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Mammalogy Lecture #3. Insectivora, Macroscelidea, Scandentia, and Dermoptera. Insectivores.
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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?
Erinaceidae: hedgehogs and gymnures Tenrecidae: tenrecs and otter shrews. Soricidae: shrews Chrysochloridae: golden moles. Solenodontidae: solenodons. Talpidae: moles and desmans. Insectivora
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.
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
Insectivora: Fossil History • Earliest insectivores data to the mid-Cretaceous (100MYA) • Recognizable soricids and talpids date to the Eocene (50MYA).
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.
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.
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.
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.
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.
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.
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.
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.
