mammalogy lecture #3 insectivora, macroscelidea, scandentia, and dermoptera

Mammalogy Lecture #3

Insectivora, Macroscelidea, Scandentia, and Dermoptera

Insectivores

The 4 orders we are considering now were once all grouped in the insectivora. The group was once, and continues to be a ‘garbage basket’ of families. Often, it is unclear where else these organisms belong.

An important question is: why do they end up in an assemblage like this?

Insectivores

1) It really has nothing to do with diet - some are herbivores, some have a cecum others do not.

2) Perhaps all are in some sense less derived than other mammals?

3) Perhaps their morphologies reflect arboreality?

Why are other groups easier to classify?

Insectivora

Erinaceidae: hedgehogs and gymnures

Tenrecidae: tenrecs and otter shrews.

Soricidae: shrews

Chrysochloridae: golden moles.

Solenodontidae: solenodons.

Talpidae: moles and desmans.

Insectivora

Morphologically, they appear to be less derived than other mammals. It is possible that they reflect the ancestral stock of eutherian mammals.

This is convenient because we often assume that the first mammals were small insect eating forms.

Insectivora: Morphology

Generally small. Pentadactyl w/ plantigrade locomotion. Rostrum tends to be long. Pelage often consists only of guard hair

(modified in some forms as spines). Pinnae small or absent. Small braincase w/ smooth cerebral

hemispheres.

Insectivora: Morphology Auditory bullae are absent - instead

there is a ring-shaped tympanic bone. Anterior vena cavae are paired. Testes usually abdominal, or if in

scrotum, then anterior to penis (as in marsupials).

Claoca is present in some. Jugal is reduced or absent. Pubic symphysis is reduced.

Blarina brevicauda

Insectivora: Morphology

Some insectivores retain the tribosphenic tooth.

Teeth are rooted, so do not grow throughout life.

Molars have 4 or 5 cusps and form either a V shape (zalambdodont) or W shape (dilambdodont) occlusal pattern.

Dental formula is often pleisomorphic 3/3, 1/1, 4/4, 3/3 = 44

Talpa & Potamogale

Cryptotis parva

Insectivora: Fossil History

Earliest insectivores data to the mid-Cretaceous (100MYA)

Recognizable soricids and talpids date to the Eocene (50MYA).

Zalambdalestes & Kennalestes from the Cretaceous

Erinaceidae

7 genera and 21 species. Hedgehogs have barbless spines while

gymnures do not. Found in the Old-World. Hedgehogs are nocturnal and mainly

terrestrial, or semiarboreal. They are omnivorous - invertebrates,

eggs, fruit, carrion.

Erinaceus sp

Cheekteeth of Erinaceus sp.

Erinaceidae

Spines in hedgehogs are soft at birth, and have not broken the skin. They harden a few weeks after birth.

In a defensive posture, the animal rolls up in a ball, using a band of muscle lateral to the ventrum - might this be similar to patagial musculature in gliders?

Erinaceidae

Hedgehogs also self-annoint. They rub saliva over their spines. Interestingly, there are reports of hedgehogs killing toads, and self-annoiinting with the parotid glands to produce ‘venemous spines.’

Erinaceus europaeus is the only insectivore to use hibernation. Others may estivate.

Erinaceidae

Gymnures do not have spines.

Closely associated with wetlands.

Phillipine moon rats have anal scent glands.

Talpidae

17 genera and 42 species, distributed throughout Europe, the Palaearctic, Asia, Japan, and North America.

Fossorial w/ consequent morphology:– fusiform– pinnae reduced or absent– small eyes– keeled sternum

Talpidae

– Extreme modification of the pectoral girdle and appendages - including rotation of the fore-feet.

Scalopus aquaticus

Upper & lower molars of Sorex vagrans (A&B) and Scalopus aquaticus (C&D)

Talpidae

Desmans are restricted to the Old World.– Eat aquatic invertebrates and fish– Some species have long, laterally

compressed tails.– Some evidence that they use echolocation

to locate prey.

Tenrecidae

24 species. 21 species of Tenrecs are found in Madagascar only (this is bad news), while there are 3 species of otter shrews found in west-central Africa.

There is extreme morphological variation in this group, w/ forms resembling hedgehogs, shrews, muskrats, and moles.

Tenrecidae

Bruce Patterson from the Field Museum in Chicago has been working furiously in Madagascar trying to understand the diversity and evolution of Tenrecs. Just within the last few years, they have discovered several new species. If you are interested in this group, you have a rich resource nearby.

Tenrec ecaudatus

Tenrec ecaudatus

Tenrecidae

Otter shrews (not surprisingly) look a lot like otters and are actually quite large.

Some Tenrecs can hibernate, and most have relatively low body temperatures.

