The Middle Miocene brachiopod fauna of the Mecsek Hills (Southern Hungary) is poorly known. In this paper the brachiopods of a new fossil site discovered by private collectors on the outskirts of Mecsekpölöske village is described. The studied assemblage from the lower Badenian clayey sand (Lajta Limestone Formation) is very abundant (5248 specimens), and represented partly by some species well-known from other shallow marine sites of the Central Paratethys (Joania cordata, Megathiris detruncata, Gryphus miocenicus, Megerlia truncata, and Discradisca sp.). However, the most abundant taxon is a new species of Bronnothyris (i.e., B. attilavorosi sp. nov.), characterised by subcircular outline; four to seven single, weak, rounded ribs; distinct cardinal process; strongly prominent triangular dorsal median septum, with septal flanges and four strong serrations on its anterior slope; short, slightly divergent inner socket ridges; narrow fused hinge plates. This is the first record of Bronnothyris from the Central Paratethys and from the Miocene. The Hungarian species extends the stratigraphic range of Bronnothyris: it is known from the Upper Cretaceous to the Middle Miocene. The taxonomic composition of the Mecsekpölöske brachiopod assemblage (with strong dominance of Megathyrididae), together with several elements of the associated fauna (e.g., gastropods, foraminifers, ostracods, otoliths, and fish teeth), suggests that the palaeoenvironment may have been a shallow marine seafloor covered with seagrass meadows. Both the recently published upper Pliocene brachiopod assemblage from Italy (Villalvernia, Piedmont) and this Middle Miocene assemblage presented here from Hungary confirm that micromorphic Megathyrididae brachiopods can be used as indirect palaeo-seagrass indicators (IPSIs). However, since they do not occur exclusively in this environment, other direct or indirect evidence of the former presence of seagrass meadows is also necessary.
Proterochampsidae is a clade of carnivorous archosauriforms that lived during the Triassic and is characterized by
an elongated rostrum with dorsally oriented external nares, and a unique pes configuration. Although the majority of
proterochampsids are found in South America, recent phylogenetic studies suggest a broader geographical distribution
for this clade. Most proterochampsids are known from cranial remains; if postcranial elements are known they are fre
quently poorly preserved. This study describes a new proterochampsid, Retymaijychampsa beckerorum gen. et sp. nov.,
from the Middle–Late Triassic, based on an almost complete and articulated hindlimb. The holotype was excavated at
the Linha Várzea 2 (Becker) Site, located in the municipality of Paraíso do Sul, Rio Grande do Sul, Brazil. The fossils
from this locality places it within the Dinodontosaurus Assemblage Zone, which is Ladinian to early Carnian in age
according to biostratigraphic investigations. The new taxon is the second proterochampsid described from the Pinheiros
Chiniquá Sequence and represents one of the oldest known members of the clade worldwide. An interesting aspect of
R. beckerorum gen. et sp. nov. is its phylogenetic position because it is more closely related to Proterochampsa than
to rhadinosuchine proterochampsids. Therefore, the discovery of the new proterochampsid partially fills a long ghost
lineage extending from the Middle Triassic to the early Late Triassic. Furthermore, the presence of two proterochamp
sid species within the Pinheiros-Chiniquá Sequence deposits supports the hypothesis of significant ecomorphological
diversity among proterochampsians in Triassic environments.
Yann Rollot, Mohamed K. AbdelGawad, Mohamed A. Hamdan
et al.
Abstract Although trionychians have a rich fossil record, much of their fossil diversity is known from the Cretaceous and Paleogene, and little is known about their evolutionary history in the Neogene. We here describe cranial and shell material of trionychians from the Early Miocene Moghra Formation of Egypt that we attribute to a new carettochelyid taxon, Allaeochelys meylani sp. nov., and to the Trionyx lineage. Allaeochelys meylani sp. nov. fills a temporal gap between previously described taxa and exhibits a series of unique features, including greatly thickened cranial bones, a broad bony wall posterior to the orbit, a large fossa formed by the maxilla and premaxilla at the anterior third of the triturating surface, and a medial process on peripheral II. Allaeochelys meylani sp. nov. also documents the oldest occurrence of Carettochelyidae on the Afro-Arabian continent, while the Trionyx material reported herein provides unambiguous evidence for the presence of this lineage on the Afro-Arabian continent no later than the Early Miocene.
