Universidade Estadual De Campinas Instituto De Biologia

UNIVERSIDADE ESTADUAL DE CAMPINAS INSTITUTO DE BIOLOGIA

THAÍS APARECIDA MARINHO

INVESTIGATING THE THYASIRIDAE DALL, 1901 (BIVALVIA, MOLLUSCA)

FROM THE SOUTHWESTERN ATLANTIC OCEAN: A STUDY ON THE

MORPHOLOGY AND TAXONOMY OF THE BRAZILIAN SPECIES

INVESTIGANDO OS THYASIRIDAE DALL, 1901 (BIVALVIA, MOLLUSCA) DO

SUDOESTE DO OCEANO ATLÂNTICO: UM ESTUDO DA MORFOLOGIA E

TAXONOMIA DAS ESPÉCIES DO BRASIL

CAMPINAS

2020 THAÍS APARECIDA MARINHO

INVESTIGATING THE THYASIRIDAE DALL, 1901 (BIVALVIA, MOLLUSCA)

FROM THE SOUTHWESTERN ATLANTIC OCEAN: A STUDY ON THE

MORPHOLOGY AND TAXONOMY OF THE BRAZILIAN SPECIES

INVESTIGANDO OS THYASIRIDAE DALL, 1901 (BIVALVIA, MOLLUSCA) DO

SUDOESTE DO OCEANO ATLÂNTICO: UM ESTUDO DA MORFOLOGIA E

TAXONOMIA DAS ESPÉCIES DO BRASIL

Dissertation presented to the Institute of Biology of the University of Campinas in partial fulfillment of the requirements for the degree of Master in Animal Biology in the area of Animal Biodiversity.

Dissertação apresentada ao Instituto de Biologia da Universidade Estadual de Campinas como parte dos requisitos exigidos para a obtenção do Título de Mestra em Biologia Animal na área de Biodiversidade Animal.

Orientador: PROF. DR. FLAVIO DIAS PASSOS

ESTE ARQUIVO DIGITAL CORRESPONDE À VERSÃO FINAL DA DISSERTAÇÃO DEFENDIDA PELA ALUNA THAIS APARECIDA MARINHO E ORIENTADA PELO PROF. DR. FLAVIO DIAS PASSOS.

CAMPINAS

2020 Ficha catalográfica Universidade Estadual de Campinas Biblioteca do Instituto de Biologia Mara Janaina de Oliveira - CRB 8/6972

Marinho, Thaís Aparecida, 1991- M338i MarInvestigating the Thyasiridae Dall, 1901 (Bivalvia, Mollusca) from the Southwestern Atlantic Ocean : a study of the morphology and taxonomy of the Brazilian species / Thaís Aparecida Marinho. – Campinas, SP : [s.n.], 2020.

MarOrientador: Flávio Dias Passos. MarDissertação (mestrado) – Universidade Estadual de Campinas, Instituto de Biologia.

Mar1. Bivalve - Atlântico, Oceano. 2. Molusco - Classificação. 3. Molusco - Morfologia. 4. Ecologia do fundo do mar. 5. Quimiossimbiose. I. Passos, Flávio Dias, 1971-. II. Universidade Estadual de Campinas. Instituto de Biologia. III. Título.

Informações para Biblioteca Digital

Título em outro idioma: Investigando os Thyasiridae Dall, 1901 (Bivalvia, Mollusca) do Sudoeste do Oceano Atlântico : um estudo da morfologia e taxonomia das espécies do Brasil Palavras-chave em inglês: Bivalve - Atlantic Ocean Mollusks - Classification Mollusks - Morphology Deep-sea ecology Chemosymbiosis Área de concentração: Biodiversidade Animal Titulação: Mestra em Biologia Animal Banca examinadora: Flávio Dias Passos [Orientador] Eliane Pintor de Arruda Michela Borges Data de defesa: 24-06-2020 Programa de Pós-Graduação: Biologia Animal

Identificação e informações acadêmicas do(a) aluno(a) - ORCID do autor: https://orcid.org/0000-0003-1299-1246 - Currículo Lattes do autor: http://lattes.cnpq.br/4945512436131064

COMISSÃO EXAMINADORA

Prof. Dr. Flavio Dias Passos

Prof.(a). Dr.(a) Eliane Pintor de Arruda

Prof.(a). Dr.(a). Michela Borges

Os membros da Comissão Examinadora acima assinaram a Ata de defesa, que se encontra no processo de vida acadêmica do aluno.

A Ata da defesa com as respectivas assinaturas dos membros encontra-se no SIGA/Sistema de Fluxo de Dissertação/Tese e na Secretaria do Programa de Pós Graduação em Biologia Animal da Unidade do Instituto de Biologia.

AGRADECIMENTOS

Agradecimento especial ao meu orientador Prof. Dr. Flavio Dias Passos pela confiança depositada durante todos esses anos. Obrigada por ter dedicado o seu tempo a me ensinar um pouco sobre esse grupo incrível que é Thyasiridae e também sobre os bivalves marinhos. Obrigada pelos momentos de descontração no laboratório, pelas risadas, pelos almoços e também pelas conversas sérias necessárias. Me sinto agradecida por ter feito parte desse meu crescimento no mundo científico por isso meu singelo “Obrigada”! O presente trabalho foi realizado com apoio da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Código de Financiamento 001. À Instituição Smithsonian por ter financiado através do “Kenneth Jay Boss Fellowship in Invertebrate Zoology” pelo período de três meses em que pude ter acesso a coleção de Thyasiridae do National Museum of Natural History. Meu obrigada especial para Dr. Ellen Strong e Dr. Jerry Harasewych, que me ajudaram durante todo o processo de aplicação até meu último dia na instituição. Obrigada as pessoas que me apoiaram e fizeram meus dias melhores durante todo meu tempo em Washington, DC: Juan e Chaya por todo o apoio e amizade. E Yolanda Villacampa, Scott e Amanda, que tornaram possível todas as minhas necessidades dentro do museu. Agradeço imensamente os meus amigos do Laboratório de Malacologia da Unicamp, Alan, Ana Clara, Fabrízio, Marcel e Pedro. Jamais esquecerei as conversas, risadas, almoços e lanchinhos da tarde, que me fizeram seguir forte durante todo o período do mestrado. Não tenho palavras para agradecer o quanto sou grata por tudo que fizeram por mim e nem pela amizade construída com as melhores pessoas dessa Unicamp. Sem vocês, com certeza não chegaria e nem seria metade do que sou hoje. Aos meus amigos de longa data, Diogo, Luciano, Carol e Yohans, agradeço pela paciência, por lutarem cada batalha comigo, e por me oferecerem sempre um conselho carinhoso e abraço apertado quando precisei. Sem vocês não teria sido possível trilhar esse caminho. Vocês são as melhores pessoas que eu podia ter. Agradeço minha família, Cristiane, Salvador e Thamires e minhas avós, Maria e Joana, que são a minha fortaleza e que me permitem estar sempre forte a frente de todas as decisões

e rumos que tomo. Vocês são o meu bem mais precioso. Obrigada por estarem comigo sempre e por confiar em mim. Obrigada a todos que participaram direta ou indiretamente desse momento da minha vida e que me fortaleceu para seguir.

RESUMO

Thyasiridae é o segundo táxon mais frequentemente encontrado em habitats marinhos considerados “hostis”, como sedimentos associados a fontes hidrotermais, plataformas de petróleo, ossadas de baleia e madeira em decomposição ou àqueles circundante a vulcões. Nesses habitats, a quantidade de nutrientes disponíveis, a baixa taxa de oxigênio e o alto nível de pressão são três principais estresses ambientais que podem provocar variações morfológicas e anatômicas em bivalves. Decorrente desses fatores as espécies podem sofrer redução significativa ou perda de partes, até órgãos inteiros relacionados ao sistema digestório, podendo impulsionar a associação com bactérias quimiossintetizantes. Neste trabalho foram examinados exemplares coletados pelos projetos HABITATS e AMBES, executados pela Petrobrás, assim como ALUCIA em colaboração com Prof. Dr. Paulo Sumida, os quais foram identificados a nível específico contribuindo para o conhecimento da malacológica brasileira. Thyasira Lamarck, 1818, Parathyasira Iredale, 1930 e Spinaxinus Oliver & Holmes, 2006 foram os gêneros identificados para o litoral sul e sudeste brasileiro, totalizando em quatro espécies: Thyasria trisinuata (d’Orbigny, 1846), T. obsoleta (Verril & Bush, 1898), Parathyasira granulosa (Monterosato, 1874) e Spinaxinus sp. Para compreender as diferenças entre as espécies e seus problemas taxonômicos os materiais-tipo foram examinados e esses provenientes das seguintes instituições: Museu de Zoologia da Universidade Estadual de Campinas “Adão José Cardoso” (ZUEC), São Paulo, Brasil; Museu Nacional do Rio de Janeiro e coleção do Laboratório de Malacologia da UFRJ, ambos no Rio de Janeiro, Brasil; National Museum of Natural History, Smithsonian Institution, e Museum of Comparative Zoology of Harvard University, ambos nos Estados Unidos da América; Muséum National d’Histoire Naturelle, Paris, França; e Museum of Wales e Natural History Museum of London, ambos da Inglaterra. Através da microscopia eletrônica de varredura foram observados detalhes da superfície externa da concha como presença ou ausência de microestruturas do perióstraco e morfologia da concha larval, as quais são características principais que permitem distinguir as espécies entre si e de suas similares.

Palavras-chave: Thyasiridae – Taxonomia – Mar profundo - Quimiosimbiontes

ABSTRACT

Thyasiridae is the second most frequent taxon found in marine “hostile habitats”, such as hydrothermal vents, oildfields, organic falls and sediment near of volcanoes. In those habitats, the quantity of available nutrients, low rate of oxygen and high level of pressure are the three main environmental factors that might cause morphological and anatomical variation in bivalves. The variations might be the reduction or lack of organs related to digestive system triggering the association with chemossymbionts bacterias. In this work, the analyzed samples were collected from HABITATS and AMBES projects executed by Petrobrás and also samples from ALUCIA, a project in collaboration with Prof. Dr. Paulo Sumida. The samples were examined and identified until specific level contributing to the knowledge of Mollusca biodiversity in Brazilian coast. Thyasira Lamarck, 1818, Parathyasira Monterosato, 1874 and Spinaxinus Oliver & Holmes, 2006 were found to the Southern and Southeastern coasts of Brazil totalizing four species, Thyasria trisinuata (d’Orbigny, 1846), T. obsoleta (Verril & Bush, 1898), Parathyasira granulosa (Monterosato, 1874) e Spinaxinus sp. Type materials of each species were examined focusing on better understanding of the differences among those species and their taxonomical problems. Those samples are from the following institutions: Museu de Zoologia da Universidade Estadual de Campinas “Adão José Cardoso” (ZUEC), São Paulo, Brazil; Museu Nacional do Rio de Janeiro, and, the collection of Laboratório de Malacologia da UFRJ, both from Rio de Janeiro, Brazil; National Museum of Natural History, Smithsonian Institution, United States of America; Museum of Comparative Zoology of Harvard University, also from USA; Muséum National d’Histoire Naturelle, Paris, France; and Museum of Wales e Natural History Museum of London, both from England. Scanning Electron Microscope helped to observe external surface details, like the presence or absence of periostracum microstructures and the larval shell morphology which distinguish the species among each other and their similar.

Keywords: Thyasiridae – Taxonomy – Deep sea - Chemosymbionts

LIST OF FIGURES

Figure 1 – Transects of the Projects Ambes and Habitats….…………………………….18

Figure 2 – Route of Alucia ………………………………………………………………19

Figure 3 – Structures terminology of external and internal surfaces ……………………21

Figure 4 – Structures terminology of dorsal and posterior views ……………………….22

Figure 5 – Thyasira trisinuata …………………………………………………………..32

Figure 6 – Thyasira trisinuata (SEM images)..………………………………………….33

Figure 7 – Thyasira obsoleta ……………………………………………………………38

Figure 8 – Thyasira obsoleta (SEM images).……………………………………………39

Figure 9 – Parathyasira granulosa ……………………………………………………...45

Figure 10 – Parathyasira granulosa (SEM images).…………………………………….46

Figure 11 – Spinaxinus sp ……………………………………………………………….51

Figure 12 – Spinaxinus sp (SEM images).……………………………………………….52

Figure 13 – Thyasira biplicata …………………………………………………………..91

Figure 14 – Thyasira flexuosa …………………………………………………………...92

Figure 15 – Thyasira gouldii …………………………………………………………….93

Figure 16 – Thyasira sarsi ……………………………………………………………….94

Figure 17 – Type-species samples ……………………………………………………….95

LIST OF TABLES

Table 1 – Total analyzed valves...... 65

Table 2 – Examined and re-identified samples from National Museum of Natural History – Smithsonian Institution. …………………………………………………………………66

SUMARY

INTRODUCTION ...... 12 OBJECTIVES ...... 16 MATERIAL AND METHOD ...... 17 Sampling area...... 17

Terminology ...... 20

RESULTS ...... 23

Thyasira trisinuata ...... 24

Thyasira obsoleta ...... 34

Parathyasira granulosa ...... 40

Spinaxinus sp ...... 47

DISCUSSION ...... 53 GENERAL CONCLUSIONS ...... 56 REFERENCES ...... 57 APPENDIX ...... 65 ANNEX ……………………………………………………………………………………97

INTRODUCTION

Within the Phylum Mollusca, Bivalvia is the second largest class after Gastropoda. Its name is based on its bilateral symmetric and laterally compressed body, covered by the external calcareous skeleton, the shell, which is divided in two valves. These valves may contain on their internal surface the impressed scars left by muscular insertions, which may bring the ontogenetic history of the group (Bieler et. al., 2013). Bivalves are highly explored economically because of their very proteic tissues and thus their value in the food industry, aquaculture and fishering; but they have also known because of invasive species (Bieler & Mikkelsen, 2006; Bieler et. al., 2013).

Studies on bivalves have been carried out since 18th century trying to fill up gaps on knowledge about the taxonomy, morphology, anatomy and phylogeny, among other areas, within the group. The number of bivalve species described worldwide differs among geographic regions, probably due to differences in the number of specialists and research funding, some areas being in a “discovery period”, still needing basic work and information (Bieler et al, 2013). This is the case of tropical regions such as Brazil from where more species have to be found and basic research to be reached on, like alpha taxonomy (Bouchet, 1997; Bieler et al, 2013), supporting the use of different methods and analysis to explore the local diversity (Bieler & Mikkelsen, 2006). Even though there are numerous species in bivalves, knowledge about most of them is proportionally scarce. In Brazilian waters, half of Bivalvia species is still unknown and the other half needs information about the basic biology and taxonomic review (Simone, 1999). Some of the most studied families, like Mytilidae, Ostreidae and Pectinidae, still need further studies about their biology, shell morphology, anatomy and molecular data.

Bivalves have different benthic lifestyles, living as epifaunal or infaunal animals. The latter find in marine sediments some of the richest habitats for them to live in. In the deep-sea environment (>200 m depth), organisms should be able to adapt to some specific conditions in the habitat such as cold temperature, no natural light, high pressures and restricted nutrient sources originated from organic matter that sinks from the water column (Snelgrove, 1997). In that environment, there are areas called “hostile habitats” which may have methane and/or sulphide aside from other hydrocarbons compounds flux that come from inside the oceanic crust (Arvidson et. al., 2004). Some organisms survive in those areas because they are associated with chemosimbiont bacterias that reduce sulphide compounds, or archeas that reduce methane compounds (Paul et. al., 1984; Sibuet & Olu, 1998; Tunnicliffe et. al., 2003; Dubilier et. al., 2008).

This association has been registered for different groups of animals and for a variety of latitude and depth gradients in marine environments (Sibuet & Olu, 1998). Examples of such “hostile habitats” are hydrothermal vents (Corliss et. al., 1979; Takai & Nakamura, 2011), oilfieds (Killen & Oliver, 2002a), mud volcanoes (Oliver & Holmes, 2006; Rodrigues et. al., 2008), whale falls (Smith et. al., 1989; Smith & Baco, 2003) and wood falls (Fagervold et. al., 2012; Kalenitchenko et. al., 2015; Kalenitchenko et. al., 2016; Kalenitchenko et. al., 2018). The latter are so called organic falls.

