Crested moa (Pachyornis australis) Dinornithiformes
Biology of crested moa
The crested moa was a heavily built bird which may have had a crest on its head for sexual or territorial display. The skull has multiple pits on its dorsum which are thought to be the insertion sites of the feathered crest, and the jaws are sturdy, suggesting a diet high in fibre such as branches of trees and shrubs (Tennyson and Martinson, 2006).
Brain of crested moa
The endocranial volume of the scanned specimen (AV36430) is 31.0 ml. With a body weight range of 44 to 90 kg, the encephalization quotient would be 0.351 to 0.527.
The specimen is remarkable for the profound retroversion (bending backwards) of the forebrain on the brainstem axis (Figure 1a).
The features of the telencephalic surface (olfactory bulb, parts of the pallium) have left impressions on the skull interior (see Figure 1a). The maxillomandibular foramen transmits the maxillary and mandibular divisions of the trigeminal nerve (5max, 5mand). The optic foramen transmits the optic nerve (2n). The optic lobe is composed of the soft tissue optic tectum, a part of the midbrain which projects ventrolaterally caudal to the telencephalon in birds. The wulst is a dorsal projection of the telencephalon which is made up of the dorsal pallium (or hyperpallium) and the parahippocampal area. The wulst is separated from the rest of the pallial surface by a groove (vallecula), which may be divided into medial and lateral divisions in some avian species, but these divisions are not visible on the moa endocranium. A substantial proportion of the wulst is concerned with vision, so the large wulst but small olfactory bulbs in moa suggest a greater reliance on vision relative to olfaction.
Figure legends
Figure 1 shows images of a 3D reconstruction of the skull of a crested moa (AV36430). The fossil was scanned at Christchurch Radiology Group, St George’s Hospital (Siemens Somatom Definition, 120 kV, 400 mA, 0.6 mm slice thickness). Impressions on the skull interior (Figure 1a) from soft tissue structures have been labelled. Figure 1b shows the pitted dorsum of the skull.
References
Ashwell KWS, Scofield RP (2008) Big birds and their brains: Paleoneurology of the New Zealand Moa. Brain Behavior and Evolution 71, 151-166.
Tennyson A, Martinson P (2006) Extinct Birds of New Zealand. Wellington, NZ: Te Papa Press.
Figure 1 shows images of a 3D reconstruction of the skull of a crested moa (AV36430). The fossil was scanned at Christchurch Radiology Group, St George’s Hospital (Siemens Somatom Definition, 120 kV, 400 mA, 0.6 mm slice thickness). Impressions on the skull interior (Figure 1a) from soft tissue structures have been labelled. Figure 1b shows the pitted dorsum of the skull.