Charax awa: A new species of Charicid Fish from Maranhão State in northestern Brazil.

Charicids are freshwater Boney Fish related to Piranhas and Tetras that are found across South and Central America and as far north as Mexico and parts of Texas. Members of the genus Charax are medium sized members of this group, reaching a maximum of about 130 mm in length, most abundant in the Andean regions, but also found in southern and western Brazil and parts of the Guyanan Shield. No described member of this genus has a distribution that includes the coastal basins of northeastern Brazil, but there are several records of Fish apparently belonging to this group being found there. 

In a paper published in the journal Zoosystematics and Evolution on 1 February 2018, Erick Cristofore Guimarães of the Programa de Pós-Graduação em Biodiversidade e Conservação, and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Pâmella Silva De Brito of the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Beldo Rywllon Abreu Ferreira, also of the Programa de Pós-Graduação em Biodiversidade e Conservação at the Universidade Federal do Maranhão, and Felipe Polivanov Ottoni, of the Programa de Pós-Graduação em Biodiversidade e Conservação, the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia, the Laboratório de Sistemática e Ecologia de Organismos Aquáticos, and the Programa de Pós-Graduação em Oceanografia at the Universidade Federal do Maranhão, describe a new species of Charax from the Rio Mearim, Rio Munim and Rio Turiaçu basins, of Maranhão State in northestern Brazil.

The new species is named Charax awa, where ‘awa’ is the name used by the Guajá people of Maranhão State to describe themselves. Adults of this species range from 40.2 to120.0 mm in length and are silvery in colour, darker on the upper surface and towards the front, and with blotchy markings on the fins. The upper part of the head is distinctly concave, and the eyes somewhat small. The upper and lower jaws both have enlarged canine teeth as well as rows of smaller, conical teeth. 

 Charax awa, live specimen from a stream at the Miranda do Norte, in the Mearim River Basin of Maranhão State, Brazil. Erick Guimarães in Guimarães et al. (2018).

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A fossil Snake from the Cretaceous of Brazil.

Snakes are generally accepted to have appeared and diversified during the Mesozoic, though their fossil record is not extensive. This is due to their lightly mineralized, easily disarticulated skeletons, which tends to result in Snake fossils, where they are found at all, tend to be poorly preserved and fragmentary. Nevertheless, by the late Cretaceous, a reasonable diversity of Snakes is known from sites across the world. How these early forms are related to modern Snakes is unclear, some retained limbs, and clearly could not be placed in any modern group, others are placed in extinct family Madtsoiidae, which died out in the Pleistocene, but most are too fragmentary for any taxonomic assignment. Fossils which can be placed with reasonable confidence in modern groups appear in the Palaeocene-Eocene.

In a preliminary paper published in the journal Acta Palaeontologica Polonica on 21 January 2013, Anne Hsiou of the Departamento de Biologia at the Universidade de São Paulo, Adriana Albino of the Departamento de Biología at the Universidad Nacional de Mar del Plata and Manuel Medeiros and  Ronny Santos of the Departamento de Biologia at the  Centro de Ciências Biológicas e da Saúde at the Universidade Federal do Maranhão describe a new Snake fossil from the Cenomanian (early Late Cretaceous, 99.6 to 93.5 million years ago) of northeastern Brazil.

The new Snake is named Seismophis septentrionalis, where 'Seismophis' means 'Earthquake-snake' and  'septentrionalis' means 'from the north'. The fossil was discovered at a site called Falésia do Sismito (Cliff of the Earthquake) on Cajual Island in the north of Maranhão State, which itself is in the north of Brazil.

The species is described from a pair of disarticulated mid-trunk vertebrae, not assumed to come from the same animal, though they are distinctive enough to say that they are Snake bones, and probably come from the same species. This is not unusual with Snakes fossils; the animals gain their extreme flexibility from having bones only lightly mineralized and loosely held together with tendons and muscles.

Seismophis septentrionalis, first specimen. Photographs (A1–E1) and schematic drawings (A2–E2), in anterior (A), posterior (B), lateral (C), dorsal (D), and ventral (E) views. Scale bar is 10 mm. Hsiou et al. (2013).

Seismophis septentrionalis, second specimen. Photographs (A1–E1) and schematic drawings (A2–E2), in anterior (A), posterior (B), lateral (C), dorsal (D), and ventral (E) views. Scale bar is 10 mm. Hsiou et al. (2013).

Due to the fragmentary nature of this material, it is not possible to say how this species is related to other Cretaceous or modern Snakes, but it is considered to be the oldest known Snake yet discovered in Brazil.

Map showing the locality where the specimen was found. Hsiou et al. (2013).

See also A cryptic Sea Snake from Australia, New species of Snail-eating Snake from western Panama, New species of Treesnakes from the Comoras, New species of Asian Coral Snake from western India and Velvet Geckos and Broad-headed Snakes; understanding the population structure of a favored prey item in order to help protect an endangered predator.

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