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    Polypterids fossil records,natural history,and anatomy

    Discussion in 'Polypterus' started by beblondie, Jun 2, 2007.

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    1. beblondie

      beblondie In Loving Memory

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      Polypterids are the sole survivors of the Order Polypteriformes whose distribution included Africa and South America and can be dated back at least 100 million years in the fossil record. They are among the most primitive of the ray-finned fishes (Actinopterygii) the dominant group of fishes today.

      Our story begins some 245 million years ago with a super continent named Pangaea in the Mesozoic era.Which has three periods the oldest triassic(245-208 mya)(short for Millions of Years Ago) then jurassic(208-146 mya) and the cretaceous(145-65 mya)era.

      Pangaea (Greek for "all lands") was the supercontinent that existed before plate tectonics separated the major continents.Pangaea was believed to have formed 300 million years ago.The vast ocean that surrounded Pangaea has been named Panthalassa.Pangaea is believed to have broken up about 200-180 mya into two supercontinents Laurasia the continents of the northern hemisphere and Gondwana (originally Gondwanaland) which includes most of the landmasses which make up today's continents of the southern hemisphere, Including Africa and South America.

      Gondwana is of intrest to us if you look at the pictures you can see The rift between Africa and South America occurs right in the natural range of the remaining memebers of the Order PolypteriformesThe polypterids.Hope this answers how South America has fossil remains-Anne

      pangaea.jpg
       
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    2. beblondie

      beblondie In Loving Memory

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      Polypterid fossil record
      The polypterid fossil record was for a long time reduced to some scarce, disarticulated bones, mainly scales, found in various African deposits covering a wider area than the actual geographical distribution. With the discovery, on one hand, of polypterid scales, vertebrae, dermal bones of the cranium and dorsal spiny rays in South America and, on the other hand, of scales and numerous dorsal spiny rays in Niger and Sudan, and two articulated fossils in Morocco, the story of the polypteriformes has revealed some of its mysteries. The discovery of isopedine between dentine and bony basal plate in the scales of living and fossil polypterid species is considered a synapomorphy of the group, and has been an important aid in discriminating polypterid scales from other ganoid scales(Fish and Fisheries Volume 2 Issue 2 Page 113 - June 2001)

      livanfossilpolyperiformes.jpg
       
    3. beblondie

      beblondie In Loving Memory

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      The only fully articulated I have ever seen a picture of

      Polypterus faraou
      A new species of Polypterus has been found inside a lump of rock.
      The fish, which is a member of the Cladistia's Polypteridae family, is the first complete fossil polypterid skeleton ever described.
      The extinct species has been named Polypterus faraou in a paper in the Zoological Journal of the Linnean Society and was found in an area known as Toros-Menalla in western Djourab, Chad.
      "The articulated skeleton is preserved in three dimensions..." The articulated skeleton is preserved in three dimensions and has allowed the scientists who discovered it to determine, fairly accurately, where it lies in the fossil record.
      The authors believe the species comes from the Late Miocene(5.3myo) and they claim it's the only verifiable record for the genus Polypterus.
      The species is said to closely resemble Polypterus bichir and P. endlicheri, which still live in the Chad and Chari river systems today.
      They don't know exactly how this and other polypterids are interrelated, but they believe that Polypterus faraou has a primitive body shape and a primitive "shape of opening of the lateral line on the scales" which is also seen in P. bichir, P. ansorgii and P. endlicheri.
      For more details see the paper: Otero O, A Likius, P Vignaud and M Brunet, 2006. A new polypterid fish: Polypterus faraou sp. nov. (Cladistia, Polypteridae) from the Late Miocene, Toros-Menalla, Chad. Zoological Journal of the Linnean Society 146: 227?237.

      Pfarou2.jpg
       
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    4. beblondie

      beblondie In Loving Memory

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      When a species is scientificly described several notations are made including the following measurements

      bichir bichir.JPG
       
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    5. beblondie

      beblondie In Loving Memory

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      The Polypteriformes are a small group of African fresh-water fish comprising
      13 species grouped into two genera,Polypterus and E.calabaricus.Although most
      paleontologists and zoologists agree that Polypteriformes belong to the group of
      osteichthian or bony fish,there exist three divergent views regarding their exact
      position within this broad taxonomic entity: Several observers
      have placed Polypteriformes into a distinct subclass,the Brachiopterygii, whose
      phylogenetic origin is not well defined In contrast,numerous investigators
      have regarded Polypteriformes as belonging to the subclass
      Actinopterygii.In the latter context two phylogenetic hypotheses have been proposed.
      The first is that the Polypteriformes most probably separated from the actinopterygian
      main stem very early (as far back as the late paleozoic ) and independently
      approached the holostean level. The second hypothesis states that the Polypteri-
      formes are primitive actinopterygian fish and represent a living relic of the Paleonis-
      coidei,the extinct ancestors of the entire actinopterygian stock.

