Sexual dimorphism in snakes has been mainly evaluated for size and number of some morphological traits, but few studies address on sexual shape dimorphism. Here we evaluated the existence of sexual size and shape dimorphism in the semi-fossorial snake Atractus reticulatus. We use linear and geometric morphometrics to evaluate differences between sexes and among different ontogenetic stages (neonates, juveniles and adults). We have shown that A. reticulatus is sexually dimorphic for some traits such as body length and head shape, with females being larger and having more robust heads than males, but the sexes do not differ in head size. Males and females are sexually dimorphic in head shape even in neonates, suggesting that this differentiation is prenatal. Differences in head shape may be associated with trophic segregation, allowing females to feed on larger prey than males. Body size dimorphism progressively increases throughout the ontogenetic stages, which is possibly related to the late sexual maturation of females and/or different growth rates between the sexes. We also found that males and females shows some sex-specific patterns towards static and ontogenetic allometry, with males showing stronger predictive response on static allometry than females, whereas females have ontogenetic allometry, but males do not. Additionally, the allometric slopes in A. reticulatus between sexes converge by presenting similar shapes as head size increases, an expected result for sexes with similar lifestyles. Further investigation on some physiological and natural history aspects in Atractus will be particularly useful for a better understanding of the significance of the morphological differences found in this study.

蛇的性二态性主要针对某些形态特征的大小和数量进行了评估，但很少有研究针对性形状二态性。在这里，我们评估了半窝蛇白术中性大小和形状二态性的存在。我们使用线性和几何形态计量学来评估性别之间以及不同个体发育阶段（新生儿，青少年和成年人）之间的差异。我们已经证明网纹拟南芥在某些特征（例如身长和头部形状）上是性二态，女性比男性更大，头部更健壮，但性别在头部大小上没有差异。甚至在新生儿中，男性和女性的头部形状也具有两性性，这表明这种分化是产前的。头部形状的差异可能与营养隔离有关，允许雌性以比雄性更大的猎物为食。体型二态性在整个个体发育阶段逐渐增加，这可能与雌性的性成熟较晚和/或性别之间的不同生长率有关。我们还发现，男性和女性在静态和个体发育方面表现出一些特定于性别的模式，其中男性对静态表示的预测反应比女性强，而雌性则具有个体发育的异体形成，而雄性则没有。此外，在性别随着头顶尺寸的增加呈现出相似的形状，从而使网状融合。这是具有相似生活方式的性别的预期结果。对白术中某些生理和自然史方面的进一步研究对于更好地了解本研究中发现的形态学差异的意义将特别有用。