The freshwater and marine fish faunas of South America are the most diverse on Earth, with current species richness estimates standing above 9100 species. In addition, over the last decade at least 100 species were described every year. There are currently about 5160 freshwater fish species, and the estimate for the freshwater fish fauna alone points to a final diversity between 8000 and 9000 species. South America also has c. 4000 species of marine fishes. The mega-diverse fish faunas of South America evolved over a period of >100 million years, with most lineages tracing origins to Gondwana and the adjacent Tethys Sea. This high diversity was in part maintained by escaping the mass extinctions and biotic turnovers associated with Cenozoic climate cooling, the formation of boreal and temperate zones at high latitudes and aridification in many places at equatorial latitudes. The fresh waters of the continent are divided into 13 basin complexes, large basins consolidated as a single unit plus historically connected adjacent coastal drainages, and smaller coastal basins grouped together on the basis of biogeographic criteria. Species diversity, endemism, noteworthy groups and state of knowledge of each basin complex are described. Marine habitats around South America, both coastal and oceanic, are also described in terms of fish diversity, endemism and state of knowledge. Because of extensive land use changes, hydroelectric damming, water divergence for irrigation, urbanization, sedimentation and overfishing 4-10% of all fish species in South America face some degree of extinction risk, mainly due to habitat loss and degradation. These figures suggest that the conservation status of South American freshwater fish faunas is better than in most other regions of the world, but the marine fishes are as threatened as elsewhere. Conserving the remarkable aquatic habitats and fishes of South America is a growing challenge in face of the rapid anthropogenic changes of the 21st century, and deserves attention from conservationists and policy makers.

Aim To present an updated database of fish species recorded on south‐western Atlantic reef environments and to explore the ecological drivers of the structure, the latitudinal gradient of biodiversity and the centre of endemism in this peripheral province. Location South‐western Atlantic (SWA): Brazilian and Argentinian Provinces. Methods A database composed of 733 fish species along 23 locations in the SWA (00°55′ N to 43°00′ S) was compiled based on primary data, literature and museum records. Cluster and beta diversity analyses were carried out to evaluate faunal overlaps among locations and subprovinces. “Target‐area‐distance effect” and “stepping stones dispersal” hypotheses for assemblage composition were tested through Mantel tests. Relationships between the distribution patterns and ecological traits of reef fish species were investigated through generalized linear mixed‐effect models. Results Out of the 733 fish species, 405 are SWA resident reef fishes, of which 111 (27%) are endemics and 78 are threatened with extinction. Cluster analysis detected six subprovinces in the SWA structured following the target‐area‐distance model, and with no evidence for a latitudinal gradient in diversity. The greatest overall richness and endemic species richness were found in the east–south‐eastern region. Depth range, habitat use and body size were the main drivers of SWA reef fish assemblage structure. Main conclusions The Brazilian and Argentinian coasts constitute different provinces structured by oceanographic barriers and environmental filters. Similarities among oceanic islands indicate connectivity driven by stochastic and ecological factors. Species richness and endemism indicate that peripheral provinces may also bear centres of origin and biodiversity, patterns driven by parapatric/ecological speciation and the overlap between tropical and subtropical reef fish species. Ecological drivers of reef fish distribution, such as habitat specialization and body size, support hypotheses of speciation in the periphery. New approaches for spatial planning, marine protected areas and off‐reserve marine management are essential for the conservation and sustainability of SWA reef fishes.

LETTERSUndercover. Many Alpheidae shrimps live deep in the reef and are impossible to collect nonlethally. Published by AAAS

The Baurusuchidae is one of the most representative families of Crocodyliformes from the Upper Cretaceous of Brazil. Amongst the ten recognized species of the family in the world, eight are recovered from Bauru Basin outcrops. Despite its relative diversity and abundance, information on postcranial elements of species of the family is scarce in the literature. Campinasuchus dinizi is a baurusuchid found in the neocretaceous redstones of the Adamantina Formation of Bauru Basin (SE Brazil). The postcranial skeleton of the species is described based on five specimens, with the following bone elements identified: proatlas, intercentrum of the atlas; pedicles of the atlas; odontoid process; axis; three postaxial cervical vertebrae; nine dorsal vertebrae; eight caudal vertebrae; seven ribs and gastralia fragments; eleven chevrons; twelve osteoderms; pectoral and pelvic girdle; humerus; radius; ulna; manus; femur; tibia; fibula; and pes. Campinasuchus dinizi has the smallest and most delicate postcranial skeleton when compared with examined Baurusuchidae, with an inferred body mass of approximately 28 kg. Some elements of the postcranial skeleton of C. dinizi are also comparatively more robust (e.g. neural spines higher and more developed; vertebral body thicker; pelvic girdle more proeminent; limbs more elongated) than in some notosuchians, such as Mariliasuchus amarali and Notosuchus terrestris, and extant crocodyliforms such as Caiman latirostris and Melanosuchus niger. The mostly straight limbs of C. dinizi indicate a terrestrial habit, and suggests a semi-upright to upright posture during locomotion. The first descriptions of postcranial bones of a young specimen of C. dinizi and osteoderms of Pissarrachampsinae as well as comments about the distinct anatomy of some of those elements are also presented.

