Paleozoic Life Radiation of the Animal Phyla Cambrian Life

Total Page:16

File Type:pdf, Size:1020Kb

Paleozoic Life Radiation of the Animal Phyla Cambrian Life Outline 14: Paleozoic Life Radiation of the Animal Phyla Cambrian Life • The first animals evolved about 100 my before the start of the Cambrian. These are the Ediacaran fossils of the latest Proterozoic. • None of these animals had hard parts. • Base of the Cambrian defined by first animals with hard parts. Life at the end of the Proterozoic Cambrian Life • Early Cambrian fossils consist mostly of trilobites, brachiopods, archaeocyathids, and small little shells. Cambrian trilobites cruising on Saturday night Typical Cambrian trilobites Modern horseshoe crabs look similar to trilobites, but they are not closely related. Example of a “living fossil.” Trilobites are extinct. A living Inarticulate Brachiopod. Very common fossils in the Cambrian. Modern Inarticulate Brachiopods in their burrows Modern Inarticulate Brachiopods for dinner in southeastern Asia. Cambrian Archaeocyathids: Reef-Forming Animals Examples of small shelly fossils from the Early Cambrian. Scale bars are 0.1 mm. Cambrian Life • The Middle Cambrian Burgess Shale records the “Explosion of Life.” All known phyla had appeared by then. • A phylum is a major body plan. Examples: Mollusca, Annelida, Arthropoda, Chordata, etc. Animals got their start in the Ediacaran, followed by the Cambrian “Explosion of Life.” Sponges Kevin Peterson, Dartmouth The Cambrian Explosion made the cover of TIME. Burgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization. • Of today’s 32 living phyla, 15 are found in the Burgess Shale. The other 17 are microscopic or too delicate to be preserved. • Another 10 extinct phyla are also found in the Burgess Shale. Burgess Shale Fossils • Assume that all 32 living phyla were alive in the Middle Cambrian. • Add the 10 extinct phyla for a total of 42 phyla. That’s more phyla than today! • Thus, Cambrian phyla were more diverse than today. A Paradox • There were more body plans (phyla) near the start of animal life than today. • However, there were many fewer species. • This doesn’t match the expectation of slow evolutionary diversification of life. The Pattern of Animal Evolution • Initial radiation of phyla. • Reduction by natural selection. • No new phyla since the Cambrian. • Diversification within remaining phyla. A Hypothesis • The genome of early animals was less rigid, not as “hardwired” as later animals. Adaptive mutations were more possible. • A wide variety of body plans were produced by mutations. • Natural selection eliminated some of these body plans. A Hypothesis • Body plans that survived became the modern phyla. • 500 m.y. of evolution has made genomes more rigid and more species rich. • Mutations required to make a new body plan would be lethal. Phyla were locked in. The Burgess Shale of British Columbia, Canada: record of the Cambrian Explosion Mt. Stephen in Yoho National Park, Canada Geologists at the Burgess Shale quarry Trilobites! Paleontologist collecting a slab of fossils Trilobites with preserved legs and antennae The strange animals of the Middle Cambrian Burgess Shale Opabinia and Amwiskia, representatives of two extinct phyla Opabinia The first sea scorpion on the attack! Marella, extinct class of arthropods Marella, extinct class of arthropods Marella as Cambrian road kill (or a squished bug?) Yohoia, an extinct class of arthropods Specimens of lobopods Living and fossil lobopods Burgess Shale worm Ottoia A spiny “worm,” Wiwaxia Hallucigenia, a spiny lobopod Which way is up? Hallucigenia Correct Interpretation Original Interpretation. Anomalocaris, the largest predator of the Cambrian and an extinct phylum. Trilobite with a bite mark, possibly from Anomalocaris Pikaia Anomalocaris in hot pursuit of Marella Pikaia, an early chordate Pikaia, a chordate from the Burgess Shale Yunnanozoan, a chordate from the early Cambrian of China Primitive chordates: Tunicates or Sea Squirts. Adults have a pharynx with gill slits. Larval forms are free-swimming and have a notochord. Fish are thought to have evolved from the larval form by precocious sexual maturation. Chordate evolution Branchiostoma, the lancelet; a primitive living chordate Invertebrates after the Cambrian Phylum Cnidaria: colonial corals Phylum Cnidaria: horn coral Skeleton of a modern coral A living sea anemone, relative of corals Living coral reefs Living coral reefs Phylum Bryozoa - fossils Phylum Bryozoa – living animals Phylum Brachiopoda BIVALVIA Phylum Mollusca Mollusca: Class Bivalvia Fossil marine bivalve, Kansas Phylum Mollusca: Class Gastropoda Phylum Mollusca: Class Cephalopoda Nautilus Nautilus A Paleozoic Cephaplopod Phylum Arthropoda An Ordovician Trilobite A Silurian Trilobite The Devonian Trilobite Phacops rana The compound eye of Phacops rana A death assemblage of Phacops rana Eurypterid or “Sea Scorpian”, Silurian of New York A Cenozoic crab Phylum Echinodermata Crinoid Blastoid A living crinoid at a depth of 692 m, Bahamas Slab of Mississippian crinoids – note the long stems for feeding high above the substrate Asteroid Ophiuroid Starfish feeding on bivalves Devonian starfish Echinoids: sand dollar (left) sea biscuit (below) Holothurian: sea cucumber.
