''Hadrogeneios'' is an extinct genus of

afrotheria Afrotheria ( from Latin ''Afro-'' "of Africa" + ''theria'' "wild beast") is a superorder of placental mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephan ...

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

recovered from the Khouribga Phosphates of the

Ouled Abdoun Basin The Oulad Abdoun Basin (also known as the Ouled Abdoun Basin or Khouribga Basin) is a phosphate sedimentary basin located in Morocco, near the city of Khouribga. It is the largest in Morocco, comprising 44% of Morocco's phosphate reserves, and at ...

dating from the

Selandian The Selandian is a stage in the Paleocene. It spans the time between . It is preceded by the Danian and followed by the Thanetian. Sometimes the Paleocene is subdivided in subepochs, in which the Selandian forms the "middle Paleocene". Stratig ...

to the

Thanetian The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...

. Only the type species ''H. phosphaticus'' is known for this genus, with the material being of dental and jaw specimens. The placement of ''Hadrogeneios'' recovered it to be the most basal stem- paenungulate, the clade that includes

elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...

sea cows The Sirenia (), commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The extant Sirenia comprise two distinct famili ...

, and

hyrax Hyraxes (), also called dassies, are small, stout, thickset, herbivorous mammals in the family Procaviidae within the order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Modern hyraxes are typically between in length a ...

es. Despite this ''Hadrogeneios'' was a contemporary of more derived members of the group such as ''

Abdounodus ''Abdounodus'' ("Abdoun tooth") is an extinct genus of mammal known from the middle Paleocene of Northern Africa. The sole species, ''A. hamdii'', is known from teeth and jaw bones discovered in the Ouled Abdoun Basin The Oulad Abdoun Basin (al ...

'', ''

Ocepeia ''Ocepeia'' is an extinct genus of afrotherian mammal that lived in present-day Morocco during the middle Paleocene epoch, approximately 60 million years ago. First named and described in 2001, the type species is ''O. daouiensis'' from th ...

'', and the early

proboscidea Proboscidea (; , ) is a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Three l ...

ns ''

Eritherium ''Eritherium'' is an extinct genus of early Proboscidea found in the Ouled Abdoun basin (early Thanetian age), Morocco. It lived about 60 million years ago. It was first named by Emmanuel Gheerbrant in 2009 and the type species is ''Eritherium ...

'', ''

Phosphatherium ''Phosphatherium escuilliei'', named by Gheerbrant, Sudre and Cappetta in 1996, is a basal proboscidean that lived in Africa during the early Eocene, about 56-55 Ma. It is one of the earliest known proboscideans, together with ''Eritherium azzou ...

'', and ''

Daouitherium ''Daouitherium'' ("Sidi Daoui beast" from the name of the site where it was discovered) is an extinct genus of early proboscideans (a group including modern elephants and their extinct relatives) that lived during the early Eocene (Ypresian st ...

''.

Discovery and naming

The known material of ''Hadrogeneios'' 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 which ''Hadrogeneios'' came from was between the top of Bed IIb and the base of Bed IIa, which correlates to the

to early

. The specimens consisted of the holotype (MHNM.KHG.227), which has a mandibular symphysis with some partial left dentary, two sockets for the

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s, the first lower

canine Canine may refer to: Zoology and anatomy * Animals of the family Canidae, more specifically the subfamily Caninae, which includes dogs, wolves, foxes, jackals and coyotes ** ''Canis'', a genus that includes dogs, wolves, coyotes, and jackals ** Do ...

, and the first to third

premolar The premolars, also called premolar Tooth (human), teeth, or bicuspids, are transitional teeth located between the Canine tooth, canine and Molar (tooth), molar teeth. In humans, there are two premolars per dental terminology#Quadrant, quadrant in ...

s. Additionally there is also the presence of the fourth premolar and first molar, and an isolated left third molar. Several paratypes have also been described and those contain additional tooth remains and jaw fragments.

Etymology

The genus name of ''Hadrogeneios'' is composed of the Greek words ''hadros'' ("strong") and ''geneion'' ("chin") due to the presence of the large anterior part of the lower mandible. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''phosphaticus'' derives from the phosphate beds it was recovered from. Therefore this early afrotherian is the "phosphate strong chin".

Description

''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-placental

eutherian Eutheria (from Greek , 'good, right' and , 'beast'; ), also called Pan-Placentalia, is the clade consisting of placental mammals and all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distingu ...

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 of ''Hadrogeneios'' to ''Ocepeia'', the anterior lower tooth row is elongated in the former genus. The upper dentition is known from the second and third upper molars.

Classification

Below is a cladogram of the placement of ''Hadrogeneios'' based on a strict consensus of 180 MPTs from unweighted and unconstrained standard analysis with TNT 1.5 and with ordered characters:

References

{{Paenungulata Paleocene mammals of Africa Fossils of Morocco Fossil taxa described in 2023 Paleocene mammals Prehistoric placental genera Paenungulatomorpha