metazoa17

Jamaican fruit bats (nominate race, Artibeus jamaicensis jamaicensis). Cueva de la 22, Cabo Rojo, south-western Puerto Rico.

Mammals are the only modern synapsids and, in many respects, are the most evolved metazoans on Earth. The group is very ancient and probably evolved from early diapsids during the Triassic Period.

Like most reptiles are even today, the first mammals were egg-layers. The most ancient forms were tiny, skulking creatures, probably similar in morphology to modern shrews. They scurried over the leaf litter of forests, 210 million years ago, in search of insects and other invertebrates that made their prey. For another 150 million years from that time the rulers of the planet where the diapsids, especially the majestic archosaurs like crocodiles, sauropods, ankylosaurs, theropods, stegosaurs, ornithopods, ceratopcians, and pterosaurs before which the insignificant furry mammals of the time cowered in fear of being devoured. (Until after the Cretaceous Period, the largest known mammals were the size of modern dogs and cats). However, 65 million years ago, the rule of the archosaurian diapsids - save for the crocodiles and birds - came to an end in the geological blink of an eye, allowing Earth to be claimed by the mammalian dynasty that dominates the World to this day, and that is rivaled in its success only by that of birds themselves.

As is the case with every distinct taxon, mammals have a series of morphological traits that distinguish them as such. Hair seems to be one of such traits. This integumentary tissue derived from reptilian scales and composed of cheratin, serves the purpose of thermal insulation. However, some species, like most cetaceans, have secondarily lost all their fur in favor of an insulating layer of blubber under their skin. (Some of the extinct pterosaurs had a fur-like cover on their bodies, but these structures were only an instance of convergent evolution, homologous to mammalian hair).

All mammals have a specialized muscle wall separating the bowels from the lung and heart cavity, and which aids in breathing: the diaphragm. They lack cervical ribs, have a single paired bone in the mandible (the "dentary"), and an inner ear structure derived from the remaining mandibular bones. Mammals possess a single set of permanent teeth. (Diapsid teeth - when they are present - are shed and replaced throughout the animal's life). Also, mammals possess two occipital condyles, knobs at the base of the skull that interlock with the first vertebra. All other vertebrates have only one occipital condyle.

But the the most distinct characteristic of the group is the way they care for their offspring: all female mammals feed their young with the use of a secretion produced by specialized sweat glands (usually organized as mammary organs).

It should be noted that some of the traits mentioned above were probably shared at least with the therapsids (another, now extinct, clade of synapsids). The point in mentioning this is that it is not very clear what a mammal really is if one compares them with the other synapsids.

Although most modern synapsids have good eyesight, the vast majority of species have more keenly developed auditory and olfactory systems, this last perhaps rivaled in efficiency only by those of some reptiles, like snakes. Most mammals lack color vision, with the exception of higher diurnal primates to include us. As a matter of fact, in higher primates the sensory trend has been reversed, since our senses of smell and hearing are rather poor, if compared to those of most other mammals. But the last two senses mentioned allow their owners to find their way in poorly-lit areas and, indeed, most mammals are creatures of the night.

There are three subclasses within the modern Synapsida. One is Monotremata: the only extant egg-laying mammals, represented today by the platypus and a few species of echidnas, all Australasian in their present distribution. Instead of delivering milk though nipples, female monotremes exude it through specialized skin patches on their bellies and the babies lick it off their mother's fur. Like reptiles and birds their intestinal, urinary and reproductive passages end in a single external opening: the "cloaca" or "vent".

The next subclass is Marsupialia, existent today in Australia and its islands, as well as in the Americas. (A number of originally South American species entered and further evolved in North America after the emergence of the Isthmus of Panama, approximately two and a half million years ago). Marsupials include well-known species like opossums, Tasmanian devils, bandicoots, and kangaroos. Their young are born in an embryonic stage, and are usually held safe in a sort of pouch (in Latin, "marsupium") during their first stages of infancy. Marsupials mothers possess nipples, which confer the developing young the advantage of holding on to something while they suckle.

