Crocodylus johnstoni, the Australian freshwater crocodile, is one of two species of crocodile that occurs in Australia. The other, C. porosus (the saltwater crocodile), is the largest living crocodylian and one of the world's most dangerous vertebrates. The freshwater crocodile occurs further inland than its larger relative, and although they both share an aggressive nature, the freshwater crocodile is less of a threat to human life. Crocodylus johnstoni rarely exceeds three meters in total length.

The evolutionary history of Crocodylus (the "true crocodiles") is poorly understood. The name has been applied to a wide variety of fossils dating back as early as the Cretaceous (> 65 million years ago), but based on phylogenetic analysis of molecular and morphological data, Crocodylus first appeared within the last 20 million years. Within that time it invaded the world's tropics, from the westernmost Pacific to the Greater Antilles and Mexico. Relationships among living species are undergoing study, and it appears that C. johnstoni is part of a group of species native to the Indian and Pacific Oceans.

Crocodylus johnstoni is one of three species of Crocodylus with a relatively slender snout. The others are C. intermedius (the Orinoco crocodile of Venezuela) and C. cataphractus (the African sharp-nosed crocodile). Extreme cases of long-snoutedness are thought to reflect an adaptation to catching fish, but both C. johnstoni and C. intermedius will eat whatever they can swallow, including fish, arthropods, and small mammals.

This specimen was raised in captivity and died in 1989 at the Northern Territory Crocodile Farms Pty. Ltd., Northern Territory, Australia. It was obtained by the Vertebrate Paleontology Laboratory of the Texas Memorial Museum of Science and History by exchange with Dirk Megirian of the Museums and Art Galleries of the Northern Territory. The individual measured 830 mm in total length, and 440 mm in snout-vent length.

The specimen was made available to Scientific Measurement Systems, Inc. for scanning by Dr. Chris Brochu of the University of Iowa and Drs. Wann Langston and Timothy Rowe of the Department of Geological Sciences, The University of Texas at Austin. Funding for scanning was provided by a 1995 NSF Dissertation Improvement Grant to Dr. Brochu. The skull was scanned along the coronal axis for a total of 771 slices, each slice 0.223 mm thick, with an interslice spacing of 0.223 mm.

Literature

Brochu, C. A. 2000. Phylogenetic relationships and divergence timing of Crocodylus based on morphology and the fossil record. Copeia 2000:657-673.

Brochu, C. A. 2001. Congruence between physiology, phylogenetics, and the fossil record on crocodylian historical biogeography, pp. 9-28. In G. Grigg, F. Seebacher, and C. E. Franklin (eds.), Crocodilian Biology and Evolution. Surrey Beatty and Sons, Sydney.

Brochu, C. A. 2003. Phylogenetic approaches toward crocodylian history. Annual Review of Earth and Planetary Sciences 31:357-397.

Brochu, C. A., and L. D. Densmore. 2001. Crocodile phylogenetics: A review of current progress, pp. 3-8. In G. Grigg, F. Seebacher, and C. E. Franklin (eds.), Crocodilian Biology and Evolution. Surrey Beatty and Sons, Sydney.

Ross, C. A. (ed.) 1989. Crocodiles and Alligators. Facts on File, New York. 240 pp.

Ross, J. P. 1998. Crocodiles - Status Survey and Conservation Action Plan. International Union for the Conservation of Nature, Gland, Switzerland. 96 pp.

Webb, G. J. W., and S. C. Manolis. 1989. Crocodiles of Australia. Reed Books Pty Ltd., Frenchs Forest, NSW Australia. 160 pp.

White, P. S., and L. D. Densmore. 2001. DNA sequence alignments and data analysis methods: Their effect on the recovery of crocodylian relationships, pp. 29-37. In G. Grigg, F. Seebacher, and C. E. Franklin (eds.), Crocodilian Biology and Evolution. Surrey Beatty and Sons, Sydney.

Willis, P. M. A. 1997. Review of fossil crocodilians from Australia. Australian Zoologist 30:287-98.

Crocodylus johnstoni on Crocodilians: Natural History & Conservation

Crocodylus johnstoni page by Dr. Adam Britton on Kingsnake.com

Crocodylus johnstoni on The Animal Diversity Web (The University of Michigan Museum of Zoology)

Hear the calls of Crocodylus johnstoni and other crocodilians at Crocodile Talk

None available.