Image from page 295 of "Bulletin of the British Museum (Natural History) Zoology" (1991-92)

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Title: Bulletin of the British Museum (Natural History) Zoology Identifier: bulletinofbritis5758farn Year: 1991-92 (1990s) Authors: Farn, Alexander E Subjects: Publisher: London : Butterworths Contributing Library: Natural History Museum Library, London Digitizing Sponsor: Natural History Museum Library, London View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: 56 P.D. JENKINS Text Appearing After Image: Fig. 3 Lateral view of skulls, top row left Microgale cowani, right M. gracilis, bottom row left M. thomasi, right M. dryas. Scale 500 mm. M. dryas and M. gracilis is in the size of the talon of the molariform maxillary teeth; this is large in M. dryas but in M. gracilis is effectively absent and more reduced than in any other species. Microgale dryas and M. thomasi differ in the following dental features. The distostyle of I1 is more robust and greater than 50% of the height of the principal cusp in M. dryas, while it is more slender and less than 50% of the height of the principal cusp in M. thomasi. A mesiolingual accessory cusp is present on I3 in M. thomasi but absent in M. dryas. A mesiolingual cusp is present and the distostyle is larger, more robust and approximately one third of the height of the principal cusp in M. thomasi, while in M. dryas the mesiolin- gual cusp is absent or reduced to a ridge and the distostyle is small, slender and approximately one quarter the height of the principal cusp. In M. dryas the anterior ectostyle of P3 is well defined and separated from the distostyle, and the talon is large, unlike the condition in M. thomasi in which the anterior ectostyle is not separated and the talon is small. The posterior ectostyle and distostyle of P4 are moderately well defined and separated from the anterior ectostyle by a notch, the talon is large with a well defined cusp in M. dryas but in M. thomasi there is no posterior ectostyle, the distostyle is barely evident and merges with the anterior ectostyle, and while the talon is moderately large it lacks a well defined cusp. A posterior ectostyle is present on M1 and the talon is large and unicuspid or bicuspid in M. dryas but in M. thomasi there is no posterior ectostyle and the talon is medium sized and unicuspid. In all the molariform teeth the talon of M. dryas is larger than that of M. thomasi. There are fewer differences in the mandibular teeth of the two species. The incisors are similar but there are no diastemata between the incisors of M. thomasi, while in M. dryas a diastema is present between I3 and the canine of all specimens and between I2 and I3 of three of the four specimens. An anterior accessory cusp is present on the canine in M. dryas but not in M. thomasi. Although P2 is similar in both species, there is a slight difference in shape, in M. dryas the tooth is anterof- lexed and tends to be caniniform, while in M. thomasi it is not anteroflexed and more molariform in appearance. P2 and P2 in both species are larger relative to the rest of the toothrow than in any other species (see Table 1). The molariform teeth (P4 to M3) are similar in the two species except that the anterior face of the paraconid of Mj and M2 is markedly convex in M. dryas but only slightly convex in M. thomasi. DISCUSSION Microgale is a taxonomically complex genus containing many named forms, over half of which were shown to be juveniles or morphological variants (MacPhee, 1987). In his revision, MacPhee demonstrated the high morphological within- species variation found in the genus, and described and Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.