Lobopodia

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See Lobopodia in Wikipedia, the free encyclopedia.

"Lobopodia" is a phylum that contains various caterpillar-sized marine "worms with legs" which date back to the Cambrian period. They superficially resemble both the modern-day onychophores, aka "velvet worms," and the tardigrades, aka "water bears." Scientists presume that "Lobopodia" is ancestral to both groups, and was a sister group to the Arthropoda. Some scientists hold Lobopodia to be distinct from onychophores, while others believe that both lobopods and onychophores are in the same group, while others, still, consider the lobopods were a crown-group of arthropod-like organisms, of which only the onychophores, and possibly the tardigrades, are the only suriving members.

The bodyplan of all lobopods was a long, cylindrical body that was highly muscular, with a series of long, paired uniramous legs that corresponded to a body segment. The heads of many lobopods, if not all, are ill-defined, being simply the anterior end of the body where the mouth opens up at. There may or may not be antennae. Among many lobopodians, particularly Aysheaia pendunculata, the antennae, when present, were believed to be not so much as sensory organs, like in modern-day onychophores, but more akin to legs that have been legs that were slightly modified to aid in grasping food.

Lobopods are divided into two informal groups, the "unarmored" lobopods, including Aysheaia pendunculata, Xenusion auerswaldae, Onychodictyon ferox, and Luolishania longicruris, and the "armored" lobopods, including Hallucigenia, Microdictyon sinicum, Cardiodictyon catenulum, and Paucipodia inermis. The names of the two groups are not terribly accurate, as X. auerswaldae, and L. longicruris have lightly mineralized sclerites on their backs, O. ferox has more spines than all of the armored lobopods put together, and P. inermis was wholely unarmored. The two groups are differentiated from each other in that the "unarmored" lobopods had the body terminate with a pair of legs, while in the "armored" lobopods, the body extended past the last pair of legs in a "tail" of sorts.

Links

Reconstruction of Burgess Shale and Chengjiang lobopods [1]

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