Researchers led by the University of Salford and international collaborators have identified two previously unknown howler monkey species in the Amazon rainforest: Alouatta iroi and Alouatta matogrossensis.

The team analyzed the genomes of 11 howler monkey species across South and Central America and combined the genetic data with morphological evidence from museum specimens to build the most comprehensive evolutionary history of howler monkeys ever documented.

According to phys.org, the study, published in Communications Biology, shows that what scientists had treated as a single species actually contains distinct evolutionary lineages.

The finding lands 85 years after the last howler species, Alouatta puruensis, was described by Lönnberg in 1941, and confirms that the world's largest tropical forest is more biodiverse than science had recorded.

The research also explains how this diversity arose.

phys.org reports that major rivers such as the Amazon, Rio Branco and Xingu have acted as natural barriers for millions of years, preventing howler populations from mixing and allowing them to evolve into separate species on opposite banks and in isolated forest regions.

The study directly addresses two long-standing problems in biology: the Linnean shortfall, meaning we do not know how many species actually exist, and the Wallacean shortfall, meaning we do not know where they live.

By mapping where each howler lineage occurs, the researchers gave conservationists a much sharper picture of which populations exist and where.

As Salford's Dr. Romina Batista put it, the Amazon still holds remarkable biological secrets even among well-known animals, and understanding which species exist is the first step toward protecting them.

The discovery arrives under a shadow. The study identified several populations that may face significant risk of extinction, including newly recognized species never previously assessed for conservation status.

phys.org highlights Alouatta matogrossensis, found in southern Amazonia, whose habitat is considered one of the world's fastest-deforesting regions because of cropland expansion, causing habitat loss and fragmentation.

Professor Jean Boubli of Salford's Environmental Research & Innovation Centre warned that rising deforestation, climate change and habitat loss threaten many Amazonian species before they are fully understood or even discovered by science, and said he hopes the findings help conservation organizations prioritize protection across the Amazon Basin.

One effort already working on that ground is the Reconecta Project led by conservationist Fernanda Abra, which reduces road mortality in arboreal species by connecting forest fragments, including habitat of the newly described Mato Grosso red howler monkey.

The howler find fits a striking broader pattern: even in well-studied animal groups, formal firsts keep emerging.

bioengineer.org reports that surveys in southwestern China identified Esolus fodingshanus, a new riffle beetle from Guizhou Province that marks the first documented occurrence of the genus Esolus in China and East Asia, collected in the Fodingshan and Fanjingshan nature reserves, while also confirming the close relative Esolus nepalensis for the first time in India's Uttarakhand State and Bhutan.

Both stories show the same lesson the Salford team stressed: species are still being discovered in places scientists thought they understood.