Cranial Material Research Articles

Green lizards (Squamata, Lacertidae) from ?Pliocene deposits of Węże I in southern Poland, with comments on cranial features for selected lacertids

AbstractI here describe lacertids from the classic Węże I locality in southern Poland (?Pliocene deposits) based on six previously undescribed jaws: an incomplete left maxilla, two dentaries and three mandibles. These jaws collectively provide considerable data on the morphology of the maxilla, dentary, teeth, coronoid, splenial, angular, surangular and prearticular. All six jaws can be unequivocally allocated to Lacertidae and five of those are allocated to European green lizards of the Lacerta viridis group. Currently, La. viridis has regionally extinct or probably extinct status in Poland. The material from Węże I provides evidence that European green lizards had a large geographic distribution in Europe, including Poland during the ?Pliocene. One mandible fragment appears to be slightly different and is allocated to Lacertidae indet. That mandible might point to a higher taxonomic diversity of lacertids in this locality. However, that interpretation needs to be viewed with caution, because based on such limited material, individual and/or ontogenetic variation cannot be ruled out. To reveal the real taxonomic palaeodiversity of lacertids in Węże I, new and more complete cranial material is needed. In addition, this article provides insights into the comparative osteology of skulls and selected cranial elements in lacertids.

Fishes and squamate reptiles from the Pliocene sites of Berești and Mălușteni (eastern Romania) – A reassessment of old but poorly known material

This paper performs a revision of teleost fish and squamate reptile material from the Early Pliocene sites of Berești and Mălușteni (eastern Romania), found in old collections, but never described in detail. The fish assemblage includes a few cyprinid species (Rutilus robustus, Rutilus cf. R. frisii, Scardinius ponticus, Barbus sp., Tinca sp.), Silurus cf. S. soldatovi, pikes (Esox moldavicus and Esox sp.), as well as indeterminate remains of salmonid, percid and sparid fishes. Squamate reptiles are represented by isolated vertebral and cranial material assigned to the anguid lizard Pseudopus pannonicus, as well as by isolated snake vertebrae belonging to the viperid Macrovipera sp. This is the most taxonomically diverse Pliocene ectothermic vertebrate assemblage described so far from the Romanian Carpathian Foreland. The obtained results contribute to a better understanding of continental vertebrate fauna evolution in the eastern part of central Europe.

A juvenile bird with possible crown-group affinities from a dinosaur-rich Cretaceous ecosystem in North America

BackgroundLiving birds comprise the most speciose and anatomically diverse clade of flying vertebrates, but their poor early fossil record and the lack of resolution around the relationships of the major clades have greatly obscured extant avian origins.ResultsHere, I describe a Late Cretaceous bird from North America based on a fragmentary skeleton that includes cranial material and portions of the forelimb, hindlimb, and foot and is identified as a juvenile based on bone surface texture. Several features unite this specimen with crown Aves, but its juvenile status precludes the recognition of a distinct taxon. The North American provenance of the specimen supports a cosmopolitan distribution of early crown birds, clashes with the hypothesized southern hemisphere origins of living birds, and demonstrates that crown birds and their closest relatives coexisted with non-avian dinosaurs that independently converged on avian skeletal anatomy, such as the alvarezsaurids and dromaeosaurids.ConclusionsBy revealing the ecological and biogeographic context of Cretaceous birds within or near the crown clade, the Lance Formation specimen provides new insights into the contingent nature of crown avian survival through the Cretaceous-Paleogene mass extinction and the subsequent origins of living bird diversity.

