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Arsinoitherium zetteli cast on display at the British Museum of Natural History

Arsinoitherium zetteli cast on display at the British Museum of Natural History.

Fast Facts

Reproduction of a painting of an Arsinoitherium by Heinrich Harder (United States Public Domain)

Name: Arsinoitherium (pronunciation: "Arsin-oy-ther-ium")
The name means "Arsinoe's Beast"

Taxonomy: Mammalia (Mammal Class) - Paenungulata (Superorder) - Embrithopoda (Order) - Arsinoitheriidae (Family) - Arsinoitherium (Genus) - A. zitteli, A. giganteum (species)

Age: Late Eocene - Early Oligocene (35 – 27 myo).

Extinction: Early Oligocene

Discovery: Beadnell, 1902
H. L. Beadnell discovered fossils of this animal in the Fayum Depression of Egypt in 1901.

Distribution: Northern Africa

Body Size: Rhinoceros Sized
E. zitteli was nearly 6 feet tall and 11 feet long, about the same size as a White Rhino. E. giganteum was about 25% larger.

Diet: Herbivore: Vegetation

Fun Facts:
Although it looks like a Rhinoceros, it's closely related to the Elephant.

The giant double horns are hollow and made of bone that probably had a keratin sheath (like a cows horns).

Arsinoitherium is named after Queen Arsinoe I of Ancient Egypt.
The Faiyum Oasis, where the first fossils were found, use to be named after Queen Arsinoe I.

Species and Distribution

Arsinoitherium lived in Africa and Saudi Arabia from the Middle Eocene into the Early Oligocene (45 – 24 myo). There are 3 species: A. zitteli, A. giganteus, and N. blackcrowense.

A. zitteli, the original species, is only found in the Jebel Qatrani Formation in Fayum, Egypt. This is also the only location where nearly complete specimens have been recovered (Site F on map below).
An additional species, A. andrewsi, is probably synonymous with A. zitteli. Fossils of A. andrewsi are most likely large A. zitteli specimens (Werdelin and Sanders, 2010).

A. giganteus is a newer large species discovered in 2004 in the Chilga region of Ethiopia (Site C on map below) (Sanders et al, 2004). Tooth size comparisons indicate it was approximately 25% larger than A. zitteli, which would be slightly larger than a large White Rhino.

Another Arsinoitheriid is Namatherium blackcrowense from the Middle Eocene of Namibia. This animal is smaller than the other Arsinoitheriums and is the earliest occurence of these animals.

There have also been fragments (mainly teeth) of the genus (uncertain species) found in various African and Middle Eastern countries, including the Late Eocene of Libya and Tunisia, and the Early Oligocene of Angola, Oman, Saudi Arabia, and Kenya. These additional sites (minus the Middle East sites) can be seen on the map below. The Eragaleitt beds (27.5 - 24 myo) in Kenya are the last occurrence of Arsinoitherium

There are also closely related animals that belong to the same Arsinoitheriidae family, such as Crivadiatherium and Palaeoamasia that are found in Romania, Turkey, the Middle East, Asia, and Africa.

Figure 1A from Sanders et al., 2004 showing a map
of Afro-Arabia with important Paleogene terrestrial mammal sites

This is Figure 1A from Sanders et al., 2004 - "Map of Afro−Arabia with several important Paleogene terrestrial mammal sites (underlined characters denote abbreviations for the localities marked on the map), including Chilga (Ethiopia), Dogali (Eritrea), Lothidok (Eragaleit Beds, Kenya), Fayum (Egypt), Dor el Talha (Libya), Malembe (Angola), Mahenge (Tanzania), and Thaytini and Taqah (Oman)."

Description and Paleoecology

Arsinoitherium zitteli skeletal reconstruction from Andrews 1906 publication

Arsinoitherium zitteli skeletal reconstruction from Andrews 1906 publication


At approximately 6 feet tall and 11 feet long, Arsinoitherium zitteli is a similar in size and shape to the White Rhinoceros. With its giant twin horns, it looks like a fanciful version of a rhino, however, it is not closely related to rhinos at all. Instead, it’s a genus of paenungulate mammals, which include Elephants, Sirena (dugongs and manatees), hyraxes, and the extinct Desmostylians.

Arsinoitherium’s bone structure is very different than a rhino’s. Examples include its columnar legs, which are distinctly elephant-like, plus its elephant-like hips, feet, and skull features.