Abstract The diversity of the fauna of the late Permian K6 Formation of the Metangula graben of northern Mozambique is coming to light thanks to recent discoveries made by the PaleoMoz Project. Here we describe the first diagnosable gorgonopsian remains from the K6a2 Member of the Metangula graben, specimen PPM2018-7Z. This specimen is a large-bodied gorgonopsian, and shows several features similar to the latest late Permian species Inostrancevia africana. PPM2018-7Z shares various autapomorphies with Inostrancevia africana including the extremely narrowed jugal ventral to the orbit, the pineal foramen being positioned far posteriorly, the anteroposteriorly expanded ventral portion of postorbital bar, the orbit being larger than the temporal fenestra and by having prefrontal rugosities and foramina. The tooth morphology of Inostrancevia africana is here accessed based on the left canine of PPM2018-7Z, which is characterised by low labial ridges, a short mesial carina and thick basal denticles of the mesial carina. PPM2018-7Z is phylogenetically recovered close to Inostrancevia africana within the “Russian clade gorgonopsians”. PPM2018-7Z and Inostrancevia africana do not possess an interorbital ridge that is present in some rubidgeines such as Clelandina and Dinogorgon. Furthermore, PPM2018-7Z and inostranceviines retain a postfrontal with a posterior process that extends posteriorly invading the parietal border, unlike in rubidgeines in which the posterior process of the postfrontal is absent. The presence of Inostrancevia africana in the K6a2 Member of the Metangula graben helps correlating this member to the Daptocephalus Assemblage Zone in the Karoo Basin of South Africa.
Lizards play vital roles in extant ecosystems. However, their roles in extinct ecosystems are poorly understood because the fossil record of lizards consists mostly of isolated bones. This makes it difficult to document changes in lizard morphology and body size over time, which is essential for studies of lizard paleoecology and evolution. It is also difficult to compare available fossil lizard data with existing sources of extant lizard data because extant studies rarely measure individual bones. Furthermore, no previous study has regressed measurements of individual bones to body length across crown lizard groups, nor tested those regressions on fossil skeletons. An extensive dataset of individual bone measurements from extant lizards across crown taxonomic groups is here employed to develop novel methods for estimating lizard body size from isolated fossil elements. These methods were applied to a comparably large dataset of fossil lizard specimens from the robust Paleogene record (66–23 Ma) of the Western Interior of North America. This study tests the hypothesis that anatomical proportions have been conserved within higher-level crown lizard groups since the Paleogene and can therefore be used to reconstruct snout-vent length (SVL) and mass for fossil specimens referred to the same groups. Individual bones demonstrated strong correlation with SVL in extant as well as fossil lizard specimens (R2 ≥ 0.69). Equations for mass estimation from individual bones were derived from the SVL regressions using published equations for calculating lizard body mass from SVL. The resulting body size estimates from regression equations for the entire fossil dataset revealed that lizards reached greatest maximum body size in the middle Paleogene, with the largest size class dominated by anguid lizards that exceeded 1 meter in SVL and 1.5 kg in body mass. Maximum body size decreased to under 400 mm and below 1.5 kg in the late Paleogene. No association was found between changes in maximum lizard body size and marine isotope proxies of global temperature through the Paleogene. This is the first study to investigate body size evolution across lizard clades over a deep time interval and for a large geographic region. The proposed methods can be used to generate body size regressions and provide estimates of body size for isolated lizard bones referred to any crown group.
The continental Lower Triassic (Middle Buntsandstein) siliciclastic deposits exposed along the margins of the Holy
Cross Mountains, Poland, yield locally abundant vertebrate footprints and bones. Although the footprints have been
described in a number of studies, providing, for example, new insights into the origin of dinosaurs, there are few studies
focusing on the bones. Here, we describe new amphibian and reptile material from the Buntsandstein fluvial sandstones
of early Olenekian age exposed at Stryczowice on the north-eastern margin of the Holy Cross Mountains. These finds
include fragmentary cranial specimens referred to as Trematosauridae gen. et sp. indet. and Procolophonidae gen. et
sp. indet. Faunal differences between Stryczowice and the best-known Polish Olenekian vertebrate-bearing site of
Czatkowice 1 near Kraków support heterogeneity in the Early Triassic vertebrate distribution across Pangea.
Stefano Dominici, Maurizio Forli, Mauro M. Brunetti
et al.
