Anthracotheriidae
Extinct hippopotamus-like ungulates possibly ancestral to hippos and whales.
Wikipedia / Wikimedia Commons
Anthracotheriidae is a paraphyletic group of extinct artiodactyls that resembled hippopotamuses and are linked to both hippos and whales. The group gets its name from the first genus identified, *Anthracotherium*, which translates to "coal beast" because its earliest fossils turned up in Paleogene coal deposits in France. These animals were widespread across Africa and Eurasia, and a few species managed to reach North America during the Oligocene. They disappeared from Europe and Africa in the Miocene, likely due to shifting climates and competition from other artiodactyls like pigs and hippos. The last genus, *Merycopotamus*, held on in Asia until the late Pliocene, probably for similar reasons. The oldest known genus, *Elomeryx*, first appeared in the middle Eocene of Asia.
In life, a typical anthracothere would have looked like a skinny hippo with a small, narrow head and a generally pig-like build. Each foot had four or five toes, and the broad feet were well suited for walking on soft mud. They had a full set of about 44 teeth, with five semicrescent cusps on the upper molars; in some species, these teeth were adapted for digging up the roots of aquatic plants.
Some skeletal features suggest anthracotheres are related to hippos. The types of sediments where they are fossilized indicate they were amphibious, supporting the idea—based on anatomy—that they were ancestors of hippopotamuses. In many ways, especially the lower jaw, *Anthracotherium* and other members of the family resemble hippos and are probably ancestral to them. However, one study argues that palaeochoerids, another pig-like artiodactyl group, are the true stem group of Hippopotamidae.
Recent comparative gene sequencing suggests hippos are the closest living relatives of whales, so if anthracotheres are stem hippos, they would also be related to whales in a clade provisionally called Whippomorpha. But the earliest anthracotheres appear in the middle Eocene, well after archaeocetes had already become fully aquatic. While molecular data on living animals strongly supports a close hippo-cetacean link, the two groups are unlikely to be closely related when both extinct and extant artiodactyls are analyzed. Cetaceans originated about 50 million years ago in the Tethys Sea, whereas the family Hippopotamidae is only 15 million years old, and the first Asian hippos are just 6 million years old.
- time_range
- Middle Eocene to late Pliocene
- first_appearance
- Middle Eocene in Asia
- last_appearance
- Late Pliocene in Asia (genus Merycopotamus)
- distribution
- Africa, Eurasia, and North America (Oligocene)
- known_for
- Possible ancestors of hippopotamuses and relatives of whales
- type_genus
- Anthracotherium ('coal beast')
Lore & Background
In life, the average anthracothere resembled a skinny hippopotamus with a comparatively small, narrow head and most likely pig-like in general appearance. They had four or five toes on each foot and broad feet suited to walking on soft mud. They had full sets of about 44 teeth with five semicrescentric cusps on the upper molars, which, in some species, were adapted for digging up the roots of aquatic plants.
Fossil remains of the anthracothere genus were discovered by the Harvard University and Geological Survey of Pakistan joint research project (Y-GSP) in the well-dated middle and late Miocene deposits of the Pothohar Plateau in northern Pakistan. The nature of the sediments in which they are fossilized implies they were amphibious, supporting the view that they were ancestors of the hippopotamuses.
Reader's Guide
Anthracotheriidae holds significance in the study of mammalian evolution due to its proposed relationship to both hippopotamuses and whales. Some skeletal characters suggest they are related to hippos, and anatomical evidence, especially of the lower jaw, allies them with the hippopotamus, of which they are probably an ancestral form. However, one study suggests that palaeochoerids, another pig-like group, are the true stem group of Hippopotamidae. Recent comparative gene sequencing indicates hippos are the closest living relatives of whales, so if anthracotheres are stem hippos, they would also be related to whales in a clade called Whippomorpha. Yet, the earliest known anthracotheres appear in the middle Eocene, well after archaeocetes had taken up aquatic lifestyles, and phylogenetic analyses of molecular data on extant animals strongly support the hippo-cetacean link, but the two groups are unlikely to be closely related when extinct artiodactyls are analyzed. Another study suggests anthracotheres are part of a clade that also includes entelodonts and even Andrewsarchus, with Siamotherium as the most basal member of Cetacodontamorpha. The family's fossil record thus provides key but contested evidence for the origins of hippos and whales.
Did You Know?
- The family name Anthracotheriidae comes from Anthracotherium, meaning 'coal beast', because its first fossils were found in Paleogene-aged coal beds in France.
- The youngest genus, Merycopotamus, died out in Asia during the late Pliocene.
- Anthracotheres had four or five toes on each foot and broad feet suited to walking on soft mud.
- Fossil remains were discovered by the Harvard University and Geological Survey of Pakistan joint research project in the Pothohar Plateau of northern Pakistan.
Frequently Asked Questions
What exactly is Anthracotheriidae?
Anthracotheriidae is a paraphyletic assemblage of extinct artiodactyls that looked a lot like modern hippos but predate them. They are considered close relatives of both hippopotamuses and whales, making them a key branch in the evolving story of even-toed ungulates.
Where does the name 'Anthracotheriidae' come from?
The family is named after its type genus, Anthracotherium, which literally means 'coal beast.' That nickname stuck because the very first specimens were pulled out of Paleogene-era coal seams in France.
When and where did anthracotheres live?
They first appeared in the Middle Eocene in Asia and persisted until the Late Pliocene, with the genus Merycopotamus holding out in Asia the longest. Their range stretched across Africa and Eurasia, and a handful of species even crossed into North America during the Oligocene.
How did the anthracotheres go extinct?
They vanished from Europe and Africa during the Miocene, most likely squeezed out by changing climates and rising competition from other artiodactyls such as pigs and early hippos. In Asia, a few lineages lingered into the Pliocene before finally disappearing as well.
Why do paleontologists care so much about Anthracotheriidae?
They sit at a critical evolutionary crossroads, showing the morphological bridge between land-dwelling ungulates and the semi-aquatic hippos and fully aquatic whales. Understanding their anatomy helps reconstruct how artiodactyls transitioned from terrestrial to aquatic lifestyles over tens of millions of years.
More in Extinct Cenozoic Mammals 1-24
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