The dwarf crocodile (Osteolaemus tetraspis) is endemic to the equatorial rainforests of central and western Africa, where it frequents small streams. Its range overlaps that of the slender-snouted crocodile (Crocodylus cataphractus). The dwarf crocodile is one of the smallest crocs, with a maximum recorded size of 1.9 meters (6.3 feet). Osteolaemus is considered endangered (Ray et al., 2000), although few thorough wild census reports -- or much information about the species in general -- exist. Liberia enjoyed a high concentration of dwarf crocodiles in recent times, but numbers of individuals have decreased as a result of hunting and deforestation (Kofron and Steiner, 1994).

The generic name Osteolaemus refers to extensive osteoderms covering the throat and neck. Such osteoderms are not unique to Osteolaemus, but are observed in other members of Crocodylia. The specific name tetraspis refers to the four bony plates on the back of the neck. As with Crocodylus, Ostoelaemus can be distinguished from alligators (Alligatoridae) by occlusion of the lower dentition outside the uppers. That is, the lower teeth are visible when the mouth is closed.

Osteolaemus is monospecific, although two subspecies are generally recognized: O. tetraspis tetraspis and O. t. osborni. There is considerable nucleotide variation within Osteolaemus. The dwarf crocodile is included in a clade with Crocodylus, Gavialis and Tomistoma. Molecular evidence places Osteolaemus as the sister taxon to Crocodylus (Aggarwal et al., 1994; Gatesy and Amato, 1992).

Additional Information on the Skull

Click on the thumbnails below for labeled images of the skull in standard anatomical views.

Dorsal view	Lateral view	Ventral view

This specimen (FMNH 98396) was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Chris Brochu of The University of Iowa. Funding for image processing was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.

Lateral view of skull	Dorsal view of skull	Ventral view of skull

This specimen was scanned by Matthew Colbert on 23 June 2005 along the coronal axis for a total of 870 slices. Each slice is 0.11 mm thick, with an interslice spacing of 0.11 mm and a field of reconstruction of 56 mm.

Literature

Aggarwal, R. K., K. C. Majumdar, J. W. Lang, and L. Singh. 1994. Generic affinities among crocodilians as revealed by DNA fingerprinting with a Bkm-derived probe. Proceedings of the National Academy of Science USA 91:10601-10605.

Gatesy, J. and G. D. Amato. 1992. Sequence similarity of 12S ribosomal segment of mitochondrial DNAs of gharial and false gharial. Copeia 1992:240-243.

Kofron, C. P. and C. Steiner. 1994. Observations on the African dwarf crocodile, Osteolaemus tetraspis. Copeia 1994:533-535.

Ray, D. A., P. S. White, H. V. Huyen, T. Cullen, and L. D. Densmore. 2000. High levels of genetic variability in West African dwarf crocodiles Osteolaemus tetraspis tetraspis. Pp. 58-63 in Grigg, G. C., F. Seebacher, and C. E. Franklin, eds. Crocodilian Biology and Evolution. Surrey Beatty and Sons, Chipping Norton.

Links

Osteolaemus tetraspis page on the Crocodilians Natural History and Conservation website

pictures of O. tetraspis on the Animal Diversity Web (University of Michigan Museum of Zoology)