The proposed Ecydsozoa superphylum includes arachnids. 2017). Major efforts should be directed toward resolving the Cycloneuralia and Scalidophora questions that presently render the deep splits in Ecdysozoa ambiguous, but also toward more refined analytical treatment of data, including improved models of evolution. Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein, Assessing the root of bilaterian animals with scalable phylogenomic methods, Palaeoscolecid worms may be nematomorphs rather than annelids, Rare coding sequence changes are consistent with Ecdysozoa, not Coelomata, Gene expression suggests conserved aspects of Hox gene regulation in arthropods and provides additional support for monophyletic Myriapoda, Aspects of dorso-ventral and proximo-distal limb patterning in onychophorans, Occurrence of -chitin in the cuticle of a pentastomid, Deep metazoan phylogeny: the backbone of the tree of life, Phylogenomics of Lophotrochozoa with consideration of systematic error, No evidence for extensive horizontal gene transfer in the genome of the tardigrade, Loricifera, a new phylum with Aschelminthes characters from meiobenthos, Microscopic anatomy of invertebrates, Vol. Ancient myriapods (or myriapod-like arthropods) from the Silurian to the Devonian grew up to 10 feet in length (three meters). 2017). In some cases, such as lobsters, the amount of calcium salt deposited within the chitin is extreme. In addition, the cuticle of Pentastomida, which are bona fide members of the crustaceanhexapod clade, Tetraconata or Pancrustacea (Abele etal. (A and B) Wronascolex antiquus, a palaeoscolecid worm from the early Cambrian Emu Bay Shale, Australia; (A) mostly complete specimen, scale 1cm; (B) paired terminal hooks, scale 2mm; (C) Gamascolex vanroyi, a palaeoscolecid from the Late Ordovician of Morocco. 2010; Popova etal. Along with the Spiralia (e.g. The Ecdysozoa are all protostomes, one of the two major groups of animals, the other being deuterostomes. Nonetheless, the number of terrestrial species in this subphylum is relatively low. Evidence for a clade of nematodes, arthropods and other moulting animals. bodies. 2015 for a recent cladistic analysis), mostly due to similarities in the ganglionar peripheral nervous system (Mayer etal. The book lungs of arachnids (scorpions, spiders, ticks, and mites) contain a vertical stack of hemocoel wall tissue that somewhat resembles the pages of a book. You'll get a detailed solution from a subject matter expert that helps you learn core concepts. The procuticle is not only flexible and lightweight, but also provides protection against dehydration and other biological and physical stresses. Pisani D, Carton R, Campbell LI, Akanni WA, Mulville E, Rota-Stabelli O. Popova OV, Mikhailov KV, Nikitin MA, Logacheva MD, Penin AA, Muntyan MS, Kedrova OS, Petrov NB, Panchin YV, Aleoshin VV. Both the molecular and fossil records indicate that Ecdysozoa is an ancient group originating in the terminal Proterozoic, and exceptional fossil biotas show their dominance and diversity at the beginning of the Phanerozoic. [29], Before Aguinaldo's Ecdysozoa proposal, one of the prevailing theories for the evolution of the bilateral animals was based on the morphology of their body cavities. That is, although their introvert morphology may attest to cycloneuralian affinities, this may simply be a plesiomorphic character for Ecdysozoa. Meaning of ecdysozoan. Created by LLKD Terms in this set (55) Fungal digestion _____. Burgess Shale-type compression fossils (Fig. Saccorhytus is different from any known bilaterians in general morphology and body plan, but the research team have been able to find four key characteristics that help address the affinity of. What is the synapomorphy of the Ecdysozoa + Lophotrochozoa clade? Three referees are acknowledged for their valuable comments. Some of these characters, especially the annulated cuticle and the terminal mouth are prevalent in many Cambrian fossils, including stem-group arthropods such as Kerygmachela (see Budd 1998), possible stem-group onychophorans such as Collinsium (see Yang etal. A cladistic analysis of pseudocoelomate (aschelminth) morphology. Symphyla are similar to centipedes, but lack the poison claws and are vegetarian. This process of molting is called