The Burgess Shale

Nectocaris pteryx

3D animation of Nectocaris pteryx.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Class: Cephalopoda (stem group molluscs)
Remarks:

Nectocaris is regarded as an early stem-group mollusc close to the cephalopods. This stem-group also includes Vetustovermis from the Middle Cambrian Emu Bay Shale of Australia, and the Lower Cambrian Petalilium from the Chengjiang deposit in China (Smith and Caron, 2010).

Species name: Nectocaris pteryx
Described by: Conway Morris
Description date: 1976
Etymology:

Nectocaris – from the Greek nekto, “swimming,” and the Latin caris, “shrimp,” based on its original interpretation as an arthropod.

pteryx – from the Greek pteryx, “fins,” in reference to the presence of fins.

Type Specimens: Holotype –USNM198667 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Period:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott, Raymond and Collins Quarries on Fossil Ridge.

History of Research:

Brief history of research:

As with Odontogriphus, another Burgess Shale animal related to molluscs, Walcott collected the first specimen of Nectocaris between 1909 and 1924. The fossil was photographed by Walcott, and its print sat with the unidentified specimen in the Smithsonian collections until noticed and described by Simon Conway Morris in 1976. Due to the lateral compression of the fossil, his resulting reconstruction was laterally-oriented. The funnel, bent back over the front, resembled the head-shield of an arthropod, and yet the fin, folded along the top of the organism, looked much like the ray-bearing dorsal fin of a chordate. A chordate affinity was further suggested by the myomere-like appearance of the bars, and although Conway Morris did not offer a firm diagnosis, Simonetta (1988) promoted a chordate status (Insom et al., 1995).

Meanwhile, Glaessner had described Vetustovermis, based on an ill-preserved specimen from Australia’s Emu Bay Shale, and because of its segmented appearance he suggested an affinity with annelid worms (Glaessner, 1979). Other workers noted the similarity of some Chengjiang fossils to this specimen and described them as slug-like relatives of the molluscs (Chen et al., 2005). During this period, the Royal Ontario Museum had been collecting similar fossils, which Desmond Collins recognized as representatives of Nectocaris. These were eventually described as stem-group cephalopods (Smith and Caron, 2010). The relationships among members of this clade are difficult to determine, and it may require further fossil finds to establish their diversity and range. The absence of a shell in Nectocarisindicates that cephalopods, which were previously thought to have evolved later in the Cambrian from snail-like monoplacophorans, did not require a buoyant shell to start swimming, but derived their shell independently of other mollusc lineages.

Description:

Morphology:

The body of Nectocaris is kite-shaped and can reach up to 72 mm in length, including two flexible tentacles that extend forwards from the head, which also bears a pair of camera-type eyes on short stalks. A long, nozzle-like funnel originates under the base of the head. The main body has wide lateral fins with transverse bars; a large axial cavity contains paired gills.

Abundance:

Nectocaris is known from 90 specimens on Fossil Ridge, mostly from the Collins Quarry; it is rare or absent at most other Burgess Shale localities. Only two specimens, including the holotype, have been found in the Walcott Quarry.

Maximum Size:
72 mm

Ecology:

Ecological Interpretations:

A free-swimming predator or scavenger, Nectocaris would have fed on small prey items with its prehensile tentacles in a similar fashion to squid today. Its primary mode of propulsion would have been in the flexing of its fins; it may have supplemented this by squirting water from its funnel. The funnel was also used to inhale and exhale water, which entered the animal’s body cavity to oxygenate the large internal gills.

References:

CHEN, J.-Y., D.-Y. HUANG AND D. J. BOTTJER. 2005. An Early Cambrian problematic fossil: Vetustovermis and its possible affinities. Proceedings of the Royal Society B: Biological Sciences, 272(1576): 2003-2007.

CONWAY MORRIS, S. 1976. Nectocaris pteryx, a new organism from the Middle Cambrian Burgess Shale of British Columbia. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 12: 703-713.

GLAESSNER, M. F. 1979. Lower Cambrian Crustacea and annelid worms from Kangaroo Island, South Australia. Alcheringa, 3(1): 21-31.

INSOM, E. A. PUCCI AND A. M. SIMONETTA. 1995. Cambrian Protochordata, their origin and significance. Bollettino di Zoologia, 62(3): 243-252.

SIMONETTA, A. M. 1988. Is Nectocaris pteryx a chordate? Bollettino di Zoologia, 55(1-2): 63-68.

SMITH, M. AND J.-B. CARON. 2010. Primitive soft-bodied cephalopods from the Cambrian. Nature, 465: 469-472.

Other Links:

http://www.nature.com/nature/journal/v465/n7297/full/nature09068.html

Morania confluens

3D animation of Morania confluens (being grazed by Wiwaxia corrugata).

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Class: Cyanophyceae (Order: Nostocales?)
Remarks:

Walcott (1919) considered Morania to be related to the modern cyanobacteria Nostoc. No revisions to the affinities of this cyanobacterium have been published since.

Species name: Morania confluens
Described by: Walcott
Description date: 1919
Etymology:

Morania – from Moraine Lake (1,885 m), in Banff National Park.

confluens – from the Latin fluere, “flow or stream,” and the prefix con, “together.” The name refers to the abundance of this species.