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The recessus lateralis, a complex structure in the otic region of the skull that is probably associated with detection and analysis of small vibrational pressures and displacements, is widely recognized as a synapomorphy of the Clupeiformes. The Clupeiformes includes the Denticipitoidei, with one living species, Denticeps clupeoides, and the Clupeoidei, with about 360 living species commonly known as herrings and anchovies. Comparisons between details of the recessus lateralis of the Clupeoidei and Denticipitoidei, and the sensory cephalic canals of other teleosts, lead to hypotheses of a series of transformations of the cephalic sensory canals. Treating that complex as a single binary 'presence vs. absence' character as was traditional practice obscures important phylogenetically informative variation. Specific synapomorphies in that system exist for the Clupeiformes and the Clupeoidei. Hypothesized synapomorphies in the recessus lateralis for the Clupeiformes are the presence of a dilated internal temporal sensory canal in the pterotic, a postorbital branch of the supraorbital sensory canal located in a bony groove in the lateral wing of the frontal, and the terminal portions of preopercular and infraorbital sensory canals closely positioned. Hypothesized synapomorphies for the Clupeoidei are the presence of a postorbital branch of the supraorbital sensory canal located deep within the body of the lateral wing of the frontal, with the distal portion of that branch totally internal on the cranium, and the expanded distal portion of the postorbital branch of the supraorbital sensory canal. The homology of the sinus temporalis of Clupeoidei, and of the dermosphenotic of both Denticeps and the Clupeoidei, with those of other teleosts is also considered.

The Stephanoberycoidei includes 23 genera and c. 94 species of deep-sea teleosts commonly known as bigscales, pricklefishes, gibberfishes and whalefishes. Stephanoberycoidei is one of the least known groups of deep-sea fishes, in spite of their apparent relative abundance in meso and bathypelagic depths. Nine species of the Stephanoberycoidei are reported here for the first time in Brazilian waters, and most of them represent new range extensions for the south-western Atlantic Ocean. Those species are Melamphaes polylepis, Melamphaes typhlops, Poromitra sp. and Scopeloberyx robustus (Melamphaidae), Acanthochaenus luetkenii and Stephanoberyx monae (Stephanoberycidae), Rondeletia bicolor and Rondeletia loricata (Rondeletiidae) and Gyrinomimus sp. (Cetomimidae). Occurrences of the pricklefish Scopelogadus mizolepis (Melamphaidae), the gibberfish Gibberichthys pumilus (Gibberichthyidae) and the velvet whalefish Barbourisia rufa (Barbourisiidae) are confirmed in the Brazilian exclusive economic zone, but previously published records of Poromitra capito and Melamphaes simus (Melamphaidae) in the region most likely represent misidentifications. Validities of the recently described Poromitra kukuevi and Poromitra indooceanica are discussed in light of new specimens of the genus collected in the south-western Atlantic Ocean. An identification key for the 13 species of Stephanoberycoidei reported off Brazil is also provided.

The Chirocentridae is a family of highly specialized large predatory clupeomorphs composed of two species from coastal waters of the Indian and western Pacific Oceans. Peculiarities of the anatomy of these fishes have puzzled ichthyologists who attempted to resolve their phylogenetic relationships. Despite controversy, it is currently accepted that the Chirocentridae is a family of Clupeiformes, included with the Clupeidae in the superfamily Clupeoidea. New data support an alternative hypothesis. Seven previously unreported derived character states from the suspensorium, branchial arches, and infraorbitals strongly indicate a hitherto unsuspected sister group relationship between the Chirocentridae and Engrauloidea, which comprises approximately 140 species of the commercially important fishes known as anchovies. These are character states: (1) the anterior margin of metapterygoid located anterior to the quadrate; (2) the ventral limb of hyomandibula and quadrate not separated by the metapterygoid; (3) the posterodorsal margin of metapterygoid in line with the condyle of articulation of the hyomandibula with the opercle; (4) the presence of a laminar outgrowth of the anterior margin of the quadrate; (5) the endochondral portion of the quadrate in the shape of an isosceles triangle; (6) the presence and arrangement of autogenous tooth plates on ceratobranchials 1 to 3; and (7) posterior region of infraorbital 1 well developed and extending along the ventral margin of infraorbital 2. Three of those character states are further modified and hypothesized as synapomorphies of the Engrauloidea: (1′) a substantial portion of the metapterygoid situated anterodorsal to the quadrate, (2′) articulation between the ventral limb of the hyomandibula and the quadrate, and (7′) infraorbitals 1 and 3 articulating by means of a well-developed laminar process of the posterior region of infraorbital 1. The separation of the dorsal, paired elements of the branchial arches of the Chirocentridae and representative Engrauloidea is apomorphic within the Clupeoidei, and constitutes circumstantial evidence for the sister group relationship between those clades. Microphagy within the Engrauloidea is secondary, homoplastic to the same condition present in other clades of the Clupeiformes. The decomposition of character complexes into discrete morphological characters and its use in phylogenetic inference is discussed. The sister group relationship between the Chirocentridae and Engrauloidea renders the Clupeoidea paraphyletic. A new classification of the Clupeoidei, with the inclusion of the Chirocentridae in the Engrauloidea, is proposed.