Ammonite Drawing

[Koss1959]

Has anyone got any advice on drawing ammonites accurately? It is often the ribs which identify an ammonite, so they are very important to get right and while I my observational skills are fairly good, I find it hard to believe people like Ernst Haeckle relied purely on observation. I don't strive for Haeckle's realism as I draw in a more sketchy manner, but I do strive for accuracy all the same. Is there a sort of formula to plot ammonite ribs? Thanks! 

[Kane]

I've attempted before, and it may require less of the freehand observation approach, and more finding a way of plotting points along the spiral so as to know where the ribs go, and at what angles. Unlike drawing a clock where all lines can emerge and radiate from the centre at uniform angles, a spiral is trickier. There is a formula for drawing a spiral in general known in the Renaissance as the Golden Number, but that doesn't work perfectly for all ammonites. Rib angles will prove the most challenging, but it can be done if you're willing to integrate some mechanical help, like a camera lucida to faintly sketch the ribs' placement along the spiral.

[RuMert]

Not sure about the ribs, but here is ammonite reconstruction based on the current understanding

[grandpa]

Here is a good detailed article on the nautilus and the golden number (a.k.a. golden ratio) that may prove useful for drawing an ammonite.  Even if not helpful, it's entertaining reading to see how the arguments for and against the ratio of the nautilus go.

 

https://www.goldennumber.net/nautilus-spiral-golden-ratio/

 

[Koss1959]

Thanks for the help everyone. I think for the super accurate illustrations, I'm sure a camera lucida would be used, although I'm finding it hard to find much information on people using them when it comes to paleontological illustration. 

[Kane]

27 minutes ago, Koss1959 said:

Thanks for the help everyone. I think for the super accurate illustrations, I'm sure a camera lucida would be used, although I'm finding it hard to find much information on people using them when it comes to paleontological illustration. 

"There an app for that." -- Quite literally so! I've used it a lot to ensure my dimensions are accurate before laying down hard lines and details. Take a photo with a device, load it into the app, and you can reduce the opacity while it uses your camera to show your hand and pencil. 

[Mahnmut]

Aloha.

Although it does not give you all proportions of the spiral, a simple radial pattern may help. In my perception it makes it easier to follow the complex lines when you concentrate on the repeating relation to the radial sections.

You could also distort the pattern when starting to draw in perspective.

Cheers,

J

[Bringing Fossils to Life]

I don't like doing the shells, but I have done lots of research on the soft anatomy of ammonoids. These papers are very helpful in this regard.

Tentacle clubs:

https://www.nature.com/articles/s41598-021-89998-4?fbclid=IwAR1MjmlTjxXHUWRSlCrxgaFTylhnzsRM4Q_DjcHLX96eaj_xpGnQ04efefQ#Sec14

Internal organs:

https://sjpp.springeropen.com/articles/10.1186/s13358-020-00215-7

Orientation in shell:

https://www.researchgate.net/publication/273301771_Wrinkle_layer_and_supracephalic_attachment_area_Implications_for_ammonoid_paleobiology

Hope this helps! I will be posting a reconstruction of Koenenites (goniatite) soon.