1. Structural peculiarities and
phylogenetic relations of
Prototheria

2. Mammals
Mammals evolved from reptiles during triassic period. It is
most highly evolved group of animals.
Characters of Mammal:
 Mammary glands on females for suckling the young ones.
 Hairy skin.
 Skin richly glandular.
 Differentiated dentition.
 Double occipital condyle.
 Double headed ribs.
 Constant body temperature.
 Three ear ossicles.
 Respiration always by lungs.
 Increase intelligence.

3. Subclass – Prototheria
This include primitive egg laying mammal. They nourish
their young with milk from mammary gland. It comprises
only one living order.
 Order- Monotremata
 Mammary glands without nipples.
 No external pinna.
 Females oviparous.
 Testis are abdominal.
 Teeth only in the young ones.
 Heart is four chambered.
 Example- Ornithorhynchus , Echidna

4. Distinctive characters of Prototheria
 Distribution-these are distributed in the
entire Australian region, including
Australia, Tasmania, Newguinea and
neighbouring Island.
 Habit and habitat-
Aquatic or terrestrial
Burrowing
Mainly insectivorous
Nocturnal

5. External features
 Body small covered by hair
and spines.
 Muzzel or snout produced
into beak.
 External ear absent.
 Mammary glands without
teats.
 Male carries a hollow,
horny, tarsal spur on each
hindleg connected
internally to a poison gland.
Ref. – A Textbook of Zoology by Parker & Haswell

6. Body cavity - Divided by a typical mammalian
diaphragm.
 Endoskeleton
 Skull dicondylic.
 Malleus and incus relatively
large.
 Lower jaw consist of single
bone dentary.
 Cervical vertebrae 7
 Ribs unicephalous.
 Presence of epipubic bone.
 A large T-shaped
interclavicle is present.
 Limbs and girdles reptilian
like held laterally. Ref.-The life of Vertebrate – J.Z Young

7.  Digestive system- teeth develop only in
embryo.
 Respiratory system-respiration pulmonary by
lungs.
 Circulatory system- heart four chambered,
right valve incomplete, R.B.C small circular and
non-nucleated.
 Excretory system- Kidney metanephric, ureter
open into urinogenital sinus which terminate
into common cloaca.
 Nervous system-brain small without carpus

8. Reproductive system
 In male testes is
abdominal, penis
retractile for passing
out sperms not urine.
 In female right ovary is
reduced and oviduct
lead separately into
cloaca.
Ref. – www.edu.com

9. Development
 Eggs large with much yolk and plastic shell.
 Cleavage is meroblastic.
 No uterine gestation
 Newly hatched young are very immature.
 These are fed on milk in abdominal pouch till
fully grown.
Ref. – Man & Vertebrates by Romer

10. Phylogenetic relationship
 Subclass- Prototheria shows its affinity to
reptiles and birds with little advance over
them.
 Affinities with class - Reptilia
 Claws are present.
 A median T shaped interclavicle present.
 They can survive during starvation for a
longer period.
 Eggs calcareous, uterine gestation is
absent.
 Testes abdominal.

11. Affinities with birds
 They have following resemblances-
 Teeth are absent.
 Feet are webbed.
 Tarsal region contain spur.
 Oil gland is present.

12. Affinities with mammals
 Body covered by hair.
 Skin richly glandular containing sweat
and sebaceous gland.
 Mammalian diaphragm divides body
cavity.
 Skull dicondylic, presence of four optic
lobes, cervical vertebrae seven.
 Liver is lobed like mammals.
 Heart is four chambered, only left aortic

13. Peculiar characters of Prototheria
The following characters are peculiar to
Prototheria :
 Presence of tarsal spur in male.
 Milk gland derived from sweat glands
and without teats.
 Temporary abdominal mammary pouch
in female during breeding season.
 Jaws elongated forming a beak or
rostrum.

14. THANK YOU