Mochlodon robustum was named by Nopcsa (1900). Its type specimen is BMNH R3392 and is a 3D body fossil. It is the type species of Zalmoxes.

It was synonymized subjectively with Mochlodon suessii by Nopcsa (1902); it was synonymized subjectively with Rhabdodon priscum by Nopcsa (1915); it was recombined as Rhabdodon robustum by Nopcsa (1915); it was synonymized subjectively with Rhabdodon suessi by Kuhn (1964); it was synonymized subjectively with Rhabdodon priscus by Brinkmann (1988), Norman and Weishampel (1990); it was recombined as Rhabdodon robustus by Le Loeuff and Buffetaut (1995), Casanovas et al. (1999), Pincemaille-Quillevere (2000), Vremir and Codrea (2002); it was recombined as Zalmoxes robustus by Weishampel et al. (2003), Norman (2004), Grigorescu (2005), Buffetaut (2005), Bojar et al. (2005), Dalla Vecchia (2006), Sachs and Hornung (2006), Hübner and Rauhut (2007), Pereda Suberbiola and Galton (2007), Pereda Suberbiola and Galton (2007), Butler et al. (2008), Galton (2009), Butler and Zhao (2009), McDonald et al. (2010), McDonald (2012), Zheng et al. (2013), Brusatte et al. (2013), Dieudonné et al. (2016), Dieudonné et al. (2016), Brusatte et al. (2017), Godefroit et al. (2017), Herne et al. (2018), Bell et al. (2018), Madzia et al. (2018), Herne et al. (2019), Ibiricu et al. (2019), Cruzado-Caballero et al. (2019), Bell et al. (2019), Párraga and Prieto-Márquez (2019), Dieudonné et al. (2020), Dalla Vecchia (2020), Pérez-Pueyo et al. (2021), Czepiński and Madzia (2025).