Abstract. Several British specimens of relatively complete and partial shells of small pleurosternid turtles, found in the Purbeck Limestone Group (Berriasian, Lower Cretaceous), are analysed in detail here. Despite having been found more than a century ago, most of them remained unpublished until now. Due to the scarce knowledge available to date about the small individuals of Pleurosternidae from the British record, their taxonomic status was doubtful. Thus, some authors proposed their attribution to a new but not defined taxon of small size, whereas others suggested that they could represent juvenile individuals of Pleurosternon bullockii, the adults of which were also found in the Purbeck Limestone Group but at different levels. Knowledge about the shell of the adult individuals of Pleurosternon bullockii has notably increased recently, abundant information on its intraspecific variability being currently available. In this context, a detailed study of the small specimens through qualitative and quantitative approaches is performed here. The results are evidence a significant range of shape variability because of ontogenetic development, as well as other types of intraspecific variation such as inter-individual variation. As a consequence, their attribution to juvenile individuals of Pleurosternon bullockii is justified, providing new data on the ontogenetic development of a basal form.

No abstract

No abstract

The uppermost Jurassic to lowermost Cretaceous stem turtle Pleurosternon bullockii is the pleurosternid (Testudinata, Paracryptodira) known by the largest number of specimens worldwide, composing the largest European collection of Lower Cretaceous complete and partial shells for a turtle taxon. The availability of numerous specimens as well as their generally good preservation allowed for recent detailed characterization of the shell of this species, including states that are variable at the intraspecific level (individual variability, sexual dimorphism, and ontogenetic development). However, extreme cases of morphological variation corresponding to anomalies have not been addressed in detail, neither for P. bullockii nor for any other member of Paracryptodira. In this context, the study of several shell anomalies in P. bullockii is carried out here. Fourteen specimens showing anomalies are recognized and examined here to determine the frequency and distribution of these shell anatomical deviations. All these anomalies are described and figured. The morphogenetic cause of each of them is discussed. As a consequence, a relatively broad spectrum of anomalies is reported for P. bullockii. None of the anomalies seem to present negative consequences for vital activities of the specimens since none compromised the main functions of the shell.

The study of pathological bone modifications of extinct organisms of lineages, which are still living today, in combination with extant representatives, allows to infer data about population dynamics, lifestyle, and diseases they were subject to. Pathological studies in turtles are extensive; however, these contributions are mainly focused on extant representative records of survival rates or on non‐skeletonized material, and do not generally include morphological descriptions, illustrations, or data concerning their etiology and pathogenesis. As a consequence, paleopathology in turtles remains relatively poorly understood, especially considering extinct forms. In this context, we herein analyze marks of possible pathological origin recognized in two disarticulated plastral plates of the Spanish freshwater basal pan‐pleurodiran turtle Dortoka vasconica (Dortokidae), from its type locality, the Upper Cretaceous (late Campanian‐early Maastrichtian) fossil site of Laño 1 (Treviño County, Burgos, Spain). As a result, information regarding the possible etiology, pathogenesis, and stages of healing of the marks studied here are provided. A probable infectious origin is recognized as the etiology in both plates, these marks being considered as pathologies. This study contributes to our understanding of pathologies in extinct turtle taxa, specifically a stem‐pleurodiran turtle.