Caecilian anatomy and diversity

Figure 1. Skull of Caudacaecilia weberi (dorsal, lateral, ventral). 
1-premaxilla, 2-nasal, 3-septomaxilla, 4-prefrontal, 5/5a-maxilla, 6-orbit, 
7-opening for nervous fibers and vessels, 8-frontal, 9-squamosal, 
10-parietal, 11-quadrate, 12-columella, 13-os basale, 14-vomer, 
15-choana, 16-pterygoid, 17-opening for mandibular muscles, 18-quadrat,
19-tentacular foramen (source: Taylor, 1968).

Caecilians (order Gymnophiona) are limbless amphibians with reduced or no tail. 

Caecilians are highly specialized for burrowing. They have a snake-like body segmented by annular grooves. These grooves contain dermal scales in some genera. The skull is compact and/or has only reduced windows. Premaxillae are usually fused with nasals, and the palatines are fused with the maxillae (maxillopalatines). 

Frontals distinct from parietals. Eyes reduced, covered by skin, tentacles or by skull bones. Sensorial tentacle between the narines and eyes, sometimes anterior to or below the narines. Left lung usually reduced. Vertebrae amphicoelus. 

 Males have a single, protrusible copulatory organ in the cloaca (phallodeum). All caecilians probably have internal fertilzation; some of them are oviparous and haveaquatic larvae. These larvae have gill slits but no external gills. Size usually between 65 and 1500 mm. 

Subtropical and tropical areas worldwide, except Madagascar and Australia. Most species in the neotropical area (19 genera, 95 species according to Taylor 1968), eastern Asia has 5 genera and 42 species, Africa 7 genera and 22 species. The Seychelles Islands have 7 species in 3 genera (all endemics).