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Filo Arthropoda Superclasse Trilobitomorpha Classe Trilobita

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Filo Arthropoda Superclasse Trilobitomorpha Classe Trilobita 8.2. IDENTIFICAÇÃO DE FÓSSEIS DE TRILOBITA Fig. 8.1 - Agnostus Filo Arthropoda Superclasse Trilobitomorpha Classe Trilobita Subclasse Miomera Ordem Agnostida Agnostus BRONGNIART, 1822 Fig. 8.1 Agnostus sp. Extraído de BONDARENKO & MIKHAILOVA (1984: 344). Carapaça muito pequena, até 10 mm de comprimento, isopígica. Cefalão ovalado, desprovido de olhos e de sutura facial, apresentando bordadura evidente. Glabela estreia e longa, com um estrangulamento profundo (sulco glabelar) próximo do extremo anterior. Torace constituído por dois segmentos. Pigídio com bordadura evidente, apresentando um par de espinhos curtos postero-laterais, dotado de ráquis longa, cónica, subdividida em três segmentos, pouco afilada para o Fig. 8.2 - Peronopsis extremo posterior. Paleoecologia: Organismos epibentónicos vágeis a endobentónicos (?), detritívoros (?). Ambientes mari- nhos bentónicos, pouco profundos, de salinidade normal. Distribuição estratigráfica: Câmbrico. Peronopsis HAWLE & CORDA, 1847 Fig. 8.2 Peronopsis gaspensis Rasetti. Adaptado de MOORE et al. (1952: 498). Carapaça muito pequena, até 10 mm de comprimento, isopígica. Cefalão semicircular, desprovido de olhos e de sutura facial, apresentando bordadura evidente. Glabela estreita e longa, com um estrangulamento próximo do extremo anterior. Torace constituído por dois segmentos. Pigídio com bordadura evidente, dotado de ráquis longa, não-segmentada, afilada posteriormente. Paleoecologia: Organismos epibentónicos vágeis a endobentónicos (?), detritívoros (?). Ambientes mari- nhos neríticos pouco profundos, de salinidade normal. Distribuição estratigráfica: Câmbrico. Subclasse Polymera Ordem Redlichiida Paradoxides BRONGNIART, 1822 Fig. 8.3 Paradoxides davidis Salter. Extraído de COX (1964: est. 2). Carapaça grande, podendo atingir cerca de 50 cm de comprimento, acentuadamente micropígica. Cefalão grande, com olhos bem definidos, holocróicos, em forma de crescente e com lóbulos palpebrais proeminentes, e faces móveis (librígenas) amplas, apresentando longos Fig. 8.3 - Paradoxides espinhos genais. Glabela grande, lisa, expandindo-se Departamento de GEOLOGIA TRILOBITA anteriormente, formando uma frente ampla e arredondada. Sulcos glabelares, normalmente 2 ou 4 pares, bem definidos, podendo unir-se na zona central da glabela. Torace com 16-21 segmentos com zonas pleurais mais amplas que a ráquis e apresentando-se muito afiladas, espinhosas. Pigídio muito pequeno, espatulado, com ráquis segmentada. Paleoecologia: Organismos epibentónicos vágeis, detritívoros (?). Ambientes marinhos bentónicos, pouco profundos, de salinidade normal. Distribuição estratigráfica: Câmbrico médio. Ordem Corynexochida Ectillaenus SALTER, 1867 Fig. 8.4 - Ectillaenus Fig. 8.4 Ectillenus katzeri (Barrande). De RICHTER (1989: 254). Carapaça média a grande (até 30 cm), isopígica, com cefalão e pigídio, praticamente, da mesma forma. Cefalão subtriangular arredondado, liso, com ângulos genais boleados, apresentando glabela mal definida, E. giganteus Burmeister, 1843 curta e lisa, com relevo baixo, não-limitada do lado anterior e desprovida de sulcos glabelares. Olhos pequenos, próximos do bordo do cefalão, por