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Class Mammalia
Order Rodentia
Family Heteromyidae

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Chaetodipus—Spiny Pocket Mice // Chaetodipus/Perognathus—Spiny or Silky Pocket Mice // Dipodomys—Kangaroo Rats // Perognathus—Silky Pocket Mice // Microdipodops—Kangaroo Mice // Prodipodomys—Prodipodomys Kangaroo Rats

Heteromyidae—Kangaroo Rats and Pocket Mice

The word "heteromyidae" can be translated as "different mice", and the name fits. Although related to the pocket gophers (heteromyids and geomyids are placed in the superfamily Geomyoidea), they've taken a different ecological/morphological route. Instead of the heavy skeleton adapted for constructing burrows, the heteromyids are lightly built and most have some adaptations for a jumping (saltatorial) mode of locomotion. This is carried to the extreme in the kangaroo rats

lateral view of dorsal skull of Dipodomy merriami showing infraorbital foramen, weak zygomatic arch, and enlarged auditory region.Among the characteristics of this family are grooved upper incisors, infraorbital foramena opening on the side of the rostrum, enlarged bullae, weak zygomatic arches, and the fur-lined pockets (shared with the pocket gophers) that are external, opening beside the mouth rather than inside of the mouth as in some other rodents. In Dipodomys, the cheekteeth are unrooted; in the pocket mice, they are rooted.

Fig. 1. Lateral view of the dorsal skull of Dipodomys merriami, showing the infraorbital foramen opening on the side of the rostrum, the weak zygomatic arch, and the greatly enlarged auditory region.

Dorsal view of Dipodomys spectabilis skull and lateral view of left dentary.   Dorsal view of Chaetodipus eremicus skull and lateral view of left dentary.

Fig. 2 (left). Dorsal view of the skull of the Banner-tailed Kangaroo Rat (Dipodomys spectabilis) and lateral view of its left dentary. Scale in mm. Fig. 3 (right). Dorsal view of the skull of the Chihuahuan Pocket Mouse (Chaetodipus eremicus) and lateral view of its left dentary. Scale in mm (note the scale difference between the two images). The very weak zygomatic arches are broken away in Fig. 3.

In the figures, the enlarged bullae are prominent, forming much of the back of the skull of Dipodomys. Pocket mice differ among themselves in the degree of enlargement of the bullae, but they are enlarged to some degree in all. In the genus Perognathus, the bullae are much more enlarged than in Chaetodipus. In the image of the Chihuahuan Pocket Mouse, the pale structures at the hind quarters of the skull are the mastoid bullae.

Wentral view of Dipodomys merriami anterior skull and upper palate and toothrows.

Fig. 4, left. Close-up of the anterior skull of Merriam's Kangaroo Rat showing the typical configuration and the grooved upper incisors. Fig. 4, right. Palate of Merriam's Kangaroo Rat showing the upper cheekteeth. As in the geomyids, the enamel capping the teeth is quickly worn away, leaving an interrupted ring of enamel around dentine.

Ventral view of anterior Chaetodipus eremicus skull.

Fig. 5. Ventral view of the anterior skull of Chaetodipus eremicus. The cheekteeth are typical of moderately worn pocket mouse dentition. The zygomatic arch has broken away in this specimen.

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Last Update: 1 Apr 2014