Search

Despite nearly two centuries of intensive research of dicynodont diversity and distribution, the progress of the last two decades makes the early 21st century a dicynodont renaissance. Here we introduce Woznikella triradiata n. gen., n. sp., a Late Triassic European kannemeyeriiform with stahleckeriid affinities that may represent an early diverging lineage of that family, preceding its split into Placeriinae King, 1988 and Stahleckeriinae Lehman, 1961. Woznikella triradiata n. gen., n. sp. is distinguished from other dicynodonts by its autapomorphic, slender scapula with distinctly expanded dorsal and ventral parts, acromion directed anterodorsally, and inconspicuous scapular spine. Furthermore, we review reported global occurrences of Triassic dicynodonts, including fragmentary, indeterminate finds that may capture cryptic diversity, and analyze the biogeography of the Permian and Triassic Dicynodontia. According to our results, the region of southeastern Africa (Malawi, Mozambique, Namibia, South Africa, Tanzania, Zambia) throughout the Permian and Triassic served as a hotspot of dicynodont diversity and origin point for lineages migrating north and west. Multiple taxa independently migrated to the Americas and Eurasia, indicating open passages between the regions of Southern and Northern Hemisphere. Southern migrations from the Northern Hemisphere appear to be very rare, however.

Shell suture obliteration (ankylosis) was exceptionally frequent in the earliest turtles, in contrast to post-Triassic taxa. Since modern turtles grow mostly along sutures, early ankylosis in Triassic taxa is intriguing. The Triassic turtle Proterochersis porebensis Szczygielski& Sulej, 2016 is known from numerous specimens, allowing observation of shell microstructure changes during ontogeny. Shell ankylosis occurred seemingly randomly in individuals of variable size, including small and morphologically juvenile, and completely obscured the initial bony composition. We propose that this phenomenon in the Triassic turtles can be an effect of early evolutionary stages of shell histogenesis and physiological mechanisms still used in shell regeneration in modern species. We also describe some parallels between the unusual peripheral microstructure of another Triassic turtle, Waluchelys cavitesta Sterli, Martínez, Cerda & Apaldetti, 2020, and Proterochersis porebensis. Microstructural changes imply that Proterochersis porebensis could change habitat during ontogeny, small individuals appearing more aquatic and larger more terrestrial.

Marine reptiles from the Upper Jurassic of Central Europe are rare and often fragmentary, which hinders their precise taxonomic identification and their placement in a palaeobiogeographic context. Recent fieldwork in the Kimmeridgian of Krzyżanowice, Poland, a locality known from turtle remains originally discovered in the 1960s, has reportedly provided additional fossils thought to indicate the presence of a more diverse marine reptile assemblage, including giant pliosaurids, plesiosauroids, and thalattosuchians. Based on its taxonomic composition, the marine tetrapod fauna from Krzyżanowice was argued to represent part of the “Matyja-Wierzbowski Line”—a newly proposed palaeobiogeographic belt comprising faunal components transitional between those of the Boreal and Mediterranean marine provinces. Here, we provide a detailed re-description of the marine reptile material from Krzyżanowice and reassess its taxonomy. The turtle remains are proposed to represent a “plesiochelyid” thalassochelydian (Craspedochelys? sp.) and the plesiosauroid vertebral centrum likely belongs to a cryptoclidid. However, qualitative assessment and quantitative analysis of the jaws originally referred to the colossal pliosaurid Pliosaurus clearly demonstrate a metriorhynchid thalattosuchian affinity. Furthermore, these metriorhynchid jaws were likely found at a different, currently indeterminate, locality. A tooth crown previously identified as belonging to the thalattosuchian Machimosaurus is here considered to represent an indeterminate vertebrate. The revised taxonomy of the marine reptiles from Krzyżanowice, as well as the uncertain provenance of the metriorhynchid specimen reported from the locality, cast doubt on the palaeobiogeographic significance of the assemblage.

Bromalites (coprolites and possibly some cololites) from a turtle-dominated fossil assemblage from the Upper Triassic of Poland were studied. Bromalites collected at the Poreba site are grouped within four morphotypes (A, B, C, and D) attributable to sharks, medium-sized omnivorous or carnivorous tetrapods (likely turtles), sizable carnivorous archosaurs (likely theropods) and an indeterminate big herbivorous tetrapod (possibly dicynodonts or aetosaurs), respectively. Food residues, abundant eggs (possibly of parasites), and microorganisms were found within the materials. Several lines of evidence suggest that at least part of the type B specimens might have been produced by turtles, since (a) turtles are the prevailing tetrapods in the assemblage (over 4/5 of tetrapod bone remains), (b) coprolites are of adequate size, and (c) they appear to have been produced by a carnivore of a low metabolic rate, as seen in extant turtles. The content of the type B specimens would imply that the Late Triassic turtle Proterochersis porebensis was partly piscivorous, but possibly complemented its diet with a more diversified foodstuff, including plants. Semiaquatic habit of Proterochersis porebensis might also provide a taphonomic explanation of the relative abundance of turtle remains at the Poreba site, Poland. Shark bromalites and coprolite specimens attributable likely to theropod dinosaurs also contain abundant fish remains. Origin and classification of spiral and scroll bromalites left by fish are discussed in addition.