AbstractHaliotis Linnaeus, 1758, a commercially important gastropod, is the only known genus in the family Haliotidae (Mollusca, Vetigastropoda, or abalone) worldwide. Its poor Cenozoic record and high intraspecific variability resulted in different interpretations of nomenclature, impeding a robust species-level taxonomy and biogeographic history. Among the best-studied forms, three subspecies of H. tuberculata Linnaeus, 1758 currently inhabit the temperate waters of the Mediterranean and the eastern Atlantic. New findings in the Pliocene of Tuscany (Italy) are presented here, and the taxonomy of the European record is revised. On the basis of a multivariate analysis of shell morphometrics for the first time applied to the study of fossil abalones, and consistent with the chronostratigraphic and geographic framework, H. plioetrusca n. sp. is introduced and H. volhynica Eichwald, 1829 and H. lamellosoides Sacco, 1897 are reinstated as valid species. Some recently described forms from the Pliocene of Spain are placed in synonymy with H. lamellosoides. Haliotis ovata Michelotti, 1847 is proposed as the ancestral taxon of modern H. tuberculata, via H. lamellosoides. This lineage diversified in the subtropical/warm temperate Pliocene Mediterranean, represented by H. lamellosoides, H. bertinii Forli et al., 2003 and H. plioetrusca. The progressive global cooling starting at around 3.0 Ma is associated with the appearance of H. tuberculata at temperate latitudes. H. plioetrusca is not known from younger strata, whereas H. bertinii survived into the Calabrian.UUID: http://zoobank.org/7c2f2258-2574-4976-a2f5-804c54c86679
Claudia P. Tambussi, Federico Javier Degrange, Ricardo Santiago de Mendoza
“The present state of knowledge of the Cenozoic birds of Argentina” published in Contributions in Sciences in 1980, written by the argentine paleontologist Eduardo Pedro Tonni, became a must-read for those interested in the record of fossil birds. In that work, all the records known up to that time are compiled and some comments are made. Since then, there have been crucial advances in unraveling the diversity of Cenozoic birds in Argentina. Based on that work, here is a detailed updated and annotated list of all known avian records in Argentina that includes representatives of Palaeognathae (Tinamiformes and Rheiformes), Galloanseres (Anseriformes) and Neoaves (Sphenisciformes, Suliformes, Charadriiformes, Phoenicopteriformes, “Ciconiiformes”, “Gruiformes”, Pelecaniformes, Coraciimorphae, Cathartiformes, Accipitriformes, Falconiformes, Cariamiformes and Passeriformes). Besides, a substantial contribution is that here are photographs of the holotypes of all the new species that were nominated after Tonni's work and a table that compiles the main bibliographic information referring to the systematic history of each taxon.
Cecilia Andrea Benavente, Juan I. Balaguer-Gasull, Paula Guillermina Giordano
et al.
The La Cantera Formation (Aptian) represents an underfilled lake system developed in an extensional basin during the Cretaceous hothouse and it bears an abundant and diverse fossil record. Our goal was to investigate paleoclimate conditions of the unit from a multiproxy approach. We analyzed two proxies: a) the stable isotope (carbon and oxygen) composition of basal Actinopterygii and Neopterygii fish remains and from indeterminate plant remains; and b) the clay mineral assemblage composition; providing two independent lines of evidence to reconstruct paleoclimate conditions including paleotemperature calculations for lake waters. The values obtained for fish remains for δ13C range between -8.4 and -1.3 ‰ (δ13C= χ -5.57‰; σ ± 2.25); and δ18O values that vary between -5.7 and -3.6‰ (δ18O= χ -4.33‰; σ ± 0.84); in the case of plant remains δ13C values range between -25.8 and -22.8‰ (δ13C= χ -25‰ -4.33). Paleotemperatures obtained from δ18O for the water column ranged between 23.33 to 35.80 °C. Plant δ13C signature allowed obtaining a δ13CCO2 composition of -5 ‰. This agrees with the interpretation of the La Cantera originating from sediment deposition in an underfilled lake basin and with the global climate context of the Cretaceous. The clay mineral assemblage is dominated by illite-smectite indicating enhanced hydrolysis and seasonal rainfall supporting temporal warmup of the lake. Our data supports aridity conditions during the La Cantera paleolake existence. These findings suggest that geochemical proxies of paleontological datasets are accurate for paleoclimate reconstructions for the deep time records of the La Cantera lacustrine system.
Jorge Campos-Medina, Martín Chávez-Hoffmeister, Pablo Oyanadel-Urbina
et al.
