We obtained data on time of sexual maturity, dimorphism, fecundity and on the reproductive cycle of Mastigodryas boddaerti (Sentzen, 1796) through the examination of 321 preserved specimens, of which 221 were collected in the Brazilian Amazon region and 100 in the Cerrado savannas of Central Brazil. The degree of sexual size dimorphism (snout-vent length, SVL) was significantly greater in the specimens from the Cerrado in comparison with those from the Amazon. Females had a significantly larger number of ventral scales, on average, whereas males had more sub-caudal scales. However, there was no intersexual difference in tail length or head width, although the heads of the males were significantly longer, which may reflect dietary differences. Breeding females from the Amazon region contained between one and six eggs (N = 12, mean = 3.0), whereas two females from the Cerrado had four to six eggs (N = 10, mean = 5.0). No relationship was found between the SVL of the Amazonian females and the number of eggs or vitellogenic follicles they contained (Cerrado females were not analyzed here due to small sample size). Males are smaller than their female counterpart when they reach sexual maturity. Even though females from the Amazon reproduce throughout the year, females from the Cerrado breed seasonality.

Os resultados apresentados correspondem à primeira análise molecular feita acerca das afinidades filogenéticas do gênero Sibynophis, um colubróideo de origem asiática. Sibynophis aparece como sendo o grupo-irmão do gênero Neotropical Scaphiodontophis. Embora Liophidium esteja por vezes associado a estes dois gêneros, a sua relação é apenas distante. Os caracteres morfológicos compartilhados entre Liophidium, Sibynophis e Scaphiodontophis correspondem a homoplasias que refletem provavelmente os hábitos alimentares especializados semelhantes, presentes nos três gêneros em questão. A tradicional subfamília Sibynophiinae é elevada ao nível de família, enquanto que Scaphiodontophiinae passa para sua sinonímia.

We present the results of the first molecular analysis of the phylogenetic affinities of the Asian colubroid genus Sibynophis. We recovered a sister-group relationship between Sibynophis and the New World Scaphiodontophis. Although Liophidium sometimes is associated with these genera, the relationship is distant. Morphological characters that Liophidium shares with Sibynophis and Scaphiodontophis are resolved as homoplasies that probably reflect the similarities of their specialized feeding habits. The traditional subfamily Sibynophiinae is elevated to the family-level, and Scaphiodontophiinae is placed in its synonymy.