In this article we will discuss about the classification of Mammalia.
Mammalia # Subclass Prototheria:
1. A cloaca is present into which open the rectum and the urinogenital sinus.
2. The vasa deferentia open into the urinogenital sinus.
3. The oviducts open separately into the urinogenital sinus. The ureters do not open in the urinary bladder but into the urinogenital sinus.
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4. Oviparous, ova with much yolk and meroblastic segmentation.
5. Mammary glands without nipples.
6. Male with a hollow tarsal spur.
Examples. Platypus, Duck-mole (Ornithorhynchus), etc.
Mammalia # Subclass Metatheria:
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1. The anus and the urinogenital sinus are surrounded by the common sphincter muscle. Except in kangaroos, a rudimentary cloaca is found in the females.
2. Two uteri and two vaginae are present. The ureters open into the bladder.
3. Ova small, cleavage holoblastic, yolk-sac large with villi; allantoic placenta usually absent.
4. Mammary glands have teats enclosed in the marsupium in which prematurely born young are carried.
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5. Brain without corpus callosum.
6. Lower jaw with an inflected angle. Examples Kangaroo, Didelphys, etc.
Mammalia # Subclass Eutheria:
1. Anus and urinogenital aperture usually quite separate.
2. The uteri are united to one. The ureters open into the bladder.
3. Small ova with little yolk and holoblastic segmentation.
4. The developing young is vitally connected with the mother by allantoic placenta.
5. Presence of corpus callosum in the brain.
6. Tympanic bulla is usually present.
Orders:
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The subclass Eutheria has been divided into following orders
Order Insectivora:
1. Terrestrial, rarely arboreal animals with plantigrade or semiplantigrade limbs.
2. The clavicles are present, except Potamogale.
3. The incisors are more than two in the mandible and the molars are tuberculated, rooted and enamelled.
4. Testes are abdominal.
Examples. Talpa (mole), Centetes, etc.
Order Chiroptera:
1. Flying mammals with the fore limbs specially modified for flight.
2. The ribs are usually flat.
3. One or two pairs of thoracic, usually postaxilliary mammae.
4. Penis is pendent.
Examples. Bats, Pteropus, Molossus, etc.
Order Xenarthra:
1. Number of teeth variable and without enamel. Grinders are numerous and pillar-like.
2. Feet provided with curved claws.
3. Posterior dorsal and lumbar vertebrae with an extra pair of zygapophyses.
4. Persistently abdominal testes.
Examples. Armadillos (Dasypus), Ant eaters (Myrmecophaga), etc.
Order Pholidota:
1. Body covered with intricately arranged horny scales with hairs between them.
2. Teeth entirely absent.
3. Jugal arch and clavicle absent.
4. Fore feet provided with strong curved claws.
Example. Manis gigantea (Scaly ant eater).
Order Rodentia:
1. Large, sharp, chisel-shaped incisor in each jaw and without canine.
2. A diastema is present.
3. The angular process of the lower jaw is well developed.
4. Lophodont premolars and molars.
Examples. Cavia, Oryctolagus (Rabbit), etc.
Order Carnivora:
1. The canine teeth are large, three incisors on each side of the jaw, cutting premolars and tuberculate molars.
2. The last upper premolar and the first lower premolar are modified as carnassial teeth.
3. The limbs have never less than four digits and are provided with claws.
4. Scaphoid, lunar and centrale in the carpus fused.
Examples. Dog (Canis), Bear (Ursus), etc.
Order Pgrissodactyla:
1. Hoofed, digitigrade animals, the digits never more than three.
2. Except the last one, all the, premolars are molarized.
3. The placenta is diffuse or cotyledonary.
4. Presence of a third trochanter in the femur.
Examples. Horse (Equus), Tapir (Tapirus), Burchell’s Zebra (Equus), etc.
Order Arteodactyla:
1. The axis of the foot passes through the third and the fourth digit.
2. Absence of a third trochanter in the femur.
3. True horn with a bony horn core present.
4. Usually with a gall bladder and ruminating stomach.
Example. Bos domestica (cattle).
Order Cetacea:
1. Aquatic, fish-like, naked animals without hind limbs.
2. Head is continuous with the body and the external nares are on the top.
3. A horizontally expanded caudal fin and often a fatty dorsal fin are present.
Examples. Whales (Balaena), Porpoises (Phocaena), etc.
Order Sirenia:
1. Short-necked, thick skinned, aquatic animals, naked or with very rare covering of hairs.
2. External nares are anteriorly directed and separate.
3. Caudal fin horizontally flattened; anterior limbs fin-like; the posterior limbs are absent.
4. Scapula long and narrow.
Examples. Sea cows, Manatus, Rhytina, etc.
Order Primate:
1. Plantigrade, usually pentadactyl animals with complete dentition.
2. The orbit is completely separated from the temporal fossa.
3. The cerebral hemispheres completely or almost completely cover the cerebellum.
4. The uterus is without horns and the placentation is metadiscoidal.
Examples. Macacus, Gorilla, Homo, etc.
