Unranked clade Cambroernida (stem group ambulacrarians)
Herpetogaster, together with other pedunculate or discoidal fossils such as Eldonia, probably belongs in the stem group to a clade known as the Ambulacraria, represented by both echinoderms and hemichordates (Caron et al., 2010).
Caron and Conway Morris
Herpetogaster – from the Greek, herpo, “to creep,” and gaster, “stomach.” The name refers to the creeping aspect of the animal and the large stomach.
collinsi – after Desmond Collins, a former curator of palaeontology at the Royal Ontario Museum who led expeditions to the Burgess Shale between 1975-2000.
Holotype – ROM 58051 in the Royal Ontario Museum, Toronto, Canada.
Burgess Shale and vicinity: none.
Other deposits: none.
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
The Walcott and Raymond Quarries on Fossil Ridge. The Collins Quarry on Mount Stephen and Stanley Glacier in Kootenay National Park.
Brief history of research:
Herpetogaster was described in 2010 as a possible member of the ambulacrarians (Caron and Conway Morris, 2010).
Herpetogaster consists of a main body with a pair of tentacles at the front and a flexible stolon. The body is divided into thirteen segments and coils clockwise when seen dorsally. The tentacles are long and flexible and branch several times. The stomach is the most conspicuous portion of the gut and is often preserved as a highly reflective film, as in Eldonia, a closely related form. The anus is terminal and the mouth is located between the tentacles. The stolon sometimes exceeds the length of the main body, and terminates with a flat disk. This structure was evidently used for anchoring the organism to the seabed, or to other organisms).
This animal is known from 101 specimens. Only 6 come from the Walcott Quarry, where it represents only 0.011% of the specimens counted in the community (Caron and Jackson, 2008); most specimens (68) come from the Raymond Quarry.
Suspension feeder?, carnivorous?
Specimens of Herpetogaster were found associated with the sponge Vauxia, suggesting the animal lived on or near the seabed. It is not clear if Herpetogaster was permanently anchored, and whether or not it fed only on particulate matter in the water column, or could hunt small preys using its prehensile tentacles.