The scientific imaginary creatures (I): The history of Caminalcules


In On elephants and bacteria we always try to present unconventional theories, unique animals or just basically whatever has caught up our attention. In this new series of articles (we have not forgotten about Strangers in the animal tree….) we are going to look at the “pinnacle of imagination” in biology: the creation of scientific imaginary creatures.

Imagination, in the field of science is considered by many people as an obnoxious characteristic that downgrades the quality and accuracy of the rational scientific patterns. Although a good scientist should stick himself to the facts, a pinch of imagination is always needed to create theories, explain phenomena and set the basis for future studies.

So, although certain creativity can be expected in scientific procedures, this is not always the case, especially when “being imaginative” involves the complete creation of fictional organisms at the disposal of science. Here, we confront some of these creatures and ask ourselves; “What was the aim of their creation?” and “What can we learn from them?”.

This series will cover the four organisms in the upper image (we are not fully responsible for the quality of the drawing): Sinkers; the bold inhabitants of Jupiter, the Rhinogrades; the perfect example of island biogeography, the Caminalcules; examples for systematics and the Creatures of the Blind Watchmaker, which show the broad scope of evolutionary pathways from simple structures.

Caminalcules, the principles of systematics and evolution

Some of the Caminalcules (Sokal, 1983)

One of the main ideas of evolution is that organisms share a common history that relates them in time. Systematics tries to unveil this history by (mainly) finding common attributes in morphology (as well as genetic, developmental characters…) amongst current and fossil species. This is easier said than done, and anyone who has worked in this field knows the struggle they can suppose.

One of the most typical problems, for example, is to know whether the compared characters are either new or old or either important or unimportant. In order to solve this and other similar questions, scientists use a plethora of methods, thresholds, definitions… to try to uncover the most plausible evolutionary history. Although much has advanced and some of these problems have been already solved, the question “are we doing this the right way” sure came to the mind of many people working in this field.

One way to test if the methods used in systematics work correctly could be to try them on known evolutionary histories and see if the obtained history match the real one. However, given the usual slow pace of evolution, such a  “real” history has not frequently been obtained. That was especially the case in the 1960s, before the appearance of genomic data, but Joseph H.Camin, acarologist, was thinking about a solution.

His work, though, was not “re-discovered” until 1980s once he was already retired. It was then that the Caminalcules, named after their creator, entered the scientific scene. But what were they? They were, in fact, a complete group of imaginary animals, consisting of almost 60 species, both “living” and “fossil” with a complete evolutionary history.

A phylogenetic tree of the Caminalcules (Ulrich, 1993)

Camin had created a group of organisms for which only he knew their history. This was not only an interesting subject to try the common tools in systematics, but proved to have an additional advantage: they were unreal.

Not an imaginary creature, the soft turtle Chitra (Image from here)

That was (and maybe still is) a problem for many senior biologists working in systematics: the knowledge bias.  Too much knowledge is a drawback, indeed. Let’s give an example. Imagine the soft turtle Chitra. Is the disappearance of the shell something new or is just one proto-turtle which never grew a shell? Someone inexpert may go for the second one, giving Chitra the status of a relict. However, someone with knowledge about the history of turtles may say the appearance of shell predates the appearance of Chitra, which is highly improbable to be a relic from before shelled turtles, so it lost the shell. The knowledge about turtles, therefore, has conditioned the result of the evolutionary history.  This is of course an easy and logical example, but that is not always the case.

The Caminalcules, on the other hand, belong to no group (maybe vertebrata?) or known relatives, so they are immune to the knowledge bias. But, do we know anything from them at all? Well, as far as I know, Joseph H. Camin didn’t include any kind of data regarding ecology… But we could make a guess.

The first one is that Caminalcules are mainly aquatic animals. The basal stages may have been filter-feeding animals (hence the pores) attached to the surface via a sucker-resembling organ . Some of these organisms may have had a change in possible diet which favored an elongation of the head (clade A). Another lineage may have preferred, for example, to burrow into sand (clade F), in a similar fashion as the Hemichordates, having also enhanced filters in the shape of a fin which could also help for free-swimming.

Another clade may have preferred a freestyle slow-paced swim which could have caused the sucker to have changed into a small paddle (clade B). The DE clade may have entered shallow waters, thus favoring Caminalcules able to leave for land. Finnally, the C clade is definitely the most bizarre one  and hypothesis of their lifestyle are welcomed in the comment section.

The Caminalcules seemed to have helped in some systematic issues (Sokal, 1983; Blanchette et al., 2012) but were mainly ignored. Nowadays they are still used to learn about the principles of evolution and systematics by undergraduates. We studied them ourselves, back in our Bachelor days when we had fun naming them (worth mentioning my unique and subtle Caminalculate, Nisicaculatum subtilis or Propenduculata optima by the fellow writer Marc Riera). In this niche, therefore, they still exist and similar creatures, like the Didaktozoa by Ulrich Wirth have also been proposed.

Some of the Didaktozoa (Wirth, 1993)

Besides this, the Caminalcules are not a mere curiosity of the past, but an imaginative one.

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On the next issue…

It’s the 1970s and the space race is everywhere. Could other planets be inhabited? Which kind of animals would populate a drastic environment such as Jupiter? Floater, hunters, scavengers and sinkers, by Carl Sagan.


Blanchette, G., O’Keefe, R., & Benuskova, L. (2012). Inference of a phylogenetic tree: hierarchical clustering versus genetic algorithm. In Australasian Joint Conference on Artificial Intelligence (pp. 300-312). Springer Berlin Heidelberg.

Camin, J. H., & Sokal, R. R. (1965). A method for deducing branching sequences in phylogeny. Evolution, 311-326. (First appearance of the Caminalcules)

Gendron, R. P. (2000). The classification & evolution of Caminalcules. The American Biology Teacher, 62(8), 570-576.

Sokal, R. R. (1983). A phylogenetic analysis of the Caminalcules. I. The data base. Systematic Biology, 32(2), 159-184.

Wirth, U. (1993). Caminalcules and Didaktozoa: imaginary organisms as test-examples for systematics. In Information and Classification (pp. 421-433). Springer Berlin Heidelberg.



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