And, finally, there are the most advanced mammals of all: Placentaria. These feed their offspring while they are still inside their mothers' uteri by means of a marvelous organ called the "placenta". This device attaches to the uterine wall of the mother, and to the fetus by means of an umbilical chord. Inside the placenta the capillaries of mother and fetus grow in such close proximity than respiration, feeding, and excretion can be realized without actual intermingling of the bloods of both. The importance of this anatomical arrangement is that by keeping the blood flows of the mother and fetus separated, the immunologic system of the first does not attack and destroy the second. It must be remembered that half of the fetuse's genes come from its father, which the mother's body would recognize as alien. Female monotremes and, for that matter, female reptiles avoid such problem by encasing the embryo in a shell and then expelling it from their bodies. Marsupials achieve the same by giving birth to a weakly developed fetus before the mother's immunologic system destroys it.

Placentalians are the most successful of mammals, and the most varied of their kind. Their babies, having been pre-nourished by the placenta, often for months, are born in a much advanced stage than those of monotremes and marsupials. In turn, that has "freed" them to evolve anatomical features that make them the most morphologically varied of their entire kind.

Altogether, there are about 4800 species of living mammals known to date. They range in size from the 10 centimeter-long, 1.3 grams Etruscan shrew to the 33 meter-long, 172,000 kilogram blue whale, which is the largest living metazoan.

Short of being able to breathe underwater, mammals have conquered all environments on Earth, and they exist in a bewildering variety of shapes, sizes, and lifestyles. There are minute species of mice and shrews a few grams in mass, as well as monsters weighting thousands, and even tens of thousands of kilograms, like rhinoceroses, elephants and whales. There are herbivores like antelope and deer; seed eaters like rats and agoutis; insectivores like pangolins and solenodons; fruit eaters like marmosets and mangabeys; fierce carnivores like tigers and quolls; extremely specialized feeders like giant pandas and tamanduas; omnivores like raccoons and boars. Some are very slow-moving species, like sloths and lorises; others are the fastest creatures on four legs, like pronghorns and cheetahs. They live in the water, like manatees and dolphins; in both water and land, like fur seals and platypuses; on the highest mountains, like chamois and pikas; in rain forests, like howler monkeys and okapis; in deserts, like oryxes and fenecs; on arctic ice shelves, like polar bears and arctic foxes; underground, like moles and naked rats; high in the trees, like martens and indris. And from those trees bats flew into the air.

This is one of the most ancient orders of extant synapsids. Formerly placed in the now defunct order Insectivora, most species are small and feed mostly on invertebrates, especially insects. The living species are grouped into four families. Two of them, the shrews and the moles, range widely in many parts of the world.

Two other families are modernly endemic to the West Indies. One of them Nesophontidae, contains the West Indian shrews. They inhabited the Cuban, Hispaniolan, and Puerto Rican insular banks, but the family is now extinct. All known species belonged to the genus Nesophontes. Interestingly, species of Nesophontes that lived in the absence of similar insectivores, as was the case with the Puerto Rican form, grew to large size and occupied the same ecological niche as the large, extant insectivores of Cuba and Hispaniola.

The other family, Solenodontidae, survives as two species of Caribbean giant shrews, one in Cuba (Solenodon cubanus), the other in Hispaniola (S. paradoxus). Both are about 36 centimeters in length, plus a 25 centimeter-long tail, and weight about 1 kilogram in weight. The Cuban species is slightly larger than the Hispaniolan. Their common name, at least in Cuba, is "almiquí" (pronounced al-mee-KEE), plural "almiquíes" (al-mee-KEE-ehs).

Cuban giant shrew, Solenodon cubanus. Alejandro de Humboldt National Park, eastern Cuba.
Notice the powerful front claws used for digging and rooting for prey.
(Photographs courtesy of Dr. Julio Genaro).

Solenodontids seems to be of North American origin. The surviving species are relict taxa inhabiting their islands in the absence of serious predation. The situation is now very different, and the introduction of feral mongooses, cats, and dogs has contributed to make this animals from uncommon, in the case of the Hispaniolan solenodon, to critically endangered, in the case of the Cuban species.

