Contribution to the knowledge of fossil fishes (Chondrichthyes and Actinopterygii) from Quaternary deposits of the Pelotas Basin, Southern Brazil

Resumo

Fossils of fishes represented by disarticulated, strongly mineralized and abraded skeletal elements, are relatively common in surface deposits of the Pelotas Basin along the coastal plain of the State of Rio Grande do Sul (CPRS), in southern Brazil, especially on storm wave-generated Konzentratt-Lagerstätten known as concheiros formed on the beach. Here, new specimens of chondrichthyan and actinopterygian fishes are presented from Quaternary (Middle Pleistocene to Holocene) coastal depositional environments that increase the diversity and distribution of fossil fishes in the Pelotas Basin. The fossils found along the beaches consist of dermal bucklers of rays (Dasyatidae), new specimens of Sciaenidae that include otoliths of Micropogonias furnieri and disarticulated but associated skeletal elements of Pogonias cromis, unidentified scales, opercles and one hyperostotic vertebra, and the first record of porcupine fishes (Diodontidae) in the Pelotas Basin, represented by jaw elements. Other fossils include the first Pleistocene fishes from marine and fluvial deposits exposed along Chuy Creek, represented by one hyperostotic pterygiophore of P. cromis and disarticulated but associated bones of catfishes (Siluriformes), including one partial skeleton associated with a fossil (probably mammalian) rib fragment reworked by fluvial erosion. Other fossils include one broken vertebral centrum from subsurface Pleistocene marine or lagoon deposits located to the east of the creek, and a vertebra of cf. P. cromis from Mirim Lagoon. Differences in representativity of chondrichthyans and actinopterygians seem related to taphonomic destruction of less resistant and/or skeletal elements of smaller species in wave-dominated marine settings, whereas freshwater/lagoon environments favor better preservation of fish remains.

Keywords: fish fauna, Dasyatidae, Pimelodidae, Sciaenidae, Diodontidae, concheiros.