Hyena phylogenetic classification
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Hyaenidae Family Phylogenetic Classification
The Hyaenidae family, once highly diverse during the Miocene, is now represented by only four extant species: the spotted hyena (Crocuta crocuta), striped hyena (Hyaena hyaena), brown hyena (Parahyaena brunnea), and the insectivorous aardwolf (Proteles cristatus) Terefe2014Rao2020. These species are the remnants of a lineage that included over 100 fossil species at its peak .
Evolutionary Relationships Among Extant Hyenas
Genomic and mitochondrial analyses show that the three bone-cracking hyenas (spotted, striped, and brown) are more closely related to each other, while the aardwolf forms a distinct lineage Terefe2014Rao2020. There is evidence of gene flow between the aardwolf lineage and the ancestral brown/striped hyena lineage, indicating complex evolutionary relationships within the family Terefe2014Rao2020. The aardwolf’s unique adaptations for insectivory, such as reduced dentition and craniofacial changes, are supported by both fossil and genomic data Terefe2014Catalano2024Rao2020.
Spotted and Cave Hyenas: Genus Crocuta
The genus Crocuta includes the extant African spotted hyena and the extinct Eurasian cave hyenas. Genetic studies reveal a deep divergence between African and Eurasian Crocuta populations, estimated at around 2–2.5 million years ago Westbury2020Westbury2021. Despite this split, there is evidence of bidirectional gene flow between these lineages after their initial separation, complicating their taxonomic classification Westbury2020Westbury2021Westbury2020. Phylogenetic trees based on mitochondrial DNA show that cave hyenas from Asia and Europe form distinct but related clades, with some Asian cave hyenas representing a deeply diverging mitochondrial lineage Rohland2005Westbury2021Westbury2020. The genetic structure of European cave hyenas was more complex than previously thought, with the Sicilian cave hyena forming a basal lineage within the group .
Striped and Brown Hyenas: Phylogeography and Diversity
The striped hyena (Hyaena hyaena) and brown hyena (Parahyaena brunnea) show low genetic diversity and little phylogeographic structure, likely due to slow declines in population size over the last two million years Hu2021Terefe2014Rao2020. Molecular studies confirm that striped hyenas in regions like Turkey belong to the H. hyaena species, and recent migrations from Africa to Eurasia have expanded their range Atay2021Hu2021. Brown hyenas display even less genetic diversity, with some studies finding only a single haplotype .
Aardwolf Lineage and Fossil Evidence
The aardwolf (Proteles cristatus) is the only extant hyaenid specialized for insectivory. Fossil discoveries, such as Gansuyaena megalotis from China, provide the closest morphological link to the aardwolf and suggest that its lineage diverged from small-bodied stem hyaenids before the evolution of the large bone-cracking hyenas . Phylogenetic analyses place extinct genera like Gansuyaena, Mesoviverrops, and Plioviverrops within the proteline lineage alongside the aardwolf .
Genetic Adaptations and Ecological Specialization
Genomic studies highlight adaptations in bone-cracking hyenas for scavenging, such as genes related to immunity and digestion, while the aardwolf shows adaptations for termite feeding Terefe2014Rao2020. All extant hyaenids share an expansion in olfactory receptor genes, indicating that a strong sense of smell was an early adaptation in the family Terefe2014Rao2020.
Conclusion
The phylogenetic classification of hyenas reveals a complex evolutionary history shaped by divergence, gene flow, and ecological specialization. The family Hyaenidae is now limited to four highly specialized species, each with unique adaptations and evolutionary trajectories. Ongoing genetic and fossil research continues to clarify the relationships among extant and extinct hyenas, deepening our understanding of their evolutionary past Westbury2020Hu2021Westbury2021+4 MORE.
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