Dale Russell
"M. lemonnieri" is a controversial taxon, and there is debate on whether it is a distinct species or not. In 1967, Dale Russell argued that "M. lemonnieri" and "M. conodon" are the same species and designated the former as a junior synonym per the principle of priority. In a 2000 study, Lingham-Soliar refuted this based on a comprehensive study of existing "M. lemonnieri" specimens, which was corroborated by a study on the "M. conodon" skull by Ikejiri and Lucas in 2014. In 2004, Eric Mulder, Dirk Cornelissen, and Louis Verding suggested that "M. lemonnieri" could be a juvenile form of "M. hoffmannii" based on the argument that significant differences could be explained by age-based variation. However, the need more research to confirm any hypotheses of synonymy was expressed.