Mammalogy, lecture 9

Insectivora, Macroscelidea, Scandentia, Dermoptera

Reading: Chapter 11; pp. 194-204

I. Introduction

A. These 4 orders (Insectivora, Macroscelidea, Scandentia, and Dermoptera) have had a confused and chaotic taxonomic history

1. All 4 orders were at one time placed within the Insectivora, which was a wastebasket grouping for these groups

2. However, all groups are highly diverse, and there is even a lot of diversity within the current Insectivora

a. Often, this means that more splitting can be expected

II. Insectivora (65 genera, 439 species)

A. Six highly diverse families are placed in this order

1. Hedgehogs and gymnures (Erinaceidae), tenrecs and otter shrews (Tenrecidae), shrews (Soricidae), moles and desmans (Talpidae), golden moles (c\Chrysochloridae, and solenodons (Solenodontidae)

B. Most of their morphological characteristics are considered to be primitive and common to the earliest mammals

1. However, some obviously have rather specialized lifestyles

a. Moles

b. Hedgehogs and tenrecs

c. Shrews are probably most similar to early eutherians

C. No key character or set of characters defines this group

1. Almost always a key sign of trouble in defining a group, and a potential sign of reassignment of members of the taxon

2. Tend to be small to medium sized

3. Pentadactyl, with generalized plantigrade locomotion

4. External ear and eyes usually small or may be absent

5. Small braincase and brain with smooth cerebral hemispheres

6. Also have primitive dentition

D. Fossil history: very diverse, with about 150 described genera

1. Basically, any fossil eutherian not assigned to another order is assigned to the Insectivora (Butler, 1972)

2. Earliest known insectivore from the Cretaceous, in North America, ~100 mya

3. Oldest members of recognizable families (shrews and moles) from the Eocene, ~50 mya

E. Economics and conservation: of little economic importance

1. Several species are considered threatened or endangered due to habitat loss

a. These are all tropical species

F. A review of some of the families

1. Erinaceidae--the hedgehogs and gymnures (7 genera and 21 species)

a. Exclusively Old World (Africa, Europe, Asia)

b. Little spiny guys with a cult following in the pet trade (hedgehogs)

c. Gymnures do not have spines

d. Both are omnivorous

e. Hedgehogs perform self-anointing behavior (sexual attractant, reduce parasites, clean spines, or protection from predators (give example of predator protection))

f. Desert hedgehogs estivate during the summer

2. Talpidae--the moles (17 genera, 42 species)

a. Found throughout Europe, Asia, and North America (north to southern Canada)

b. Fossorial with fusiform body, short powerful limbs, smooth pelage

c. Ear pinnae reduced or absent

d. Eyes very small

e. Humerus short and broad, feet permanently rotated outward for digging

f. Most people never see moles--rather, they see the molehills

g. They eat mostly invertebrates

3. Tenrecidae: very diverse

a. Some look somewhat like large shrews, others like moles, others like hedgehogs, and the otter shrews look something like river otters

4. Soricidae: the shrews (23 genera, 312 species)

a. Largest group of insectivores, although taxonomy is confused

b. These are generally very small

i. Adult pygmy white-toothed shrews and pygmy shrews weigh ~ 3g, ~35 mm long, two of the smallest mammals in the world

ii. Most shrews, however, weight ~ 10-15 g, ~ 50 mm

c. Most have a pointed snout and small eyes

d. They are mainly insectivorous

e. They are often associated with water or moist habitat

f. They may enter torpor, but do not hibernate and are of course too small to migrate

i. Therefore, most of them forage throughout the year

g. They also secrete toxins

h. They also use high-frequency sounds for interspecific communication, orientation, and to detect prey

5. Other groups: Chrysochloridae (golden moles; burrowers), Solenodontidae (two species, one in Cuba, one in Dominican Republic and Haiti, large, reach 600 mm, produce a toxin in submaxillary glands, may use echolocation to navigate, and both are endangered)

III. Macroscelidea: the elephant shrews (4 genera, 15 species)

A. Sometimes included in the Insectivora

1. However, recent evidence shows that they are different enough to deserve their own order

B. Found only in central and eastern Africa to southern Africa, with one North African species

C. Occupy diverse habitats, including desert, brushland, plains, forests, rocky areas

D. Terrestrial and diurnal

1. Become somewhat nocturnal during hot weather

E. Feed on insects primarily, also on plant and animal material

F. Morphology

1. Have long, flexible, highly sensitive snouts

2. Large eyes and ears

3. Pelage is long and soft

4. Hind legs are longer than forelegs--look somewhat like kangaroo rats in this way

a. This allows for bipedal locomotion when alarmed

5. Size from 95-315 mm

G. Fossils: known from Oligocene (37-24 mya) and onwards in Africa

H. Economics and conservation: some species are eaten, some are used in research (one species gets naturally-occurring malaria)

IV. Scandentia: the tree shrews (one family, 5 genera, 19 species)

A. All are in family Tupaiidae

B. Considered to be the most primitive living primates

1. Because of this, they’ve been intensely studied and debated

2. Also probably because of this, their taxonomic placement and evolution has been subject to much debate

3. Currently they are considered as a lineage distinct from primates and insectivores

C. Found only in India, southern China, and Philippines through Borneo and Indonesia (Oriental faunal region)

1. Found in forests from 0-2400 m elev

D. Diurnal and omnivorous

E. They are not shrews

F. Morphology

1. Superficially resemble squirrels

2. Maximum total length is 450 mm, but half of this is tail

3. Characteristics that resemble those of primates

a. Large braincase

b. Various anatomical features

G. Fossils from mid-Miocene of India, ~15 mya

H. None are considered endangered or threatened (despite continuing loss of forested habitat), and none are economic importance

V. Dermoptera: The flying lemurs (actually, gliders) or colugos (single family, 1 genus, 2 species)

A. Taxonomic history of these is also confused

1. Have been grouped with bats, insectivores, and primates

B. The Philippines colugo found only in the southern Philippines

1. Malayan colugo in Indochina, Malaya, Sumatra, Java, Borneo, and other small islands near Sumatra, Java, and Borneo

C. Primarily nocturnal and completely arboreal

1. Feed on flowers, leaves, and fruits

2. They are extremely efficient gliders

a. They have an extensive patagium, extending from neck to digits of forelimbs, along sides of body and hind limbs, and enclosing the tail

b. They also have a keeled sternum, like birds and bats

c. They are about a half meter long, but lose less than 10 m for 100 m of gliding, showing how efficient they are at gliding

d. They are helpless on the ground

D. Fossil history seems uncertain: some fossils from the late Paleocene (~55 mya) in North America and from early Eocene (~50 mya) in Europe, but nothing found in Asia

E. Neither species considered threatened or endangered, but habitat loss to logging and farming is extensive

1. Hunted for fur and food (although I did not notice this for the Philippine colugo)