Graptolite Fossils

Victorian Marine Fossils series

What are graptolites?

Graptolites (formally known by their scientific name Graptolithina) are extinct marine creatures that formed twig-like or net-like colonies composed of one or more branches. These colonies mostly floated freely in the sea but some may have been attached to the sea floor. Because of their branching form they may have superficially resembled seaweed but they were in fact animals. Each colony was made up of a large number of individual microscopic animals that lived in a series of tiny cup-like structures arranged along the branches of the colony. The individual animals were all joined together by a type of nerve cord.

Photo of Graptolite, Pendeograptus fruticosus

Graptolite, Pendeograptus fruticosus, Early Ordovician (c. 482 my old), Castlemaine district, Victoria
Source: Museum Victoria

The graptolite colonies were originally three-dimensional but during fossilization they usually became completely flattened. After flattening the cup-like structures that housed the individual animals appear like serrations along one or both edges of the colony. The flattened remains of the colonies preserved in slates or shales tend to resemble pencil marks on the rock, and the name ‘graptolite’ is derived from Greek words meaning ‘writing on stone’.

Where are graptolites found?

Graptolites first appeared in the Cambrian Period, 545–490 million years ago (mya), and evolved rapidly during the following Ordovician Period (490–434 mya) when the greatest variety of different forms lived. They suffered a major decline in the Silurian (434–410 mya) and only a few forms lasted into the Devonian. They finally became extinct during the Carboniferous Period, about 315 my ago.

Hundreds of different species of graptolites are known and many of them were widely distributed around the world because they drifted in the surface waters of the oceans. Graptolites are therefore one of the most important groups of fossils for dating rocks of Ordovician to early Devonian age. Ordovician rocks occur over wide areas in central and eastern Victoria, and contain one of the most abundant and varied assemblages of graptolites in the world.

These assemblages have been used to subdivide the Victorian Ordovician sequences into 30 intervals and to date these intervals accurately with other rock sequences in New Zealand, Asia, Europe and North America. Graptolites were also used to work out the structure and sequence of Ordovician rocks in the central Victorian goldfields, as the strata themselves are too uniform in appearance to allow this to be done on the basis of rock type.

Photo of Graptolite, Rhabdinopora scitulum

Graptolite, Rhabdinopora scitulum, Early Ordovician (c. 485 my old), Romsey district, Victoria
Photographer: Rodney Start / Source: Museum Victoria

Visitor Information

Common species of fossil graptolites from Victoria are exhibited in the Marine Invertebrate Fossil Drawers in the Melbourne Museum Discovery Centre.

Further Reading

Palmer, D. and Rickards, R. B. (eds) 1991. Graptolites: writing in the rocks. Fossils illustrated, volume 1, Boydell Press, Woodbridge, Suffolk, UK. [Detailed information and photographs on graptolites].

Comments (14)