Chemosynthetic habitats have been recorded in specific places around the world according to their geologic origin (Arvidson et. al., 2004). The high level of organic matter coming from decomposition process improves the dispersion of organisms and act as trampoline or temporary habits allowing the colonization of other new habitats (Smith et. al., 1989; Distel et. al., 2000). Different bivalve taxa are found on these hostile environments such as Protobranchia, Pectinidae, Cuspidariidae, Verticordiidae and Thyasiridae.

Species of bivalves living in the deep sea generally present morphologic and anatomical variations due to three main environmental stresses: (i) quantity and quality of available nutrients, (ii) low level of oxygen rate and (iii) high level of pressure. The reduction of size and volume of individual body cause anatomical modifications, as in the gills and the organs related to digestive system (mouth, stomach and gut), which suffer reduction or loss affecting directly the feeding habits and then triggering the association with other organisms, such as chemosymbiotic bacterias (Allen, 2008). The association process and its evolution are the main interest for many authors who tried to describe and understand the adaptations directly related to the bacteria or archea (e. g. Allen, 1958; Dando et. al., 1986; Southward, 1986; Distel & Felbeck, 1987; Payne & Allen, 1991; Anderson, 1995; Frankiel & Moueza, 1995; Distel, 1998; Taylor & Glover, 2000; Dufour, 2005; Taylor & Glover, 2006; Glover et. al., 2008; Rodrigues et. al., 2008; Oliver, 2014; Astrom et. al., 2017; Oliver & Rodrigues, 2017).

Except for the Protobranchia, Thyasiridae species are the most frequently found in these deep-sea habitats (Allen, 2008; Rodrigues et. al., 2008). This family has 28 genera, but only 11 living with 150 known species, approximately (Worms, 2017). Among these genera, Conchocele Gabb, 1866, Thyasira Lamarck, 1818 and Maorithyas Fleming, 1950 have been recorded as bearing species associated with chemosymbiotic bacterias, while for Axinopsida Keen & Chavan in Chavan, 1951, Genaxinus Iredale, 1930 and Mendicula Iredale, 1924 there are no records on this

association (Kauffman, 1969; Southward, 1986; Taylor & Glover, 2000; Fujiwara et. al., 2001; Dufour & Felbeck, 2003; Dufour, 2005; Oliver & Levin, 2006; Taylor et. al., 2007; Oliver & Rodrigues, 2017). Differently from other bivalve families with chemosymbiotic bacterias, Thyasiridae species hold the bacteria externally from gill cells, meaning that the bacteria are ectosymbionts. Thyasira sarsi and T. equalis are exceptions, because the bacterias live inside of the gill cells, as endosymbionts, as it occurs species of Lucinidae (Southward, 1986; Dufour 2005; Taylor et. al., 2007). Few published papers considered anatomical and shell morphologies of Thyasiridae species (e.g. Allen, 1958; Payne & Allen, 1991; Taylor & Glover, 2000; Killeen & Oliver, 2002a; Taylor & Glover, 2006; Passos et. al., 2007; Rodrigues et. al., 2008). Related to their minute body, some taxonomic characters are not evident, such as the external ornamentation and its patterns, muscles scars, hinge and prodissoconch details, what justified scarce knowledge on the biology and taxonomy of this group.

Bernard (1983) classified Thyasiridae in two subfamilies, Thyasirinae and Axinopsinae, which were mainly differentiated by the numbers of demibranchs present in each ctenidium – Thyasirinae bearing both demibranchs and Axinopsinae having a single inner one. This character was considered enough by Coan et al. (2000) to recognize these subfamilies, but not by other authors. Huber (2015), otherwise, suggested the resumption of that organization including not only anatomical characters, but also, shell morphology. Meanwhile, Williams et al. (2004) and Taylor et al. (2007) showed, according to their phylogenetic analysis, that both Thyasirinae and Axinopsinae are not strongly supported. Thyasiridae has been included to Lucinida as the sister- group of Lucinidae, both belonging to Euheterodonta within the Imparidentia (Bieler et al., 2006; Bieler et al., 2013; Bieler et al., 2014). Giribet & Distel (2003) and Sharma et al. (2012) supported the clade Lucinida, contrary to Williams et al. (2004), who suggested that Thyasiridae and Ungulinidae are two distinct and not related superfamilies, the Thyasiroidea and Ungulinoidea, respectively.

Among all genera of Thyasiridae, Thyasira Lamarck, 1818 is the most problematic. In this genus there are ten subgenera, which are placed as subcategory because of their tenuous differences compared to the type-species, Tellina flexuosa Montagu, 1803 (Payne & Allen, 1991; Coan et al. 2000; Killeen & Oliver, 2002a; Coan & Valentich-Scott, 2012). Huber (2015) discussed the validation of these subgenera as distinct genera considering, then, that the small differences are

relevant taxonomic characters, mainly for minute infaunal species (Oliver & Holmes, 2006; Taylor & Glover, 2006; Oliver et al, 2013; Huber, 2015; Astrom et al., 2017). WorMs (2017) is holding the subcategories as genera.

First designated as a genus by Iredale (1930), Parathyasira Iredale, 1930 was posteriorly considered a subcategory of Thyasira (Smith & Heppell, 1990; Payne & Allen, 1991). Zelaya (2009), Oliver (2014), Oliver et al. (2015) and Oliver & Rodrigues (2017) did not agree to keep Parathyasira as subgenus because of its spiny microstructures and the absence of the auricle projection on posterior margin.

Spinaxinus is the most recent described genus of Thyasiridae. It was designated by Oliver & Holmes (2006) based on the presence of periostracum spinose microstructures. Periostracum microstructure is not unique for Spinaxinus and Parathyasira, but should also be found in Thyasira species (e.g. Oliver & Holmes, 2006). Up to now, there are four described species of Spinaxinus, most of them occurring in hostile habitats, such as hydrothermal vents, cold seeps, mud volcanoes, and organic falls (whale bones and/or wood) (Oliver & Holmes, 2006).

The knowledge of the Thyasiridae from the Brazilian coast can be considered scarce. Based on literature, the diversity of the Brazilian thyasirids can be summarized as this: Rios (1985, 1994) and Pimpão (2004) recorded two species of Thyasira – Thyasira trisinuata and T. croulinensis; Payne & Allen (1991) described a new species from the Brazilian Basin – northeast coast, Thyasira transversa; Absalão & Oliveira (2007) and Rios (2009) added one more species Mendicula ferruginosa; and Absalão (2010) made a checklist book for the Campos Basin – Rio de Janeiro, and listed Thyasira sp., and Axinulus sp., both without description and illustration/photos. Viegas (2015) also analyzed material from Campos Basin and recorded fourteen species from six different genera: two new species of Adontorhina, one of Axinopsida, one of Axinus, one of Mendicula, six of Thyasira, and the new occurrence of Axinulus antarcticus Zelaya, 2010, Mendicula ferruginosa (Forbes, 1844), Mendicula inflata (Payne & Allen, 1991) and Thyasira obsoleta (Verrill & Bush, 1898). In conclusion, only six species of thyasirids were formally described, justifying the necessity of more studies on the taxonomy of this family.

OBJECTIVES

The main goal of this work is to contribute to the knowledge about the diversity of Brazilian malacofauna focusing on the species of the family Thyasiridae.

The specific objectives are:

● Furnish a detailed description of the shell of four species and compared to their congeners; ● Register the ones which are new occurrences from the Brazilian coast, and one that is new, up to now unknown to science; ● Discuss the taxonomy of some genera of Thyasiridae, emphasizing the importance of shell characters that are used to distinguish their species.

MATERIALS AND METHODS Sampling area The study areas consist on Southeastern regions of Brazil: São Paulo, Rio de Janeiro and Espírito Santo States. This is a high economical interest littoral area, where two of them are the most extensible and important petroleum platforms are located: the Campos and Santos Basin. Campos Basin extends from Espírito Santo to Rio de Janeiro States (Figure 1), totalizing 100,000 Km² length. During 2008 to 2010, PETROBRAS (Brazilian Petroleum Institution) executed two projects to collect materials: HABITATS and AMBES. HABITATS – Avaliação da Heterogeneidade Ambiental da Bacia de Campos (CENPES/PETROBRAS) had accomplished during two different periods: May to July/2008, when 8 transects in 12 isobaths were implemented, and March to July/2009, 12 cruise ships focusing on collect in depths of 25 to 3,000m in Rio de Janeiro coast. In addition, Espírito Santos coast, two transects between two canyons in depths varying of 400 to 1,300m (see Figure 1). AMBES – Caracterização Ambiental da Bacia do Espírito Santos e extremo norte da Bacia de Campos had accomplished in december/2010 to July/2013. Six transects were performed in 10 isobaths all in 14 cruise ships. The collections covered depths varying from 25 to 3,000m, including continental shelf, slope and canyons (Figure 1). The specimens were collected by Box-Corer and Van-Veen for each point and three replicas divided in three strata/segments (0-2, 2-5 and 5-10cm) were sampled. In the laboratory, samples washed using sieves of 1,000 and 500µm for macrofauna. Specimens fixed in formaldehyde 4% and, posteriorly, preserved in 70% ethanol and then destined to specialists including Prof. Dr. Flávio Dias Passos, sponsor of this work.

Figure 1 – Transects illustration of AMBES and HABITATS collections. (Red dots) - Ambes sample points and (Yellow dots) - Habitats sample points.

Santos Basin extends from Rio de Janeiro State (Cabo Frio - RJ) to Santa Catarina State (Florianópolis - SC), totalizing 350,000 km² of area. In that area, two landers placed on the sea bottom in two different stations, named 255 and 260 off São Paulo and Paraná States (Figure 2). These landers had pieces of bone and wood which were colonized by different animals along ten months were placed materials to experimental and control on deep sea floor. The visit for stations happened on July 2016 in agreement with Alucia Productions and Prof. Dr. Paulo Sumida and Prof. Dr. Michel Mahiques, both from Oceanographic Institution of University of São Paulo (IOUSP). The samples washed using a 300µm mesh, preserved in 70% ethanol and separated according to morphotypes. In 2017, Prof. Dr. Paulo Sumida contacted Prof. Dr. Flávio Dias Passos to identify in specific individuals of stations.

Figure 2 - Route of Alucia cruise in July/2016 to collect the samples from landers on Stations 255 and 260.

At laboratory, the specimens of Thyasira trisinuata, T. obsoleta, Parathyasira granulosa and Spinaxinus sp were observed under stereomicroscope Zeiss SteREO Discovery. V8 with attached camera, which was used to take photos on software AxioVision 4.8.2. Dry isolated valves and full individuals were submitted to Scanning Electron Microscope (SEM) JSM 5800LV of Scanning Electron Microscope Lab (LME) of Biology Institute of State University of Campinas, to obtain details of valves. They were fixed under an aluminum stub with glue carbon tape and methalized with gold by Sputter Balzers SCD-050, holding them 150 seconds with the equipment pulverizing. Available samples from national institutions: (i) ZUEC - BIV – Bivalvia collection of Museu de Zoologia da Universidade Estadual de Campinas “Adão José Cardoso” – Unicamp - Campus Barão Geraldo, Campinas, São Paulo, Brasil; (ii) MNRJ – Museu Nacional, Quinta da Boa Vista, São Cristóvão, Rio de Janeiro, Brasil;

(iii) UFRJ – Laboratório de Malacologia, Universiade Federal do Rio de Janeiro – Campus Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brasil; (iv) MUCIN – Museu de Ciências Naturais – Universidade Federal do Rio Grande do Sul, Imbé, Rio Grande do Sul, Brasil; Available samples from international institutions: (i) MCZ – Comparative Zoology Museum of Harvard University, Cambridge, Massachusetts, United States of America; (ii) NMNH – National Museum of Natural History of Smithsonian Institution, Washington, District of Columbia, United States of America; (iii) MNHN – Muséum National d’Histoire Naturelle, Paris, France. The specimens were observed under the stereomicroscope Laica, and photographed by Olympus DSX1000. Samples from NMNH – Smithsonian Institution and NMNH – Paris were not gold covered, and photographed by Philips XL-30 SEM at Scanning Electron Microscope and Image’s Lab - Smithsonian Institution. Type-materials that were not available to loan, only photos were used. They are from the institutions: (i) National Museum of Wales – National Association of Gales Museums, Cardiff, United Kingdom (photos available in the website: https://naturalhistory.museumwales.ac.uk/BritishBivalves/home.php); (ii) NHM – Natural History Museum, London, United Kingdom (photographs sent by Andreia Salvador).

Terminology Aiming to facilitate comprehension of descriptions and comparisons among examined species, the terminology used in this work followed Killeen & Oliver (2002a). These authors described the structures found in thyasirids shells in detail and defined some terms referring to the outlines of their valves. The Figures 3 and 4 summarize the main shell parts of thyasirids, which are applied in the descriptions of species examined herein. These species belong to three different genera, two of them considered as subgenera of Thyasira in some papers (e. g. Payne & Allen, 1991; Killeen & Oliver, 2002a; Dufour, 2005; Rodrigues et. al., 2008; Taylor & Glover, 2010;

Oliver, 2014; Taylor et. al., 2014; Huber, 2015; Oliver, 2015; Zanzerl & Dufour, 2017), but here considered as distinct genera, as discussed below.

Figure 3 – Structures terminology of external and internal views of a thyasirid – Thyasira trisinuata (d’Orbigny, 1846). A - External view of right valve. B - Internal view of right valve.

Figure 4 – Structures terminology of external dorsal and posterior views of a thyasirid – Thyasira trisinuata (d’Orbigny, 1846). A – External dorsal view. B – External posterior view.

RESULTS

In this work, the total of 1,587 valves were analyzed of four species of Thyasiridae: Thyasira trisinuata (720 valves), Thyasira obsoleta (743 valves), Parathyasira granulosa (124 valves) and Spinaxinus sp (200 valves) (see Table 1). Those species were sampled in the southern coast of Brazil by two projects of Petrobrás, HABITATS and AMBES, and one named ALUCIA, due to collaboration with Prof. Dr. Paulo Sumida. Beside of the collected materials, comparative samples were used from the scientific collections of National Museum of Natural History and Museum Support Center from Smithsonian Institute, totalizing 4,415 valves examined including the type-material; Muséum National D’Histoire Naturelle totalizing 196 valves; Museum of Comparative Zoology totalizing 1,293 valves examined; and Natural History Museum of London totalizing 8 valves as photos of type- material.

Taxonomy

Genus Thyasira Lamarck, 1818

Type - species: Tellina flexuosa Montagu, 1803, originally described based on material from Falmouth Harbor, Cornwall – England, United Kingdom, without illustrations (Allen, 1958; Killeen & Oliver, 2002a). A picture of the syntype was furnished by Oliver et al. (2017, pp. 384; fig. 30 – EXEMS Moll3894. Diagnosis: The diagnosis adopted in the present work is based on and summarized from Payne & Allen (1991), Coan et al. (2000), Killeen & Oliver (2002a), Oliver & Sellanes (2005), Coan & Valentich-Scott (2012), Astrom et al. (2017), focusing on shell morphology.

Shells usually varying from 1.5 to 27mm in length, fragile. Outline oval to oblique. Posterior margin sinuated; anterior margin truncated or angulated. Hinge weak. Right valve without cardinal

tooth; pseudotooth or cardinal tubercle usually present fitting in a respective depression on left valve. External surface with weak commarginal lines. White.

Remarks: Thyasira Lamarck, 1818 is the richest genus of Thyasiridae with 61 living species distributed in ten different subgenera. The existence of subcategories for this genus was firstly proposed by Dall (1901), who restricted Thyasira for species resembling Tellina flexuosa Montagu, 1803, its type-species. Then, Thyasira trisinuata (d’Orbigny, 1846), T. biplicata (Philippi, 1836), T. flexuosa Montagu, 1803, T. gouldii (Philippi, 1845) and T. sarsi (Philippi, 1845) are included in that restricted category, due to their higher shell outline, the presence of submarginal sulcus with auricle projection and sunken posterior sulcus (Killeen & Oliver, 2002a). Meanwhile, the species that do not correspond to the latter characteristics is placed in “Thyasira lato sensu” (e.g. Payne & Allen, 1991; Killeen & Oliver, 2002a; Oliver & Sellanes, 2005; Astrom et al., 2017). Thyasira ls includes Thyasira obsoleta (Verrill & Bush, 1898), Thyasira succisa (Jeffreys, 1876) and Thyasira atlantica Payne & Allen, 1991 due to their elliptical shell outline, minute size (less than 5mm) and non-sulcate posterior sulcus.

