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After finding and mounting (- click here-) microfossils, and then going onto make my own slides (- click here-), I wanted to combine my microfossil slides with my reconstructions, such as my my recent belemnite reconstructions in watercolour (- click here-). The plan was to make a new type of slide, at a standard microscopy slide size, which has a painted background instead of the regular black or white on black grid.
1. The slide
The slide was composed of the components below. There was a backing piece of mounting card, stuck to a piece of watercolour paper, with two pieces of mounting card with the apertures cut out. Two bits of card are required, as the specimen is thicker than a single piece of card. This means that only small specimens can be mounted, with the height of the specimen being the limiting factor. The height can be reduced by sanding (this also creates a flat surface with a greater surface area for the glue to adhere to), although this partially destroys the specimen, so this decision is not to be taken lightly. As well as the components needed to make the slide, the usual slide cover and sticker is needed.
2. Neohibolites minimus belemnite
Due to the size restrictions on the specimens for these slides, the slide is made for the specimen, instead of the other way around. The first specimen I wanted to mount was a tiny belemnite guard (probably Neohibolites minimus) from the Speeton Clay Formation. I had not reconstructed this species before, when I painted watercolour reconstructions of belemnites (below), however the specimen is morphologically very similar Hibolites, as seen in the etymology. As a result, I decided to reconstruct this specimen in a similar way to Hibolites jaculoides, with similar fin morphology and colouration/patternation.
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| A reconstruction (watercolour) of three species of belemnite from the Speeton Clay Formation. To see the blog and full reconstruction process - click here -. |
I also decided to keep the enlarged hooks (mega-onychites). The brown-beige colour scheme was chosen as it differed slightly from the Hibolites jaculoides reconstruction, as well as matching the brown framer's tape used in the slide cover and the colour of the fossil. In hindsight, a colour scheme that contrasts with the colour of the fossil might have been better, in order to highlight the fossil, bringing the viewer's eye to it.
Having a similar reconstruction to the Hibolites jaculoides - the Tethayan marbled belemnite, this reconstruction should have a similar common name, and hence I've called it the minor marbled belemnite. While this isn't a particularly interesting common name, it is rather fitting given the species name in its binomial scientific name (minimus).
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Belemnite guard (possibly Neohibolites minimus) mounted on a slide, backed on a painted reconstruction. |
3. Orthocone nautiloids
After this slide, I painted two orthocone nautiloid slides. Orthocones are straight-shelled nautiloids, which similarly to belemnites are cephalopods. Orthocones can often be seen as (incorrectly) synonymous with Orthoceras, which is a wastebasket taxon. Orthocones can be found from the Late Cambrian to the Late Triassic, but are commonly found in the Palaeozoic. My specimens are from the Palaeozoic- more specifically the Mississippian of the Carboniferous.
The first orthocone nautiloid was from the regular flooded quarry site on Aughertree Fell near Green How, and was found in a shale band Five Yard Limestone Formation, Yoredale Group from the Brigantian Substage, Mississippian, Carboniferous (336-326 +/_ 1.6 Ma). I have found around 5 fragments of orthocone nautiloids at the locality, with two of the fragments joining together to create a complete specimen. The second specimen that I mounted in a slide was from Faulds Brow Quarry, which isn't far from the Aughertree locality, but differs in the bedrock geology. Instead of the Five Yard Limestone Formation, the limestone once quarried at the site belongs to the Scar Limestone Formation. This formation, does however include shale bands, given the position of the fossil within the quarry, as well as the type of preservation, I think the fossil may have originated from drift.
As stated, orthocone nautiloids, like belemnites, are cephalopods and similarly to belemnites only the hard parts are usually preserved (the shell in orthocones and the guard/rostrum in belemnites). One major difference however, is that fossils of belemnites have been found with soft body preservation (in lagerstatten), whereas no orthocone nautiloids have been found with soft body preservation (to my knowledge). As a result, where we know that some belemnites had hooks (onychites) on 10 arms, as well as arm length and proportions, we don't know these details about orthocone nautiloids [1].
Additionally, unlike belemnites, nautiloids are still represented by extant species from the genus Nautilus and Allnautilus. However, modern nautiloids aren't a direct modern analogue to their fossil counterparts. As well as obvious morphological differences in the shell, they also (along with ammonites) have an aptychus. Aptychi are a fossil of uncertain origin. Either they are a double valved 'closing hatch' or a double-plated beak. The interpretation and positioning of this unusual feature varies with reconstructions, but I have chosen to reconstruct it as a 'closing hatch' like hood, similar to the hood of modern nautiloids (although the modern hood is a very different feature as it is formed of soft tissue). For the morphology and positioning of arms, I decided to stick with a lower number than modern nautiloids, more like ancestral nautiloids (10). On one of the reconstructions I included two speculative specialised arms (tentacles), like many modern cephalopods.
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Painting the second reconstruction. |
As for the pattern and colour of nautiloids, I stuck with a classic Nautilus colour scheme of Indian Red and white. The shell of modern nautiloids are countershaded, with a red and white striped upper and just white/beige underside so, similarly to my belemnite reconstructions, the orthocones would be countershaded. Countershading is a colouration scheme that is found in many marine animals to blend in with their habitat, with a darker dorsal side and lighter ventral side. Sadly due to the design of the painting (being dorsal view) the full effect could not be seen. The pattern of orthocones has been preserved in some specimens [e.g. 2], so accurate patterns can be reconstructed and patterns can be speculated, based upon modern cephalopods and species with similar life habits.
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Orthocone nautiloid (I) fragment mounted on a slide, backed on a painted reconstruction. |
For the naming of the two reconstructions, I looked to modern nautilus names such as the crusty, king, emperor, pearly and white-patch nautiluses, as well as moth common names- orthocone nautiloid I is called the pearly orthocone and orthocone nautiloid II is called the tiger orthocone. Although naming reconstructions is ultimately arbitrary, it is fun to do and helps keep track of different reconstructions of the same species.
I really enjoyed the process of making these slides, from finding the fossil, to reconstructing and painting, until making the actual slide and mounting the specimen. I plan to do more in a similar style, but I'm sadly limited by by the size of the specimens, as well as their scarcity.
[1] Sordes, 2014. A rather unconventional life-reconstructions of orthocones. Accessed at https://tonmo.com/threads/a-rather-unconventional-life-reconstruction-of-orthocones.17213/ on the 29/08/2020.
[2] Turek, 2007. Colour Pattern in Early Devonian Cephalopods from the Barrandian Area: Taphonomy and taxonomy. Acta Palaeontologica Polonica. 54 (3).
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