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Liana 2 December, 2010 22:30
Im really hating this 'creation view is faith and evolution is science' thing because I find it lots easier to believe that, say, all the kinds of dogs in the world came from two dogs rather then they all came from a rock. they dont have an explanation for how the blood could last that long, and why 65 million years anyway? the geologic column was made before carbondating and all that was even made. And if the age of the rocks are determined by the age of the fossils and the age of the fossils are determined by the age of the rock then i have to say evolution is much harder to believe. and creation science isn't just a bible thing.. if you looked around you would find science supported with the bible. for example, a dinosaur bone with blood vessels and tissue in it. haha evolution cracks me up
RT 25 September, 2013 17:09
Liana, you obviously are in over your head on this one, and obviously don't have a grasp of some basic scientific concepts. I find more scientists are willing to read the bible in an attempt to understand other's perspectives than religious people are willing to read and understand scientific principles. I think the bible just provides a simple way of explaining the world for those who don't want to, or can't, understand it. In terms of religion's view of science and evolution, I believe it is called a logical fallacy through personal incredulity.
Josh 12 January, 2011 22:37
I think you may have missed the point of this article Liana. Fossils such as Graptolites are used to define the ages of sedimentary packages of rock but they define the ages by a number of different ways. Firstly, an age is determined from volcanic material in the stratigraphic column (this is usually a volcanic ash layer [termed a Tuff] but can be a dyke [an igneous rock that 'cuts through' the rocks] or a layer of lava or all of the above). The age is what they call an absolute age and is determined by basically assessing the radioactivity of certain elements with the rock (common elements are potassium, argon, lead or uranium [carbon is not used very often in geology/palaeontology because it has a very short half-life and can only date very 'young' rocks or artefacts. It is used in archaeology extensively however]) to find out how long they have been radioactive for (this is a method that has been used for a fairly long time in the science disciplines and has very extensive supporting evidence and scientific methods). Once they have this age, they determine what the fossiliferous unit's relationship is to the unit that has been radioactively dated. By relationship, i mean does the dated dyke cut through the fossiliferous unit? If yes, then the unit is older than the dyke (because it the unit had to be there before the dyke in order for it to cut through it). This is called a relative age. Many other relationships are used to determine relative age also. To clarify on your comment about the 'dinosaur bone with blood vessels and tissue in it', this is still a very heavily debated topic and is widely controversial. Before the work of MH Schweitzer, the only known living tissue samples are from fossil deposits of exceptional preservation potential and are young (e.g. the collagen from a mammoth fossil was sequenced of 100,000 years to 300,000 years old). There is substantial evidence to support it but there is also evidence which show other possibilities to explain it (e.g. Kaye TG, Gaugler G, Sawlowicz Z (2008) Dinosaurian Soft Tissues Interpreted as Bacterial Biofilms. PLoS ONE 3(7) [abstract @]). I guess the reason for this comment is that science isn't 'out to get' "creationist". Science is a part of our society because it helps us learn more about this incredible planet called Earth. Faith in God or Adi Purush, Yahweh, Aesir, Nezha or whatever your faith, is yours. You may share that faith with many but why try and take the faith others away? If your answer is: for the 'greater good', then look no further than religion because religion has been the reason for war for many centuries. I have read many parts of the Bible (no, I'm not claiming I've read the whole thing) and I carry some of the ideas from the Bible with me. Perhaps you should take a less ignorant approach also and read the first chapter of an introductory geology or palaeontology book. You might find that your faith in your religion is bolstered rather than in question.
Jiny 5 May, 2011 19:37
In the last photo, does anyone know what rock it is fossilized in?
Discovery Centre 13 May, 2011 15:01
Hi Jiny, the fossil of Rhabdinopora scitulum shown here is in black shale, a rock formed from muddy sea-floor sediments deposited in the Ordovician, over 440 million years ago.
Dierk von Behrens 6 February, 2012 16:18
Thank you for an effective, well-illustrated overview of this subject. I also much appreciate Josh's response to Lina.
Gabs M. 18 March, 2013 20:15