ecdysis, and gives the group its name. Molecular analyses occasionally fell victim to common biases, and placed additional taxa within Ecdysozoa, notably the unstable Chaetognatha (e.g., Zrzav etal. Ecdysozoan genomics got an early start, as the nematode Caenorhabditis elegans was the first published animal genome (C._elegans_Sequencing_Consortium 1998), to be followed by that of Drosophila melanogaster (Adams etal. C. Mingorance Rodrguez; credit c: modification of work by B. Kimmel based on original work by Ernst Haeckel). Crustaceans may also be cannibalistic when extremely high populations of these organisms are present. The exoskeleton is very protective (it is sometimes difficult to squish a big beetle! 2015), to be almost immediately refuted (Koutsovoulos etal. Background Ecdysozoa are the moulting protostomes, including arthropods, tardigrades, and nematodes. Clearly, further resolution of ecdysozoan relationships is needed, as genomic and transcriptomic resources are still limited for Loricifera, Kinorhyncha, Priapulida, and Nematomorpha. Little is known about kinorhynch nuclear genomes, with no size estimate or sequence currently available. Scanning electron micrograph showing rows of plates on the cuticular annulations, scale 0. The name Ecdysozoa refers to the fact that many members of this group regularly shed their cuticle, a process called ecdysis that is controlled hormonally by a class of steroids appropriately called ecdysteroids. Respiratory systems vary depending on the group of arthropod. 2013; Borner etal. Aguinaldo AMA, Turbeville JM, Lindford LS, Rivera MC, Garey JR, Raff RA, Lake JA. Drag any of the characteristics that may be found in either the ecdysozoan or lophotrochozoan phyla . These animals bear one pair of legs per segment, mandibles as mouthparts, and are somewhat dorsoventrally flattened. available to them. 2007), but that hypothesis was soon refuted with improved evolutionary models (Lartillot etal. Expert Answer Ecdysozoan Characteristics Nematoda Chelicerata Arthropoda Crustacea Hexapoda Symmetry Head of a nematode exhibits radial symmetry while the body is bilaterally symmetrical while cut (lengthwise) in half it will produce mirror image of the ot View the full answer Transcribed image text: Currently, we describe various arthropods as having uniramous or biramous appendages, but these are descriptive only, and do not necessarily reflect evolutionary relationships other than that all jointed legs of arthropods share common ancestry. This allows both sides of the tissue to be in contact with the air at all times, greatly increasing the efficiency of gas exchange. American Zoology 38(6): 907-917. The Ecdysozoa comprise one of the major groups within the
from the final adult and even live in a completely different environment. 2016; Kocot etal. 2013; Lozano-Fernandez etal. The monophyly versus paraphyly of Cycloneuralia (discussed below) is central to the interpretation of whether a collar-shaped or dorsal ganglionar brain is plesiomorphic for Ecdysozoa. For example, in the pterygotes (winged insects), in addition to a pair of jointed legs on all three segments comprising the thoraxprothorax, mesothorax, and metathoraxthere are veined wings on the mesothorax and metathorax. eggs as they are released. The book gills of (b) horseshoe crabs are similar to book lungs but are external so that gas exchange can occur with the surrounding water. Summary of selected ecdysozoan phylogenies from (A) Nielsen (2012); and other less resolved versions presented in recent textbooks and reviews: (B) Dunn etal. 4: Aschelminthes. Selection of of metazoan phylogenies based on analysis of: (E) EST data (Campbell etal. There were three types, or grades of organization: the Acoelomata (no coelom), the Pseudocoelomata (partial coelom), and the Eucoelomata (true coelom). The phylogeny above is based on a combination of morphology and 18S RNA;