Type Specimens: Syntypes–USNM35378-35390, 35398 (M. confluens); USMN 35391, 35392 (M. costellifera);USNM35393 (M. elongata);USNM35394 (M. fragmenta);USNM35395 – 35397, 35401 (M.? globosa);USNM57718 (M. parasitica);USNM35402 (M.? reticulata) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: M. costellifera Walcott, 1919; M. elongata Walcott, 1919; M. fragmenta Walcott, 1919; M.? globosa Walcott, 1919; M. parasitica Walcott, 1919; M.? reticulata Walcott, 1919, all from the Walcott Quarry.

Other deposits: M.? antiqua Fenton and Fenton, 1937 from the middle Proterozoic Altyn Limestone of Montana and the Little Dal Group, Mackenzie Mountains (see Hofmann and Aitken, 1979).

Age & Localities:

Period:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Walcott described Morania, erecting eight species, in a 1919 paper along with Burgess Shale algae, comparing the genus to the extant cyanobacteria Nostoc. Walcott included thin sections and details of the microstructures of M. confluens showing that it was formed of tangled strings of pyrite. Satterthwait (1976) studied specimens of M. confluens from the Geological Survey of Canada collections as part of her PhD thesis and broadly agreed with Walcott’s original interpretations, in particular regarding a position within the Nostocaceae. Sattertwhait’s work has not been published but she suggested that many species erected by Walcott might not be valid and could represent parts of more complex algae. Mankiewicz (1992) re-observed Walcott’s thin sections and confirmed the presence of Morania in several samples. Rigby (1986) identified M.? frondosa Walcott 1919, as a sponge and reassigned it to a new genus (see Crumillospongia frondosa).

Description:

Morphology:

Morania ranges in shape from spherical to sheet-like. The sheet-like form M. confluens is by far the most common species. Specimens typically range in length between 1 to more than 13 centimeters. The sheets are characteristically perforated, with holes up to 3 centimeters in diameter. The shape, size, number and distribution of holes are highly variable. Thin sections show that the microstructure of M. confluens is represented by a tangle mass of filaments called trichomes. These filaments have a beadlike structure with little spheroids of pyrite ranging 3 to 7 micrometers in diameter, and originally interpreted by Walcott as defining cellular structures.

Abundance:

Estimating the abundance of Morania is difficult since some bedding planes have large tangled masses of this cyanobacterium, and many could represent fragments of the same colony. Morania is very common in the Walcott Quarry and represents 4.9% of the community (Caron and Jackson, 2008).

Maximum Size:
130 mm

Ecology:

Ecological Interpretations:

Caron and Jackson (2006) suggested that Morania covered large areas of the benthos and might have provided a stable substrate and food source for benthic animals, in particular for a number of grazers, like Odontogriphus and Wiwaxia.

References:

CARON, J.-B. AND D. A. JACKSON. 2006. Taphonomy of the Greater Phyllopod Bed Community, Burgess Shale. Palaios, 21: 451-465.

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

HOFMANN, H. J. AND J. D. AITKEN. 1979. Precambrian biota from the Little Dal Group, Mackenzie Mountains, northwestern Canada. Canadian Journal of Earth Sciences, 16: 150-166.

MANKIEWICZ, C. 1992. Obruchevella and other microfossils in the Burgess Shale: preservation and affinity. Journal of Paleontology, 66(5): 717-729.

SATTERTHWAIT, D. F. 1976. Paleobiology and Paleoecology of Middle Cambrian Algae from Western North America. Unpublished PhD thesis, California, Los Angeles, 120 p.

WALCOTT, C. 1919. Cambrian Geology and Paleontology IV. Middle Cambrian Algae. Smithsonian Miscellaneous Collections, 67(5): 217-260.

Other Links:

None

Marrella splendens

3D animation of Marrella splendens.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Class: Marrellomorpha (Order: Marrellida, stem group arthropods)
Remarks:

The affinity of Marrella is still somewhat uncertain. It has been grouped together with the Devonian taxa Mimetaster and Vachonisia from the Hunsrück Shale to form the Class Marrellomorpha (Beurlen, 1934; Strømer, 1944), but the placement of this class in arthropod evolution is unclear. It has been suggested to be at the base of a group of Lamellipedian arthropods, including trilobites and trilobite-like taxa, (Hou and Bergström, 1997), but has also been placed in the most basal position in the upper stem lineage arthropods (Briggs and Fortey, 1989; Wills et al., 1998).

Species name: Marrella splendens
Described by: Walcott
Description date: 1912
Etymology:

Marrella – after Dr. John Marr, palaeontologist at Cambridge University and friend of Walcott.

splendens – from the Latin splendens, “beautiful, or brilliant.”

Type Specimens: Lectotype –USNM57674 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none

Other deposits: Marrella sp. from the Kaili Biota of southwest China (Zhao et al., 2003).

Age & Localities:

Period:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge. Smaller localities on Mount Field, the Tulip Beds (S7) on Mount Stephen and Mount Odaray.

