''Aphonopelma marxi'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

in the family Theraphosidae (

tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...

s), found in United States (Arizona, New Mexico, Colorado and Utah). ''Aphonopelma behlei'' and ''A. vogelae'', at one time considered separate species, are now considered to be synonyms.

Description

''Aphonopelma marxi'' is generally dark brown to black in color, very hairy, with some orange to red hairs on the abdomen. The mature male's carapace ranges from long, the mature female being larger, with a carapace from long. The total body length of a female, including the

chelicerae The chelicerae () are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as " jaws", chelicerae may be shaped as either articulated fangs, or similarl ...

, is around . ''A. marxi'' can be distinguished from other species of the genus living in the same places by its dark color, overall hairy appearance, size and habitat. In males, the ratio of the length of the femur of the first leg to the length of the metatarsus of the same leg is greater than 1.69, whereas in similar species the ratio is smaller. In females, the ratio of the length of the femur of the first leg to the length of metatarsus of the third leg is greater than 1.76, being smaller in similar species.

Taxonomy

The species was first described by Eugène Simon in 1891 as ''Eurypelma marxi''. The original

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...

on which the species was described has been lost; in 1997, T. R. Prentice designated a

neotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

. Placement in the genus ''

Aphonopelma ''Aphonopelma'' is a genus of tarantulas native to the Americas. It includes nearly all the North American tarantula species north of Mexico and a considerable percentage of the tarantula species that range into Central America. Most are fairly ...

'' was first made by Andrew M. Smith in 1995. Smith also recognized two species, ''A. behlei'' and ''A. vogelae'', that in analyses performed by Hamilton et al. in 2016 were not distinguished from ''A. marxi'' on either morphological or molecular grounds, and so were treated as junior synonyms. ''Aphonopelma marxi'' belongs to the "Marxi species group" – a group of mainly black species, often found in high-elevation habitats. Other species of the group include '' A. catalina'', '' A. chiricahua'', '' A. madera'', '' A. peloncillo'' and '' A. vorhiesi''.

Distribution and habitat

''Aphonopelma marxi'' is widely distributed in areas of higher elevation in the "Four Corners" region of northern Arizona, northwestern New Mexico, southwestern Colorado, and southeastern Utah. It is found in a variety of habitats, including mixed conifer forests and sagebrush steppe. The species is described as "very common" in these areas, but is difficult to find as it normally remains in its hidden burrow. The burrows of all the Marxi species group have been described as "incredibly difficult to find".

References

{{Taxonbar, from=Q1997335 marxi Spiders of the United States Spiders of Central America Spiders described in 1891