Updated cranial and mandibular description of the Late Cretaceous (Maastrichtian) baenid turtle Saxochelys gilberti based on micro-computed tomography scans and new information on the holotype-shell association

Saxochelys gilberti is a baenid turtle from the Late Cretaceous Hell Creek Formation of the United States of America known from cranial, shell, and other postcranial material. Baenid turtles are taxonomically diverse and common fossil elements within Late Cretaceous through Eocene faunas. Detailed anatomical knowledge is critical to understanding the systematics and morphological evolution of the group. This is particularly important as baenids represent an important group of continental vertebrates that survived the mass extinction event associated with the Cretaceous/Paleogene boundary. High-resolution micro-computed tomography scanning of the holotype skull reveals additional anatomical details for the already well-known Saxochelys gilberti. This includes the revision of some anatomical statements from the original description, but also detailed knowledge on internal anatomical features of the braincase and the description of a well-preserved axis (cervical vertebra 2). Our new detailed description and previous work on the shell and postcrania make Saxochelys one of the best-described, nearly complete baenid turtles, which are often only known from either isolated shell or cranial material. A revised phylogenetic analysis confirms the position of Saxochelys gilberti as a derived baenid (Eubaeninae) more closely related to Baena arenosa than to Eubaena cephalica.

Cranial anatomy of Libognathus sheddi Small, 1997 (Parareptilia, Procolophonidae) from the Upper Triassic Dockum Group of West Texas, USA.

Libognathus sheddi, a leptopleuronine procolophonid from the Upper Triassic Cooper Canyon Formation, Dockum Group, West Texas, was based on an isolated left dentary and partial coronoid. New material referable to Libognathus sheddi, from the Cooper Canyon Formation, provides new information on the cranial anatomy. This new cranial material includes the antorbital portion of a skull, a left maxilla and premaxilla, quadratojugals, and dentaries, including intact tooth rows in the upper and lower jaws. Libognathus shows autapomorphies including; dentary deep with ventral margin oblique to tooth row immediately from the symphysis at ≥23°; anterior projecting coronoid contacting the lingual surface of the dentary underlying the last two dentary teeth; reduced contact between the lacrimal and the nasal; suborbital foramen formed by the maxilla and ectopterygoid, excluding the palatine; a posterior supralabial foramen shared by the maxilla and jugal; a Y-shaped antorbital pillar formed by the palatine, and massive orbitonasale and facial foramina (shared with unnamed southwest USA leptopleuronines). Phylogenetic analysis indicates that Libognathus is a highly derived leptopleuronine procolophonid, closely related to Hypsognathus fenneri and other southwest USA Revueltian leptopleuronines, which fall out as sister taxa to Hypsognathus, a relationship supported by a maxillary dentition restricted anterior to the orbital margin, a possibly synapomorphic orbitonasale septum in the form of an "antorbital pillar" created by the palatine, an anteroventral process of the jugal, and the presence of a small diastema between the first dentary tooth and the more posterior dentition. Libognathus exhibits a possible ankylosed protothecodont tooth implantation with frequent replacement, differing from some other proposed procolophonid implantation and replacement models. Chinle Formation and Dockum Group leptopleuronines are restricted to the Revueltian teilzone/holochronozone, making them possible Revueltian index taxa.

Temporal fenestration in a Procolophon trigoniceps specimen (Procolophonoidea) from the Lower Triassic of Brazil.

The parareptiles diversified widely during the Permian and persisted in Pangean ecosystems until the end of the Triassic. However, most parareptiles succumbed to the Permian-Triassic extinction, leading to the exclusive survival of procolophonoids. Procolophonoidea stands out as one of the most diverse parareptile clades, with about 40 species across Pangean land masses. The Early Triassic species Procolophon trigoniceps is known from South Africa, Antarctica, and Brazil. The majority of cranial materials of this procolophonoid are described as anapsid in temporal morphology, however, some skulls discovered in South Africa were found to exhibit temporal fenestration. Once thought to have systematic significance for the genus Procolophon, temporal fenestration was lately proposed to be an anomalous or pathological feature in P. trigoniceps. In this study, we describe new cranial material of P. trigoniceps from the Sanga do Cabral Formation of Brazil that clearly displays temporal fenestration. Aside from the fenestra, the specimen closely resembles more complete Brazilian P. trigoniceps skulls. The recurrent presence of the feature and the varying morphologies exhibited by the temporal fenestrae of P. trigoniceps may substantiate its characterization as an anomalous trait within the species. Furthermore, the occurrence of temporal fenestration in P. trigoniceps specimens from both South America and South Africa underscores parallels between these two Early Triassic ecosystems.

