On the comparative osteology of the passerine bird Arachnothera magna / by R.W. Shufeldt.

  • Robert Wilson Shufeldt
Date:
1909
Catalogue details

Licence: In copyright

Credit: On the comparative osteology of the passerine bird Arachnothera magna / by R.W. Shufeldt. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    13/22 page 537
    OF TIIF FASSERINK HlllU ARACIINOTHEUA MAGN’A. 1909.] r)o7 dorsal aspect; the pair of “ notches ” in the xiphoidal extremity giving rise to an outer xiphoidal process upon either side; the deep “ keel ” with its prominent carinal angle, anteriorly; and, finally, the fact that the bone is more or less pneumatic. The coracoids never decussate in their sternal beds, though in some species they almost appear to do so. Again, the hypocleidimn of the furcula never comes in contact with the manubilal process of the sternum, though in some species the approach is extremely close {Entomyza cyanotis). So mi;ch for the general characters, and Arachnothera has them all to perfection ; and there are a feio minute jmeumatic foramina in the middle line on the dorsal aspect of the bone, anteriorly, in this species. If we designate the length of the stevmmi by a line extending fi'om the apex of*the cailnal angle of the keel to the mid-xiphoidal jJoint posteriorly where the keel terminates, then this distance in A. magna measures 2'3 centimetres. This same measurement will be applied in the case of the sterna of the other species—as, for example, in Arachnothera longirostris, the length of the sternum is but T5 cms., and we find the body of the bone fatter, the xiphoidal notches comparatively deeper, the cai-inal angle not so acute, and the keel of the manubi-ium conspicuous and produced well down upon the anterior border of the sternal cai-ina . The pneumatic foramina are scarce and in the same locality. In Lcptocoma grayi the sternum has a length of but T3 cms. In Cyanerpes cyanea, as representing the Coerebidte, it measures T7 cms., and here the bone is very thin and delicately constructed, with a small manubrium ; deep notches and dilated exti-emities to the xiphoidal processes. These charactei'S do not apply to the sternum of Cvereba chlorojyyga, another of the Coorebida’, a species having the bone only T2 cms. long. Anthreptes malaccensis has a sternum which is the counterpai't of that bone in A. magna, only it is much smaller, having a length of but T4 cms. Among the larger forms of the Meliphagidje we meet with characters in the sternum that are absolutely diagnostic, as, for example, there is no such a thing as mistaking the species had we but this bone to help us in such a bird as Acanthogenys rnfigularis. Here, although it is of the usual passerine type, it is peculiar in having the antei-ior border of tbe sternal body very much thickened and rounded; this thickening is continued across the base of either costal process and up on to the mesio-posterior margin of the same. Such a thickening also defines the limits laterally of a deep mesio-longitudinal groove, deepest anteriorly, that is found upon the dorsal aspect of the body of the bone. For its anterior moiety, thickly crowded together at the bottom of this groove, we fin(l some thirty or forty pneumatic foramina! openings. Between the coracoidal grooves there is another single pneumatic foramen, and the external angles of the mid- xiphoidal prolongation are pronounced. The carinal angle is Proc. Zool. Soc.—1909, No. XXXY. 35 [11]
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