''Palaeoamasia'' is an extinct

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

paenungulate mammal of the embrithopod order, making it distantly related to elephants, sirenians, and hyraxes. ''Palaeoamasia'' fossils have been found in Turkish deposits of the Çeltek Formation, dating to the

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

. It has unique

bilophodont The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

upper molars, an embrithopod

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

Discovery

''Palaeoamasia kansui'' (Ozansoy, 1966), the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

, was first discovered in Anatolia, Turkey in 1966. Since then, ''Palaeoamasia'' fossils have only been found In Anatolia. The fossil record of ''Palaeoamasia'' is scarce, although a new species of ''Palaeoamasia'' was discovered in 2014. The ''Palaeoamasia'' sp. nov. fossil is the youngest found to date, extending the period of survival of the genus to the early Oligocene. The fossils recorded consist mostly of tooth and jaw fragments. The tooth fossils show that ''Palaeoamasia'' has two prominent transverse crests on upper molars, signifying the embrithopod synapomorphy of bilophodont upper molars.

Distribution

Embrithopods are a group of early

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

mammals with evolutionary roots in

Northern Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in t ...

, eventually traveling over the Neotethys Sea to the Eurasian Eocene island of

Pontides The Pontic Mountains or Pontic Alps ( Turkish: ''Kuzey Anadolu Dağları'', meaning North Anatolian Mountains) form a mountain range in northern Anatolia, Turkey. They are also known as the ''Parhar Mountains'' in the local Turkish and Pontic G ...

. The method in which embrithopods reached the Orhaniye Basin is unclear. One thing is certain, in that

vicariance Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

is out of the question. The Orhaniye Basin is located on what was an Eocene island called Pontides. Pontides was located just north of the Neotethys sea and south of the

Paratethys Sea The Paratethys sea, Paratethys ocean, Paratethys realm or just Paratethys was a large shallow inland sea that stretched from the region north of the Alps over Central Europe to the Aral Sea in Central Asia. Paratethys was peculiar due to its pal ...

. Pontides, which is part of Eurasia, separated into its own land mass before the Paleocene-Eocene boundary. Embrithopods did not appear on Pontides until 43 Ma, which is after the breakup of the island. Part of the reason the embrithopods living in the Orhaniye Basin are thought to have been living on an island is the odd nature of the associated mammalian fauna, which includes anachronistic taxa such as ''pleuraspidotheriid condylarths'', but lacks the (otherwise ubiquitous) rodents, perissodactyls, and artiodactyls. If vicariance did take place, all fossils would be found in both locations. This leaves only two other methods of dispersal. Embrithopods could have “island hopped” from Africa to Pontides. Another theory is that embrithopods rode a land raft that happened upon Pontides. Currently, only Palaeoamasia and Hypsamasia, both Palaeoamasiidae, have been found in Turkey. A recent stable isotope study concluded that ''

Arsinoitherium ''Arsinoitherium'' is an extinct genus of paenungulate mammals belonging to the extinct Order (biology), order Embrithopoda. It is related to elephants, sirenians, hyraxes and the extinct desmostylians. Arsinoitheres were superficially rhinoceros ...

'', an African embrithopod, was terrestrial, not semi-aquatic as originally believed. Radiating from the same ancestral node, it is likely that ''Palaeoamasia'' was also terrestrial. Thus, it is likely that embrithopods did not swim across the Neotethys sea.

Description

Little information is available on the physiology of ''Palaeoamasia''. Sister taxa ''

'', on the other hand, is very well documented. The build of ''Arsinoitherium'' is consistent with aquatic mammals, even though it is a terrestrial mammal. The vertebrate of ''Arsinoitherium'' suggest that the head was raised above the shoulders, allowing the mammal to hold its head above water while swimming. However, the sacral vertebrae were no fused, making it harder to hold up its large body. Additionally, ''Arsinoitherium'' has short legs with a low knee joint, reducing the mammal to a short stride, which tends to make it more difficult to walk. Finally, ''Arsinoitherium'' is recorded to be

plantigrade 151px, Portion of a human skeleton, showing plantigrade habit In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. T ...

. ''Palaeoamasia'' has highly unique hyperdilambdodont molars, indicative of a plant-only diet. This derived feature of having two prominent transverse crests on upper molars is only found in embrithopods.

References

{{Taxonbar, from=Q7126387 Embrithopods Ypresian life Prehistoric placental genera Eocene mammals of Asia Fossils of Turkey Fossil taxa described in 1966