Before the flood: Miocene otoliths from eastern Amazon Pirabas Formation reveal a Caribbean-type fish fauna

Abstract

a b s t r a c tThe Pirabas Formation of Early Miocene age represents the final stage of the central western Atlantic carbonate platform in northeastern South America, predating the emplacement of the Amazon delta system. The otolith-based fossil fish fauna is represented by 38 species typical of a shallow marine environment. A total of 18 species are described new to science from the families Congridae, Batrachoididae, Bythitidae, Sciaenidae and Paralichthyidae. The fish fauna was associated with high benthic and planktic primary productivity including seagrass meadows, calcareous algae and suspension-feeders. The break of todays shallow marine bioprovince at the Amazonas delta mouth is not evident from the fish fauna of the Pirabas Fm., which shows good correlation with the Gatunian/proto-Caribbean bioprovince known from an only slightly younger time window in Trinidad and Venezuela. Differences observed to those Early Miocene faunal associations are interpreted to be mainly due to stratigraphic and geographic and not environmental differences. We postulate that the emergence of the Amazonas river mouth close to its present day location has terminated the carbonate cycle of the Pirabas Fm. and pushed back northwards a certain proportion of the fish fauna here described.

Bayesian divergence-time estimation with genome-wide SNP data of sea catfishes (Ariidae) supports Miocene closure of the Panamanian Isthmus

“…The posterior distribution of species trees is illustrated in Figure 5 Aguilera et al 2013Aguilera et al , 2014; see Table 7). Branch color indicates reconstructed geography: Caribbean; green, or Tropical Eastern Pacific (TEP); dark blue.…”

“…Regardless of the exact relationships of Notarius quadriscutis in our species tree, our analyses suggest that the lineage originated around the time of the crown divergence of Notarius (11.61 Ma; 95% HPD: 13.23-10.21 Ma) and is thus younger than the earliest fossils assigned to the genus, Notarius sp. (Early Miocene; Aguilera et al 2014).…”

Neogene sharks and rays from the Brazilian ‘Blue Amazon’

“…Large specimens were collected directly from the outcrops, following the classical stratigraphic successions of the Pirabas Formation presented previously in several works [ 6 , 19 , 27 , 53 – 57 ]. In addition, 30 kg of sediments were collected in the Atalaia section, screen-washed and sieved with 0.5, 1.0 and 2.0 mm open mesh-size, dried and picked under a stereomicroscope to examine the presence and relative abundance of microdental elements.…”

“…Its fauna rich in species and abundance is well known [ 10 , 22 ] and a distinct tropical Western Central Atlantic subprovince was proposed for the early Miocene, based on the benthic marine invertebrates (mollusks, crustaceans, echinoids, corals and bryozoans). The formation also yielded many fish remains, among them elasmobranchs [ 23 – 26 ], and most recently a very diverse shallow marine and brackish teleostean fauna was reported [ 6 , 27 , 28 ].…”

Record of the rare Caribbean mud eel, Pythonichthys sanguineus (Heterenchelyidae, Anguilliformes), in the region of the Amazon Reef

“…In this context, the Amazonian-Orinoco plume, formed by the rearrangements of the hydrographic basins of the Amazon (Shepard et al 2010) and the Orinoco (Rod 1981), during the middle to late Miocene (7.2 mya) (Figueiredo et al 2009;Hoorn et al 2017), has been recognized as an important barrier to the dispersal of coral reef fishes of the Caribbean and Brazil (Bernal and Rocha 2011). Aguilera et al (2014) described Pythonichthys pirabasensis based on a fossil from the Aquitanian period of the early Miocene (20.4-23.0 mya), from the Pirabas Formation of Atalaia Beach (municipality of Salinópolis, in the northern Brazilian state of Pará) and concluded that the current interruption of the shallow marine bioprovince, found off the Amazon delta cannot be perceived in the fish fauna of the Pirabas Formation, which is closely related to that of the Gatunian/proto-Caribbean bioprovince (Petuch 1982(Petuch , 2013Landau et al 2008). The shift of the mouth of the Amazon River, close to its present day location, has terminated the carbonate cycle of the Pirabas Formation, pushing the Pirabas fish fauna northwards, including Pythonichthys and the congrid genus Paraconger Kanazawa 1961, also captured with the Pythonichthys specimens described herein (A.P.…”