The Spalacidae, or spalacids, are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s in the large and complex superfamily

Muroidea The Muroidea are a large Taxonomic rank, superfamily of rodents, including mice, rats, voles, hamsters, lemmings, Gerbillinae, gerbils, and many other relatives. Although the Muroidea originated in Eurasia, they occupy a vast variety of habitat ...

. They are native to eastern

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

, the

Horn of Africa The Horn of Africa (HoA), also known as the Somali Peninsula, is a large peninsula and geopolitical region in East Africa.Robert Stock, ''Africa South of the Sahara, Second Edition: A Geographical Interpretation'', (The Guilford Press; 2004), ...

, the

Middle East The Middle East (term originally coined in English language) is a geopolitical region encompassing the Arabian Peninsula, the Levant, Turkey, Egypt, Iran, and Iraq. The term came into widespread usage by the United Kingdom and western Eur ...

, and southeastern

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

. It includes the blind mole-rats, bamboo rats,

mole-rat Mole-rat or mole rat can refer to several groups of burrowing Old World rodents: * Bathyergidae, a family of about 20 hystricognath species in six genera from Africa also called blesmols. *'' Heterocephalus glaber'', the naked mole-rat. * Spalac ...

s, and zokors. This family represents the oldest split (excluding perhaps the Platacanthomyidae) in the muroid superfamily, and comprises animals adapted to a subterranean way of life. These rodents were thought to have evolved adaptations to living underground independently until recent phylogenetic studies demonstrated they form a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group. Members of the Spalacidae are often placed in the family

Muridae The Muridae, or murids, are either the largest or second-largest family of rodents and of mammals, containing approximately 870 species, including many species of mice, rats, and gerbils found naturally throughout Eurasia, Africa, and Australia. ...

along with all other members of the Muroidea.

Characteristics

Spalacids are

mouse A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus'' ...

- to rat-sized rodents, adapted to burrowing and living underground. They have short limbs, wedge-shaped skulls, strong neck muscles, large incisor teeth, and small eyes and

external ear The outer ear, external ear, or auris externa is the external part of the ear, which consists of the auricle (anatomy), auricle (also pinna) and the ear canal. It gathers sound energy and focuses it on the eardrum (tympanic membrane). Structur ...

s. In the zokors, which dig primarily with their feet, rather than their teeth, the front

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthro ...

s are also massively enlarged. These features are least extreme in the bamboo rats, which spend at least some of their time above ground, foraging for food. They are most highly developed in the blind mole-rats, whose eyes are completely covered by skin, and entirely lack external ears or tails. All of the spalacid species dig extensive burrows, which may include storage chambers for food, latrine chambers, and breeding nests. They are generally solitary animals, and do not share their tunnel complexes with other individuals. All the species are

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

s, feeding on

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

s, bulbs, and

tuber Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reproduc ...

s. They give birth to litters of up to six young after a

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...

period between three and seven weeks, depending on the species. As with many other muroids, the young are born blind, hairless, and helpless. They may stay with the mother for several months before setting off to establish their own burrows, although some species disperse as soon as they are weaned.

Characteristics

Norris ''et al.'' listed several characteristics present in all members of this family which distinguish them from the rest of the muroids, (the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Eumuroida). These are "the reduction or absence of external eyes, reduced pinnae, stocky body, short tail (<50% head and body length), broad rostrum, triangular-shaped braincase, infraorbital canal ovoid shape and does not extend ventrally to the roof of the

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...

, zygomatic plate absent or much reduced, nasolacrimal canal inside infraorbital canal, incisive foramina small to medium-sized, extensive neck musculature and prominent points of attachment on the occipitum, minimal reduction in M3 relative to M1 and M2, and a distinct orientation of the manubrium of the malleus bone." Spalacid genomes also share a derived filovirus-like nucleoprotein element with an open reading frame.

Classification

The spalacids are classified in three subfamilies, six

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

, and 37

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. Family Spalacidae *Subfamily Myospalacinae - zokors **Genus '' Myospalax'' ***''Myospalax myospalax'' species group **** False zokor, ''M. aspalax'' **** Siberian zokor, ''M. myospalax'' ***''Myospalax psilurus'' species group **** Transbaikal zokor, ''M. psilurus'' **Genus '' Eospalax'' *** Chinese zokor, ''E. fontanierii'' *** Rothschild's zokor, ''E. rothschildi'' *** Smith's zokor, ''E. smithii'' *Subfamily Rhizomyinae **Tribe Rhizomyini - bamboo rats ***Genus '' Rhizomys'' **** Hoary bamboo rat, ''R. pruinosus'' **** Chinese bamboo rat, ''R. sinensis'' **** Large bamboo rat, ''R. sumatrensis'' ***Genus '' Cannomys'' **** Lesser bamboo rat, ''C. badius'' ***†Genus '' Brachyrhizomys'' (Miocene to Pleistocene) **Tribe Tachyoryctini ***Genus '' Tachyoryctes'' - African mole-rats **** Ankole African mole-rat, ''T. ankoliae'' **** Mianzini African mole-rat, ''T. annectens'' **** Aberdare Mountains African mole-rat, ''T. audax'' **** Demon African mole-rat, ''T. daemon'' **** Kenyan African mole-rat, ''T. ibeanus'' ****

Big-headed African mole-rat The big-headed African mole rat (''Tachyoryctes macrocephalus''), also known as the giant root-rat, Ethiopian African mole rat, or giant mole rat, is a rodent species in the family Spalacidae. It is Endemism, endemic to Ethiopia's Bale Mountains. ...

, ''T. macrocephalus'' **** Navivasha African mole-rat, ''Tachyoryctes naivashae'' **** King African mole-rat, ''T. rex'' **** Rwanda African mole-rat, ''T. ruandae'' **** Rudd's African mole-rat, ''T. ruddi'' **** Embi African mole-rat, ''T. spalacinus'' **** Northeast African mole-rat, ''T. splendens'' **** Storey's African mole-rat, ''T. storeyi'' *Subfamily Spalacinae - blind mole-rats **Genus '' Spalax'' *** Mehely's blind mole-rat'', S. antiquus'' *** Sandy blind mole-rat, ''S. arenarius'' *** Giant blind mole-rat, ''S. giganteus'' *** Bukovina blind mole-rat, ''S. graecus'' *** Oltenia blind mole-rat, ''S. istricus'' (possibly

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 ...

) *** Greater blind mole-rat, ''S. microphthalmus'' *** Kazakhstan blind mole-rat, ''S. uralensis'' *** Podolsk blind mole-rat, ''S. zemni'' **Genus '' Nannospalax'' - small-bodied mole-rats ***Subgenus ''Nannospalax'' **** Middle East blind mole-rat or Palestine mole-rat, ''N. ehrenbergi'' ***Subgenus ''Mesospalax'' **** Lesser blind mole-rat, ''N. leucodon'' **** Anatolian blind mole-rat or Nehring's blind mole-rat, ''N. xanthodon''

References

Bibliography

*Jansa, S. A. and M. Weksler. 2004. Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

sequences. Molecular Phylogenetics and Evolution, 31:256-276. *Michaux, J., A. Reyes, and F. Catzeflis. 2001. Evolutionary history of the most speciose mammals: molecular phylogeny of muroid rodents. Molecular Biology and Evolution, 17:280-293. *Steppan, S. J., R. A. Adkins, and J. Anderson. 2004. Phylogeny and divergence date estimates of rapid radiations in muroid rodents based on multiple nuclear genes. Systematic Biology, 53:533-553. {{Taxonbar, from=Q557935 Rodent families Muroid rodents Extant Miocene first appearances Taxa named by John Edward Gray