Monday, 26 September 2011

adaptions of brachiopods

Turbulent of water

A thick and heavy shell- provide extra stability
strong ribbed valves- to strengthen against wave action
a large pedicle opening- to support large pedicle to secure attachment
a folded margin- to reduce sediment getting into mouth

adaptions in quiet water

no pedicle opening- peddicle not needed
week ribbed valves or smooth- quiet conditions
may have median fold or sulcus- to seperate curents of water entering and leaving the animal
may have extension of valves to form 'wings'- to provide large surface area to prevent sinking into the sediment

adaptions in a sof muddy substrate

valves flat with large resting area- to provide a large surface area to prevent sinking into sediment
one margin of the shell may be turned upwards, away from the sediment- to ensure that some part of the shell remain out of the sediment for feeding


most brachiopods possess teath and sockets, and have shells made out of calcium carbonate. each valve shows bilateral symmetry, sizes range from 5mm to 8cm. the biggest valve is called the pedical valve. this contains a pedicle which attaches the brachiopod to the floor. the brachial valve contains supports for the lophophore.  

these are benthonic,sessile, marine organisms enclosed between two unequal-sized valves. they are still alive today, but are greatly reduced in number.

Sunday, 25 September 2011

Corals- mode of life

Looking at corals today, we find some species have a type of algae living inside them. these algae are called zooxanthellae. there is a symbiotic relationship between the algae and the coral. 

The soft tissue is not preserved, but we assume that fossil corals had samilar soft tissue to modern-day corals

conditions needed for good coral growth 

  • need to be shallower than 30m - as need light
  • clear waters so the algae can phtosynthesise
  • high energy condiditions as need need well oxygenated waters
  • temperatures beetween 23*C and 27*C
  • found beetween 30* north and 30* south of the equator 

 types of modern reefs

  • Fringing reef- must meet the land and some parts above sea level at low tide
  • Barrier reef- further out to sea , with a lagoon seperating the land from the sea
  • atolls or coral islands- ring shaped found far offshor. formed due to hot spot activity as the volcanoes create an area of shallow sea.


Coral consist of two layers, an outer endoderm and an inner endoderm. corals have an calcium carbonate skeleton, which is of imense importance in the geological record.

Tabula- horizontal plates dividing the coralite skeleton

calice-Bowl shaped depression where the soft polyp sits

columella- Axial rods which supports the septa, running up the centre of some corals

septa- vertical plates, dividing the corallite skeleton

dissepiments- curved plates connected to septa and tabulae

Rusgose Corals 

  • These extinct corals are either solitary or colonial. the epitheca, or outer layer, is often wrinkled and may be hornshaped.
  • the have 1 plane of symmetry known as bilateral symmetry
  • they have a columella
  • may have dissepiments but not always present
  • usually large

Tabulate Corals

  • These are extinct
  • always colonial
  • usually small
  • they show radial symmetry
  • no speta or undeveloped
  • may have dissepiments
  • dont have a columella
Scleratinian corals 

  • either solitary or colonial
  • usually small
  • radial symmetry hexagonal
  • show 6 primary septa
  • may have disspeiments
  • always have tabulae 

Wednesday, 21 September 2011

types of trilobites and adaptions

Benthonic (e.g Calymene) 
  • generally large trilobites
  • had a lot of pleura which means they have the ability to enroll for protection - lots of legs 1 pleura = 2 legs
  • epifaulnal - they crawl on the sea floor looking for food as active hunters or scavengers
  • had very good eyes 360* vision, the eyes would have been sensitive to movement to detect food and predators an advantage over other bottom dwellers in the same enviroment- could explain why they where so successfull.

Pelagic (e.g. Agnostus)
They where blind as no eyes                                  
  • had few pleura, and therefore few legs or gills.
  • found in sediments such as shales formed in low energy deep waters
  • had a pelagic planktonic lifestyle
  • possible lack of eyes means in deep water where theres no light
  • they where small and probably light weight

Nektonic (e.g. Deiphon)

  •  These where small trilobites - to stay a float
  • show streamlining
  • actively swimming, possibly as active hunters
  • eyes on stalks- ability to see 360* and beneth
  • inflated glabella may be filled with fat org as to help to float
  • has lots of pleura , with spines - has many legs for swimming and spines to increase surface area

Burrowing (e.g. Trinucleus)

  • These trilobites lack eyes      
  • shovel like head
  • benthonic and infaunal
  • no eyes due to depth
  • dug shallow burrows for protection or to feed 
  • extended genal spines - to spread its mass on soft substrate
  • pitted cephalic fringe

Tuesday, 20 September 2011


Trilobites are the earliest known organisms which belong to the phylum Arthropoda, a phylum which includes familiar creatures such as lobsters,crabs,insects and spiders. Trilobites are so-called  because their skeleton is divided into 3 lobes.  the head is called the cephalon the pygidium is the tail and the middle part is called the thorax.

Trilobites have a hard exoskelaton made out of a tough substance called chitin. the exoskeleton acts like a suit of armour, where plates move separately within the movement of the animal.


Cephalon- its made up of several structures, including the eyes, facial sutures, free cheeks, fixed cheeks and glabella. they eyes where compound eyes . spines may be attached to the glabella. there is also an antenna.

Thorax - the thorax is made up of thoracic segments, each possessing a pair of appendages and gills in life. each thoracic segment consists of two pleurae and a segment from the axis. Each pleuron may also have spines extendidng from them, depending on the mode of life. some trilobites were so flexible that they could curl up into a ball or enroll, rather like a hedgehog. the ability to roll was a defence mechanism.

Pygidium- the pygidium or tail is composed of several segments fused together.

more on trilobites will follow soon

Modes of life

Modes of life

Organisms have evolved to live in all enviroments. they live in various parts of the water column, on or in the sediment. They may hunt, scavenge or filter feed. they may swim ,float,crawl or remain fixed in one position.

Benthonic-  Organisms that live on or in the sea floor 

Infaunal-  Organisms that live in the sediment, usually in a burrow many will filter feed

Epifaunal-  Organisms that live on the sediment

Vagrant-  Organisms that move around of the sea floor

sessile- organisms that dont move aroun on the sediment

Pelagic-  Organisms lives in the water column

Planktonic- Floats in the water column to wherever the currents will take the organism

Nektonic-  Actively swims in the water comlumn. Most are scavengers or predators

Trace fossils

Trace fossils provide glimpses of the nature and behaviour of ancient organisms of the geological record. Trace  fossils are extremely important as they can help us interpret the palaeo-environment. Trace fossils preserve the activity of an organism, not the organism itsellf. These include tracks,trails,burrows,borings and excrement. when an organism walk across soft fine sediment and leaves the inprint of its feet. There is then a very small chance that the footprints will be filled in by sediment before they are destroyed by water currents or wind.