Independent of the adopted decision - the maintenance of subgenera for the genus Thyasira or its splitting in distinct genera – based on tenuous morphology differences, a confusion and instable classification still remains (Payne & Allen, 1991; Oliver & Killeen, 2002a; Oliver & Sellanes, 2005; Astrom et al., 2017). Huber (2015) believes that the subcategories should be treated as separated genera. In this work, both subcategories will be considered, thus, Thyasira trisinuata (d’Orbigny, 1846) as Thyasira stricto sensu and Thyasira obsoleta (Verril & Bush, 1898) as T. lato sensu.

Thyasira trisinuata (d’Orbigny, 1846) - Figures 5 and 6

Type species: Lucina trisinuata d’Orbigny, 1846.

Type locality: Martinica and Guadalupe.

Examined type material: 2 valves. Natural History Museum of United Kingdom: NHMUK Nº 1854.10.4.566 (Figure 5).

Examined materials: 360 specimens (720 valves) in 119 samples (see Table 1). ZUEC - BIV all collected in Campos Basin, off Rio de Janeiro and Espírito Santo States, Brazil, by “HABITATS Project”: Continental Shelf – ZUEC – BIV 5746, HAB 11, sta G5R1 (22º 6' 10,670" S, 40º 3' 6,481" W), 24/ii/2009, 154m [2 valves]; ZUEC - BIV #5746, HAB 13, sta D3R1 (22º 19' 32,030" S, 40º 37' 18,991" W), 15/iii/2009, 75m [2 valves]; ZUEC - BIV #5748, HAB 13, sta H5R1 (21º 42' 37,461" S, 40º 8' 59,804" W), 09/iii/2009, 147m [2 valves]; ZUEC - BIV #5750, HAB 13, sta I4R3 (21º 9' 9,310" S, 40º 16' 5,377" W), 07/iii/2009, 101m [2 valves]; ZUEC - BIV #5747, HAB 13, sta H4R3 (21º 42' 53,677" S, 40º 10' 16,159" W), 09/iii/2009, 99m [2 valves]; ZUEC - BIV #5733, HAB 16, sta G4R2 (22º 3' 39,049" S, 40º 6' 59,816" W), 06/vii/2009, 90m [2 valves]; ZUEC - BIV 5752, HAB 16, sta H3R1 (21º 43' 10,796" S, 40º 11' 30,783" W), 07/vii/2009, 71m [2 valves]; ZUEC - BIV #5754, HAB 16, sta H4R3 (21º 42' 54,432" S, 40º 10' 14,096" W), 07/vii/2009, 98m [2 valves]; ZUEC - BIV 5755, HAB 17, sta. I3R1 (21º 23' 38,083" S, 40º 15' 37,197" W), 21/vii/2009, 88m [2 valves]; ZUEC - BIV 5756, HAB 17, sta I5R1 (21º 23' 3,544" S, 40º 15' 9,352" W), 21/vii/2009, 140m [2 valves]. Malacological Laboratory of State University of Campinas (UNICAMP) - all collected in Campos Basin, off Rio de Janeiro and Espírito Santo States, Brazil, by “AMBES Project”: Slope – AMBES 3, STA CAN D5R3 (-39,04° long, -19,5° lat), nd, 374m [2 valves]; AMBES 5, sta B5R1 (-39,89° long, -20,58° lat), nd, 382m [4 valves]; AMBES 5, sta B5R3 (-39,89° long, -20,58° lat), nd, 382m, [2 valve]; AM0BES 5, sta C5R1 (- 39,80° long, -20,23° lat), nd, 416m [4 valves]; AMBES 6, sta E4R3 (-38,17 long, -19,60 lat), nd, 145m [4 valves]; AMBES 6, sta E4R1 (-38,17 long, -19,60 lat), nd, 145m [6 valves]; AMBES 6, E4R2 (-38,17 long, -19,60 lat), nd, 145m [2 valves]; AMBES 6, sta CANW N5R1 (-39,59° long, - 19,82° lat), nd, 352m [4 valves]; AMBES 11, sta B5R1 (-39,89° long, -20,58° lat), nd, 382m [4 valves]; AMBES 11, sta B5R3 (-39,89° long, -20,58° lat), nd, 382m [6 valves]; AMBES 11, sta C5R1 (-39,80° long, -20,23° lat), nd, 418m; AMBES 11, sta D5R3 ( ), nd, [4 valves]; AMBES 12, sta D5R1 (-39,50° long, -19,77° lat), nd, 431 [2 valves]; AMBES 12, sta E4R2 (-39,17° long, - 19,60° lat), nd, 142m [2 valves]; AMBES 12, sta G5R2 ( ), nd, [2 valves]; AMBES 12, CAN D4R2 (-39,05° long, -19,53° lat), nd, 163m [4 valves]; AMBES 12, CANW N4R2 (-39,60° long, -19,81° lat), nd, 181m; AMBES 12, sta CANW N4R3 (-39,60° long, -19,81° lat), nd, 181m [2 valves]; AMBES 12, sta CANW N5R1 (-39,59° long, -19,82° lat), nd, 363m [4 valves]; AMBES 12, sta CANW N5R2 (-39,59° long, -19,82° lat), nd, 363m [6 valves]. Continental Shelf – AMBES 7, sta A4R1 (-40,23° long, -21,06° lat), nd, 142m [4 valves]; AMBES 7, sta A4R2 (-40,23° long, -21,06°

lat), nd, 142m [10 valves]; AMBES 7, sta A4R3 (-40,23° long, -21,06° lat), nd, 142m [6 valves]; AMBES 14, sta C1R2 (-40,14° long, -20,16° lat), nd, 21m [2 valves]; AMBES 7, sta F2R1 (- 39,14° long, -18,87° lat), nd, 34m [2 valves]; AMBES 7, sta F2R3 (-39,14° long, -18,87° lat), nd, 34m [2 valves]; AMBES 7, sta F3R1 (-39,10° long, -18,89° lat), nd, 43m [6 valves]; AMBES 7, sta F3R2 (-39,10° long, -18,89° lat), nd, 43m [32 valves]; AMBES 7, sta F3R3 (-39,10° long, - 18,89° lat), nd, 43m [12 valves]; AMBES 7, sta G2R1 (-39,15° long, -18,60° lat), nd, 30m [12 valves]; AMBES 7, sta G3R1 (-38,92° long, -18,68° lat), nd, 44m [16 valves]; AMBES 7, sta G3R2 (-38,92° long, -18,68° lat), nd, 44m [18 valves]; AMBES 7, sta G3R3 (-38,92° long, -18,68° lat), nd, 44m [20 valves]; AMBES 13, sta G2R3 (-39,15° long, -18,60° lat), nd, 28m [2 valves]; AMBES 13, sta G2R2 (-39,15° long, -18,60° lat), nd, 28m [2 valves]; AMBES 13, sta G3R1 (- 38,92° long, -18,68° lat), nd, 44m [6 valves]; AMBES 13, sta G3R2 (-38,92° long, -18,68° lat), nd, 44m [4 valves]; AMBES 13, sta G3R3 (-38,92° long, -18,68° lat), nd, 44m [32 valves]; AMBES 14, sta A2R1 (-40,38° long, -21,05° lat), nd, 34m [2 valves]; AMBES 14, sta A4R1 (-40,23° long, -21,06° lat), nd, 147m [12 valves]; AMBES 14, sta A4R2 (-40,23° long, -21,06° lat), nd, 147m [8 valves]; AMBES 14, sta A4R3 (-40,23° long, -21,06° lat), nd, 147m [4 valves]; AMBES 14, sta F3R1 (-39,10° long, -18,89° lat), nd, 43m [2 valves]; AMBES 14, sta F3R2 (-39,10° long, -18,89° lat), nd, 43m [16 valves]; AMBES 14, sta F3R3 (-39,10° long, -18,89° lat), nd, 43m [4 valves]. B- CO_PPM#8/14, [4 valves]; B-CO_PPG1#4/14, [2 valves]; B-CO_P65_2015, [2 valves]. MNRJ – MNRJ 29507, nd [2 valves]; MNRJ 29498, nd, 600m, [6valves]; MNRJ 27627, nd [4 valves]; MNRJ 27610, nd [2 valves]; MNRJ 27635, nd [4 valves]. MUCIN – MUCIN 7, Revizee, sta 6539, nd [8 valves]; MUCIN 24, Revizee, sta 6839, nd [113 valves]; MUCIN 7, Revizee, 6839, nd [15 valves]. MNHN – Paris – total of 12 samples collected in Martinique by “Madibenthos Project” and 18 samples collected in Guadalupe by “Karubenthos Project”. Madibenthos – sta AD276, Baie de Fort-de-France, nd, 60m [13 valves]; AD243, Presqu’ille de la Caravelle, nd, 60m [7 valves]; AS411, E le Vauclin E Pointe du Fort, nd, 9m [1 valve]; AD251, N Loup Ministre, nd, 60m [19 valves]; AD611, Schoelcher, nd, 57m [3 valves]; AD279, Schoelcher, nd, 80m [5 vavles]; AD287, Bellefontaine – SO Centrale EDF, nd, 60m [12 valves]; AS572, Baie de St. Pierre – Epave du Rouraima, nd, 44 – 47m [1 valve]; AD256, NE Le Lorrain, nd, 49m [38 valves]; AD242, Presqu’ille de la Caravelle, nd, 60m [36 valves]; AD610, Schoeler, nd, 90m [8 valves]; AN292, Baie de Fort-de-France, nd, 75m [1 valve]. Karubenthos – GD25, Grand Cul-de-Sac Marin Point Louis, nd, 160m [2 valves]; GD08, Basse-Terre, nd, 35m [5 valves]; GD33, Grand Cul-de-Sac

Marin, nd, 130m [1 valve]; GD14, Besse-Terre – Anse à la Barque, nd, 10m [1 valve]; GD01, Grand Cul-de-Sac Marin, nd, 80m [2 valves]; GD36, Grand Cul-de-Sac Marin, nd, 65m [2 valves]; GD09, Besse-Terre – Ilete Bouillante, nd, 40m [1 valve]; GN18, Besse-Terre – Point-Noire, nd, 40m [8 valves]; GD10, Basse-Terre Pointe Nord Baie de Bouillante, nd, 54m [6 valves]; GD31, Grand Cul-de-Sac Marin – Port-Louis, nd, 85m [5 valves]; GD55, Grand Cul-de-Sac Marin, nd, 85m [1 valve]; GD12, Basse – Terre Anse à la Barque, nd, 45m [5 valves]; GD04, Grand Cul-de- Sac Marin, nd, 70m [4 valves]; GD26, Grand Cul-de-Sac, nd, 60m [4 valves]; GD15, Au large Anse à la Barque, nd, 50m [9 valves]; GN08, Grand Cul-de-Sac, nd, 155m [1 valve]; GD03, Grand Cul-de-Sac Marin, nd, 50m [1 valve]; GN01, Grand Cul-de-Sac, nd, 80m [1 valve]. USNM – Smithsonian Institution: Gulf of Mexico: USNM 157878, sta 2404, nd, 110m [2 valves]; Puerto Rico: USNM 108948, sta 134, nd, 55m [5 valves]; Barbados: USNM 503435, sta 89, nd, 183m [1 valve]; USNM 503436, sta 39, nd, 183m [1 valve]; USNM 503437, sta 48, nd, 172m [1 valve]; USNM 503438, sta 40, nd, 165m [1 valve]; North Carolina: USNM 38404, sta 2112, nd, 27m [1 valve]; USNM 92591, sta 2597, nd, 27m [1 valve]; USNM 92597, sta 2610, nd, 40m [12 valves]; USNM 92595, sta 2607, 33m, 5 valves; USNM 92596, sta 2608, 40m, 6 valves; USNM 94190, sta 2611, nd, 57m [4 valves]; USNM 92598, sta 2612, nd [1 valve]. No locality specified: USNM 430088, sta 104, nd, 91m [1 valve].

Geographic distribution: Abbott (1974), Rios (1985, 1994, 2009), Payne & Allen (1991) and Mikkelsen & Bieler (2008) recorded this species to Atlantic and Pacific Oceans. They also highlight the bathymetric range varying from 20 to 400m depth, a shallow water species.

T. trisinuata has been recorded from the Atlantic Ocean by many authors (e.g. Abbot, 1974; Rios, 1985, 1994, 2009; Payne & Allen, 1991; Mikkelsen & Bieler, 2008), from where it has been considered widely distributed in the Americas, having its northern limit in the Nova Scotia (Eastern Canada) and southern in the State of Rio Grande do Sul (south Brazil). Available museum specimens from the North American Atlantic Coast were examined, and some of them proved to be erroneously identified as this species (Table 2). Based on this, it is here suggested that T. trisinuata has in fact a more restricted distribution in the northwestern Atlantic: in the USA its occurrence could be confirmed for the North Carolina and Florida, apart from the places along the Gulf of Mexico; further to the north, lots from Massachusetts, New Jersey, Maine and Nova Scotia are all from other species, as T. biplicata, T. flexuosa and T. gouldi. In the Central America and

Caribbean, its occurrence could be verified by lots from Porto Rico, Barbados, Martinique and Guadalupe. In the Brazilian coast, it has been collected in the southeastern and southern, confirming Rio Grande do Sul as its southeastern limits of distribution in the Atlantic America.

This species is also registered from the Pacific Ocean: Alaska to San Diego (USA) in American coast, and in the Korean coast (Dall, 1901; Payne & Allen, 1991). Some available Pacific lots were examined and reidentified as T. tomeana (Dall, 1901) or T. barbarensis (Dall, 1890) after comparison with their type-species; then, it suggests a reevaluation of occurrence of the species on Pacific Ocean.

Diagnosis: midline umbones. Dorso-anterior margin short and slightly inclined. Lunule margin in “L” form. Anterior margin truncated. Ventral margin rounded and without angulation. Weak hinge; right valve with triangular pseudotooth fitting in respective depression on left valve. White valves.

Redescription: Shell up to 4.4mm in length and 4.5mm in height (Fig 5, A and B). Equivalve. Equilateral. Inflate. Outline equilateral oval–polygonal (Killeen & Oliver, 2002a). Umbones prosogyrous on midline. Prodissoconch varying from 108 to 166µm in length; its sunken limits surrounded by a belt; wrinkles absent (Fig. 5, M and N).

Dorso-anterior margin short and slightly inclined, with a long lunule margin, rounded concave in a weak “L” form; strongly truncate in the confluence with the anterior margin, this truncate taking 1/3 to ½ length of this margin. Anterior margin inclined and slightly rounded ventrally, continuous with the rounded ventral margin. Posterior region sinuated with two sunken sulci, submarginal and posterior (Fig 5G). Auricle projection high and short, taking about ½ of the length of the sunken submarginal sulcus (Fig. 5, H,to F); marginal sinus strongly concave. Posterior sulcus sunken, forming a rounded, concave posterior sinus (Fig 5, H to F). External surface with weak commarginal lines. Periostracum present and thin with rows of microstructures (as pustules) in a commarginal pattern (Fig 5, B and D). White shell with or without orange/ferrugineous marks on posterior and anterior margins.

Escutcheon sunken (Fig 5H). Ligament partially internal; ligament scar sunken and straight. Hinge weak (Fig 5, I to L). Right valve with rounded triangular pseudotooth (Fig 5K); respective depression present on left hinge (Fig 5L). Internal surface white and opaque. Adductor muscle

scars weakly impressed. Anterior adductor muscle scar roundly elongated and divided in three bundles. Posterior adductor muscle scar elliptical–oval. Retractor muscle scars not impressed.