Order Proboscidea:
1. A proboscis is present.
2. The ulna and radius permanently cross.
3. Pelvis with broad ilium and vertical in direction.
4. Clavicles absent. Example. Elephant (Elephas).
Classification of the order Chiroptera:
Bats are the only mammals, which possess the power of flight and are found throughout the world, even in the oceanic islands. Their fore limbs are modified as wings. Although surprisingly equipped with the specialised power of flight, the chiroptera, as an order is by far primitive and owes its origin to as far back as Palaeocene.
1. The wing is formed by a fold of skin, the patagium, which begins from the shoulder and extends along the upper margin of the arm to the thumb and from there to between the long fingers and to the legs along the sides of the body. In some cases the fold runs up to the tail.
2. The phalanges are usually reduced to two.
3. The pectoral girdle is strong and the presternum bears a slight keel.
4. The thumb is always clawed, ulna vestigeal.
5. The hind limb is short and weak, and with backwardly directed knee and all the five toes are clawed.
6. The maximum dentition is 2,1,3,3/3, 1, 3, 3.
7. The cerebral hemispheres are smooth or with a few convolutions.
8. The stomach is usually simple and never bears more than a short caecum.
9. The testes are abdominal or inguinal; the penis is pendent.
10. The uterus is simple, bicornuate or duplex.
The order Chiroptera has been divided into two suborders
Suborder Megachiroptera:
1. Fruit eating bats, usually of large size.
2. Crowns of the molar teeth smooth, marked with a longitudinal furrow.
3. The bony palate slightly narrows down backward and continues behind the last molar.
4. Pinna forms a complete ring at the base.
5. The tail is short or absent.
6. The pyloric part of the stomach is much elongated in most cases.
Distribution:
Tropical or subtropical regions of the new world.
Examples. Pteropus, Celebes, Notopteris, etc.
Suborder Microchiroptera:
1. Mostly insectivorous bats of small size.
2. Crowns of the molar teeth acutely tubercular, marked by transverse furrows.
3. Bony palate narrows down suddenly and does not continue behind the molar.
4. The second finger does not end in a claw and usually with one small phalanx only.
5. The pinna does not form a complete ring at the base.
6. The stomach is simple and the pyloric part not elongated. Distribution. Tropical and temperate regions of both hemispheres.
Examples. Rhinolophus, Anthops, Nyeteris, Atalapha, etc.
Classification of Carnivora:
Carnivores are mammals, which feed on other animals and most of them prey upon others and take their warm flesh. These are beautiful animals with keen senses and quick intelligence but at the same time they are most bold and fierce.
1. Almost all have well developed claws and the digits are never more than four.
2. The teeth are provided with roots, the canines are strong and sharp and some of the back teeth are modified for cutting.
3. The last upper premolar and the first lower premolar are modified as carnassial teeth.
4. The occipital and sagittal crest on the skull are strong.
5. The glenoid fossa is deeply concave and bounded by a large postglenoid process.
6. The tympanic bullae are large in most cases.
7. The stomach is always simple, the caecum is absent or short or simple and the colon is not sacculated.
The order carnivora has been subdivided into two suborders.
Suborder Credonta (Extinct):
1. The canines were strong but no single carnassials.
2. Molars bluntly tuberculate or ridged.
3. The brain was possibly very small.
From Palaeocene to Miocene in Europe, Asia and America.
Examples Hvaenodon. Arctocyon. etc.
Suborder Fissipedia:
1. The incisors are almost always 3/3, the canines are usually large.
2. The digits bear sharp retractile claws.
3. They are digitigrade or plantigrade or subplantigrade.
The suborder has three sections.
Section AEluroidea:
1. The canines are large, the carnassials are the last premolars above and the molars beneath.
2. The skull is generally rounded, the zygomaticarches are wide and strong and the tympanic bullae are large smooth and thin-walled and divided by a septum.
3. The alisphenoid canal is absent.
4. The paroccipital process of the exoccipital is applied to the posterior part of the tympanic bulla.
Examples. Felis, Civet, Hyaena, etc.
Section Cvnoidea:
1. The dentition is more generalised.
2. The tympanic bulla is dilated and with a rudimentary septum within it.
3. The paroccipital process of the exoccipital is prominent and is in contact with the tympanic bulla.
4. The caecum is either short and simple or long and peculiarly folded.
Examples. Can is (dog), Vulpes (fox), etc.
Section Arctoidea:
1. Plantigrade or subplantigrade and usually provided with five toes.
2. The tympanic bulla is depressed with no trace of an internal septum.
3. The paroccipital process of the exoccipital is widely separated from the mastoid process and is quite apart from the tympanic bulla.
4. A caecum is wanting.
Examples. Ursus (bear), Lutra (otter), etc.
Suborder Pinnipedia:
1. Marine carnivores, move on land with difficulty.
2. Five well developed digits connected by a web of skin.
3. The incisors are less than 3/3, carnassials absent and the back teeth bear pointed cusps.
4. The tympanic bulla is often depressed and without an internal septum.
5. The paroccipital process of the exoccipital is separate from the tympanic bulla.
Examples. Phoca (seals), Trichechus (walrus), Otaria (sea-lion), etc.