Olenellus fowleri Palmer, 1998

Gapp, I. Wesley & Lieberman, Bruce S., 2014, New olenelloid trilobites from the Northwest Territories, Canada, Zootaxa 3866 (4), pp. 479-498 : 481-482

? Olenellus fowleri Palmer, 1998

Fig. 2.3

Olenellus ( Olenellus ?) fowleri Palmer, 1998 , p. 669, figs. 5.5, 10.1–10.6; see for complete synonymy.

Material examined. KUMIP 355555 likely from the Olenellus zone or Waucoban Series, Dyeran stage, sensu Webster (2011a, b) and Webster et al. (2011), early Cambrian, Sekwi Formation, Northwest Territories, Canada, but occurring from Section 2 in float.

Description. The addition of the new specimen figured here does not warrant a redescription of the species as only a partial thorax is present. At least six prothoracic segments and thirty-six opisthothoracic segments are visible in this specimen. The end of a spine found most abaxially to the right on the specimen is likely part of a macropleural T3 spine. The length of the prothoracic segments are long, some are longer than the length of the entire opisthothorax.

Discussion. Assigning this specimen to Nephrolenellus (a genus known for having greater than 22 segments in the opisthothorax) is ruled out because the prothorax pleural spines are much longer in this specimen than in species of Nephrolenellus (and have the condition typical of O. fowleri ). Also, this specimen is much larger than is common for other Nephrolenellus species, which are known for having the cephalon generally 12 mm or shorter (sag.) ( Palmer 1998). This genus is discussed in greater detail in Webster (2007).

As Palmer (1998) noted, the thorax of O. robsonensis Burling, 1916 is very similar to that of O. fowleri . The main difference that he observed in thoracic characters was a lack of granules on either pleural spines or the axial spine of T 15 in O. fowleri , and a lack of axial nodes in O. robsonensis . Unfortunately the preservation of this specimen is too poor to observe these details, especially since T15 is not visible.

However, the single specimen of O. robsonensis appears to lack the long T3 spines (see Lieberman 1999) that are present in specimens of O. fowleri . Thus, the small part of the very large spine (present in the upper right part of Fig. 2.3) that we interpret as part of T3 is evidence for questionably assigning this specimen to O. fowleri (as opposed to O. robsonensis ). Furthermore, O. fowleri probably forms a clade with several species in addition to O. robsonensis (see Palmer 1998, p. 669) and it is conceivable that the material illustrated herein could represent one of those species (M. Webster, pers. comm.).

Olenellus fowleri has been recovered previously from the Pioche Formation, Nevada ( Palmer 1957; 1998), the Grapevine Mountains, California (Palmer in Palmer & Halley 1979), and several additional localities described in Webster (2011a, b) and Webster et al. (2011).