Growth changes: The shells from 0.7 to 1.5mm in length (Fig 5C) are elliptical outline because of the anterior region be more expanded. They have a rounded angulation between dorso- anterior and anterior margins and the lunule margin is straight. From 1.6 to 2.5mm (Fig 5D), the valves have equal length and height and the truncate starts to form; the lunule is still straight. Then, in shells larger than 2.5mm in length (Fig 5, E and F), the ventral-dorsal axe starts to develop, ending in the higher adult shells, with the strong truncate anterior margin and the “L” lunule margin. The posterior region is sunken sinuated even in minute shells, and the auricle projection grows directly with the shell size. The pseudotooth is present in all right valves examined. In the north and south limits of its geographical distribution, the shells are larger and even higher, also presenting a tenuous angulation on ventral margin.

Variation: There isn’t any variation observed among the examined specimens from same locality and depth.

Remarks: Thyasira trisinuata has been inside of a complex with another Thyasira species of the Atlantic Ocean. It closely resembles to: (1) the juveniles of Thyasira biplicata (10mm length) and Thyasira sarsi (27mm length) (Fig 13 and 16, respectively), the largest species; (2) adults of same size species, Thyasira flexuosa (8mm length) (Fig 14); and, (3) adults of Thyasira gouldi (4mm length) (Fig 15), the smallest species. Those comparisons and observations made based on my own examination of available lots of each species compiling with literature information.

Comparing to Thyasira trisinuata, Thyasira biplicata is bigger, the adults may measure 10mm in length and 14mm in height (own observations). Both species have the posterior region sinuated, but the auricle of T. biplicata is lower (Fig 13E) and slightly longer than that of T. trisinuata (Fig 5, E and F). In addition, the second and third waves of T. biplicata are more prominent, strongly demarcated (Fig 13E). The sunken posterior sulcus forms a concave posterior sinus. Distinct from T. trisinuata which has a truncate confluent between dorso-anterior and anterior margins, Thyasira biplicata has two angulations (forming an obtuse angle): (i) the dorso- anterior and anterior margins; and (ii) the postero-ventral and ventral margins. Both species have a pseudotooth in right valve, but in T. biplicata it is more pointed, prominent and triangular, with

a sulcate line present in the middle (Fig 13, H and I). Moreover, the periostracum of T. biplicata (Fig 13, K and L) does not have microstructures such as the one of T. trisinuata (Fig 6, B and D). The larval shell size is similar in these two species, but in T. biplicata there is a weak radial striate ornamentation (Fig 13M), which is absent in T. trisinuata (Fig 5, M and N).

The juveniles of Thyasira sarsi (Fig 16E) resemble the medium or adult individuals of T. trisinuata (Fig 5, C and D), even though the size of the adults species are strongly different, the former reaching 27mm, and the latter is not transposing 4.5mm in length. The first species juveniles have one sunken sulcus on posterior region, while T. trisinuata has two. There is an obtuse angle confluent the margins dorso-anterior and anterior margins (Fig 16, F and G), while in T. trisinuata it is truncated (Fig 5, E and F). Moreover, there is one more angulation on postero-ventral margin of T. sarsi (Fig 16, F and G), which is absent in T. trisinuata (Fig 5, E and F). Apart from the size, the adults of these species are easily distinguished by the rounded outline of T. sarsi (Fig 16, A to G). Both have microstructures on external surface, the ones of T. sarsi being rounded (Fig 16N), close to each other and randomly distributed (Oliver et al, 2013). In addition, Thyasira sarsi has no pseudotooth and corresponding depression in any of both valves (Fig 16, K and L); its juveniles have a triangular peseudotooth on left valve and respective depression on right valve (own observation). The larval shell size is a quite larger in T. trisinuata (130 to 166µm) (Fig 5, M and N) than in T. sarsi (110 to 130 µm), both having sunken edges surrounding by a belt (Fig 16O).

Thyasira trisinuata distinguished from Thyasira gouldii by the truncate anterior margin, only present in the former species (Fig 15, C and D); in Thyasira gouldii, the lunule is depressed by marginal ridges forming only a subtruncate anterior margin (Fig 15G). Both species are sinuated in the posterior region, but T. gouldii has the auricle projection less prominent and a weak submarginal sulcus (Fig 15, C and D); related to this, the marginal sinus is replaced by straight margin. The hinge is weak and there is a rounded pseudotooth on right valve and respective depression on left one (Fig 15, E and F). There is not any microstructure on external surface (Fig 15K) contrary to the features observed in T. trisinuata (Fig 6, B and D). In addition, the larval shell of T. gouldii varies from 170 to 190µm in length without striate sulci with a more prominent sunken belt surrounding it (Fig 15J)

Recorded from the same localities, except for Eastern Atlantic waters, Thyasira trisinuata (Fig 5, A, B and E, F) closely resembles Thyasira flexuosa (Fig 14, A, B and F). These two are

distinguished for longer (1/3 of submarginal length), short and less prominent auricle projection, rounded and slightly prominent second wave of the latter species. In Thyasira flexuosa there are two obtuse angle confluents in: (i) dorsal-anterior to anterior margins and (ii) middle to anterior region on ventral margin; these two are visible in juveniles (Fig 14F). The outline of species is similar, but T. flexuosa is more rounded. Thyasira trisinuata (Fig 5K) and T. flexuosa (Fig 14J) have a developed pseudotooth on right valve. However, the first species is more inflated, pointed triangular while T. flexuosa is smaller and rounder. There are microstructures on external surface of T. flexuosa such as T. trisinuata, however, T. flexuosa’s are rounded features with no organic net linking on their basal (Fig 14, K and L), they are similar of T. sarsi (Fig 16N). Some of available specimens analyzed from National Museum of Natural History and Museum Support Center – Smithsonian Institution identified as T. trisinuata were re-identified as T. flexuosa (Table 2). Based on examined specimens localities of the latter species, it is restrict to northern of North American coast, such as T. gouldii, even though, both registered to continental shelf and slope.

Comparing the available samples of those five Thyasira species with syntype materials from Eastern Pacific Ocean infer that Thyasira trisinuata and T. flexuosa, previous registered on that location, could also be misidentify to Thyasira barbarensis (Dall, 1890) (USNM 74299 – Syntype) (Fig 17, S to V) – described to Baja California, and Thyasira tomeana (Dall, 1901) (USNM 108907 – Syntype) (Fig 17, W to X) – described to Chile Coast. Both species are resembling to available images of Coan et al., (2000) and Coan & Valentich-Scott (2012) which are identified in these works as T. flexuosa what is different of the same species syntype presented by Oliver et al., (2017). Then, the images presented by Coan and Valentich-Scott are similar of T. barbarensis. T. trisinuata is more similar to T. tomeana but they differ because of presence of the auricle projection and less prominent truncate on anterior margin of T. tomeana. Therefore, the observations made suggest an investigation of occurrence of T. trisinuata to Pacific American Coast.

Figure 5 – Thyasira trisinuata (d’Orbigny, 1846). A - B – Lucina trisinuata d’Orbigny, 1846, NHMUK 1854.10.4.566, lectotype, Guadaloupe: (A) left valve on external view and (B) – left valve on internal. C – F – growth serie: (C) external surface of right valve, juvenile from (Ambes 7 G3R1), (D) external surface of right valve, intermediate (Ambes 7 F3R21), (E) external surface of right valve, adult (Habitats 17 I3R1) and (F) external surface of left valve, adult (Habitats 17 I3R1). (G) posterior view (Habitats 17 I3R1). (H) dorsal view (Habitats 17 I3R1). I – J – internal surface: (I) left valve and (J) right valve (both from MUCIN Draga 24_5). K – L – hinge view: (K) SEM right hinge (Ambes 7 A4R2) and (L) SEM of left hinge (Ambes 7 F3R1). M – N – SEM of larval shell: (M) SEM of right and left larval shell articulated (Ambes 7 G3R1) and (N) SEM of larval shell of left valve (Ambes 7 F3R1).

Figure 6 – Thyasira trisinuata (d’Orbigny, 1846). (A) SEM external surface of left valve (Ambes 7 G3R1); (B) SEM of periostracum microstructures in postero-ventral region of left valve in x300 zoomed (Ambes 14 A4R2); (C) SEM of external surface of left valve ventral region in GSE detector with x36 zoomed (KARUBENTHOS GD15); (D) SEM periostracum microstructure of ventral region in GSE detector with x119 zoomed (KARUBENTHOS GD15).

Thyasira obsoleta (Verrill & Bush, 1898) – Figures 7 and 8

Type species: Cryptodon obsoletus Verrill & Bush, 1898

Type locality: off Martha’s Vineyard, Massachusetts, USA.

Examined type material: 2 valves. National Museum of Natural History of Smithsonian Institution: USNM Nº 159886 (Figure 7).

Examined materials: 383 specimens and 1 valve (767 valves) in 29 samples (see Table 1). Malacological Laboratory of State University of Campinas (UNICAMP) – all collected in Campos Basin, off Rio de Janeiro and Espírito Santo States, Brazil, by “AMBES Project”: Slope - AMBES 6, sta CAN WN N4R1 (-39,60° long, -19,81° lat), nd, 124m [10 valves]. Continental Shelf - AMBES 7, sta A4R1 (-40,23° long, -21,06° lat), nd, 142m [4 valves]; AMBES A4R3 (-40,23° long, -21,06° lat), nd, 142m [2 valves]; AMBES 7, sta D4R3, nd [2 valves]. MNRJ – all collected in Campos Basin, off Rio de Janeiro and Espírito Santo States, Brazil, by “AMBES Project”: MNRJ 29496 (23°16’43”S, 40°59’50,8”W), 19/viii/2009, 600m [39 valves]; MNRJ 29441, nd, 96 valves; MNRJ 29428, nd [28 valves]; MNRJ 29420, 31/viii/2013 [80 valves]; MNRJ 29445, nd [8 valves]; MNRJ 29457, nd [12 valves]; MNRJ 29451, nd [26 valves]; MNRJ 29436, nd [74 valves]; MNRJ 29481, nd [48 valves]; MNRJ 29493, nd [54 valves]; MNRJ 29473, nd [40 valves]; MNRJ 29460, nd [120 valves]; MNRJ 29504, nd [20 valves]; MNRJ 29429, nd [2 valves]; MNRJ 294504, nd [12 valves]; MNRJ 29498, nd [4 valves]. Malacological laboratory of Federal University of Rio de Janeiro (UFRJ) - all collected in Campos Basin, off Rio de Janeiro and Espírito Santo States, Brazil, by “HABITATS Project”: HAB 135, nd [26 valves]; HAB 141, nd [8 valves]; HAB 149, nd [18 valves]; HAB 152, nd [6 valves]; HAB 248, nd [26 valves]; HAB 326, nd [2 valves].

Geographic distribution: Payne & Allen (1991) and Killeen & Oliver (2002a) recorded this species from Western and Eastern Atlantic Ocean. They also highlighted the bathymetric range varying from 43 to 2900m depths.

In Western Atlantic, the records of Thyasira obsoleta are from the North American Basin, and in the Eastern, this species is known from Norway, West European, Sierra Leone and Angola Basins, with a wide bathymetric distribution from 500 to 2900m (Payne & Allen, 1991). This species has been collected in the southeastern Brazilian coast from 124 to 600m. It was never

registered from other places south to Massachusetts. None of examined available museums samples had specimens of this species.

Diagnosis: umbones moderately dislocated to the posterior region. Inequilateral obliquely ovate shell outline. Dorso-anterior margin short and slightly straight. Lunule margin with boundaries ridges. Anterior margin truncated and antero-ventral margin with an angulation. Posterior margin bisinuated with a short auricle projection. Weak hinge; both valves without pseudoteeth. White valves.

Redescription: Shell up to 3.0mm in length and 2.5mm in height, inflate, equivalve, inequilateral. Outline inequilateral obliquely-ovate, pyriform, with the antero-ventral region slightly expanded. Umbones prosogyrous and moderately positioned in the posterior region. Prodissoconch varying from 140 to 150µm; its sunken limits surrounded by a belt; radial wrinkles present.

Dorso-anterior margin short and slightly inclined, well-marked by a truncate in the confluence with anterior margin. Lunule slightly sunken, with boundary ridges forming a “crest” in the margin. Anterior margin slightly rounded or straight, forming an angulation in the confluence with the ventral margin. Posterior region sinuated with two sulci. Escutcheon slightly sunken. Ligament internal taking ½ of auricle length. Auricle projection short, low and slightly prominent, taking about 1/3 to ½ of sunken submarginal sulcus; marginal sinus slightly concave. Posterior sulcus weakly sunken forming an inclined posterior sinus. External surface with weak commarginal lines. Periostracum thin without microstructures. White shell with or without orange/ferrugineous marks on posterior and anterior margins.

Weak hinge. Right and left valves without pseudoteeth. Internal surface brightly white. Anterior and posterior adductor muscle scars weakly impressed, the anterior roundly elongate, the posterior elliptical-oval. Retractor muscle scars not impressed.

Growth changes: The shells from 0.7 to 1.5mm in length are elongate, with a more expanded anterior region; the posterior sinuate region is slightly prominent. Shells larger than 2.5mm, the sinuate of posterior region and margin is demarcated and prominent, just as the truncate and lunule boundary ridges. In addition, the anterior-ventral dorsal axe starts to develop, forming in the higher larger shells.

Variations: There are two main variations based on examined specimens outline: one, higher shells, which the ventral-dorsal axe is longer than the postero-anterior; and second, with more rounded shells. In the first, there is an angulation in antero-ventral margin and the anterior region is more expanded and prominent; the second fold of posterior margin is prominent angulated. Moreover, the lunule boundaries ridges are strongly sunken forming a higher, prominent and short crest. In the rounded forms, the auricle projection and second fold of posterior region are more rounded and not angulated; anterior region expanded but with antero-ventral angulation less prominent; the boundaries ridges less sunken, then lower and longer crest; and less prominent truncate. There is no correlation of depth or specific locality to each shell form. Specimens examined from or near of type-locality are similar to rounded shell form.

Remarks: Thyasira obsoleta has been placed in the genus Thyasira but its shell morphology does not exactly match the one of Thyasira flexuosa. This species and some others, like Thyasira succisa and T. atlantica, are all considered by Payne & Allen (1991) and Killeen & Oliver (2002a) as Thyasira sensu lato. It is a pending question regarding the exact definition of shells characters of Thyasira and related genera.

Thyasira obsoleta (Fig. 7, A to B and G to J) has been confounded with other Atlantic species, like Thyasira succisa (Jeffreys, 1876) (Fig. 17, A to D), Thyasira atlantica Payne & Allen, 1991 (Fig 17, E to H) and Thyasira gouldii (Fig 15, A to D), but based on examination of the collected and available museum samples of all species, comparisons could be made and reveal that they are distinct.

Thyasira obsoleta is distinguished from Thyasira succisa, because the absence of the pseudotooth on the right valve hinge in the former species (Fig 8, A to D), which also has more rounded outline (Fig. 7, A and B, J to R) compared to Thyasira succisa (Fig. 17, C and D). Thyasira succisa (Fig. 17, A and B) has a lower and less prominent auricle projection than Thyasira obsoleta (Fig 7, A and B, J). Both species have a sinuous posterior region, but in T. succisa the sulci are weak (Fig. 17, A and B). Even though Killeen & Oliver (2002a) pointed out the presence of boundary ridges surrounding the lunule margin in Thyasira succisa, this feature was not observed on examined specimens including the lectotype (USNM 61973 – see Figure 17, A and B). These ridges are more evident in Thyasira obsoleta (Fig. 8, F and I and J), where the dorso-anterior margin is truncated in the confluence with the anterior margin; in Thyasira succisa these margins are more

continuous and uniformly rounded (Fig. 17, A and B). In Thyasira atlantica (NHMUK 1990041 - holotype) (Fig 17, E and F) the ridges surrounding the lunule are even less sunken, the anterior margin is expanded and not strongly angulated compared to T. obsoleta. Moreover, the auricle projection of the posterior margin is more pronounced in Thyasira obsoleta (Fig. 7J) than T. succisa (Fig. 17, A and B) and T. atlantica (Fig. 17, E and H).

The pyriform variation of Thyasira obsoleta might be misidentified as T. gouldi (Fig 15, A to D), as already discussed by Killeen & Oliver (2002b), this being a main problem in Massachusetts, where they co-occur. Comparing the shell outline, Thyasira gouldi is more rounded (Fig. 15, C and D) while in T. obsoleta the antero-ventral region is more expanded with a prominent angulation (Fig. 7, I to N). In addition, the auricle projection of Thyasira gouldi is longer and lower, the posterior sulcus is deeper (Fig. 15, C and D) and there is a pseudotooth on right valve (Fig. 15, E and F), contrary to T. obsoleta (Fig. 8, C and D). Both species have a truncate anterior margin, but in Thyasira obsoleta it is stronger and upper (Fig. 8J) than in T. gouldi (Fig. 15, C and D).

