Stenothecoides cf. elongata ( Walcott, 1884 )

Johnston, Paul A. & Streng, Michael, 2021, Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides-new data from the middle Cambrian Burgess Shale Formation, Acta Palaeontologica Polonica 66 (4), pp. 723-751 : 741

Stenothecoides cf. elongata ( Walcott, 1884)

Fig. 7 .

Material.— Total 3 specimens (two articulated shells and one isolated valve), ( ROMIP 66248–66250 ) and more than 160 uncatalogued specimens from Locality 3, Odaray Mountain , Yoho National Park, Canada, middle Cambrian .

Description.—Specimens from Locality 3 are closely similar to S. elongata in shell outline ( Fig. 10 ) but are much smaller than the largest of the Utah specimens ( Fig. 9 ) and so may represent juveniles or a separate species. Most specimens are articulated and show valve inequality varies from moderate ( Fig. 7A ) to scarcely detectable. None show any radial fabric but may be too coarsely silicified to retain such details. Auricles in the few isolated valves recovered seem less well developed than is typical for S. elongata .

Figures

Fig. 7. SEM micrographs of stenothecoid pan-brachiopod Stenothecoides cf. elongata, middle Cambrian, Burgess Shale Formation, Kootenay National Park, Canada, Locality 3. A. ROMIP 66248, articulated shell in right lateral view.B. ROMIP 66249, articulated shell in left lateral (B1) and posterior (B2)

Fig. 10. Shell outlines of species discussed herein.

Fig. 9. Bivariate plots of length and width and best fit lines of Stenothecoides rasettii sp. nov., Burgess Shale Formation, Locality 2 (tectonic strain is evident in some specimens at Locality 1, which are excluded from this plot); Stenothecoides elongata (Walcott, 1884), Wheeler Formation, Drum Mountains, Utah, USA, Locality 8 of Robison (1964); Stenothecoides cf. elongata, Burgess Shale Formation, Locality 3; Stenothecoides cf. elongata, Mount Whyte Formation, Ross Lake, Mount Stephen, and Mount Field, Yoho National Park, Canada (Rasetti 1954, 1957).