The horns are also very different from a rhinoceros. These twin horns could grow to over 2.5 feet in length. The animal aslo had a much smaller pair of horns above the eyes. Rhino horns are completely made of keratin, where Arsinoitherium horns are hollow and made of bone. Witton briefly looked at the structure of the horns and compared them to modern animals. They most closely resemble bovid (cow) horns and probably had a keratin sheath over them like a cow (Witton 2017). Witton also says the keratin would have strengthened the horns, as the hollow horns would have been fragile and prone to fracturing.


Formations Arsinoitherium have been found in indicate tropical forests and edges of mangrove swamps.

A common misconception is that Arsinoitherium spent much of its time in water, like a hippopotamus, feeding on aquatic vegetation. This misconception arises because Arsenoitherium was poorly designed for running. However, research has shown it was fully terrestrial. Other fossils found with Arsinoitherium support a fully terrestrial environment. Also a stable isotope analysis was done on Arsinoitherium fossil which indicate it was a terrestrial feeder (Clementz et al., 2008). It may have been poorly designed for running because it didn’t need to run, as it was one of the largest mammals in Africa in its time!

Arsenoitherium also has a specialized tooth design and specific attachment points for muscles in its jaws which indicate a very specialized diet. Court, 1992b suggested it may have ate bulky fruits. This type of food is also abundant at the Fayum site in Egypt where A. zitteli is found.

Sketch of Arsinoitherium zitteli from Egypt.

Sketch of Arsinoitherium zitteli from Egypt. Photo by Dmitry Bogdanov (CC-3.0)


The first Arsinoitherium fossils were found in the Fayum (Faiyum/Fayoum) area of Egypt from the Jebel Qatrani formation by H. L. Beadnel in 1901.

In 1902 he published his findings and named the specimen Arsinoitherium zitteli. The genus name comes from Queen Arsinoe I of Egypt, whose husband Ptolemy II named the Fayum region after her. The name means Arsinoe’s Beast. The species is named in honor of the Paleontologist Karl Alfred Ritter von Zittel who was a pioneer in Egyptian Paleontology.

Arsinoitherium fossils were studied in much greater detail by Andrews in 1906. His publication "A descriptive catalogue of the Tertiary Vertebrata of the Fayûm, Egypt" is still a great resource with wonderful fossil illustrations. The book is available online here.

Dekadrachm of Ptolemy III for Arsinoe I (245 BC)

Dekadrachm of Ptolemy III for Arsinoe I (245 BC); Kestner museum, Hannover by Einsamer Schutze (CC-by-3.0)

Additional Images

Arsinoitherium zitteli cast on display at the British Museum of Natural History in London

Arsinoitherium zitteli cast on display at the British Museum of Natural History in London

These are additional specimens from the digitized collection of the British Museum - Image Credit: The Trustees of the Natural History Museum, London (CC-by-4.0). Tap a thumbnail for the full image and specimen number.

Recommended Books

Beadnell 1902 Historic Book
by Beadnell, 1902

This historic book "A Preliminary Note On Arsinoitherium Zitteli, Beadn: From The Upper Eocene Strata Of Egypt" contains historic plates of the first Arsinoitherium fossils, including skulls. It's a really interesting book for anyone into Historical Paleontology!

Cenozoic Mammals of Africa
Editors: Werdelin and Sanders, 2008

This reviews the mammal fossil record from Africa over the past 65 million years (including the Arsinoitherium species with fossil images). Included is detailed information about the fossil sites, the mammals, paleoecology, biogeography, and much more. It's great for anyone wanting to study the fossil record of mammals. There were lots of strange mammals in Africa!

Works Cited:

Clementz M. T., Holroyd P. A., and Koch P. L. (2008) Identifying aquatic habits of herbivorous mammalsthrough stable isotope analysis. Palaios,23, 574–585.

Court N. (1990) Periotic Anatomy of Arsinoitherium (Mammalia, Embrithopoda) and Its Phylogenetic Implications. Journal of Vertebrate Paleontology, 10(2), 170-182. Retrieved from www.jstor.org/stable/4523315

Court N. (1992b) A unique form of dental bilophodonty and a func-tional interpretation of peculiarities in the masticatory systemof Arsinoitherium (Mammalia, Embrithopoda). HistoricalBiology,6,91–111

Sanders W., Kappelman J., and Rasmussen D. T. (2004) New large−bodied mammals from the late Oligocene site of Chilga, Ethiopia. Acta Palaeontologica Polonica 49(3):365-392. Link to Paper

Witton, M. (2017, September 24) The horns of Arsinoitherium: covered in skin or augmented with keratin sheaths? Retrieved from markwitton.com - blog.

Bennett S.C. (2003) New crested specimens of the Late Cretaceous pterosaur Nyctosaurus. Paläontologische Zeitschrift, 77: 61-75.

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