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Anops kingii, Keel-headed Worm Lizard
Dr. Jessie Maisano - The University of Texas at Austin
Anops kingii
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Field Museum of Natural History (FMNH 80100)

Image processing: Dr. Jessie Maisano
Publication Date: 15 May 2003


Anops kingii can be found from southeastern Brazil and Uruguay to the Chubut Province of southern Argentina. Individuals can reach 205 mm snout-vent length (SVL), with the achievement of sexual maturity at approximately 155 mm SVL. They are generally found under rocks, and their diet consists mainly of coleopteran and lepidopteran larvae.

Anops kingii is a member of Amphisbaenia, a lineage (160 species) of mostly limbless burrowing squamates. The amphisbaenian skull classically has been difficult to study due to its small size (this skull measures just 10.1 mm in length) and largely closed construction, but high-resolution industrial CT offers a solution to these problems. There are four major amphisbaenian groups: Bipedidae, the only one to have forelimbs; Amphisbaenidae, the most diverse (149 species) and widespread (to which Anops belongs; see also Loveridgea ionidesii and Geocalamus acutus); Trogonophidae, whose members use an oscillating excavation pattern (see Diplometopon zarudnyi); and Rhineuridae, represented by numerous fossils (see Rhineura hatcherii) but only one extant species. Amphisbaenians occur in northern and sub-saharan Africa, southwest Asia, the Mediterranean, South America east of the Andes, the West Indies, western Mexico, Baja California, the southeasternmost United States, and Cuba. They are generally poorly represented in collections, and little is known of their life history, because of their burrowing lifestyle.

head morphotypes

There are four basic amphisbaenian head morphotypes, each of which appears to correspond to a different burrowing mode: 'round-headed', 'shovel-headed', 'spade-headed', and 'keel-headed'. Anops presents the most extreme case of the 'keel-headed' morphotype; this is readily apparent when compared to the 'shovel-headed' Rhineura hatcherii.

Amphisbaenians, like other squamates, have paired evertible hemipenes, a transverse cloacal slit, and shed their skin in its entirety. They differ in that they have a highly modified skull architecture, a unique modification of the ear called the extracolumella, and skin with annuli (rings, like a worm -- hence the common name).


It is difficult to discern exactly where amphisbaenians fit in the squamate tree, as even the earliest-known fossil representatives already exhibit the highly derived cranial morphology seen in living forms. Phylogenetic analyses based on morphology tend to place amphisbaenians with the other two major limbless squamate clades -- snakes and dibamids; however, this may be due to convergence of characters correlated with a burrowing lifestyle rather than ancestry.

About the Species

This specimen was collected from Rio Grande do Sul, Porto Alegre, Floresta, Brazil by Dina Buriak on 24 May 1951. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Jessie Maisano of The University of Texas and Dr. Maureen Kearney of the Field Museum of Natural History. Funding for scanning was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.

Dorsal view of specimen

Lateral view of head

Dorsal view of head

About this Specimen

The specimen was scanned by Richard Ketcham on 11 February 2003 obliquely along the coronal axis for a total of 663 slices, each slice 0.0192 mm thick with an interslice spacing of 0.0192 mm.

About the

Gans, C. 1978. The characteristics and affinities of the Amphisbaenia. Transactions of the Zoological Society of London 34:347-416.

Gans, C., and C. Rhodes. 1964. Notes on amphisbaenids (Amphisbaenia, Reptilia). 13. A systematic review of Anops Bell, 1833. American Museum Novitates 2186:1-25.

Gans, C., and E. G. Wever. 1972. The ear and hearing in Amphisbaenia (Reptilia). Journal of Experimental Zoology 179:17-34.

Kearney, M. In press. Systematics and evolution of the Amphisbaenia (Reptilia: Squamata) based on morphological evidence from fossil and living forms. Herpetological Monographs.

Vanzolini, P. 1999. On Anops (Reptilia: Amphisbaenia: Amphibaenidae). Papeis Avulsos de Zoologia 41:1-37.

Zangerl, R. 1944. Contributions to the osteology of the skull of the Amphisbaenidae. American Midland Naturalist 3:417-445.

Vega, L. E. 2001. Reproductive and feeding ecology of the amphisbaenian Anops kingii in east-central Argentina. Amphibia-Reptilia 22:447-454.


Amphisbaenidae page from the EMBL Reptile Database

& Links

None available.


To cite this page: Dr. Jessie Maisano, 2003, "Anops kingii" (On-line), Digital Morphology. Accessed July 22, 2024 at http://digimorph.org/specimens/Anops_kingii/.

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