''Arsinoitherium'' is an extinct genus of paenungulate

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 ...

s belonging to the extinct

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Embrithopoda Embrithopoda ("heavy-footed") is an Order (biology), order of extinct mammals known from Asia, Africa and Eastern Europe. Most of the embrithopod genera are known exclusively from jaws and teeth dated from the late Paleocene to the late Eocene; ...

. It is related to

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 ...

sirenia 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 ...

ns, 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. Arsinoitheres were superficially

rhinoceros A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

-like

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

s that lived during the Late

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

and the Early

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

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

from 36 to 30 million years ago, in areas of

tropical rainforest Tropical rainforests are dense and warm rainforests with high rainfall typically found between 10° north and south of the Equator. They are a subset of the tropical forest biome that occurs roughly within the 28° latitudes (in the torrid zo ...

and at the margin of

mangrove swamp Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangrove trees cannot withs ...

s. A species described in 2004, ''A. giganteum'', lived in

Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...

about 27 million years ago.

Taxonomy

The best-known (and first-described) species is ''A. zitteli''. Another species, ''A. giganteum'', was discovered in the

n highlands of

Chilga Chilga (Amharic language, Amharic: ጭልጋ ''č̣ilgā'') also Chelga, Ch'ilga is a Districts of Ethiopia, woreda in Amhara Region, Ethiopia. It is named after its chief town Chilga (also known as Ayikel), an important stopping point on the hist ...

in 2003. The fossil teeth, far larger than those of ''A. zitteli'', date to around 28–27 million years ago. While the

Faiyum Oasis The Faiyum Oasis ( ''Wāḥat al-Fayyum'') is a depression or basin in the desert immediately west of the Nile river, 62 miles south of Cairo, Egypt. The extent of the basin area is estimated at between 1,270 km2 (490 mi2) and 1,700&nb ...

is the only site where complete skeletons of ''Arsinoitherium'' fossils were recovered, arsinoitheriids have been found in southeastern Europe, including ''

Crivadiatherium ''Crivadiatherium'' is an extinct genus of Palaeoamasiidae, which fossil remains—teeth and mandible fragments—have been discovered in the Crivadia site in the Hațeg depression, Romania. The age of the Crivadia site is not clear, but seem ...

'' from Romania, and '' Hypsamasia'' and '' Palaeoamasia'' from Turkey. The generic name ''Arsinoitherium'' comes from

Pharaoh Pharaoh (, ; Egyptian language, Egyptian: ''wikt:pr ꜥꜣ, pr ꜥꜣ''; Meroitic language, Meroitic: 𐦲𐦤𐦧, ; Biblical Hebrew: ''Parʿō'') was the title of the monarch of ancient Egypt from the First Dynasty of Egypt, First Dynasty ( ...

Arsinoe II Arsinoë II (, 316 BC – between 270 and 268 BC) was Queen consort of Thrace, Anatolia, and Macedonia by her first and second marriage, to king Lysimachus and king Ptolemy Keraunos respectively, and then Queen of the Ptolemaic Kingdom of Egy ...

(after whom the

, the region in which the first fossils were found, was called during the

Ptolemaic Kingdom The Ptolemaic Kingdom (; , ) or Ptolemaic Empire was an ancient Greek polity based in Ancient Egypt, Egypt during the Hellenistic period. It was founded in 305 BC by the Ancient Macedonians, Macedonian Greek general Ptolemy I Soter, a Diadochi, ...

), and the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

word θηρίον (''theríon''), meaning "beast". The

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

of the

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

, ''A. zitteli'', was given to it in honor of the eminent German paleontologist

Karl Alfred Ritter von Zittel Karl Alfred Ritter von Zittel (25 September 1839 – 5 January 1904) was a German palaeontologist best known for his ''Handbuch der Palaeontologie'' (1876–1880). Biography Karl Alfred von Zittel was born in Bahlingen in the Grand Duchy ...

, regarded by some as the pioneer of paleontology in Egypt.