Since 1990, several localities within the Keuper (upper Middle to Upper Triassic) strata in southern Poland have yielded remains of numerous terrestrial vertebrate species. Here we report a new Upp...

Although Western Europe has yielded numerous Jurassic turtle taxa, several represented by cranial material or complete skeletons, the fossil record of the Jurassic turtles remains scarce to the north and east from Germany. Although some Late Jurassic testudinates were historically described from Poland, they were, thus far, represented by fragmentary remains that never were properly figured or described in detail. Therefore, very little is known about the mid-Mesozoic diversity of turtles in that region of the continent. A new pancryptodiran turtle genus and species, Owadowia borsukbialynickae, is described from the uppermost Jurassic (Tithonian, ca. 148 Ma) carbonate sediments of the Kcynia Formation in Owadow-Brzezinki Quarry, near Tomaszow Mazowiecki in central Poland. The lower jaw morphology and palaeoecological setting inhabited by the new genus and species, together with the trophic relationships of the Jurassic pancryptodiran turtles, are discussed in an attempt to determine the potential range of mode of life of O. borsukbialynickae. We propose that the new specimen belongs to a new durophagous pancryptodiran turtle taxon. O. borsukbialynickae might have spent considerable time in the marine environment and specialized on eating hard-shelled invertebrates like bivalves and decapod crustaceans, common to that setting.

BackgroundTurtle shells tend to exhibit frequent and substantial variability, both in bone and scute layout. Aside from secondary changes, caused by diseases, parasites, and trauma, this variability appears to be inherent and result from stochastic or externally induced flaws of developmental programs. It is, thus, expected to be present in fossil turtle species at least as prominently, as in modern populations. Descriptions of variability and ontogeny are, however, rare for fossil turtles, mainly due to rarity, incompleteness, damage, and post-mortem deformation of their remains. This paper is an attempt at description and interpretation of external shell variability in representatives of the oldest true turtles,Proterochersis robustaandProterochersis porebensis(Proterochersidae, the sister group to all other known testudinatans) from the Late Triassic (Norian) of Germany and Poland.MethodsAll the available shell remains ofProterochersis robusta(13 specimens) andProterochersis porebensis(275 specimens) were studied morphologically in order to identify any ontogenetic changes, intraspecific variability, sexual dimorphism, and shell abnormalities. To test the inferred sexual dimorphism, shape analyses were performed for two regions (gular and anal) of the plastron.ResultsProterochersisspp. exhibits large shell variability, and at least some of the observed changes seem to be correlated with ontogeny (growth of gulars, extragulars, caudals, and marginals, disappearance of middorsal keel on the carapace). Several specimens show abnormal layout of scute sulci, several others unusual morphologies of vertebral scute areas, one has an additional pair of plastral scutes, and one extraordinarily pronounced, likely pathological, growth rings on the carapace. Both species are represented in a wide spectrum of sizes, from hatchlings to old, mature individuals. The largest fragmentary specimens ofProterochersis porebensisallow estimation of its maximal carapace length at approximately 80 cm, whileProterochersis robustaappears to have reached lower maximal sizes.DiscussionThis is the second contribution describing variability among numerous specimens of Triassic turtles, and the first to show evidence of unambiguous shell abnormalities. Presented data supplement the sparse knowledge of shell scute development in the earliest turtles and suggest that at least some aspects of the developmental programs governing scute development were already similar in the Late Triassic to these of modern forms.

The presence of a pathology in the vertebral column of the early Permian mesosaurid specimen ZPAL R VII/1, being one of the oldest amniotic occurrences of congenital scoliosis caused by a hemivertebra, was recently recognized. Here we provide CT data to further characterize the phenomenon. The affected hemivertebra is wedged (incarcerated) between the preceding and succeeding vertebrae. The neural canal is misshapen but continuous and the number of dorsal ribs on each side of the specimen corresponds with the number of the vertebrae, documenting its congenital (homeobox-related) derivation.

This research was supported by the National Science Center (Narodowe Centrum Nauki, www.ncn.gov.pl), Poland, project no. 2011/ 01/N/ST10/06989 granted to D. Surmik. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. There was no additional external funding received for this study., We report the first occurrence of congenital scoliosis in an early Permian aquatic parareptile, Stereosternum tumidum from Paraná state, Brazil. The spine malformation is caused by a congenital hemivertebra. These observations give insight into the biomechanical aspects of underwater locomotion in an axial skeleton-compromised aquatic amniote. This is the oldest record of a hemivertebra in an aquatic animal., National Science Center (Narodowe Centrum Nauki, www.ncn.gov.pl)