A striated pattern with a main radial wrinkles on the larval shell is here described for the first time to Thyasira obsoleta (Fig. 8E), this feature being difficult to observe because salt precipitation might be covering the umbones, which are also frequently eroded (Fig. 8F). The measurements of the prodissoconchs obtained by the SEM are similar to the ones furnished by Killeen & Oliver (2002a).

Figure 7 – Thyasira obsoleta (Verril & Bush, 1898). A - D – Cryptodon obsoletus (USNM 159886 - Lectotype): (A) – external view of left valve, (B) – external view right valve, (C) internal view of left valve, (D) internal view of right valve. (E) posterior view (UFRJ 152). (F) dorsal view (UFRJ 152). G – J – growth serie: (G) and (H) juveniles (MNRJ 29420), (I) intermediate specimen (MNRJ 29428) and (J) adult specimen (UFRJ 152). K – L – upright variation examples of the species: (K) (MNRJ 29441), (L) (MNRJ 29420), (M) (MNRJ 29481) and (N) (UFRJ 152); O – R – elongate variation examples of the species: (O) (UFRJ 152), (P) (MNRJ 29481), (Q) (MNRJ 29441) and (R) (UFRJ 149).

Figure 8 – Thyasira obsoleta (Verril & Bush, 1898). A – B – internal view: (A) left valve and (B) right valve (both MNRJ 29441). C – D – SEM of hinge view: (C) left hinge x80 zoom and (D) right view x90 zoom (both MNRJ 29411). E – F – SEM of larval shell: (E) larval shell of right valve x650 zoom and (F) articulated larval shell x500 (both MNRJ 29441). (G) SEM of external surface with salt precipitation on posterior and anterior regions (MNRJ 29441). (H) right valve highlighting posterior region salt precipitation, x85 zoom (MNRJ 29441). (I) posterior view also highlighting the salt precipitation x55 zoom (MNRJ 29441). J – K – SEM of periostracum microstructures: (J) postero-ventral region highlighting lack of periostracum microstructures with x150 zoom; (K) posterior-ventral region with x300 zoom, also highlighting the lack of periostracum microstructures (both MNRJ 29441).

Genus Parathyasira Iredale, 1930

Type species: Parathyasira resupina Iredale, 1930. This species was originally described based on material from New South Wales, off Port Kembla, Australia. Illustration present in pp. 29 figure 5 of Iredale (1930).

Diagnosis: The diagnosis adopted in the present work is based on and summarized from Iredale (1930), Payne & Allen (1991), Killeen & Oliver (2002a), Oliver (2014), Oliver et al. (2015) and Oliver & Rodrigues (2017), focusing on shell morphology.

Shells flattened, equivalve, ovate to ovate-rhomboidal in outline, with height and length mostly equal; anterior, ventral and/or posterior margins subacute. Umbones positioned in midline. Lunule margin “L” in form. Auricle projection absent. Submarginal and posterior sulci weak. Anterior margin slight truncate. Hinge weak. Right valve without cardinal tooth; pseudotooth or cardinal tubercle usually present, fitting in a respective depression on left valve. External surface white, with weak commarginal lines; thin periostracum with spinose microstructures.

Remarks: Parathyasira was first described as a valid genus, distinct from Thyasira, by Iredale (1930). Smith & Heppell (1990) and Payne & Allen (1991) adopted it as a subcategory of Thyasira due to tenuous differences distinguishing Parathyasira of others Thyasira subgenera (Killeen & Oliver, 2002a). However, Oliver (2014), Oliver et al. (2015) and Oliver & Rodrigues (2017) reconsidered that Parathyasira should be a genus, based on the observation that the presence of sculptures on external surface, which are observed in P. resupina Iredale, 1930 (type- species) and in some Atlantic species of the genus, like Parathyasira granulosa (Monterosato, 1874) (old A. granulosa) and P. subcircularis Payne & Allen, 1991.

Parathyasira granulosa (Monterosato, 1874) – Figure 9 and 10

Type-species: Axinus granulosus Monterosato, 1874

Type-location: Cape Santo Vito, Sicily, Italy.

Type material: Natural History Museum of London: BM(NH) nº 1885.11.5.933 – Syntype not examined.

Examined materials: 62 specimens (124 valves) in 22 samples (see Table1). Malacological Lab of Unicamp – all collected in Campos Basin, off Rio de Janeiro and Espírito Santo States, Brazil, by “AMBES Project”: Slope - AMBES 3, sta E5R3 (-39,17° long, -19,60° lat), nd, 352m [4 valves]; AMBES 6, sta CANNWN4R1 (-39,60° long, -19,81° lat), nd, 124m [2 valves]; AMBES 6, sta D4R2 (-39,50° long, -19,76° lat), nd, 121m [4 valves]; AMBES 6, sta E4R3 (-39,17° long, -19,60° lat), nd, 145m [4 valves]; AMBES 11, sta B5R3 (-39,89° long, -20,58° lat), nd, 382m [2 valves]; AMBES 12, sta D4R1 (-39,50° long, -19,76° lat), nd, 138m [12 valves]; AMBES, sta D4R2 (-39,50° long, -19,76° lat), nd, 138m [2 valves]; AMBES 12, sta D4R3 (-39,50° long, -19,76° lat), nd, 138m [2 valves]; AMBES 12, E4R1 (-39,17° long, -19,60° lat), nd, 142m [2 valves]; AMBES 12, sta CAN D4R2 (-39,05° long, -19,53° lat), nd, 163m [4 valves]. Continental Shelf - AMBES 7, sta A4R2, 2 valves; AMBES 7, sta D4R1, 2 valves, AMBES 7, sta D4R2, 2 valves; AMBES 7, sta F3R1 (-39,10° long, -18,89° lat), nd, 43m [2 valves]; AMBES 12, sta D4R1 (-39,50° long, -19,76° lat), nd, 138m [6 valves]; AMBES 12, sta D4R2 (-39,50° long, -19,76° lat), nd, 138m [8 valves]; AMBES 12, sta D4R3 (-39,50° long, -19,76° lat), nd, 138m [4 valves]. USNM – Smithsonian Institution: USNM 62030, Norway – Osterfiord, nd [1 valve]; USNM 61956, nd [13 valves]; USNM 633879, Norway, nd [16 valves]; no location specified: USNM 61979, nd [2 valves].

Geographic distribution: Jeffreys (1881), Dall (1901) and Killeen & Oliver (2002a) recorded this species for Mediterranean and Western and Eastern Atlantic Oceans. They reported a bathymetric range from 100 to 1800m depths.

In Mediterranean, the record of Parathyasira granulosa is from Sicily (Monterosato, 1874; Jeffreys, 1881); in the Eastern Atlantic Ocean, from Cannaries Islands (Spain), England and Norway (Jeffreys, 1881; Killeen & Oliver, 2002a); and in the Western Atlantic, from Gulf of Mexico and West Indies (Killeen & Oliver, 2002a). Moreover, specimens from the southeastern Brazilian coast have been misidentified as “Thyasira croulinensis” as discussed below; there remains a gap on the knowledge of its occurrence from the Central American Coast and from the north and northeastern Brazilian coasts.

Diagnosis: minute shell. Midline umbones. Lunule margin as “L” in form. Auricle projection absent. Submarginal sulcus weak sunken. Anterior margin slightly truncate. External

surface with weak sunken commarginal lines; periostracum thin with spinose microstructures. Hinge weak; both valves without pseudotooth.

Redescription: Shell length varying from 0.9 to 8.0mm, inflate, equivalve, equilateral. Outline equilateral ovate, with height and length mostly equals. Umbones prosogyrous, positioned on midline, bearing a high concentration of ferruginous precipitations. Prodissoconch varying from 140 to 170µm; its sunken limits surrounded by a belt; radial wrinkles absent; prodissoconch usually eroded near of boundaries.

Dorso-anterior margin short and slightly inclined, well-marked by a slight truncate in the confluence with anterior margin. Lunule weak sunken forming an “L” in the margin. Anterior margin slightly straight and marked by and angulation in the confluence with ventral margin. Ventral margin with an weak angulation in the midline region. Posterior region with two sulci. Posterior margin with one wave. Escutcheon sunken. Submarginal sulcus long and sunken without an auricle projection. Ligament pseudo-external, sunken and taking about ½ of submarginal sulcus length. Posterior sulcus weakly sunken forming a slightly rounded concave posterior sinus. External surface with weak commarginal lines. Periostracum thin with spinose microstructures on radial pattern. White shell with or without orange/ferruginous marks on posterior and anterior margins.

Weak hinge. Right and left valves without pseudoteeth. Internal surface opaquely white. Anterior and posterior adductor muscle scars weakly impressed, the anterior roundly elongate divided in two bundles, and the posterior elliptical-oval. Retractor muscle scars not impressed.

Growth changes: The juveniles are slightly more oval than the adults due to the expanded anterior region.

Variation: There is no significant variation among the examined specimens.

Remarks: Parathyasira granulosa was originally described as Axinus granulosus by Monterosato (1874) and then posteriorly transferred to the subgenus Parathyasira by Payne & Allen (1991) and Killeen & Oliver (2002a) now considered a separated genus, distinct from Thyasira. Parathyasira granulosa has the outline and spinose microstructures similar of Parathyasira resupina (Iredale, 1930).

Outline similarity of Parathyasira granulosa (Fig. 9C) is observed in other species like Parathyasira resupina and P. equalis (Fig. 17, Q and R), which are recorded from Australian coast and the western Atlantic, respectively. Parathyasira granulosa differs from P. resupina by the higher outline of the latter; apart from this, Parathyasira granulosa has a truncate confluent of dorso-anterior to anterior margins and it is longer and more abrupt (Fig. 9C) than the truncate of P. resupina. The latter species has an angulation on midline region of ventral margin, which there is none in P. granulosa (Fig. 9, A to C), and P. resupina has a sunken posterior sulcus while it is weak in P. granulosa (Fig. 9E). The holotype of Parathyasira equalis was examined (USNM 74302) (Fig. 17, Q and R), and there is no microstructure on the external surface, this being the main difference among this species and P. granulosa (Fig. 10, D to G). Moreover, the latter species has a less sunken posterior sulcus, which is demarcated in Parathyasira equalis; the submarginal sulcus is deeper in P. granulosa (Fig. 9, D to F) than P. equalis. There is a strong and short truncate on the anterior margin of the valves of P. equalis (Fig. 17, Q and R) while it is long and slightly rounded in P. granulosa (Fig. 9C). Part of the ligament in the latter species is visible from the outer view (Fig. 9, E and F) while in the P. equalis it is deeply sunken and not externally visible. Parathyasira biscayensis (Payne & Allen, 1991), also a species from the deep Atlantic, resembles P. granulosa, but differs by the shell outline, which is oblique with a prolonged antero- ventral region in the former species. In the anterior margin of Parathyasira biscayensis there is no truncate or subtruncate, and it is continuously rounded to ventral margin. Parathyasira biscayensis has a weak submarginal sulcus surrounding the escutcheon, forming a weak auricle projection (based on figure 40 of Payne & Allen (1991)) and weak posterior sulcus. Payne & Allen (1991) highlighted the similarity between Parathyasira granulosa and Thyasira subcircularis Payne & Allen, 1991 due to granulose external surface in radial rows. However, their shell outlines are different: Thyasira subcircularis is equilateral-subcircular while P. granulosa is oval-trigonal. In Brazilian waters, Parathyasira granulosa was identified as Thyasira croulinensis (Jeffreys, 1847) by Rios (1985, 1994, 2009) and Pimpão (2004). The specimens used by Rios (1985, 1994, 2009) were not available for examination, and the illustrations furnished by him are the same from Abbott (1974), which are also the same from Verrill & Bush (1898). However, when recording Cryptodon croulinensis, these latter authors highlighted the possibility of the specimens

were Thyasira gouldii and Thyasira dearborni (current Parathyasira dearborni) designated by Nicol (1965), an observation ignored by both Abbott (1974) and Rios (1985, 1994, 2009). In fact, the figures used by Verrill & Bush (1898) are probably from another species distinct from P. croulinensis. The samples identified as Thyasira cf. croulinensis by Pimpão (2004) were examined and re-identified as Parathyasira granulosa.

Figure 9 – Parathyasira granulosa (Monterosato, 1872). A - C - growth serie: (A) juvenile (Ambes 12 D4R2), (B) intermediate (Ambes 12 D4R2) and (C) adult (Ambes 7 D4R2). (D) dorsal view (Ambes 7 D4R2). (E) posterior view (Ambes 7 D4R2). F and G – internal surfaces view: (F) right internal surface and (G) left internal surface (both Ambes 12 CAND4R2, Slope); H and I – hinge view: (H) right hinge (Ambes 12 D4R2, Slope) and (I) left hinge (Ambes 12 D4R2, Continental Shelf).

Figure 10 – Parathyasira granulosa (Monterosato, 1872). A and B – larval shell: (A) eroted larval shell (Ambes 12 CAND4R2, Slope) and (B) less eroted larval shell (Ambes 12 CAND4R2, Slope). C – H – external surface hihglightling the periostracum microstructure: (C) left valve on external view (Ambes 12 CAND4R2, Slope). (D) central region of external surface of left shell highlighting the microstructures on lupe observation (Ambes 12 CAND4R2, Slope); (E) central region of external surface of left shell highlighting the microstructures on SEM observation (Ambes 12 D4R2, Continental Plataform); (F) ventral margin region highlighting the radial pattern of the periostracum microstructure on SEM (Ambes 12 D4R2, Continental Plataform); (G) ventral margin region highlighting the radial pattern of the periostracum microstructure on SEM with x800 zoomed (Ambes 12 D4R2, Continental Plataform).

Genus Spinaxinus Oliver & Holmes, 2006 Type species: Spinaxinus sentosus Oliver & Holmes, 2006. This species originally described based on material collected from 1160m depth off Vigo, Spain, by the sunken ship “Francois Vieljeux” (Oliver & Holmes, 2006). Diagnosis: The diagnosis adopted in this work is based on and summarized from Oliver & Holmes (2006), Oliver et al. (2013) and Oliver & Rodrigues (2017), focusing on shell morphology. Its species have equilateral, equivalve and white shells. Its outline usually moderate in size with a quadrangular outline. Anterior region expanded; posterior region with a sunken submarginal sulcus and a weak posterior sulcus, both forming a slight truncate in the posterior margin. Hinge weak without cardinal tooth; pseudotooth or cardinal tubercle absent in both valves. External surface with weak commarginal lines; thin periostracum with spinose microstructures in commarginal pattern. Remarks: Spinaxinus is the most recent genus of Thyasiridae described by Oliver & Holmes (2006). There are only four species known of this genus: Spinaxinus sentosus Oliver & Holmes, 2006, S. emicatus Oliver, 2013, S. phrixicus Oliver, 2013 and S. caldarium Oliver & Rodrigues, 2017, the first two recorded from the Atlantic Ocean, S. phrixicus from Pacific Ocean and the latter one from the Antarctic Ocean. Spinose microstructures on external surface were believed to be unique for this genus, a characteristic related to the name of this group. However, this feature has been observed in other species apart from Spinaxinus, such as Parathyasira granulosa (Fig. 10, D to G).