      Taxonomy
      The science of taxonomy,is concerned with discovering and describing the enormous diversity of living organisms is an ever-
      changing field.As research sheds light on species and their relationships,taxonomic categories ideally reflect thier diverging paths taken by evolution-responds with name changes and the reassembly of families,orders,classes,phyla,kingdomsand domains.
      Among aquarium organisms are examples of taxa undergoing extensive revisions and ongoing research.

      taxonomic hierarchy
      A logical series of successively larger groups into which a species may be placed according to its supposed evolutionary
      relationships with other species.

      Polypterids are classified as follows
      Taxonomic hierarchy
      Kingdom Animalia -- Animal
      Phylum Chordata -- chordates
      Subphylum Vertebrata -- , vertebrates
      Superclass Osteichthyes -- bony fishes
      Class Actinopterygii -- ray-finned fishes, spiny rayed fishes
      Subclass Chondrostei -- paddlefishes, sturgeons
      Order Polypteriformes
      Family Polypteridae -- bichirs,lobed-finned pike, reed fishes and dinosuar eels
      Genus Polypterus
      Species(example) Polypterus senegalus- gray bichir-Cuviers bichir

      dates listed are when the species were described
      Cladistia Cope, 1871 after Lund, 2000<==o CLADISTIA Cope, 1871 sensu Lund, 2000
      |--o &#8224;GUILDAYICHTHYIFORMES Lund, 2000
      | `--o &#8224;Guildayichthyidae Lund, 2000
      | |-- &#8224;Guildayichthys carnegiei Lund, 2000
      | `-- &#8224;Discoserra pectinodon Lund, 2000
      `--o POLYPTERIFORMES [Brachiopterygii] (niilinhaukikalat)
      |?- &#8224;Dagetella sudamericana [Dajetella]
      `--o Polypteridae (niilinhauet; bichirs)
      |-- Calamoichthys calabaricus (Smith, 1865) [Erpetoichthys] (käärmehauki, käärmekala; Reedfish)
      `--o Polypterus (niilinhauet; bichirs) [9?]
      |-- P. ansorgii Boulenger, 1910 (Guinean bichir)
      |--o P. bichir Geoffroy St. Hilaire, 1802 (niilinhauki)
      | |-- P. b. bichir Geoffroy St. Hilaire, 1802 (Nile bichir)
      | |-- P. b. katangae Poll, 1941
      | `-- P. b. lapradei Steindachner, 1869
      |-- P. delhezi Boulenger, 1899 (Barred bichir)
      |--o P. endlicheri Heckel, 1846-49
      | |-- P. endlicheri congicus Boulenger, 1898
      | `-- P. endlicheri endlicheri Heckel, 1846-49 (Saddled bichir)
      |-- P. ornatipinnis Boulenger, 1902 (Ornate bichir)
      |--o P. palmas Ayres, 1850 (Shortfin bichir)
      | |-- P. palmas buettikoferi Steindachner, 1891
      | |-- P. palmas palmas Ayres, 1850 (Shortfin bichir)
      | `-- P. palmas polli Gosse, 1988
      |-- P. retropinnis Vaillant, 1899 (West African bichir)
      |--o P. senegalus Cuvier, 1829 (Gray bichir)
      | |-- P. senegalus meridionalis Poll, 1941
      | `-- P. senegalus senegalus Cuvier, 1829 (Gray bichir)
      `-- P. weeksii Boulenger, 1898 (Mottled bichir)

      Reference(s):
      Carroll, R. L., 1988: Vertebrate paleontology and evolution.
      --W. H. Freeman and company, New York, 1988. 698.
      Carroll, R. L., 1988: Appendix. 594-648.
      in Carroll, R. L., 1988: Vertebrate paleontology and evolution.
      --W. H. Freeman and company, New York. 1988.
      Frickhinger, K. A., 1995: Fossil Atlas - Fishes. 1-1088
      --Mergus, Publishers for Natural History and Pet Books, Hans A.Baensch, Malle, Germany
      Froese, R. & Pauly, D. (eds), 2001: FishBase.
      --iNet: www.fishbase.org
      Long, J. A., 1995: The Rise of Fishes: 500 million years of evolution.
      --Johns Hopkins University Press, Baltimore & London, pp. 1-223
      Lund, R., 2000: The new actinopterygian order Guildayichthyiformes from the
      Lower Carboniferous of Montana (USA).
      --Geodiversitas: Vol. 22, #2, pp. 171-206
      Nelson, J. S., 1994: Fishes of the world.
      --John Wiley & Sons, Inc., New York, 1994. XX-600.
      --Tullock,James 2000 Dictionary of Aquarium terms
       
