| Mesonychidae | |
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| Harpagolestes immanisskull | |
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| Life reconstruction ofHarpagolestes macrocephalus | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | †Mesonychia |
| Family: | †Mesonychidae Cope 1880[1] |
| Genera | |
See text | |
Mesonychidae (meaning "middleclaws") is an extinctfamily of small to large-sizedomnivorous-carnivorousmammals. They wereendemic toNorth America andEurasia during theEarly Paleocene to theEarly Oligocene, and were the earliest group of large carnivorous mammals inAsia. Once considered asister-taxon toartiodactyls, recent evidence now suggests no close connection to any living mammal. Mesonychidtaxonomy has long been disputed and they have captured popular imagination as "wolves onhooves",animals that combine features of bothungulates andcarnivores.Skulls andteeth have similar features to earlywhales, and the family was long thought to be the ancestors ofcetaceans. Recentfossil discoveries have overturned thisidea; the consensus is that whales are highly derivedartiodactyls.[2] Some researchers now consider the family a sister group either to whales or to artiodactyls, close relatives rather than direct ancestors. Other studies defineMesonychia asbasal to all ungulates, occupying a position betweenPerissodactyla andFerae. In this case, the resemblances to early whales would be due toconvergent evolution among ungulate-likeherbivores that developed adaptations related to hunting or eating meat.[3]
The mesonychids were an unusual group ofcondylarths with a specialized dentition featuring tri-cuspid upper molars and high-crowned lower molars with shearing surfaces. They had large heads with relatively long necks. Over time, the family evolved foot and leg adaptations for faster running, and jaw adaptations for greater bite force. Like the Paleocene familyArctocyonidae, mesonychids were once viewed as primitivecarnivorans, and the diet of most genera probably included meat or fish. Various genera and species coexisted in some locations, as hunters and omnivores or scavengers.[4] In contrast to arctocyonids, the mesonychids had only four digits furnished with hooves supported by narrow fissured end phalanges.[5]
They first appeared in the EarlyPaleocene, undergoing numerous speciation events during the Paleocene, andEocene. Mesonychids fared very poorly at the close of the Eocene epoch, with only one genus,Mongolestes,[6] surviving into the EarlyOligocene epoch.
Mesonychids probably originated inAsia, where the most primitive mesonychid,Yantanglestes, is known from the early Paleocene. They were also most diverse in Asia where they occur in all major Paleocenefaunas. Since othercarnivores such as thecreodonts andCarnivora were either rare or absent in these animal communities, mesonychids most likely dominated the largepredatorniche in the Paleocene of Asia. Throughout the Paleocene and Eocene, several genera, includingDissacus,Pachyaena andMesonyx would radiate out from their ancestral home in Asia and into Europe and North America, where they would give rise to new mesonychid genera. These animals would have migrated to North America via theBering land bridge.
Mesonychidae was named by Cope (1880). Its type genus isMesonyx. It was assigned toCreodonta by Cope (1880); to Creodonta by Cope (1889); toCarnivora by Peterson (1919); to Mesonychia by Carroll (1988) and Zhou et al. (1995); and to Cete by Archibald (1998);[7] and to Mesonychia by Carroll (1988), Zhou et al. (1995), Geisler and McKenna (2007) and Spaulding et al. (2009).[8]
Family Mesonychidae
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| Triisodontidae |  | |
| Mesonychidae | ||
| Hapalodectidae | ||