Fig. 92.—Skull of Anteater (Myrmecophaga). Lateral view, al.sph, Alisphenoid; cond, condyle of mandible; cor, coronoid process of mandible; ex.oc, exoccipital; ext.aud, external auditory meatus; fr, frontal; ju, jugal; lcr, lachrymal; max, maxilla; nas, nasal; occ.cond, occipital condyle; pal, palatine; par, parietal; p.max, premaxilla; s.oc, supraoccipital; sq, squamosal; ty, tympanic. (From Parker and Haswell's Zoology).
The skull of the Anteater[[100]] is very long and low; the fore-part is tubular, and there appear to be no traces of teeth. The premaxilla is very small; the zygomatic arch is imperfect, and does not reach the squamosal behind. A curious feature of this genus, which it shares with some Dolphins and other Whales, is that the pterygoid bones develop palatine plates which meet each other in the middle line, and thus shift the opening of the
posterior nares backwards. This is also, of course, a character of various lower vertebrates. Another Whale-like character in the skull is the weak character of the mandible, which does not give off a marked coronoid process. But then in neither group is there much mastication. The tympanic, periotic and squamosal are ankylosed together. A peculiarity of the cervical vertebrae is that (as in the Camels) the vertebrarterial canal of several of the vertebrae perforates the pedicle obliquely. There are fifteen or sixteen dorsal and three or two lumbar vertebrae. The additional zygapophyses upon the former have been already referred to. The mode of articulation of the ribs is highly singular.
| Fig. 93.—Skull of Anteater (Myrmecophaga). Ventral view. Letters as in Fig. 92. In addition, b.oc, basioccipital; glen, glenoid surface for mandible; pter, pterygoid. (From Parker and Haswell's Zoology.) | Fig. 94.—Side view of three mesosternal segments of a young Anteater (Tamandua), showing the mode of articulation of the sternal rib (sr). mst, The upper or inner surface of the mesosternal segment; sy, the synovial articulation between the segments. (From Flower's Osteology, after Parker.) |
Each segment of the sternum (of which there are eight) is separated from the next by a synovial membrane: and it has on either side two facets for articulation with the ribs. The way in
which these latter bones are connected with the sternum is curiously like their mode of connexion with the spinal column at their other end. With this may be possibly compared the double articulation of the single rib (which articulates with the sternum) in the Rorquals. In Cycloturus this mode of articulation does not occur.
The manus of Myrmecophaga is five-fingered. Of these the third digit (as in Perissodactyles) is the most prominent; it is at least double the width of the second or third finger; the pollex is very slender. In the little Cycloturus this is carried to a greater extent: the third digit is relatively enormous; the first and the fourth have become quite rudimentary; while the fifth is only just recognisable as a minute ossification.
Fig. 95.—A, Manus of Great Anteater (Myrmecophaga jubata). × ⅓. B, Manus of Little Anteater (Cycloturus didactylus). × 2. c, Cuneiform; l, lunar; m, magnum; p, pisiform; s, scaphoid; td, trapezoid; tm, trapezium; u, unciform; I-V, digits. (From Flower's Osteology.)