Description This new species is included within the Rhinella margaritifera (= Bufo margaritifer) group, with the following combination of characters: (1) size of adult males in type series 36.0–45.3 mm SVL, adult females in type series 43.1–53.3 mm SVL, (2) snout pointed in dorsal view, protrunding beyond margin of lip, (3) nostril lateral, protuberant, (4) canthal crest not raised, (5) supraorbital crests not developed, (6) supratympanic crest prominent, (7) supraorbital and supratympanic crests continuous, both with tubercles, (8) tympanic membrane distinct, (9) bony protrusion at angle of jaws, (10) parotoid glands small and not very distinct, (11) upper eyelid without projections, (12) presence of a dorsolateral line of tubercles that extends from behind the eye along the side to the base of the legs, (13) neural crests of vertebrae absent, (14) skin on dorsal, dorsolateral and ventral surfaces with spicules in males and females, (15) first finger shorter than second finger, (16) rudimentary lateral fringes on both sides of all fingers, except the outer edge of finger III, (17) a line of spinose tubercles on all lateral fringes except on the outer edge of finger IV, (18) all toes webbed in males and females, (19) lateral fringes present on all toes in females and all but the fourth toe in males, (20) nuptial excrescences present in the first two fingers of males.
Bufo (Rhinella) magnussoni has been collected only from the type locality, Belterra municipality (03.15313°S, 54.84216°W), Pará state. However, it has also been seen and heard calling in the Floresta Nacional do Tapajos, at km 72 on the BR 163 highway, Belterra municipality (A. P. Lima, unpubl. data). This species inhabits the leaf litter of forests.
Life History, Abundance, Activity, and Special Behaviors Male Bufo (Rhinella) magnussoni call frequently during daylight hours from leaf-litter distant from streams or terrestrial pools. Most males called from below fallen leaves. Approximately 60 calling males were heard within a 2 km x 0.5 km area. At night, males and females are found resting on vegetation, 30 to 150 cm above ground.
Reproduction appears to be seasonal and occurs between January and March. Oviposition sites are pools of water that form on fallen tree trunks. They typically contain tadpoles of Bufo (Rhinella) magnussoni in more than one developmental stage, indicating that clutches were deposited in the same site at different times. Tadpoles eat conspecific eggs.
Trends and Threats Deforestation of areas in the type locality appears to be the main threat to this species.
Possible reasons for amphibian decline
General habitat alteration and loss Habitat modification from deforestation, or logging related activities