The Anomalocaris Homepage
last revised 28 December 2007 by S.M. Gon III
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Species Accounts III - Anomalocaris canadensis & Laggania cambria
The best known anomalocaridids are the two Burgess shale species that defined the group and its unique bauplan.

Anomalocaris canadensis #1

There are a number of complete specimens of Anomalocaris canadensis, but this is perhaps the best preserved. It shows the elongate body, narrow anterior, stalked eyes, and imbricate fantail, as well as the flexible nature of the lateral swimming lobes. Although there is no scale provided in this image, the length of the specimen is about 20 cm (<8 inches) Parts of the anterior appendages are visible, folded ventrally (right). It is also one of the few Anomalocaris specimen images that I've seen in color.

Anomalocaris canadensis #2

In this partial specimen of Anomalocaris canadensis, the large anterior appendage has been prepared out from beneath the overlying body. the tip of the other appendage shows near the diagonal break on the left, and the bottom of the circular mouth is also exposed near the top of the specimen. This was one of the specimens worked on by Whittington and Briggs that linked Whiteaves' Anomalocaris with Walcott's Peytoia with the anterior arms and mouth, respectively, of a much larger creature. 

Anomalocaris canadensis #3

This detail on the head of a specimen of Anomalocaris canadensis offers a clear impression of how narrow the head and "neck" region is just anterior to the first swimming lobes. It suggests that the animal was able to turn its head and swivel its eyes as it hunted (as depicted in Collins 1996).

Anomalocaris canadensis #4

Another image of the head of Anomalocaris canadensis also accentuates how narrow the anterior portion of the animal is. The distorted anterior swimming lobes appear at the bottom of the image, while the wide lateral reach of the anterior appendages indicate an impressive range of motion. 

My reconstruction of the dorsal view of Anomalocaris canadensis captures a number of details that are not consistently dealt with in other reconstructions. The lateral lobes are treated as ventral, rather than dorsal features. The fantail does not overlap with the last lateral swimming lobes, but treated as occupying their own segments. If the fantail fins are homologous to the lateral lobes (as suggested by Opabinia and Parapeytoia), then they should not co-occupy body segments.
Above: reconstruction of Anomalocaris canadensis (Collins 1996). Note rather massive "neck" lateral lobes rather dorsally placed, and significant overlap between rear lateral lobes and fantail.
My modification of the reconstruction offered by Collins 1996 (top) shifts the placement of the lateral swimming lobes to a more ventral position, shifts the dorsal fantail posterior of the last pair of lateral lobes, and makes the head and neck more narrow and gracile. This seems to conform more closely to the specimen images above.

Laggania cambria #1


In contrast to Anomalocaris canadensis, Laggania shows a wide, parabolic head, with eyes placed well behind the mouth and anterior appendages. Collins (1996) argues that the mouth of Laggania is more oval, with long axis oriented anterior-posterior, and with a roughly rectangular aperture. The anterior appendages, shown lying to each side of the mouth, are not as large as those of Anomalocaris canadensis, and bear long, delicate spines (visible in better-preserved specimens than this).
Laggania cambria #2
This foreshortened specimen of Laggania shows additional differences from Anomalocaris. There is no trace of a fantail, and the lateral lobes reach maximum width well behind the front half of the body. Horizontal support rods are associated with each pair of lateral lobes. Lateral lobes extend outward about 50% of body width.
---- Laggania cambria -------- Anomalocaris canadensis

Collins (1996) demonstrated well the contrast between the heads of Laggania (left) and Anomalocaris (right). Laggania's eyes do not seem as well suited for an active hunter, and its anterior appendages (Briggs' "Appendage F") bear comb-like spines that seem better suited for plankton sweeping than subduing trilobites. The mouth orientation and shape differences expoused by Collins may not be as distinctive as shown. There is variability in the mouth shape of both Laggania and Anomalocaris, and both may tend toward a circular outline.
The reconstruction of Laggania by Collins (1996) suggests that the lateral lobes were extremely flexible, rather like the swimming membrane of modern squid .or cuttlefish. This does not seem quite consistent with the fossil specimens, in which the lobes are typically preserved without much distortion, suggesting a certain amount of rigidity.

My reconstruction of the bauplan of Laggania cambria is rather similar to that of Collins, but the lateral lobes are extended outward more, and depicted as largely rigid, albeit capable of flexing and movement similar to the fins of other swimming animals. 

The bauplan of Laggania cambria suggests that it was far less acrobatic than Anomalocaris canadensis. Perhaps it cruised instead through the well-lit waters near the surface, sweeping clouds of zooplankton into its ovoid maw.

Even with semi-rigid fins, the sinusoidal swimming movements suggested by Whittington and Briggs (1985) are easily achieved. In this reconstruction, the long, comb-like bristles on the anterior appendages are not easily discerned.