These animals exhibit the phenomenon known as "island giantism" and are, indeed, the largest members of their order. Resembling enormous shrews with shaggy coats, they possess a snout elongated into a short trunk. Their sensitive olfaction and hearing allow them to hunt for their prey consisting of earthworms, insects, lizards, snakes, and basically any other small animal that they can overpower. Their eyes are tiny and almost vestigial and, correspondingly, their sense of sight is very poorly developed.

Solenodons share with a few other members of their order a trait unique among living synapsids (save for the platypus): they are the only known venomous mammals. Indeed, their generic name translates into "grooved tooth". Their second pair of lower incisors have lengthwise indentations through which venom flows that helps paralyze their victims. Its effect on a healthy human is rather weak.

These fascinating mammals tend to be very ill-tempered, flying into a rage with very little provocation. However, they are rather slow and clumsy and, when surprised in the open (not likely, since they are almost strictly nocturnal) they are easily cornered.

Hispaniolan giant shrew, Solenodon paradoxus. Bahoruco Mountains, south-western Dominican Republic, Hispaniola.
(Photographs courtesy of Mr. Eladio M. Fernandez).

The terrestrial mammalian fauna of the Antillean region has never been very rich and is, indeed, extremely meager compared to the panoply of species found in the continental Neotropics. New World monkeys, bats, ground sloths, insectivores, and rodents large and small comprise the greater part of what is known in the way of native terrestrial mammals in the Antilles, and most of them are known only from their fossils. By far, most of them are or were nocturnal creatures that go about after nightfall as they feed on insects, reptiles, or plant material.

Because the West Indies are oceanic islands, they lack many groups of terrestrial organisms which are spread far and wide in the American continents. Only those which - like reptiles - could withstand long periods of time without food and water, due to impermeable skins and low metabolisms were able to cross the ocean barriers with relative success. Flying organisms also have a decided advantage, since they can fly to the islands, often in a matter of mere hours. Many insects and birds can take that journey. And then there is another group that is able to accomplish the same feat...

This section of the class has more species in these islands than all others put together, partly for being the only mammalian order that developed the capacity for true flight: Chiroptera. Such are the bats, and today as before they are the most successful group of furry creatures in the islands of the Caribbean. (With almost 1000 species described to date they are, in fact, the second largest order of mammals, after rodents).

Similar to insectivores in several aspects, bats seem to be close to the basal group of synapsids that gave rise to colugos (the "flying lemurs" of Asia - order Dermoptera) and, perhaps surprisingly for many people, to primates - lemurs, monkeys, apes... and us.

Unlike birds, which achieved the power of flight by way of specialized scales (feathers) attached to their arms and vestigial fingers, bats did the same through a very different means. A bat's wings are actually its hands, which are very similar to ours as far as having the same main bones, yet have extremely elongated and slender fingers. These are interconnected by a thin layer of skin which stretches taut when the animal extends its arms and fingers, thus serving as the surface that produces lift as these mammals fly.

Long-tongued bat, (southern Lesser Antillean race, Glossophaga longirostris rostrata). Layou Valley, south-western Saint Vincent, Lesser Antilles.

A bat's wings are elongated hands and fingers over which spreads a thin membrane of skin.

A Jamaican fruit bat (nominate race, Artibeus jamaicensis jamaicensis), takes to the air. Balcones Cavern, Florida, central Puerto Rico.

In a manner similar to a bird, a bat's thrust as it flies is provided by the comparatively enormous chest muscles. And also like many birds, the smaller bats need proportionally huge amounts of food in order to m maintain their frenetic and highly expensive metabolisms. Indeed, some of the smaller species that live in high latitudes need to resort to hibernation during the winter months, as food supplies disappear for months.

Although bats are not particularly fast fliers - most flying birds greatly surpass them in speed - they can be extremely agile in flight. Many species can dramatically change direction in a space no wider than their own wingspan, maneuvering, twisting and turning in almost impossible curves and angles. Among the birds, only hummingbirds are better than bats when it comes to aerial acrobatics.

