Thomson, S. and Georges, A. (1996). Neural bones in chelid turtles. Chelonian Conservation and Biology 2:82-86.
| Species | Specimen Number | N1 | N2 | N3 | N4 | N5 | N6 | N7 | N8 | Pleural Pairs in Contact |
| Aspideretes hurum | UC 0167 | 6P | 6P | 6P | 6P | 6A | 6A | 6A | 6A | VIII |
| Pelomedusa subrufa | UC 0221 | 6A | 6A | 6A | 6A | 6A | 6A | -- | -- | all |
| Chelodina longicollis | UC 0166 | -- | 4 | 3P | 5 | -- | -- | -- | -- | all |
| Chelodina oblonga | QM 59283 | 5P | 7A | 5A | 5A | 6A | 6A | 5A | 5 | I, VII, VIII |
| QM 59272 | 6P | 5P | 4A | 5A | 5A | 6A | 7A | -- | I, VIII | |
| UC 0163 | -- | 6A | 7A | 5A | 5A | 6A | 5A | 5 | I, VII, VIII | |
| UC 0162 | -- | 3A | 8A | 8A | -- | 5 | -- | -- | I, II, V, VI, VII, VIII | |
| UC 0161 | -- | 5A | 6P | 5A | -- | 5A | -- | -- | I, V, VI, VII, VIII | |
| Chelus fimbriatus | PCHP 3985 | 6P | 6A | 6A | 6A | 6A | 6A | 6A | -- | VIII |
| Elseya novaeguineae | AM 42662 | -- | -- | -- | -- | -- | -- | 3 | -- | ALL |
| Elseya sp. (Manning) | AM 123040 | -- | -- | 6A | 6A | 6A | 6P | -- | -- | I, VI, VII, VIII |
| AM 123042 | -- | -- | 5A | 6A | 6A | -- | -- | -- | I, II, V, VI, VII, VIII | |
| QM 59289 | -- | 5P | 6A | 6A | 6A | 5A | -- | -- | I, VI, VII, VIII | |
| QM 59290 | -- | 6A | 6A | 6A | 6A | 5A | -- | -- | I, II, VI, VII, VIII | |
| Elseya sp. (S. Alligator) | QM 59286 | -- | -- | -- | -- | -- | -- | 5 | -- | ALL |
| Phrynops gibbus | UC 0222 | 5 | 6A | 6A | 6A | 6A | -- | -- | -- | I, V, VI, VII, VIII |
Table 1. Neural Formulae of Specimens Examined Possessing Exposed Neurals. Also shown is the number of pleural pairs which make midline contact. Pleural pairs numbered I to VIII, anterior to posterior.
|
It is not clear whether the well developed neurals of Chelodina oblonga or Elseya sp. aff. latisternum (Manning) are ancestral or secondarily derived. Consideration of the currently hypothesised phylogeny for Australian chelids (Georges and Adams, 1992) indicates that if exposed neurals are ancestral for both species, then loss of exposed neurals must have occurred independently at least five times in their evolutionary history, and twice in Chelodina alone (Fig. 3, hatched squares). 
Figure 3. Occurrence of loss of exposed neurals mapped on the currently hypothesized phylogeny of Australian chelids (Georges and Adams, 1992). Open squares assume that in the Manning River Elseya neurals are ancestral and in C. oblonga they are secondarily derived. Hatched squares assume that both species retain ancestral neurals. |
In this scenario, the loss of exposed neurals would have occurred independantly only four times, and only once in Chelodina (Fig. 3, open squares). Acknowledgments We would like to thank the many people who provided specimens for this study including Ross Sadlier (Australian Museum), Patrick Couper (Queensland Museum), Paul Horner (NTM), John Cann, Peter Pritchard and Gerald Kuchling. Bone sections were kindly prepared by Glen Fisher and the drawings were prepared by Rainer Rehwinkel. Peter Pritchard, Anders Rhodin, Russell Mittermeier and the staff and students of the Applied Ecology Research Group provided many useful criticisms of an early draft of this paper. Literature Cited Boulenger, G.A. 1889. Catalogue of the Chelonians, Rhynchocephalians and Crocodiles in the British Museum (Natural History). London: Taylor and Francis. 311pp |