Comprehensive Description

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Description

Incilius aurarius is a moderate sized toad with a snout that from the lateral view that is rounded, but from the dorsal view is pointed. Snout-vent length of males varies from 54.5 - 67.5 mm, and in females from 53.1 - 79.5 mm. The tympanum is round and smaller than the eye. Males have moderately developed cranial crests that lack rounded protruberances at the junction of the parietal, supraorbital, and postorbital crests; females have thin, hypertrophied crests much taller than the eye. Both sexes have elongate parotoid glands. Incilius aurarius has short moderate forelimbs with thin hands and fingers that lack webbing. Relative finger lengths are 2 < 4 < 1 < 3. The hind limbs are 44.5% of the SVL and are slender with relative toe lengths of 1 < 2 < 5 < 3 < 4. Toes are connected by thin webbing (Mendelson et al. 2012).

Larval I. aurarius (based on four tadpoles of Gosner stages 32-44) have ovoid, depressed bodies widest slightly posterior to the eyes. Tail musculature is tallest at the base and gradually tapers. The oral disc is small and anteroventral. Overall, the tadpole is indistinguishable from that of I. macrocristatus (Mendelson et al. 2012).

Incilius aurarius adults are similar in appearance to I. macrocristatus, but they lack the dark brown or black markings on the legs and feet that are present on the latter. They can also be distinguished by their less prominent cranial crests, the absence of vocal slits, and a characteristic golden coloration in males. Incilius aurarius males’ golden coloration is less orange than that of I. periglenes (Mendelson et al. 2012).

In life, I. aurarius exhibits easily distinguishable sexual dimorphism in color pattern; females display a variable brown color with markings that are darker brown or black on the dorsum, while males are a uniform golden color that becomes paler as it approaches the ventral surface. Adult males lose the golden color when fixed in formalin and stored in ethanol. The ventral surface of males is cream-colored with faint gray mottling. The iris of the eye is copper-colored with fine black flecking. The ventral surface of females is dark brown with some light cream mottling growing more significant towards the rear of the animal, and the iris of the eye is dark brown with faint copper flecking. Formalin-fixed tadpoles have transparent ventral surfaces and uniformly red-brown dorsal and lateral surfaces. Tail musculature is similarly red-brown, and tail fins are transparent with some thin brown reticulations on the dorsal fin (Mendelson et al. 2012).

Incilius aurarius is part of the “forest toad” clade and was formerly classified under the name Incilius macrocristatus (Mendelson et al. 2011).

The Latin aurarius means “golden”, referring to the coloration of males of this species (Mendelson et al. 2012).

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