Recommended publications
  • Curious Creatures Using Fossil and Modern Evidence to Work out the Lifestyles of Extinct Animals
    Earthlearningidea http://www.earthlearningidea.com Curious creatures Using fossil and modern evidence to work out the lifestyles of extinct animals Try comparing the features of animals today with • Of what animal(s) alive today does it remind you? those of fossils - can you predict the lifestyles of the • How did the animal move? (swim, crawl, float, extinct animals? wriggle, hop). • How did it catch its food? (predators often have Divide the pupils into groups. Give each group a copy grasping limbs for catching prey. Not all animals of the diagrams of animals shown below and a copy are herbivores or carnivores; some are filter of the reconstruction of life on page 3. Tell the pupils feeders (like mussels) or deposit feeders (like that all of these creatures lived in the sea about 515 worms). million years ago before there were any plants or • Could it see? (predators often have large eyes for animals on land. hunting). (Further background information is given for teachers • Is there evidence of other organs that could sense on page 2). the environment around? (feelers). • Look at the diagram on page 3. Where do you For each of the five animals shown in the diagram, think it lived? (swimming around, on the seabed, ask the pupils to answer the following questions and burrowing, on another animal or plant). to list the evidence they have used:- • Can you deduce anything else about the lifestyles of these five animals? Images reproduced with kind permission of The Burgess Shale Geoscience Foundation http://www.burgess-shale.bc.ca ……………………………………………………………………………………………………………………………………. The back up: Title: Curious creatures Time needed to complete activity: 20 minutes Subtitle: Using fossil and modern evidence to work Pupil learning outcomes: Pupils can: out the lifestyles of extinct animals • relate characteristics of marine animals today to similar characteristics shown by fossil evidence Topic: A snapshot of the history of life on Earth from long-extinct creatures; • realise that there are no right answers to this Age range of pupils: 10 - 18 years activity.
    [Show full text]
  • Biology of Chordates Video Guide
    Branches on the Tree of Life DVD – CHORDATES Written and photographed by David Denning and Bruce Russell ©2005, BioMEDIA ASSOCIATES (THUMBNAIL IMAGES IN THIS GUIDE ARE FROM THE DVD PROGRAM) .. .. To many students, the phylum Chordata doesn’t seem to make much sense. It contains such apparently disparate animals as tunicates (sea squirts), lancelets, fish and humans. This program explores the evolution, structure and classification of chordates with the main goal to clarify the unity of Phylum Chordata. All chordates possess four characteristics that define the phylum, although in most species, these characteristics can only be seen during a relatively small portion of the life cycle (and this is often an embryonic or larval stage, when the animal is difficult to observe). These defining characteristics are: the notochord (dorsal stiffening rod), a hollow dorsal nerve cord; pharyngeal gills; and a post anal tail that includes the notochord and nerve cord. Subphylum Urochordata The most primitive chordates are the tunicates or sea squirts, and closely related groups such as the larvaceans (Appendicularians). In tunicates, the chordate characteristics can be observed only by examining the entire life cycle. The adult feeds using a ‘pharyngeal basket’, a type of pharyngeal gill formed into a mesh-like basket. Cilia on the gill draw water into the mouth, through the basket mesh and out the excurrent siphon. Tunicates have an unusual heart which pumps by ‘wringing out’. It also reverses direction periodically. Tunicates are usually hermaphroditic, often casting eggs and sperm directly into the sea. After fertilization, the zygote develops into a ‘tadpole larva’. This swimming larva shows the remaining three chordate characters - notochord, dorsal nerve cord and post-anal tail.
