Quaternary equatorial Atlantic deep-sea ostracodes: evidence for a distinct tropical fauna in the deep sea

Abstract

Low-latitude, deep-sea faunas remain poorly understood and described. Here, we systematically describe Quaternary deep-sea ostracodes from the Ocean Drilling Program (ODP) Site 925 (Ceara Rise; 4°12.2'N, 43°29.3′W; 3040 m water depth) in the equatorial Atlantic Ocean. Twenty-six genera and 52 species were examined and illustrated with high-resolution scanning electron microscopy images. Six new species are described herein: Pseudocythere spinae, Hemiparacytheridea zarikiani, Pedicythere canis, Xylocythere denticulata, Paracytherois obtusa, and Poseidonamicus sculptus. The results show that deep-sea ostracodes have a tropical faunal element that is distinctive from higher latitude ostracodes, and that is globally distributed in low latitudes. This tropical faunal component is possibly a Tethyan legacy of a fauna that was widely distributed in tropical and extratropical latitudes in deep waters during greenhouse conditions in the Cretaceous and early Cenozoic. Global cooling thereafter shrank its distribution, limiting it to tropical latitudes, perhaps with the relatively warm uppermost bathyal area acting as the source or refuge of this faunal component. Because similar present-day biogeographic patterns (i.e., presence and wide distribution of tropical deep-sea fauna) are known in other deep-sea benthic groups, this scenario might be applicable to the deep-sea benthos more broadly. UUID: http://zoobank.org/552d4cb2-c0db-463a-ae3f-b2efcc0985df.

Paleoenvironmental significance of Benthic Foraminifera and Ostracoda from the late Quaternary of the Ceará Basin, Brazilian Equatorial Margin

“…Another species of the genus herein recorded, Ambocythere sp., differs in having a conspicuous perforate spine near the posterior cardinal angle and subdued ornamentation. The nearest study on deep-sea ostracods was carried out at ODP site 925, Ceará Rise (Yasuhara et al 2009a(Yasuhara et al , 2021; however, the taxonomic similarity between the two sites is represented only by Argilloecia labri, possibly due to the low abundance of the material herein studied.…”

“…The suprageneric taxonomy of Ostracoda followed Liebau (2005). Previous studies on Quaternary Ostracoda also were consulted to identify taxa at the species level (e.g., Brandão 2004a, 2004b, 2010, Yasuhara et al 2009b, Maia et al 2021, Yasuhara et al 2021. Finally, the pteropods were identified according to Janssen (2012), and references therein.…”

Sight and blindness: The relationship between ostracod eyes, water depth, and light availability in the Arctic Ocean

“…Despite such uncertainty, it is well-established on the basis of living examples that ornamented ostracods of certain families (particularly the Hemicytheridae and Trachyleberididae) commonly have eyes and prominent eye tubercles in shallowmarine species (Tanaka 2005(Tanaka , 2006. In contrast, most deep-sea species lack eye tubercles, not only in these ornamented families (Yasuhara et al 2015) but also in general (e.g., Yasuhara et al 2009Yasuhara et al , 2021Alvarez Zarikian 2015), indicating their blindness there. Thus, the presence/absence of eye tubercles can be used as an approximate proxy for sightedness/blindness.…”