Osteology of the axial skeleton of Aucasaurus garridoi: phylogenetic and paleobiological inferences.

Aucasaurus garridoi is an abelisaurid theropod from the Anacleto Formation (lower Campanian, Upper Cretaceous) of Patagonia, Argentina. The holotype of Aucasaurus garridoi includes cranial material, axial elements, and almost complete fore- and hind limbs. Here we present a detailed description of the axial skeleton of this taxon, along with some paleobiological and phylogenetic inferences. The presacral elements are somewhat fragmentary, although these show features shared with other abelisaurids. The caudal series, to date the most complete among brachyrostran abelisaurids, shows several autapomorphic features including the presence of pneumatic recesses on the dorsal surface of the anterior caudal neural arches, a tubercle lateral to the prezygapophysis of mid caudal vertebrae, a marked protuberance on the lateral rim of the transverse process of the caudal vertebrae, and the presence of a small ligamentous scar near the anterior edge of the dorsal surface in the anteriormost caudal transverse process. The detailed study of the axial skeleton of Aucasaurus garridoi has also allowed us to identify characters that could be useful for future studies attempting to resolve the internal phylogenetic relationships of Abelisauridae. Computed tomography scans of some caudal vertebrae show pneumatic traits in neural arches and centra, and thus the first reported case for an abelisaurid taxon. Moreover, some osteological correlates of soft tissues present in Aucasaurus and other abelisaurids, especially derived brachyrostrans, underscore a previously proposed increase in axial rigidity within Abelisauridae.

A megaraptorid (Dinosauria: Theropoda) frontal from the upper Strzelecki Group (Lower Cretaceous) of Victoria, Australia

Cretaceous (non-avian) theropod dinosaurs from Australia are poorly understood, primarily because almost all specimens described thus far comprise isolated postcranial elements. In Australia, only three non-dental cranial elements pertaining to Theropoda have been reported: the left and right dentaries of Australovenator wintonensis from the Winton Formation (Cenomanian–lowermost Turonian) of Queensland, and an isolated surangular from the Eumeralla Formation (lower Albian) of Victoria. Herein, we report the first evidence of non-mandibular cranial material of a non-avian theropod from Australia: a left frontal and fused parietal fragment from the Lower Cretaceous (lower Aptian) upper Strzelecki Group of Victoria. The specimen shares several synapomorphies with the frontals assigned to Megaraptoridae, including an anteroposteriorly elongate postorbital articulation and a truncated nasal articular surface. Accordingly, we regard this frontal as Megaraptoridae gen. et sp. indet. We performed both parsimony-based and Bayesian-based phylogenetic analyses to support our assignment, and both analyses support a placement within Megaraptoridae. However, this specimen appears to possess plesiomorphic characters relative to other megaraptorid frontals, lacking dorsoventrally high walls of bone that emarginate the nasal and prefrontal articular surfaces. The plesiomorphies of this specimen have implications for the evolution of the megaraptoran skull roof, suggesting the acquisition of specialised adaptations for longirostry over time. This specimen improves the limited record of Cretaceous Australian theropod cranial remains, and provides limited support for the hypothesis that Megaraptoridae might have originated in Australia.

