Pronolagus humpatensis
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| Pronolagus humpatensis Temporal range: Pleistocene[1] | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Lagomorpha |
| Family: | Leporidae |
| Genus: | Pronolagus |
| Species: | †P. humpatensis |
| Binomial name | |
| †Pronolagus humpatensis Sen & Pickford 2022[2] | |
Pronolagus humpatensis is a small-sized fossil species of lagomorph that lived during the Pleistocene epoch[3] on the Humpata Plateau of Huíla, Angola.[4] Its remains have been identified in limestone rocks[5] found in the karsts of Huíla Province.[6] The species is known from fragmented leg, skull and jaw bones from multiple individuals.[7] Fossils have also been found in Namibia that may correspond to the species.[8] It was first described in a 2022 survey of extant and fossil Pronolagus species by Sevket Sen and Martin Pickford,[7] and was assigned to the genus mainly based on dental characteristics. It is one of only a few African fossil lagomorphs described.[8]
Across the African continent, lagomorph fossils are poorly documented. Many fossils are known from southern Africa, but detailed studies are lacking.[8] Winkler and Avery, in a 2010 work on the mammals of Africa, noted that no fossil species of Pronolagus were known at the time.[9] The fossil species Pronolagus humpatensis is the first of its genus to be described, besides the nomen oblitum (forgotten name) P. intermedius[10] named by Henry Lyster Jameson in 1909.[11] It was described in 2022 by Sevket Sen and Martin Pickford in their review of Pronolagus specimens and fossils.[12] The P. humpatensis fossils described in this study were collected in 1990[12] and are kept at the Regional Museum of Huila in Lubango. They were prepared by the dissolution of the surrounding breccia rocks by an acetic acid solution and a buffer solution of calcium triphosphate, followed by consolidation in a solution of glyptol, a type of varnish.[13]
Excavations in southern Africa have found evidence of Pronolagus prior to this species' first description. A 2019 excavation of breccias in Leba Cave, a location in the Humpata Plateau, discovered a single Pronolagus specimen near the surface.[14] A 2017 excavation from the Okongwe locality of Kaokoland (in Kunene Region, Namibia) discovered several lagomorph teeth that bore similarities to those of P. humpatensis, but were labeled as Pronolagus sp. (unidentified species).[15]
Taxonomy
Pronolagus humpatensis was described based on fossils of several individuals,[16] both cranial (belonging to the skull) and postcranial (from all other parts of the body) bones. In all, there are three mandibles from the right side of the skull, a skull fragment, a palate fragment with some cheek teeth; several postcranial bones, including five femoral fragments, ulna, tibia, and humerus fragments; astragalus, calcaneum, metacarpal, and phalanx bone fragments. The femoral fragments belonged to juvenile individuals, based on evidence of increased bone porosity and the missing head and greater trochanter.[17] These fossil fragments were excavated from limestone breccias and tufas in the Humpata Plateau from the Tchiua and Cangalongue localities.[16]
The holotype of the species (Tc 2'90) is a mandible fragment kept at the Regional Museum of Huila. It bears the teeth from the third premolar to the third molar and comes from the lower right side of the jaw. The specific name humpatensis is taken from its type locality, Humpata Plateau.[12] The limestones that contained the fossils date to the early Pleistocene epoch (1.8 to 1.3 million years ago).[1] A 2022 inventory of Angolan fossils placed the species in the Pleistocene according to Sen and Pickford's analysis.[18]
The genus Pronolagus was described as closely related to the extinct genus Alilepus by Claude William Hibbard in 1963, which was corroborated by Winkler and Avery in 2010. However, their analyses also place the genus as being closely related to Bunolagus (the riverine rabbit),[19] which has not been supported by studies of molecular data in 2004 by Conrad Matthee and colleagues, as well as in 2024 by Leandro Iraçabal and colleagues. These studies place Pronolagus in a clade with Poelagus (the Bunyoro rabbit) and Nesolagus (the striped rabbits):[20][21]