Dalyia racemata

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A presumed red alga with long slender stems

Sketch of Dalyia racemata.

Dalyia racemata (USNM 35421) – Syntype. Slab showing multiple branches and details of the top left section. Length of slab = 146 mm. Specimen dry – direct light (left), wet – direct light (right). Walcott Quarry.

Taxonomy:

Kingdom: Plantae

Phylum: Rhodophyta

Class: Non applicable

Species name: Dalyia racemata

Remarks:

No revisions of the affinities of this alga have been published since its original description.

Described by: Walcott

Description date: 1919

Etymology:

Dalyia from Mount Daly (3,152 m), a mountain northeast of Fossil Ridge, just at the border between British Columbia and Alberta. The name was originally given by mountaineer Professor Charles E. Fay to honour Judge Charles P. Daly (1816-1899), president of the American Geographical Society (1864-1899).

racemata – from the Latin racemus, “the stalk of a cluster,” referring to the shape of the alga.

Type Specimens: Syntypes –USNM35415-35418 (D. racemata); Holotype –USNM35414 (D. nitens) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.

Other species:

Burgess Shale and vicinity: Dalyia nitens Walcott 1919 from the Walcott Quarry.

Other deposits: none.

Age & Localities:

Period:

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

Principal localities:

The Walcott Quarry on Fossil Ridge and the Trilobite Beds on Mount Stephen.

History of Research:

Brief history of research:

Walcott (1919) described D. racemata and D. nitens, but the latter was based on only one specimen and may not be a separate species. The validity of this genus is also questionable and it is likely that Dalyia represents only the distal branches of Yuknessia. Walcott’s proposed affinity of Dalyia with the rhodophytes (red algae) was briefly questioned in an unpublished thesis (Satterthwait, 1976). However, the relationships of all Burgess Shale algae await thorough restudy and redescription.

Description:

Morphology:

This form is composed of a central axis, from which emerge almost perpendicular, slender, straight branching stems that terminate in whorls of short branchlets, not exceeding five in number. The surface of the stems is generally smooth, but transverse lines in some specimens give a jointed appearance, which Walcott likened to the modern rhodophyte Halurus equisetifolius. The central axes are 0.4 to 0.6 cm in diameter and the largest specimens found reach up to 4 cm in height.

Abundance:

Dalyia is very rare and represents only 0.07% of the Walcott Quarry community (Caron and Jackson, 2008).

Maximum Size:

40 mm

Ecology:

Life habits: Epibenthic, Sessile

Feeding strategies: Primary producer

Ecological Interpretations:

The mode of life of this alga is uncertain. Its rigidity suggests it was attached to the sea floor within the photic zone, rather than 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.