Distinction from the most closely related species, Scolopendropsis bahiensis (Brandt, 1841), is most obvious from the difference in trunk segment numbers (39 or 43 in S. duplicata versus 21 or 23 in S. bahiensis). Other diagnostic characters of S. duplicata include:
- the paramedian sutures of T1 (the tergite of the maxillipede segment and first leg-bearing trunk segment) are incomplete anteriorly, extending ¾ of length
- posterior border of the coxopleuron usually bearing a single short spine caudal to the posterolateral corner of the pore field, shown above.
- ultimate leg prefemur with two ventromedial and one to three dorsomedial spines in longitudinal rows (when multiple), the dorsomedial row being aligned with the prefemoral process, the latter with two or three apical spines
- flattened medial face of prefemur of the ultimate leg variably bearing one to six small spines that, when maximally developed, are aligned in two rows
- posterior halves of ultimate leg prefemur and femur with a sulcus-like longitudinal depression on their dorsal surface
The type material of the closely allied species Scolopendropsis bahiensis (Brandt, 1841) has 23 leg-bearing trunk segments but, following its recent taxonomic revision (Schileyko, 2006), S. bahiensis has 21 segments throughout most of its geographic range, which includes southeastern, northeastern and central Brazil, in the 'cerrado' and 'caatinga' biomes as well as the Atlantic Forest.