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Sculptures by Phyllis Bone


EXTINCT UNGULATES

There are 5 orders of ungulates which are now extinct:

ORDER CONDYLARTHRA.

The early ungulates of the Palæocene and Eocene epochs have for a long time been grouped together in the Order Condylarthra. This consists of several families at least two of which are known to have given rise to modern orders of ungulates. Protungulatum, the first ungulate, was a condylarth.

Taken as a whole the condylarths were a widespread group. Condylarths were found throughout Eurasia, North America, South America and Africa. Ungulates also reached Antarctica, which had a temperate climate in the early Tertiary. Most incredibly, a recent find of dental material in early Eocene rocks of Queensland, Australia suggests that condylarth placental mammals were present at this time.Tingamurra is known only from a single tooth, but analysis of its structure and enamel ultrastructure place it with the condylarths.


ORDER EMBRITHOPODA.

For a long time this order contained the solitary species Arsinoitherium . This early Oligocene African horned creature is fascinating for numerous reasons - its apparent isolation in the fossil record and its convergence with the rhinoceroses and brontotheres on other continents. Other arsinoitheres are now known from Asia Minor and the Balkans.

The Embrithopoda is now considered the 'stem group' of the Proboscidea, that is to say the ancesors of the proboscids were embrithopods.


ORDER DESMOSTYLIA.

The desmostylians are one of the most bizarre ungulate groups. Skulls were discovered in marine sediments long before the skeletons, leading to the conclusion that desmostylians were aberrant sirenians.The tusks on both jaws were reminiscent of early proboscids, while the teeth were apparently replaced from the back of the jaw as in sirenians and proboscids. When skeletons were found it became obvious that desmostylians were very different from the sea cows - they were short-tailed and had fully-formed, robust hind and fore-limbs.They could perhaps best be described as small-headed, buck-toothed hippopotamuses. It has been suggested that they may have 'poled' their way along the substrate at high tide, much in the manner of a hippopotamus 'walking' along the bottom of a river. They probably ate seaweed, or perhaps shellfish. Recent finds in North America suggest that desmostylians may be closer to the Proboscidea than the Sirenia.

All but one of the desmostylians are from the Pacific coasts of Asia and North America, where they persisted to the late Pliocene. A single fossil from Florida helps to connect them to a likely origin by the shores of the ancient Tethys Sea.


ORDER NOTOUNGULATA AND ORDER LITOPTERNA.

Two orders of ungulates confined entirely to South America, where they evolved in isolation from other ungulates for nearly 60 million years, until the Panamanian landbridge formed 2.5 million years ago.

The notoungulates included a variety of forms, some of which looked like rhinoceroses, others like rodents and lagomorphs, others like the peculiar perissoadactyl chalicotheres and some had skulls like horses.

The litopterns were even more unusual. Some were very like camels, including a bizarre creature with a proboscis called Macrauchenia, described as "a cross between a camel and a tapir".

Perhaps the most amazing of the South American ungulates were the litopterns of the Family Prototheriidae. These were very horse-like indeed, and evolved singl-toed limbs 20 million years before they appeared in horses.