A Pelomedusoid Turtle from the Paleocene–Eocene of Colombia Exhibiting Preservation of Blood Vessels and Osteocytes
We describe a Paleocene–Eocene pelomedusoid turtle from tropical South America in a new fossiliferous locality, from Los Cuervos Formation, at the Calenturitas Coal Mine, Colombia. Although no further systematic precision beyond Pelomedusoides incertae sedis can be supported, the presence of an ischial scar positioned far anteriorly to the anal notch, and a strongly decorated ventral surface of the plastron, indicate that this specimen is potentially related to the bothremydid clade formed by Puentemys–Foxemys. We also demonstrate the potential organic preservation of osteocytes and blood vessels for this specimen, indicating that preservation of soft tissue such as vessels and bone cells in the fossil record is independent of bone type, fossil site, or locality; occurring in different lineages of vertebrates; and that it is even possible to occur in tropical depositional environments during a period of maximum global warming such as the Paleocene–Eocene. Aqui describimos la primera ocurencia de tortugas pelomedusoid del Paleoceno–Eoceno en la parte tropical de Suramérica, en una nueva localidad fósilifera, de la Formación Los Cuervos, en la mina de carbón Calenturitas, Colombia. Aunque, no mayor precisión sistemática puede ser soportada más que Pelomedusoides incertae sedis, la presencia de una cicatriz isquial posicionada muy anteriormente a la escotadura anal y una fuertemente decorada superficie ventral del plastron, indican que el especimen esta relacionado con el clado bothremydido formado por Puentemys–Foxemys. También demostramos la posible preservación orgánica de osteocitos y vasos sanguineos para este especimen; indicando que la preservación de tejidos blandos como vasos y celulas oseas en el registro fósil es independiente del tipo de hueso, sitio fósil o localidad, ocurriendo en diferentes linajes de vertebrados, y que es possible que ocurra en ambientes deposicionales tropicales, durante periodos de maximo calentamiento global como el Paleoceno–Eoceno.Abstract
Resumen
(A) Location of Calenturitas Coal Mine, La Jagua de Ibirico town, Cesar Department, Colombia, where the CCMFC01 pelomedusoid turtle was discovered. (B) Process of extraction of the fossil from the massive block of sandstone in which it was preserved. (C–D) CCMFC01 Pelomedusoides incertae sedis, plastron in ventral view. (E–F) Pattern of decoration on the ventral surface of the right hyoplastron. Abbreviations: abd, abdominal scale; en, entoplastron bone; ep, epiplastron bone; gu, gular scale; hu, humeral scale; hyo, hyoplastron bone; hyp, hypoplastron bone; int, intergular scale; is, ischiac scar; mes, mesoplastron; pec, pectoral scale; ps, pubic scar; xi, xiphiplastron bone.
Osteocytes isolated from a fragment of plastral bone from CCMFC01 Pelomedusoides incertae sedis, after demineralization. All photographs were taken under transmitted light and a × 63 oil lens. Osteocyte morphology following Cadena and Schweitzer, 2012. (A) Flattened osteocyte (FO1), arrows indicate tertiary ramification of filipodia. (B) Flattened osteocyte (FO2), slightly shorter and wider than FO. (C–E) Stellate osteocyte (SO).
Blood vessels isolated from a fragment of plastral bone from CCMFC01 Pelomedusoides incertae sedis, after demineralization. All photographs were taken under transmitted light and × 40, except G, taken with a × 63 oil lens. (A–B) Blood vessels; (C) blood vessel showing three points of ramification; (D) reconstruction of blood vessels shown in C; (E) blood vessel showing three points of ramification; (F) reconstruction of blood vessels showed in E; (G) fragment of blood vessel preserving its three dimensional shape; (H) reconstruction of blood vessels showed in G, showing the process of disintegration of the orange-brown wall in tiny grains. In blue is the diameter considered for the measurements, grey shadow region represents the segment between ramifications considered in the measurements of diameter, black arrows represent potential direction of the blood vessel. Abbreviation: D, diameter of the blood vessel.
Contributor Notes