vezes de difícil observação. Sutura facial opistopária. Librígenas estreitas e subtriangulares. Torace constituido por 10 segmentos. Pigídio semicircular, praticamente liso, com ráquis quase imperceptível, lisa e com fronteira posterior indefinida. Paleoecologia: Organismos epibentónicos vágeis a endobentónicos, detritívoros (?). Ambientes marinhos bentónicos, pouco profundos, de salinidade normal. Distribuição estratigráfica: Ordovícico. Ordem Phacopida Fig. 8.5 - Calymene Calymene BRONGNIART, 1822 Fig. 8.5 Calymene blumenbachii. Extraído de TASCH (1973: 520). Carapaça de dimensões médias, micropígica. Cefalão semicircular, com ângulos genais arredondados. Glabela campaniforme, bastante proeminente, convexa, Fig. 8.6 - Dalmanites estreitando anteriormente, apresentando 3-4 lobos glabelares, sendo o par L1 o mais desenvolvido; o L2 atravessa o sulco dorsal, ao encontro de uma saliência na face fixa (fixígena). Olhos pequenos, holocróicos. Sutura facial gonatopária. Torace com cerca de 12-13 segmentos, com extremos pleurais arredondados. Pigídio alargado, subtriangular a semicircular, costilhado, apresentando ráquis segmentada. Paleoecologia: Ver Paradoxides, acima. Distribuição estratigráfica: Silúrico a Devónico. Observações: Os exemplares de Calymenidae portugueses são atribuídos ao género Neseuretus Hicks (e.g., Neseuretus avus = N. tristani), próximo de Calymene. Eodalmanitina HENRY, 1965 Fig. 8.6 Dalmanites myops (König), espécie de género aparentado, próximo de Eodalmanitina. Extraído de COX (1964: est. 28). Fig. 8.7 Eodalmanitina destombesi Henry, 1966. Ordovícico de Valongo. 8 cm. Carapaça média (até 8 cm), micropígica. Cefalão algo Fig. 8.7 - Eodalmanitina ogival, com glabela claviforme, alargando anteriormente destombesi (com lóbulo frontal, Lf, muito desenvolvido), com sulcos glabelares bem marcados: SO, S1 e S2 equidistantes, 56 TRILOBITA S2 nunca atingindo o sulco dorsal. Pontas genais bem desenvolvidas, longas e finas (raramente se conservam). Olhos bem desenvolvidos, grandes, esquizocróicos. Sutura facial propária. Torace com cerca de 11 segmentos. Pigídio subtriangular, apresentando ponta caudal, ou caudícula, e ráquis pigidial com 8-12 anéis. Paleoecologia: Organismos epibentónicos vágeis, detritívoros (?). Ambientes marinhos bentónicos, pouco profundos, de salinidade normal. Distribuição estratigráfica: Ordovícico médio. Phacops EMMRICH, 1836 Fig. 8.8 Phacops fecundus. Extraído de TASCH (1973: 520). Fig. 8.8 - Phacops Carapaça média a grande (até 20 cm), isopígica a micropígica. Cefalão semicircular, com ângulos genais arredondados, apresentando glabela muito inflada e alargando para diante, ornamentada com granulações evidentes. Sulco glabelar S1 podendo atravessar a glabela, formando anel pré-occipital; S2 e seguintes mal definidos ou ausentes. Olhos bem desenvolvidos, grandes, esquizocróicos. Sutura facial propária. Torace com cerca de 11 segmentos, com extremos pleurais arredondados. Pigídio semicircular, com oito ou menos pleuras e com ráquis pigidial ostentando 9-11 anéis. Paleoecologia: Organismos epibentónicos vágeis, detritívoros (?). Ambientes marinhos bentónicos, pouco profundos, de salinidade normal. Distribuição estratigráfica: Devónico. Encrinurus EMMRICH & CORDA, 1844 Fig. 8.9 Encrinurus punctatus (Wahlenberg). Extraído de COX (1964: est. 29). Carapaça pequena a média (até 8 cm), micropígica. Cefalão