Rufaida Hassan Nafia gave a presentation on Habit & Habitat of Trilobites which is Index Fossil of Cambrian geological time. This lecture is part of Earth Science, Paleontology. Presentation Video Link on YouTube: https://www.youtube.com/watch?v=5XOcmcZA_YE&ab_channel=EarthDetective We are available in social media. Follow our Facebook Page: https://www.facebook.com/earthdetective Follow our Linkedin Page: https://www.linkedin.com/company/eart... Visit Our YouTube Channel: https://youtu.be/Hg5PcDsIJao If this video seems helpful to you, please like and subscribe. #trilobite #cambrian #paleontology #geology #habit #habitat #index #fossil

1. Presentation
On
Habit & Habitat of Trilobites
Rufaida Hassan Nafia

2.  The trilobites constitute an extinct group of paleozoic arthropods which is easily
recognized by their distinctive 3 lobed,3 segmented form.Trilobites are usually 50 to
75mm in length.Some are quite tiny and a few giants attained a length of more than
half a meter.
 It had appeared at the beginning of the Cambrian period,about 542mya.
The dominant among the invertebrates until the cephalopods displaced them in
the Late Ordovician.Therefore they declined gradually to the close of the
Paleozoic when they became extinct.

3.  In as much as trilobites are extinct, nothing can be directly determined about their
habits and habitats by observation.By observing their faunal associates, their methods
of burial and preservation, and their different exoskeletal structures we got some
Information about them.
The Food of Trilobites:
It is assumed that trilobites selected their food from
among their living associates like sponges ,protozoans
bryozoans, branchiopods and mollusks. Some were quite
likely herbivorous,feeding on the simple plants of the earlier
pacleozoic seas.Others may have been scavengers ,cleaning
up organic debris included in the soft sediments through
which they ploughed and borrowed.

4. Prey on other animals:
Trilobites almost certainly served as food for other animals .Among possible
enemies were Cephalopods,early chordates,sharks etc.It seems more
than a coincidence that trilobites underwent a marked decline in the
Late Silurian and in the Devonian with the advent of Sharks and other early fishes.
How they protect themselves
 Some investigators have suggested that the early trilobites had no
exoskeleton.The original development of the exoskeleton was possibly a response to
protect themselves.
 Fossil borrows and tracks have been found and these show that Trilobites
could burrow into sediment to avoid predators.
 Many trilobites living after the Cambrian development the ability to roll up,also
probably as a defense against predators.

5.  When in defense mood ,the ridges would have allowed
water to enter & flow over the gills,so that the trilobite
could breath while enrolled.
 We know that some species had complex eyes and used
them to hunt and navigate. However, some deep sea
species were blind, and had no use for eyes in regions
where light could not reach.
Reproduction of Trilobites
 Fossil evidence of the reproduction of these arthropods is limited. Though no
evidence exists, researchers believe that they produced eggs.
 Their reproductive habits would have varied by species.
 The eggs hatched into a larval form, which underwent stages of growth before
reaching the adult form.

6. Habitat of Trilobites
 Some lived on the sea floor
 others lived pelagic lives swimming through the open water.
 Some lived in extremely shallow regions or intertidal zones.
 After the Ordovician, when many trilobites groups went extinct, the survivors
tended to be restricted to deeper water.
Trilobites lived in a wide number of different habitats.

7.  Trilobites molted periodically like other arthropods.But the number of molting is
unknown.As a consequence of molting,exoskeleton greatly outnumbered actual
individual organisams on the sea bottom.That’s why we face difficulties to
understand the actual exoskeleton.
The many free cheeks,cranidia,thoraic segments and pygidia scattered sporadically
throgh the sedimentary rocks should probably be regarded in large part as fragments
of molts rather than as parts of exoskeletons.
 The molts were no doubt of low specific gravity and can be transported long
distances.It surely makes difficulties to identify the actual environment of trilobite life.

8. Thank you!
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