Art. Xix.—On the Occurrence of a Pneumatic Foramen in the Femur of a Moa.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 27, 1894, Page 173

Art. Xix.—On the Occurrence of a Pneumatic Foramen in the Femur of a Moa. By Captain F. W. Hutton, F.R.S. [Read before the Philosophical Institute of Canterbury, 2nd May, 1894.] Plate IX. In his second paper on Dinornis Sir R. Owen remarks, on some moa remains from Poverty Bay, that “in only one out of eighteen femora are the parietes of the bone deficient at the part where the air is admitted into the interior of the shaft in the ostrich, emu, rhea, and cassowary; but in the exceptional instance cited the cavity dces not lead to the interior of the bone, and may be due to accidental fracture, as there is a similar opening on the opposite side. In all the other femora of the Dinornis the parietes at the back part of the proximal extremity of the bone are entire, as in the Apteryx; and both the weight and cancellous structure of these bones prove the accuracy of the statement made in the original description of the original fragment that the Dinornis retains the medullary contents of the cavities of the femur throughout life, as in the Apteryx.”* Trans. Zool. Soc., iii., p. 248; and “Extinct Birds of New Zealand,” p. 86. In the large number of femora of moas of all ages which have passed through my hand I have never, before now, noticed an opening for an air-sac—although there are usually two nutrient foramina in the place where the air-canal exists in the emu—and this absence of a pneumatic foramen in the femur is taken as one of the most essential characters of the

Dinornithidae; so much so that both Dromornis australis and Dinornis (?) queenslandice were placed by their original describers among the moas largely because in them also the femur is non-pneumatic. Nevertheless this character is not absolutely constant even in the true Dinornithidae of New Zealand. I now exhibit to the members a femur of an adult bird belonging to Pachyornis pygmceus, from the Te Aute Swamp, near Napier, in which the pneumatic foramen is well developed (Plate IX., p.f.). The opening is subtriangular in shape, and about half an inch in diameter. It is placed at the posterior base of the neck, slightly more interior than the same cavity in the emu. The interior-lower margin is broken, and evidently extended further, but the external and upper margins are quite smooth and rounded, and are unquestionably in their natural condition, so that the interior – lower margin could not have extended much farther. The canal leading from the opening is divided by a longitudinal septum into two parts, each of which contracts into a narrow tube, through which a fine wire can be pushed into the interior of the bone. Probably no air-sac penetrated into the canal, but blood-vessels alone passed through the two tubes. Nevertheless the large opening is evidently a reversionary character, and a proof that a pneumatic canal and air-sac existed in the ancestors of the moas. Explanation of Plate IX. Posterior aspect of left femur of Pachyornis pygmceus, reduced to 5/9 natural size: p.f., pneumatic foramen.