This species belong to a primitive group of graptolites called the dithecoids, a sister group to dendroids and graptoloids (Rickards and Durman, 2006).
Chaunograptus – from the Greek chaunos, “loose,” and graptos, “inscribed,” in reference to the general outline of the animal.
scandens – from the Latin scandens, “to climb,” in reference to the presence of this species on the surface of sponges.
Burgess Shale and vicinity: none.
Other deposits: Several species of this genus occur in the Cambrian (Rickards and Durman, 2006; Ruedemann, 1947).
The Walcott Quarry on Fossil Ridge.
Described by Ruedemann in 1931, Chaunograptus was originally interpreted as a hydroid (which is now considered an obsolete group) within the Class Hydrozoa (see also Ruedemann, 1947). The hydrozoans include jellyfish and corals today. Graptolites are now convincingly interpreted as a primitive group of pterobranchs within Hemichordates (see references in Urbanek, 1986).
Chaunograptus scandens is a small colonial organism comprised of several very slender and straight stems that branch near the base. Short conical structures (thecae) are attached to either side of each stem at regular intervals.
About a dozen specimens are known from the Walcott Quarry, comprising only 0.021% of the specimens counted (Caron and Jackson, 2008).
Like modern rhabdopleurid forms, Chaunograptus was probably attached to substrates in order to filter the water for particulate organic matter. The original description suggests that Chaunograptus might have been climbing on the sponge Leptomitus lineata (“Tuponia lineata” in Ruedemann, 1931).
CARON, J.-B. AND D. A. Jackson, 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.
RICKARDS, R. B. AND P. N. DURMAN, 2006. Evolution of the earliest graptolites and other hemichordates, p. 5-92. In M. G. Bassett and V. K. Deisler (eds.), Studies in Palaeozoic Palaeontology. National Museum of Wales Geological Series 25. National Museum of Wales, Cardiff.
RUEDEMANN, R. 1931. Some new Middle Cambrian fossils from British Columbia. Proceedings of the United States National Museum, 79: 1-25.
RUEDEMANN, R. 1947. Graptolites of North America. Geological Society of America Memoir, 19: 652.
URBANEK, A. 1986. The enigma of graptolite ancestry: lesson from a phylogenetic debate, p. 184-226. In A. Hoffman and M. H. Nitecki (eds.), Problematic Fossil Taxa (Oxford Monographs on Geology and Geophysics N°5). Oxford University Press and Clarendon Press, Oxford.