Cyanophyceae (Order: Oscillatoriales?)
Walcott (1919) considered this species to be a cyanobacterium, but Walton suggested a relationship to red algae instead (Walton, 1923). More recent studies concurred with Walcott’s original interpretation (Conway Morris and Robison, 1988).
Marpolia – from Mount Marpole (2,997 m), a peak located near the Burgess Shale, northwest of Emerald Lake in Yoho National Park.
spissa – from the Latin spissus, “crowded,” in reference to the bush-like aspect of this cyanobacteria.
Lectotype –USNM35403 (M. spissa); holotype –USNM35412 (M. aequalis) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Burgess Shale and vicinity: M. aequalis Walcott 1919 from the Trilobite Beds on Mount Stephen (known from a single specimen).
Other deposits: Marpolia (possibly represented by different species) is common in various Cambrian exceptional fossil deposits, in particular from the Middle Cambrian Spence Shale and Wheeler Formation in Utah (Conway Morris and Robison, 1988) and the Middle Cambrian Kaili Formation in China (Yang et al., 2001).
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
The Walcott Quarry on Fossil Ridge, the Tulip Beds (S7) on Mount Stephen, and other smaller localities on Mount Field, Mount Stephen and Monarch Cirque.
Brief history of research:
Walcott described Marpolia in 1919 and named two species from the Burgess Shale, M. spissa from the Walcott Quarry and M. aequalis from the Trilobite Beds. M. spissa was compared to the modern Oscillatorialesin an unpublished thesis (Satterthwait, 1976), an interpretation followed by Conway Morris and Robison (1988) based on the study of fossil material from various Utah deposits. M. spissa is commonly found in thin sections (Mankiewicz, 1992) and can be isolated by acid maceration (Butterfield, 1990). A recent taphonomic study demonstrated that the preservation style of Marpolia is similar to other Burgess Shale organisms (Butterfield et al., 2007).
Marpolia forms dense tufts up to 5 cm in length composed of numerous filaments. Filaments tend to branch near the base of the tuft. Each filament averages about 40 microns in width. Filaments are composed of an outer sheath and one to four strands of inner cells. Each cell is about 2 microns in length. M. aequalis has a central stem and stronger branching structures than M. spissa.
Estimating the abundance of Marpolia is difficult since some bedding planes have large tangled masses of this cyanobacterium, and many could represent fragments of the same colony. M. spissa is rare and represents only 0.07% of the Walcott Quarry community (Caron and Jackson, 2008).
The absence of an attachment structure suggests that Marpolia may have been free-living, floating in large masses (i.e., planktonic). It may have attached to other floating objects as free-living cyanobacteria do today. It is also possible that the lack of attachment structure is taphonomic (a structure that is lost during deposition), due to detachment from the sediment during transport (caused by having been swept up in mud flows) prior to burial.