''Hapalodectes'' (literal translation 'soft biter'; from grc, ἁπαλός ('soft, tender') and ('biter')) is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

otter Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine, with diets based on fish and invertebrates. Lutrinae is a branch of the Mustelidae family, which also includes wea ...

-like mesonychids from the

Late Paleocene The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...

Early Eocene In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian i ...

, some 55million years ago. Although the first fossils were found in the Eocene strata of

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

, the genus originated in

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

, as the oldest species is ''H. dux'', which was found in Late Paleocene strata in the Naran Bulak Formation. The genus was once suggested to be related to the

Archaeoceti Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene (). Representing the earliest cetacean radiation, they include the initia ...

, such as '' Pakicetus'', due to numerous similarities between the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

and tooth anatomies of the two genera. Now, however, ''Hapalodectes'' and other mesonychians are thought to be related to basal artiodactyls, while the Archaeoceti are now determined to be descended from more

derived Derive may refer to: * Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguatio ...

artiodactyls, like '' Indohyus'', which are related to

hippopotamus The hippopotamus ( ; : hippopotamuses or hippopotami; ''Hippopotamus amphibius''), also called the hippo, common hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two extan ...

es and

anthracothere Anthracotheriidae is a paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, '' Elomeryx'', first appeared during the middle Eocene in Asia. They thrived in Africa and Eur ...

Species

*Genus ''Hapalodectes'' ** ''H. anthracinus'' Zhou et Gingerich, 1991 ** ''H. dux'' Lopatin, 1999 ** ''H. hetangensis'' Ting et Li, 1987 ** ''H. huanghaiensis'' Tong et Wang, 2006 ** ''H. leptognathus'' Osborn et Wortman, 1892 ** ''H. lopatini'' Solé et al., 2017 ** ''H. paleocenus'' Beard et al., 2010 ** ''H. serus'' Matthew et Granger, 1925

References

Mesonychids Paleocene mammals Eocene mammals Ypresian extinctions Paleogene mammals of Asia Prehistoric placental genera {{paleo-mammal-stub