3D Models | The internal beauty of extinct nerineids

Fossils have long been reproduced as casts from artificial molds of original specimens, for pedagogical purposes, private collections or even exhibits (e.g. large dinosaur skeletons). Now, modern 3D printers allow reproducing not only the external morphology of a fossil but also their internal structures.

An example of these internal structures is displayed by the extinct Mesozoic gastropods Nerineoidea, with a more or less complex set of internal parietal, palatal and columellar plaits and folds (Fig.1).

Fig. 1 – Terminology of internal plaits on nerineoids (from Kollmann, 2014.)

Fossils of Nerinea s.l. are commonly mentioned in classes of Invertebrate Paleontology, namely those we give at the Department of Geology of the Faculty of Sciences of the University of Lisbon (Portugal). Specimens of this group are relatively easy to find in Cretaceous formations around Lisbon, namely in limestones of the Bica formation (Dinis et al., 2008), dating from the base of the Upper Cretaceous (Late Cenomanian). However, their shells are most of the time missing (the fossils are internal casts) or we can only observe them sectioned on surfaces of natural stones (Fig. 2) in buildings, monuments and squares from Lisbon surroundings.

Initially described and classified as Nerinea olisiponensis by Daniel Sharpe (1850) it is more recently recognized as Neoptyxis olisiponensis (Sharpe, 1850) by Ayoub-Hannaa & Fursich (2011).

Fig. 2 – Section of nerineids (Neoptyxis olisiponensis) on an Upper Cretaceous limestone from the surroundings of Lisbon. Note that the lime mud only partially filled the inside of shell of these gastropods with complex internal structure.

Because these gastropods are already extinct we proposed to a couple of Portuguese architects (Sandra Louro and Rui Casinhas) to reconstruct these shells first by defining the mathematical model of their helicoidal complex internal shapes and spaces, and second to produce them on a 3D printer.

The idea was to obtain realistic models of these gastropods to understand the natural biostratonomical processes by which carbonate sediments entered inside these turriculate (high spired) empty shells.

Because these models cannot (still) be produced in transparent materials we are not yet able to fully address the biostratonomical mechanisms (e.g. currents) by which sediment can enter the restricted spaces of these shells. However, we were able to obtain a 3D real size replica of the Neoptyxis olisiponensis (Sharpe, 1850), to illustrate in classes of Invertebrate Paleontology, since fossils of these shells rarely can be observed fully individualized from the limestone matrix.

Fig. 3 – Illustration of the 3D replicas of Neoptyxis olisiponensis (Sharpe, 1850) produced by Sr-3design (www.sr-3design.com.pt/sr3dprint/en/).

We use this realistic models to better visualize the internal complex morphology of these gastropods (difficult to reconstruct from 2D sections alone) on practical classes of Invertebrate Paleontology, to exhibit on Natural History Museums beside real fossil specimens, or during outreach activities of urban Paleontology along the facades of buildings and monuments in downtown Lisbon.

To continue to have the ability to work on these type of pedagogical and outreach materials, we need to produce the replicas in higher numbers. Believing they may be useful for colleagues who work in the same activities, we are proposing its acquisition to professors, divulgators, scientific institutions or others who might be interested.

You can order such replicas (each shell is produced as two non-symmetrical halves) (Fig. 3) at Half 1 – http://shpws.me/Idtw; Half 2 – http://shpws.me/Idtc. Click on the previous links to see the conditions and to order.

They’re not cheap (I have no commissions… – our intent is solely scientific and pedagogical), but taking into consideration all the mathematical development involved and that each half takes more or less 8 hours to be produced on a 3D printer I think it is totally worthwhile.

Bibliographic references:

Ayoub-Hannaa W. & Fürsich, F. T. (2011) – Revision of Cenomanian-Turonian (Upper Cretaceous) gastropods from Egypt. Zitteliana A 51,115 – 152.

Dinis, J. L., Rey, J., Cunha, P.P., Callapez, P. & Pena dos Reis, R. (2008) – Stratigraphy and allogenenic controls of the western Portugal Cretaceous: an update synthesis. Cretaceous Research: 29, p. 772-780.

Kollmann, H. A. (2014) – The extinct Nerineoidea and Acteonelloidea (Heterobranchia, Gastropoda): a palaeobiological approach. Geodiversitas 36 (3): 349-383.

Sharpe, D., (1850) – On the secondary district of Portugal which lies on the North of the Tagus. 1. Remarks on the genus Nerinaea with an account of the species found in Portugal. Quart. J. Geol. Soc. 6, 135–195.

Mário Cachão

Lecturer, researcher, author and consultant in Geology and Paleontology, affiliated with diverse national and international scientific organizations. Portuguese coordinator of ProGEO. Director of NanoLab and Rocha Amiga. (read more about me)