History of Research:

Brief history of research:

Marrella was one of the first fossils found by Walcott, and sketches appear in his notebook as early as August 31st, 1909. Walcott informally named them “lace crabs” at the time. The next summer, on August 9, 1910, Walcott and son Stuart found the “lace crab beds” in situ, marking the discovery of the fossil-bearing beds of the Walcott Quarry of the Burgess Shale. Walcott (1912) formally described the “lace crabs” as Marrella splendens, but a reconstruction was not attempted until Raymond (1920).

Marrella was examined again by Simonetta (1962) and in a major study by Whittington (1971). New specimens collected by the Royal Ontario Museum allowed for the description of a specimen showing Marrella in the act of moulting (García-Bellido and Collins, 2004), and another re-description of the taxon (García-Bellido and Collins, 2006).

Description:

Morphology:

Marrella is a small arthropod with a wedge-shaped head shield bearing two pairs of prominent spines that project from the sides and posterodorsal margin and extend back along most of the length of the body. There is also a pair of smaller posteroventral spines. The head bears a pair of long, thin antennae with as many as 30 segments, and a pair of paddle-like appendages with six segments and numerous bushy setae along the edges.

Behind the head, the body consists of 26 segments that are small and subcircular, each bearing a pair of biramous appendages. The walking branch of this appendage has six segments, and the second branch is made of tapering gills with long, slim filaments that attach near the base of the legs. The last twelve body segments have conspicuous internal projections that form a net below the body.

The tail is minute and pointed. The stomach is located in the head near the ventral mouth, and the intestine stretches most of the length of the body. Dark stains found around the body are suggested to be the gut contents that were squeezed out during preservation. A small, triangular dorsal heart is located in the cephalic region and has arteries branching off from it.

Abundance:

Marrella is one of the most common species in the Burgess Shale. Over 25,000 specimens have been collected (García-Bellido and Collins, 2006), and it is the second most common arthropod species in Walcott Quarry, comprising 7.3% of the specimens counted (Caron and Jackson, 2008).

Maximum Size:
25 mm

Ecology:

Ecological Interpretations:

Marrella was an active swimmer that moved just above the sea floor while deposit feeding. It could rest on the sea floor by standing on its body appendages. Swimming was achieved by undulating the second pair of paddle-like appendages on the head. Its antennae would be used to sense the environment and locate food items. The net of internal projections on the last twelve body segments would have been used to trap food particles located in water currents and to pass them along the underside of the animal. Food particles trapped in the net would be moved towards the mouth using the tips of the anterior legs.

References:

BRIGGS, D. E. G. AND R. A. FORTEY. 1989. The early radiation and relationships of the major arthropod groups. Science, 246: 241-243.

BRIGGS, D. E. G., B. S. LIEBERMAN, J. R. HENDRICKS, S. L. HALGEDAHL AND R. D. JARRARD. 2008. Middle Cambrian arthropods from Utah. Journal of Paleontology, 82(2): 238-254.

BEURLEN, K. 1934. Die Pygaspiden, eine neue Crustaceen – (Entomostraceen) – Gruppe aus den Mesosaurier führenden Iraty-Scichten Brasiliens. Paläontologische Zeitschrift, 16: 122-138.

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

GARCÍA-BELLIDO, D. AND D. H. COLLINS. 2004. Moulting arthropod caught in the act. Nature, 429: 40.

GARCÍA-BELLIDO, D. AND D. H. COLLINS. 2006. A new study of Marrella splendens(Arthropoda, Marrellomorpha) from the Middle Cambrian Burgess Shale, British Columbia, Canada. Canadian Journal of Earth Sciences, 43: 721-742.

HOU, X. AND J. BERGSTRÖM. 1997. Arthropods of the Lower Cambrian Chengjiang fauna, southwest China. Fossils and Strata, 45: 1-116.

RAYMOND, P. E. 1920. The appendages, anatomy, and relationships of trilobites. Memoirs of the Connecticut Academy of Arts and Sciences, 7: 1-169.

SIMONETTA, A. M. 1962. Note sugli artropodi non trilobiti della Burgess Shale, Cambriano Medio della Columbia Britannica (Canada). 1. contributo: 2. genere Marrella Walcott, 1912. Monitore Zoologico Italiano, 69: 172-185.

STØMER, L. 1944. On the relationships and phylogeny of fossil and recent Arachnomorpha. Norsk Videnskaps-Akademi Skrifter I. Matematisk-Naturvidenskaplig Klasse, 5: 1-158.

WALCOTT, C. 1912. Cambrian geology and paleontology II. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57(6): 145-228.

WHITTINGTON, H. B. 1971. Redescription of Marrella splendens (Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia. Bulletin of the Geological Survey of Canada, 209: 1-24.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY, M. WILKINSON AND P. H. A. SNEATH. 1998. An arthropod phylogeny based on fossil and recent taxa, p. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

ZHAO, Y., J. YUAN, M. ZHU, X. YANG AND J. PENG. 2003. The occurrence of the genus Marrella (Trilobitoidea) in Asia. Progress in Natural Science, 13: 708-711.

Other Links:

http://paleobiology.si.edu/burgess/marrella.html