Fossil Gallery

Home > Fossil Gallery > Chaunograptus

Chaunograptus scandens

A minute colonial organism with simple conical extensions

Image of Chaunograptus scandens.

Get Adobe Flash player

Chaunograptus scandens (USNM 83484) – Holotype. Several small thecae can be seen attached on either side of several stems. The filamentous structures associated with this specimen represent spicules of the sponge Leptomitus lineatus. Specimen length = 25 mm. Specimen dry – direct light (left), wet – direct light (right). Walcott Quarry.

© Smithsonian Institution – National Museum of Natural History. Photos: Jean-Bernard Caron

Media 1 of 2 for Chaunograptus scandens Photo
Media 2 of 2 for Chaunograptus scandens Photo

Taxonomy

Kingdom:

Animalia

Phylum:

Hemichordata

Class:

Graptolithina (Order: Dithecoidea, stem group hemichordates)

Affinity:

This species belong to a primitive group of graptolites called the dithecoids, a sister group to dendroids and graptoloids (Rickards and Durman, 2006).

Species name:

Chaunograptus scandens

Described by:

Ruedemann

Description date:

1931

Etymology:

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.

Type Specimens:

Holotype – UNSM 83484 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.

Other species:

Burgess Shale and vicinity: none.

Other deposits: Several species of this genus occur in the Cambrian (Rickards and Durman, 2006; Ruedemann, 1947).

Back to top

Age

Period:

Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).

Back to top

Localities

Principal localities:

The Walcott Quarry on Fossil Ridge.

Back to top

History of Research

Brief history of research:

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).

Back to top

Description

Morphology:

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.

Abundance:

About a dozen specimens are known from the Walcott Quarry, comprising only 0.021% of the specimens counted (Caron and Jackson, 2008).

Maximum size:

25 mm

Back to top

Ecology

Life habits:

Epibenthic, sessile

Feeding strategies:

Suspension feeder

Ecological Interpretations:

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).

Back to top

References

Bibliography:

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.

Other links:

None

Back to top