According to these authors, the ancestral nervous system of the Ecdysozoa might have comprised an unpaired ventral nerve cord (seen in Priapulida, Kinorhyncha, Nematoda, and Nematomorpha), but the architecture of the brain in the ancestral ecdysozoan remains unclear. Jointed arthropod appendages, often in segmental pairs, have been specialized for various functions: sensing their environment (antennae), capturing and manipulating food (mandibles and maxillae), as well as for walking, jumping, digging, and swimming. It protects the cephalothorax. The name Ecdysozoa stems etymologically from Ancient Greek (kdusis)'shedding', and (zion)'animal'. A. Ecdysozoans are most known for their cuticle, a thick yet flexible exoskeleton that shields these creatures from predators, water loss, and other elements of their environment. 2015), and EST libraries (Dunn etal. 2016). Definition of ecdysozoa in the Definitions.net dictionary. In the arthropod body, a central cavity, called the hemocoel (or blood cavity), is present, and the hemocoel fluids are moved by contraction of regions of the tubular dorsal blood vessel called "hearts." 2D). Schmidt-Rhaesa A, Bartolomaeus T, Lemburg C, Ehlers U, Garey JR. Schokraie E, Hotz-Wagenblatt A, Warnken U, Mali B, Frohme M, Frster F, Dandekar T, Hengherr S, Schill RO, Schnlzer M. Schwentner M, Combosch DJ, Nelson JP, Giribet G. Sharma PP, Kaluziak S, Prez-Porro AR, Gonzlez VL, Hormiga G, Wheeler WC, Giribet G. Simion P, Philippe H, Baurain D, Jager M, Richter DJ, Di Franco A, Roure B, Satoh N, Queinnec E, Ereskovsky A, et al. [16][17][18][19][20][21] It is indicated when approximately clades radiated into newer clades in millions of years ago (Mya); dashed lines show especially uncertain placements. Further use of nearly complete 28S and 18S rRNA genes to classify Ecdysozoa: 37 more arthropods and a kinorhynch, The comparison of -thymosin homologues among Metazoa supports an arthropod-nematode clade, Assessing segmental versus non-segmental features in the ventral nervous system of onychophorans (velvet worms), Neuronal tracing of oral nerves in a velvet wormimplications for the evolution of the ecdysozoan brain, The larval nervous system of the penis worm, Origin and differentiation of nephridia in the Onychophora provide no support for the Articulata, Selective neuronal staining in tardigrades and onychophorans provides insights into the evolution of segmental ganglia in panarthropods, A revision of brain composition in Onychophora (velvet worms) suggests that the tritocerebrum evolved in arthropods, Introduction: the evolution of segmentation, Phylogenomics resolves the timing and pattern of insect evolution, Proposing a solution to the Articulata-Ecdysozoa controversy, Animal evolution: interrelationships of the living phyla, Phylotranscriptomics to bring the understudied into the fold: monophyletic Ostracoda, fossil placement, and pancrustacean phylogeny, Making sense of lower and upper stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848, Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda, Bilaterian phylogeny: a broad sampling of 13 nuclear genes provides a new Lophotrochozoa phylogeny and supports a paraphyletic basal Acoelomorpha, First molecular data on the phylum Loricifera an investigation into the phylogeny of Ecdysozoa with emphasis on the positions of Loricifera and Priapulida, Phylogeny of molting protostomes (Ecdysozoa) as inferred from 18S and 28S rRNA gene sequences, The Opisthokonta and the Ecdysozoa may not be clades: stronger support for the grouping of plant and animal than for animal and fungi and stronger support for the Coelomata than Ecdysozoa, Multigene analyses of bilaterian animals corroborate the monophyly of Ecdysozoa, Lophotrochozoa and Protostomia, The clade Ecdysozoa, perplexities and questions, Animal Earth: the amazing diversity of living creatures, Arthropod biology and evolution: molecules, development, morphology, The complete mitochondrial genome of the onychophoran, Biology of the integument, Vol. Dunn CW, Giribet G, Edgecombe GD, Hejnol A. Dunn CW, Hejnol A, Matus DQ, Pang K, Browne WE, Smith SA, Seaver E, Rouse GW, Obst M, Edgecombe GD, et al. 2011). Other ecdysozoan phyla could be valuable models to study the evolution of development, . The Author 2017. Twenty years after its proposal, the monophyly of molting protostomesEcdysozoais a well-corroborated hypothesis, but the interrelationships of its major subclades are more ambiguous than is commonly appreciated. Answer: Ecdysozoa is a group of protostome animals including Arthropoda, Nematoda and several smaller phyla and includes all animals which grow by the process of