Lobopodia

Paraphyletic group
fossil_range=Early Cambrian onwards


regnum = Animalia
superphylum = Ecdysozoa
includes =
* † Dinocarida
* † Xenusia
* Onychophora
* Tardigrada

Lobopodia is a group of poorly understood animals, which mostly fall as a stem group of arthropods. Their fossil range dates back to the Early Cambrian. Lobopods are segmented and typically bear legs with hooked claws on their ends.

The oldest near-complete fossil lobopods date to the Lower Cambrian. They resemble the modern oncyophorans (velvet worms) in their worm-like body shape and numerous stub-legs. They differ in their possession of numerous dorsal armour plates, "sclerita", which often cover the entire body and head. Since they taper off into long, pointed spikes, these probably served a role in defence against predatorsFact|date=September 2008. Individual sclerita are found among the so-called "small shelly fauna" (SSF) from the early Cambrian period.cite journal | author = Liu | year = 2007 | doi = 10.1016/j.gr.2007.10.001 | title = Origin, diversification, and relationships of Cambrian lobopods | journal = Gondwana Research | volume = 14 | pages = 277 ] The "lobopodia" group is considered to include these Cambrian forms in addition to the wict|extant onychophorans.

The better-known genera include, for example, "Aysheaia", which was discovered among the Canadian Burgess Shale and which is the most similar of the Lobopoda in appearance to the modern velvet worms; a pair of appendages on the head have been considered precursors of today's antennaeFact|date=September 2008. "Xenusion" was apparently able to roll itself up, spines outward, giving insight into the defensive strategies of the Lobopoda. However, by far the most famousFact|date=September 2008 of the lobopod genera is "Hallucigenia", named on account of its bizarre appearance. It was originally reconstructed by with long, stilt-like legs and mysterious fleshy dorsal protuberances, and was long consideredFact|date=September 2008 a prime example of the way in which nature experimented with the most diverse and bizarre body designs during the Cambrian. However, further discoveries showed that this reconstruction had placed the animal upside-down: interpreting the "stilts" as dorsal spines made it clear that the fleshy "dorsal" protuberances were actually legs. This second reconstruction also exchanged the front and rear ends of the creature, which further investigation showed to be erroneous.Fact|date=July 2008

The way of life of the Lobopoda is to a large extent unknown; some species were apparently carnivorous, feeding on other animals such as, for example, sponges (Porifera) or sea cucumbers (Holothuroidea) of the genus "Eldonia".

During the Cambrian lobopods displayed a substantial degree of biodiversity, which reduced drastically during the Ordovician.Fact|date=July 2008

The lobopods are closely related to the arthropods; indeed, the arthropods may well have arisen from within the lobopods. They are less closely to the tardigrades; precise classification is still in flux.

ee also

The name Lobopodia is also used for lobose pseudopods, found among certain amoeboids.

References