. Biology of the Heteromyidae. Heteromyidae. Fig. 12. —Stages in the development of the infraorbital region of the skull in the heteromyid D. merriami (above) and in the geomyid T. bottae (bottom). In D. merriami, the foramen (i) arises in the maxillary bone (m) of the prenatal individuals at the premaxillary suture (left), where it remains at juvenile (right) and adult stages (not shown). In T. bottae, the infraorbital foramen arises in the maxillary bone at the premaxillary suture as in D. merriami, but bone growth at its cranial margin (left) results in its gradual caudal movement (middle a
. Biology of the Heteromyidae. Heteromyidae. Fig. 12. —Stages in the development of the infraorbital region of the skull in the heteromyid D. merriami (above) and in the geomyid T. bottae (bottom). In D. merriami, the foramen (i) arises in the maxillary bone (m) of the prenatal individuals at the premaxillary suture (left), where it remains at juvenile (right) and adult stages (not shown). In T. bottae, the infraorbital foramen arises in the maxillary bone at the premaxillary suture as in D. merriami, but bone growth at its cranial margin (left) results in its gradual caudal movement (middle and bottom). Drawn from specimens that had been fixed, cleared, and stained for bone and cartilage. Scale bars = 1 mm for fetuses (top, bottom left) and 5 mm for others (from Brylski, unpubl.). mammals functions in preventing the inner ear from overstimulation by excessive sound or in enhancing the frequency tuning of the inner ear is unresolved (Fleischer, 1978). The cochlear differences (including cochlear histology and size of the oval window; Web- ster and Webster, 1975), probably act in concert with the inflated bullae to heighten auditory sensitivity (Webster and Webster, 1984); the influence of the differences in sta- pedial height (see section on carotid circu- lation) on inner ear function has not been addressed in heteromyids. The nasal bones are more tubular and elongated in Dipodomys, Microdipodops and Perognathus than in heteromyines; where Chaetodipus Hes on this spectrum is uncer- tain. In Dipodomys, nasal elongation is thought to increase the amount of water re- sorbed from exhaled air (Schmidt-Nielsen et al., 1970). Several pairs of scrofl-shaped maxilloturbinal bones are found in the nasal passages of heteromyids along the medial surface of each nasal bone. One of these ducts, the nasolacrimal, is continuous cau- dally with the lacrimal duct. In many ro- dents, the nasolacrimal duct carries a pher- omone from the Harderian gland (medial to the eye) to the nos
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