The Burgess Shale

Yuknessia simplex

3D animation of Yuknessia simplex.
© Phlesch Bubble

Taxonomy:

Class: Non applicable
Remarks:

Walcott (1919) considered Yuknessia as a green alga, a view shared by Conway Morris and Robison (1988). However, no revision of the type material from the Burgess Shale has been published since its original description and its affinities remain uncertain.

Species name: Yuknessia simplex
Described by: Walcott
Description date: 1919
Etymology:

Yuknessia – from Yukness Mountain (2,847m), a Peak in Yoho National Park, east of the Burgess Shale.

simplex – from the Latin simplex, meaning “simple,” in reference to the simple morphology of this alga.

Type Specimens: Holotype –USNM35406 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none

Other deposits: Yuknessia sp. from the Lower Cambrian Niutitan Formation in China (Yang et al., 2003).

Age & Localities:

Period:
Middle Cambrian, Bathyuriscus-Elrathina Zone to Ptychagnostus punctuosus Zone (approximately 505 million years ago).
Principal localities:

Burgess Shale and vicinity: The Walcott Quarry on Fossil Ridge and the Trilobite Beds on Mount Stephen.

Other deposits: Y. simplex is known from the Middle Cambrian Spence Shale and the Marjum and Wheeler Formations in Utah (Conway Morris and Robison, 1988).

History of Research:

Brief history of research:

This genus was described by Charles Walcott (1919) as a possible green alga. However, like all the algae from the Burgess Shale, it awaits a modern redescription (see Dalyia). Conway Morris and Robison (1988) described specimens of this species from several Utah deposits.

Description:

Morphology:

This alga has long branches emerging from a short but wide hollow stem covered of small conical elements or plates. The plates were the attachment sites of the branches. The branches show strong similarities with Dalyia and suggest the two species might be synonymous, with Yuknessia representing the main stem structure of the Dalyia branches.

Abundance:

Yuknessia is very rare and represents only 0.04% of the Walcott Quarry community (Caron and Jackson, 2008).

Maximum Size:
30 mm

Ecology:

Ecological Interpretations:

The wide stem suggests this species was attached to the sea floor within the photic zone rather than being free floating.

References:

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

CONWAY MORRIS, S. AND R. A. ROBISON. 1988. More soft-bodied animals from the Middle Cambrian of Utah and British Columbia. University of Kansas Paleontological Contributions, 122 p.

WALCOTT, C. 1919. Cambrian Geology and Paleontology IV. Middle Cambrian Algae. Smithsonian Miscellaneous Collections, 67(5): 217-260.

YANG, R., W. ZHANG, L. JIANG AND H. GAO. 2003. Chengjiang biota from the Lower Cambrian Niutitang Formation, Zunyi County, Guizhou Province, China. Acta Palaeontologica Sinica, 77: 145-150.

Other Links:

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Margaretia dorus

3D animation of Margaretia dorus.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Class: Bryopsidophyceae (Order: Bryopsidales)
Remarks:

Walcott (1919) considered this species to be a green alga, but also noted some similarities with alcyonarian corals (closely related to the sea pens). Studies of specimens from the Burgess Shale and Utah suggest affinities with the modern green alga Caulerpa(Satterthwait, 1976; Conway Morris and Robison, 1988).

Species name: Margaretia dorus
Described by: Walcott
Description date: 1931
Etymology:

Margaretia – unspecified; possibly from the Greek margarites, “pearl,” in reference to the rounded structures present along the tegument.

dorus – unspecified; possibly from the Greek dora, “skin,” in reference to the skin-like tegument of this algae.

Type Specimens: Holotype –USNM83922 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: M. chamblessi from the Lower Cambrian Latham Shale of southeastern California (Waggoner and Hagadorn, 2004).

Age & Localities:

Period:
Upper Lower Cambrian, Olenellus Zone to the upper Middle Cambrian, Ptychagnostus punctuosus Zone.
Principal localities:

Burgess Shale and vicinity: The Walcott, Raymond and Collins Quarries on Fossil Ridge. The Trilobite Beds, Collins Quarry and smaller sites on Mount Stephen. Mount Odaray and Stanley Glacier.

Other deposits: M. dorus is known from several Cambrian deposits in particular from the Middle Cambrian Spence Shale and Marjum Formation in Utah (Conway Morris and Robison, 1988).

History of Research:

Brief history of research:

Walcott collected about 70 specimens of this new species from the Burgess Shale. It is only after his death that this material was formally published by his assistant Charles Resser in 1931. This species was compared to the modern green alga Caulerpa in an unpublished thesis (Satterthwait, 1976) an interpretation followed by Conway Morris and Robison (1988) based on the study of well preserved material from several Utah deposits. No revisions of this alga using specimens from the Burgess Shale have been published since its original description by Walcott (1931).

Description:

Morphology:

This alga is the largest known in the Burgess Shale. It is composed of single or dichotomous (divided into two) tubular axes which are erect and are connected perpendicularly to simple root-like elements called rhizomes. The tubular axes do not vary in width and can reach at least 40 cm in length. The distal ends were rounded. The surfaces are covered with small protuberances of similar size and shape called papillae. These papillae are organized in a spiral pattern. Papillae are visible along the margins of the fossils, but when preserved perpendicularly, they tend to split off at their base giving the impression of holes along the stems. Contrary to Walcott’s initial assessment, Margaretia is not a “thin membranous perforated sheet.” The rhizomes are usually smaller in diameter than the stems and tend to have irregular undulations but no papillae.

Abundance:

Margaretia is present in many sites but is usually rare. No specimens of this alga were found in the Walcott Quarry community out of 52,620 specimen observed (Caron and Jackson, 2008).

Maximum Size:
400 mm

Ecology:

Ecological Interpretations:

Margaretia lived attached to the sea floor via its rhizomes, with its fronds floating above it in the water. The presence of mostly fragmentary specimens in many fossil deposits suggests this alga could have been transported from nearby environments.

References:

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

CONWAY MORRIS, S. AND R. A. ROBISON. 1988. More soft-bodied animals from the Middle Cambrian of Utah and British Columbia. University of Kansas Paleontological Contributions, 122 p.

SATTERTHWAIT, D. F. 1976. Paleobiology and Paleoecology of Middle Cambrian Algae from Western North America. Unpublished PhD thesis, California, Los Angeles, 120 p.

WAGGONER, B. AND J. W. HAGADORN. 2004. An unmineralized alga from the Lower Cambrian of California, USA. Neus Jahrbuch fur Geologie und Palaontologie-Abhandlungen, 231: 67-83.

WALCOTT, C. D. 1931. Addenda to descriptions of Burgess Shale fossils. Smithsonian Miscellaneous Collections, 85: 1-46.

Other Links:

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