Close look at Castracollis
deutsche Version

More samples of Rhynie chert found in the latter years with the lately discovered crustacean Castracollis [1] allow us to gather additional structural information which possibly will complement or modify the reconstruction offered in [1]. (See also Rhynie Chert News 24 .) A few polished chert slabs are presently being investigated at the university of Ulm, Germany. Castracollis is easily recognized by its moults with more than 30 segments (Fig.1). Nevertheless it seems to have been overlooked for decades. 
Castracollis moult with numerous legs
Fig.1: Castracollis moult, head and tail missing or hidden in the depth.
         Note the leg size decreasing towards the rear.
         Width of the picture 4mm.

As known from other small shrimp-like creatures, many of the segments bear legs, which come in several varieties adapted to the various purposes they are used for (Fig.2). Some are used for paddling with the aim to move the water or to propell the body, or both.
Castracollis "feet" with claws

Fig.2: Two "feet" of a paddle-shaped type of legs selected from the various leg types of Castracollis. Detail extracted from a 3D-picture by J. Haug , Ulm.

The claws at the very end of the legs in Fig.2 and the row of slender bristles attached sideways indicate a use as dual-purpose devices.

It may be irrelevant here but nevertheless interesting that Fig.1 is taken from a chert sample lacking the usual "Higher Plant" debris but harbouring the very rare "Lower Plant" Nematoplexus. (See Rhynie Chert News 29 .)

H.-J. Weiss      2009

[1]  S.R. Fayers, N.H. Trewin : A new crustacean from the Early Devonian Rhynie Chert ...
    Trans. Roy. Soc. Edinburgh, Earth Sci. 93(2003): 355-382.
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