A New Giant Anaconda Species

A new giant anaconda species has been officially described in a scientific paper in the journal Diversity, and it is reshaping what we thought we knew about one of the world’s most iconic snakes. Researchers have named this new species the Northern Green Anaconda, or Eunectes akayima, and confirmed that it is genetically distinct from the well-known Southern Green Anaconda, Eunectes murinus. The study combines DNA analysis, body measurements, and formal taxonomic work to show that what was once treated as a single “green anaconda” is actually two separate species with different evolutionary histories and conservation needs.​

A New Green Anaconda Species Emerges

The description of Eunectes akayima was published in the open-access journal Diversity in 2024, in a paper titled “Description of the Northern Green Anaconda (Eunectes akayima sp. nov.)”. In this work, scientists formally separate the northern populations of green anacondas from the classic southern species, arguing that the differences are too large to ignore. The paper focuses on the snake populations living in and around the Orinoco Basin and adjacent regions, which include parts of Colombia, Venezuela, Guyana, Suriname, French Guiana, northern Brazil, Ecuador and Peru.​

For many years, herpetologists suspected that green anacondas might actually represent more than one species, but they lacked a comprehensive dataset to prove it. Previous genetic work hinted at deep splits between northern and southern populations, and the new Diversity paper builds on that by integrating genetics, morphology and formal taxonomic decisions into a single, detailed study.​

How the Researchers Proved It’s a New Species

The Diversity paper does not rest on a single line of evidence; instead, it uses multiple independent approaches to support the recognition of Eunectes akayima. First, the authors carried out mitochondrial DNA analysis comparing northern and southern green anacondas to quantify the genetic distance between them. They found that the level of genetic divergence is consistent with, and in some cases greater than, differences typically seen between recognized snake species.​

Second, the team compiled an unusually large dataset of morphological measurements, examining more than 1400 individual anacondas from across South America. They measured traits like total body length, tail length, head proportions and other body ratios, with special attention to differences between males and females, also known as sexual size dimorphism (SSD). By comparing these measurements across the range, they showed that northern and southern populations do not simply form a smooth continuum but display distinct patterns, supporting the idea of two species.

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Third, the researchers used biogeography and evolutionary timing to place these differences in a broader context. By combining molecular clock analysis with fossil evidence and known geological history, they estimated that the northern and southern green anacondas split from a common ancestor roughly 10 million years ago. This long period of independent evolution further strengthens the case that they represent separate species rather than local variants.​

Cleaning Up Taxonomy and Naming the Northern Green Anaconda

An important part of the Diversity paper deals with taxonomy—the rules and procedures for naming species under the International Code of Zoological Nomenclature (ICZN). Over time, multiple names and descriptions had been applied to green anacondas, creating confusion about which name should apply to which population. The authors carefully review this history and then use ICZN rules to stabilize the nomenclature of the group.​

In doing so, they formally describe the Northern Green Anaconda as Eunectes akayima sp. nov., while retaining Eunectes murinus for the Southern Green Anaconda. They also designate a neotype for E. murinus, which means they choose a modern specimen to serve as the official reference for that species, clarifying what exactly the name “murinus” should be attached to. This is crucial for future research because it gives other scientists a clear standard for identification and comparison.​

The name “akayima” is not randomly chosen; it has a cultural and ethical dimension. The authors explicitly state that they draw the name from Indigenous languages in the region as a way to honor Indigenous nations and their connection to the land and its wildlife. They argue that zoology and species naming have historically been dominated by Eurocentric traditions, and that incorporating Indigenous perspectives and names is one way to make taxonomy more inclusive.​

Sexual Size Dimorphism and Biological Differences

Beyond naming, the Diversity paper also looks closely at how male and female anacondas differ in size in each species. Green anacondas are famous for extreme sexual size dimorphism, with females often much larger than males, and this study refines how that pattern works in different parts of their range. By comparing SSD in Eunectes akayima and Eunectes murinus, the authors show that the degree and pattern of size differences are not identical between the two species.​

This has implications for understanding their reproductive biology, ecology and behavior. For example, differences in body size can affect how mating balls form, how many males can compete for a female, and how each species uses its habitat. The paper suggests that these ecological and behavioral dimensions are part of what sets the northern and southern species apart, even if they appear similar to a casual observer.​

Scientific Debate and Skepticism

Like many major taxonomic revisions, the recognition of Eunectes akayima has not gone unquestioned. An editorial or commentary later raised skepticism about parts of the broader anaconda revision, especially regarding how several yellow anaconda forms were interpreted. However, that critique did not present new original data; instead, it mainly challenged how existing evidence was being interpreted.​

In contrast, the Diversity paper is built on long-term fieldwork, large sample sizes and multiple independent lines of evidence, all presented with detailed methods and references. The ongoing discussion is part of the normal scientific process, where hypotheses are tested, questioned and refined over time. For now, Eunectes akayima stands as a well-supported species in the literature, and further work will likely continue to clarify the picture.​

Conservation Urgency for the Northern Green Anaconda

One of the most important messages of the Diversity paper is about conservation. When green anacondas were treated as a single widespread species, they appeared relatively secure because their combined range covered much of tropical South America. But once scientists split them into two species, a new reality emerges: the Northern Green Anaconda has a smaller and more restricted distribution than its southern counterpart.​

This makes Eunectes akayima more vulnerable to habitat loss, river modification, oil extraction and other human impacts in the Orinoco and northern Amazon regions. The study notes that recognizing this northern population as a separate species forces conservation planners to reassess its status and threats. In other words, taxonomy is not just an academic exercise; it directly influences how species are prioritized for protection and how resources are allocated on the ground.​

The paper also aligns with reports that many of these habitats are under pressure from infrastructure projects, deforestation and pollution, especially in areas overlapping Indigenous territories. By tying together scientific classification, cultural recognition and conservation concerns, the Diversity article presents Eunectes akayima not just as a new name, but as a symbol of how much we still have to learn—and protect—in the world’s largest tropical rainforest.

Sources / References:
Rivas et al., 2024, Diversity – Description of the Northern Green Anaconda (Eunectes akayima sp. nov.).​
National Geographic – Scientists reveal new green anaconda species.​
Mongabay – New giant anaconda species found on Waorani Indigenous land in Ecuador.​

VU Amsterdam research portal – Revealing a New Green Species and Rethinking Yellows.​