El presente artículo tiene como objetivo dar a conocer un caso de estudio donde se aplicaron metodologías para la excavación de restos de vertebrados fósiles en áreas acotadas, en el marco del proceso de monitoreo ambiental en Chile. Este caso resulta de particular interés debido a que se realizó bajo condiciones de alta humedad, durante un periodo de aproximadamente un mes en el que se procesaron ocho toneladas de sedimento. La metodología aplicada consistió en la excavación manual de niveles fosilíferos a través de desmonte lateral de planos horizontales con cuadrículas, desde los niveles superiores hasta la base del estrato portador, con recuperación de fósiles por medio de excavación de planta y bochón seco. Adicionalmente se aplicó la metodología estándar, de acuerdo con el organismo estatal, para la recuperación de microvertebrados mediante lavado y tamizado. Todo el proceso de rescate permitió la extracción de 82 piezas de las cuales el 76% fueron recuperadas in situ, mientras que el 24% fue recuperada por la metodología estándar. En base en lo anterior, se ofrecen recomendaciones para mejorar las propuestas metodológicas para rescate y monitoreo ambiental, ofreciendo una base comparativa para evaluar la efectividad de las técnicas empleadas en futuras labores de rescate.
Feiko Miedema, Gabriele Bindellini, Cristiano Dal Sasso
et al.
Abstract Relatively complete ontogenetic series are comparatively rare in the vertebrate fossil record. This can create biases in our understanding of morphology and evolution, since immaturity can represent a source of unrecognized intraspecific variation in both skeletal anatomy and ecology. In the extinct marine reptile clade Ichthyopterygia, ontogenetic series were widely studied only in some Jurassic genera, while the ontogeny of the oldest and most basal members of the clade is very poorly understood. Here, we investigate cranial ontogeny in Mixosaurus cornalianus, from the Middle Triassic Besano Formation of the Swiss and Italian Alps. This small-bodied taxon is represented by a wealth of material from multiple size classes, including fetal material. This allows us to assess ontogenetic changes in cranial morphology, and identify stages in the ontogenetic trajectory where divergence with more derived ichthyosaurs has occurred. Early ontogenetic stages of Mixosaurus show developmental patterns that are reminiscent of the presumed ancestral (early diverging sauropsid) condition. This is prominently visible in the late fetal stage in both the basioccipital, which shows morphology akin to basal tubera, and in the postorbital, which has a triradiate head. The ontogenetic trajectory of at least some of the cranial elements of Mixosaurus is therefore likely still very akin to the ancestral condition, even though the adult cranium diverges from the standard diapsid morphology.
AbstractBorophagusis the terminal genus of the highly diverse and successful subfamily, Borophaginae. Skeletal remains of this bone-crushing canid are most commonly found in transitional or grassland environments across North America between Late Miocene–Middle Pleistocene, but are rare or absent in forested habitats. Here, we describe a humerus from the Gray Fossil Site of Tennessee, which is the first occurrence of this genus in a heavily forested ecosystem. The distinct limb proportions ofBorophagussuggest the genus may have been well suited for a closed habitat like the Gray Fossil Site, contrary to where a majority of their fossils have been previously found. This discovery documents the first pre-Pleistocene occurrence of a canid in the Appalachian region of the eastern United States.
Darja Dankina, Andrej Spiridonov, Paweł Raczyński
et al.
The late Permian time was a transformative period before the most severe mass extinction known. Even though fishes constitute a key component of marine ecosystems since the Silurian, their biogeographic patterns during the late Permian are currently insufficiently known. The new ichthyofaunal material described here comes from the southeastern part of the Zechstein Basin, from the calcareous storm sediments alternating with marls, which were deposited in less energetic conditions. Chondrichthyans and osteichthyans are reported here for the first time from the Nowy Kościół quarry in the SW Poland. The assemblage consists of various euselachian dermal denticles, actinopterygian scales and teeth, and isolated hybodontoid tooth putatively assigned as extremely rare ?Gansuselache sp. from the Permian. The diverse actinopterygian tooth shapes show significant ecological differentiation of fishes exploring sclerophagous, durophagous, and herbivory modes of feeding in the given part of the Zechstein Basin suggesting the presence of complex ecosystems even in hyper-saline conditions of an epicontinental sea.
Josh Jenkins Shaw, Alexey Solodovnikov, Ming Bai
et al.