The bodies and physiologies of bats are adapted not only for flight, but also for another peculiarity, shared only with a few other synapsids (modern sloths, for example). When resting, a chiropteran usually does so facing head down from its perch. The posterior extremities have rotated almost 180°, so its knees point backwards and the soles of its feet face forward. With few exceptions - like vampires and some New Zealand bats - the legs and feet are too weak to allow the animal to walk horizontally for long periods of time. The tendons in the ankles and toes work in such a way that they automatically lock the claws unto the perch as the animal hangs from it, without any investment of energy. In fact, a bat has to flex its legs muscles to let go of its substrate, instead of doing the opposite, as in most mammals.

A bat's circulatory systems have also adapted to send blood through the vessels in a head-down position. This arrangement prevents the fluid from rushing to the head when the animal perches.

Being able to hang down from mostly inaccessible perches grants most bats a great deal of protection from predators. However they still fall prey especially to birds like owls, falcons, and hawks, which sometimes wait near the entrance of caverns and wait for the mammals to exit or return, in order to pounce on them.

Like all mammals except the monotremes, bats give birth to life young, in most case only one, two at most. The females of many species carry their babies for a few days after birth while they forage for food. This is not an easy feat, considering that the offspring may weight as much as a third as the mother.

Bats are divided into two suborders. The Microchiroptera ("lesser bats") are divided into 16 families, and are Cosmopolitan in distribution, inhabiting every continent save for Antarctica, as well as many oceanic islands around the world. The Megachiroptera ("greater bats") belong all to a single family, Pteropodidae. They are an exclusively Old World group (mostly Paleotropical) and live in Africa, Asia, Australia, and in the continental and oceanic islands that surround them. They are commonly known as "fruit bats" and "flying foxes", and some species of Pteropus are the largest in their entire order, with wingspans of almost two meters. When considering only the etymology of the terms, this division results somewhat artificial, since some microchiropterans are quite large, while a number of megachiropterans are almost tiny. However, the smallest known mammal is indeed an Old World microchiropteran: Craseonycteris thonglongyai, only a couple of grams in weight.

I should be noted that the phylogenetic relationships between megachiropterans and microchiropterans have not been definitively solved, and the two groups could actually represent a case of convergent evolution. In that case, pteropodids (the flying foxes) might not be true bats at all, but members of a mammalian order all by themselves.

Most microchiropterans are insectivores, although a good number of them feed mainly on nectar, pollen, or fruits. (These last may be locally called "fruit bats", although they are not related to the Old World species of the same name). A few are carnivores that prey on fish, frogs, lizards, small birds, and even other bats. A small group of Neotropical microchiropterans have a very specialized diet that makes them the only true mammalian parasites known to date (and, for that matter, the only vertebrate parasites of man). These are the vampires of Central and South America, belonging to the genus Desmodontus.

Compared to the varied diets of microchiropterans, most megachiropterans feed mainly on fruits. Often aggregating in large colonies which roost on exposed branches, they may fly long distances in order to reach favored fruit trees in different areas, depending on the fruiting season of each species of tree.

The 60, or so, species of bats native to the West Indies range in size from diminutive creatures you can close a fist around, like those of the genus Tadarida and Molossus, to the Neotropical fishing bat, Noctilio leporinus, which has a wingspan that might reach half a meter. Some have very specialized diets of insects, nectar, or fruit. Others are omnivorous.

Some species, like the Jamaican fruit bat, are widespread in the Antilles and even in the continent. Other species have much more restricted distributions, and are even endemic to single or related insular banks, like the Jamaican leaf-nosed bat, Phyllonycteris aphylla, the Puerto Rican red bat (Stenoderma rufum), the Bahamian funnel-eared bat (Chilonatalus tumidifrons), and several species in the Lesser Antillean Guadeloupan island bank.

