Tylenchorhynchus cylindricus
Cobb, 1913
Syn.: Tylenchus (Tylenchorhynchus) cylindricus (Cobb, 1913) Filipjev, 1934
Anguillulina cylindrica (Cobb, 1913) Thorne, 1935
Photo Gallery- Haughton Crater

Dimensions.  13 Females  L = 0.65 - 0.99 mm  a = 28 - 35  b = 4.2 - 6.0  c = 13 - 20  V = 54 - 64  Stylet 24 - 27 u long
                    7 Males  L =  0.67 - 1.00 mm  a = 30 - 40  b = 4.4 - 5.8  c = 14 - 16  T = 64 per cent  Stylet 22 - 28 u long
Female (neotype).  L = 0.81 mm  a = 34  b =  5.2  c = 17  V = 57
Body cylindrical, tapering at both ends.  Lip region hemispherical, set off from body contour by constriction, bearing 5 annules.  Labial framework moderately sclerotized.  Stylet 26 u long, with well-developed basal knobs, the anterior margins directed forward.  Orifice of dorsal esophageal gland about 2 u behind spear base.  Excretory pore opens at level of base of isthmus.  Esophageal-intestinal valve large.  Oocytes in single row except for a region of multiplication near distal end.  Spermatheca containing spermatozoa present.  Tail subcylindrical, with terminus bluntly rounded, not striated.  Length of tail 2.5 x anal body diameter.  Cuticle coarsely striated.  Lateral field with 4 incisures.  Phasmids prominent, opening slightly anterior to middle of tail.
Male. Similar to female.  Testis single.  Phasmids anterior to middle of tail.  Bursa envelops tail.  Spicules tylenchoid.  Gubernaculum straight to slightly curved, with distal end enlarged, proximal end distinctly curved or crescent-shaped.
Type host.  Soil at base of Pinus sp.
Type locality.  Cathedral City, California.

Tylenchorhynchus cylindricus can be distinguished by the hemispherical, definitely set-off lip region, bearing 5 annules, by the lateral fields with four lines, and by the subcylindrical tail without striations around the terminus.  Specimens of this species were examined from the following localities:  soil around Prunus sp. at Cathedral City, California;  soil from Arvin, Victorville, Yuma Mesa, Modesto, and Stockton, California; soil around shadscale at Mosida, Utah and soil around juniper at Duchesne, Utah.

This species was synonymized with dubius by Filipjev in 1936.  He recognized the genus Tylenchorhynchus Cobb (1913), but assumed that the type of the genus was a synonym of dubius.  During 1952 and subsequently, a large number of specimens collected in the Netherlands and in England have been examined.  In this material were large numbers of a species of Tylenchorhynchus that are without doubt dubius, since they correspond in all respects to the specimens illustrated by Goodey as this species.  In addition, with only two exceptions, the species of Tylenchorhynchus encountered in the Netherlands appear to be distinct from those so far collected in the United States.  In the author's opinion there can be no doubt that dubius of Bütschli and cylindricus of Cobb are separate and distinct species and it is therefore necessary to recognize cylindricus as the type species of the genus Tylenchorhynchus.
(Description- Allen, 1955)