AbstractThe first fossil rove beetle (Coleoptera, Staphylinidae) from New Zealand is described from the earliest Miocene Foulden Maar fossil-Lagerstätte, Otago. The new species,Sphingoquedius meton. sp., is attributable to the tribe Amblyopinini of the subfamily Staphylininae based on the scutellum with anterior scutellar ridge only; isodiametric microsculpture on the pronotum; multidirectional arranged setae on the elytra; and presence of radiating setae on the fourth abdominal tergite.Sphingoquedius meton. sp. is the first Southern Hemisphere fossil record of Amblyopinini and its affinity to the extant fauna as well as biogeographic and paleocological implications are discussed.UUID:http://zoobank.org/52275b83-d5ff-48af-A66F-2d62c3461677
Adriana Mónica Blasi, Carola Castiñeira Latorre, Diego Francisco Block
et al.
In order to contribute to the knowledge of the paleoenvironmental and paleoclimate evolution that occurred from the Late Pleistocene to the Late Holocene in the Pampa Ondulada, northeast of the Province of Buenos Aires, the results obtained by interdisciplinary research carried out in the Salto-Arrecifes fluvial basin are presented. These results were integrated and correlated with those published by some authors of this work referring to the geological and paleoecological characteristics that dominated the valleys of this sector of the Argentina Pampas region since the Late Pleistocene. The age of the sedimentary successions was obtained by radiocarbonic dates in 10 locations of the Salto-Arrecifes fluvial basin. Regional correlations with the units described for the Luján and Areco river basins were carried out. Those characterize the sedimentary processes that occur in the current valleys, of the lower-middle basins of these courses. The various sedimentary facies present in the continental sectors and in the sections closest to the river’s mouth are discriminated. The Late Pleistocene–Holocene sedimentation, which occurred in the middle Salto-Arrecifes, Luján and Areco basin, shows the incidence of climatic changes during the period. As for the facies recognized in the sections near the river’s mouth of the courses, the incidence of eustatic changes produced during the current interglacial were added. Exposure in the ravine of deposits that have the oldest recorded ages and that occurs only in some stretches along the current valley could indicate that neotectonics has been another extrinsic factor acting in the basins at some point in the Late Holocene.
Yael Leshno Afriat, Yael Edelman-Furstenberg, Rivka Rabinovich
et al.
Accurate identification of fossils forms the foundation for many aspects of geological research, including biostratigraphy and paleoecology. Yet, many taxa are identified qualitatively based on their morphology, which requires extensive expertise in specific taxonomic groups. The often-subjective identification of specimens is difficult to verify and can cause misinterpretation and inaccuracies. Thus, finding new ways to objectively identify fossils will be of great value. A prime example of the ‘taxonomic impediment’ in the fossil record is exhibited in the Nerineoidea, a group of extinct gastropods that form a major component of Mesozoic shallow marine environments. Taxonomically diverse and numerically abundant assemblages of Nerineoidea are found across a wide range of paleo-latitudes, and used for biostratigraphy and paleoecology. The group is distinctly recognized by the presence of internal spiral folds that developed inside the internal cavity of the shell during ontogeny. The number and position of folds is constant within a species, and form the basis of their classification. Their paleoecological and biostratigraphical importance is represented by vast scientific literature and abundant fossil collections worldwide. However, identification and uniform classification of this group is lacking due to two major factors: inconsistent systematic position and subdivision, and the classification procedure is largely based on polished cross-sections of specimens that reveal the important internal structure and destroy whole specimens, thus preventing any further verification. Therefore, identification of specimens is largely based on expert judgment and difficult to replicate. inconsistent systematic position and subdivision, and the classification procedure is largely based on polished cross-sections of specimens that reveal the important internal structure and destroy whole specimens, thus preventing any further verification. Therefore, identification of specimens is largely based on expert judgment and difficult to replicate. Micro-computed tomography (micro-CT) is revolutionizing species identification by modeling the internal anatomy of fossils in 3D, and allowing the study of structures that would previously have been impossible to visualize. We present the first automated taxonomic identification method of Nerineoidea fossils, by combining modern non-destructive imaging techniques with classic identification methods. Fifty-eight Jurassic Nerineoidea specimens were examined from Europe, Arabia, and Africa. Images of polished cross-sections of specimens were compiled from online databases, literature, and fossil collections. Three successive longitudinal whorl cross-sections showing the internal folds were analyzed for each specimen. The shape of each whorl was captured using thirty evenly spaced semi-landmarks. In addition, twenty eight specimens from the Geological Survey of Israel and the Natural History Museum (UK) were scanned using micro-CT. Optimal longitudinal slices were selected from the 3D reconstructions for each specimen using Amira (v. 6.3), and their whorl outlines were captured as described above. Canonical variate analysis shows that whorl outlines significantly differentiate between Nerineoidea, independent of the data source or the location of the whorl in the spire. The Jackknife estimate of future identification is high (73.25%), and suggests that the method can be applied to accurately assign the taxonomic family of future specimens reliably and effectively. Moreover, the high variation in whorl outlines between genera can be used to identify specimens to the species level with a high level of certainty. We demonstrate that shape analysis of the whorl outlines is an objective and quantitative method for identifying different taxa of Nerineoidea. The advantages of the method include its application to mass accumulation of specimens, as well as to two-dimensional images from various sources. This will enable future quantitative study of polished cross-sections of specimens from museum collections, scientific publications and online databases. The quantitative and objective taxonomic identification of Nerineoidea fossils could revolutionize their classification and improve the paleoecological reconstruction of Mesozoic carbonate platforms. This will enhance interpretations of faunal biogeographic response to changing environmental conditions along shelf ecosystems.