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    6. beblondie

      beblondie In Loving Memory

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      In May 1798,Napoleon Bonaparte set out from France for a major expedition to Egypt.Much more important were the lasting cultural and scientific effects of this expedition. For many centuries, Egypt had been a mysterious country where foreigners (especially Christians) were not welcome. Therefore, antiquarians interested in Ancient Egypt merely had access to the few antiquities taken to Europe by the Romans or by contemporary merchants, and to the inaccurate reports written by Greek and Roman authors. It was Napoleon who really opened up Egypt for the West.
      Napoleon had found out that first-hand experience on Egypt&#8217;s past and present was practically lacking.In order to remedy this state of affairs, he decided to invite 167 scholars and artists to accompany the expedition.In 1798 Geoffroy Saint-Hilaire was chosen to be a member of Napoleon's great scientific expedition to Egypt.It was here along the banks of the Nile Geoffroy Saint-Hilaire discovered a in the Nile a one meter-long green fish with gar like scales and several finlets on its back and named it Polypterus(many fins).In 1802 the scientific name Polypterus bichir was given at a conference.it had already been known along the Nile since the time of the pharoahs. The local peoples referred to it as a bichir (unknown pronunciation and spelling). While unable to come up with an exact meaning for the word it was most likely a descriptive term (''whip'' has been suggested) for this type of fish.The French most likely pronounced it as phonetically as possible to the orginal native word and came up with bee-sheer as a pronunciation and spelled 'bichir'.In 1809, the year after his return to France, he was made professor of zoology at the faculty of sciences at Paris, and from that period he devoted himself more exclusively than before to anatomical study.

      "If I had discovered only this species in Egypt, it would compensate me for the pains usually involved in a long journey"
      Geoffroy Saint-Hilaire, 1809, describing the genus Polypterus and its Nile species Polypterus bichir.*
      (English translation)

      So who was Cuvier?
      Baron Georges Léopold Chrétien Frédéric Dagobert Cuvier (August 23, 1769&#8211;May 13, 1832) was a French naturalist and zoologist.Cuvier, after corresponding with the well-known naturalist Étienne Geoffroy Saint-Hilaire, was appointed in 1795, at the age of 26, as assistant to the professor of comparative anatomy at the Muséum National.Cuvier's researches on fish, begun in 1801, finally culminated in the publication of the Histoire naturelle des poissons, which contained descriptions of 5000 species of fishes.
      In 1794 Geoffroy Saint-Hilaire entered into correspondence with Georges Cuvier. Shortly after the appointment of Cuvier as assistant at the Museum d'Histoire Naturelle, Geoffroy received him into his house. The two friends wrote together five memoirs on natural history, one of which, on the classification of mammals, puts forward the idea of the subordination of characters upon which Cuvier based his zoological system.
      Animals named after Cuvier
      These include Cuvier's beaked whale, Cuvier's Gazelle, Cuvier's toucan, Cuvier's Bichir, and Galeocerdo cuvieri, the tiger shark.
      There are also some extinct animals named after Cuvier, such as the South American giant sloth Catonyx cuvieri.
       
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    7. beblondie

      beblondie In Loving Memory

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      Polypterid
      SCALES
      Polypterids are covered by multilayered scales, rhombiod in shape, with an outer layer of ganoine a middle layer of dentine a layer of isopidine and an inner dermal, cosmine bony layer and are referred to as ganoid scales. Only the bowfin (Amiidae) share this scalation. While the scales of Lepisosteidae species may look the same they lack the middle dentine layer present in Polypterids and Amiidae.
       