The common Tenrec has as many as 32 offspring in a single litter!

Chrysochloridae

7 genera and 18 species, found in central and southern Africa.

These are the golden moles - they have iridescent fur. It is truly an amazing sight.

No pinnae, vestigal eyes. Convergent w/ Talpids, but forelimbs are

not rotated.

Chrysochloridae

They push soil w/ the snout, then push soil under the body with the limbs.

Claw on 3rd digit is enlarged.

Chlorotalpa sclateri

Chlorotalpa sclateri

Solenodontidae

2 species. 1 restricted to Cuba, the other to Haiti and the Dominican Republic (this is not good news).

They are large (TL = 600mm) Look like a cross between a rat and a

shrew. Omnivorous.

Solenodon paradoxus

Solenodon paradoxus

Solenodontidae

May be capable of echolocation - they produce high frequency clicking sounds. Has anyone recorded them w/ a bat detector?

Submaxillary glands produce toxic saliva, which flows into the bite via grooved 2nd incisor.

Soricidae

23 genera and 312 species. Generally small (3g - 100g). Organized into 2 subfamilies: Soricinae

and Crocidurinae. Soricinae are the ‘red-toothed’ shrews. Crocidurinae are the ‘white-toothed’

shrews.

Blarina brevicauda

Crocidura leucodon

Soricidae

Smallest shrews are Suncus etruscus and Sorex hoyi, while largest is Suncus murinus.

Most have short legs, are plantigrade. 2 forms have webbed feet: Nectogale

elegans and Sorex palustris. Small eyes, pointed rostrum, short dark

pelage.

Suncus murinus

Suncus murinus

Soricidae

Many produce a musky odor - which you will notice if we trap any this semester.

No zygomatic arch, no auditory bullae. 1st upper incisor is unique w/ apparent

2nd cusp.

Sorex vagrans

Soricidae

Most are insectivorous, although some are functionally omnivorous.

This brings up a number of interesting points:– why are shrews so small?– What are the consequences of small size

(note, they are incapable of hibernation or migration)?

Soricidae

Some use high frequency sound for communication, orientation, and prey detection - although this has not been studied extensively.

Many exhibit caravanning. Short lived. Often associated w/ moist habitats.

Macroscelidae

4 genera and 15 species of elephant shrews.

Central and eastern Africa. Insectivores to omnivores. Can move bipedally. Long, flexible snout, large eyes and

long ears.

Convergent w/ Dipodomys & Jerboa?

Macroscelidae

Size ranges from 50g to 400g. Hind-limbs longer than fore-limbs. Have audotory bullae and a zygomatic

arch. All but Rhynchocyon have functional

incisors.

Macroscelidae: Rhynchocyon chrysopygus

Macroscelidae

Molars are quadrituberculate, and occlusal surfaces are dilambdodont.

Possess a cecum. Fossil history dates to the Oligocene of

Africa.

Scandentia

Contains a singel family (Tupaiidae) with 5 genera and 19 species.

Have long been considered primates. It is important to realize that primates are a poorly defined group, w/ most of their distinguishing characteristics related to arboreality.

Scandentia: Tupaiidae

Restricted to Oriental faunal region. Mostly diurnal and omnivorous. Not all are arboreal, and they are not

shrews. Most scent mark. Resemble squirrels in general

morphology.

Tupaia sp.

Tupaia glis

Scandentia: Tupaiidae They resemble primates in that they

– 1 have a large braincase– 2 have a postorbital bar– 3 have scrotal testes– 4 similar structure of carotid and

subclavian arteries. Tribosphenic molars Unperforated palate. Lower incisors are procumbent and

used for grooming. Date to the Miocene of India

Tupaia glis

Dermoptera

These are the ‘flying lemurs’ or Colugos.

In the past, they have been classified with bats, primates, and insectivores.

There is 1 family (Cynocephalidae), 1 genus (Cynocephalus) and 2 species.

Dermoptera

Cynocephalus volans occurs in the Philippines, while C. variegatus occurs in Malaya, Sumatra, Java, Borneo, and nearby islands.

They weigh up to 2kg, and can glide at up to 25m/s which is very fast for a glider.

Dermoptera

Feldhammer claims they can glide 100m and lose only 10m in altitude. This is hooey.

They are very specialized arboreal folivores, with long gut retention times.

They feed only on newly emergent leaves of a few species of trees.

Dermoptera They have the most extensive patagium

of any glider. They have pectinate lower incisors. They have a keeled sternum. Your

author claims other gliders have a keeled sternum - I have never seen one.

Fossil history dates to Paleocene of NA, and Eocene of Europe (both for family Plagiomenidae). No fossils in Asia.

Colugo variegatus

Colugo variegatus

Crocidura leucodon

Cryptotis parva