“This is not a plant, not a sculpture. It was a live animal, with no eyes, what may or may not be a head, mostly a gaggle of limbs, armor-plated, covered in thorns, attached to a stomach.” Hell, scientists don’t know what to make of them or its relatives.
For me it’s less of a mystery, the environment spent billions of years reprocessing itself and the materials. The environment and tiny long evolving precursors and the time was ripe, and there were no predecessors, so creation was a blank slate. What else was there to do, but diversity like crazy, and then figure it out as they went along.
CCv3 said; For me it’s less of a mystery, the environment spent billions of years reprocessing itself and the materials. The environment and tiny long evolving precursors and the time was ripe, and there were no predecessors, so creation was a blank slate. What else was there to do, but diversity like crazy, and then figure it out as they went along.
Yep, just as early living organism multiplied by an exponential function, so did variety. Eventually natural selection culled out the least efficient forms and some of the most bizarre but hardy creatures survived to procreate and find a survival niche.
LopoPodia
Lopodium is the most common type found in such organisms as Amoeba proteus. Lobopods are characterized by finger-like tubular pseudopodia consisting of ecto and endoplasm. However, they have also been shown to contain actin and myosin (microfilaments) which contribute to the overall movement.
Unlike the other pseudopods, microtubules in lobopodia are poorly developed. In many amoebas, lobopodia are primarily involved in locomotion
I’m thinking you can only say that because you haven’t taken the time to familiarize yourself with the current state of understanding. Not that I’m particularly familiar with it, but I poke around enough to know they are making incredible finds and interpretations. Here’s a wee sampling:
A Tube-Dwelling Early Cambrian Lobopodian
Richard J.Howard, XianguangHou, Gregory D.Edgecombe, TobiasSalge, XiaomeiShi, XiaoyaMa
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New specimens indicate Facivermis is a tube-dwelling lobopodian
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Phylogenetic analyses place Facivermis in Luolishaniidae (total group Onychophora)
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Facivermis’ worm-like morphology resulted from adaptation to tube dwelling
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Facivermis was not intermediate between cycloneuralian worms and panarthropods
Summary
Facivermis yunnanicus [1, 2] is an enigmatic worm-like animal from the early Cambrian Chengjiang Biota of Yunnan Province, China. It is a small (<10 cm) bilaterian with five pairs of spiny anterior arms, an elongated body, and a swollen posterior end. The unusual morphology of Facivermis has prompted a history of diverse taxonomic interpretations, including among annelids [1, 3], lophophorates [4], and pentastomids [5]. However, in other studies, Facivermis is considered to be more similar to lobopodians [2, 6, 7, 8]—the fossil grade from which modern panarthropods (arthropods, onychophorans, and tardigrades) are derived. In these studies, Facivermis is thought to be intermediate between cycloneuralian worms and lobopodians.
Facivermis has therefore been suggested to represent an early endobenthic-epibenthic panarthropod transition [6] and to provide crucial insights into the origin of paired appendages [2]. However, the systematic affinity of Facivermis was poorly supported in a previous phylogeny [6], partially due to incomplete understanding of its morphology.
Therefore, the evolutionary significance of Facivermis remains unresolved. In this study, we re-examine Facivermis from new material and the holotype, leading to the discovery of several new morphological features, such as paired eyes on the head and a dwelling tube. Comprehensive phylogenetic analyses using parsimony, Bayesian inference, and maximum likelihood all support Facivermis as a luolishaniid in a derived position within the onychophoran stem group rather than as a basal panarthropod. In contrast to previous studies, we therefore conclude that Facivermis provides a rare early Cambrian example of secondary loss to accommodate a highly specialized tube-dwelling lifestyle.
Here’s a very cool story about how the march of science works with evidence driving new finds and reinterpretations of old assumptions.
Fossil Focus: Hallucigenia and the evolution of animal body plans
www_ ncbi.nlm.nih - gov/pmc/articles/PMC3735267/
Hallucigenia's onychophoran-like claws and the case for Tactopoda
Authors: Martin R. Smith and Javier Ortega-Hernandez Date: Oct. 16, 2014
From: Nature(Vol. 514, Issue 7522) Publisher: Nature Publishing Group
The Palaeozoic form-taxon Lobopodia encompasses a diverse range of soft-bodied ‘legged worms’ known from exceptional fossil deposits [1, 2, 3, 4, 5, 6, 7, 8, 9]. Although lobopodians occupy a deep phylogenetic position within Panarthropoda, a shortage of derived characters obscures their evolutionary relationships with extant phyla (Onychophora, Tardigrada and Euarthropoda) [2, 3, 5, 10, 11, 12, 13, 14, 15]. Here we describe a complex feature in the terminal claws of the mid-Cambrian lobopodian Hallucigenia sparsa–their construction from a stack of constituent elements–and demonstrate that equivalent elements make up the jaws and claws of extant Onychophora. A cladistic analysis, informed by developmental data on panarthropod head segmentation, indicates that the stacked sclerite components in these two taxa are homologous–resolving hallucigeniid lobopodians as stem-group onychophorans. The results indicate a sister-group relationship between Tardigrada and Euarthropoda, adding palaeontological support to the neurological [16, 17] and musculoskeletal [18, 19] evidence uniting these disparate clades. These findings elucidate the evolutionary transformations that gave rise to the panarthropod phyla, and expound the lobopodian-like morphology of the ancestral panarthropod.
