Agapornis longipes

with the sites where A. longipes fossils have been found labeled|alt=Drawn map showing fossil location All known fossilized remains of Agapornis longipes originate from the Cradle of Humankind, a World Heritage Site about northwest of Johannesburg, South Africa and consisting of many fossil-bearing caves. The first to be discovered were found decades before the species was named. In 1969, T.N. Pocock reported that remains of lovebirds belonging to the genus Agapornis have been discovered at the Kromdraai fossil site (one of the caves that would later be designated as part of the World Heritage Site). He believed that two species were represented by these specimens, a smaller species around the size of a budgerigar and a larger species, but did not assign any of the specimens to any named species. The presence of at least one lovebird species at Kromdraai was further confirmed in 2010, when Thomas A. Stidham reported that the fossilized humerus of a small lovebird had been discovered during excavations at the site between 1977 and 1980, and was being housed in the Transvaal Museum. Stidham also added that the lovebird remains reported by Pocock had been lost. However this turned out to be incorrect, and those remains are actually kept at the Evolutionary Study Institute at the University of the Witwatersrand. In 2024, a study on the fossil lovebird remains found in the Cradle of Humankind was published. The authors of the study analysed specimens housed in the University of the Witwatersrand and the Ditsong National Museum of Natural History, including those formerly studied by Pocock, Stidham or Pavia, and concluded that they represent a single new species. The name Agapornis longipes was given to this species, with the specific name derived from the Latin words longus (meaning "long") and pēs (meaning "foot"). Bones of this lovebird were uncovered in three caves in the Cradle of Humankind, namely Kromdraai, Cooper's Cave and Swartkrans, and the authors described a series of remains found between 1979 and 1986 by paleontologist Bob Brain in detail. Birds have fragile bones, so fossils of small birds such as Agapornis are typically found in small fragments, but A. longipes was unusually represented by 96 bones, some entirely complete and others incomplete. ==Description==

of a pair of Agapornis longipes|left Agapornis longipes was a small species of parrot with relatively large legs compared to other lovebirds. Its wing bones are comparable in size to those of the extant Fischer's, Lilian's and black-cheeked lovebirds, suggesting it was about as large as these small modern forms. However, the tarsometatarsus (a bone in the lower leg) of A. longipes is closer in size to that of larger lovebird species such as the black-winged and rosy-faced lovebirds. This makes the ratio of humerus to tarsometatarsus length in A. longipes the smallest of all known Agapornis species, indicating this species had long legs for a lovebird. Intraspecific variation in size is known in A. longipes, with some individuals being larger than others, though the ratio of wing length to leg length remains the same regardless of an individual's size. There is also a continuous ridge connecting the pisiform process to the alula process, a feature not seen in other lovebird species. A single tibiotarsus of A. longipes is known, and is similar in structure to that of other lovebirds (and unlike most other African parrots). The tarsometatarsus has a canal where both the flexor hallucis longus muscle and the flexor digitorum longus muscle would have been attached, and a separate canal is present for the superficial flexor tendons. Such a canal structure of the tarsometatarsus is also known in other Agapornis species, as well as the related hanging parrots of the genus Loriculus. In A. longipes, the trochlea (pulley-like grooved structure) at the head of the third metatarsal protrudes further and is wider at the proximal end than in any living lovebird species, and the tarsometatarsus is also straighter and narrower at the proximal end. ==Paleobiology==

of two Agapornis longipes feeding on the ground during the dry season|left Because all but one living species of lovebirds eat mainly grass seeds and secondarily feed on fruit, it is believed that Agapornis longipes had a similar diet. While some extant lovebirds search for food in trees, the ones with comparably longer legs relative to their wings (namely the grey-headed, yellow-collared and Fischer's lovebirds) feed on the ground. A. longipes has the proportionally longest legs of all known lovebirds, suggesting that it lived primarily on the ground rather than in trees, feeding on grass seeds in the tall, dense vegetation of the South African grasslands. Even so, the breeding habits of A. longipes are still presumably similar to those of living lovebirds, which require tall trees with either natural cavities or holes made by other birds (such as African barbets and woodpeckers) to lay their eggs in. It was reported by T.N. Pocock in 1969 that one humerus found at the Kromdraai fossil site was of an immature bird, suggesting that the surrounding area was used as a nesting ground for A. longipes rather than simply being part of its non-breeding range. Known from a large number of fossil remains, including 24 specimens of at least seven individuals from Cooper's Cave, A. longipes was likely a common animal in its natural habitat, being the fifth most common bird in terms of percentage of identified remains at this site and the third most common in terms of number of individuals represented. The species may be similarly abundant in Kromdraai, where it is known from 23 specimens, but since these remains are spread across multiple stratigraphic layers, it is difficult to verify the true abundance of this bird there. Some of the A. longipes specimens from Kromdraai and Cooper's Cave come from deposits with numerous small animal remains, which are believed to be debris from fossilized owl pellets. In particular, the remains in the Kromdraai deposits are most similar to debris under roost sites of western barn owls, and fossils attributed to Tyto cf. alba are known from both localities. This suggests that barn owls used these caves as roosting spots and were at least an occasional predator of A. longipes. ==Paleoenvironment==

