Index fossils in PakistanSubmitted by: Khurram Shahzad

Submitted to: Mumtaz Ali Khan

24 October2014

Table of contents page no;

1. Index fossils 02

2. Types of index fossils and occurrences in Pakistan 03

a. Trilobite 03

b. Brachiopods 04

c. Pelecypods 06

d. Gastropods 07

3. References 08

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1. Index fossils; Any animal or plant preserved in the rock record of the  Earth that is characteristic of a particular span of geologic time or environment. A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time. Index fossils are the basis for defining boundaries in the geologic time scale and for the correlation of strata. In marine strata, index fossils that are commonly used include the single-celled Protista with hard body parts and larger forms such as ammonoids. In terrestrial sediments of the Cenozoic Era, which began about 65.5 million years ago, mammals are widely used to date deposits. All of these animal forms have hard body parts, such as shells, bones, and teeth, and evolved rapidly.

Fig.1. Keyed to the relative time scale are examples of index fossils, the forms of life which existed during limited periods of geologic time and thus are used as guides to the age of the rocks in which they are preserved.

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2; Types of index fossils and its occurrence in Pakistan:

2. a; Trilobite:

Trilobites are hard-shelled, segmented creatures that lived hundreds of millions of years ago in the Earth's ancient seas.  They are considered to be one of our planet's earliest complex life-forms and are one of the key signature creatures of the Paleozoic Era.  Trilobites went extinct before dinosaurs even existed.  The name 'TRILOBITE' means 'three lobed" and is derived from the fact these animals had bodies featuring three longitudinal lobes, not lateral (head, body, tail) as is often thought.  The lateral division of three parts is shared by many arthropods, not just trilobites. Still most baffling is the incredible diversity of sizes and features that made up the trilobite group.  Many bizarre species co-existed with highly specialized body parts that defy the theories of evolution in their "sudden" emergence and diversity during the Early Cambrian Period in what is known as the 'Cambrian Explosion. Trilobites were among the world's first arthropods, a phylum of hard-shelled creatures with multiple body segments and jointed legs (although the legs, antennae and other finer structures of trilobites only very rarely are preserved).  They constitute an extinct class of arthropods, Trilobite that is comprised of over 15,000 known species.

Occurrences in Pakistan:

Trilobite’s fossils of Cambrian to Permian age are found in eastern salt range of khewra sandstone and jutana dolomite and khusar Formation in D.I.Khan. It is also found in various localities in Pakistan.

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Fig .2.Trilobite’s fossils.

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2. b: Brachiopods:

The brachiopods are a large group of solitary and exclusively marine organisms with a very good geologic history throughout most of the Phanerozoic and are among the most successful benthic macro invertebrates of the Paleozoic. They are typified by two mineralized valves which enclose most of the animal. Like the bryozoans, brachiopods are filter feeders which collect food particles on a ciliated organ called the lophophore. An excellent example of a brachiopod lophophore can be seen in the Recent terebratulid.  Brachiopods differ in many ways from bryozoans (in both soft and hard-part morphology), and are thus considered by most workers as a separate but closely related phylum. However, one of the most distinguishing features of brachiopods is the presence of a pedicle, a fleshy stalk-like structure that aids the animal in burrowing and maintaining stability. The pedicle can be seen in the Recent Lingula.

Currently, brachiopods are divided into two or three major groups. We depart from your text in considering two major groups: Class Inarticuleta (including lingulids), and Class Articuleta based on the presence or absence of hinge teeth and sockets.

A large portion of this lab is designed to make you familiar with the seemingly endless morphologic terms associated with brachiopods. This is a necessary process, as understanding such features are the only tools available to enable one to identify brachiopods with any success Although it may seem unreasonable to ask one to learn the various groups presented below, with a little common sense and observational skills, recognition is actually easier then it may first seem.

