Cambrian Soft Animal Survived Unchanged 200 Million Years

Posted on September 25, 2012 in Darwin and Evolution, Dating Methods, Fossils, Geology, Marine Biology

A fossil soft-bodied lobopodian has been found in Carboniferous strata in Illinois.

Lobopodians (“lobe-footed”) are soft-bodied worm-like animals with cylindrical legs that are well known from the Cambrian explosion.  The best-known fossils were from Sweden, although members have been found in the Burgess Shale in Canada.  The taxonomy of these classic Cambrian-explosion animals has been confusing; some evolutionists think they are related to modern tardigrades (water bears) or were ancestral to arthropods.  Paleontologists had thought they died out in the middle Cambrian, but now, an exquisitely-preserved fossil has been found in Carboniferous rock in Illinois.  This one is not related to onycophorans.  Current Biology reported,1

Lobopodians, a nonmonophyletic assemblage of worm-shaped soft-bodied animals most closely related to arthropods, show two major morphotypes: long-legged and short-legged forms. The morphotype with stubby, conical legs has a long evolutionary history, from the early Cambrian through the Carboniferous, including the living onychophorans and tardigrades. Species with tubular lobopods exceeding the body diameter have been reported exclusively from the Cambrian; the three-dimensionally preserved Orstenotubulus evamuellerae from the uppermost middle Cambrian “Orsten” (Sweden) is the youngest long-legged lobopodian reported thus far. Here we describe a new long-legged lobopodian, Carbotubulus waloszeki gen. et sp. nov., from Mazon Creek, Illinois, USA (∼296 million years ago). This first post-Cambrian long-legged lobopodian extends the range of this morphotype by about 200 million years. The three-dimensionally preserved specimen differs significantly from the associated short-legged form Ilyodes inopinata, of which we also present new head details. The discovery of a Carboniferous long-legged lobopodian provides a more striking example of the long-term survival of Cambrian morphotypes than, for example, the occurrence of a Burgess Shale-type biota in the Ordovician of Morocco and dampens the effect of any major extinction of taxa at the end of the middle Cambrian.

This discovery, therefore reveals several problems for evolutionary theory and the geologic time scale.  For one, these are delicate, soft-bodied animals that did just fine for 200 million years in evolutionary time, through all the twists and turns of fate that led to mass extinctions of other animals.  For another, the exquisite preservation of the fossilized details of soft tissues challenges beliefs they lasted nearly 300 million years through many other geologic and climatic upheavals.  Third, finding one of these in Illinois, when others were known from Sweden and Canada, shows a “remarkable range extension” of these small, delicate creatures that further reduces “the impact of any major turnover of taxa at the end of the middle Cambrian.”  Finally, the fossil shows virtually no evolution for 200 million years: the authors said, “the morphology has not changed in any significant aspect.”  If living tardigrades and velvet worms represent modern counterparts of lobopodia, then evolution within this phylum has been scant or non-existent for the whole duration of the fossil record from the lower Cambrian onward.

1. Haug, Mayer, Haug, Briggs, “A Carboniferous Non-Onychophoran Lobopodian Reveals Long-Term Survival of a Cambrian Morphotype,” Current Biology, Volume 22, Issue 18, 1673–1675, 09 August 2012, doi:10.1016/j.cub.2012.06.066.

Though small and delicate, lobopodians are complex organisms.  They are not mere amoebas with pseudopodia; they are multicellular animals with coordinated legs, bilateral symmetry, a gut, and behavior suited for their life.  Viewers of the documentary Darwin’s Dilemma may recall the strange-looking Hallucigenia, a long-legged lobopodian from the Burgess Shale.  This finding adds to the challenge against Darwinism that movie so effectively made.

 

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