1. PowerPoint Presentation
Phylum: mollusca
Class : Gastropoda

2. CLASS : GASTROPODA
Gastropods are found mostly in marine conditions; also in fresh water conditions.
Snails & cowry shells are common examples of gastropod.
Gastropod shell is strong and helps in the protection of animal.
The shell is univalved and it is calcareous.
The first representative of gastropods occur from early cambrian age.
Gastopods increased in palaeozoic era and mostly in mesozoic era.
Gastropods have world wide distribution in quarternery or recent times

3. spiral coiling .whorl, suture line &spire
Univalved shell shows “spiral coiling”.
Each coil is called as a whorl.
The whorl shows “helicoid spiral type of coiling”.
Each whorl joins with other whorl along a line called “suture line”.
All the whorls except body chamber are called “spire”.
The angle formed at the top of the shell is called “spire angle”

4. Direction of coiling
If the coiling is clockwise then the aperture will be right side; it is “dextral condition”.
If the coiling is anti-clockwise then the aperture will be left side; it is “sinistral condition”.

5. Holostomatus & siphonostomatus
There are two conditions- holostomatus & siphonostomatus.
The aperture or opening will have a margin called “peristome”.
Peristome will be complete in holostomatus condition.
Siphonostomatus condition will have a bend or break in the margin ex: physa
The peristome will have an outer lip and an inner lip -outer lip may be plain or reflected (turned out) or inflected (turned in).

6. The whorls or chambers of the shell are formed in two different types-
Columella & umbilicus
The whorls or chambers of the shell are formed in two different types-
One type is formed around the pillar like structure called “columella”.
In some fossils the shell forms around a hollow axial cone. Such fossil will show an opening in the body chamber called “umbilicus”.
Shells having umbilicus are called perforate; imperforate shell do not show umbilicus.

7. Forms of gastropod
Coiled gastropod shells will show 8 different forms.
The forms are depending on – a. Type of coiling b. Length of spire and spire angle c. Shape and size of body chamber

8. Discoidal form : Planorbis
fresh water air breathing mollusca belongs to planorbis.
Appears like a disc.
Whorls will be almost in a single plane.
Planorbis is a Latin word which means- flat ring or disc.

9. Conical form : conus
It is a cone shaped fossil with a medium spire and long body chamber.
Base will be flat.
Aperture will be long and narrow.

10. Turbinate form : Turbo
This form is nearer to conical form, but it will have rounded body chamber with rounded base.

11. Turreted form :turitella
This form will have long spire and a cute spire angle.
Body chamber is big and rounded.

12. It is spindle shaped, narrow at both ends and broader in the middle.
Fusi form : fusinus
It is spindle shaped, narrow at both ends and broader in the middle.

13. Globular form : Nautica
The shape is like a globe with a short spire and big body chamber.
Bogy chamber is rounded.

14. Cylindrical form : pupilla
This form will have cylinder shape with similar diameter for all whorls.

15. Convolute form : cyprea
Body chamber is big and prominent.
It encloses all other whorls.
Aperture will be long with folded margin.

16. Ornamentation
The shell of gastropod shows some thin lines called “striations”.
If the striations are parallel to the suture line, it is “spiral striations”.
If the striations are vertical to the suture line , they are “transverse striations”.
Some fossils show “knobs” on the surface.
Some fossils will have “spines”.
A few fossils will show combination of all the above features.
Ex: murex

17. Geographical and geological distribution
Phylum mollusca is a common marine animal, found in salt water conditions.
Gastropods are found in large numbers, distributed in different environments of the world .
Gastropods are found in marine waters, fresh waters & on the land.
The opisthobranchiata order fossils live in marine & fresh water conditions.
opisthobranchia

18. Prosobranchiata order fossils live in marine conditions.
Pulmonata order fossils found in fresh water and on land.
Gastropods live in groups and found at shallow depths.
The first representative of gastropods occur from early cambrian age.
Gastropods increased in palaeozoic.
Gastropods were mostly holostomatus shells.
The shells with siphonostomatus condition were more in tertiary period.
Gastropods have world-wide distribution in quaternary or recent times.
PULMONATA

19. Thank you
By : D sai phani prashanth 3rd Bsc MPG