What is a microfossil? Why are they useful? How do we extract them from the rock, and then how do we study them? The answer to all these questions can be found in out first video. So strap in and hit play.


Key points to take away from this video are:

  • Microfossils are fossils that are small enough that they are best studied using a microscope
  • Thus, microfossils are a taxonomically diverse and heterogeneous group
  • They are extracted from rocks in a number of ways (e.g. using acids), and studied via microscopy
  • They are used in a wide range of subdisciplines, especially when fossils are recovered via boreholes

Siliceous Microfossils

For our remaining videos, we're going to have a quick trip through the wonderful world of microfossil groups. These are organised by the composition of their hard parts. This is a useful way to categorise microfossils for our purposes, as it dictates how we extract and study them. With that, let's meet our first group of microfossils – those which make their hard bits out of silica (silicon dioxide, SiO2).


Key points to take away from this video are:

  • Diatoms are a group of algae with complex silica skeletons that have been around from the Jurassic to today
  • They come in two flavours: centric (round valves, a bit like a petri dish, mostly marine) and pennate (elliptical valves, mostly freshwater)
  • Radiolaria are solitary or colonial eukaryotes useful for biostratigraphy from the Cambrian onwards

Lets meet some siliceous microfossils

I'm afraid the majority of these microfossils are so small that creating 3D models from the fossils themselves is really challenging. As such we're going to have to go with digitally sculpted 3D models (as opposed to ones created using the actual object), or photos taken down a microscope, rather than 3D models. But hopefully it'll be enough to give ou an idea of what they look like.

Note: I also have had to use a variety of sources for the 3D models on this page. The creator (and thus copyright holder) is shown in the top left of each, and you can visit the source by clicking on the logo bottom left. It also means that these links are more likely to break than my normal ones. If this has happened, I'd appreciate it if you could let me know via email.


Diatoms are a form of algae with a silica skeleton, you will recall from the video. Remember that diatoms were split into two groups. A single frustule of a centric diatom – the kind typical of marine environments – is shown below.

A single frustule of a centric diatom - typically 1/100th - 1/10th of a mm in size.

Cool cool. Now let's meet the other type - a pennate diatom, more normally found in fresh water.

A 3D model of the diatom Diploneis.

This is actually based on the SEM image shown below (and sourced from the same page as that 3D model).


And since they're gorgeous, let's check out a 3D model of a radiolarian.

Phosphatic Microfossils

Next up, we have microfossils whose hard parts are made of phosphatic materials. Often such fossils are the remnants of vertebrates. The only group we're going to meet in depth is one such example, and comprise small calcium carbonate fluorapatite, or francolite, fossils (this form of apatite has the the formula (Ca,Mg,Sr,Na)10(PO4,SO4,CO3)6F2-3).


Key points to take away from this video are:

  • Conodont elements are tooth-like microfossils between 0.25 and 2mm in size
  • They represent the remains of an extinct vertebrate, around from the ~Precambrian to Triassic
  • They are particularly useful for early Palaeozoic biostratigraphy

Lets meet some phosphatic microfossils

Isn't that cool? Weird extinct vertebrates known primarily from their teeth!


The model below shows a range of the different elements associated with the ozarkodinid conodont apparatus. This group was – in the Palaeozoic – amongst the most successful groups of jawless vertebrates.

Ozarkodinid Conodont Apparatus by AVZ.

That 3D model doesn't give you a great idea of how these elements actually look when they have been kicked around a bit and then found in a rock though. For that, see the image below from a paper on conodont biostratigraphy.

Examples of conodonts as found in a rock – these ones from the Ordovician of Argentina. Scale bar 0.2 mm Source: Feltes, N.A., Albanesi, G.L. and Bergström, S.M., 2016. Conodont biostratigraphy and global correlation of the middle Darriwilian-lower Sandbian (Ordovician) Las Aguaditas Formation, Precordillera of San Juan, Argentina. Andean Geology, 43(1), pp.60-85.

Calcareous Microfossils

Now we're onto the biggie. Calcareous microfossils – those things that make their hard parts out of various forms of CaCO3. There are a few important groups, so let's jump right in.


Key points to take away from this video are:

  • Calcareous nanoplankton a very small, unicellular phytoplankton – around from the Late Triassic to today
  • Amongst the most abundant are coccolithophores – single celled algae
  • Foraminifera are single celled amoeboid protists which typically produce a chambered test (shell)
  • They have been around from the Lower Cambrian to today, and are particularly useful for palaeoenvironmental analysis
  • Ostracods are small arthropods (i.e. animals) whose bivalved shell often survives as a microfossils

Lets meet some calcareous microfossils

This is our biggest group – there are a wide range of important calcareous microfossils. Let's meet them in a little more detail.

Calcareous nannoplankton

Oooh, this model is actually based on a really high resolution CT scan in a particle accelerator called a synchrotron! Want to know more? Ask Russell in person and he'll happily describe how this all works.

Coccosphere Gephyrocapsa oceanica, 8 microns in diameter. Model by synchrotron européen ESRF à Grenoble, France


Onwards – to the forams. As per my video, this is a really important group. Let's meet a few of them. First off we have a fairly recognisable marine, benthic species (Elphidium (=Polystomella) crispa):

Foraminiferan Polystomella crispa – this is actually an enlarged teaching model. Forams are typically 0.05-0.5 mm.

Do remember, this is just a single-celled organism – neat, huh? Let's now meet a typical planktonic foram – these have been around for a shorter time, and there are fewer of them (mostly in the suborder Globigerinina if you're interested):

Foraminiferan Globigerina bulloides – also an enlarged teaching model. Forams are typically 0.05-0.5 mm.


Sweet. Now let's meet the final major group I introduced – the ostracods. You may remember these are small crustacean arthropods. This time our model is a little different – this is a limestone with a whole range of fossil debris in it. The kidney-bean shaped things are the ostracods.

Ordovician limestone from Lafayette County, Wisconsin (PRI 76750). Maximum dimension ~15cm.

As you can see, these are generally a little chunkier than the other microfossils we've met.

Organic-Walled Microfossils

Let's finish with organic-walled microfossils – a class of microfossils whose study is often referred to as palynology. This is basically the stuff that is left over after dissolving a rock with the strongest acids we have.


Key points to take away from this video are:

  • Be aware of the safety precautions when preparing palyntological samples!
  • Spores and pollen are the remnants of the reproductive cycles of terrestrial plants
  • They are widespread and commonly used for biostratigraphy and palaeoclimate analysis

Lets meet some palynology samples

These little guys are so small that you're most likely to only see them under a high powered light microscope or using a scanning electron microscope.

Pollen and spores

Given their size, I thought the most useful thing here to give you would be an images showing that they look like. This is a false-coloured SEM microscope image of various types of pollen:

Pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomoea purpurea), prairie hollyhock (Sidalcea malviflora), oriental lily (Lilium auratum), evening primrose (Oenothera fruticosa), and castor bean (Ricinus communis). Source.

Pollen are released during the reproductive cycle of flowering plants (= angiosperms). Those plants which are not flowering plants (there are a few groups) release spores. Here are some from a moss:

Spores of the moss Bartramia ithyphylla by Kristian Peters. Source.

This is the end

The Breakfast Club closing scene