Polacanthus Reconstruction: Part 7 ‘Dorsal Spines’

I visited Dinosaur Isle Museum at Sandown on the Isle of Wight and whilst I was there I saw one of the Dorling Kindersley dinosaur models in the lab.

The Gastonia model has an original arrangement of spines.

The tall lateral (side) spines near the shoulders are quite striking compared with other reconstructions.

The model demonstrates the side row of spines from neck to the tip of the tail that formed Gastonia’s primary defense against predators.

The tail of Gastonia would have been a formidable weapon against medium to large theropods. Similar in effect to an Aztec Macuahuitl, the keratin covered tail spines would have probably caused significant lacerations to the lower body of any dinosaur unfortunate enough to be in the way of the swinging tail.

Suitable inspired, I returned to the Dinosaur Expeditions Centre at the Dinosaur Farm and decided to focus on producing a pair of dorsal (top) spines, notable for having a solid base.

I marked out the template on the foam with the keratin thickness outline added and started carving the shape out.

Once the first spine was finished I temporarily mounted it on the Minmi model to check how it looked.

I still need to blend the spine to match the body but the overall effect is imposing. So I repeated the process to make the opposite spine.

Next time I will sculpt a pair of Polacanthus spines based on a rare fossil.

Polacanthus Reconstruction: Part 6 'Cervical Spines'

With the first pair of Cervical (neck) spines done, I decided to base the next pair of (slightly bigger than half scale spines) on a plaster cast of a fossil Polacanthus spine rather than some small black and white photographs.

With the outline of the template marked out on the foam, I cut out one of the spines and started carving. A couple of hours later I had finished the left spine.

Before starting the opposite spine I thought it would be a good idea to mount the spine on the Minimi model to see how it looks. I temporarily attached the foam spine to the fibreglass model with a small piece of modelling putty

So far so good. Next I added the first cervical (neck) spine to check the effect of both spines together.

Obviously to finish the model they will need to be blended to fit when finally mounting them but the overall impression seems great.

An hour later I had carved the opposite spine.

So I mounted the pair of spines on the model.

Not too bad for a few hours work! Next I will look at a reconstruction of the Polacanthid Gastonia and sculpt a pair of  ‘solid-based’ scapula-coracoid spines.

Polacanthus Reconstruction: Part 5 ‘First Blood….’

With everything to hand I was finally in a position to actually do something. Before putting scalpel to foam I needed to create some templates to base the sculpted spines on.

The Minmi model is approximately half the size of an adult Polacanthus. Assuming the spines discovered to date are from adults (which is quite likely) then I would need to scale the spine to half actual size.

However there was another aspect to this reconstruction. The spines would be fine in their original condition for a skeletal reconstruction. However this was going to be a life-like, fleshed reconstruction. In life the spines would have been covered in keratin, like a crocodile scute.

So the spines would actually need to be slightly bigger than half size to take into account the keratin surface. With this in mind I selected the pre-sacral (neck to hip) spines images and set about drawing slightly bigger than half scale outlines.

Once left and right Cervical Spine templates were cut out I drew their outlines on the foam. (Note the ‘keel’ on the bottom of Spine 1 below was deliberately omitted on the foam as it would be embedded in the skin in life and would not be visible on the finished model).

I selected the first Spine and cut around the outline.

A few hours later I had sculpted both Left and Right Spines, but not before the scalpel blade caught the tip of my left index finger!!! So after a quick rumage through my first aid kit for a plaster, I donned a latex glove and a rubber glove to finish the sculpts.

With the light level dropping I decide to call it a day. My sacrifice had not been in vain!

Polacanthus Reconstruction: Part 4 ‘We can rebuild it….’

With Christmas and the New Year celebrations over for another year, the priority was to make a start on turning the Minmi model into a Polacanthus.

The modifications required include:

• A new head - based on Gastonia burgei.
• A number of spines and plates over the body and the tail.
• A Sacral Shield over the hips.

I went through my scientific papers on Polacanthus, Gastonia and their relatives to refresh my memory before putting pen to paper. Gastonia has the most complete skeleton of a Polacanthus relative and there are several mounted Gastonia skeletons on display in the United States. The first mounted skeleton was produced by Robert Gaston, Jennifer Schellenbach and James Kirkland (2001) in the Armoured Dinosaurs. They arranged the spines based on the best information available, so I decided to use this as the starting point of my attempt to reconstruct a Polacanthus.

The first thing to do was plan out the arrangement of the spines, scutes, the sacral shield and label them; this would allow me to break the task into ‘bite’ sized chunks.

Over forty spines, a fleshed skull and a sacral shield would need to be sculpted. So I would have my work cut out to get it ready in time for the end of March.

With time ticking the next task was to set-up a workshop space with everything required in easy reach.

Before starting to carve the spines I requisitioned the Children’s area (which explains the Dinosaur pictures on the walls), relocated the Minmi, set-up my drawing table, a heater and stuck my laminated inspirational pictures to the wall. With my Palaeontological Fortress of Solitude complete I was ready to get to work.

Polacanthus Reconstruction: Part 3 ‘The best laid plans…..’

The Minimi model made a great impression on the visitors to the Dinosaur Expeditions Centre as it helped to give the Wealden Floodplain diorama some context and scale. During guided tours we explained that it was a work-in-progress and pointed out what we were planning to add to the display.

The centre closed to the public at the end of the main tourism season in November 2013. The priority was to continue work on the Brachiosaur ‘Barn-sized Sauropod skeleton’. Unfortunately the time flew by and we couldn’t mount all of the newly sculpted bones before we had to stop and re-open for the start of the 2014 tourism season. Knowing that once the initial rush of the Spring holidays ebbed away the centre would be quiet for several weeks I had an idea!

The Minmi needed modifications to change it into a Polacanthus. The head was the wrong shape and lacking in certain details, the body and tail needed spines and the sacral shield over the hips needed enhancing. If the Minmi’s head was removed I could sculpt the modifications required to finish the head, add suitable taxidermy eyes and then reattach it back on to the body before the Summer Holidays. After discussing it with my fellow Directors and assuring them the work would be done with plenty of time to spare the decision was made to saw the head off!

It was a relatively simple to remove the Minmi’s head and drill-out the eyes. I had sourced some milliput from a local art shop and set-up a tray for the Dinosaur head, sculpting tools and materials. I made initial progress, but every time I started sculpting the phone would ring, or visitors would arrive and I would have to stop. I soon realised that not only was the sculpting material not delivering the result I wanted but I wasn’t going to finish the job in time for the Summer Holidays.

One of our visitors, Andre (a professional model sculptor) made recommendations on a different type of  sculpting material and I came-up with a new plan. Rather than bulk out the head to match the shape of a different dinosaur, it would be easier to put ‘flesh’ on a cast of the skull. The finished result would much more life-like but it would cost a lot more.

However before going to Plan B, I would have to explain to the other Directors what had gone wrong and that the cost of the job would go up significantly. Fortunately they were very understanding given the circumstances. However it was decided that we would have to wait until the end of the tourism season to ensure we could afford to order a cast of the skull and the professional sculpting material that would form the finished head.

In the meantime there was a headless Minmi / Polacanthus on the diorama, so I improvised by reusing part of the original cardboard packaging and a marker pen to produce a cardboard head. 

This provoked a lot of comment by visitors wondering what had happened to the dinosaur’s head? In some ways it became a feature of our guided tours of the centre in 2014 and it certainly engaged children and adults alike with the ‘reveal’ when the cardboard head was removed!

As the 2014 tourism season drew to a close, my attention returned to the forlorn looking dinosaur on the diorama and I resolved to get it finished over the coming winter.