ecdysis ( moulting their exoskeleton through their lifetime many times over) . These are identified based on their fossils; they were quite diverse and radiated significantly into thousands of species before their complete extinction at the end of the Permian about 240 million years ago (Figure 28.36). For example, a radial mouth composed of overlapping plates and radially aranged, scalid-like pharyngeal teeth in such giant stem-group arthropods as the early Cambrian Pambdelurion are interpreted as plesiomorphies shared by Panarthropoda and cycloneuralians, and thus characters of the Ecdysozoa as a whole (Edgecombe 2009; Vinther etal. Misof B, Liu S, Meusemann K, Peters RS, Donath A, Mayer C, Frandsen PB, Ware J, Flouri T, Beutel RG, et al. Tardigrades have been placed in Panarthropoda using a plethora of morphological characters, as well as in several molecular analyses designed to counter long branch attraction, and based on a novel microRNA (Campbell etal. Even defining panarthropods morphologically is less straightforward than it might appear, as most characters typically used in textbooks are absent in one of the three phyla. Virtually all subsequent phylogenomic analyses have found support for Ecdysozoa (e.g., Philippe etal. 2016). a) takes place inside a stomach-like structure b) is extracellular, meaning that it takes place outside the organism c) takes place inside a food vacuole d) does not occur, as fungi do not digest nutrients b All fungi are _____. molluscs, flatworms and annelids) and the Deuterostomia (e.g. Members of this subphylum have an open circulatory system with a heart that pumps blood into the hemocoel. picture of ecdysozoan relationships may change. It has a carapace around the cephalothorax and the heart in the dorsal thorax area. 2B) had been cited as a character indicating affinities to Nematomorpha (Hou and Bergstrm 1994), and a system of large, helically wound cross-wise fibers in the innermost layer of the cuticle is also comparable to nematoids (Harvey etal. 2015, 2018; Shao et al. This subphylum includes animals such as horseshoe crabs, sea spiders, spiders, mites, ticks, scorpions, whip scorpions, and harvestmen. Ecdysozoa, as understood nowadays (see different configurations in Fig. by simply releasing mass quantities of egg and sperm cells into the water
a) decomposers b) flagellated c) heterotrophic There are well over a million arthropod species described, and systematists believe that there are millions of species awaiting proper classification. This means that the skeleton can be
in 2008 suggested that the tardigrada could be grouped along with the nematodes, leaving Onychophora as the sister group to the arthropods. Chelicerates are dioecious, meaning that the sexes are separate. successful fertilization, and has evolved independently in the
Tardigrades share many characteristics with C. elegans and Drosophila that could make them useful laboratory models, but long-term culturing of tardigrades historically has been a challenge, and there have been few studies of tardigrade development. Boothby TC, Tenlen JR, Smith FW, Wang JR, Patanella KA, Osborne Nishimura E, Tintori SC, Li Q, Jones CD, Yandell M, et al. The Burgess Shale species Ottoia prolifica, for example, is known from thousands of specimens that permit details of the eversion of the introvert to be documented (Fig. Variations in wing, leg, and mouthpart morphology all contribute to the enormous variety seen in the insects. 2016). 2010), a group of often large-bodied worms that have a high preservation potential because of their robust, annulated cuticle (Fig. In turn, the Protostomia belongs to
