Graptolites is an important index fossil for Paleozoic rocks and common throughout the world. As in Pakistan the sequences from the Ordovician to carboniferous age missing but these strata are exist in Noshehra and Chitral, so thats why its more valuable as regional fossil of sub-continent.
3. General Characteristics
• Graptolites belong to the phylum
Hemichordata
• Graptolites are the marine-colonial animals
which growing three dimensionally.
• Some of them were attached to the sea bed
(benthic) and many of them were floated
freely(pelagic) in the sea.
• Bilaterally symmetrical and tentacled.
4. Cont…
• Graptolie derived from Greek word that means
writing on rock(Grapto=writing &litho= rock).
• They lived from Cambrian to Carboniferous
times and flourished in sea environment.
• Size is 6 inches & some of them were up to 30
inches.
• Scientifically they known as Graptolithina.
5. Cont…
• The early Graptolietes are use as fossil guide
for Paleozoic rocks.
• Due to its flattened 3-D structure very hard to
identify as fossil.
• Preserved in the form black carbon film on
surface of rocks and in tectonically disturbed
sequence as light gray film.
6. Classes
There are two main classes of Graptolites on the
basis of their branches.
a) Graptolithina
b) Dendritic Graptolites
• Dendritic Graptolites: Dendritic mean many
branched Graptolites of order Dendroidea.
These were the benthonic marine animals i-e
lives or attached to the sea floor and lived till
the Carboniferous period.
7. Cont…
• Graptolithina: The few branched Graptolites
that belong to the order Graptoloidea were
good swimmer i-e pelagic.
• Graptolithina were survived up to the
Devonian period.
8. Morphology
• Graptolites Consist of numbers of branches
that is called stipes. stipes originated from
sicula.
• Sicula: Individual organism of graptolites join
to make the tube like structure. It is initial
growth point of colony of the Graptolites
• Rhabdosome :A single colony of Graptolite
9. Cont…
• Theca: Each succeeding micro-organism is
hosted in tree or tube like structure.
• Arrangement of theca and braches are very
useful criteria to recognize the fossils of
Graptolites.
• Nema: This is a thin tube at larva stage of
Graptolite that originated from the apex of
sicula.
10.
11. Cont…
• Aperture: In graptolites the point/end at
which the theca opened is called aperture.
• Vergulla: The spine at the siculum end.
• Dissepiment: The bar which connects adjacent
stipes into the rhabdosomes of dendroid
graptolites.
12. Occurrences in Pakistan
• Found all over the world in the rock of
Ordovician to Carboniferous with their divers
verity and shape.
• In Pakistan the sequences from the Ordovician to
carboniferous age missing but these strata are
exist in Noshehra and Chitral.
In Chitral, Graptolites fossils are present in
• Broghil Formation,
• Lun shale of Chitral
• Shogram Formation
