Westergaardodina

From Palaeos.org

Westergaardodina was a long-lived paraconodont genus found from the Middle or Late Cambrian to the Middle Ordovician. It had W- or U-shaped elements that Müller & Hinz-Schallreuter (1998) explained as growing through a combination of dorsal and/or lateral pressure being applied to points on a growing element. How the Westergaardodina elements were arranged in their original apparatus remains unknown.

Characters (from Müller & Hinz-Schallreuter 1998): Bi- or tricuspidate elements; internal cavity may be divided between lateral cavities. Lateral projection(s) (one-sided only in bicuspidate forms) resulting from combination of upward growth from base and dorsal pressure alongside/on either side of median projection causing tearing of older lamellae; lamellae-free spaces became filled by a callus-like substance. Lateral projections of elements remain flexible; probably not heavily mineralised in life.

Phylogeny

<==Westergaardodina Müller 1959 DJ71
   |  i. s.: W. mosseburgensis Müller 1959 DJ71
   |--*W. bicuspidata Müller 1959 DJ71
   `--+--W. amplicava Müller 1959 DJ71
      `--Chosonodina Müller 1964 DJ71
           |  i. s.: C. rigbyi PBJ03
           |--C. fisheri Druce & Jones 1971 DJ71
           `--+--*C. herfurthi Müller 1964 DJ71
              `--+--C. lunata Harris & Harris 1965 DJ71
                 `--Coleodus Branson & Mehl 1933 DJ71, SS05
                      `--C. simplex DJ71

* Type species of generic name indicated

References

[DJ71] Druce, E. C., & P. J. Jones. 1971. Cambro-Ordovician conodonts from the Burke River Structural Belt, Queensland. Commonwealth of Australia, Bureau of National Development, Bureau of Mineral Resources, Geology and Geophysics, Bulletin 110: 1-159.

Müller, K. J., & I. Hinz-Schallreuter. 1998. Internal structure of Cambrian conodonts. Journal of Paleontology 72 (1): 91-112.

[PBJ03] Pyle, L. J., C. R. Barnes & Z. Ji. 2003. Conodont fauna and biostratigraphy of the Outram, Skoki, and Owen Creek Formations (Lower to Middle Ordovician), Wilcox Pass, Alberta, Canada. Journal of Paleontology 77 (5): 958-976.

[SS05] Sansom, I. J., & M. P. Smith. 2005. Late Ordovician vertebrates from the Bighorn Mountains of Wyoming, USA. Palaeontology 48 (1): 31-48.

Credits

Christopher 13:17, 6 January 2011 (UTC)