Morphology and postnatal ontogeny of the dentition of Chthonerpeton indistinctum (Gymnophiona: Typhlonectidae): Supplementary material

The gross
morphology, histology and postnatal ontogeny of the dentition of the viviparous
and direct-developing typhlonectid Chthonerpeton
indistinctum were described and compared with other caecilian species. C. indistinctum exhibited the typical pedicellated
condition present in lissamphibians, with a conical monocuspid crown. Our histological
analysis demonstrated that the tissue joining crown and pedicel was formed by
two bands (internal and external), whereas the external band circumvented the
complete periphery of the tooth junction. Likely this condition was not
described for another gymnophionan species. In viviparous and some oviparous
caecilians, dentition changes radically during ontogeny. Thus, there is a
foetal dentition arranged in multiple rows of teeth (i.e. tooth patch), which
is replaced by single tooth rows in neonate or juvenile individuals. Details of
dentition in the lower jaw of neonate specimens are firstly reported for C. indistinctum herein, adding another
member of Typhlonectidae. In some slightly larger specimens the foetal tooth patch
on the lower jaw coexisted with a lingual row of the adult-type teeth, indicating
that replacement of foetal dentition in the lower jaw did not take place just
after birth. The number of teeth, a character widely employed among caecilian
species descriptions, varies during postnatal ontogeny. Hence, we concluded that
at least for typhlonectid caecilians, tooth number should not be considered as
a character with a strong taxonomic value without considering the intraspecific
ontogenetic variation. An extensive survey exploring the relationship between
body length and tooth count becomes necessary to test the usefulness of tooth
counts in species diagnosis.