    [Show full text]
  • Using Information in Taxonomists' Heads to Resolve Hagfish And
    This article was downloaded by: [Max Planck Inst fuer Evolutionsbiologie] On: 03 September 2013, At: 07:01 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Historical Biology: An International Journal of Paleobiology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ghbi20 Using information in taxonomists’ heads to resolve hagfish and lamprey relationships and recapitulate craniate–vertebrate phylogenetic history Maria Abou Chakra a , Brian Keith Hall b & Johnny Ricky Stone a b c d a Department of Biology , McMaster University , Hamilton , Canada b Department of Biology , Dalhousie University , Halifax , Canada c Origins Institute, McMaster University , Hamilton , Canada d SHARCNet, McMaster University , Hamilton , Canada Published online: 02 Sep 2013. To cite this article: Historical Biology (2013): Using information in taxonomists’ heads to resolve hagfish and lamprey relationships and recapitulate craniate–vertebrate phylogenetic history, Historical Biology: An International Journal of Paleobiology To link to this article: http://dx.doi.org/10.1080/08912963.2013.825792 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information.
    [Show full text]
  • Fish and Amphibians
    Fish and Amphibians Geology 331 Paleontology Phylum Chordata: Subphyla Urochordata, Cephalochordata, and: Subphylum Vertebrata Class Agnatha: jawless fish, includes the hagfish, conodonts, lampreys, and ostracoderms (armored jawless fish) Gnathostomates: jawed fish Class Chondrichthyes: cartilaginous fish Class Placoderms: armored fish Class Osteichthyes: bony fish Subclass Actinopterygians: ray-finned fish Subclass Sarcopterygians: lobe-finned fish Order Dipnoans: lung fish Order Crossopterygians: coelocanths and rhipidistians Class Amphibia Urochordates: Sea Squirts. Adults have a pharynx with gill slits. Larval forms are free-swimming and have a notochord. Chordates are thought to have evolved from the larval form by precocious sexual maturation. Chordate evolution Cephalochordate: Branchiostoma, the lancelet Pikaia, a cephalochordate from the Burgess Shale Yunnanozoon, a cephalochordate from the Lower Cambrian of China Haikouichthys, agnathan, Lower Cambrian of China - Chengjiang fauna, scale is 5 mm A living jawless fish, the lamprey, Class Agnatha Jawless fish do have teeth! A fossil jawless fish, Class Agnatha, Ostracoderm, Hemicyclaspis, Silurian Agnathan, Ostracoderm, Athenaegis, Silurian of Canada Agnathan, Ostracoderm, Pteraspis, Devonian of the U.K. Agnathan, Ostracoderm, Liliaspis, Devonian of Russia Jaws evolved by modification of the gill arch bones. The placoderms were the armored fish of the Paleozoic Placoderm, Dunkleosteus, Devonian of Ohio Asterolepis, Placoderms, Devonian of Latvia Placoderm, Devonian of Australia Chondrichthyes: A freshwater shark of the Carboniferous Fossil tooth of a Great White shark Chondrichthyes, Great White Shark Chondrichthyes, Carcharhinus Sphyrna - hammerhead shark Himantura - a ray Manta Ray Fish Anatomy: Ray-finned fish Osteichthyes: ray-finned fish: clownfish Osteichthyes: ray-finned fish, deep water species Lophius, an Eocene fish showing the ray fins. This is an anglerfish.
    [Show full text]
  • LETTER Doi:10.1038/Nature13414
    LETTER doi:10.1038/nature13414 A primitive fish from the Cambrian of North America Simon Conway Morris1 & Jean-Bernard Caron2,3 Knowledge of the early evolution of fish largely depends on soft- (Extended Data Fig. 4f). Incompleteness precludes a precise estimate of bodied material from the Lower (Series 2) Cambrian period of South size range, but themostcomplete specimens (Fig.1a,b) areabout 60 mm China1,2. Owing to the rarity of some of these forms and a general in length and 8–13 mm in height. Laterally the body is fusiform, widest lack of comparative material from other deposits, interpretations of near the middle, tapering to a fine point posteriorly (Fig. 1a, b and Ex- various features remain controversial3,4, as do their wider relation- tended Data Fig. 4a), whereas in dorsal view the anterior termination is ships amongst post-Cambrian early un-skeletonized jawless verte- rounded (Fig. 1d and Extended Data Fig. 4c–e). The animal was com- brates. Here we redescribe Metaspriggina5 on the basis of new material pressed laterally, as is evident from occasional folding of the body as well from the Burgess Shale and exceptionally preserved material collected as specimensindorso-ventral orientation being conspicuously narrower near Marble Canyon, British Columbia6, and three other Cambrian (Fig. 1a and Extended Data Fig. 5a). Along the anterior ventral margin Burgess Shale-type deposits from Laurentia. This primitive fish dis- there was a keel-like structure (Fig. 1b, g, i, k, l), but no fins have been plays unambiguous vertebrate features: a notochord, a pair of prom- recognized. In the much more abundant specimens of Haikouichthys1,3,4 inent camera-type eyes, paired nasal sacs, possible cranium and arcualia, fins are seldom obvious, suggesting that their absence in Metaspriggina W-shaped myomeres, and a post-anal tail.
