Potamotrygonidae, Garman, 1877

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, Geodiversitas 45 (10), pp. 327-351 : 332

Potamotrygonidae indet.

( Fig. 2 B1-G2).

EXAMINED BODY PARTS. — Bucklers and caudal spines.

MATERIAL EXAMINED. — Museo de La Tormenta, two isolated teeth ( VPPLT 10000 , 10001 ); Museo de Historia Natural La Tatacoa, 13 isolated dermal bucklers ( VPPLT-668 , 805 , 1226 [no. 2], 1239 , 1245 [no. 2], 1415 , 1440 , 1444 , 1452 [no. 2], 1481 ), and four isolated caudal spines ( VPPLT-042 , 1425 , 1430 , 1485 ) .

LOCALITIES. — La Victoria Fm. Diomatal-Museo La Tormenta (VPPLT-1481, 1485); Morrongo 1 (VPPLT-1415, 1452), Morrongo 2: (VPPLT-805, 1226, 1239, 1245, 1430, 1440); Km-121 (VPPLT-042, 1425, 1444). — Indeterminate Fm. Santa Barbara 2 (VPPLT-668) (see Fig. 1 ; Appendix 1). The two isolated teeth (VPPLT 10000 and VPPLT 10001) do not have precise information about their locality (presumably Diomatal-Museo La Tormenta).

DESCRIPTION

The indeterminate potamotrygonid isolated teeth described and illustrated by Lundberg (1997: fig. 5.1), plus another group of teeth were observed but not photographed or described in detail by one of the authors (JDCB) during a visit to the Academy of Natural Sciences of Drexel University, Philadelphia (ANSP), where they are temporarily housed. A detailed description of at least five of the isolated teeth housed in the ANSP is presented by Lundberg (1997). Most of these specimens in the ANSP, as well as two other isolated teeth reported here from the Museo de La Tormenta ( Fig. 2 A1, A2), are smaller than 3 mm wide and are characterized by a crown that is higher than the root with a middle transverse crest that separates the labial and lingual sides. The labial side of the crown is coarsely ornamented in specimens that do not show a wear pattern. In some cuspidate teeth, the crest is lingually elongated and forms a distinctive triangular cusp. The root is a typical holaucorhize type with two rounded and basal flattened lobes (see Fig. 2 A1-A2; Lundberg 1997: fig. 5.1).

The dermal bucklers are up to 3.5 mm in diameter and circular and semi-circular in shape( Fig.2 B1-F).Three specimens are fused bucklers (up to 33 mm in length) of ovoidal/or irregular shape (e.g., Fig. 2 C, E). The bucklers are characterized by an erected curved crown with a central and small tip. Abundant ridges and deep furrows from the base of the central tip to the basal edges of the buckler ornament the crown. In some specimens, abundant rounded and micro like-bucklers (up to 2 mm in diameter) are present in the crown ( Fig. 2 B1-B2, D-F). Of the four caudal spines, only two specimens are relatively complete (58 and 64 mm in length). All the caudal spines preserve their denticles at the lateral margins, the central ridge, and the central groove on the ventral and dorsal sides, respectively ( Fig. 2 G1-G2).

REMARKS

The only previous reports of stingrays from the Honda Group include the few isolated teeth (from the Fish Bed layer) and the fragmented caudal spines reported as indeterminate potamotrygonids by Lundberg (1997). The teeth described by Lundberg (1997), and the two isolated teeth reported here ( Fig. 2 A1-A2), have morphological features that more closely resemble those teeth of the extant and fossil Potamotrygon species than other genera within the Potamotrygonidae (seeAdnet et al. 2014; Carrillo-Briceño et al. 2021a). It is best to assign these specimens from the Honda Group to cf. Potamotrygon , and we believe that new specimens and future detailed studies are necessary for more accurate taxonomic assignments.

The preservation of the caudal spines does not allow an assignment beyond Potamotrygonidae .The dermal bucklers are recorded here for the first time from the Honda Group. These dermal bucklers are similar in size and morphology to those of fossil potamotrygonids from the late Miocene of Argentina and Brazil ( Brito & Deynat 2004), as well as some extant Potamotrygon species ( Deynat & Brito 1994). In accordance withBrito & Deynat (2004), we believe that the dermal bucklers from the Honda Group can be tentatively identified as indeterminate potamotrygonids; although the chances that these belong to Potamotrygon are very high (see Deynat & Brito 1994). Still there is poor knowledge of the broader dermal elements and dental patterns among the more than 35 potamotrygonid species (four genera) from different South American river basins.These stingrays inhabit a wide range of environments, including lakes, still waters, and flowing rivers, commonly associated on sandy substrates ( Lasso et al. 2014; van der Sleen & Albert 2018).

Figures

FIG. 2. — Stingrays (A1-G2) and cichlids (H1-L2) from the Honda Group: A1, A2, cf. Potamotrygon sp. tooth (VPPLT 10000); B1-F, isolated dermal bucklers; B1, B2, VPPLT-1415; C, E, VPPLT-1245; D, VPPLT-1126; F, VPPLT-1239; G1, G2, isolated caudal spines (VPPLT-42) of Potamotrygonidae indet.; H1-H4, left dentary of cf. Astronotus sp. (VPPLT-668A); I1, I2, left dentary of the extant Astronotus ocellatus (Agassiz, 1831) (ANSP s/n); J1-J3, left dentary of cf. Cichla sp. (VPPLT-668B); K1-K3, left dentary of the extant Cichla Bloch & Schneider, 1801 (PIMUZ A/I 4897); L1, L2, indet. cichlid anal spine (VPPLT-1164). Views: L1, anterior; B, C-G1, H3, I2, J3, K3, dorsal; A1, labial; A2, lingual-lateral; H1, I1, J2, K1-K2, left lateral; L2, lateral; B2, profile; H4, J1, right lateral; G2, H2, ventral. Scale bars: A, 0.5 mm; B, 1 cm; C, E, I1, J, K2, 5 mm; D, H, 7 mm; F, K1, L, 6 mm; G, K3, 4 mm; I2, 3 mm.

FIG. 1. — Geographical position (A) of the Honda Group’s stratigraphic section (B) at La Venta site placed in the Upper Magdalena River Valley, Colombia. For details on the localities’ geographic coordinates and stratigraphic position, please see Appendix 2.