Palaeozoic lobopodians feature prominently in discussions about the origins of crown-group panarthropods–the extant velvet worms (Onychophora), water bears (Tardigrada) and euarthropods (Euarthropoda) [5, 9, 10, 11, 20]. Although lobopodians have been regarded as onychophoran ancestors [2, 3], the presence of ‘primitive’ characters–such as a terminal radial mouth, unsclerotized annulated cuticle, a non-segmented body and terminal claws in the walking legs–suggests a deeper phylogenetic position [1, 4, 13]. Because lobopodians have few derived morphological features in common with extant panarthropod phyla, there has been much disagreement over the precise affinities of these extinct organisms and their significance for the origins of the major extant groups [5, 10, 11, 12, 14, 20, 21].
Here we describe the fine morphology of exceptionally preserved terminal claws in the Burgess Shale lobopodian H. sparsa (mid-Cambrian; Stage 5), and demonstrate a fundamentally similar construction in the claws and jaws of the extant onychophoran Euperipatoides kanangrensis. These new data clarify both the affinity of ambiguous lobopodians and the evolutionary origins of extant panarthropods. …
Mr. Martin Smith yet again:
Here we describe a complex feature in the terminal claws of the mid-Cambrian lobopodian Hallucigenia sparsa—their construction from a stack of constituent elements—and demonstrate that equivalent elements make up the jaws and claws of extant Onychophora. A cladistic analysis, informed by developmental data on panarthropod head segmentation, indicates that the stacked sclerite components in these two taxa are homologous—resolving hallucigeniid lobopodians as stem-group onychophorans. The results indicate a sister-group relationship between Tardigrada and Euarthropoda, adding palaeontological support to the neurological16,17and musculoskeletal18,19 evidence uniting these disparate clades. These findings elucidate the evolutionary transformations that gave rise to the panarthropod phyla, and expound the lobopodian-like morphology of the ancestral panarthropod.
August 2014
Hallucigenia’s onychophoran-like claws and the case for Tactopoda
The “Cambrian Explosion” refers to the appearance in the fossil record of most major animal body plans about 543 million years ago. The new fossils appear in an interval of 20 million years or less. On evolutionary time scales, 20 million years is a rapid burst that appears to be inconsistent with the gradual pace of evolutionary change. However, rapid changes like this appear at other times in the fossil record, often following times of major extinction. The Cambrian Explosion does present a number of interesting and important research questions. It does not, however, challenge the fundamental correctness of the central thesis of evolution.
The Cambrian Explosion is often posed as a challenge for evolution because the sudden burst of change in the fossil record appears to be inconsistent with the more typical gradual pace of evolutionary change. However, although different in certain ways, there are other times of very rapid evolutionary change recorded in the fossil record—often following times of major extinction. The Cambrian Explosion does present a number of challenging and important questions because it represents the time during which the main branches of the animal tree of life became established.
It does not create a challenge to the fundamental correctness of the central thesis of evolution, the descent of all living species from a common ancestor.
This important period in the history of life extended over millions of years, plenty of time for the evolution of these new body plans (phyla) to occur. Furthermore, the fossil record provides numerous examples of organisms that appear transitional between living phyla and their common ancestors. The ongoing research about the Cambrian period is an exciting opportunity to advance our understanding of how evolutionary processes work, and the environmental factors shaping them.
The major animal body plans that appeared in the Cambrian Explosion did not include the appearance of modern animal groups such as: starfish, crabs, insects, fish, lizards, birds and mammals. These animal groups all appeared at various times much later in the fossil record.3 The forms that appeared in the Cambrian Explosion were more primitive than these later groups, and many of them were soft-bodied organisms. However, they did include the basic features that define the major branches of the tree of life to which later life forms belong.
ANU’s calculations state that Dickinsonia lived 558 million years ago, some 16 million years before the Cambrian explosion is thought to have begun. This will no doubt help shape scientists’ thinking about the Ediacaran biota, which, because individual species were so difficult to classify, had left scientists scratching their heads for many years.
As the team writes in the paper, their conclusion about Dickinsonia’s age “supports the idea that the Ediacaran biota may have been a precursor to the explosion of animal forms later observed in the Cambrian, about 500 million years ago.”
What this means is that, although Dickinsonia doesn’t exist today, it is the earliest known part of the evolutionary family tree from which all animals — our unbathmat-like selves included — eventually emerged.
