Postcranial anomalies of Eocene freshwater pleurodiran and cryptodiran turtles from the Spanish Duero Basin.

Testudines are one of the best-represented taxonomic groups among the Paleogene taxa of the Duero Basin (Castile and Leon Autonomous Community, central Spain). Among them, Neochelys (Podocnemidide) and Allaeochelys (Carettochelyidae) are most abundant, allowing the population to be assessed for osteological anomalies. The abundance of postcranial remains of both taxa allows us to identify several individuals with potential anomalies, mostly in their shells. Some of them have already been described in previous studies, but most of them are still unpublished. The objective of this study is to analyze in detail the anomalous Neochelys and Allaeochelys remains. As a result, different categories of causal agents (such as bacteria, fungi, parasites, or trauma) have been identified as potential producers of the anomalies in these freshwater turtles. Information regarding the pathogenesis and healing stages of some of these anomalies is provided.

A new Crocodyloidea from the middle Eocene of Zamora (Duero Basin, Spain).

The eusuchian crocodyliforms recorded in the Eocene levels of the Spanish Duero Basin belong to three lineages: Planocraniidae, with the species Duerosuchus piscator; Alligatoroidea, represented by several specimens of the genus Diplocynodon; and Crocodyloidea, which includes several specimens traditionally attributed to Asiatosuchus. The genus Asiatosuchus, established in 1940 based on a middle Eocene species from Mongolia, has subsequently served as a wastebasket taxon for Paleogene remains belonging to several species, not only from Asia but also belonging to the European and North American records. Many of these species are known by highly fragmentary remains, sharing the presence of characters such as a flat and triangular skull, and long symphyses in the lower jaw, recognized as characteristic for the crocodyloids. In addition to isolated cranial remains, among the material traditionally attributed to Asiatosuchus at the Duero Basin stands out a nearly complete skull and a left mandible, from the middle Eocene area of Casaseca de Campeán (Zamora Province). The present study analyses in detail these specimens, previously reported during the 1980s, but analyzed in a very preliminary way. They are included for the first time in a phylogenetic analysis to establish the systematic position of this Spanish form. The results confirm that it corresponds to a new species of basal crocodyloid, defined here as Asiatosuchus oenotriensis sp. nov.

Shell characterization of the youngest valid species of the European Eocene genus Neochelys (Pleurodira, Podocnemididae): The Spanish Bartonian Neochelys salmanticensis.

The freshwater pleurodiran turtle Neochelys is the best-represented member of Podocnemididae in the European record, being known by eight Eocene species. The youngest of them is the Bartonian (middle Eocene) Neochelys salmanticensis, from the Duero Basin (Salamanca Province, Central Spain). It corresponds to the largest representative known for this genus, its shell reaching 50 cm in length. Despite this form was defined several decades ago, the information currently available on it is very limited, being restricted to shell remains of less than 10 individuals. In fact, this species lacks a valid diagnosis, considering the current knowledge about the genus. Numerous remains (i.e., more than 1,200) of the shell of this Spanish species are identified. Its detailed study is presented here, so that the anatomy of its shell is characterized in detail. In addition, several aspects related to its intraspecific variability are analyzed, relative to the individual, ontogenetic, and sexual variability. In this way, the shell of N. salmanticensis can be characterized with greater precision than that of any other species of the genus.