One of the characteristics often cited for Ecdysozoa is the presence of -chitin in their cuticle, but to date this has only been found in Priapulida and Panarthropoda (Greven etal. At first, this seems to be a dangerous method of growth, because while the new exoskeleton is hardening, the animal is vulnerable to predation; however, molting and ecdysis also allow for growth and change in morphology, as well as for great diversification in size, simply because the numbers of molts can be modified through evolution. Despite the vast genomic resources available for many members of Ecdysozoa, relationships within its constituent clade remain in flux (Fig. The bright side is that we have yet to test their relationships with improved taxon sampling and modern molecular (genomic/transcriptomic) data, and the constant discovery of new fossils (e.g., Harvey and Butterfield 2017) will continue to contribute toward a better understanding of the stems leading to the major ecdysozoan clades (see Edgecombe 2017). 2014), and Arthropoda is likewise represented in the early Cambrian (ca 519Ma) by crown-group taxa (Edgecombe 2017). then you must include on every physical page the following attribution: If you are redistributing all or part of this book in a digital format, c. Mammal. 2. 2014). Information and translations of ecdysozoan in the most comprehensive dictionary definitions resource on the web. The first two are commonly grouped together as Cycloneuralia (Fig. 2016). Question: Describe the major characteristics that differentiate the Ecdysozoa and the Lophotrochozoa. Allgemeine Grundzge der Organischen formen-wissenschaft, mechanisch begrndet durch die von Charles Darwin reformirte descendenztheorie, 2 vols. 1), to the point that many authors use some ecdysozoan clades as bona fide, even though no molecular support for them exists, thus relying on morphological hypotheses. Image courtesy of Tom Harvey and Nick Butterfield; (F) Ottoia prolifica, a cycloneuralian from the Burgess Shale, Canada, scale 5mm. 2012). The Ecdysozoa include the following phyla: Arthropoda, Onychophora, Tardigrada, Kinorhyncha, Priapulida, Loricifera, Nematoda, and Nematomorpha. T, circled) are well developed in the scorpion. Garey, James R. & Andreas Schmidt-Rhaesa, 1998. We should note here that chelicerae are actually modified legs, but they are not the exact serial equivalent of mandibles, which are the modified leglike chewing mouthparts of insects and crustaceans: The chelicerae are borne on the first segment making up the prosoma, whereas the mandibles are embryonically on the fourth segment of the mandibulate head. Danovaro R, Gambi C, Dell'Anno A, Corinaldesi C, Pusceddu A, Neves RC, Kristensen RM. Some of the proposed cuticular characters include its trilayered ultrastructure and the formation of the epicuticle from the tips of epidermal microvilli, annulation, molting (probably through ecdysteroid-mediated hormones), or lack of cilia for locomotion (Schmidt-Rhaesa etal. 2011; Pisani etal. 18. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. Want to cite, share, or modify this book? Phylum Arthropoda includes animals that have been successful in colonizing terrestrial, aquatic, and aerial habitats. Also a mineral skeleton
This ability to shed the outer skeleton has opened up developmental
Unique features include: 1. their external skeleton. Complete mitochondrial genomes are however available for both onychophoran families (Podsiadlowski etal. Adult nematomorphans are covered in a very thick cuticle that is secreted by the epidermis and is comprised of two layers. The insects comprise the largest class of arthropods in terms of species diversity as well as in terms of biomassat least in terrestrial habitats. 2017). The subphylum Hexapoda includes some insects that are winged (such as fruit flies) and others that are secondarily wingless (such as fleas). Unfortunately, they are all extinct! Their cuticular sclerites (Fig. Terrestrial crustaceans seek out damp spaces in their habitats to lay eggs. Li J, He F-N, Zheng H-X, Zhang R-X, Ren Y-J, Hu W. Lozano-Fernandez J, Carton R, Tanner AR, Puttick MN, Blaxter M, Vinther J, Olesen J, Giribet G, Edgecombe GD, Pisani D. Ma X, Aldridge RJ, Siveter DJ, Siveter DJ, Hou X, Edgecombe GD. By the end of this section, you will be able to do the following: The superphylum Ecdysozoa also includes the phylum Arthropoda, one of the most successful clades of animals on the planet. Irimia M, Maeso I, Penny D, Garcia-Fernndez J, Roy SW. Janssen R, Jrgensen M, Prpic N-M, Budd GE. Phylum Arthropoda is the largest phylum in the animal world, and insects form the . Based on the resulting trees, the most recent common ancestor of extant Panarthropoda was a macroscopic lobopodian with heteronomous body annulation, an anteriorly-facing mouth with radial circumoral papillae, and paired dorsolateral epidermal structures in segmental association with lobopodous limbs (Smith and Ortega-Hernndez 2014). 2014; Sharma etal. Nevertheless, the segment polarity protein engrailed is expressed in the posterior ectoderm of developing segments in each of the three panarthropod groups, suggesting that it plays a common role in establishing segmental boundaries (Gabriel and Goldstein 2007) and can be interpreted as an autapomorphy related to panarthropod segmentation. 2017; Schwentner etal. 2014), or recovered either that grouping or Panarthropoda under different analytical conditions (Dunn etal. Most groups of insects undergo partial or complete metamorphosis
