Rabbi Heller was presented with a problem. The Torah mandates that for a fish to be considered kosher, it must possess fins and scales. The Talmud states that every fish that possesses scales, also possesses fins. But Rabbi Heller was presented with a specimen of a fish that appeared to contradict this principle:
...When I was Av Beis Din… in Vienna, the scholar Rabbi Aharon the doctor brought me a fish called Stincus Marinus in the local tongue. It is found in the Spanish sea, and it is poisonous, and the pharmacists know techniques for removing the poison, and then they make various remedies from its flesh. …It has scales over all its body, and it does not possess any fin, but rather it has four legs like those of a domesticated or wild animal. (Ma’adanei Yom Tov to Rosh, Chullin 68:5)
The fact that the Stincus marinus had legs and would thus not be zoologically classified as a fish does not automatically help; the Torah does not follow the classification system of modern zoology (and hence bats are listed amongst the non-kosher birds). Still, Rabbi Heller proposed this as a possible solution, suggesting that it is classified as an aquatic animal rather than a fish, and is not part of the Torah’s discussion. He also suggests another possibility, that it is a hybrid creature produced after Talmudic times, and thus not included in the Talmudic principle that every fish with scales also possesses fins. But Pri Chadash considers both of these explanations difficult, and answers instead that the Stincus marinus must have indeed had fins at some stage in its life, and that it is indeed kosher. Rabbi Yonasan Eybeschitz, on the other hand, is not bothered by the Stincus marinus at all; he explains that, like all such principles, the Talmudic principle that every fish with scales also possesses fins is simply a general rule covering the majority, which could easily have exceptions.
As it turns out, there is an even simpler solution to the problem of the Stincus, later clarified by Chassam Sofer. The Stincus marinus, which I am watching in its vivarium as I type these words, is not only not a fish, it is not an aquatic creature at all. Instead, it is a lizard from the skink family, known by the Latin name of Scincus scincus. I was able to confirm this identification from nineteenth century works which refer to this animal by the name Stincus marinus and which say that it has long been known by this name. Furthermore, this lizard perfectly matches the description given by Rabbi Heller in Ma’adanei Yom Tov. The widespread legends of skinks possessing a poisonous bite or sting are baseless, but certain skinks are toxic if ingested. Scincus scincus was widely used in pharmaceutical preparations, and it is also sometimes known as Scincus officinalis (“pharmaceutical skink”).
But why would Rabbi Heller have thought that it was a type of fish? First of all, he clearly did not see a live specimen. And the dead specimen was presented to him under the name Stincus marinus, which means “aquatic skink.” The lizards of the genus Scincus are known in English as “sandfish.” This is because, although they are not aquatic, these skinks “swim” through sand, beneath the surface. On July 17th, the same day that I received my sandfish, the major science news outlets all ran a report about a breakthrough study on sandfish. It had previously been thought that sandfish swim through sand via a swimming stroke resembling the front crawl, pushing the sand behind it with its feet. But Daniel Goldman of Georgia Tech, in a study published in the journal Science, showed that this is only when they first enter the sand. Using high speed X-ray imaging, Goldman discovered that as soon as the sandfish is submerged beneath the sand, it tucks in its legs and swims through the sand by undulating its body, just like a fish. According to Goldman, “the results demonstrate that burrowing and swimming in complex media like sand can have intricacy similar to that of movement in air or water, and that organisms can exploit the solid and fluid-like properties of these media to move effectively within them.”
So the sandfish truly deserves its name, and it is not at all surprising that Rabbi Heller was told that it was an aquatic creature. Indeed, the idea of an aquatic lizard is not at all impossible; the Galapagos Islands are home to the marine iguana. The extraordinary secret of the Stincus is that you don’t have to be a fish in the water in order to swim like one.
(To subscribe to these essays by email, send an email to email@example.com.)