    [Show full text]
  • The Secrets of Fossils Lesson by Tucker Hirsch
    The Secrets of Fossils Lesson by Tucker Hirsch Video Titles: Introduction: A New view of the Evolution of Animals Cambrian Explosion Jenny Clack, Paleontologist: The First Vertebrate Walks on Land Des Collins, Paleontologist: The Burgess Shale Activity Subject: Assessing evolutionary links NEXT GENERATION SCIENCE STANDARDS and evidence from comparative analysis of the fossil MS-LS4-1 Analyze and interpret data for patterns record and modern day organisms. in the fossil record that document the existence, diversity, extinction, and change of life forms Grade Level: 6 – 8 grades throughout the history of life on Earth under the Introduction assumptions that natural laws operate today as In this lesson students make connections between in the past. [Clarification Statement: Emphasis fossils and modern day organisms. Using the is on finding patterns of changes in the level of information about the Cambrian Explosion, they complexity of anatomical structures in organisms explore theories about how and why organisms diversified. Students hypothesize what evidence and the chronological order of fossil appearance might be helpful to connect fossil organisms to in the rock layers.] [Assessment Boundary: modern organisms to show evolutionary connections. Assessment does not include the names of Students use three videos from shapeoflife.org. individual species or geological eras in the fossil record.] Assessments Written MS-LS4-2 Apply scientific ideas to construct an Time 100-120 minutes (2 class periods) explanation for the anatomical similarities and Group Size Varies; single student, student pairs, differences among modern organisms and between entire class modern and fossil organisms to infer evolutionary relationships. [Clarification Statement: Emphasis Materials and Preparation is on explanations of the evolutionary relationships • Access to the Internet to watch 4 Shape of Life videos among organisms in terms of similarity or • Video Worksheet differences of the gross appearance of anatomical • “Ancient-Modern” Activity.
    [Show full text]
  • The Fossil Record of the Cambrian “Explosion”: Resolving the Tree of Life Critics As Posing Challenges to Evolution
    Article The Fossil Record of the Cambrian “Explosion”: 1 Resolving the Tree of Life Keith B. Miller Keith B. Miller The Cambrian “explosion” has been the focus of extensive scientifi c study, discussion, and debate for decades. It has also received considerable attention by evolution critics as posing challenges to evolution. In the last number of years, fossil discoveries from around the world, and particularly in China, have enabled the reconstruction of many of the deep branches within the invertebrate animal tree of life. Fossils representing “sister groups” and “stem groups” for living phyla have been recognized within the latest Precambrian (Neoproterozoic) and Cambrian. Important transitional steps between living phyla and their common ancestors are preserved. These include the rise of mollusks from their common ancestor with the annelids, the evolution of arthropods from lobopods and priapulid worms, the likely evolution of brachiopods from tommotiids, and the rise of chordates and echinoderms from early deuterostomes. With continued new discoveries, the early evolutionary record of the animal phyla is becoming ever better resolved. The tree of life as a model for the diversifi cation of life over time remains robust, and strongly supported by the Neoproterozoic and Cambrian fossil record. he most fundamental claim of bio- (such as snails, crabs, or sea urchins) as it logical evolution is that all living does to the fi rst appearance and diversi- T organisms represent the outer tips fi cation of dinosaurs, birds, or mammals. of a diversifying, upward- branching tree This early diversifi cation of invertebrates of life. The “Tree of Life” is an extreme- apparently occurred around the time of ly powerful metaphor that captures the the Precambrian/Cambrian boundary over essence of evolution.