Bats are extremely important to the ecosystems where they belong. Insectivorous species keep a tight control upon their prey's numbers. Also, the species-richness of many mesic forests in the Antilles is largely due to these mammals. Nectarivorous species pollinate flowers as they feed from them. Fruit-eating species, like those of the genus Artibeus, help disperse seeds far away from the parent tree, either by excreting them in flight after they pass unharmed through their guts within minutes after consumption, or by simply flying off with ripe fruits in their mouths, discarding the seeds after eating the juicy parts elsewhere. Sometimes, in a forest clearing caused by a fire, a landslide, a hurricane, or man, a group of shrubs or trees of the same species is seen extending for several meters, either in a straight line or in a curve. Upon closer investigation, one can realize that such trees - frequently a species of Ficus, Piper, or Schlefflera - produce fruits that are a favorite of one or another species of bat on that island, and then can deduce that one of the flying mammals flew in such a pattern over the clearing, years before.

Several species of Antillean bats roost in caverns, and their colonies may at times be more than a million-strong. In the West Indies and elsewhere, these assemblages constitute the largest concentrations of mammals to be found on Earth.

Since these colonies are often composed of multiple species, these partake of the available space by occupying different parts of the cavern, and the peaks of their nightly emergence varies by species, from before actual dusk to several hours after sundown. This temporal arrangement helps the entire colony to avoid a "traffic jam" at the mouth of the cave. It also reflects dietary preferences for each species: many insects are easier to hunt during their own peak of activity at dusk, while pollen- and nectar feeders rely on the cover of darkness during the deep night, as their hover in relatively vulnerability around fruits and inflorescences.

Bats are also known for their echolocation. That is the capacity to find their way around by hearing and without the use if sight (although, contrary to a popular myth, bats are not blind).

Mixed flock of bats, probably Pteronotus quadridens and Brachyphylla cavernarum, in a cavern, Cabo Rojo, south-western Puerto Rico.

As they leave their shelters in huge numbers their echolocating apparatus helps them to avoid crashing into surrounding objects and one another.

Echolocation is not exclusive to bats. It has also been developed in other groups of animals, particularly cetaceans (whales and dolphins), some insectivores, oilbirds, and some insects. Even among bats themselves, the phenomenon is not universal: only microchiroterans echolocate. The Old World's fruit bats do not, and depend much more on sight and smell than on hearing, to find food sources and mates, and to avoid danger. The fact that they cannot use hearing to find their way about is hinted at by the fact that they usually roost in open spaces, like tree branches, where they can see where they are going.

Many microchiropterans have a modified flap of skin, the "nose leaf", with which they can focus and direct chirps, squeals, and clicks, most of them beyond the range of human hearing. The sound waves bounce off the surface of objects, and are received by highly sensitive hearing systems in the bats' ears. The hearing apparatus is often modified in a way similar to the nose, with a convoluted flap of skin (the "tragus") inside the external ear itself. Such devices in turn focus and amplify the sounds that reach their inner ears. With echolocation, bats gather a huge amount of information on the distance, position, size, speed, and texture of everything that surrounds them. In fact, the entire head of many species of microchiropterans is modified for hearing, being covered in wrinkles, flaps of skin, hair tufts, and perpetual grimaces on their lips, all of which work to better emit and gather sound, and which gives them the appearance of gargoyles. (Going back to the Old World flying foxes, they derive their name from the fact that, not depending as much on their sense of hearing, their heads do not show such extravagant morphologies and instead have a rather generic, somewhat canine appearance).

Whatever their individual aspect, bats are astonishing, marvelous, beautiful creatures...

Sadly, a number of of Antillean bats have suffered due to the destruction of habitat, pollution, or are simply destroyed due to people's prejudices against them. While no species is known to have gone extinct, education and the protection of natural areas remain key elements in their continued survival.

This family contains only one genus two species, and the one inhabiting the Antilles is the greater fishing bat, Noctilio leporinus. Its name means "hare-like nocturnal creature" for its long ears and hare-lipped face.

These bats show the extraordinary habit of capturing fish from the surface of rivers, lakes and even the ocean by snatching them with the long claws of their feet. After than they transfer the prey to their mouths and will usually return to a roost to chew on their meal. Their daytime lairs are small caves and trees near their hunting gounds and can be found from a distance by their strong, pungent smell.

Greater fishing bats, (Antillean race, Noctilio leporinus mastivus). Portland Ridge, south-central Jamaica.
(Photograph courtesy of Mr. Joseph Burgess).

