Parapliohyrax: Difference between revisions
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Revision as of 12:01, 29 April 2024
| Parapliohyrax | |
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Hyracoidea |
| Family: | †Pliohyracidae |
| Genus: | †Parapliohyrax Lavocat, 1961 |
| Type species | |
| Parapliohyrax mirabilis Lavocat, 1961
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| Species | |
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Parapliohyrax is an extinct genus of large hyracoid, a group today represented only by the diminutive hyraxes, but showing in fossil archives a large diversity in ecology and morphology. Parapliohyrax lived during the Miocene period, in various localities spanning the entirety of the African continent. Two species have been identified, based on cranial remains : Parapliohyrax mirabilis, the type species, known from the Miocene of Morocco and Tunisia, and P. ngororaensis, discovered in Kenyan and Namibian deposits. Isolated postcranial remains attributed to the genus have been identified in South African and Libyan deposits of the same age.
History
Description of P. mirabilis
The holotype specimen of Parapliohyrax, consisting of a relatively complete maxilla and an associated mandible, were first collected soon after the discovery in 1951 of the Beni Mellal fossil locality in Morocco. In 1961, René Lavocat identified the specimen as a new genus and species of hyracoid, which he named Parapliohyrax mirabilis. This description, however, was only superficial, the specimen still being encased in paraffin wax due to its extreme fragility. The fossil stayed in this state for more than a decade until 1977, when Léonard Ginsburg redescribed the holotype after a lengthy preparation, and attributed to the genus various mandibular remains and isolated teeth from the same locality preparated by Jacques Braillon.[1]
Description of P. ngororaensis
: Localities where P. mirabilis remains have been discovered.
: localities where P. ngororaensis remains have been discovered.
: localities where remains tentatively attributed to Parapliohyrax have been discovered.Between 1969 and 1975, extensive excavations in the Ngorora Formation in the Great Rift Valley of Kenya led to the discovery of cranial remains belonging to a new type of large hyracoid. In 1977, Martin Pickford and Martin S. Fischer formally described these new remains as a distinct species, Parapliohyrax ngororaensis.[2] In 1996, additional remains of P. ngororaensis, discovered at Berg Aukas, near Grootfontein, Namibia, were described by Pickford.[3]
Additional assigned material
In 1999, the manager of a mine near Hondeklip Bay, in the Northern Cape region of South Africa, discovered in a diamond-bearing locality labeled "Nova pit" the remains of a fragmentary metapodial bone that was identified as that of a primitive horse. In 2003, after further inspection, Pickford concluded that this single bone belonged to a large hyrax, and attributed it tentatively, due to the lack of overlapping material, to P. ngororaensis, based on its presence in Berg Aukas at the time of the deposition of the Nova pit. Pickford mentioned in passing in the same paper the presence of P. mirabilis in Miocene deposits near Kairouan, in Tunisia.[4] In 2005, Tsujikawa Hiroshi described a single and isolated premolar tooth coming from the Lower Namurungule Formation, near Baragoi, Kenya, and considered the similarities with those of Parapliohyrax, classifying it as an indeterminate Pliohyracidae due to the paucity of the material and the lack of element of comparison with other taxa.[5] In 2006, an additional isolated metapodial discovered by R. J. G. Savage in the locality W of Djebel Zelten, Libya, was tentatively attributed to Parapliohyrax sp. based on its similarity with the Nova specimen.[6] In the same year, Jean-Albert Rémy and Mouloud Benammi mentioned in passing the presence of Parapliohyrax sp. in the Vallesian fauna of the Aït Kandoula Basin near Toundoute, Morocco.[7]
Description
Cranial material
Maxilla
Cranial materials of both species are relatively well preserved, and present a relatively complete dentition. The snout of P. mirabilis was noticeably longer than that of Pliohyrax, with a remarquably deep palate forming a palatine pocket overarching the rear suture of the palatine bones, that can be compared to that of modern lagomorphs, the springhare Pedetes, and the early astrapothere Trigonostylops ; overall, despite many similarities in the shape of the cranium, the skull was more elongated than that of modern hyraxes.[1] As in Procavia, the nasals were projected forwards.[2] The dentition of Parapliohyrax is distinctively more derived than that of most other extinct and modern hyraxes, to the exception of Pliohyrax. The first upper incisor was noticeably larger and stronger, slightly convex towards the palate with a marked bend, and bearing wearing on a posterior face devoid of enamel, as in modern hyraxes. Differences in size between specimens of those incisors were tentatively attributed by Ginsburg to sexual dimorphism. The second upper incisor was slightly spatulate and oriented towards the palate. The third upper incisor was diminutive, premolariform and triangle-shaped. The upper canine and premolar teeth were molariform and quite similar from each others, as in other large hyracoids like Pliohyrax and Megalohyrax. The molars are much stronger and elongated, with the hypocone of the jugal teeth increasingly protruding towards the back, giving the teeth a typical square profile with wear.[1]
Mandible
The body of the mandible of P. mirabilis was relatively high and concave, with a noticeable pit on the internal face between the second premolar and the second molar, similar to that of Meroehyrax, and another, smaller, pit on the external face between the first and the fourth premolar, delimitated towards the front by the mental foramen. The ramus of the mandible, incompletely preserved, seems to have been less vertical than that of the modern Procavia.[1] The lower incisors are spatulated adn dentelated, with a small first lower incisor, a second lower incisor quite strong and slightly coiled, and a third lower incisor triangle-shaped,premolariform and similar in its structure to that of bovids and cervids. The lower canine and premolar teeth are elongated and quite similar, by the presence of a W-shaped ridge crossing their entire section, to those of chalicotheres. The molars bear tubecles in the shape of curved crescents, with the third molar bearing an extensive, internally concave and crescent-shaped lobe, similar to that of modern horses.[1]
Postcranial material
The postcranial material attributed to Parapliohyrax is extremely scarce, a condition not uncommon among Cenozoic hyracoids. The only postcranial material attributed to the genus consist in metapodial bones. This attribution is only done tentatively, as there is no material overlapping between these bones and the cranial remains that are relatively well known. This attribution is therefore mostly based on the large size of the remains, only reached by Parapliohyrax in Africa during the Miocene, and on the presence of the genus in their general region.
