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| Hadrogeneios | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Infraclass: | Placentalia |
| Superorder: | Afrotheria |
| Clade: | Paenungulatomorpha |
| Genus: | †Hadrogeneios Gheerbrant,2023 |
| Type species | |
| Hadrogeneios phosphaticus Gheerbrant, 2023 | |
Hadrogeneios is an extinct genus ofafrotherianmammal recovered from the Khouribga Phosphates of theOuled Abdoun Basin dating from theSelandian to theThanetian. Only the type speciesH. phosphaticus is known for this genus, with the material being of dental and jaw specimens. The placement ofHadrogeneios recovered it to be the most basal stem-paenungulate, the clade that includeselephants,sea cows, andhyraxes. Despite thisHadrogeneios was a contemporary of more derived members of the group such asAbdounodus,Ocepeia, and the earlyproboscideansEritherium,Phosphatherium, andDaouitherium.[1]
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The known material ofHadrogeneios were collected from the local people from an unknown site in Ouled Abdoun Basin, though it is inferred they come from the Sidi Chennane quarry. Geochemical studies of the Paleocene mammals show phosphate intervals which suggested the bed of whichHadrogeneios came from was between the top of Bed IIb and the base of Bed IIa, which correlates to theSelandian to earlyThanetian. The specimens consisted of the holotype (MHNM.KHG.227), which has a mandibular symphysis with some partial left dentary, two sockets for theincisors, the first lowercanine, and the first to thirdpremolars. Additionally there is also the presence of the fourth premolar and firstmolar, and an isolated left third molar. Several paratypes have also been described and those contain additional tooth remains and jaw fragments.[1]
The genus name ofHadrogeneios is composed of the Greek wordshadros ("strong") andgeneion ("chin") due to the presence of the large anterior part of the lower mandible. Thespecific namephosphaticus derives from the phosphate beds it was recovered from. Therefore this early afrotherian is the "phosphate strong chin".[1]
Hadrogeneios is only known from the aforementioned gnathic and dental remains. Gheerbrant (2023) performed a CT scanning on the specimens in order to create 3D digital to create a composite reconstruction of the lower mandible. Based on the reconstruction,Hadrogeneios had a lower dental formal of 3i–c–4p–3m, a formula shared with basal placental or stem-placentaleutherian mammals. There are three postcanine diastemata. The first one is located between the lower canine and the first lower premolar, the second (longest) is between first and second premolars, and the third (shortest) between the second and third premolars. When comparing the lower mandible ofHadrogeneios toOcepeia, the anterior lower tooth row is elongated in the former genus. The upper dentition is known from the second and third upper molars.[1]
Below is a cladogram of the placement ofHadrogeneios based on a strict consensus of 180 MPTs from unweighted and unconstrained standard analysis with TNT 1.5 and with ordered characters:[1]
