Brian J. Stafford

GLIDING BEHAVIOR OF JAPANESE GIANT FLYING SQUIRRELS (PETAURISTA LEUCOGENYS)

Abstract Gliding behavior of Japanese giant flying squirrels, Petaurista leucogenys, was studied at Nara Park, Japan. We observed 150 glides. We were able to calculate glide ratios on 57 glides and airspeeds on 29 glides. Glide ratios (distance/[altitude lost]) averaged 1.87, and a glide ratio of 3–3.5 seems to represent an upper performance limit for P. leucogenys. Airspeeds (4.39–9.47 m/s) were substantially lower than reported in other studies, and glide angles were higher (17.74–34.99°). Aspect ratios of the animals in mid-glide averaged 1.42.

CRANIODENTAL FUNCTIONAL MORPHOLOGY AND TAXONOMY OF DERMOPTERANS

Abstract Craniodental form and function were evaluated in the 2 extant, parapatric species of dermopterans (Dermoptera: Cynocephalidae). The level of morphological distinction between the 2 taxa was such that were they known as fossils; most taxonomists would not contest their genus-level distinction as indicative of adaptive differentiation. In fact, these taxa exemplify the widely employed but implicit morphological distance-based standards used for delineating mammalian genera in the paleontological literature. Appropriate names for these 2 taxa are Cynocephalus volans for the Philippine flying lemur and Galeopterus variegatus for the heterogeneous populations of the Sundaic flying lemurs. Cynocephalus probably has a hypertrophied version of the ancestral cynocephalid molar complex and modified incisor and canine morphology. The hypertrophied metaconules of cynocephalids occlude with an expanded paracristid and a cusplike shelf, the distocuspid. Cynocephalus also has a broader rostrum, a greater degree of postorbital constriction, and enhanced ectocranial ridges associated with a more robust masticatory musculature than Galeopterus. Cynocephalus appears adapted to a diet that requires a greater degree of shearing by the anterior dentition and crushing by the molariform dentition. These anterior shearing teeth (I3, C1, P3, c1, p3) are larger and more bladelike than those of Galeopterus, and the bite force is more anteriorly directed. Angle of the mandible is ventrally expanded in Cynocephalus, facilitating enhanced chewing force for the postcanine dentition while maintaining orientation of the temporalis muscle. Dwarfed forms of Galeopterus are found on many of the smaller islands of the Sunda Shelf and in central Laos. They are not morphologically distinguishable from larger members of this species, other than in size, and do not warrant specific distinction. However, it may be desirable to designate 4 subspecies of G. variegatus: G. v. variegatus from Java, G. v. temminckii from Sumatra, G. v. borneanus from Borneo, and G. v. peninsulae from the Malay Peninsula and mainland Southeast Asia. Separate species rank for each of the dwarfed populations should not be recognized. Phylogenetic relationships of Dermoptera are discussed in light of the morphological differences of the 2 genera.

Three-dimensional CT image analysis of the digging system in the aardvark

We examined the bone movement in the forepaw and hind paw in the aardvark (Orycteropus afer) by using three-dimensional (3D)-computed tomography (CT) techniques and osteometrical methods to confirm the functional adaptation of the extremities as a digging system. The four metacarpal bones could be strongly bent from the distal carpal bones. The distal end of the second and third metacarpal bones possessed enlarged smooth articulation surfaces that allowed the proximal phalanx to bend at a sharp angle. However, the articulation surface was not well-developed in the distal end of the fourth and fifth metacarpal bones and the proximal phalanx could bend at smaller angle in these two lateral digits. The proximal phalanges sharply crook from the metatarsal in the first, second, third and fourth digits in the hind paw. We suggest that the medial two digits in the forepaw directly contribute to the crushing, when these proximal phalanges crook in the phase of power stroke. In contrast the lateral third and fourth digits may act as sweeper of the crushed soil. These suggestions regarding the different functional adaptation between medial two digits and lateral two digits are consistent with the anatomical data of the forearm musculature. In the hind paw, we suggest that the second, third and fourth digits are functionally similar and that the hind paw may not act as a crushing apparatus but as a running motor or soil-sweeper similarly using these main three digits.