North American Tadpoles

Jaw Sheaths



Keratinization

The upper (suprarostral) and lower (infrarostral) supportive jaw cartilages have pigmented and keratinized jaw sheaths. The relative amount of dark keratinization (width in longitudinal dimension) of a sheath sometimes is useful for distinguishing among tadpoles.

Drawing showing narrow sheaths Drawing showing medium sheaths Drawing showing wide sheaths

Narrow Sheaths-dark for less than half the width

Medium Sheaths-dark for about half the width

Wide Sheaths-dark for nearly the entire width


Other jaw sheath characteristics are sometimes useful to distinguish among species.

Cuspate and Serrate Jaw Sheaths

Drawing showing cuspate, rounded sheaths Drawing showing cuspate, pointed sheaths Drawing showing serrate, saw-toothed sheaths


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