subtriangular, com pontas genais curtas e afiladas. Glabela inflada e alargando para diante, Fig. 8.9 - Encrinurus ornamentada com fortes granulações, ostentando três pares de sulcos glabelares muito curtos, normalmente camuflados pela forte ornamentação da glabela. Olhos bem desenvolvidos, holocróicos, por vezes pedunculados, posicionados junto do L2 ou L3. Sutura facial propária. Torace com cerca de 10-12 segmentos, com extremos pleurais algo arredondados. Pigídio triangular, algo alongado, com oito ou menos pares de costilhas pleurais e com ráquis pigidial ostentando 9-11 anéis. Paleoecologia: Organismos epibentónicos vágeis, detritívoros (?). Ambientes marinhos bentónicos, pouco profundos, de salinidade normal. Distribuição estratigráfica: Ordovícico a Devónico inferior. Placoparia HAWLE & CORDA, 1847 Fig. 8.10 Placoparia cambriensis Hicks. Extraído de COX (1964: est. 8). Carapaça pequena (até 4 cm), acentuadamente micropígica. Cefalão semicircular. Glabela com lados subparalelos, alargando ligeiramente para diante, Fig. 8.10 - Placoparia desprovida de área pré-glabelar. Sutura glabelar S3 oblíqua, atingindo o sulco dorsal no canto anterior da glabela, S1 e S2 subperpendiculares ao sulco dorsal. 57 TRILOBITA Sutura facial opistopária. Olhos ausentes. Torace constituído por 11-12 segmentos, apresentando a banda posterior de cada pleura inflada. Pigídio muito pequeno, ostentando ráquis com quatro anéis axiais, mais uma peça terminal subtriangular, e igual número de costilhas pigidiais infladas, com extremos salientes, mas arredondados, conferindo-lhe aspecto algo “aracnóide”. Paleoecologia: Organismos epibentónicos vágeis, detritívoros (?). Ambientes marinhos bentónicos, pouco profundos, de salinidade normal. Distribuição estratigráfica: Ordovícico. Deiphon BARRANDE, 1852 Fig. 8.11 Deiphon sp. Extraído de BONDARENKO & MIKHAILOVA (1984: 358). Carapaça micropígica, pequena a média (até 4 cm), com aspecto “sui generis”, muito espinhosa e com ornamentação finamente granulosa. Cefalão constituído, praticamente, por uma glabela muito inflada, quase esférica, não segmentada, e por faces reduzidas a longos espinhos encurvados. Olhos pequenos, instalados no bordo anterior das faces, junto à glabela. Torace constituído por nove segmentos com expansões pleurais longas e espinhosas, encurvadas lateralmente. Pigídio ostentando dois pares de espinhos, sendo os posteriores muito longos, expandidos lateralmente. Paleoecologia: Segundo alguns autores estas trilobites seriam organismos pelágicos nectónicos. Ambientes marinhos pelágicos, neríticos profundos a oceânicos, de salinidade normal. Fig. 8.11 - Deiphon Distribuição estratigráfica: Silúrico. BIBLIOGRAFIA COX, L.R. 1964. British Palaeozoic Fossils. British Museum (Natural History), Londres, 4ª edição, 1983, 203 pp. BONDARENKO, O.B. & MIKHAILOVA, I.A. 1984. Kratkii Opredelitel’ Iskopaemykh Bespozvonotchnykh. Nedra, Moscovo, 2ª edição, 536 pp. MOORE, R.C.; LALICKER, C.G. & FISHER, A.G. 1952. Invertebrate Fossils. McGraw-Hill Book Comp. Inc., New York, 766 pp. RICHTER, A.E. 1981. Manual del coleccionista de fósiles. Ediciones Omega, Barcelona, edição de 1989, 460 pp. TASCH, P. 1973. Paleontology of the Invertebrates. Data retrieval from the fossil record. John Wiley & Sons, New York, 2ª edição, 1980, 975 pp. 2015/16 NOTAS / OBSERVAÇÕES: 58 .
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