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    8. beblondie

      beblondie In Loving Memory

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      LUNGS
      Paleontological evidence shows that air-breathing appeared some 438-408 million years ago during the late Silurian period (Sundstrom 2002).
      Two main theories are trying to explain its evolution.
      1) Theory 1 more widely accepted one argues that warm tropical waters were suffering from either periodical or constant low concentrations of dissolved oxygen. Based on observations of modern species, an existing behavioral responce is fish moving to shallower, higher oxygen availabilty water and utilyzing aquatic surface respiration. Such pressure led to the evolution of specialized organs for breathing athmospheric air and retreaving its oxygen contents (Sundstrom 2002).
      2) The second theory suggests that fish started gulping air to increase their buoyancy; the result was again an air-breathing system (Sundstrom 2002).
      In fact, evidence supports both hypothesis. Studies have shown that the air-breathing fish exhibit various structural, behavioral, physiological characteristics, and differ in ventilatory control and central/periferal receptor interactions. This suggests that air-breathing has evolved independently. Graham (1997) stipulates between 38 and 67 independent occurences of air-breathing.
      A study by Perry et al. (2001) on the origin of potentially homologous air-filled organs (lungs and swimbladders) also demonstrates the complexity of figuring out the evolution of air-breathing. The Polypteriformes, lungfish, and tetrapods are characterised by the existence of lungs; in all other bony fish the swimbladder is ancestral. Perry et al.(2001) defines lungs as "paired ventral derivatives of the pharynx posterior to the gills." The unpaired swimbladder in gar fish (Ginglymodi), bowfin (Halecomporphi), and basal teleosts is dorsal and evolved from the posterior pharynx. The authors of "Which came first, the lung or the breath?" (Perry et al., 2001) demonstrate that extreme variation exists even though air ventilatory mechanisms in the ray-finned fish (Actinopterygii) and Polypteriformes are similar among different groups, and are markedly different from those of lungfish and tetrapods. Evidence exists that supports the theory that homologous pharyngeal air-filled organs first appeared in early bony fish, but resulted from behavioral mechanisms for surface (water) breathing. The posterior gill pouches or the gills served by the sixth branchial artery might have been the early air-filled organs. It could have later evolved into the respiratory swimbladder and the lungs.
      Wilson et al. (2000) also looked into the difference between the lobe-finned (Sarcopterygii) and the ray-finned (Actinopterygii) fish, both of which have evolved primitive air breathers. The tetrapods, which stem from Sarcopterygii, utilise a chemoreceptor bound central pattern generator. It is subject to control from both central and peripheral CO2/H+ chemoreceptors. On the contrary, Actinopterygii are believed to lack such chemoreceptors and rely instead on "reflexive" behavior. However, using in vitro brainstem from longnose gar fish, Wilson et al. (2000) show that air-breathing patterns occur in brainstem and are subject to changing levels of carbon dioxide. The authors make a case that a central neuronal controller for air-breathing appeared in a common ancestor before the split of lobe-finned and ray-finned fish. This illustrates the difficulty of quantifying the number of independent evolutions of air-breathing suggested above by Graham (1997).Note how the lung on the right runs almost the lenght of the body.
      pic from digimorph
      The wall of the asymmetrical saclike lungs of the fishes Polypterus and Erpetoichthys consists of several functionally different tissue layers. Their lumen is lined by a surface epithelium composed of (1) highly attenuated cells, termed pneumocytes I; (2) pneumocytes II with lamellar bodies, presumably indicating surfactant production; (3) mucous cells; and (4) ciliated cells. Underlying the pneumocytes I is a dense capillary net. The thin continuous endothelium of this net, together with the pneumocytes I, constitute the very thin blood-air barrier. The basement membrane of epithelium and endothelium fuse in the area of the blood-air barrier (thickness 210 m). Secretory and ciliary cells form longitudinal rows in the epithelium. Below the zone with a gas-exchanging tissue, a layer of connective tissue containing collagen and special elastic fibers occurs. The blood vessels that give rise to or drain the superficial capillary plexus are located in this connective tissue. The outermost layer of the lung consists of muscle cells, a narrow inner zone with smooth muscle cells, and an outer, broader zone with cross-striated muscle cells. The lung is innervated by myelinated and nonmyelinated nerve fibers. The morphology of the gas-exchange tissue in the lungs of these primitive bony fish is fundamentally very similar to that of the lungs of tetrapod vertebrates. The morphologic observations are in close agreement with physiologic data, disclosing well-developed respiratory capacities. Structural simplicity can be regarded as a model from which the lungs of the higher vertebrates derived. In addition to respiratory function, the lungs seem also to have hydrostatic tasks.
      A. Lechleuthner 1, U. Schumacher 1, R. D. Negele 2, Dr. U. Welsch 1 *
      1Department of Anatomy, University of Munich, Federal Republic of Germany
      2Bavarian Institution for Freshwater Research, Wielenbach, Federal Republic of Germany
      *Correspondence to U. Welsch, Anatomische Anstalt, Universität München, Pettenkoferstr. 11,8000 München 2, FRG
      The respiratory behaviour in Polypterus senegalus. P. senegalus rarely resorts to aerial respiration under normal conditions.The consumption of atmospheric O2 depends on the activity and age of fish and the availability of aquatic oxygen.immature fish cannot utilize aerial O2 but older fish exhibit age-dependent reliance on aerial respiration in *hypoxic and** hypercarbic waters.Atmospheric O2 accounts for approx. 50% of the total oxygen needed when aquatic O2 levels are approx.3.5mg per liter (or CO2is about 5%) an fish rely exclusively on atmospheric O2 in oncentrations of less than 2.5mgl.Branchial respiration is initially stimulated by **hypercarbia (CO2: 0.5–0.8%) but increased** hypercarbia (CO2 – 1%) greatly depresses (by over 90%) brancial respiration and initiates (CO2: 0.5%) and sustains pulmonary respiration.
      *hypoxic = very low oxygen levels
      **hypercarbic = the presence of an abnormally high level of carbon dioxide
      Development of dependence on aerial respiration in Polypterus senegalus (Cuvier)
      M. M. Babiker1
      (1) Department of Zoology, Faculty of Science, University of Khartoum, Sudan
      photo/digimorph