Description

Adults of the species ''A. zitteli'' stood around tall at the shoulders and in length. It weighed 2.5 tons, only slightly smaller than the modern

white rhino The white rhinoceros, also known as the white rhino or square-lipped rhinoceros (''Ceratotherium simum''), is the largest extant species of rhinoceros and the most Sociality, social of all rhino species, characterized by its wide mouth adapted f ...

and due to the similar features and sizes. ''Arsinoitherium'' superficially resembles a species of rhinoceros, but it is not closely related to rhinos; instead, their closest extant relatives are elephants and manatees. They were massive, slow-moving animals with forelimbs adapted for pulling strongly backwards rather than swinging forward, a feature typical of animals that punt themselves through shallow water or walk on soft, sticky ground. Fossils are found in sediments deposited in coastal swamps and warm, humid, heavily vegetated lowland forests across what is now Africa and Arabia. The most noticeable features of ''Arsinoitherium'' were a pair of enormous horns above the nose and a second pair of tiny knob-like horns over the eyes. These were structurally similar to the horns of modern bovids. While reconstructions usually show them as similar to the

ossicone Ossicones are columnar or conical skin-covered bone structures on the heads of giraffes, male okapi, and some of their extinct relatives. Ossicones are distinguished from the superficially similar structures of Horn (anatomy), horns and antlers ...

s of

giraffe The giraffe is a large Fauna of Africa, African even-toed ungulate, hoofed mammal belonging to the genus ''Giraffa.'' It is the Largest mammals#Even-toed Ungulates (Artiodactyla), tallest living terrestrial animal and the largest ruminant on ...

s, in life each bony core may have been covered, like the horn cores of bovids, with a large horn of

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...

. Both males and females had horns. While some investigators have described a larger and a smaller species from the same site, others have identified the difference in body and tooth size as sexual dimorphism. The skeleton is robust and the limbs were columnar, similar to those of elephants; the hips were also elephant-like, and arsinotheres were not built to run. ''Arsinoitherium'' had a full complement of 44 teeth, which is the primitive state of placental mammalian dentition. However, the genus had a unique and highly specialized way of chewing, shifting the jaw joint to produce constant pressure along its continuous row of teeth; it has been reconstructed as a highly selective browser.

Distribution

Fossils of ''Arsinoitherium'' have been found in:''Arsinoitherium''
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org ;Eocene * Aydim Formation,

Oman Oman, officially the Sultanate of Oman, is a country located on the southeastern coast of the Arabian Peninsula in West Asia and the Middle East. It shares land borders with Saudi Arabia, the United Arab Emirates, and Yemen. Oman’s coastline ...

* Idam Unit Formation,

Libya Libya, officially the State of Libya, is a country in the Maghreb region of North Africa. It borders the Mediterranean Sea to the north, Egypt to Egypt–Libya border, the east, Sudan to Libya–Sudan border, the southeast, Chad to Chad–L ...

* Djebel Chambi,

Tunisia Tunisia, officially the Republic of Tunisia, is a country in the Maghreb region of North Africa. It is bordered by Algeria to the west and southwest, Libya to the southeast, and the Mediterranean Sea to the north and east. Tunisia also shares m ...

;Oligocene * Malembe,

Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...

Jebel Qatrani Formation The Jebel Qatrani Formation (also Gebel Qatrani, Gabal Qatrani or Djebel Qatrani) is a geologic formation located in the Faiyum Governorate of central Egypt. It is exposed between the Jebel Qatrani escarpment and the Qasr el Sagha escarpment, nor ...

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

* Chilga formation,

* Erageleit Formation,

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

* Ashawq Formation, Oman * Shumaysi Formation,

Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in West Asia. Located in the centre of the Middle East, it covers the bulk of the Arabian Peninsula and has a land area of about , making it the List of Asian countries ...

References

External links

New fossils from Ethiopia open a window on Africa's 'missing years'

Arsinoitherium fact file on ''BBC Science & Nature: Prehistoric Life''

Description of Arsinoitherium zitteli from upper Eocene strata in Egypt
* {{Taxonbar, from=Q131720 Embrithopods Prehistoric placental genera Priabonian genus first appearances Rupelian genus extinctions Eocene mammals of Africa Oligocene mammals of Africa Fossils of Angola Fossils of Egypt Fossils of Ethiopia Fossils of Kenya Fossils of Libya Fossils of Tunisia Eocene mammals of Asia Oligocene mammals of Asia Fossils of Oman Fossils of Saudi Arabia Fossil taxa described in 1902