Blog Posts From Curator of Micropalaeontology's blog Tagged With microvertebrates

How can something that small appear on TV?

Giles Miller — Fri, 24 Jun 2011 14:13:01 GMT

Film crews are not an uncommon sight behind the scenes at the Natural History Museum but they have never come to see me ... until recently, that is.

Filming takes place in the Palaeontology Department regularly for documentaries, with staff interviewed or specimens brought out from their cabinets for a few minutes of fame. Usually the film crews want large vertebrates like dinosaurs or early human fossils, and one or two members of staff are well known for regular appearances in the media. For example, an episode of the BBC TV show New Tricks was filmed after hours last November and recently the department was featured in the BBC Documentary Museum of Life.

At the time I was disappointed that no aspect of micropalaeontology was featured in the BBC’s programme. So it was a pleasant surprise when I was asked to provide some specimens for a Korean film crew from EBS (Educational Broadcasting System) who were making a documentary on the early evolution of life called "The Secret Lives". They wanted to know about the earliest armoured fishes, the arandaspids.

These early fish were probably poor swimmers, scrabbling around on the bottom of the shallow sea, filtering for food. They play an important role in helping us to understand the early evolution of vertebrates. For further details including a picture of a whole arandaspid fish see:

http://accessscience.com/studycenter.aspx?main=7&questionID=5120
http://tolweb.org/Arandaspida/16907

Perhaps my most important fossil discovery was some fragments of the arandaspid Sacabambaspis in a consultancy sample sent to me from Oman in 2005. I wasn’t expecting to find fish and certainly not anything as significant as this. Luckily for me a university colleague had a large grant to study them so he funded a trip there in November 2006.

Wadi Daiqa, Oman

Because they are so small we were not expecting to see any "in the field" and were expecting to have to take back rocks to the Museum to dissolve and analyse. However, on the final day of our trip I saw by my foot a specimen with some tiny fish fragments.

The specimens themselves appear on the surface of some rocks as tiny black specks so I was amazed that I managed to see them (especially as I was told on my return that I would need glasses for reading!).

As a result of my find we went back in 2007 to collect some more samples. The image below suggests that they should be easy to spot. However, this is the very best specimen discovered after days of searching and the fragments are much larger than the original find.

The film crew first wanted a close up of the rock...

Close up of the surface of the rock being filmed. Impoverished curators use a one pence piece for scale.

Filming a close up of the arandaspid fish fragment rock in the Palaeontology Imaging Suite.

Then they wanted me to talk about its significance and say what it tells us about early fishes and their habitat.

The Oman discoveries showed that the fish were present all around the margins of the ancient continent of Gondwana and not just in the southern regions as had previously been shown by the findings from South America and Australia. In the Ordovician period about 450 million years ago, Gondwana was an amalgamation of what we currently know as Africa, South America and Australia with some parts of China and the Middle East.

Rocks from similar geological settings have produced similar fish fossils from Argentina, Bolivia and Australia so we know that this particular type of fish lived in shallow waters on the continental margins of Gondwana.

After this they wanted to film a close up of some arandaspid scales and plates on a computer screen. The filming took place in the Palaeontology Department’s imaging suite where we used a Leica microscope with a Zeiss Axiocam digital camera to provide a close up of some of the specimens that we found.

Zeiss Axiocam set up in the Palaeontology Imaging Suite.

Here I was able to show a close up of the rock on the computer and to show some features of the microscopic fragments that were inside it. I have already photographed some fragments by scanning electron microscope (SEM) so I was also able to show some of these to illustrate the close up features of some arandaspid fish scales. The “oak leaf”-like tubercles are typical of this type of fish.

Scanning electron microscope image of a scale of Sacabambaspis showing oak-leaf tubercles. The scale on the bottom is 0.38mm so the width of the scale is less than 1mm.

Sadly, I’m not sure I’ll ever see the final product as I don’t think our TV gets EBS. However, I am happy to play a small part in researching into some of the earliest vertebrates to have lived on our planet.

What is micropalaeontology?

Giles Miller — Tue, 21 Jun 2011 10:14:15 GMT

The answer to this question is the straightforward part of this post: palaeontology is the study of fossils and micropalaeontolgy is the study of microfossils. Alas, that’s the easy bit done… what then, are microfossils?

I’ll assume that we all know what a fossil is (if not, I recommend starting here) so a microfossil must be a small fossil, right? Actually, this is a harder question to answer than you might think so here are some thoughts on how large a microfossil is, how old they are and how we manage them at the Museum.

Size

There is no agreed size below which a fossil stops being a large fossil and starts becoming a microfossil. Some people arbitrarily say that if you need to use a microscope to view a fossil then you are looking at a microfossil. However, some fossils we consider microfossils measure more than a couple of centimetres in diameter. The rocks that were used to construct the pyramids in Egypt contain microfossils that can be as large as a ten pence piece!

Photo of Egyptian pyramid courtesy of Bobbie Molloy.

This size delimiting definition also gets slightly difficult to use when you are studying the microscopic parts of a larger organism, for example the fossilised scales of a fish or a minute example of something that is usually larger like a gastropod (e.g. a snail). Most people studying these topics would consider themselves microvertebrate workers or gastropod workers and not micropalaeontologists. However, many micropalaeontologists, like me also study microscopic remains of larger organisms like fish that they find during laboratory preparations for other microscopic remains.

Biological classification

Some people try to restrict micropalaeontology to particular biological groups that are commonly considered microfossils. This can also be open to personal opinion, for example, palynologists study microscopic organic remains like spores, pollen and oceanic plankton – all microscopic in size – but some of them would consider themselves palynologists rather than micropalaeontologists. The Micropalaeontological Society defines its specialist groups to reflect biological classifications of organisms commonly accepted as microfossil groups.

Age

As with size, there is no agreed age beyond which something stops being recently dead and becomes a fossil. With specimens in this narrow window of age (ie 0-10,000 years old) it is virtually impossible to tell how old a microfossil specimen is without carrying out some sort of destructive chemical analysis on it.

Our collections

At the Museum, we mainly follow the Micropalaeontological Society's definition of a microfossil and in the Palaeontology Department we have collections of Foraminifera, Ostracoda, conodonts, Radiolaria, nannofossils and various palynological groups such as the dinoflagellates and spores. In future posts I will introduce each of these microfossil groups as I highlight projects that are currently happening here at the Museum.

My job is to manage all of these collections which number over 750,000 objects. It would be impossible to count the exact number of specimens because some slides and residues contain hundreds of thousands of specimens.

The lack of clarity over what age makes a microfossil causes problems sometimes with deciding where to store specimens in the Museum collections. In the Palaeontology Department we have all the extant (modern) Foraminifera as well as the fossil specimens, so no problem there. However, ostracods are split between our department and the Zoology Department, with us holding the fossils and Zoology the recent (extant) forms. In practise it is very difficult to draw the line between fossil and recent and we certainly have some ostracods that could be in the Zoology Department and probably vice versa.

The majority of the microfossil collections are Foraminifera, which are unicellular animals with a foramen (i.e. an opening, sometimes multiple) that form small shells of calcium carbonate, silica or organic materials. Examples of Foraminifera are shown below, where the field of view of the slide from the Heron-Allen Collection is about 2cm.

The Heron-Allen Collection

I mentioned that some micropalaeontologists like me also work on microscopic fragments of fish (microvertebrates). At the Museum these are kept with the fish collections so they do not come under my ‘jurisdiction’. However, I still study them and some of my most important discoveries have been on this subject as you will find out in the next post to the blog.