The eight species of gymnures are found primarily in the rain forests of Southeast Asia, Gymnures are also called moonrats, and with good reason – they resemble rats much more than they
Trang 1most bizarre elaboration of a general phenomenon found in
the true moles, which have thousands of receptors arranged in
a structure called the Eimer’s organ on the snout Cortical
development of the brain is linked with the Eimer’s organ The
Eimer’s organ assists moles in navigating and foraging in their
tunnel networks
The fourth family in Soricomorpha, the Soricidae family,
contains the shrews, represented by 26 genera A very
suc-cessful mammalian family, shrews are found on every
con-tinent except Australia and Antarctica Soricidae also boasts
the world’s smallest living terrestrial mammal, the Etruscan
shrew (Suncus etruscus), which weighs 1.8 g on average.
Erinaceomorphia
The last of the new forms of Insectivora, the order
Erinaceo-morphia contains hedgehogs and gymnures The eight species
of gymnures are found primarily in the rain forests of
Southeast Asia, Gymnures are also called moonrats, and with
good reason – they resemble rats much more than they do
their much closer relatives, the hedgehogs The 16 species of
hedgehog are all well known for their spines, which are simply
stiff hairs hollowed and supported by keratin, and their ability
to roll into a ball as a defense mechanism
Scandentia
The five genera and 20 species of tree shrews (families
Tupaiidae and Ptilocercidae) are the only extant members of
the Scandentia The group is dispersed across the rain forests
of southern Asia and Southeast Asia and has a relatively long
fossil history (first found in the Eocene of Asia) Resembling a
small squirrel, weighing 45–50 g, tree shrews have an
elong-ated snout and a long, bushy tail Like true shrews, many
species are known to consume insects; however, the few
sci-entific studies that have been conducted on the family have
found that fruit is often the dominant component of the diet
Parental care is unusual, with the female giving birth to a
small number of young (one to three) and hiding them in a
nest In a pattern more common in antelopes, the female visits
the young to nurse and then leaves them lying in Maturation
is rapid, with independence from the mother at about a
month and full sexual maturity at 4 months Tree shrews are
enigmatic in their phylogenetic affiliations They have
vari-ously been assigned to the primates, flying lemurs
(Dermop-tera), and rabbits (Lagomorpha), with both molecular and
morphological analysis producing contradictory results
Dermoptera
Gliding, as opposed to true flying, is a mode of locomotion
that has evolved independently in a number of mammalian
orders The two living species of Dermoptera (family
Cyno-cephalidae), also called colugos or flying lemurs, are a relictual
group of gliders found today only in the forests of Southeast
Asia Not closely related to lemurs, the dermopterans first
appear in the fossil record in the Eocene of Thailand
Throughout their evolutionary history, only two families of
colugos have been described, one North American and the
other Asian Affiliations of the order are unclear, with some
paleontologists placing them as relatively close relatives to
bats: they are not related to lemurs despite their common
name The gliding membrane, or patagium, stretching over the
animal’s entire body, connecting along both sides of the tail to the legs, from legs to arms and from the arms to the neck, makes the animal look like a kite Despite their relatively large size, reaching a maximum size just under 2 kg, the colugos are spectacular gliders, moving more than 100 m from tree to tree
in the forest to reach the trees on which they feed The colugo diet is herbivorous but may include leaves, fruits, and flowers
Chiroptera
Bats represent the second most diverse order of mammals with
18 families, 202 genera, and 1050 species Two major sub-orders of bat have been distinguished, the Megachiroptera, also called fruit bats or flying foxes, and the Microchiroptera Bats come as small as 1.5 g with a wingspan of 15 cm (Craseonycteridae, Kitt’s hog-nosed bat) and as large as the flying foxes in the genus Teropus (Teropidae), which may weigh up to 1.5 kg and have wingspans of 2 m
The two suborders have long, independent evolutionary histories, although the very nature of their morphology, and in particular their fine, light bone structure, makes preservation unusual In contrast to modern diversity, sufficient fossil ma-terial has been found to describe just more than 30 genera The lack of fossil evidence has provoked repeated controversy and called into question whether bats are monophyletic or whether the fruit bats are actually more closely related to another group (primates are postulated because of shared evolution with megachiropterans of details of their neural pathways for vision) If this were the case, the remarkable flight structures would have to have evolved twice independ-ently Molecular data show relatively unambiguously that the two bat groups are monophyletic
Bats are the only mammals capable of true flight (as op-posed to gliding) The wing is formed by a thin membrane that stretches across the arms, elongated fingers, and along the body, forming a diaphanous umbrella-like structure, or pata-gium Like all flying animals, bats need wings that are at once light but strong The wings are greatly reduced in weight with muscles pulled in close to the body and bones reduced in size land volume Torsional stress is reduced by simplification of joints The remarkable flying abilities of bats ensure a global distribution, with bats often the only mammal naturally occurring on remote islands
Whereas birds monopolize diurnal aerial niches, bats are nocturnal specialists In some areas where birds and bats do not co-occur, bats may become more diurnal, providing thin evidence of competitive exclusion Flying at night, visual acuity is of relatively little value; nonetheless, all but one species of Megachiroptera rely on vision to navigate In con-trast, microchiropteran bats have evolved navigational tools that are independent of sight Using their larynxes, micro-chiropterans produce extremely high frequency sound that they emit through their nose or mouth The sound produced
by bats is referred to as ultrasonic because it is above the range that humans can hear The ultrasound bounces off both po-tential prey and obstacles and is received back at the large, elaborated ears of the bat Because the bat navigates using the sound that bounces back, this form of navigation is called echolocation
Despite their high specific diversity, patterns of repro-duction (in the few species that have been studied) all are
Mammals, Biodiversity of 691