The Cosmopolitan family Molossidae (free-tailed bats) includes several very small species of genera like Molossus and Tadarida. Mainly insectivores, these forms often roost close to human habitations, though they can likewise be found in caverns and other such natural refugia. Molossids are usually good climbers. Their long and narrow wings require them to attain some speed before the become airborne, which is the reason why the take off their lairs by dropping vertically from their perch before they extend their wings.

Velvety free-tailed bat (Puerto Rican bank race, Molossus molossus fortis). El Yunque National Forest, north-eastern Puerto Rico.

These tiny bats often roost in holes and crevices in buildings.
(Photographs courtesy of Mr. Alfredo Colon Archilla).

Molossus molossus fortis arriving and hiding in its daytime lair in a building.
Camp Santiago, south-eastern Puerto Rico.

The family Mormoopidae might be related to phyllostomids (see below). Unlike them, they lack a well-developed nose-leaf. However, they can be distinguished morphologically by their folded lips which give them the appearance of being pouting. Highly gregarious, mormoopids sometimes congregate in caverns in immense colonies, often mixed with other species. Their common name of "moustached bats" derives from the tuft of bristly hair on the snouts of many species. Most of them are small, and are exclusively insectivorous.

Some species, like the sooty moustached bat, Pteronotus parnelli, leave their lairs every evening and return to them every morning in huge formations. Flocks of them snake from the entrance of caverns at dusk before dispersing to look for their nightly repast of flying insects. This and related species usually stay under the forest canopy, seldom venturing into open areas.

Sooty moustached bat, (Greater Antillean race, Pteronotus quadridens fuliginosus), male. Cueva de la 22, Cabo Rojo, south-western Puerto Rico.

The tiny Pteronotus bats form aggregations of hundreds of thousands, and even millions, in some caverns of the West Indies.

At dusk, hordes of them leave their diurnal retreats in living, airborne streams, and then disperse for their nocturnal feast of flying insects.

They keep a tight control on their insect prey and, thus, are a very important component of their karstic ecosystems.

A number of bats in the Antilles belong to the family Phyllostomidae, the "leaf-nosed bats". The name derives from the fleshy structure above theis noses, which allow them to emit beams of sound as they echolocate. The family is found exclusively in the americas, as is well representedin the West Indies, where several subfamilies are found . These include Stenodermatinae, Phyllostominae, Glossophaginae, and the Antillean endemic Brachyphillinae. Several species of Artibeus, Brachyphylla, and Glossophaga feed mainly on plant material (these last mainly on nectar and pollen).

Artibeus jamaicensis is perhaps the most widely distributed bat species in the Caribbean, being found in all the islands and in a wide variety of habitats. This species usually roots in caves and tree holes, but is also known for biting the main nerve of large leaves until it tents, creating thus a shelter against sun and rain.

Jamaican fruit bats, (nominte race, Artibeus jamaicensis jamaicensis). Cueva de la 22, Cabo Rojo, south-western Puerto Rico.

Small groups that aggregate together normally consist of a male with a harem of several females. The male will defend its mates from other suitors.

In this apparent pair, the female, at the right, has a cub hanging from its chest.

One of the most common species of Caribbean bats, it was originally described from Jamaica (hence its name).

However, it is also found throughout the entire West Indian region, and in Central America and northern South America.

The term "fruit bat" applied to this species is also somewhat misleading, since it doesn't feed exclusively on fruits.

Jamaican fruit bats, (nominate race, Artibeus jamaicensis jamaicensis). Balcones Cavern, Florida, central Puerto Rico.

A female Jamaican fruit bat suckles her pup. Balcones Cavern, Florida, central Puerto Rico.

The Cuban race of the Jamaican fruit bat, Artibeus jamaicensis parvipes. Cueva de las Perlas, Guanahacabibes Peninsula, western Cuba.

Long-tongued bat, (southern Lesser Antillean race, Glossophaga longirostris rostrata). Layou Valley, south-western Saint Vincent, Lesser Antilles.

Notice the nose leaf over the snout. Endemic to the island banks of Saint Vincent and Grenada.

