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

  • Shufeldt, Robert W. (Robert Wilson), 1850-1934.
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.

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    SO feebly cleveloj)ed as to be barely noticeable, while the squctmosctl process below it is rather long, though extremely slender. The valley between them is only fairly YV'eH-marked. Humming- birds exhibit simiLar characters with respect to these two apo- physes, but, taken as a whole, there is nothing, beyond the big pars plana in one of this family, to remind us of the orbital cavity as a whole in Arachnothera. To be sure, the anterior wall of the brain-case is deficient in bone in both, markedly so in the Trochilidie, but, in so far as that goes as indicating any affinity between the two groups, it stands for very little. The external aural aperture in the skull of Arachnothera is large, and admits of a full view of the interior of the bony ear. Posteriorly, and to some extent below, this entrance is protected by a thin scroll of bone, seen in so many other 2>vsaerine forms, and very prominent in the Trochilidae *. Among some of the Ccerebidaj, as, for example, in Diglossa baritula, these bony pai'ts of the external ear are remarkably developed ; the ajjerture upon either side looks directly to the front, while the bidbous, thin, and scroll-like wall protecting it above, behind, and below is a striking featiu’e upon this aspect of the cranium. Postei'ioi'ly, the skull of Arachnothera ofiers but little for examination beyond what we wmuld find in the skull of any ordinary passerine bird. The occipital ridge is but faintly defined, while the supi'a-occipital pi'ominence is above the average in size, and especially so in A. longirostris. This is also seen in I'rochilus, whereas among the Meliphagidre it is not the case. Passing to the basis cranii we have to note the large subcircular foramen magnum, and the extremely minute occipital condyle, which is distinctly hemiglobular in form. The basitemporal area is smooth and convex throughout, presenting at the usual localities the foramina for the entrance and exit of vessels and nerves to and fi’om the ci’anial cavity. The double entrance to the Eustachian tubes, one to either side, is shielded below by a very narrow lim of bone. The basi-presphenoidal ro.strum presents nothing peculiar, and is thoroughly codssified anteiioi’ly w'ith the mesethmoid and the pars planae. The quadrate possesses a sharp, compressed orbital process, that in articulation comes in close contact with the cranium. Its mandibular facet for the low'er jaw is double, there being a small mesial elliptical facet and an outer and larger irregular-shaped one. A longitudinal groove stands between them. As usual, the mastoidal articular head is double, and the bone, as a Avhole, is highly pneumatic. Aj^art from the quadrates, all the other osseous structures at the base of the cranium in Arachnothera are characterised by extreme slenderness and delicacy of structure. And, in passing, it may be said that all the articulations, * SnCFELDT, K. W. “Contribution to the Coiniinrntivc Osteologj- of tbe Trodiilidie, Cnprimulgidnn, and CypselidiP.” 1’. Z. S. Loud., I'ec. 1, 1885, pi. Iviii. fig. 2.