Artiodactyla, from Greek ἄρτιος (ártios, “even”) and Greek δάκτυλος (dáktulos, “finger, toe”), means “even-toed”, in reference to the fact that these animals bear weight equally on two (an even number) of their five toes: the third and fourth, often in the form of a hoof. The other three toes are either present, absent, vestigial, or pointing posteriorly.

Common names of members

Pigs, peccaries, hippopotamuses, antelopes, deer, giraffes, camels, llamas, alpacas, sheeps, goats, cattle, whales, dolphins, and porpoises.

Distribution 

All oceans and continents (except Australia and some oceanic islands).

Size

Size varies considerably: the smallest members often reach a body length of only 45 centimeters and a weight of 1.5 kilograms. The largest can grow up to 26 m in length and weigh 130 metric tons.

Morphology

They are generally quadrupeds. Two major body types are known: Suinids and hippopotamuses are characterized by a stocky body, short legs, and a large head (as well as whales and dolphins, but these play a streamlined shape, and their forelimbs are flippers); camels and ruminants, though, have a more slender build and lanky legs. Their digits are reduced. All of them have 3rd and 4th digits remaining. Some also have reduced 2nd and 5th digits. Their toes are laterally symmetrical.

Ecology & Habitat

All terrestrial (grassland, forest, mountain, desert, etc.) and oceanic environments.

Diet

The terrestrial ones play herbivorous diets  (grasses, roots, fruits, leaves, etc), but the aquatic ones often play exclusively carnivorous diets (fish, krill, plankton, mollusks, seals, etc).

Reproduction 

Many of them live in social groups. The young live with their mother and the male may accompany them depending on species. In some species, the social group even includes the young of the previous year. Most of the males will defend their territories during the mating period. Males will also taste the urine of females to target the individuals which are ready for mating. Most of them only give birth to one young in a year. 

Total species known

551

Species in the collection

14

Species in Hong Kong

3

References

- Spaulding, M., O'Leary, M. A., Gatesy, J. (2009). Relationships of Cetacea (Artiodactyla) Among Mammals: Increased Taxon Sampling Alters Interpretations of Key Fossils and Character Evolution. PLOS ONE. https://doi.org/10.1371/journal.pone.0007062. 

Macdonald, D. W. (2006). The Encyclopedia of mammals. Oxford University Press. https://doi.org/10.1093/acref/9780199206087.001.0001.