The tip of the long tongue of this species is covered in bristles that form a kind of brush with which it laps up nectar and juices of ripened fruits.

Lesser Antillean pig-nosed bat, (Puerto Rican race, Brachyphylla cavernarum intermedia). Cueva de la 22, Cabo Rojo, south-western Puerto Rico.

This large species requires mostly extensive and dark caverns to roost during the day.

Although widely distributed among the Lesser Antilles, it probably invaded them from the Puerto Rican insular bank.

In the other Greater Antilles, it is substituted by its sister species, the Greater Antillean pig-nose, B. nana.

Lesser Antillean pig-nosed bat, (Lesser Antillean race, Brachyphylla cavernarum cavernarum).

Waterhouse's leaf-nosed bat, Macrotus waterhousii. Portland Ridge, south-central Jamaica.
(Photograph courtesy of Mr. Joseph Burgess).

Waterhouse's leaf-nosed bats (Bahamian race, (Macrotus waterhousii minor). Grand Inagua, The Bahamas.
(Photographs courtesy of Mr. Joseph Burgess).

Buffy flower bats, Erophylla sezekorni. New Providence, The Bahamas.
(Photographs courtesy of Mr. Jopseph Burgess).

With more than 2000 extant species (almost half the number of modern mammals) this is the largest order of living synapsids. All have one trait in common: they are gnawers. They all have two incisors in each jaw, which grow continuously throughout their lives. These are followed by a gap in the jaw (the "diastema") behind which follow the premolars and molars. No rodent has any canines.

Four families of rodents are know from the Caribbean islands. Three of them are now extinct, including that Antillean endemic family Heptaxodontidae, found in the Lesser Antilles and in the Greater Antilles save for Cuba. This group includes some of the largest known members of their order, like Amblyrhiza inundata, of the Anguilla-Saint Bartholomew-Saint Martin paleoisland. This monstrous rodent weighted up to 200 kilograms, thus being about the size of a North American black bear.

The only extant family in the region is Capromyidae, locally known by the Taino Amerindian name of "hutías" (pronounced "uh-TEE-ahs"). Some of these animals resemble huge rats with rotund and cheeky faces, although they are only very distantly related to true rats and mice of the family Muridae. In fact, they are far closer kin of the South American agoutis and guinea pigs. Some species can be as large as a domestic cat.

The living representatives of the group are spread between two subfamilies: Capromyinae, in Cuba, Jamaica and The Bahamas, and Plagiodontinae, in Hispaniola.

Twelve species of hutias survive only in Cuba, with the genera Geocapromys, Mesocapromys, Mysateles, and the type genus of their family, Capromys; in Jamaica and The Bahamas, again with the genus Geocapromys; and in Hispaniola, with the genus Plagiodontia. Some species are agile tree climbers, (though they may still sleep in underground lairs or in crevices among boulders), and indeed feed on twigs, leaves, and fruits of the plants and trees in their environment. Some may occasionally feed on insects or small vertebrates.

As is usual with rodents, hutias are mostly nocturnal. However, they will go about their business during the day, if conditions warrant it.

The largest living species is the Cuban hutia, Capromys pilorides, which measures up to a total of 80 centimeters in length (including its 30-centimeter tail) and 7 kilograms in weight.

Cuban hutia, Capromys pilorides. Guantanamo Naval Base, Guantanamo, south-eastern Cuba.

Larger than a domestic cat, this is the biggest living member of this West Indian group.

An arboreal Hispaniolan hutias Plagiodontia aedium, peeks through the foliage. Pedernales, south-western Dominica Republic Hispaniola.

Hispaniolan hutias, Plagiodontia aedium. Pedernales, south-western Dominica Republic Hispaniola.

Hispaniolan hutia, Plagiodontia aedium. Bahoruco Mountains, south-western Dominica Republic Hispaniola.

Among all local chordate taxa, Antillean mammals suffered the most in the wave of extinctions of the post-Columbian period. Although endemic West Indian rodents are the most numerous living group after bats, most species are threatened and a good number is indeed already extinct, due to hunting by man, habitat degradation, and pressure from exotic animals.