Spinaxinus new species - Figures 11 and 12 Type material: Holotype. Collected by ALUCIA Ship, off Paraná State, Brazil 26º36'S / 46º09'W, 550 m. Sample named “Bivalve #1, Bag Wash Alucia”. Dimensions: Length: 7.3mm; Height: 6.1mm. Examined material: all the 200 examined specimens are whole animals collected from one single place (see Table1). Diagnosis: flattened shell with moderate size, equivalve and quadrangular in outline (shell length longer than height). Umbones prosogyrous. Anterior margin pronounced, posterior margin

truncated. Auricle projection absent. Posterior sulcus sunken. External surface with weak commarginal lines; thin periostracum with spinose microstructures. Description: shell white, 0.9 to 7.3mm in length, and 0.7 to 6.1mm in height, flattened, equivalve. Outline quadrangular, with prosogyrous umbones positioned just behind the midline. Dorso-anterior margin long, slightly inclined, straight. Lunule sunken and a half of dorso-anterior margin length; lunule margin with boundary ridges sunken. Anterior margin uniformly rounded, continuous with the slightly rounded ventral margin. Postero-dorsal margin long, slightly convex, truncated in the confluence with the posterior margin. Posterior region with two sulci: a submarginal sunken sulcus without auricle projection; and a posterior sunken sulcus forming a weak posterior sinus. Sunken and narrow escutcheon. External surface with weak commarginal lines. Periostracum thin with spinose microstructures distributed in a random pattern; each spine has a longitudinal sulcus taking 2/3 of its length. Mainly in the ventral margin, the periostracum extends to internal surface of the valve. Weak hinge. Right and left valves without cardinal teeth; right hinge with small rounded pseudotooth and respective depression on left hinge. Pseudo-external, opisthodetic ligament with outline triangular and taking 1/2 of dorso-posterior margin. Internal surface opaquely white. Anterior and posterior adductor muscle scars weakly impressed, the anterior roundly elongate and the posterior, elliptical-oval. Retractor muscle scars not impressed. Prodissoconch 130 to 190µm in length; its sunken limits surrounded by belt; radial wrinkles absent. Growth changes: Small variations occur among specimens of same size and along the growth. The juveniles are slightly more elongate than the adults due to the pronounced anterior region; in the larger animals the height is mostly equal to length, the dorso-anterior margin is straight and the lunule is less demarcated than in small specimens. Along the growth, the posterior sulcus becomes more prominent causing the formation of a weak posterior sinus which is absent in the smaller specimens. Variations: There isn’t any significant variation among the examined specimens. Remarks: The shell of the new species resembles the one of Spinaxinus sentosus Oliver & Holmes (2006), but these species strongly differ regarding the anterior margin which is slightly truncate in the latter while in the former it is uniformly rounded. Apart from this, the posterior sinus of the new species appears to be stronger (Fig. 11G) than in S. sentosus; the lunule is present in both, but it is more concave and sunken in S. sentosus than in the new species (Fig. 11F). Near the

lunule margin and in the inner surface of the valves, S. sentosus has residual pedal retractor scars, which are not observed in the new species. Moreover, the shell of Spinaxinus sentosus is more inflated, while in the new species it is more laterally compressed (Fig. 11F). The new species is also different from the Spinaxinus species described to Gulf of Mexico, Spinaxinus emicatus and, the vent species in Pacific Ocean, Spinaxinus phrixicus, which are larger and oval – up to 20mm and 15mm in length, respectively – while the new one reaches 6.1mm and is elongated (Fig. 11, D and E). The shell of the Antarctic Spinaxinus caldarium is also larger, up to 19.1mm, and so distinct from the new species Brazilian species of Spinaxinus. All these species of Spinaxinus, including the new one from Brazil, have very similar microstructures on the external surface of the shell (Fig. 12, D to G), this being a main character used by Oliver & Holmes (2006) to originally describe Spinaxinus, although this feature is not exclusive for this genus. In Thyasira, for example, Payne & Allen (1991) and Oliver & Holmes (2006) highlighted the presence of microstructures in Thyasira sarsi and T. subcircularis Payne & Allen, 1991 (the latter is current classified as subgenus Parathyasira). The present study confirmed that Thyasira trisinuata has a periostracum with rounded pustular microstrucutres on commarginal pattern on external surface (Fig. 6, B to D); in T. sarsi microstructures are rounded and calcareous origin (Oliver & Holmes, 2006). Payne & Allen (1991), Huber (2010), Oliver & Rodrigues (2017) suggested that the presence of external microstructures is character of the old subgenus Parathyasira, that contains Thyasira subcircularis (Payne & Allen, 1991), which is in turn similar to Parathyasira granulosa (Fig. 10, D to G). Parathyasira granulosa (Monterosato, 1874) and P. resupina are the only species of Parathyasira that have external microstructure that is spinose (Iredale, 1930; Payne & Allen, 1991), but distributed in a radial pattern, and so distinct to the ones of Spinaxinus, which it is in a commarginal pattern (Oliver & Rodrigues, 2017). Occurring naturally in organic falls, Atlantic species of Spinaxinus have been registered from artificial substrates simulating a reduced environment (Oliver et al., 2013), based on traps experiments to understand the associate faunas (Gaudron et al., 2010). The current discussed species is the first record of Spinaxinus in whale bone falls trap. Usually, the species related to organic falls are retrieved at surrounding sediments and, supporting the period, only 10 months of bones decomposition, that new species are considered as early colonizer (Oliver et al., 2013). Organic falls and reduced habitats have been related to chemoassociated individuals, unique and specialized species hosted (Smith & Kukert, 1989; Taylor & Glover, 2005; Taylor & Glover, 2013).

All Spinaxinus species present association with chemossinbionts bacterias in their gills, inferring the possibility to be found in the new species too. The connection between those habitats and dispersal fauna mechanisms are mostly unknown for science (Duperron et al., 2013; Oliver et al., 2013; Levin et al., 2016).

Figure 11 – Spinaxinus sp. A - D - growth serie: (A) and (B) juveniles; (C) intermediate and (D) adult. (E) adult. (F) dorsal view. (G) SEM of posterior view. H and I – larval shell: (H) larval shells of right and left valves, (I) larval shell of left valve. (J) external view of left valve. (K) hinge of left valve. (L) SEM of left hinge highlighting the depression. (M) external view of right valve. (N) right hinge. (O ) SEM of right hinge highlighting the pseudotooth.

Figure 12 – External microstructures of periostracum of Spinaxinus sp. (A) SEM of microstructures of periostracum on midline of ventral margin. (B) magnification of x100 on midline of ventral margin. (C) SEM of microstructures of periostracum on posterior- dorsal region. (D) magnification of x400 on posterior-dorsal margin. (E) SEM of internal periostracum on midline of ventral margin. (F) SEM of shell profile. (G) SEM magnification of x2,000 highlighting each spinose structure.

DISCUSSION

In Brazilian coast, the biodiversity knowledge of Thyasiridae species is scarce which represents the underestimated species number of Thyasiridae worldwide (Allen, 2008; Huber, 2015). The low number of registered species might be explained based on difficulties of classify and identifying thyasirids species because of variable and tenuous shell morphology of minute size specimens (Payne & Allen, 1991; Killeen & Oliver, 2002a; Oliver & Sellanes, 2005; Oliver & Drewery, 2013). Payne & Allen (1991) suggested that similarity observed among thyasirids species is its pre-adaptation which allow them to live in deep-sea. Exemplifying the authors hypothesis, they use a high depth range occurrence species like T. obsoleta that represents species which does not suffer strong morphology variation comparing individuals from different depths.

Just as mentioned before, the most problematic of Thyasiridae is the subcategories and generic descriptions in genera and specific levels (Huber, 2015). However, there is a necessity of compare side by side each specimen to comprehend the differences and similarities of species mainly in shell morphology which helped differ the examined species analyzed in this work – Thyasira, Parathyasira and Spinaxinus species and their comparison species. The former two genera are considered not well stablished in literature because some author suggest keep them as subgenera (e.g. Payne & Allen, 1991; Killeen & Oliver, 2002a; Rodrigues et. al., 2008; Huber, 2015) and some as independent ones (e.g. Zelaya et. al., 2009; Huber, 2015; Oliver, 2015; Oliver & Rodrigues, 2017). Meanwhile, some shell morphologies were highlighted to help distinguish genera and one species from another, like shell outline, shell sulci, hinge details and presence or absence and morphology of periostracum microstructures in external surfaces. Thyasirids species could be divided in two main groups based on their shell morphologies (Payne & Allen, 1991; Rodrigues et. al., 2008): higher shells, which characterized Thyasira and Parathyasira species (Thyasira trisinuata and Parathyasira granulosa, respectively), and elongated shells, Thyasira and Spinaxinus species (Thyasira obsoleta and Spinaxinus sp). Payne & Allen (1991) correlated the shell outline and hinge details, the authors observed a well-developed hinge pseudotooth in higher species and less developed in elongated outline species. This pattern is here supported by examined Thyasira species except to T. sarsi, which does not have a pseudotooth, just as Spinaxinus and Parathyasira species which are characterized to be edentule without pseudotooth. Sunken posterior sulcus or weak posterior sulcus is related to bigger and

smaller species (Payne & Allen, 1991), respectively, corresponding to the observations made here. The presence or absence of submarginal sulcus and auricle projection is direct related (Payne & Allen, 1991), which is exemplifying by T. trisinuata with sunken submarginal sulcus and a higher auricle projection and P. granulosa with none submarginal sulcus and auricle projection. Those outline differences related to other shell morphologies should reflect on species habits. The bigger, higher and more inflated possibly live deeply buried and less mobile while the elongated and flattened ones should bury closely to the surface and be more mobile (Payne & Allen, 1991; Watters, 1993). Microstructures on external surface, calcareous or periostracum origins, have been discussed by Payne & Allen (1991), Killeen & Oliver (2002a), Oliver & Holmes (2006), Rodrigues et al. (2008), Huber (2015), Oliver (2015), Oliver & Rodrigues (2017). The spiny morphology of periostracum microstructures observed in Spinaxinus species was responsible of the genus name (Oliver & Holmes, 2006). As well as discussed above, this feature and its origin is not restricted to Spinaxinus, spinose periostracum microstructure was also observed in Parathyasira granulosa. Even considered as unusual to Thyasira species, most of them also have microstructures but in a different pattern, radial or randomly, and morphology, pustule (periostracum origin) or rounded (calcareous origin) such as T. trisinuata and T. sarsi (Oliver & Holmes, 2006), respectively. Apart from that, thyasirids may occur in a variety of habitats such as hydrothermal vents, oilfields, mud volcanoes, organic falls (Corliss et al., 1979; Smith et al., 1989; Killen & Oliver, 2002a; Smith & Baco, 2003; Oliver & Holmes, 2006; Rodrigues et. al., 2008; Takai & Nakamura, 2011; Fagervold et. al., 2012; Oliver et. al., 2013; Kalenitchenko et. al., 2015; Kalenitchenko et. al., 2016; Kalenitchenko et. al., 2018), where its diversity is specific (Bernardino et al., 2012). However, species like T. sarsi is an example of the same species which occur in many different places: methane seep, active pockmark, vegetation fall (Dando & Southward, 1986; Dando et al., 1994; Dando et. al., 1991; Oliver et al., 2013) but it still morphologically one species (Dando & Southward, 1986; Dando et al., 1994; Dando et al., 1991; Oliver et al., 2013). Oliver et al. (2013) and Astrom et al., (2017) suggest that thyasirids are not restricted to an only habitat but a reduced environment considering, then, as an early colonizer. Oliver et al., (2013) support this hypothesis based on Spinaxinus species which there are five species already described that occur in five different places, including artificial traps in Atlantic and Pacific Oceans as already discussed above.

Then, those places are considered temporary reduced places or stepping stone environment allowing organisms dispersal (Smith et. a., 1989; Astrom et. al., 2017).

GENERAL CONCLUSIONS

The general conclusions about this work are: ● Four species registered to the southern and southeastern Brazilian coasts, Thyasira trisinuata, which was already recorded to them and here confirmed and redescribed; Parathyasira granulosa, new occurrence to the coasts but specimens were misidentified as Thyasira croulinensis; Thyasira obsoleta, also a new occurrence; and Spinaxinus sp. new species. ● The shell morphology is useful to distinguish species of each other and among the similar congeners when compared to the type-materials. ● The main characters that differ one species of another is the outline, characteristics of posterior region and margin and external surface features. ● It would be interesting to have access of specimens from other Brazilian localities, such as northeastern to better understand the species distribution and variations along the Brazilian coast.

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APPENDIX This annex will be present some extra information about the examined materials of each species.

Table 1 - Total analyzed valves from nationals and internationals institutions. Quantity of examined valves

Thyasira Thyasira Parathyasira Soinaxinus Total Institutions (Thyasira) obsoleta granulosa sp trisinuata

Lab of Malacology 316 16 76 0 408 (Unicamp)

ZUEC Museum 26 0 0 0 26 (Unicamp)

MUCIN 128 0 0 0 128

MNRJ 12 643 16 0 671

UFRJ 0 84 0 0 84

USNM 42 24 32 0 74

MCZ 0 0 0 0 0

NMNH - Paris 196 0 0 0 196

IO - USP 0 0 0 200 200

Total 720 743 124 200 1587

Table 2 – Examined and re-identified samples from National Museum of Natural History (NMNH) and Museum Support Center (MSC) of Smithsonian Institution. USNM Old-iD Re-ID Locality Depth Thyasira Thyasira Off Marth`s Vineyard – USA 82m 35023 trisinuata biplicata Thyasira Thyasira Off Cape Hatteras, North 27m 38404 trisinuata trisinuata Carolina – USA Thyasira Thyasira Off Marth`s Vineyard – USA 115m 40216 trisinuata biplicata Thyasira S of Nantucket – USA 97m 40275 Thyasira flexuosa trisinuata Thyasira Thyasira Off Marth`s Vineyard – USA 142m 40291 trisinuata biplicata Thyasira Off Marth`s Vineyard – USA 7m 40298 Thyasira flexuosa trisinuata Thyasira Thyasira Off Marth`s Vineyard – USA 6m 40312 trisinuata biplicata Thyasira Thyasira Off Marth`s Vineyard – USA 91m 40342 trisinuata biplicata Thyasira Thyasira S of Nantucket – USA 97m 40389 trisinuata biplicata Thyasira Off Marth`s Vineyard – USA 80m 40449 Thyasira flexuosa trisinuata Thyasira Off Cape Hatteras, North 2m 44580 Thyasira flexuosa trisinuata Carolina – USA Thyasira Chesapeak Bay – USA 128m 44616 Thyasira flexuosa trisinuata Thyasira Off Cape Hatteras, North 78m 44617 Thyasira flexuosa trisinuata Carolina – USA Thyasira Off Martha`s Vineyard – USA 351m 45707 Thyasira flexuosa trisinuata

Thyasira Thyasira Off Martha`s Vineyard – USA 283m 45708 trisinuata biplicata Thyasira Thyasira Off Martha`s Vineyard – USA 210m 45709 trisinuata biplicata Thyasira Thyasira Off Martha`s Vineyard – USA 182m 45710 trisinuata biplicata Thyasira Thyasira Off Martha`s Vineyard – USA 219m 45711 trisinuata biplicata Thyasira Off Martha`s Vineyard – USA 230m 45712 Thyasira flexuosa trisinuata Thyasira Thyasira Off Martha`s Vineyard – USA 97m 45714 trisinuata biplicata Thyasira Thyasira Off Martha`s Vineyard – USA 183m 45715 trisinuata biplicata Thyasira Off Martha`s Vineyard – USA 219m 45716 Thyasira flexuosa trisinuata Thyasira Thyasira Off Martha`s Vineyard – USA 347m 53106 trisinuata biplicata Thyasira New England – USA Thyasira flexuosa/ 62069 trisinuata Thyasira biplicata Thyasira Thyasira New England – USA 62099 trisinuata biplicata Thyasira Thyasira USA 64225 trisinuata biplicata Thyasira Thyasira Off George`s Bank – USA 786m 74291 trisinuata biplicata Thyasira Off Nova Scotia – Canada 95m 74293 Thyasira sp trisinuata

Thyasira Thyasira succisa Off Cape Cod. – USA 49m 74294 trisinuata succisa Thyasira Rhode Island – USA 35m 74295 Thyasira flexuosa trisinuata Thyasira Off Martha`s Vineyard – USA 62m 74300 Thyasira flexuosa trisinuata Thyasira Off Cape Hatteras, North 241m 76754 Thyasira flexuosa trisinuata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 219m 92588 trisinuata biplicata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 115m 92589 trisinuata biplicata Carolina – USA Thyasira Off Cape Hatteras, North 92590 Thyasira flexuosa trisinuata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 27m 92591 trisinuata trisinuata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 159m 92592 trisinuata biplicata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 227m 92594 trisinuata biplicata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 33m 92595 trisinuata trisinuata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 40m 92596 trisinuata trisinuata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 40m 92597 trisinuata trisinuata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 92598 trisinuata trisinuata Carolina – USA Thyasira Thyasira Off Cape Hatteras, North 92599 trisinuata biplicata Carolina – USA