    [Show full text]
  • A Personal View XVIII. Food Webs & Stability of Ecological Networks
    Systems Biology Across Scales: A Personal View XVIII. Food Webs & Stability of Ecological Networks Sitabhra Sinha IMSc Chennai Alaskan food web Network of Ecological Interactions Simple food chains …are embedded in more… Complex food webs Arrows indicate direction of energy flow Early understanding of food webs “Not a single plant, not even a lichen, grows on this island; yet it is inhabited by several insects and spiders” Charles Darwin,1839 “In February, 1832, Darwin described the food web of St. Paul's Rocks near the equator in the middle of the Atlantic Ocean, and remarked with surprise on the apparent absence of plants.” J E Cohen (1994) in Frontiers of Mathematical Biology (ed S A Levin) Abundance of each species maintained at a natural equilibrium: “Moebius in1877... recognized the importance of interspecific nutritive relationships while he was studying the organisms living on the oyster- beds of Schleswig-Holstein. To Moebius is due also the credit for noting that the effect of these interspecific relationships is to establish a state of equilibrium.” U d' Ancona (1954) The Struggle for Existence First known network of trophic relations First graphical representation of a food web as a network of groups of species linked by feeding relations Lorenzo Camerano (1880) 1856 – 1917 Network nodes classified into several taxa Plants Parasitic plants Insects Worms Spiders Crustaceans Fish Amphibians Reptiles Birds Mammals Web of interactions between Coleoptera, (beetle), their predators and predators of predators Summerhayes and Elton (1923) Food web of Bear Island Wikipedia Wikipedia Source: Neo Martinez Food web of Little Rock Lake, Wisconsin Antarctic Weddell Sea Food Web Source: Neo Martinez Ecology of Early Earth: Cambrian “Explosion” Annelid Canadia Arthropod Marrella Charles Walcott, Secretary of Hallucigenia the Smithsonian, discovered Cambrian-era fossils where soft body parts (e.g., eyes, muscles, gills, digestive system, etc.) was preserved in the Burgess shale in Velvet Worm Aysheaia the Canadian Rockies in 1909.
    [Show full text]
  • Lobopodian Phylogeny Reanalysed
    BRIEF COMMUNICATIONS ARISING Phylogenetic position of Diania challenged ARISING FROM J. Liu et al. Nature 470, 526–530 (2011) Liu et al.1 describe a new and remarkable fossil, Diania cactiformis. absent. For example, character 6 (position of frontal appendage) can This animal apparently combined the soft trunk of lobopodians (a only be coded in taxa that possess a frontal appendage (character 5) in group including the extant velvet worms in addition to many the first instance (such that a ‘‘0’’ for character 5 necessitates a ‘‘-’’ for Palaeozoic genera) with the jointed limbs that typify arthropods. character 6). In morphological analyses such as this, inapplicable They go on to promote Diania as the immediate sister group to the states are usually assumed to have no bearing on the analysis, being arthropods, and conjecture that sclerotized and jointed limbs may reconstructed passively in the light of known states. In analyses of therefore have evolved before articulated trunk tergites in the imme- nucleotide data, by contrast, gaps may alternatively be construed as a diate arthropod stem. The data published by Liu et al.1 do not un- fifth and novel state, because shared deletions from some ancestral ambiguously support these conclusions; rather, we believe that Diania sequence may actually be informative. If this assumption is made with probably belongs within an unresolved clade or paraphyletic grade of morphological data, however, all the logically uncodable states in a lobopodians. character are initially assumed to be homologous, and a legitimate Without taking issue with the interpretation of Diania offered by basis for recognizing clades.
    [Show full text]
  • The Early History of the Metazoa—A Paleontologist's Viewpoint
    ISSN 20790864, Biology Bulletin Reviews, 2015, Vol. 5, No. 5, pp. 415–461. © Pleiades Publishing, Ltd., 2015. Original Russian Text © A.Yu. Zhuravlev, 2014, published in Zhurnal Obshchei Biologii, 2014, Vol. 75, No. 6, pp. 411–465. The Early History of the Metazoa—a Paleontologist’s Viewpoint A. Yu. Zhuravlev Geological Institute, Russian Academy of Sciences, per. Pyzhevsky 7, Moscow, 7119017 Russia email: [email protected] Received January 21, 2014 Abstract—Successful molecular biology, which led to the revision of fundamental views on the relationships and evolutionary pathways of major groups (“phyla”) of multicellular animals, has been much more appre ciated by paleontologists than by zoologists. This is not surprising, because it is the fossil record that provides evidence for the hypotheses of molecular biology. The fossil record suggests that the different “phyla” now united in the Ecdysozoa, which comprises arthropods, onychophorans, tardigrades, priapulids, and nemato morphs, include a number of transitional forms that became extinct in the early Palaeozoic. The morphology of these organisms agrees entirely with that of the hypothetical ancestral forms reconstructed based on onto genetic studies. No intermediates, even tentative ones, between arthropods and annelids are found in the fos sil record. The study of the earliest Deuterostomia, the only branch of the Bilateria agreed on by all biological disciplines, gives insight into their early evolutionary history, suggesting the existence of motile bilaterally symmetrical forms at the dawn of chordates, hemichordates, and echinoderms. Interpretation of the early history of the Lophotrochozoa is even more difficult because, in contrast to other bilaterians, their oldest fos sils are preserved only as mineralized skeletons.
