Everything about The Desmostylia totally explained
The
Desmostylia (
Greek for "bonded pillars") are an
extinct order of
marine mammals which existed from the
Arikareean age of the late
Oligocene epoch (30.8 million years ago) to the
Tortonian age of the late
Miocene epoch (7.25 million years ago). Their dental and skeletal form suggests desmostylians were
amphibious herbivores dependent on
littoral habitats. Their name refers to their highly distinctive molars, in which each cusp was modified into hollow columns, so that a typical molar would have resembled a cluster of pipes, or in the case of worn molars, volcanoes.
Desmostylian
fossils are known from the northern
Pacific rim, from southern
Japan through
Russia, the
Aleutian Islands and the Pacific coast of
North America to the southern tip of
Baja California. Though the
type species Desmostylus hesperus was originally classified from a few teeth and
vertebrae as a
sirenian by
Marsh in 1888, doubts arose a decade later when more complete fossils were discovered in Japan. In 1898, American geologist
Henry Fairfield Osborn, working with Japanese paleontologists S. Yoshiwara and J. Iwasaki, suggested a
proboscidean origin based on skull and tusk similarities to early
mastodons. One of the most comprehensive collections of desmostylian teeth was amassed by paleontologist
John C. Merriam, who concluded based on the
molar structure and repeated occurrence in marine beds that the animals had been aquatic, and were probably sirenian. Other scientists suggested origins with
monotremes like the
duck-billed platypus. Because desmostylians were originally known only from skull fragments, teeth and bits of other bones, general agreement was that they'd had flippers and a fin-like tail. The discovery of a complete skeleton from
Sakhalin Island in 1941, however, showed that they possessed four legs, with bones as stout as a
hippopotamus's, and justified the creation of a new order for the desmostylians, described by
Roy H. Reinhart in 1953.
Despite their similarities to manatees and elephants, desmostylians were entirely unlike any living creatures.
Douglas Emlong's 1971 discovery of the new genus
Behemotops from
Oregon showed that early desmostylians had more proboscidean-like teeth and jaws than later ones. Despite this discovery, their relationships to manatees and
ungulates remain unresolved.
Desmostylians grew to 1.8
metres in length and are thought to have weighed more than 200
kg.
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