      dived airblad.jpg
       
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    9. beblondie

      beblondie In Loving Memory

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      TEETH
      Polypteriformes show a derived condition with respect to structure, arrangement, replacement, and differentiation of teeth,which arises in sequence during larval development.This also corresponds to observed changes of feeding behaviour and functional demands during larval life.
      Dentition and dentigerous bones in juveniles and adults of Polypterus senegalus (Cladistia, Actinopterygii).
      Clemen G, Bartsch P, Wacker K.
      Institut fur Spezielle Zoologie und Vergleichende Embryologie, Universitat Munster.

      Tooth types,their arrangement and the mode of tooth replacement were studied in juvenile and adult specimens of Polypterus senegalus by means of scanning electron microscopy of cleared and stained specimens as well as sections. All the dermal bones of the oropharynx are almost completely covered with teeth except for the angulare.The same is true for the branchial apparatus where only the hyoid skeleton is toothless. The teeth are uniformly monocuspid and conical, but can be classified according to shape and size into three types.These types and the mode of tooth replacement are characteristic for each dermal bone.In some of the jaw bones each tooth possesses a lingually situated replacement tooth. This is true for the teeth of the premaxillary, the maxillary, and the dentary which are arranged in a single line, and those of the dermopalatine, the coronoids, and the vomer which are in several lines and graded in size.Replacement teeth of all the other dentigerous elements develop on top of existing pulpal openings,forming an anastomosing common pulpal complex only after resorption of the previous tooth.The tooth plates of the dermal bones of the branchial apparatus are connected by syndesmosis only to the perichondrally ossified and to the cartilaginous or connective tissue material of the elements of the gill-arches.The dentition and its association with the bones of the head in Polypterus senegalus bear resemblances to advanced actinopterygians on the one hand (e.g.differentiation of tooth-types, arrangement),but also some similarities to living Amphibia (anchoring material and mode of replacement) on the other.The accentuation of a single marginal line of large teeth in both, the outer and the inner dental arcade of the jaws is a peculiarity of Polypterus that in a way parallels the derived state of similar monolinear tooth arrangements in Actinopterygii and Tetrapoda.
      Clemen G, Bartsch P, Wacker K.
      Institut fur Spezielle Zoologie und Vergleichende Embryologie, Universitat Munster.

      Test results showed that the structure of the dental epithelial cells in Polypterus was different from that in teleosts and gars, but that the function of the dental epithelial cells was similar to that in teleosts possessing well-mineralized cap enameloid.The development of the tooth pattern and dentigerous bones in Polypterus senegalus (Cladistia, Actinopterygii).
      Department of Anatomy, School of Dentistry at Niigata, Nippon Dental University, Niigata, Japan

      The tooth cap matrix contained proteins of ectodermal and mesodermal origin which extended the data already available on teleost teeth and showed that a combined origin for the tooth cap should be regarded as a primitive feature of actinopterygian fish.Furthermore,the dual nature of the Polypterus tooth cap matrix suggested that evolution of tetrapod enamel did not occur within the actinopterygians.The collar tissue was an unmodified dentine, in contrast to its enameloid nature in many other actinopterygian teeth.
      PMID: 6953936 [PubMed - indexed for MEDLINE]
      Scripps Institution of Oceanography, Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla, USA.
       
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    10. beblondie

      beblondie In Loving Memory

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      scent hunter(Polypterid) vs Sight hunter brain.Note the differences in the
      Telencephalon where chemoreception(smell) is processed and the optic tectum where visual information is processed.

      polybrain.jpg
       
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