Parahippus

Name: Parahippus ‭(‬Near horse‭)‬.
Phonetic: Pah-rah-hip-pus.
Named By: Joseph Leidy‭ ‬-‭ ‬1858.
Synonyms: Hippodon barbouri,‭ ‬Hippodon vellicans,‭ ‬Merychippus socius,‭ ‬Merychippus vellicans,‭ ‬Nannippus niobrarensis,‭ ‬Neohipparion niobrarense,‭ ‬Parahippus barbouri,‭ ‬Parahippus vellicans,‭ ‬Protohippus niobrariensis.
Classification: Chordata,‭ ‬Mammalia,‭ ‬Perissodactyla,‭ ‬Equidae,‭ ‬Anchitheriinae.
Species: P.‭ ‬cognatus‭ (‬type‭?)‬,‭ ‬P.‭ ‬agrestis,‭ ‬P.‭ ‬atavus,‭ ‬P.‭ ‬coloradensis,‭ ‬P.‭ ‬leonensis,‭ ‬P.‭ ‬maxsoni,‭ ‬P.‭ ‬nebrascensis,‭ ‬P.‭ ‬pawniensis,‭ ‬P.‭ ‬pristinus,‭ ‬P.‭ ‬tyleri,‭ ‬P.‭ ‬wyomingensis.
Diet: Herbivore.
Size: About‭ ‬1‭ ‬meter tall at the shoulder‭ (‬withers‭)‬.
Known locations: Across the USA.‭ ‬Canada,‭ ‬Saskatchewan.
Time period: Rupelian of the Oligocene to possibly the Messinian of the Miocene.
Fossil representation: Multiple individuals.

       The Oligocene and Miocene periods were times of change for the world‭’‬s ecosystems,‭ ‬particularly those of the northern‭ ‬hemisphere.‭ ‬Long covered by temperate and in places tropical forests,‭ ‬these were now steadily being replaced by grassy plains.‭ ‬Parahippus is a horse that shows a shift towards coping with these changing environments.
       Primitive horse forms still had toes like many other kinds of mammals,‭ ‬but in time most of these toes became reduced until a single hoof was left,‭ ‬just like in modern horses.‭ ‬Parahippus still had three visible toes to the lower foot,‭ ‬but only one was in contact with the ground.‭ ‬The other two remaining toes that were still visible were now vestigial,‭ ‬which means that they were still there,‭ ‬just no longer serving a practical purpose.‭ ‬The legs in general had also changed with enhanced musculature that limited side to side movement while increasing forward stride strength.‭ ‬This is a clear adaptation towards living on an open plains environment where fast locomotion would not‭ ‬only be possible,‭ ‬but also preferable to escape from predators that were also becoming faster runners.
       Earlier and shorter snouted horses were better adapted for browsing foliage,‭ ‬though changing ecosystems meant a continuing reduction in the amounts of available plants.‭ ‬The head of Parahippus was also proportionately longer than earlier forms so that it could more easily reach lower down to graze upon grass,‭ ‬a plant type that was becoming increasingly common.‭ ‬Grazing grass means that the teeth have to do more grinding and the teeth of Parahippus also had higher tooth crowns to cope with‭ ‬this increase in grinding.‭ ‬These‭ ‬were not new features exclusive to Parahippus as the earlier genus Miohippus also had higher tooth crowns.‭ ‬However the size of the tooth crown increase was more uniform and consistent across all of the teeth of Parahippus,‭ ‬meaning that while the adaptation was essentially the same,‭ ‬it had still managed to become more stabilised.‭ ‬This is a good study for evolution in action since not only can a change be seen to have taken place,‭ ‬it can also be seen to become refined.






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