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Sexual dimorphism in the ratio of digits length is a morphological feature resulted from the interaction between sex hormones and prenatal Hox genes, the latter is known to control the development of both limbs and genitals. The status of this trend and ratios have been investigated in various animal groups, including humans, other mammals, birds, reptiles, and amphibians. In this study, the body length and sexual dimorphism in the second-to-fourth, second-to-third and third-to-fourth digit lengths ratios (i.e., 2D:3D, 2D:4D, 3D:4D) of left fore and hind limbs were investigated in 54 specimens of toads collected from the northern Iran, including Bufo viridis (16 males and 19 females) and Pelobates syriacus (10 males and 9 females). In addition, the body length of the studied specimens were recorded. The results showed that the average body length (SVL) of female individuals of Pelobates syriacus was higher than those in males, which was found to be statistically significant (P≤0.05). Meanwhile, the average body length (SVL) of female individuals of Bufo viridis was found to be higher than those in males, however, the difference was not statistically significant. No sexual dimorphism was detected in the second-to-fourth, second-to-third and third-to-fourth digit lengths ratios of left fore and hind limbs between the male and female undividuals of Bufo viridis. However, the second-to-fourth digit ratio (2D:4D) in Pelobates syriacus species were found to be significantly different (P=0.040) between the male and female individuals, as the ratio was higher in males than females. Therefore, it could be concluded that the sexual dimorphism in 2D:4D of Pelobates syriacus species is consistent with those in most amphibians and diapsids.

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The status of sexual dimorphism patterns in human and various animal groups including some mammals, birds, reptiles and amphibians have been studied, however, despite the fact that a growing number of studies were aimed to describe sexual dimorphism patterns in external morphological features such as the proportion of toes in animals, our knowledge of some basic issues, specially in some animal groups, is still limited. In this study, sexual dimorphism in terms of external morphological features as well as the ratio between finger lengths II to IV (2D: 3D, 2D: 4D, 3D: 4D) of the front and rear limbs in 30 specimens of Bufo eichwaldi toads (15 male and 15 female specimens) were in northern Iran. The results showed that females had higher mean body length (SVL) than males and this difference was statistically significant (90.50 mm in males vs. 114.93 mm in females and P = 0.00). In terms of other morphological traits, the results of T-test analysis (T test for independent samples) showed that the traits of diameter between two eyes (IOD), tympanum diameter (TD), length of the humerus (LHU), forearm length (FOL) and foot length (FL) had significant differences (P ≤ 0.05) between males and females. Also, the ratio of the size of the length of the fingers and toes on the left side of the body was examined in the species studied in terms of 2D:3D, 2D:4D, 3D:4D. The results showed that males and females were significantly different in two traits including 4^th toe length (D4) and 1^st finger length (F1). In addition, in terms of 2D:4D between males (0.4628) and females (0.4853) significant difference (P = 0.041) in the second and fourth toes of the hind limbs and in terms of 3D:4D between males (0.6233) and females (0.6787), there was a significant difference (P= 0.040) in the third and fourth fingers of the hind limbs. In this study, some habitat characteristics, ecology, threats and conservation measures related to Talysh toad species were also investigated.