New species discovered: how many are described each year, and how the process actually works, explained

The phrase makes it sound like an event: someone pushes through undergrowth and finds an animal nobody has seen. Occasionally that happens. Far more often a new species discovered this year was collected a decade ago, sat in a drawer, and became a species when somebody finally had the technique and the time to look at it properly.

What counts as a new species discovered

A species description is a formal scientific description, published, that does two things: it describes the organism, and it explains how the organism differs from species already described and from its close relatives. The second half is the real work. Finding something unfamiliar is not the same as demonstrating that it is not a variant of something already named.

For the name to be valid it has to follow the relevant nomenclature code. There are three that cover most of life: the International Code of Zoological Nomenclature for animals, the International Code of Nomenclature for algae, fungi and plants, and the International Committee on Taxonomy of Viruses for viruses. The codes impose formal criteria rather than editorial judgement, and one of the firmest is that the description must designate at least one type specimen. A description will usually also carry photographs or other illustrations of the type material and state where that material is deposited, so that anyone disputing the claim later has something physical to go back to.

How many new species are discovered each year?

The answer is in five figures and it has been rising.

The International Institute for Species Exploration, which tracked this for years, reported 19,232 species named in 2009, up 5.6 per cent on the year before. More recent analysis puts the current rate above 16,000 a year, with an average of more than 16,000 annually across 2015 to 2020, including more than 10,000 animals. Of roughly 16,000 in a year, something like 6,000 are insects.

Those figures matter mainly because they contradict a common assumption. The intuition is that the easy discoveries were made in the nineteenth century and the rate must be falling. It is not. When people ask how many new species are discovered each year and hear a number that large, the usual follow-up is whether the count is being inflated by splitting existing species. Some of it is. Most of it is not.

Set the annual rate against the totals and the scale of what is left becomes clear. About 1.9 million species have been described. Estimates of how many exist run to roughly 8.7 million. At 16,000 a year, the arithmetic on the remainder is not encouraging.

How the naming process works, explained

The sequence, briefly explained, runs: collect, compare, describe, publish.

Comparison is where most of the elapsed time goes. Every new species discovered has to be checked against the type material of every plausibly related species, and that material is distributed across institutions in different countries. This is why a specimen can be recognised as unusual in the field and still take years to acquire a name, and why museum backlogs are a genuine bottleneck rather than an administrative excuse.

Publication is the moment the name becomes available. In zoological terminology, a name becomes valid with the date of publication, which means the paper is not a report of a decision made elsewhere. The paper is the decision.

A worked example: the dragon ants of New Guinea

In July 2016, Eli Sarnat, Georg Fischer and Evan Economo published a taxonomic revision of the Pheidole cervicornis species group in PLOS ONE, under the title Inordinate spinescence. Two of the species in it were new: Pheidole drogon and Pheidole viserion, named after dragons in Game of Thrones, from the rainforests of Papua New Guinea. The spines on the workers do genuinely resemble a wing and a claw, which is where the naming came from.

The interesting part is not the name. These are big-headed ants, and the team used microtomography, essentially 3D X-ray imaging, to look inside the spines rather than only at their outline. What they found was a division of labour written into the anatomy: in workers with large heads the spines contain muscle fibres, apparently helping to support the weight of the head, while in workers with smaller heads the same spines are practically hollow.

That is a discovery you cannot make with a microscope and a steady hand. It is also a good illustration of why the rate of description keeps climbing: a technique that lets you see internal structure without destroying the specimen turns a drawer of preserved ants into a source of new information.

Why the count keeps rising

Three things push it up.

Imaging and sequencing keep getting cheaper, which means characters that were previously invisible become available as evidence, and populations previously lumped together get separated on grounds that would not have been arguable before.

Collections keep being worked through. A large fraction of every year’s new species discovered has been sitting in institutional hands for a long time, waiting for somebody with the right training to open the drawer.

And undersampled groups stay undersampled. Insects account for a large share of annual descriptions and an even larger share of the estimated remainder, and the number of specialists able to describe them is small relative to the task. The bottleneck is not the supply of unnamed species. It is the supply of people who can name them.