An estimated 77,000 species of chelicerates can be found in almost all terrestrial habitats. Fernndez R, Laumer CE, Vahtera V, Libro S, Kaluziak S, Sharma PP, Prez-Porro AR, Edgecombe GD, Giribet G. Frster F, Beisser D, Grohme MA, Liang C, Mali B, Siegl AM, Engelmann JC, Shkumatov AV, Schokraie E, Mller T, et al. The cuticle is the hard covering of an arthropod. From a molecular standpoint, researchers have proposed a series of synapomorphies, such as the identification of ecdysozoan tissue-specific markers, including neural expression of horseradish peroxidase (HRP) immunoreactivity (Haase etal. Development 126(5): 851-859. 2012), and lobopodians that are either allied to tardigrades or near the base of Panarthropoda such as Aysheaia (Fig. In addition, a lack of mitochondria has been reported in some species (Danovaro etal. The abdomen usually has 11 segments and bears external reproductive apertures. 2010a; Braband etal. 5mm. Adams MD, Celniker SE, Holt RA, Evans CA, Gocayne JD, Amanatides PG, Scherer SE, Li PW, Hoskins RA, Galle RF, et al. first opening to develop in the embryo. The evolution of the ecdysozoan nervous systems has centered on understanding the nature of the brain, which is circumoral in the non-panarthropods (and has been used in the diagnosis of Cycloneuralia as a putative clade) but has cephalic ganglia in the three panarthropod groups (Martin and Mayer 2014; Martn-Durn etal. Millipedes bear two pairs of legs per diplosegmenta feature that results from the embryonic fusion of adjacent pairs of body segments. In effect, life on Earth could conceivably be called the Age of Arthropods beginning nearly 500 million years ago. Crustaceans have a chitinous exoskeleton that is shed by molting and ecdysis whenever the animal requires an increase in size or the next stage of development. The head also has one pair of sensory antennae, as well as sensory organs such as a pair of compound eyes, ocelli (simple eyes), and numerous sensory hairs. are not subject to the Creative Commons license and may not be reproduced without the prior and express written Vinther J, Porras L, Young FJ, Budd GE, Edgecombe GD, Zhang X-G. Wgele JW, Erikson T, Lockhart PJ, Misof B. Wang C, Grohme MA, Mali B, Schill RO, Frohme M. Yang J, Ortega-Hernndez J, Gerber S, Butterfield NJ, Hou JB, Lan T, Zhang X-g. Yoshida Y, Koutsovoulos G, Laetsch DR, Stevens L, Kumar S, Horikawa DD, Ishino K, Komine S, Kunieda T, Tomita M, et al. Another molecular synapomorphy, a supposed multimeric form of a -thymosin gene in arthropods and nematodes to the exclusion of other metazoans (Manuel etal. Likewise, the Cambrian lobopodian Hallucigenia, which has been interpreted as a stem-group onychophoran (Smith and Ortega-Hernndez 2014) or a stem-group panarthropod (Caron and Aria 2017), has radially arranged circumoral lamellae and pharyngeal teeth that compare with putative homologues in tardigrades and cycloneuralians and accordingly cited as possible autapomorphies of Ecdysozoa (Smith and Caron 2015). [15], A modern consensus phylogenetic tree for the protostomes is shown below. The chelicerates have secondarily lost their antennae and hence do not have them. Handbook of Zoology Gastrotricha, Cycloneuralia and Gnathifera Volume 1: Nematomorpha, Priapulida, Kinorhyncha, Loricifera. (1992) based on a phylogenetic analysis of 141 morphological characters of ultrastructural and embryological phenotypes. Additional transcriptomes are now being generated to investigate the phylogenetic position of onychophorans with respect to arthropods and tardigrades and for developmental research (e.g., Franke etal. 2013; Rota-Stabelli etal. 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