On the Miocene Cyprideis species flock (Ostracoda; Crustacea) of Western Amazonia (Solimões Formation): Refining taxonomy on species level

Abstract

The Miocene mega-wetland of western Amazonia holds a diverse, largely endemic ostracod fauna. Among them, especially the genus Cyprideis experienced a remarkable radiation. Micropalaeontologic investigations of a 400 m long sediment core (~62 km SW Benjamin Constant, Amazonia, Brazil) permitted a taxonomic revision of about two-thirds of hitherto described Cyprideis species. We evaluate the diagnostic value of shell characters and provide an extensive illustration of the intraspecific variability of species. Based on comparative morphology, the 20 recorded Cyprideis species are arranged in groups and subgroups. The “smooth” group comprises C. amazonica, C. kotzianae, C. kroemmelbeini, C. machadoi, C. multiradiata, C. olivencai, C. paralela and C. simplex; the “ornate” group C. curucae nom. nov., C. cyrtoma, C. aff. graciosa, C. inversa, C. ituiae n. sp., C. matorae n. sp., C. minipunctata, C. munoztorresi nom. nov., C. pebasae, C. reticulopunctata, C. schedogymnos and C. sulcosigmoidalis. Five species have been revalidated, two renamed, two synonymised and two are new descriptions. Along with 10 further formally established species, for which a review is pending, Cyprideis keeps at least 30 endemic species in that region during Miocene times. Up to 12 Cyprideis species have been found to occur sympatrically, representing >90 % of the entire ostracod fauna. Ostracod index species enable a biostratigraphic allocation of the well succession to the Cyprideis minipunctata to Cyprideis cyrtoma biozones, corresponding to a late Middle to early Late Miocene age (late Serravallian–early Tortonian).

The ostracods from Solimões Formation, Brazil: an alternative biostratigraphic zonation for the Neogene of Amazonia

“…As in Gross et al (2014), the zones proposed herein present better correlation with those conceived by Wesselingh et al (2006) and Wesselingh & Ramos (2010). Regarding chronostratigraphic positioning of the 1-AS-33-AM drillcore based on the palynological data by Leite et al (2017), a divergence is clearly observable.…”

“…C. amazonica, Cyprideis Figure 1. Location of the well 1-AS-33-AM in the Solimões Basin, Brazil, along with several wells and outcrops from the western Amazon region that yielded ostracods in previous studies (Muñoz-Torres et al, 2006;Gross et al, 2014Gross et al, , 2015 Wesselingh & Ramos (2010) and palynological zonation by Leite et al (2017) for the 1-AS-33-AM drillboring, the Cyprideis caraionae Range Zone is inserted into the Crassoretitriletes palinozone, lower Serravallian, middle Miocene. Muñoz-Torres et al (2006) erected Cyprideis caraionae as a concurrent range zone for the middle Serravalian Stage, and this interpretation is followed herein to encompass the amplitude of the Cyprideis caraionae in the 1-AS-33-AM drillcore.…”

“…The present analysis resulted in the identification of 12 ostracod species, nine of them, after the most recent review by Gross et al (2014), belonging to the genus Cyprideis Jones, 1857: Cyprideis aff. C. amazonica , Cyprideis caraionae Purper & Pinto, 1985, Cyprideis aff.…”

A 60-million-year Cenozoic history of western Amazonian ecosystems in Contamana, eastern Peru

“…Most of these localities represent a series of snapshots in the history of Proto-Amazonia and/or glimpses into the evolutionary history of a given taxonomic group, which are not easily correlated temporally, although synthetic works have begun to pave the way for broader analyses: see Hoorn (1993) and Jaramillo et al (2011) for Neogene and Cenozoic palynostratigraphy, respectively; Wesselingh et al (2006) for Miocene mollusks; Sheppard and Bate (1980), Muñoz-Torres et al (1998), Ramos (2006), Wesselingh and Ramos (2010), or Gross et al (2013Gross et al ( , 2014 for ostracods and/or foraminifers; Lovejoy et al (1998Lovejoy et al ( , 2006, Monsch (1998), Brito and Deynat (2004), Brito et al (2007), and Lundberg et al (2010) for fish evolution and distribution; Negri et al (2010) for mammals and birds; Hovikoski et al (2010), Lundberg et al (2010), Boonstra et al (2015) for sedimentological and paleontological arguments of Miocene marine incursions.…”

Middle Jurassic Tethyan–Boreal ostracod faunal links: a case study from the Callovian of Portugal

“…The cooccurrence of three biological species of the same genus was explained by the possession of different reproductive and growth strategies, and also by the possibility that some very local bottomwater habitats were close to freshwater salinity. Other examples of sympatric speciation, perhaps less clear because from non-marine environments, concern Miocene Cyprideis Jones from Amazonia (Gross et al 2014) where up to 12 species are considered to occur sympatrically, and Cyprideis from Austria (Gitter et al 2015) where four apparently co-existing Cyprideis species are referred to different microhabitats based on salinity preferences. Whatever the biological or ecological rationale behind these cases, on present evidence we prefer to recognize three morphotypes of multiforma which may, or may not, represent three co-existing sympatric species reflecting some kind of original niche-partitioning and not a simple taphonomic signal.…”