• Category
  • Length Range
    8.0-22.4 µm
  • Width Range
    4.7-8.4 µm
  • Striae in 10 µm
  • Synonyms
    Gomphogramma rupestre (Kütz.) Braun in Rabenh. 1853



Valves are elliptic-lanceolate, with broad, unconstricted apices. The axial area is wide and indistinct. Striae are parallel, with individual erratic striae that intrude into the axial area. Costae are primary and robust, and become inflated and relatively indistinct in axial area; 3-4 in 10 µm. A single rimoportula is present at one valve end. Girdle bands are incomplete. Septae extend approximately 1/4 of the way into the valve, and alternate orientation from one band to the next.

Recent work suggests that the name of this taxon needs to be reconsidered (Williams et al. 2021) and this page needs to be revised. Tetracyclus rupestre may a European species.


The specimens imaged for this page were collected from Nantahala River near Rainbow Springs, North Carolina. Similar to T. hinziae and T. glans (2/4 of the other extant Tetracyclus species known) populations in the Pacific Northwest, T. rupestris is found to co-occur with specific araphid taxa in the Tabellaria, Meridion, and Odontidium genera.

Original Description

  • Basionym
    Denticula thermalis var. rupestris
  • Author
    Kütz. 1849

Original Images

Tet Rupestris Orig Desc Text

Cite This Page

Bishop, I. (2016). Tetracyclus rupestris. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/tetracyclus_rupestris


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Tetracyclus rupestris from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.