A new vertebrate assemblage from the Matute Formation of the Cameros Basin (Ágreda, Spain): implications for the diversity during the Jurassic/Cretaceous boundary

The Ribota site (Ágreda, Soria, Spain) is a new locality in the Matute Formation (Tithonian–Berriasian) composed of several carbonate layers, outstandingly rich in macrovertebrate remains. Fossils show an unusual replacement of the original bioapatite by quartz, and are found as positive reliefs protruding from lacustrine limestone beds. This type of conservation has allowed the identification of around one hundred vertebrate bone accumulations in an outcrop of more than 10 hectares. Osteichthyans (articulated partial skeletons, cranial material, and isolated postcranial bones and scales), crocodylomorphs (disarticulated cranial material, isolated teeth, vertebrae and osteoderms), turtles (partial carapaces and plastra, but also isolated plates) and pterosaurs (cranial and appendicular elements) have been identified. Around 80 specimens have been collected and a preliminary study of part of the collection (35 specimens) has allowed the identification of at least 5 different taxa: Halecomorphi indet., Neoginglymodi indet., Goniopholididae indet., Testudinata indet., and Pterodactyloidea indet. This new site represents one of the few sites from this time interval preserved in a fully lacustrine environment, so these vertebrate assemblages are unique and composed of different animals that presumably lived around and within the lake. They are dominated by aquatic and amphibian vertebrates and was formed by attrition in this lacustrine environment, possibly far from the lake shoreline. These macrovertebrate assemblages provide new data about the diversity in the faunal ecosystems from the Jurassic/Cretaceous transition of the Iberian Basin Rift System.

Braincase and neuroanatomy of the lagerpetid Dromomeron gregorii (Archosauria, Pterosauromorpha) with comments on the early evolution of the braincase and associated soft tissues in Avemetatarsalia.

The anatomy of the braincase and associated soft tissues of the lagerpetid Dromomeron gregorii (Archosauria: Avemetatarsalia) from the Late Triassic of the United States is here described. This corresponds to the first detailed description of cranial materials of Lagerpetidae, an enigmatic group of Late Triassic (c. 236-200 Million years ago) animals that are the closest known relatives of pterosaurs, the flying reptiles. The braincase of D. gregorii is characterized by the presence of an anteriorly elongated laterosphenoid and a postparietal, features observed in stem-archosaurs but that were still unknown in early members of the avian lineage of archosaurs. Using micro-computed tomography (CT-scan data), we present digital reconstructions of the brain and endosseous labyrinth of D. gregorii. The brain of D. gregorii exhibits a floccular lobe of the cerebellum that projects within the space of the semicircular canals. The semicircular canals are relatively large when compared to other archosauromorphs, with the anterior canal exhibiting a circular shape. These features of the sensory structures of D. gregorii are more similar to those of pterosaurs than to those of other early avemetatarsalians. In sum, the braincase anatomy of D. gregorii shows a combination of plesiomorphic and apomorphic features in the phylogenetic context of Archosauria and suggests that the still poorly understood early evolution of the braincase in avemetatarsalians is complex, with a scenario of independent acquisitions and losses of character states.

Craniomandibular anatomy of a juvenile specimen of Edmontosaurus regalis Lambe, 1917 clarifies issues in ontogeny and biogeography

ABSTRACT Edmontosaurus regalis is a hadrosaurid represented by abundant fossil material from the late Campanian–early Maastrichtian of what is now Alberta, Canada. Despite its prevalence, juvenile craniomandibular elements of E. regalis are poorly known. A newly collected partial skeleton from the Horseshoe Canyon Formation, UALVP 60425, represents a small saurolophine with a partial skull (skull length ∼500 mm). It can be referred to Edmontosaurini based on the presence of a postorbital fossa and anteroposteriorly long frontals that lack a dorsally oriented nasal contact and contribute significantly to the orbital margin. Despite its small size and presumed immaturity, UALVP 60425 is assigned to E. regalis based on a horizontal shelf on the postorbital process of the jugal. The deep postorbital fossa that, in part, diagnoses E. regalis is acquired during growth. UALVP 60425 shares many features with the Alaskan Prince Creek saurolophine (Ugrunaaluk kuukpikensis); both show consistent anatomical differences in the lacrimal, jugal, and postorbitals from E. annectens throughout their growth series. New data from UALVP 6025 supports referring the Alaskan saurolophine material to Edmontosaurus cf. regalis in the absence of large-sized cranial material from the Prince Creek Formation.

