Rhinoceros - Evolution

Evolution

Rhinocerotoids diverged from other perissodactyls by the early Eocene. Fossils of Hyrachyus eximus found in North America date to this period. This small hornless ancestor resembled a tapir or small horse more than a rhino. Three families, sometimes grouped together as the superfamily Rhinocerotoidea, evolved in the late Eocene: Hyracodontidae, Amynodontidae and Rhinocerotidae.

Hyracodontidae, also known as 'running rhinos', showed adaptations for speed, and would have looked more like horses than modern rhinos. The smallest hyracodontids were dog-sized; the largest was Indricotherium, believed to be one of the largest land mammals that ever existed. The hornless Indricotherium was almost seven metres high, ten metres long, and weighed as much as 15 tons. Like a giraffe, it ate leaves from trees. The hyracodontids spread across Eurasia from the mid-Eocene to early Miocene.

The Amynodontidae, also known as "aquatic rhinos", dispersed across North America and Eurasia, from the late Eocene to early Oligocene. The amynodontids were hippopotamus-like in their ecology and appearance, inhabiting rivers and lakes, and sharing many of the same adaptations to aquatic life as hippos.

The family of all modern rhinoceros, the Rhinocerotidae, first appeared in the Late Eocene in Eurasia. The earliest members of Rhinocerotidae were small and numerous; at least 26 genera lived in Eurasia and North America until a wave of extinctions in the middle Oligocene wiped out most of the smaller species. However, several independent lineages survived. Menoceras, a pig-sized rhinoceros, had two horns side-by-side. The North American Teleoceras had short legs, a barrel chest and lived until about 5 million years ago. The last rhinos in the Americas became extinct during the Pliocene.

Modern rhinos are believed to have began dispersal from Asia during the Miocene. Two species survived the most recent period of glaciation and inhabited Europe as recently as 10,000 years ago: the woolly rhinoceros and Elasmotherium. The woolly rhinoceros appeared in China around 1 million years ago and first arrived in Europe around 600,000 years ago. It reappeared 200,000 years ago, alongside the woolly mammoth, and became numerous. Eventually it was hunted to extinction by early humans. Elasmotherium, also known as the giant rhinoceros, survived through the middle Pleistocene: it was two meters tall, five meters long and weighed around five tons, with a single enormous horn, hypsodont teeth and long legs for running.

Of the extant rhinoceros species, the Sumatran rhino is the most archaic, first emerging more than 15 million years ago. The Sumatran rhino was closely related to the woolly rhinoceros, but not to the other modern species. The Indian rhino and Javan rhino are closely related and form a more recent lineage of Asian rhino. The ancestors of early Indian and Javan rhino diverged 2–4 million years ago.

The origin of the two living African rhinos can be traced back to the late Miocene (6 mya) species Ceratotherium neumayri. The lineages containing the living species diverged by the early Pliocene (1.5 mya), when Diceros praecox, the likely ancestor of the black rhinoceros, appears in the fossil record. The black and white rhinoceros remain so closely related that they can still mate and successfully produce offspring.

• Family Rhinocerotidae
  • Subfamily Rhinocerotinae
    • Tribe Aceratheriini
      • †Aceratherium lived from 33.9—3.4 Ma
      • †Acerorhinus 13.6—7.0 Ma
      • †Alicornops 13.7—5.33 Ma
      • †Aphelops 20.430—5.330 Ma
      • †Chilotheridium 23.03—11.610 Ma
      • †Chilotherium 13.7—3.4 Ma
      • †Dromoceratherium 15.97—7.25 Ma
      • †Floridaceras 20.43—16.3 Ma
      • †Hoploaceratherium 16.9—16.0 Ma
      • †Mesaceratherium
      • †Peraceras 20.6—10.3 Ma
      • †Plesiaceratherium 20.0—11.6 Ma
      • †Proaceratherium 16.9—16.0 Ma
      • †Sinorhinus
      • †Subchilotherium
    • Tribe Teleoceratini
      • †Aprotodon 28.4—5.330 Ma
      • †Brachydiceratherium
      • †Brachypodella
      • †Brachypotherium 20.0—5.33 Ma
      • †Diaceratherium 28.4—16.0 Ma
      • †Prosantorhinus 16.9—7.25 Ma
      • †Shennongtherium
      • †Teleoceras 16.9—4.9 Ma
    • Tribe Rhinocerotini 40.4—11.1 Ma—Present
      • †Gaindatherium 11.61—11.1 Ma
      • Subtribe Rhinocerotina 17.5 Ma—Present
        • †Rusingaceros 17.5 Ma
        • Rhinoceros – Indian & Javan rhinoceros
    • Tribe Dicerorhinini
      • †Coelodonta – Woolly rhinoceros
      • Dicerorhinus – Sumatran rhinoceros
      • †Dihoplus 11.610—1.810 Ma
      • †Lartetotherium 15.97—8.7 Ma
      • †Stephanorhinus 9.7—0.126 Ma – Merck´s rhinoceros & Narrow-nosed rhinoceros
    • Tribe Dicerotini 23.03—Present
      • Ceratotherium – White rhinoceros 7.250—Present
      • Diceros – Black rhinoceros 23.03—Present
      • †Paradiceros 15.97—11.61 Ma
  • Subfamily Elasmotheriinae
    • †Gulfoceras 23.030—20.430 Ma
      • †Victoriaceros 15 Ma
    • Tribe Diceratheriini
      • †Diceratherium 33.9—11.610 Ma
      • †Subhyracodon 38.0—26.3 Ma
    • Tribe Elasmotheriini 20.0—0.126 Ma
      • †Bugtirhinus 20.0—16.9 Ma
      • †Caementodon
      • †Elasmotherium – Giant rhinoceros 3.6—0.126 Ma
      • †Hispanotherium synonymized with Huaqingtherium 16.0—7.250 Ma
      • †Iranotherium
      • †Kenyatherium
      • †Meninatherium
      • †Menoceras 23.03—16.3 Ma
      • †Ougandatherium 20.0—16.9 Ma
      • †Parelasmotherium
      • †Procoelodonta
      • †Sinotherium 9.0—5.3 Ma