Name: Sirius Passet Fm.
Location: Greenland
Age: Lower Cambrian
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Fauna and Flora

The fauna from Sirius Passet has been widely compared to that from the Burgess Shale, but the two are by no means identical. Sirius Passet is older, and provides an even earlier view of early metazoan evolution. Much of the fauna is endemic to this locality.

The fauna contains a diverse suite of arthropods (Budd, 1999), but has a notable lack of trilobite species (only two species, compared with several from the Chengjiang fauna, and 12 or so from the Burgess Shale) (Clowes, [www] 2002).

In direct contrast with the Burgess Shale, the Sirius Passet fauna contains few taxa with shelly skeletons; the trilobites, "rare hyoliths, a number of species with prominet spicules, a few small brachiopods, and no echinoderms or molluscs" (Conway Morris, 1998 pp.120-121). The total number of shelly fossils in the Burgess Shale is quite low, but the diversity among them is very high.

In addition, sponges and halkieriids are present (Budd, 1999).

Examples of some of the fossil fauna from Sirius Passet:

Figure 1: Halkieria evangelista

Halkieiriids are essentially marine slugs with a shell at both ends. They would have crawled along the sediment surface, sporting an array of armoured plates for protection. The specimen in Fig.1 is approximately 30 mm long.

Figure 2: Kerygmachela kierkegaardi

Kerygmachela was initially descibed as a lobopod. This is now disputed, and hence this taxon is still regarded as enigmatic.

Buenellus higginsi is a trilobite (Butterfield, 2002). The specimens have an obvious lack of sediment-filled guts, which suggests that they were probably carnivorous. Many of the specimens also display sub-lethal predation scars, possibly as a result of attack from anomalocarids. This indicates that trilobites were both predators and prey in this environment (Babcock, [www] 2002).

Figure 3: Laggania cambria (an anomalocarid) - specimen is approx. 50 cm long.

Since the evidence of anomalocarid predation is present, it is likely that future expeditions will recover specimens of these organisms from the Sirius Passet locality.

Figures 1, 2 and 3 are all taken, with permission, from the Palaeos webpage (see references).

  1. Sirius Passet Home
  2. Location
  3. Geological setting and age
  4. Fauna and flora
  5. Taphonomy
  6. References and links