Межгрупповая изменчивость краниометрических характеристик населения Средней Азии в 1500-летней ретроспективе (VII в. до н.э. – VIII в. н.э.)

Introduction. The paper revisits the intergroup craniometric variability in the Early Iron Age, Antiquity and Early medieval Central Asian population. Some new cranial materials are considered within the hierarchical system of the regional populations. Materials and methods. The comparison included 61 cranial samples from all historical and cultural regions of Central Asia with a total of 1100 crania. 12 standard measurements of the facial skeleton were used. First, we conducted Canonical discriminant analysis. Second, the matrix of Mahalanobis D2 distances was obtained using the resulting group coordinates in the space of the canonical vectors. Finally, the distance matrix was subjected to Multidimensional scaling and the Ward’s hierarchical cluster analysis. Results. The first three canonical variates reflect 53.4% of the total intergroup variation and differentiate samples based on bizygomatic breadth, orbit dimensions, nasal bridge height (and width to a lesser extent), horizontal profiling angles and nose protrusion angle. Upper facial height also contributes to intergroup craniometric variability but does not play a decisive role in differentiating among samples of European ancestry in the considered chronological period. Correlation coefficients between canonical variables and multidimensional scaling coordinates suggest similar relative positions of the groups in the scatterplots. Discussion. Considering the mixed nature of the Central Asian population and the difficulty of objective differentiation of morphological types, we caution against unreflective use of terms “East Mediterranean type” and “Pamir-Fergana race”. The results suggest that the Antiquity and Early medieval sedentary populations are difficult to distinguish from nomadic and semi-nomadic groups of the Wusun period. The new materials confirm the morphological similarity between Early medieval population of Sogdiana (ancient Panjakent) and Ushrusana (Kurkat dakhmaks). @ 2023. This work is licensed under a CC BY 4.0 license

Redescription of the soft-shell turtle Rafetus bohemicus (Testudines, Trionychidae) from the Early Miocene of Czechia.

The taxonomy of the soft-shell turtle Rafetus bohemicus (Liebus, 1930), family Trionychidae, subfamily Trionychinae, is revised based on new and previously mentioned material (including the type material) from the Early Miocene (Burdigalian, MN 3) sites of the Most Basin, Czechia. Given that the diagnosis was so far based only on plastral elements, here we focused on the cranial material and combined our study with previously published data on postcranial elements. 3D models of the skulls derived from CT scans allow us to provide the first complete skull description of R. bohemicus, including several new cranial diagnostic characters of the species. Our results not only enable the distinction of the trionychid genera Trionyx and Rafetus, both recorded from Central Europe during the Early Miocene, but further allow us to provide an emended diagnosis for R. bohemicus. We confirm the conclusions of a previous study according to which Trionyx pontanus, T. preschenensis, T. aspidiformis, and T. elongatus are nomina dubia. R. bohemicus from Břešt'any (MN 3) represents the oldest record of this genus in Europe as well as the oldest occurrence of the genus.

Craniometric study of Central Asian population at the turn of the era: multivariate statistics versus typological approach?

The article aims to assess the method of individual visual typological definitions in biological anthropology and compare it with the results of multivariate statistical analysis based on the cranial materials coming mainly from the Yuezhi / Kushan period in Central Asia. The database contains information on 185 crania. We have established that sex has a highly significant effect on the variation of facial craniometric traits, while the effect of artificial deformation is less prominent but still statistically significant. The PCA has shown that variation between the cranial types of very distant ancestry is captured even though the samples are small and variables are limited to the traits of facial skeleton. The PCA has highlighted the craniometric distinctiveness of the crania labeled as having Asian ancestry. The PCА of the sample of European ancestry has not revealed either the distinctiveness of the mixed European-Asian ancestry individuals or the differences between the two large morphological types within the sample of European ancestry. The differences between individuals of different anthropological types could be due to the effects of random variation which have been consistently interpreted as non-random.