Thyasira Off Cape Hatteras, North 196m Thyasira flexuosa/ Carolina – USA 93542 trisinuata Thyasira biplicata Thyasira Thyasira Off Cape of Florida, Florida – 155m 94188 trisinuata biplicata USA Thyasira Thyasira South of Lookout, North 57m 94190 trisinuata trisinuata Carolina – USA Thyasira Off Cape Hatteras, North 40m 94191 Thyasira flexuosa trisinuata Carolina – USA Thyasira Thyasira 97147 trisinuata biplicata Thyasira Thyasira 108948 trisinuata trisinuata Thyasira Off of Florida, Florida – USA 155m 151988 Thyasira flexuosa trisinuata Thyasira Thyasira Deltaand Cedar Keys, Gulf of 110m 157878 trisinuata trisinuata Mexico, Florida – USA Thyasira Thyasira Off Delaware Bay – USA 110m 181251 trisinuata biplicata Thyasira Thyasira 91m 430088 trisinuata trisinuata Thyasira Off Sand Key, Florida – USA 142m 445788 Thyasira flexuosa trisinuata Channelaxinus Thyasira oliveri Valentich- 445869 trisinuata Scott & Coan, 2012 Thyasira Off Key West, Florida - USA 115m 445870 Thyasira flexuosa trisinuata

Thyasira Key West, Florida - USA 110m 445871 Thyasira flexuosa trisinuata Thyasira Off Ajax Reef, Florida – USA 146 – 182m 445872 Thyasira flexuosa trisinuata Thyasira Off Miami, Florida – USA 110m 445873 Thyasira flexuosa trisinuata Thyasira Off Miami, Florida – USA 110m 445874 Thyasira flexuosa trisinuata Channelaxinus Off Gov. Cut. Miami, Florida 110m Thyasira oliveri Valentich- – USA 445875 trisinuata Scott & Coan, 2012 Thyasira Off Gov. Cut. Miami, Florida 137m Thyasira flexuosa/ – USA 445876 trisinuata Channelaxinus oliveri Thyasira Off Fowey Light, Florida – 382m 445877 Thyasira flexuosa trisinuata USA Thyasira Off Fowey Light, Florida – 118m 445878 Thyasira flexuosa trisinuata USA Thyasira Off Fowey Light, Florida – 128m 445879 Thyasira flexuosa trisinuata USA Thyasira Off Fowey Light, Florida – 106m 445880 Thyasira flexuosa trisinuata USA Thyasira Off Fowey Light, Florida – 95m Thyasira flexuosa/ USA 445881 trisinuata Channelaxinus oliveri Thyasira Off Fowey Light, Florida – 110m 445882 Thyasira flexuosa trisinuata USA

Thyasira Florida – USA 220m 445883 Thyasira flexuosa trisinuata Thyasira Fowey Light, Florida - USA 165m 445884 Thyasira flexuosa trisinuata Thyasira Off Fowey Light, Florida – 64m 445885 Thyasira flexuosa trisinuata USA Channelaxinus Off Raggedd Key, Florida – 130m Thyasira oliveri Valentich- USA 445886 trisinuata Scott & Coan, 2012 Channelaxinus Off Raggedd Key, Florida – 155m Thyasira oliveri Valentich- USA 445887 trisinuata Scott & Coan, 2012 Thyasira Off Sand Key, Florida – USA 64m 445889 Thyasira flexuosa trisinuata Thyasira Off Sand Key, Florida – USA 139m 445890 Thyasira flexuosa trisinuata Thyasira Thyasira Off Pelican II, Barbados 182m 503435 trisinuata trisinuata Thyasira Thyasira Off Lazaretto, Barbados 182m 503436 trisinuata trisinuata Thyasira Thyasira Off Lazaretto, Barbados 182m 503437 trisinuata trisinuata Thyasira Thyasira Off Payne’s Bay Church, 165m 503438 trisinuata trisinuata Barbados Thyasira Chennelaxinus South Carolina – USA 703737 trisinuata oliveri Thyasira Lantana, Slorida – USA 128m 822820 Thyasira flexuosa trisinuata

Thyasira Antartica 37m 898272 Thyasira sarsi trisinuata 801046 GD15 100m Thyasira / Block Thyasira flexuosa trisinuata ID. 8-1 801047 GWPierce II RW 185m / Block Thyasira Thyasira flexuosa ID. 4-1 trisinuata & 5-4 Thyasira Thyasira GD15 100m 801046 trisinuata biplicata Thyasira Thyasira GWPierce II RW 185m 801047 trisinuata biplicata Thyasira Thyasira 801048 trisinuata biplicata Thyasira Thyasira 897034 trisinuata biplicata Thyasira Thyasira 930417 trisinuata biplicata Thyasira Thyasira 830416 trisinuata biplicata Thyasira Thyasira 830398 trisinuata biplicata Thyasira Thyasira 830402 trisinuata biplicata Thyasira Thyasira 830404 trisinuata biplicata Thyasira Thyasira 830409 trisinuata biplicata

Thyasira Thyasira 930403 trisinuata biplicata Thyasira Thyasira 830405 biplicata/ trisinuata Thyasira flexuosa Thyasira Thyasira 830406 biplicata/ trisinuata Thyasira flexuosa Thyasira Thyasira 830399 trisinuata biplicata Thyasira 830411 Thyasira flexuosa trisinuata Thyasira Thyasira 830401 biplicata/ trisinuata Thyasira flexuosa Thyasira Thyasira 830412 biplicata/ trisinuata Thyasira flexuosa Thyasira 830408 Thyasira flexuosa trisinuata Thyasira Thyasira 830397 trisinuata biplicata Thyasira Thyasira 830407 trisinuata biplicata Thyasira 830395 Thyasira gouldii trisinuata Thyasira Thyasira 830410 biplicata/ trisinuata Thyasira gouldii

Thyasira Thyasira 847559 trisinuata biplicata Thyasira Thyasira 847558 trisinuata biplicata Thyasira Thyasira 847551 trisinuata biplicata Thyasira Thyasira 847550 trisinuata biplicata Thyasira Thyasira 830388 trisinuata biplicata Thyasira 830373 Thyasira gouldii trisinuata Thyasira Thyasira 830366 biplicata/ trisinuata Thyasira flexuosa Thyasira Drobak - Norway 13960 Thyasira sarsi flexuosa Thyasira Timby 14122 Thyasira flexuosa flexuosa Thyasira Mendicula Loch Tyne, Britain - UK 14123 flexuosa ferruginosa Thyasira Grand Greve Gaspe - Canada 91m 22766 Thyasira gouldii flexuosa Thyasira Massachussetts Bay – USA 24664 Thyasira gouldii flexuosa Thyasira Henley Harbor, Labrador – 9m 34367 Thyasira gouldii flexuosa Canada Thyasira L`Anse au Loup, Labrador – 9m 34368 Thyasira gouldii flexuosa Canada

Thyasira Off George`s Bank – USA 181m 35079 Thyasira sp flexuosa Thyasira Off Martha`s Vineyard – USA 182m 45727 Thyasira gouldii flexuosa Thyasira Off Newfoundland – Canada 52400 Thyasira gouldii flexuosa Thyasira Off Nova Scotia – Canada 52436 Thyasira gouldii flexuosa Thyasira Green Bank, New Jersey – 122m 52438 Thyasira gouldii flexuosa USA Thyasira South of Matha`s Vineyard – 713m 52441 Thyasira gouldii flexuosa USA Thyasira Off Nova Scotia – Canada 52442 Thyasira gouldii flexuosa Thyasira Green Bank, New Jersey – 861m 52556 Thyasira sarsi flexuosa USA Thyasira 238m 52733 Thyasira sarsi flexuosa Thyasira 61941 Thyasira flexuosa flexuosa Thyasira Thyasira 61943 flexuosa biplicata Thyasira 61944 Thyasira flexuosa flexuosa Thyasira Thyasira 61945 biplicata/ flexuosa Thyasira flexuosa Thyasira Greenland,Holsteinsborg 18m 61948 Thyasira gouldii flexuosa

Thyasira gouldii/ Thyasira 61952 T. succisa flexuosa succisa Thyasira Obra Firth 61953 Thyasira flexuosa flexuosa Thyasira Thyasira Tunis Bay, Tunes 46 – 155m 61954 flexuosa biplicata Thyasira North Sea, German Ocean 61955 Thyasira flexuosa flexuosa Thyasira Greenland,Holsteinsborg 55m 61957 Thyasira gouldii flexuosa Thyasira Greenland,Holsteinsborg 18m 61958 Thyasira gouldii flexuosa Thyasira Greenland,Holsteinsborg 22m 61959 Thyasira gouldii flexuosa Thyasira T. succisa 61960 flexuosa succisa Thyasira Thyasira 61964 flexuosa biplicata Thyasira Skye 61966 Thyasira flexuosa flexuosa Thyasira Skye 61968 Thyasira flexuosa flexuosa Thyasira Norway 62003 Thyasira sarsi flexuosa Thyasira Drobak – Norway 110m 62004 Thyasira sarsi flexuosa Thyasira Lofoten I. – Norway 36 -91m 62005 Thyasira sarsi flexuosa

Thyasira Scandinavia 62006 Thyasira sarsi flexuosa Thyasira Norway 62007 Thyasira flexuosa flexuosa Thyasira Bergen – Norway 62008 Thyasira sarsi flexuosa Thyasira Drobak – Norway 62009 Thyasira sarsi flexuosa Thyasira Iceland 62019 Thyasira gouldii flexuosa Thyasira Norway 62022 Thyasira sarsi flexuosa Thyasira Osterfjord – Norway 62025 Thyasira sarsi flexuosa Thyasira Torbay Thyasira 62026 flexuosa/ flexuosa Thyasira gouldii Thyasira sarsi/ Osterfjord – Norway Thyasira Thyasira 62027 flexuosa/ flexuosa Thyasira biplicata Thyasira Vadso – Norway 62028 Thyasira gouldii flexuosa Thyasira Spazzia – Italy 62031 Thyasira flexuosa flexuosa Thyasira Norway 62032 Thyasira flexuosa flexuosa Thyasira Thyasira Vigo Bay – Spain 62034 flexuosa biplicata

Thyasira Thyasira Unst 174m 62035 flexuosa biplicata Thyasira Breton 62036 Thyasira flexuosa flexuosa Thyasira Killybegs Harb. 62039 Thyasira flexuosa flexuosa Thyasira Adventure Bay, Cartegena – 168m 62040 Thyasira flexuosa flexuosa Colombia Thyasira Thyasira Adventure Bay, Cartegena – 84-153m 62041 flexuosa biplicata Colombia Thyasira Drogger Bank, North Sea 62042 Thyasira flexuosa flexuosa Thyasira Zetland 62043 Thyasira flexuosa flexuosa Thyasira Hebrides 62044 Thyasira flexuosa flexuosa Thyasira St. Magnus Bay – UK 62045 Thyasira flexuosa flexuosa Thyasira Thyasira Iceland 62046 flexuosa biplicata Thyasira Shetland 62047 Thyasira flexuosa flexuosa Thyasira Unst. Haf. Thyasira flexuosa/ 62050 flexuosa Thyasira biplicata Thyasira Arran I. 62051 Thyasira flexuosa flexuosa Thyasira Guemsey 62052 Thyasira flexuosa flexuosa

Thyasira Plymouth 62053 Thyasira flexuosa flexuosa Thyasira Shetland 62054 Thyasira flexuosa flexuosa Thyasira L. Tyne 62055 Thyasira flexuosa flexuosa Thyasira Shetland 62056 Thyasira flexuosa flexuosa Thyasira Zetland Thyasira 62057 biplicata/ flexuosa Thyasira flexuosa Thyasira Skye 62058 Thyasira flexuosa flexuosa Thyasira Norway 62059 Thyasira sarsi flexuosa Thyasira G St. Lawrence 62088 Thysira equalis flexuosa Thyasira Norway 62089 Thyasira gouldii flexuosa Thyasira Gaspe Bay 62092 Thyasira gouldii flexuosa Thyasira Greenland 62093 Thyasira gouldii flexuosa Thyasira Eastport, Maine – USA 74219 Thyasira gouldii flexuosa Thyasira gouldii/ Grand Menan Thyasira 74220 Thyasira flexuosa biplicata Thyasira Bay of Fundy 110m 74221 Thyasira gouldii flexuosa

Thyasira gouldii/ Gulf of Maine 95-117m Thyasira 74222 T. succisa flexuosa succisa Thyasira Jeffrey`s Bank 146m 74225 Thyasira gouldii flexuosa Thyasira Massachusetts Bay – USA 102m 74226 Thyasira gouldii flexuosa Thyasira Casco Bay, Maine - USA 172m 74228 Thyasira gouldii flexuosa Thyasira Stellwagen`s Bank 53m 74229 Thyasira gouldii flexuosa Thyasira Casco Bay, Maine – USA 74230 Thyasira gouldii flexuosa Thyasira N. Thatcher`s Id. – USA 93m 74232 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 78-124m 74233 Thyasira gouldii flexuosa Thyasira gouldii/ Jeffrey`s Ledge 161-168m Thyasira 74234 Thyasira flexuosa biplicata Thyasira W Jeffrey`s Ledge 161-168m 74235 Thyasira gouldii flexuosa Thyasira gouldii/ Gulf of Maine – USA 77-106m Thyasira 74236 Thyasira flexuosa biplicata Thyasira E of Jeffrey`s Ledge 228m 74237 Thyasira gouldii flexuosa Thyasira Off Boon II 93m 74238 Thyasira gouldii flexuosa

Thyasira Salem 58m 74239 Thyasira flexuosa flexuosa Thyasira Halifax Harbor – Canada 29m 74241 Thyasira gouldii flexuosa Thyasira Halifax Harbor – Canada 33m 74244 Thyasira gouldii flexuosa Thyasira Off Nova Scotia, Halifax 74245 Thyasira gouldii flexuosa Harbor – Canada Thyasira Massachusets Bay – USA 47m 74249 Thyasira gouldii flexuosa Thyasira Gulf ofMaine 64m 74251 Thyasira gouldii flexuosa Thyasira Massachusets Bay – USA 182m 74252 Thyasira flexuosa flexuosa Thyasira Off Cape Cod. 110m 74253 Thyasira gouldii flexuosa Thyasira Massachusets Bay – USA 58m 74254 Thyasira gouldii flexuosa Thyasira Massachusets Bay – USA 5+8m 74255 Thyasira gouldii flexuosa Thyasira Massachusetts Bay – USA 51m 74256 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 37m 74258 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 64m Thyasira 74260 flexuosa/ flexuosa Thyasira gouldii Thyasira Off Cape Cod. 86m 74261 Thyasira gouldii flexuosa

Thyasira Off Cape Cod. 53m 74262 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 50m 74263 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 48m 74264 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 50m 74265 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 35 – 38m 74266 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 46m 74267 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 122m 74268 Thyasira gouldii flexuosa Thyasira gouldii/ Off Cape Cod. 29m Thyasira 74269 Thyasira flexuosa biplicata Thyasira Off Cape Cod. 26m 74270 Thyasira gouldii flexuosa Thyasira Off Cape Cod. 88m 74272 Thyasira gouldii flexuosa Thyasira Off Newport – USA 36m 74274 Thyasira gouldii flexuosa Thyasira Narragansett Bay – USA 36m 74278 Thyasira gouldii flexuosa Thyasira Off Martha`s Vineyard – USA 62m 74279 Thyasira gouldii flexuosa Thyasira Casco Bay – USA 74281 Thyasira gouldii flexuosa

Thyasira Gulfof Maine – USA 47m 74283 Thyasira gouldii flexuosa Thyasira Gulfof Maine – USA 182m 74284 Thyasira gouldii flexuosa Thyasira Gulfof Maine – USA 110m 74285 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 64m 74286 Thyasira flexuosa flexuosa Thyasira Thyasira gouldii/ Off Cape Cod. – USA 135m 74289 flexuosa Thyasira flexuosa Thyasira Off Cape Cod. – USA 238m 74290 Thyasira sarsi flexuosa Thyasira Off Cape Cod. – USA 49m 74294 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 60m 74310 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 223m 74313 Thyasira gouldii flexuosa Thyasira Casco Bay, Maine – USA 108866 Thyasira gouldii flexuosa Thyasira Gulf of St. Lawrence 108867 Thyasira gouldii flexuosa Thyasira Chelsea Beach, Massachusetts 108868 Thyasira gouldii flexuosa – USA Thyasira Bergen – Norway 36m 108946 Thyasira sarsi flexuosa Thyasira gouldii / S of Marth`s Nineyard – USA 713m Thyasira 151904 Axinulus flexuosa croulinensis

