years ago. They are eaten by people in Belize, where they were served to Queen Elizabeth II.

Chinchilla rats or chinchillones

3

These rodents may be colonial. They are probably herbivorous, but their diets, like most other aspects of their biology, are poorly known.

Tuco-tucos

67

The common name, "tuco-tuco", comes from the "tuc-tuc" sound they make while they dig their burrows. While the processes behind its diversification are unknown, it has been suggested that they are among the most diversely speciated genus of mammals, largely due to chromosomal rearrangements and rapid speciation since their appearance in the late Pliocene or early Pleistocene era. Their chromosomal diversity is so impressive because their diploid numbers range from 10 to 70.

Spiny rats, hutias, and coypus

78

Most species have stiff, pointed hairs, or spines, that presumably serve for protection from predators. Many echimyids can break off their tails when attacked, however they do not regenerate, so the tactic can only be used once in an individual's lifetime.

Degus or coruros

15

Their name derives from the wear pattern of their teeth, which resembles a figure 8.

Jerboas

33

Their anatomy is more attuned towards erratic hopping locomotion, making use of sharp turns and great vertical leaps to confuse and escape predators, rather than for sustained hopping over long periods of time.

Birch mice

19

They are mouse-like jumping rodents, formerly classified alongside the jerboas and jumping mice until phylogenetic evidence indicated all three of these belonging to distinct families.

Jumping mice

11

Their tail makes up about 60% of its body length and is used to gain balance while jumping, and their cheeks have pouches. The Sichuan jumping "yeti" mouse (Eozapus setchuanus) from China can be identified by the ‘Y’ marking on its belly.

Mouse-like hamsters

10

They are not true hamsters, but represent an early split from the rest of the mouse-like rodents, and have been referred to as living fossils. They were once thought to be hamsters based on the shape of their molars, but they lack the cheek pouches, flank glands and short tails of the true hamsters.

Hamsters, New World rats and mice, muskrats, voles and lemmings

608

Their reproduction is characterized by large litters and short interbirth intervals. Most of them are able to breed when they are just a few months old, and the females often have a postpartum estrus and mate shortly after giving birth.

(True) mice and rats, gerbils, spiny mice and crested rats

1383

They are the largest family of mammals. They probably evolved from hamster-like animals in tropical Asia some time in the early Miocene, and have only subsequently produced species capable of surviving in cooler climates. They have become especially common worldwide during the current geological epoch, as a result of hitching a ride commensally with human migrations.

Climbing mice, rock mice, white-tailed rat,Malagasy rats and mice, swamp mice and pouched rats

68

Given their range of food habits, it is apparent that nesomyids as a group, and in some cases even individual nesomyid species, occupy several trophic levels, including those of primary, secondary, and tertiary consumer.

Spiny dormice and Chinese pygmy dormice

3

They are not true dormice, and can be distinguished by the distinct shape of their infraorbital canal and by the presence of multiple openings in the palate of the skull.

Mole rats, blind mole rats, bamboo rats, zokors

37

These rodents were thought to have evolved adaptations to living underground independently until recent genetic studies demonstrated they form a monophyletic group. They dig extensive burrows, which may include storage chambers for food, latrine chambers, and breeding nests. They are generally solitary animals, and do not share their tunnel complexes with other individuals.

Mountain beaver

1

Mountain beavers have an unusual projection on each molar and premolar tooth, which is unique among mammals and allows for easy identification of teeth. This projection points toward the cheek on the upper tooth row, but points toward the tongue on the lower. They do not fell trees, build dams, live in lodges, or communicate by tail slappings

Dormice

29

They are unique among rodents in that they lack a cecum, a part of the gut used in other species to ferment vegetable matter. Their dental formula is similar to that of squirrels, although they often lack premolars.

Tree squirrels, flying squirrels, chipmunks, prairie dogs and marmots

279

Tree and flying squirrels are also essential in the regeneration of forests around the world through their seed dispersal activities. This is not only because seeds are left in the feces of these animals but also because of the caching habits of many squirrels.