I honestly disagree with the majority of you people. I think the evolution theory(ies) are a bunch of dumb ideas coz like Lina said a lot of science is explained by the bible, however the same can be said for the other way around. But the Bible really does hod all the truth so yeah take that buddies!!!! 8O Btw how may i ask can scientist say that the universe all started from some random "Big Bang", I mean how is that realy logical.? There is something I gotta say about some of this and that is that the earth probably is miions of years old, however this is also something that is again justified by the Bible. The first verse goes like so-In the beginning God created the heavens and the earth.~Gen 1:1. Verse to goes like this-But the earth became waste and emptiness, and darkness was on the surface of the deep, and the Spirit of God was brooding upon the surface of the waters. These two verses show that there must have been a reason as to why the earth became like this, and science seemed to come up with an answer. They believe that the earth is millions of years old, and there is a gap between the two verses so there you go. From the time that God created the heavens and the earth and when it became waste and emptiness there is a gap filled in by the miions of years explained by scientists so yeah. And just so y'all know I'm a year 9 student who believes in God but is also facinated with science, I plan on being a vet when I'm older, so yeah that just goes to show.
Gizmo 6 November, 2013 04:09
Gabs, You do realise you need to have a very in depth understanding of biological principles (including the theory of evolution) in order to become a vet, right? You also need to understand how science works. This means you will need to research evolution and many other areas of biology for many years, and demonstrate you have good working knowledge of these topics. If you find you cannot accept one of the major facets of biology because of your faith, you are likely to be unsuccessful in a biology based career. Also, as a future scientist, you will need to learn what a scientific theory actually is. Good luck with your plan to be a vet: you're probably going to need it.
Sr89 14 October, 2013 21:00
Hahaha @Gabs M - a religious person schooling people on logic. My god! No wait, your god. Put the bible down and read one of your science textbooks with an open, unbrainwashed mind. Then make up your mind.
Maureen 20 April, 2015 11:12
Stop the "either/or" argument. I've taught geology to people who believe in God. Change over time in the fossil remains of successive layers of rock are clear evidence of the evolution of life. And Evolution is a basic tenet of modern biology. If people feel that God started that process, I have no problem with that point of view. Why be so polarized about such a compelling picture of the way life functions on earth?
Charles 20 May, 2015 15:11
Talking about the big bang, my first reaction to it was "don't people think?" But when I read on and realized there were reasons for people believing this like- the components of the universe are constantly moving away from each other therefore they must have started from a point etc etc. I saw the reason in that. Our faith is ours to keep but when reason shines its light ahead, we must take the step forward, that's the only way we continue to advance in life.
Teresa 12 October, 2015 14:54
Wow! Why are the comments from obviously religious people so angry? Is scientific reason messing with blind faith? I love the fact that scientists endeavour to seek truth and reasons for why the Earth is the way it is. Only after much research and evidence is gained can an hypothesis be called a 'theory'. If there is evidence against that theory, then it can be altered to reflect new knowledge and wisdom. Christian faith relies on believing what is written in a book over 1000 years old. We know so much more now that our world view should reflect this new knowledge. The scientific revolution and subsequent age of enlightenment was about revealing the truth about how our world worked and moving away from the previously held view that all was explained by divine intervention.
cam 14 February, 2017 00:34
I believe God created everything here on earth--or just everything,period. BUT that doesn't stop me from believing the big bang theory...because,people, the author/scientist of such did not write and publish it because it's just his/her belief...of course, it went through a series of studies, investigations,etc. they didn't write/publish articles like this to get attention! peeps,let's be open minded..I needed the info in this article for an assignment and happened to read those comments..can't help but comment too even if it's 2017 already...PLEASE people...never EVER use the name of God if you're just going to talk sh*ts and put other people or other's work a Christian, I'm very disappointed to whoever wrote that,I believe the topic here is about what period 'graptolites' existed and the time of it's extinction NOT where it came from or who or what created it #myopinion
Paul Gahan 12 June, 2017 17:22
I am also a Christian and love the Biblical stories. I have dug up Isograptus and Cardiograptus fossils on my property in Central Victoria (Australia)where I live in an Old Methodist Church building where Christians worshiped for almost 150 years. It was well attended during the Gold rush period. Well, there you go! "About 450 million years old. Floating animals, considered to be very primitive chordates, the phyla that also includes all vertebrates." One day:100 million years?? doesn't matter. When I sleep in the old church, I have a sense of all the Christian saints from the past in this place. I feel they are looking out for me and cheering me on! But how good is this? I can now take even more comfort knowing that God so long ago was here - well before the building of this fragile brick and wooden edifice - messing in the clay - breathing life into the sea slugs and worms leaving His creative marks in the rocks demonstrating His love and care as The Great Creator. Continue with your important scientific work demonstrating just how old our planet really is. Just maybe then we will all work harder looking after our fragile environment. Cheers PG
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