In synonymy:
Platycryptus aureocomosus (Mello-Leitão, 1943, T from Naubolus) = Platycryptus magnus (G. W. Peckham & E. G. Peckham, 1894) (Galiano, 1981a: 11, sub Marpissa broadwayi)
Platycryptus broadwayi (G. W. Peckham & E. G. Peckham, 1894) = Platycryptus magnus (G. W. Peckham & E. G. Peckham, 1894) (Edwards, 2006: 210)
Platycryptus conspersus (C. L. Koch, 1846, T from Marpissa) = Platycryptus undatus (De Geer, 1778) (Peckham & Peckham, 1888: 80, sub Marptusa familiaris)
Platycryptus cunctator (Walckenaer, 1837, T from Attus) = Platycryptus undatus (De Geer, 1778) (Banks, 1901c: 183, sub Marptusa)
Platycryptus delus (Chamberlin & Ivie, 1936, T from Menemerus) = Platycryptus magnus (G. W. Peckham & E. G. Peckham, 1894) (Chickering, 1946: 44, sub Marpissa)
Platycryptus familiaris (Hentz, 1846, T from Marptusa) = Platycryptus undatus (De Geer, 1778) (Simon, 1901a: 603, sub Marpissa)
Platycryptus lentus (Walckenaer, 1837, T from Attus) = Platycryptus undatus (De Geer, 1778) (Roewer, 1955c: 1262, sub Marpissa)
Platycryptus luridus (Olivier, 1789, T from Aranea) = Platycryptus undatus (De Geer, 1778) (Bonnet, 1957: 2729, sub Marpissa)
Platycryptus milberti (Walckenaer, 1837, T from Attus) = Platycryptus undatus (De Geer, 1778) (Banks, 1901c: 183, sub Marptusa)
Platycryptus rupicola (Hentz, 1846, T from Attus) = Platycryptus undatus (De Geer, 1778) (Petrunkevitch, 1911: 671, sub Marpissa)
Platycryptus sundevalli (Blackwall, 1846, T from Salticus) = Platycryptus undatus (De Geer, 1778) (Banks, 1891b: 193, sub Marptusa familiaris)
Platycryptus varius (C. L. Koch, 1846, T from Marpissa) = Platycryptus undatus (De Geer, 1778) (Peckham & Peckham, 1888: 80, sub Marptusa familiaris)