Pleurodira turtles from the Candeleros Formation (Cenomanian) at ¨La Buitrera¨, Neuquén Basin, Rio Negro Province.

MANIEL IGNACIO JORGE

Jornada; RCAPA 2022; 2022

New remains of Pleurodira turtles came out from Candeleros Formation (Cenomanian) exposed in the ¨La Buitrera¨ locality (Río Negro Province, Argentina). These materials were sampled from two sites within La Buitrera Paleontological Area (LBPA). One of them comes from the La Buitrera site. This new specimen (MPCA PV 1126) consists of a nuchal bone, a first neural, three partially costal bones, a hypoplastron, a left xiphiplastron, a xiphiplastral tip, and an epiplastral fragment. The others specimen come from MED 4 sites (MPCA PV 1127 and MPCA PV 1128), a place close to Cañadon de las Tortugas site, where Prochelidella buitreraensis is recorded. These materials belong to the same taxon but are represented by two specimens composed of carapace remains highlighting a nuchal bone, neural bones, peripheral bones, costal bones, and fragmentary epiplastron bone. The size of these new materials is bigger than Prochelidella buitreraensis holotype. MPCA PV 1127 and MPCA PV 1128 are referred to here as cf. P. buitreraensis by a nuchal bone wider than long with a trapezoidal cervical scute and a well-developed axillary buttress not angled, meanwhile MPCA PV 1126 is a Chelidae indet. by the presence of a pelvic girdle sutured to the carapace (inferred by the presence of a pubis scar and ischiadic scar on xiphiplastron) and a nuchal bone wider than long with a cervical scute. Differs from Prochelidella in a nuchal bone wider than long, more similar to that observed in Yaminuechelys or Rionegrochelys but lacks the characterized ornamentation patterns observes in these species, and in the first neural in an arrow shape. To evaluate the nuchal morphology of the taxa from the Neuquen Basin a morphometrics analysis was performed evaluating the long vs width index, which recovered Prochelidella nuchal in an index between 0.68 and 0.75. The nuchal index of MPCA PV 1127 is 0.77 similar to the index observed in Prochelidella buitreraensis, meanwhile, the nuchal index of MPCA PV 1126 is 0.58 out of the range of Prochelidella species. These records here presents extend geographically to the turtle remains recovered from LBPA and allow us to discuss the diversity and relative size of pleurodiran turtles in the interval Albian-Turonian in Neuquén Basin.