Phylum Brachiopoda (Cambrian-Recent)Class Inarticulata (Cambrian-Recent)Class Articulata (Cambrian-Recent)

Order Orthida (Cambrian-Permian)Order Strophomenida (Ordovician-Jurassic)Order Pentamerida (Cambrian-Devonian)Order Rhynchonellida (Ordovician-Recent)Order Spiriferida (Ordovician-Jurassic)Order Terebratulida (Devonian-Recent)

Brachiopods and WWII:

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In 1941 the Fossil Invertebrate Section at the Field Museum was making plans for a new and larger display but with the start of World War II these plans were postponed. The Curator of Fossil Invertebrates, Dr. Sharat Roy, served with the U.S. Army as a captain in the India-Burma Theatre of war. Near the end of the war he was able to take a month long leave and collect fossils (including a large collection of Permian brachiopods) and other geologic specimens from the Salt Range in what was then Punjab, India, but today is part of Pakistan. The Salt Range is named after the rich salt deposits that are close to 500 meters (1600 feet) thick, but is also famous (at least among geologists) for Permian brachiopods. He shipped his fossil collection from the Salt Range back to the Field Museum. After the war Roy was made Chief Curator of the Geology Department and expanded his areas of interest and began studying meteorites. In 1946 the Field Museum hired a new curator of Fossil Invertebrates, Eugene S. Richardson. One of Richardson’s first assignments was identifying and curating Roy’s collection of brachiopods from the Salt Range.

Occurrences in Pakistan:

Brachiopods  from Permian-Triassic boundary beds are found in Chhidru Formation, jutana dolomite and khewra sandstone. And also found in mianwali Formation and chorgali Formation also.

Fig.3. Brachiopods fossils in Pakistan from khewra eastern salt range.

2. c: Pelecypods:

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Pelecypods (peh-les'-i-pods) include oysters, clams, mussels, and cockles. They have been found in some of the oldest marine rocks known and still are very numerous in the seas and rivers today. In the past, some pearl buttons were made from clam shells from the Illinois and Mississippi Rivers. This major industry caused near extinction of some species.Most Pelecypods, also known as bivalves, have two shells that are mirror images of each other, one on the right and one on the left. Each shell has a beak that points forward and represents the spot where the shell began to grow. The top edge of each shell commonly has several teeth and sockets that fit into those of the opposite shell to make a hinge. The outside of the shell generally is ornamented by ribs, spines, and growth lines.

Most Pelecypods form shell banks in the seas or rivers on sand and mud flats. Many burrow into the mud or sand and even into wood or rock. Some oysters attach themselves to rocks, and others creep about the sea floor by means of a hatchet-shaped foot thrust between the open valves. A few (scallops) move by jet propulsion, forcing water in a jet stream from openings at the beak end.

.Occurrences in Pakistan:

In Pakistan Pelecypods fossils are of Permian Triassic boundary is found in jutana dolomite and khewra sandstone in Eastern salt range. And also found in chorgali Formation in Rumli Islamabad.

Fig.4. Pelecypods fossil in detail.

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2.d: Gastropods: Gastropods are one of the most diverse groups of animals, both in form, habit, and habitat. They are by far the largest group of molluscs, with more than 62,000 described living species, and they comprise about 80% of living molluscs. Estimates of total extant species range from 40,000 to over 100,000, but there may be as many as 150,000 species! There are about 13,000 named genera for both Recent and fossil gastropods. They have a long and rich fossil record from the Early Cambrian that shows periodic extinctions of sub clades, followed by diversification of new groups. Gastropods have figured prominently in paleobiological and biological studies, and have served as study organisms in numerous evolutionary, biomechanical, ecological, physiological, and behavioral investigations. They are extremely diverse in size, body and shell morphology, and habits and occupy the widest range of ecological niches of all molluscs, being the only group to have invaded the land.

Occurrences in Pakistan:

In Pakistan gastropods fossils of Permian Triassic boundary are found in salt range. And also found in jutana dolomite in eastern salt range chorgali Formation and also be here in chorgali Formation in Rumli Islamabad.

Fig.5. Gastropods fossils.

3. References:

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i. http://geology.about.com/od/glossaryofgeology/g/Index-Fossils.ii. http://www.fossils-facts-and-finds.com/brachiopods.iii. http://www.utsa.edu/fieldscience/pelecypod_info.iv. http://www.ucmp.berkeley.edu/taxa/inverts/mollusca/gastropoda.v. http://www.paleodirect.com/trilobites.

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