Dinomischus isolatus

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An enigmatic chalice-shaped animal

Reconstruction of Dinomischus isolatus.

Dinomischus isolatus (USNM 198735) – Holotype. Partial specimen showing calyx and internal organs, bracts and upper part of the stem. Specimen height = 18 mm. Specimen dry – polarized light (left), wet – polarized and direct light (middle and right respectively). Walcott Quarry.

Dinomischus isolatus (MCZ 1083) – Paratype. Nearly complete specimen showing the bulbous termination of the stem. Specimen height = 20 mm. Specimen wet – direct light (left), dry – polarized light (right). Walcott Quarry.

Taxonomy:

Kingdom: Animalia

Phylum: Unknown

Higher Taxonomic assignment: Non applicable

Species name: Dinomischus isolatus

Remarks:

Although it has been suggested that Dinomischus may be related to the ectoprocts (Conway Morris, 1977), its unusual morphology has not yet been conclusively related to a known phylum and as such its affinities remain unclear.

Described by: Conway Morris

Description date: 1977

Etymology:

Dinomischus – from the Greek dinos, “goblet,”, and michos, “stalk or stem.” The name refers to the wine glass-shape of the animal.

isolatus – from the Latin insula, “island.” The name refers to the non-gregarious life habit of this animal.

Type Specimens: Holotype –USNM198735 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.

Other species:

Burgess Shale and vicinity: none.

Other deposits: D. venutus Chen, Hou and Lu, 1989 from the Lower Cambrian Chengjiang fauna.

Age & Localities:

Age:

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

Principal localities:

Burgess Shale and vicinity: Walcott Quarry, Raymond Quarry, Tulip Beds (S7)

Other deposits: A single specimen of D. isolatus was also reported from the Middle Cambrian Kaili Formation (Peng et al., 2006).

History of Research:

Brief history of research:

D. isolatus was among the original fossils collected by Walcott, although it was not formally described until 1977 by Conway Morris. The original description was based on three specimens. A second species was added by Chen et al. (1989) based on material from the Chengjiang in China. Further specimens have been collected by the Royal Ontario Museum from sites on both Fossil Ridge and Mount Stephen.

Description:

Morphology:

Dinomischus consists of a cup-shaped calyx supported by a long stem that terminates in a bulbous swelling. A circle of 20 stiff bracts up to 4.5 mm in length surround the upper margin of the calyx. These point upward and project beyond the level of the anus and the mouth and are interpreted as part of a filter feeding apparatus. Reflective material in the central part of the calyx has been interpreted as a U-shaped gut, with a large sac-like stomach positioned centrally and a mouth and anus on the upper surface. The stem appears to be a rigid structure and the bulbous termination is interpreted as an attachment structure.

Abundance:

Dinomischus is very rare. Only three specimens were originally described from the Burgess Shale. A few additional specimens are known in the Burgess Shale collections of the Royal Ontario Museum.

Maximum Size:

28 mm

Ecology:

Life habits: Epibenthic, Sessile

Feeding strategies: Suspension feeder

Ecological Interpretations:

Dinomischus was a stalked filter feeder that lived anchored to the sea floor. Its ring of bracts would have captured food particles from passing water and moved them to the mouth.

References:

CONWAY MORRIS, S. 1977. A new entoproct-like organism from the Burgess Shale of British Columbia. Palaeontology, 20(4): 833-845.

CHEN, J. HOU, X. AND H. LU. 1989. Early Cambrian hock glass-like rare sea animal Dinomischus (Entoprocta) and its ecological features. Acta Palaeontologica Sinica., 28 (1): 58-71.

PENG, J., Y. L. ZHAO AND J. P. LIN. 2006. Dinomischus from the Middle Cambrian Kaili Biota, Guizhou, China. Acta Geologica Sinica-English Edition, 80: 498-501.