    [Show full text]
  • Opabinia Regalis
    Crazy Creatures Opabinia regalis Opabinia was a very odd creature found in the Time: 500 Million Cambrian period about 500 million years ago. It was an arthropod, which means a creature Years ago with an exoskeleton. Period: Cambrian Opabinia was only 5cm long but was a ferocious predator. It lived in the sea and ate other small animals including very early fish Prawn with and lots of other arthropods. It was very well adapted to it's environment. a trunk! Your task 1: Draw Opabinia! It had: 5 mushroom shaped eyes a long trunk with sharp pincers at the end a round mouth underneath fifteen short fins on each side a tail with five longer fins Your task 2: Opabinia was well adapted to it's environment. This meant everything about it made it good at living in the sea. What kind of environment do you think it lived in? Think of a sea environment that would need: lots of eyes a long trunk a body for slow, careful swimming Creature Fact! Your task 3: Opabinia was a fierce predator but didn't have any jaws or There are millions of teeth! Jaws and teeth help us to chew arthropods around today hard foods. Without jaws, what kind of but none of them are food do you think Opabinia ate? related to Opabinia – it's so weird it is put in a group of animals all on it's own! Your task 4: Noone knows what Opabinia's large trunk was for! What other kinds of animals have trunks, and what do they use them for? Could Opabinia have used their trunks the same way? Your task 5: Opabinia is one of many famous fossils from a certain very famous place in the palaeontological world.
    [Show full text]
  • Fossils, Histology, and Phylogeny: Why Conodonts Are Not Vertebrates
    234 by Alain Blieck1, Susan Turner2,3, Carole J. Burrow3, Hans-Peter Schultze4, Carl B. Rexroad5, Pierre Bultynck6 and Godfrey S. Nowlan7 Fossils, histology, and phylogeny: Why conodonts are not vertebrates 1Université Lille 1: Sciences de la Terre, FRE 3298 du CNRS «Géosystèmes», F-59655 Villeneuve d’Ascq cedex, France. E-mail: [email protected] 2Monash University, Geosciences, Box 28E, Victoria 3800, Australia 3Queensland Museum, Geosciences, 122 Gerler Road, Hendra, Queensland 4011, Australia 4Kansas University, Biodiversity Institute & Natural History Museum, 1345 Jayhawk Blvd., Lawrence, KS 66045-7593, USA 5Indiana Geological Survey, 611 North Walnut Grove, Bloomington, IN 47405-2208, USA 6Institut Royal des Sciences Naturelles de Belgique, Département de Paléontologie, Rue Vautier, 29, B-1000 Bruxelles, Belgium 7Geological Survey of Canada, 3303 – 33rd Street NW, Calgary, AB T2L 2A7, Canada The term vertebrate is generally viewed by help resolve the phylogenetic relationships of conodonts systematists in two contexts, either as Craniata and chordates, the analysis should be extended to (myxinoids or hagfishes + vertebrates s.s., i.e. basically, include non-chordate taxa. animals possessing a stiff backbone) or as Vertebrata (lampreys + other vertebrae-bearing animals, which Historical background we propose to call here Euvertebrata). Craniates are characterized by a skull; vertebrates by vertebrae A recent paper by Sweet and Cooper (2008), within the classic paper series of Episodes, drew our attention and prompted this (arcualia); euvertebrates are vertebrates with hard response. Their paper concerned the discovery and the concept of phosphatised tissues in the skeleton. The earliest conodonts by Christian Heinrich Pander (1856). He was the first known possible craniate is Myllokunmingia (syn.
    [Show full text]