Tiane Macedo De Oliveira, Daniel Oliveira, Cesar L. Schultz
et al.
Tanystropheidae is a clade of early archosauromorphs with a reported distribution ranging from the Early to the Late Triassic of Asia, Europe, and North America. Although some specimens with possible tanystropheid affinities from the Lower Triassic beds of Brazil have been previously attributed to “Protorosauria”, little is known about the tanystropheid record in Gondwana. Here, two new and one previously reported specimen from the Sanga do Cabral Formation (Induan–Olenekian) of Brazil are described and interpreted as ?Tanystropheidae. These records, together with other tetrapods previously reported for the Sanga do Cabral Formation, increase the knowledge of the biotic diversification during the beginning of the Triassic. This contribution reinforces that the archosauromorph diversification occurred shortly after the Permo-Triassic extinction, making the Sanga do Cabral Formation an important unit for the study of early Mesozoic faunas.
José I. Canudo, José L. Carballido, Alberto Garrido
et al.
Rebbachisaurids are a group of basal diplodocimorph sauropods that diversified in Gondwana at the end of the Early Cretaceous and the beginning of the Late Cretaceous. It is a group of great palaeobiogeographical interest, for it clearly illustrates various processes of dispersal throughout Gondwana and to Laurasia prior to the breakup of Africa and South America. However, the relationships within the group are still under discussion owing to the scarcity of cranial material that would help clarify them. In the present paper we describe the new rebbachisaurid Lavocatisaurus agrioensis gen. et sp. nov. from the Aptian–Albian (Lower Cretaceous) of Neuquén (Argentina). Remains have been recovered belonging to an adult specimen (holotype) and two immature specimens (paratypes). Taken together, almost all the bones of the taxon are represented, including most of the cranium. Lavocatisaurus agrioensis gen. et sp. nov. is the first rebbachisaurid from Argentina with an almost complete cranium, making it possible to recognize differences with respect to other rebbachisaurids, such as the highly derived Nigersaurus. Among its most notable characters are the presences of a large preantorbital fenestra and maxillary teeth that are significantly larger than those of the dentary. Our phylogenetic study places Lavocatisaurus amongst basal rebbachisaurids, as the sister lineage to Khebbashia (the clade formed by Limaysaurinae + Rebbachisaurinae). This position, which is somewhat more derived than that previously suggested for Comahuesaurus and Zapalasaurus (the Argentinean rebbachisaurids closest in geographical and geological terms), reaffirms the presence of different basal rebbachisaurid lineages in the Early Cretaceous of Patagonia.
Elsa Panciroli, Roger B.J. Benson, Richard J. Butler
We describe two partial dentaries of mammals from the Middle Jurassic of Scotland. They belong to the early cladotherian Palaeoxonodon ooliticus. These dentaries comprise the first specimen of P. ooliticus ever found—although its significance was initially unrecognised so it remained undescribed until now—and the most recently discovered specimen, found during fieldwork in 2017. The new specimen preserves part of the coronoid process of the dentary, previously unknown for P. ooliticus, demonstrating the presence of a deep masseteric fossa, with a prominent crest enclosing the fossa anteriorly, and a masseteric foramen, located in the masseteric fossa on the buccal surface of the dentary. On the lingual surface, the mandibular foramen is offset from the Meckel’s sulcus, and positioned below the alveolar plane. These morphologies allow an updated analysis of the phylogenetic position of P. ooliticus, confirming a sister-taxa relationship between Palaeoxonodon and Amphitherium. The position of the mandibular foramen, and the slight extension of the masseteric fossa into the body of the dentary are new autapomorphies for Palaeoxonodon.