Oxydoras undetermined
Creators: name: Carrillo-Briceño, Jorge D.
name: Mora-Rojas, Laura
name: Hendricks, Kimberly
name: Vanegas, Andrés
name: Aguilera, Orangel
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Siluriformes
Doradidae
Oxydoras
Oxydoras undetermined

description: Oxydoras sp.
(Fig. 3 C1-C3).
MATERIAL EXAMINED. — Incomplete neurocranium (ULA-1316).
LOCALITY. — Villavieja Fm. LA-3 (fish bed) (seeFig.1B; Appendix 1).
DESCRIPTION
ULA-1316 is an incomplete neurocranium of 51 mm in length, preserving only the anterior section of the skull (Fig. 3 C1-C3), and is assigned here to Oxydoras. It preserves a complete mesethmoid bone clearly observable in both dorsal and ventral views. It has an elongate arrow-shape with a bifid anterior tip, and a convex profile in lateral view (Fig. 3 C1). In dorsal view, the anterior section of both right and left frontals and both right and left lateral ethmoids are articulated to the mesethmoid; the most proximal section of the anterior cranial fontanelle is also preserved (Fig. 3 C1). The ornamentation of the skull is not well defined, possibly as a result of erosion. In ventral view, the mesethmoid, vomer, remnants of what appear to be lateral ethmoids, and the parasphenoid are preserved (Fig. 3 C2). The vomer has an arrow-shaped anterior section and seems to have reduced anterolateral processes; its posterior section is elongated and narrow, being enclosed in the anterior bifid tip of the parasphenoid.
REMARKS
ULA-1316 possess a mesethmoid bone similar to those present in living and fossil representatives of Oxydoras, which can be differentiated from the mesethmoid bones of any other living (Birindelli 2014) or fossil (see Lundberg et al. 2010) species of doradid. The thorny catfish Oxydoras is represented by three extant species, Oxydoras niger (Valenciennes in Humboldt & Valenciennes, 1821), Oxydoras kneri Bleeker, 1862a, and Oxydoras sifontesi Fernández-Yépez, 1968, from the Amazon, Essequibo, Orinoco and Paraná basins. These species occur over mud in streams and lakes, but are also present in large rivers (Froese & Pauly 2022). The only fossil of Oxydoras known to date corresponds to an isolated mesethmoid bone from the Miocene of Peru illustrated by Lundberg et al. (2010). Although ULA-1316 resembles the skull of the extant O. niger (see Birindelli 2014; Prestes-Carneiro et al. 2019), and/ or the other two living species O. kneri and O. sifontesi, its incomplete and poor state of preservation make it difficult to associate this fossil specimen with any of these extant species. The skulls of the extant species of Oxydoras usually present well-defined ornamentation (see Birindelli 2014: fig. 25); in the case of ULA-1316, the ornamentation pattern is not well-defined or is absent, possibly as a consequence associated with taphonomic processes or erosion of the fossil during its exposure in the outcrop. Due to that, ULA-1316 is tentatively assigned to Oxydoras sp. This fossil specimen from the middle Miocene of the Honda Group, and the isolated mesethmoid bone from the Miocene (Lundberg et al. 2010), are to date the only known fossils of Oxydoras.
description: Published as part of Carrillo-Briceño, Jorge D., Mora-Rojas, Laura, Hendricks, Kimberly, Vanegas, Andrés & Aguilera, Orangel, 2023, New clues on the palaeodiversity of the middle Miocene freshwater ichthyofauna from the Tatacoa Desert, Colombia, pp. 327-351 in Geodiversitas 45 (10) on pages 335-336, DOI: 10.5252/geodiversitas2023v45a10, http://zenodo.org/record/8056044