Family Platacanthomyidae
(Malabar spiny dormouse and pygmy dormice)

Platacanthomyidae is a small family of rodents. It contains just three species in two genera: Platacanthomys, the spiny dormouse, and Typhlomys, the pygmy dormice. (Nowak, 1999)

Platacanthomyids have a discontinuous Old World distribution. They are found in several regions of southern India, southern China, and northern Vietnam. (Corbert, 1984)

Platycanthomyids live in moist, rocky, tropical and subtropical forests at elevations of 600 to 2100 meters. They inhabit burrows, tree cavities, and clefts between rocks, often near streams. (Helin, Ohtaishi, and Houji, 1999; Mudappa, Kumar, and Chellam, 2001; Nowak, 1999)

The genera now placed in the family Platycanthomyidae were once grouped in the subfamily Platacanthomyidae and considered to be part of the family Gliridae (Myoxidae), the dormice (Ellerman 1940). However, certain characteristics, such as the absense of premolars, suggest that Platacanthomys and Typhlomys belong within the Muroidea. Some authors have considered the Platacanthomyidae to be a subfamily within Muridae (Alston 1876, Nowak 1999, Corbert 1984) or within Cricetidae (Chaline et al. 1977). Others have argued that Platacanthomyidae should be recognized as a separate family (Musser and Carleton 2005, Simpson 1945, Miller and Gidley 1918). In any case, the relationship between Platacanthomyidae and the rest of the Muroidea remains uncertain, as none of the three platacanthomyid species has been included in recent molecular phylogenetic analyses. (Alston, 1876; Chaline, Mein, and Petter, 1977; Corbert, 1984; Ellerman, 1940; Jansa and Weksler, 2004; Michaux, Reyes, and Catzeflis, 2001; Miller and Gidley, 1918; Musser and Carleton, 2005; Norris et al., 2004; Nowak, 1999; Simpson, 1945; Steppan, Adkins, and Anderson, 2004)

EXTERNAL CHARACTERISTICS:

Platacanthomyids are mouselike in overall appearance, with tail length ranging from 75 to 138 mm and total body length ranging from 70 to 212 mm. Long, stiff hairs form a brush on the tip of the tail. The feet are slim and small with medium long digits. Four of the digits on the front foot have claws, and the fifth is a rudimentary thumb with a nail. The soles of all four feet are naked and have six pads. Long vibrissae protrude from the relatively short muzzle. The ears are prominent and sparsely furred. Sexual dimorphism has not been described in this group.

DENTAL CHARACTERISTICS:

The dental formula is 1/1, 0/0, 0/0, 3/3 = 16. The cheek teeth are high-crowned and parallel ridges of enamel run diagonally across the crowns. The enamel on the incisors is orange. The molars in the upper jaw each have three roots; those in the lower jaw have two. The first two molars are about the same size, and the third is about 2/3 the size of the other two.

SKULL CHARACTERISTICS:

The small, delicate dentary has a low, angular coronoid process that in most specimens is positioned just slightly higher than the condyloid process. The unperforated angular process is not inflected lingually. The wide hard palate terminates anterior to the rear margins of the molar rows. The interorbital region and the interparietal are both broad, the occiput is deep, and the infraorbital foramina are large and narrow. The lateral surface of the alisphenoid canal is formed by the alisphenoid bone. The pterygoid fossa, which may or may not be perforated with tiny holes, is broad, flat, and smoothly continuous with the sides of the braincase. The masticatory-buccinator formanina are coalesced into one opening. The complete, slightly enlarged mastoid is not perforated. The small squamosomastoid foramen is contained within the suture between the squamosal and the mastoid. The auditory bullae are relatively small and lack transbullar septae. (Carleton and Musser, 1984; Helin, Ohtaishi, and Houji, 1999; Nowak, 1999)

The lifespan of platacanthomyids has not been reported.

Very little information is available on the behavior of these rodents. It is known that Platacanthomys is arboreal, and it is assumed that Typhlomys is as well. Platacanthomys individuals use their large, tufted tails as a balancing organ as they hop between branches. They build nests of moss and leaves in tree cavities, among branches, or in rock clefts. One captive Platacanthomys lasiurus was lethargic during the day, allowing itself to be handled without struggle, suggesting nocturnal habits. (Carleton and Musser, 1984; Nowak, 1999)

It is unknown how these rodents communicate. They do have the ability to perceive their world through visual, auditory, tactile, and chemical means, though it is not known how well-developed any of these senses are.

Platacanthomyids reportedly eat leaves, stems, fruit, seeds, and roots. (Corbert, 1984; Helin, Ohtaishi, and Houji, 1999; Nowak, 1999)

There are no reports of predation on platacanthomyids, although it is likely that small to medium-sized predators, such as large snakes, raptors, and mammalian carnivores, will target these species. Native people of southern China and northern Vietnam claim that cats will not eat Typhlomys species. (Nowak, 1999)

Platacanthomyids are herbivores, meaning that they are at least primary consumers in their ecosystem.

In parts of India, Platacanthomys lasiurus are abundant and are referred to as "pepper rats", because they raid and destroy pepper crops. (Corbert, 1984; Nowak, 1999)

There are no known positive impacts of platacanthomyids on humans, except in their roles in the healthy ecosystems they inhabit.

One of the three species in this family, Typhlomys chapensis, the Chapa pygmy dormouse, is listed as critically endangered by the IUCN. This species is known only from a single locality and therefore is extremely vulnerable to habitat destruction. (IUCN, 2004; Nowak, 1999)