has not changed significantly since the time of Agapornis longipes.|alt=Photo of an open grassland with dry golden-brown grass Fossilized remains of Agapornis longipes have been discovered in three caves, namely the Kromdraai fossil site, Cooper's Cave and Swartkrans. These caves are situated within the UNESCO World Heritage Site of the Cradle of Humankind in South Africa, so named because this area bears fossils of early hominins spanning from the Late Pliocene to Late Pleistocene epochs. However, in spite of extensive searches, specimens of this lovebird have not been recorded from localities other than the aforementioned three caves. The environment that A. longipes inhabited was similar to the savanna and veld grasslands of modern South Africa. Living in the Cradle of Humankind, the species lived alongside a wide variety of other animals, including the hominins Paranthropus and Homo. Because the environment of A. longipes has not changed significantly, it is likely that the bird was driven to extinction by microclimatic changes or the extinction of a food source rather than a change in the general environment. However, the Kromdraai A. longipes specimens have been broadly considered to represent individuals which lived about 2.5 million years ago, near the boundary of the Pliocene and Pleistocene epochs. This rocky structure was likely influenced by erosion from a large stream or river, and the presence of a water body is further supported by the fact that fossils of ducks belonging to the genus Anas are represented. A gallery forest would have flanked this water body, as evidenced by fossils of forest-dwelling birds such as the black sparrowhawk (Astur melanoleucus) and a green pigeon of the genus Treron, and some particular species such as the pygmy owl Glaucidium ireneae and a roller of the genus Coracias would have required tree cavities to nest in. Swartkrans In Swartkrans, fossils of A. longipes have been uncovered from the Lower Bank of Member 1, the oldest of the fossil-bearing deposits in this cave. Analysis of the faunal assemblage suggests that the Swartkrans fauna originates from a mosaic of habitats made up largely of veld grassland with riparian woodland. The Lower Bank deposits at Swartkrans have preserved remains of many different animals which would have coexisted with A. longipes. As with Kromdraai, the most famous of these are the hominins, which include Paranthropus robustus and an early Homo species. Other primate fossils from the Lower Bank include those of the monkeys Theropithecus oswaldi, Dinopithecus ingens and Cercopithecoides williamsi. The majority of the large herbivores in this environment were bovids, with extant species such as the springbok (Antidorcas marsupialis), klipspringer (Oreotragus oreotragus), steenbok (Raphicerus campestris) and rhebok (Pelea capreolus) living alongside prehistoric taxa such as Antidorcas bondi and a species of Megalotragus, though equids such as Equus capensis and Hipparion lybicum were also present. Carnivoran fossils are also abundant in the Lower Bank, mostly representing extant species such as the lion (Panthera leo), leopard (Panthera pardus), African wildcat (Felis lybica), brown hyena (Parahyaena brunnea), black-backed jackal (Lupulella mesomelas), Egyptian mongoose (Herpestes ichneumon) and African clawless otter (Aonyx capensis), though there are also extinct species such as the hyena Chasmaporthetes nitidula. Other mammals represented in this fossil assemblage include the hyraxes Procavia antiqua and Procavia transvaalensis, the aardvark (Orycteropus afer), a springhare belonging to the genus Pedetes, and a pangolin of the genus Manis. Cooper's Cave Cooper's Cave is an extensive system and includes multiple distinct localities which have produced fossils, with the A. longipes specimens originating from a locality known as Cooper's D. Uranium-lead dating conducted in 2009 suggests that the Cooper's D deposits are approximately 1.5 to 1.4 million years old, while a more recent study from 2019 refined that estimate to an age of about 1.38 million years, dating to the Early Pleistocene epoch. Though geologically younger, the fossil assemblage at Cooper's D suggests an environment similar to that at Kromdraai, with open savanna being the dominant habitat, while rocky outcrops and woodland were also present. However, while rock-dwelling species made up most of the birds in Kromdraai, Cooper's D instead preserves more open grassland birds and almost no water-associated birds, suggesting that the environment had gradually become drier and more open by the time the Cooper's D deposits formed. Bovids are also well-represented, with remains of both modern species such as the greater kudu (Tragelaphus strepsiceros), common eland (Tragelpahus oryx), and springbok (Antidorcas marsupialis), and those of extinct forms such as Antidorcas recki and Megalotragus having been found. Though rarer than the bovids, fossils of equids such as Equus capensis and Eurygnathohippus cornelianus are also known from Cooper's D. The apex predators in this ecosystem were large felids of the genera Dinofelis, Megantereon, Panthera and Acinonyx, as well as hyenas including the brown hyena (Parahyaena brunnea), striped hyena (Hyaena hyaena), Crocuta ultra and Chasmaporthetes nitidula. Smaller carnivores at Cooper's D include felids of the genera Felis and Caracal, the mustelids Propoecilogale bolti and the honey badger (Mellivora capensis), and mongooses such as the Egyptian mongoose (Herpestes ichneumon) and marsh mongoose (Atilax paludinosus). ==See also==