New postcranial remains of ground sloths (Xenarthra, Folivora, Mylodontidae) from Southern Brazil

Diagnoses of Mylodontidae species are generally based on skull, mandibular, and tooth characteristics, and rarely on postcranial morphology, due to the lack of postcranial material associated with the cranial material. The studies of postcranial anatomy have generally a biomechanical focus and reflect a set of functions of skeletal structures, but their interpretation in phylogenetic analysis is still limited. In Pleistocene deposits of Rio Grande do Sul State, Brazil, an important set of postcranial specimens was collected, belonging to Mylodontidae. They were morphologically and morphometrically analyzed, allowing us to observe some diagnostic characters such as the humeral entepicondylar foramen and crests, shape of the radial shaft, angle of distal articulation of the tibia, as well as the angle of proximal articulation of the astragalus. The material was also compared with specimens from other South American localities. Most of the remains were assigned to Glossotherium robustum and Lestodon armatus. In addition, a new Scelidotheriinae was recorded for Rio Grande do Sul State. The study indicated significant differences in the postcranial morphology, which allowed the recognition of some specific diagnostic characters. Keywords: Mylodontinae, Scelidotheriinae, hindlimb, forelimb, Pleistocene, Rio Grande do Sul.

Cranial Material of Long-Snouted Dolphins (Cetacea, Odontoceti, Eurhinodelphinidae) from the Early Miocene of Rosignano Monferrato, Piedmont (NW Italy): Anatomy, Paleoneurology, Phylogenetic Relationships and Paleobiogeography

We provide a new study of previously published eurhinodelphinid materials from the early Miocene of Piedmont (NW Italy) based on a new preparation of the fossil specimens. We studied specimens previously assigned to Tursiops miocaenus and Dalpiazella sp. and provide new anatomical data on the eurhinodelphinid skull and ear bones. In particular, we suggest that a skull that was previously assigned to Tursiops miocaenus must be reassigned to Ziphiodelphis sigmoideus (Cetacea, Odontoceti, Eurhinodelphinidae) based on new comparisons of the squamosal. This finding enabled us to provide new anatomical information on the ear bone anatomy of Z. sigmoideus that was previously unknown. The material originally assigned to Tursiops miocaenus is currently lost. For this reason and due to the fact that the partial illustration of this species by Portis does not allow us to find diagnostic characters for this species, we decided that Tursiops miocaenus is a nomen dubium. Analysis of additional isolated teeth previously assigned to Tursiops miocaenus led to the conclusion that these specimens represent Odontoceti incertae sedis. We performed a new phylogenetic analysis by adding newly discovered character states to a previous dataset and a paleobiogeographic analysis of Eurhinodelphinidae. We found two monophyletic clades within this family. The paleobiogeographic pattern found by the present work suggests the existence of North Atlantic and Mediterranean clades with some species distributed among both basins. We analyzed the virtual endocast of Ziphiodelphis sigmoideus and found that it resembles that of Schizodelphis in several respects, suggesting that some of the more derived characters of the odontocete brain were still absent in these early Miocene eurhinodelphinids.

Progress in the Research of Skull Repair Materials

Skull defect is a common clinical neurosurgery disease. If not repaired in time, it will seriously threaten the safety of patients. The skull defect repair of children is more complicated because their skull is in the growth stage. To improve the treatment level of skull defect, skull repair materials used to replace skull defects have evolved in recent years. An ideal material for skull repair should meet the requirements of good osseointegration, biodegradability and conformability, and finally a perfect fusion with the surrounding bone tissue. In this article, the evolution of current materials utilized in cranioplasty are comprehensively reviewed. Firstly, the existing situation of skull repair materials used in clinical practice are first introduced, including autologous cranial materials and synthetic materials. Secondly, the research hotspots of skull repair materials are summarized, including bone-induced framework and growth factors, and points out the scientific problems that need to be solved in the current research. Finally, the future development direction and clinical application prospect of skull repair are prospected, in order to provide the thinking and reference for the treatment of skull defect.