Two metapodial bones have been tentatively referred to Parapliohyrax. The first one, discovered near Hondeklip Bay in Namibia, consist in the distal portion of a metatarsus, reaching 32.6 mm in its maximal diameter.[4] The second, coming from the Djebel Zelten region of Libya, is too fragmentary to determinate whether its a metatarsus or a metacarpus, 29 mm long in its largest diameter.[6] Overall, based on the fossil material, Pickford estimates that P. ngororaensis reached 80 kilos, the weight of the modern blesbok,[4] and the size of a donkey.[6]
Species
Parapliohyrax mirabilis
P. mirabilis is the type species of the genus. Described by Lavocat in 1961, it is known after a fairly complete holotype maxilla, an associated paratype mandible probably coming from the same specimen than the holotype, and several fragmentary and isolated teeth remains.[1] It has been identified in Beni Mellal, Morocco[1] and Kairouan, Tunisia.[4] It is reportedly slightly smaller than P. ngororaensis.[3]
Parapliohyrax ngororaensis
P. ngororaensis is the largest species of the genus, described in 1987 by Pickford and Fischer, based on KNM BN 1741, a fragmentary skull associated with a damaged mandible. It is known from the Ngorora Formation in Kenya and the Berg Aukas locality in Namibia. A fragmentary metapodial from the Nova Pit locality in South Africa has been tentatively referred to the species by Pickford in 2003. P. ngororaensis is known from an abundance of material in the Ngorora Formation, being present in the members B, C, D and E of the formation, with 57 specimens of varying preservation attributed to the species, the remains of crania and mandibles of adults and juveniles being only found in the members C and D.[2]
References
- ^ a b c d e f g Ginsburg, L. (1977). "L'Hyracoide (Mammifère subongulé) du Miocène de Beni Mellal (Maroc)". Géologie Méditerranéenne. 4 (3): 241–253. doi:10.3406/geolm.1977.1006.
- ^ a b c Pickford, M.; Fischer, M.S. (1987). "Parapliohyrax ngororaensis, a new hyracoid from the Miocene of Kenya, with an outline of the classification of Neogene Hyracoidea". Neues Jahrbuch für Geologie und Paläontologie. 175 (2): 207–234.
- ^ a b Tab Rasmusse, D.; Gutiérrez, M. (2010). "Thirteen: Hyracoidea". In Werdelin, L. (ed.). Cenozoic Mammals of Africa. University of California Press. pp. 123–145. doi:10.1525/california/9780520257214.003.0013. ISBN 9780520945425.
- ^ a b c d Pickford, M. (2003). "Giant dassie (Hyracoidea, Mammalia) from the Middle Miocene of South Africa". South African Journal of Science. 99 (7): 366–367.
- ^ Tsujikawa, H. (2005). "The Updated Late Miocene Large Mammal Fauna from Samburu Hills, Northern Kenya". African Study Monograph. 32: 1–50.
- ^ a b c Pickford, M. (2006). "Giant hyracoid from basal Middle Miocene deposits at Gebel Zelten, Libya". Estudios Geologicos. 62 (1): 495–498.
- ^ Rémy, J.-A.; Benammi, M. (2006). "Présence d'un Gomphotheriidae indet. (Proboscidea, Mammalia) dans la faune vallésienne d'Afoud AF6 (Bassin d'Aït Kandoula, Maroc), établie d'après la microstructure de l'émail d'un fragment de molaire". Geobios. 39: 555–562.
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