The rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

 family Platacanthomyidae, or Oriental dormice, includes the spiny dormice and the Chinese pygmy dormice. In spite of their appearance, these animals are not true dormice

Dormouse

Dormice are rodents of the family Gliridae. Dormice are mostly found in Europe, although some live in Africa and Asia. They are particularly known for their long periods of hibernation...

, but are part of the large and complex superfamily

Taxonomic rank

In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

 Muroidea

Muroidea

Muroidea is a large superfamily of rodents. It includes hamsters, gerbils, true mice and rats, and many other relatives. They occupy a vast variety of habitats on every continent except Antarctica. Some authorities have placed all members of this group into a single family, Muridae, due to...

. The platacanthomyids can be distinguished from the true dormice, because they have no premolar

Premolar

The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...

s, giving them three cheek teeth, like their relatives, the Muroidea.

The evolutionary relationship of the Platacanthomyidae was uncertain until a molecular phylogenetic study found it to be the earliest extant lineage to branch within the superfamily Muroidea

Muroidea

Muroidea is a large superfamily of rodents. It includes hamsters, gerbils, true mice and rats, and many other relatives. They occupy a vast variety of habitats on every continent except Antarctica. Some authorities have placed all members of this group into a single family, Muridae, due to...

. They can be distinguished from both the family Spalacidae

Spalacidae

The Spalacidae, or spalacids are a family of rodents in the large and complex superfamily Muroidea. They are native to eastern Asia, the Horn of Africa, the Middle East, and south-eastern Europe. It includes the blind mole rats, bamboo rats, root rats, and zokors...

 and the Eumuroida

Eumuroida

Eumuroida is a clade defined in 2004 to describe a group of muroid rodents. The clade is not defined in the standard taxonomic hierarchy, but it is between superfamily and family....

 (all non-spalacid and non-platacanthomyid muroids), by the distinct shape of their infraorbital canal

Infraorbital canal

Not to be confused with the infraorbital groove and infraorbital foramen, which are on opposite ends of the canal.One of the canals of the orbital surface of the maxilla, the infraorbital canal, opens just below the margin of the orbit...

 and by the presence of multiple openings in the palate

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 separate. The palate is divided into two parts, the anterior...

 of the skull. On the basis of these two characteristics, they have been considered to be distinct from all other muroids. More work is needed to determine the evolutionary position of this subfamily.

The Platacanthomyidae contains three genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, and a number of species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, only two of which are still extant.

Taxonomy

• Family Platacanthomyidae
  • Genus †Neocometes
    • †Neocometes brunonis
    • †Neocometes orientalis
    • †Neocometes similis
  • Genus Platacanthomys (spiny dormouse)
    • †Platacanthomys dianensis
    • Platacanthomys lasiurus
      Platacanthomys lasiurus
      The Malabar Spiny Dormouse is a species of muroid rodent endemic to the Western Ghats of India. It is the only extant species in the genus Platacanthomys and although resembling a dormouse is not closely related. About the size of a Brown Rat, this arboreal species lives in tree holes in dense...
      
      (spiny dormouse)
  • Genus Typhlomys Pygmy dormice
    • Typhlomys cinereus (Chinese pygmy dormouse)
    • †Typhlomys hipparionium
    • †Typhlomys intermedius
    • †Typhlomys macrourus
    • †Typhlomys primitivus