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Metaspriggina walcotti

A very rare eel-like chordate

Image of Metaspriggina walcotti.

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Metaspriggina walcotti (USNM 198611) – Holotype, part and counterpart. Lateral specimen showing clear myomeres; anterior to the right. Specimen length = 43 mm. Specimen dry – direct light (left column), dry – polarized light (right column). Walcott Quarry.

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

Media 1 of 2 for Metaspriggina walcotti Photo
Media 2 of 2 for Metaspriggina walcotti Photo

Taxonomy

Kingdom:

Animalia

Phylum:

Chordata

Class:

Unranked clade (stem group chordates)

Affinity:

Metaspriggina is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates (Conway Morris, 2008).

Species name:

Metaspriggina walcotti

Described by:

Simonetta and Insom

Description date:

1993

Etymology:

Metaspriggina – from the Greek meta, “in company with, or later in time,” and the morphologically similar Ediacaran organism Spriggina (which is no longer thought to be related). Spriggina honours Reg Sprigg, discoverer of the Precambrian fossils of the Ediacara Hills in Australia.

walcotti – after Charles Walcott, discoverer of the Burgess Shale.

Type Specimens:

Lectotype –USNM198612 and former holotype 198611 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.

Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

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Age

Period:

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

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Localities

Principal localities:

The Walcott Quarry on Fossil Ridge.

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History of Research

Brief history of research:

Set aside by Walcott for further study, the two known specimens of this species were briefly examined by Conway Morris (1979). Simonetta and Insom (1993) described one of the two specimens (the original holotype specimen) as a potential relative of the Ediacaran organism Spriggina, whereas the second specimen (now the lectotype) was interpreted as a potential chordate. A chordate interpretation for both specimens was proposed (Janvier, 1998; Smith et al., 2001) and a detailed redescription was eventually instigated by Conway Morris (2008) with both specimens being included in the same genus and species.

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Description

Morphology:

Metaspriggina is elongate in shape with a small anterior cranial region and a long triangular and laterally flattened trunk; there is no evidence of fins. The larger of the two known fossil specimens is around 7 cm in length. Both specimens possess numerous V-shaped or zig-zag segments interpreted as myomeres or muscle bands. A narrow central structure runs down the length of the organism and is interpreted as a gut. The front of one specimen appears to show a rudimentary cranium which is poorly preserved and seems to have lacked eyes.

Abundance:

M. walcotti is very rare in the Walcott Quarry, known from just two specimens.

Maximum size:

69 mm

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Ecology

Life habits:

Nektonic, nektobenthic, mobile

Feeding strategies:

Unknown

Ecological Interpretations:

With only two specimens, and poor preservation of the head, the diet and feeding habits of Metaspriggina remain a mystery. The rarity of fossils suggests that the animal was likely free-swimming, which is consistent with its musculature, although it is possible that it also spent some time on the sea floor.

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References

Bibliography:

CONWAY MORRIS, S. 1979. The Burgess Shale (Middle Cambrian) fauna. Annual Review of Ecology and Systematics, 10(1): 327-349.

CONWAY MORRIS, S. 2008. A redescription of a rare chordate, Metaspriggina walcotti Simonetta and Insom, from the Burgess Shale (Middle Cambrian), British Columbia, Canada. Journal of Paleontology, 82(2): 424-430.

JANVIER, P. 1998. Les vertébrés avant le Silurien. GeoBios, 30: 931-950.

SIMONETTA, A. M. AND E. INSOM. 1993. New animals from the Burgess Shale (Middle Cambrian) and their possible significance for the understanding of the Bilateria. Bolletino di Zoologia, 60(1): 97 - 107.

SMITH, M. P., I. J. SANSOM AND K. D. COCHRANE. 2001. The Cambrian origin of vertebrates, p. 67-84. In P. E. Ahlberg (ed.), Major Events in Early Vertebrate Evolution: Palaeontology, Phylogeny, Genetics and Development. Taylor and Francis, London.

Other links:

None

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