Petalomonas quadrilineata (Penard, 1890)

Most likely ID: n.a.


Synonym: n.a.


Sampling location: Simmelried


Phylogenetic tree: Petalomonas quadrilineata



  • length 20 µm, width 10 µm, thickness 7 µm
  • broadly spindle-shaped to ellipsoidal
  • dorso-ventrally flattened
  • one flagellum
  • each two keels ventrally and dorsally
  • the keels converge anteriorly and posteriorly
  • cross shaped in apical view
Petalomonas quadrilineata

I found Petalomonas quadrilineata in 2007 in the same sample as Petalomonas mira var. bicarinata. The assignment of Petalomonas quadrilineata is really only possible by an apical view. Only in this way the cruciform cross section can be observed, which is caused by the 4 keels. Two of them run on the dorsal side and two on the ventral side. The dimensions are given by Penard with 20 X 10 µm, without naming a size range. My specimen was 27 µm long and 14 µm wide. The keels of the similar species Petalomonas alata are much higher and steeper, giving an almost X-shaped apical view, with deep depressions between the keels.


Fig. 1 a-i: Petalomonas quadrilineata. L = 27 µm, W = 14 µm. A freely swimming specimen. h, i) In apical view the  specimen is cross-shaped due to the 4 keels (each two dorsal and ventral). F = flagellum, K1 – K 4 = dorsal and ventral keels, NU = nucleus, RE = reservoir. Obj. 100 X.