Brachiopods are marine invertebrates characterized by their two valves and bilateral symmetry, with the larger pedicle valve typically being convex. Their shell structure features a beak and umbo, with various shapes including elliptical and semi-elliptical. The document outlines the characteristics, symmetry, and classification of brachiopod shells.

1. How to describe a Brachiopod
Shell, Shape of Shell,
Symmetry etc.
Sumaiya Amin Titun

2. Brachiopoda
Brachiopods are marine invertebrates,
meaning they have no backbone, and are
one of the few animal groups that live only
in the ocean. The name 'Brachiopoda' comes
from the Greek words 'brachion" (=arm)
and "podos" (=foot). They are sometimes
referred to as 'lamp shells' since certain
groups.
Fig: Brachiopoda

3. Brachiopod Shell
 Living brachiopods are normally
attached to rocks, shells, or other
objects with the help of pedicle.
 The two valves articulate along a hinge
line, which carries teeth and sockets. In
brachiopods, the larger valve contains
teeth and the smaller valve contains
sockets. The earliest part of the valve is
called beak and the rounded part
adjacent to the beak is called umbo.

4. Description of Shell
 The shell is bilaterally symmetrical with the plane
of symmetry passing through the pointed
posterior beak and rounded anterior margin. It
bisects each valve in brachiopods.
 The beak or pointed part is posterior and the
opposite round margin is anterior. The line along
which the valves are in contact is the
commissure.

5. The Shell
1.Anterior and Posterior
Anterior: The shell margin where
the valves separate and open that is
anterior.
Posterior: Opposite direction defined
by the position of Hinge line or
pedicle opening is posterior.

6. The Shell
2. Dorsal and Ventral
During life, the pedicle valve is commonly
larger and situates in a superior position,
and the brachial valve in a lower position.
The direction away from the pedicle valve
is learned Ventral and away from the
brachial valve is named Dorsal.
 .

7. Shell Shape
 OUTLINE
Brachiopod shells have diverse shapes.
The simplest forms are elliptical,
subcircular, or semi-elliptical. Shell shape
can be shown in the dorsal view and
lateral view.

8. Shell Shape
 CONVEXITY
The pedicle valve is always convex.
Depending upon the brachial valve, the
shape is termed differently. We can classify
it into different 9 kinds.

9. Symmetry
 Brachiopods have a plane of symmetry that cut across
the two valves.
 Bivalves usually have a plan of symmetry between the
valves of the shell, which are mirror images of each
other; most brachiopods have a plan of bilateral
symmetry through the valves and perpendicular to
the hinge.

10. Bilateral Symmetry
Symmetry in which similar anatomical parts
are arranged on opposite sides of a median
axis so that only one plane can divide the
individual into essentially identical halves.
Brachiopods have this kind of symmetry.

11. References :
1. https://static.hwpi.harvard.edu/files/styles/os_files_xxlarge/public/trenton/files/brachconvexity.jpg?
m=1525446811&itok=ro1zJeHyhttps://images.app.goo.gl/mcyFL2sTE4ksTqfQ7
2. https://trenton.mcz.harvard.edu/phylum-
brachipopodahttps://www.slideshare.net/LeeannaCota/mollusks-bivalvesgastrocepha-marine
3. https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/brachiopods/
4. https://www.digitalatlasofancientlife.org/learn/brachiopoda/
5. https://fossiilid.info/64?mode=in_baltoscandia&lang=en

12. Thank You for
your Patience