People have seen this frog thousands of times, but it is only now that they have realised it is a new species
Scientists have described a new species of frog that did not have to be sought out in an unexplored cave or a remote corner of the jungle. Pristimantis milpe is widespread in western Ecuador and southern Colombia; it is even found in areas disturbed by human activity and gives itself away at night with its loud calls. Yet for decades it was classified as a different species.
The answer was found thousands of kilometres away — in the collection of the Natural History Museum in London. A comparison of modern frogs with old museum specimens revealed that the name used by the researchers had been applied to the wrong animal altogether. As a result, the frog familiar to biologists was effectively left without its own scientific name – until now.
The new species had been right under our noses all along
Most stories about the discovery of new animals involve rare species with a tiny range. With Pristimantis milpe, the situation is almost the opposite.
According to the authors’ calculations, the species’ range covers an area of approximately 67,072 square kilometres. It is found in the Chocó region of western Ecuador and southern Colombia — from sea level up to around 1,200 metres. The species can live both in primary forests and in areas significantly altered by human activity.
Furthermore, the researchers characterise it as locally abundant. It is for this reason that the authors provisionally recommend classifying P. milpe as ‘Least Concern’.
In other words, the scientists found themselves faced with a rare taxonomic situation: the new species was ‘new’ primarily in terms of its scientific status, rather than because it was the first time a human had observed the animal.
The answer had to be sought in London
To understand the origin of the confusion, the lead researcher, Santiago Ron from the Pontifical Catholic University of Ecuador, travelled to London.
Old type specimens — the specimens historically associated with a species’ scientific name — are kept there. Such specimens are of particular importance to taxonomy: when a dispute arises over exactly which creature is referred to by an old name, researchers return to the original type specimens.
A comparison of these specimens with modern populations has shown that the frogs which, in recent decades, have been referred to as *Pristimantis subsigillatus* do not correspond to the animal to which this name actually pertains.
The error proved to be significant enough to require the reclassification of several names at once.
The old name belonged to a different frog
The authors reviewed the status of Pristimantis subsigillatus and concluded that this taxon should be regarded as the same species already known as Pristimantis latidiscus.
As the name P. latidiscus has priority, P. subsigillatus becomes its junior synonym — in simpler terms, it should no longer be regarded as a separate, valid species name.
But this raised a new problem. Numerous frogs from Ecuador and Colombia, which had been referred to as P. subsigillatus in the current literature, turned out not to be P. latidiscus.
It turned out that the population, well known to researchers, did indeed represent a separate species, but it had no correct scientific name.
This is how Pristimantis milpe came to be.
The name is linked to the Milpe Bird Sanctuary in the province of Pichincha in Ecuador. It is from there that the holotype – the specimen chosen as the primary reference for the new species – originates. It was collected in February 2020 at an altitude of around 1,150 metres.
The new species was not simply recognised because one group of frogs differed slightly in colour.
The authors took an integrative approach: they compared morphological characteristics, genetic data, evolutionary relationships and the animals’ vocalisations. The American Museum of Natural History has already added Pristimantis milpe to its list of new species described in 2026.
The mating call is particularly distinctive. Males of P. milpe produce a single note with a dominant frequency of around 2,581 Hz. In one of the closely related species, P. eremitus, the call consists of a series of three to nine notes, and the average dominant frequency is around 4,916 Hz.
In the wild, male P. milpe are active at night. They can climb onto the leaves of shrubs and bromeliads at a height of several metres and emit a loud, click-like call.
The females were found to be noticeably larger than the males
Sexual dimorphism is also pronounced in this species.
The body length of adult females in the studied sample was approximately 32.1–36.1 mm, whilst males reached only 24.2–27 mm. For these measurements, the authors used nine adult females and 12 adult males.
Colouration also differs. Females may develop bright orange or pale blue patches with black spots in the groin and on the hind limbs. In males, the colouration is usually more uniform.
To a non-specialist, these features may seem trivial, but together with genetics and vocalisation, they help taxonomists distinguish one closely related species from another.
How could an ordinary frog have remained ‘unknown’ for so long?
The story of Pristimantis milpe clearly illustrates that the number of species yet to be described cannot be reduced solely to animals that nobody has ever seen.
Sometimes an organism is well known, has been photographed, added to museum collections and mentioned in scientific publications — but is listed under the wrong name.
The new species itself had appeared in earlier works under the name Eleutherodactylus subsigillatus, and later as Pristimantis subsigillatus. The list of authors includes publications that used this name as far back as 1980 and then repeatedly in the 21st century.
It is therefore more accurate to speak not of a frog that science ‘overlooked’, but of a species that for decades was not recognised as distinct.
It was here that museum collections proved decisive: without the ability to refer back to historical specimens to determine which animal the old name actually referred to, it would have been far more difficult.
Old museum jars continue to yield new species
This research demonstrates why natural history museums have been preserving biological specimens for decades, and even centuries.
A type specimen serves as a kind of physical reference point for a name. Genetic methods and modern observations may become as accurate as one likes, but without the correct link between new material and historical specimens, errors may persist in the classification.
In the case of Pristimantis milpe, it was necessary to combine an old museum collection in London with modern data from Ecuador and Colombia. As a result, the new species was discovered not because scientists had finally found a rare frog, but because they realised which frog they had been looking at all these years.
Source
Authors: Santiago R. Ron, Poulette Paredes-Aguirre, Diego A. Paucar, Yaara López, Katherine Apunte, Jhael A. Ortega.
Journal: ZooKeys, volume 1286, pages 121–152. Published on 24 July 2026.