Thyasira Kildin Id., Murman Coast 9 – 18m 152580 Thyasira gouldii flexuosa Thyasira Off Gloucester – USA 73m 153690 Thyasira gouldii flexuosa Thyasira Casco Bay – USA 159848 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 82m 159849 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 133m 159851 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 88m 159852 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 70m 159853 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 25m 159854 Thyasira gouldii flexuosa Thyasira Off Nova Scotia – Canada 33m 159855 Thyasira gouldii flexuosa Thyasira Casco Bay – USA 159856 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 49m 159857 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 47m 159858 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 53m 159859 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 29m 159860 Thyasira gouldii flexuosa Thyasira Off Cape Cod. – USA 25m 159861 Thyasira gouldii flexuosa

Thyasira Gulf of Maine – USA 38m 159862 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 64m 159863 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 47m 159864 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 124m 159876 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 70m 159877 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 47m 159878 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 64m 159879 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 179m 159880 Thyasira gouldii flexuosa Thyasira Gulf of Maine – USA 100m 159881 Thyasira gouldii flexuosa Thyasira Off Nova Scotia, Halix Harbor 33m 159882 Thyasira gouldii flexuosa – Canada Thyasira Off Cape Cod. – USA 47m 159883 Thyasira sarsi flexuosa Thyasira Seal Cove 159884 Thyasira gouldii flexuosa Thyasira gouldii/ Frenchman`s Bay, Maine – 0-64m Thyasira Thyasira USA 173277 flexuosa biplicata/ Lucinidae Thyasira Labrador – Canada 181939 Thyasira gouldii flexuosa

Thyasira Fjord – Norway 201682 Thyasira sarsi flexuosa Thyasira Scilly Island, Englando – UK 217677 Thyasira flexuosa flexuosa Thyasira Nova Scotia – Canada 10-26m 219833 Thyasira gouldii flexuosa Thyasira England – UK Thyasira flexuosa/ 225200 flexuosa Thyasira biplicata Thyasira Thyasira gouldii/ Hardanger Fjord – Norway 18m 225201 flexuosa Thyasira sarsi Thyasira North Sea 9m 225202 Thyasira flexuosa flexuosa Thyasira Firth of Clyde, Scotland – UK 250943 Thyasira flexuosa flexuosa Thyasira Wiscasset, Maine – USA 253731 Thyasira gouldii flexuosa Thyasira Digby, Nova Scotia – Canada 273461 Thyasira gouldii flexuosa Thyasira Maine – USA 333645 Thyasira gouldii flexuosa Thyasira Dublin, Republico of Ireland 337240 Thyasira flexuosa flexuosa Thyasira Kennebecasis Bay – Canada 60m 420709 Thyasira gouldii flexuosa Thyasira Eastport, Maine – USA 425779 Thyasira gouldii flexuosa Thyasira Casco Bay, Maine – USA 431277 Thyasira gouldii flexuosa

Thyasira Thyasira gouldii/ Labrador – Canada 431301 flexuosa Thyasira sarsi Thyasira Friar`s Head, Maine – USA 445797 Thyasira gouldii flexuosa Thyasira Egg Harbor, Labrador – 13m 445861 Thyasira gouldii flexuosa Canada Thyasira Sand Island, New Brunswick 445862 Thyasira gouldii flexuosa – Canada Thyasira Eastport, Maine – USA 445863 Thyasira gouldii flexuosa Thyasira Maine – USA 445864 Thyasira gouldii flexuosa Thyasira Maine – USA 445865 Thyasira gouldii flexuosa Thyasira E of Nanset Light, Maine – 445866 Thyasira gouldii flexuosa USA Thyasira Plymouth, Massachusetts – 42-55m 445867 Thyasira gouldii flexuosa USA Thyasira George Bank, Maine – USA 914m 445868 Thyasira gouldii flexuosa Thyasira Bar Harbor, Mt Desert, Maine 451278 Thyasira gouldii flexuosa – USA Thyasira Wiscasset, Maine – USA 465825 Thyasira gouldii flexuosa Thyasira Campobello Island, Friar – 611676 Thyasira gouldii flexuosa Canada Thyasira Bohusian, Sweden 611901 Thyasira flexuosa flexuosa Thyasira Osterfjord – Norway 611903 Thyasira sarsi flexuosa

Thyasira Spitzbergen – Norway 633866 Thyasira gouldii flexuosa Thyasira Unst 633868 Thyasira gouldii flexuosa Thyasira Shetland 633870 Thyasira gouldii flexuosa Thyasira 633871 Thyasira flexuosa flexuosa Thyasira Norway 633875 Thyasira gouldii flexuosa Thyasira Norway 633877 Thyasira sarsi flexuosa Thyasira Skye 633880 Thyasira flexuosa flexuosa Thyasira Norway 819910 Thyasira sarsi flexuosa Thyasira Oresind – Denmark 58m 819913 Thyasira sarsi flexuosa Thyasira Bohusian – Sweden 15m 819914 Thyasira flexuosa flexuosa Thyasira SW of outar Jattehofmen – 402 – 420m 819915 Thyasira sarsi flexuosa Sweden Thyasira gouldii/ Diskofjourd – Greenland Thyasira 819918 T. succisa flexuosa succisa Thyasira George`s Bank, Southern 90m 843000 Thyasira gouldii flexuosa Slope – USA Thyasira George`s Bank, Southern 103m 843001 Thyasira gouldii flexuosa Slope – USA

Thyasira George`s Bank, Southern 142m 843002 Thyasira gouldii flexuosa Slope – USA Thyasira George`s Bank, Southern 106m 843003 Thyasira gouldii flexuosa Slope – USA Thyasira George`s Bank, Massachusetts 90m 847561 Thyasira flexuosa flexuosa – USA Thyasira Wiscasset, Maine – USA 890695 Thyasira gouldii flexuosa 144245 Thyasira Maine – USA Thyasira gouldii 9 flexuosa Thyasira Off New Jersey – USA 89m 830593 Thyasira flexuosa flexuosa Thyasira Off New Jersey – USA 750m 830573 Thyasira flexuosa flexuosa Thyasira Off New Jersey – USA 90m 830649 Thyasira flexuosa flexuosa Thyasira Off New Jersey – USA 77m 830653 Thyasira flexuosa flexuosa Thyasira Off Virginia – USA 140m 830662 Thyasira flexuosa flexuosa Thyasira Off New Jersey – USA 170m 830655 Thyasira flexuosa flexuosa Parathyasira Parathyasira 61956 granulosa granulosa Parathyasira Parathyasira 61979 granulosa granulosa Parathyasira Parathyasira Osterfjord - Norwaay 62030 granulosa granulosa Parathyasira Parathyasira Norway 633879 granulosa granulosa

COMPARISONS SPECIES

The plates below are from specimens that characterize the species and were used to compare with four Thyasiridae species present in this current project. Those species were:

● Thyasira biplicata

● Thyasira flexuosa

● Tellina flexuosa

● Thyasira gouldii

● Thyasira sarsi

● Cryptodon insignis

● Thyasira succisa atlantica

● Thyasira atlantica

● Leptaxinus var minutus [=Thyasira minuta = Thyasira succisa minuta Payne &

Allen, 1991)

● Cryptodon equalis [=Parathyasira equalis]

● Cryptodon barbarensis [=Thyasira barbarensis]

● Thyasira tomeana

Figure 13 – Thyasira biplicata (Philippi, 1836) A – E – growth serie and external surface view of right valves: (A) and (B) juveniles (IM-2012-28332), (C) and (D) intermediate (IM-2012-28332), (E) adult (USNM 822820). (F) dorsal view (USNM 62007). (G) internal surface of right valve (USNM 445882). H – I - right hinge view: (H) right hinge in general view (USNM 94188) and (I) right hinge in dorsal view highlighting the pseudotooth (USNM 611901). (J) SEM of posterior region in external surface of left valve (IM-2012-28330). (K) SEM of central to ventral regions of left valve highlighting the microstructures in external surface in magnification of x10 (IM-2012-28330). (L) SEM of left valve microstructures in external surface (IM-2012-28330). (M) SEM of larval shell (IM-2012-28328).

Figure 14 – Thyasira flexuosa (Monterosato, 1803) A – D – Tellina flexuosa Montagu, 1803, EXEMS Moll3894-9, syntype (Oliver et. al., 2017): (A) and (B) external surfaces of right and left valves, respectively, (C) and (D) internal surfaces of right and left valves, respectively. E and F – growth serie: (E) juvenile, external surface of right valve (USNM 62036) and (F) adult, external surface of right valve (USNM 61941). (G) dorsal view (USNM 337240). (H) internal surface of right valve (USNM 225202). I and J – right hinge view: (I) right hinge in general view (MADIBENTHOS Stn AD242) and (J) right hinge in dorsal view highlighting the pseudotooth (USNM 62027). K and L – SEM of periostracum microstructures in external surface: (K) SEM of periostracum microstructures of anterior-ventral margin on x350 zoom (IM-2012-28325) and (L) SEM of periostracum microstructures of anterior-ventral margin on x800 zoom (IM-2012-28325). (M) SEM of larval shell of T. flexuosa on x500 zoom (IM-2012-28325).

Figure 15 – Thyasira gouldii (Philippi, 1845). A – D – growth serie: (A) juveniles, external surface of right valve (MCZ 15138), (B) intermediate, external surface of right valve (USNM 807293), (C) adult of “elongate variation”, external surface of right valve (USNM 201682), (D) – adult of “high variation”, external surface of right valve (USNM 869475). E – F – hinge view: (E) left hinge (USNM 807293) and (F) right hinge (USNM 807293). (G) dorsal view (USNM 201682). H – I – internal surface: (H) left valves (USNM 807293) and (I) right valves (USNM 807293). (J) SEM of larval shell (USNM 74264). (K) SEM of midline ventral margin, highlighting periostracum microstructure (USNM 843001).

Figure 16 – Thyasira sarsi (Phillippi, 1845). A – D – Cryptodon insignis Verrill & Bush, 1898, USNM 52596, syntype, locality: New Scotia, Canada, Station 238, 238m [Thyasira sarsi (Pjillippi, 1845)]: (A) and (B) external surfaces of right and left valves, respectively, (C) and (D) internal surfaces of right and left valves; E – G - growth serie: (E) juvenile, external surface of right valve (USNM 819915), (F) – intermediate, external surface of right valve (USNM 201682), (G) adult, external surface of right valve (USNM 52733); (H) – dorsal view (USNM 62059). I – J – internal surfaces: (I) right valve (USNM 819910) and (J) left valve (USNM 819913). K – L – hinge view: (K) right hinge (USNM 819910) and (L) left hinge (USNM 819913). (M) SEM of anterior region of external surface of right valve (IM-2012-28326); (N) SEM of anterior-ventral margin, highlighting periostracum microstructure (IM-2012-28326). (O) SEM of larval shell (IM-2012-28334).

Figure 17 – A – D - Thyasira succisa atlantica Payne & Allen, 1991, NHMUK 1990041, holotype, locality: Cape Basin, “Atlantic II”, Station 191, 23°05’S, 12°31.5’E, 1546-1559m [Thyasira succisa (Jeffreys, 1876), Worms, 2017]: (A) and (B) external surfaces

of left and right valves, respectively; (C) and (D) internal surfaces of left and right valves, respectively. E – H – Thyasira atlantica Payne & Allen, 1991, NHMUK 1990039, holotype, locality: North America Basin, “Atlantic II”, Station 124, 37°26.0’N, 63°59.5’W, 4862m [Thyasira tortuosa (Jeffreys, 1881), Worms, 2017]: (E) and (F) external surfaces of left and right valves, respectively; (G) and (H) internal surfaces of left and right valves, respectively. I – L – Leptaxinus var minutus Verrill & Bush, 1898, USNM 48692, holotype [synonymous of Thyasira subovata minuta Payne & Allen, 1991 = Thyasira minuta Payne & Allen, 1991]: (I) and (J) external surfaces of left and right valves, respectively; (K) and (L) internal surfaces of left and right valves, respectively. M – P – Thyasira subovata minuta Payne & Allen, 1991, NHMUK 1990040, holotype, locality: Angola Basin “Atlantic II”, Station 203, 08°48.0’S, 12°52.0’E, 527-542m [synonymous of Thyasira minuta Payne & Allen, 1991 = Leptaxinus minutus Verrill & Bush, 1898]: (M) and (N) external surfaces of left and right valves, respectively; (O) and (P) internal surfaces of left and right valves, respectively. Q – R – Cryptodon equalis Verrill & Bush, 1898, USNM 74302, holotype, locality: Casco Bay, Maine, “Blue Light R/V”, latitude 43.63° and longitude -70.05°, 172m [Parathyasira equalis (Verrill & Bush, 1898, Worms, 2017]: (Q) and (R) external surfaces of left and right valves, respectively S – V – Cryptodon barbarensis Dall, 1890, USNM 96973, holotype, locality: Santa Rosa Island, California, USA “Albatroz R/V”, latitude 34.18° and longitude -120.25°, 50.5m [Thyasira barbarensis (Dall, 1890), Worms, 2017]: (S) and (T) external surfaces of left and right valves, respectively; (U) and (V) internal surfaces of left and right valves, respectively. W – X – Thyasira tomeana Dall, 1901, USNM 108907, syntype, locality: Chile, 18m: (W) and (X) external surfaces of left and right valves, respectively.

ANNEX

Declaração de Direitos Autorais

As cópias de artigos de minha autoria ou de minha co-autoria, já publicados ou submetidos para publicação em revistas científicas ou anais de congressos sujeitos a arbitragem, que constam da minha Dissertação/Tese de Mestrado/Doutorado, intitulada INVESTIGATING THE THYASIRIDAE DALL, 1901 (BIVALVIA, MOLLUSCA) FROM THE SOUTHWESTERN ATLANTIC OCEAN: A STUDY ON THE MORPHOLOGY AND TAXONOMY OF THE BRAZILIAN SPECIES / INVESTIGANDO OS THYASIRIDAE DALL, 1901 (BIVALVIA, MOLLUSCA) DO SUDOESTE DO OCEANO ATLÂNTICO: UM ESTUDO DA MORFOLOGIA E TAXONOMIA DAS ESPÉCIES DO BRASIL, não infringem os dispositivos da Lei n.° 9.610/98, nem o direito autoral de qualquer editora.

Campinas, 2020

Assinatura : Nome do(a) autor(a): Thaís Aparecida Marinho

RG n.° 48.072.915-3

Assinatura : Nome do(a) orientador(a): Prof. Dr. Flavio Dias Passos RG n.° 20.027.359-0

COORDENADORIA DE PÓS-GRADUAÇÃO INSTITUTO DE BIOLOGIA

Universidade Estadual de Campinas

Caixa Postal 6109. 13083-970, Campinas, SP, Brasil

Fone (19) 3521-6378. email: [email protected]

Declaração de Bioética e Biossegurança

Em observância ao §5º do Artigo 1º da Informação CCPG-UNICAMP/001/15, referente a Bioética e Biossegurança, declaro que o conteúdo de minha Dissertação de Mestrado, intitulada “INVESTIGATING THE THYASIRIDAE DALL, 1901 (BIVALVIA, MOLLUSCA) FROM THE SOUTHWESTERN ATLANTIC OCEAN: A STUDY ON THE MORPHOLOGY AND TAXONOMY OF THE

BRAZILIAN SPECIES”, desenvolvida no Programa de Pós-Graduação em Biologia Animal do Instituto de Biologia da Unicamp, não versa sobre pesquisa envolvendo seres humanos, animais ou temas afetos a Biossegurança.

Assinatura: Nome do(a) aluno(a): Thaís Aparecida Marinho

Assinatura: Nome do(a) orientador(a): Prof. Dr. Flavio Dias Passos

Data: 29/07/2020