Fossils Explained 83: Diversity of skull morphology in the Titanosauria

Titanosaurs were a globally distributed group of sauropod dinosaurs. They had diverse forms and a wide-gauge stance, with a few of their species reaching immense sizes, such as Argentinosaurus huinculensis and Patagotitan mayorum (reaching >35 m in length). There are about 100 valid titanosaur species known so far, but most of the originally described species are no longer valid, due to the incomplete nature of fossil materials. Our understanding of titanosaur skull morphology is based on very few incomplete fragmented cranial materials and findings of the complete skull are even rarer. Understanding the skull morphology of extinct animals helps palaeontologists make deductions of feeding mechanisms and also provide an idea about their appearance when they were alive. Diversity in titanosaur skull morphology is greater than that of any other sauropod clade, indicating diversity in feeding mechanism among these dinosaurs. Titanosaurs were the last surviving clade of sauropod dinosaurs, occupying nearly every ecological niche around the world during the Late Cretaceous, and resulting in a rich diversity in this group. This article highlights diversity in the basic structure of sauropods with special emphasis on titanosaur skull morphology.

Insight into the evolutionary assemblage of cranial kinesis from a Cretaceous bird.

The independent movements and flexibility of various parts of the skull, called cranial kinesis, are an evolutionary innovation that is found in living vertebrates only in some squamates and crown birds and is considered to be a major factor underpinning much of the enormous phenotypic and ecological diversity of living birds, the most diverse group of extant amniotes. Compared to the postcranium, our understanding of the evolutionary assemblage of the characteristic modern bird skull has been hampered by sparse fossil records of early cranial materials, with competing hypotheses regarding the evolutionary development of cranial kinesis among early members of the avialans. Here, a detailed three-dimensional reconstruction of the skull of the Early Cretaceous enantiornithine Yuanchuavis kompsosoura allows for its in-depth description, including elements that are poorly known among early-diverging avialans but are central to deciphering the mosaic assembly of features required for modern avian cranial kinesis. Our reconstruction of the skull shows evolutionary and functional conservation of the temporal and palatal regions by retaining the ancestral theropod dinosaurian configuration within the skull of this otherwise derived and volant bird. Geometric morphometric analysis of the palatine suggests that loss of the jugal process represents the first step in the structural modifications of this element leading to the kinetic crown bird condition. The mixture of plesiomorphic temporal and palatal structures together with a derived avialan rostrum and postcranial skeleton encapsulated in Yuanchuavis manifests the key role of evolutionary mosaicism and experimentation in early bird diversification.

New giant theropod material from the Kem Kem Compound Assemblage (Morocco) with implications on the diversity of the mid-Cretaceous carcharodontosaurids from North Africa

ABSTRACT The ‘Kem Kem Compound Assemblage’ (KKCA) along the Algerian-Moroccan border is a series of fossiliferous localities, Cenomanian in age, particularly rich in large-bodied theropod dinosaurs. Two species of carcharodontosaurid allosauroids have been identified in these units, Carcharodontosaurus saharicus and Sauroniops pachytholus. Recently, the validity of the second species has been challenged, and all carcharodontosaurid material from the KKCA has been referred uniquely to the former species. Here, we describe a new theropod cranial material from the KKCA which is referred to Carcharodontosauridae, including one partial maxilla which shows a morphology distinct from that of C. saharicus. We review the arguments used to interpret Sauroniops holotype as an immature individual of Carcharodontosaurus and show that they were based on non-homologous comparisons and on the misinterpretation of the original description of S. pachytholus: The latter is confirmed to be a valid taxon, distinct from C. saharicus and with an inferred body size comparable to the largest carcharodontosaurids. The presence of more than one giant carcharodontosaurid species in the Cenomanian of Morocco recalls the carcharodontosaurid diversity from penecontemporary units from Argentina.