''Miacis'' ("small point") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of placental mammals from clade Carnivoraformes, that lived in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

from the early to middle

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

.J. J. Flynn (1998.) "Early Cenozoic Carnivora ("Miacoidea")." In C. M. Janis, K. M. Scott, and L. L. Jacobs (''eds.''
"Evolution of Tertiary Mammals of North America. Volume 1: Terrestrial Carnivores, Ungulates, and Ungulatelike Mammals."
Cambridge University Press, Cambridge.

Description

''Miacis'' was five-clawed, about the size of a

weasel Weasels are mammals of the genus ''Mustela'' of the family Mustelidae. The genus ''Mustela'' includes the least weasels, polecats, stoats, ferrets, and European mink. Members of this genus are small, active predators, with long and slend ...

(~30 cm), and lived on the North American continent. It retained some primitive characteristics such as a low skull, a long slender body, a long tail, and short legs. ''Miacis'' retained 44 teeth, although some reductions in this number were apparently in progress and some of the teeth were reduced in size. Miacis cropped

The hind limbs were longer than the forelimbs, the

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

was dog-like in form and structure, and some specialized traits were present in the vertebrae. It had retractable claws, agile joints for climbing, and

binocular vision Binocular vision is seeing with two eyes. The Field_of_view, field of view that can be surveyed with two eyes is greater than with one eye. To the extent that the visual fields of the two eyes overlap, #Depth, binocular depth can be perceived. Th ...

. ''Miacis'' and related forms had brains that were relatively larger than those of the creodonts, and the larger brain size as compared with body size probably reflects an increase in intelligence. Like many other early carnivoramorphans, it was well suited for an arboreal climbing lifestyle with needle-sharp claws, limbs, and joints resembling modern carnivorans. ''Miacis'' was probably a very agile forest dweller that preyed upon smaller animals, such as small

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s, and

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s, and might also have eaten eggs and fruits.

Classification and phylogeny

Classification

History of taxonomy

Since

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...

first described the genus ''Miacis'' in 1872, at least twenty other species have been assigned to ''Miacis''. However, these species share few

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ...

other than

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

characteristics of miacids in general. This reflects the fact that ''Miacis'' has been treated as a wastebasket taxon and contains a diverse collection of species that belong to the stemgroup within the Carnivoraformes. Many of the species originally assigned to ''Miacis'' have since been assigned to other genera and, apart from the type species, ''Miacis parvivorus'', the remaining species are often referred to with ''Miacis'' in quotations (e.g. ''"Miacis" latidens''). The following table lists the former ''Miacis'' species in chronological order of their original description and notes the reassignments to other genera.

Phylogeny

The phylogenetic relationships of genus ''Miacis'' are shown in the following cladogram:

References