Early Devonian (Late Emsian) shark fin remains (Chondrichthyes) from the Paraná Basin, southern Brazil

Abstract

We report on the pioneering discovery of Devonian fish remains in the Paraná Basin, which represents the southernmost record of fishes from that period in mainland South America. The material comes from an outcrop at the lower portion of the São Domingos Formation, within Sequence C of the Paraná-Apucarana sub-basin in Tibagi, State of Paraná. Marine invertebrates are abundant in the same strata. The dark colored fish remains were collected in situ and represent natural moulds of partially articulated shark fin rays (radials). No elements such as teeth or prismatic cartilage have been preserved with the fins rays. This can be attributed to the dissolution of calcium-phosphatic minerals at the early stages of fossilization due to diagenetic processes possibly linked to strong negative taphonomic bias. This may have contributed to the fact that fishes remained elusive in the Devonian strata of this basin, despite substantial geological work done in the Paraná State in recent decades. In addition, the scarcity of fish fossils may be explained by the fact that the Devonian rock deposits in this basin originated in a vertebrate impoverished, cold marine environment of the Malvinokaffric Realm, as previously suspected.

The oldest Devonian circumpolar ray-finned fish?

“…The peculiarity of high-latitude southern faunas in the Early and Middle Devonian is well established, with Malvinokaffric vertebrates represented almost exclusively by fragmentary chondrichthyan (including acanthodian) and placoderm remains from southern South America (e.g. Brazil and Bolivia) [10,11,45], the Falkland Islands [46] and South Africa [47]. Even in Late Devonian high-latitude localities postdating dissolution of the Malvinokaffric Realm, actinopterygians remains rare and represented mostly by fragments of little taxonomic value [47][48][49][50].…”

“…Sites at low palaeolatitudes yield the majority of Early-Middle Devonian osteichthyans [9]. Fishes from high palaeolatitude deposits of that age include acanthodians, chondrichthyans and placoderms [10,11], with bony fishes only well represented in the Late Devonian [12]. This mirrors the taxonomically depauperate Early-Middle Devonian invertebrate communities from southern high latitudes characterizing the Malvinokaffric Realm, a central feature of Devonian biogeography [13][14][15].…”

Paleoenvironments of a regressive Devonian section from Paraná Basin (Mato Grosso do Sul state) by integration of ichnologic, taphonomic and sedimentologic analyses

“…The Lower Devonian macrofossil content is also similar both in Mato Grosso do Sul and Paraná states. Except by fish remains only preserved in southern part of the basin (e.g., Richter et al 2017), all groups are distributed in the basin, corresponding to the typical association of the Malvinokaffric Realm (dominance of brachiopods Orbiculoidea, lingulids, Australospirifer, Australocoelia, Schuchertella, with subordinated mollusks bivalves and gastropods, tentaculitids, conulariids and crinoids). The decline in diversity during the Middle Devonian (Eifelian), as observed by Bosetti et al (2012), was not yet observed in Mato Grosso do Sul state.…”

“…The Devonian macrofossils from Paraná Basin have been widely studied under different approaches, such as taxonomy (e.g., Clarke 1913, Kotzian 1995, Leme et al 2004, Scheffler & Fernandes 2007a, 2007b, Scheffler et al 2013, Richter et al 2017, biogeography (Melo 1988) and taphonomy (Simões et al 2009, Rodrigues et al 2003, Bosetti et al 2011, 2012, Zabini et al 2010, Horodyski et al 2014. However, most of those studies were developed in the south part of the Paraná Basin (Paraná State, Brazil, Fig.…”

EDITORIAL NOTE: Collection of Paleontology Papers in honor of the Centenary of the Brazilian Academy of Sciences

“…Over 70 authors from different countries were involved in this volume, showing the increasing international integration of Brazilian paleontologists.Overall, the study of fossils has gotten more and more diversified, which has also been represented by the papers recently published in the AABC. This includes new discoveries of rare specimens that expand the distribution of certain groups (e.g., Richter et al 2017), studies on how Brazilian material might provide answers to more general questions such as the extinction of dinosaurs (e.g., Brusatte et al 2017), discovery of distinct pattern of dental replacement in lizards (e.g., Chavarría-Arellano et al 2018), and efforts to better understand complicated questions like the interpretation of cranial structures (e.g., Cheng et al 2017) and new feeding modes (Kellner and Calvo 2017) of flying reptiles.But that is not all. Brazilian researchers have also been concerned with ethical questions regarding on how specimens are collected (Mansur et al 2017), a problem that has been addressed by several scientists around the world (e.g., Lipps and Granier 2009, MacFadyen 2011).Paleontologists working in Brazil have also applied distinct techniques in the study of fossils.…”