Members of the genus had a long spinal column with short limbs and tail, making them one of the few genera of Paleogene mammal with a common name: "tube-sheep" Reconstructing their appearance in life was originally difficult, as remains are common but often consist only of fragmentary jaws or skulls and teeth. (In
H. paulus, this preservation has been observed in predator coprolites, along with lizard scutes.) However, several whole individuals in the genus have been found beautifully preserved in life positions in
langerstatten in fossil lakes. They show
Hyopsodus individuals had an arched back with a posture similar to a
hyrax, rather than a weasel-like tube-shaped body. Study of the limbs in
H. lepidus has shown these animals were not adapted either for life as underground diggers like
moles and
groundhogs, or for life in the trees. However, they would have moved quickly on the ground, and could have dug for food or shelter as
pigs and
bandicoots do. An endocast of the brain of
H. lepidus has shown it had an excellent sense of smell and an expanded ability to process sounds. Though they did not have a sophisticated echolocation system like
bats, they may have had basic terrestrial
echolocation to help them avoid or find objects in the dark, like modern
shrews and
tenrecs. It is likely
H. lepidus was a nocturnal ground-dweller in damp closed forests and by the edges of lakes.
H. wortmani had strong chest muscles and could have dug burrows or swum. The teeth of all species show they were
omnivores; at least one species,
H. lovei, had a battery of procumbent incisors worn by chewing, and likely had a specialized diet. In their heyday,
Hyopsodus species may have occupied a variety of niches later taken by other flexible forest feeders such as
rats, small early
perissodactyls, and
hypocarnivores like
raccoons. ==References ==