Shed teeth from Portezuelo formation at Sierra del Portezuelo reveal a higher diversity of predator theropods during Turonian-Coniacian times in northern Patagonia

The study of thirty-two shed crowns from the Portezuelo Formation (middle Turonian-late Coniacian) at the Sierra del Portezuelo locality, reveals six distinct tooth morphotypes identified through cladistic, discriminant, and cluster analyses. Two morphotypes were identified as belonging to Megaraptoridae, three to Abelisauridae, one to Abelisauroidea, and one to Alvarezsauridae. Additionally, two of the morphotypes exhibit a combination of dental features typically found in megaraptorid and abelisauridtheropods. These results suggest a greater diversity of theropods in the original ecosystem than previously thought, including the presence of a second morphotype of megaraptorid and alvarezsaurid previously undocumented in this formation. Furthermore, the existence of Morphotype 6 indicates the potential coexistence of medium-sized abelisauroids alongside larger abelisaurids in the same ecosystem. These findings underscore the importance of future expeditions to the Sierra del Portezuelo locality to further our understanding of these previously unknown theropod species.

New information on paleopathologies in non-avian theropod dinosaurs: a case study on South American abelisaurids

Studies on pathological fossil bones have allowed improving the knowledge of physiology and ecology, and consequently the life history of extinct organisms. Among extinct vertebrates, non-avian dinosaurs have drawn attention in terms of pathological evidence, since a wide array of fossilized lesions and diseases were noticed in these ancient organisms. Here, we evaluate the pathological conditions observed in individuals of different brachyrostran (Theropoda, Abelisauridae) taxa, including Aucasaurus garridoi, Elemgasem nubilus, and Quilmesaurus curriei. For this, we use multiple methodological approaches such as histology and computed tomography, in addition to the macroscopic evaluation. The holotype of Aucasaurus shows several pathognomonic traits of a failure of the vertebral segmentation during development, causing the presence of two fused caudal vertebrae. The occurrence of this condition in Aucasaurus is the first case to be documented so far in non-tetanuran theropods. Regarding the holotype of Elemgasem, the histology of two fused vertebrae shows an intervertebral space between the centra, thus the fusion is limited to the distal rim of the articular surfaces. This pathology is here considered as spondyloarthropathy, the first evidence for a non-tetanuran theropod. The microstructural arrangement of the right tibia of Quilmesaurus shows a marked variation in a portion of the outer cortex, probably due to the presence of the radial fibrolamellar bone tissue. Although similar bone tissue is present in other extinct vertebrates and the cause of its formation is still debated, it could be a response to some kind of pathology. Among non-avian theropods, traumatic injuries are better represented than other maladies (e.g., infection, congenital or metabolic diseases, etc.). These pathologies are recovered mainly among large-sized theropods such as Abelisauridae, Allosauridae, Carcharodontosauridae, and Tyrannosauridae, and distributed principally among axial elements. Statistical tests on the distribution of injuries in these theropod clades show a strong association between taxa-pathologies, body regions-pathologies, and taxa-body regions, suggesting different life styles and behaviours may underlie the frequency of different injuries among theropod taxa.

Developmental strategies underlying gigantism and miniaturization in non-avialan theropod dinosaurs

In amniotes, the predominant developmental strategy underlying body size evolution is thought to be adjustments to the rate of growth rather than its duration. However, most theoretical and experimental studies supporting this axiom focus on pairwise comparisons and/or lack an explicit phylogenetic framework. We present the first large-scale phylogenetic comparative analysis examining developmental strategies underlying the evolution of body size, focusing on non-avialan theropod dinosaurs. We reconstruct ancestral states of growth rate and body mass in a taxonomically rich dataset, finding that contrary to expectations, changes in the rate and duration of growth played nearly equal roles in the evolution of the vast body size disparity present in non-avialan theropods-and perhaps that of amniotes in general.

The effects of skull flattening on suchian jaw muscle evolution

Jaw muscles are key features of the vertebrate feeding apparatus. The jaw musculature is housed in the skull whose morphology reflects a compromise between multiple functions, including feeding, housing sensory structures, and defense, and the skull constrains jaw muscle geometry. Thus, jaw muscle anatomy may be suboptimally oriented for the production of bite force. Crocodylians are a group of vertebrates that generate the highest bite forces ever measured with a flat skull suited to their aquatic ambush predatory style. However, basal members of the crocodylian line (e.g., Prestosuchus) were terrestrial predators with plesiomorphically tall skulls, and thus the origin of modern crocodylians involved a substantial reorganization of the feeding apparatus and its jaw muscles. Here, we reconstruct jaw muscles across a phylogenetic range of crocodylians and fossil suchians to investigate the impact of skull flattening on muscle anatomy. We used imaging data to create 3D models of extant and fossil suchians that demonstrate the evolution of the crocodylian skull, using osteological correlates to reconstruct muscle attachment sites. We found that jaw muscle anatomy in early fossil suchians reflected the ancestral archosaur condition but experienced progressive shifts in the lineage leading to Metasuchia. In early fossil suchians, musculus adductor mandibulae posterior and musculus pterygoideus (mPT) were of comparable size, but by Metasuchia, the jaw musculature is dominated by mPT. As predicted, we found that taxa with flatter skulls have less efficient muscle orientations for the production of high bite force. This study highlights the diversity and evolution of jaw muscles in one of the great transformations in vertebrate evolution.

On the homology of crocodylian post-dentary bones and their macroevolution throughout Pseudosuchia

The lower jaw of early tetrapods is composed of several intramembranous ossifications. However, a tendency toward the independent reduction of the number of bones has been observed in the mandible of mammals, lepidosaurs, turtles, crocodiles, and birds. Regarding archosaurs, the coronoid and prearticular bones are interpreted to be lost during the evolution of stem-birds and stem-crocodiles, respectively, but the homology of the post-dentary bones retained in living pseudosuchians remains unclear. Here, we combine paleontological and embryological evidence to explore in detail the homology of the crocodylian post-dentary bones. We study the mandible embryogenesis on a sample of 71 embryos of Caiman and compare this pattern with the mandibular transformations observed across pseudosuchian evolution. In the pre-hatching ontogeny of caimans, at least five intramembranous ossification centers are formed along the margins of the internal mandibular fenestra (perifenestral centers) and, subsequently, merge to form the coronoid (three intramembranous centers), angular (one intramembranous center), and articular (one intramembranous and one chondral center). In the fossil record, an independent prearticular is lost around the base of Mesoeucrocodylia (optimized as reappearing in Thalattosuchia if they are placed within Neosuchia), and the coronoid is apomorphically lost in notosuchians. The integration of embryological and paleontological data indicates that most perifenestral centers are involved in the origin of the prearticular of non-mesoeucrocodylian pseudosuchians. These centers are rearranged during the evolution to contribute to different post-dentary bones in mesoeucrocodylians bolstering the idea that the coronoid and the articular of Crocodylia are not completely homologous to those of other diapsids.

Cost and prescription trends of P2Y12 inhibitors in Australia over the last decade

Funding Acknowledgements

Type of funding sources: None.

Background

Coronary artery disease (CAD) remains one of the leading causes of mortality worldwide and in Australia, and places significant burden on healthcare costs. [1,2] Dual antiplatelet therapy (DAPT) is guideline therapy following acute coronary syndrome (ACS).[3] Novel, potent P2Y12 inhibitors have been developed and studied but it is unclear how this evidence has been incorporated into patient care across the spectrum of P2Y12 prescribers.

Purpose

We sought to describe the prescribing trends, healthcare costs of P2Y12 therapy in Australia over the last decade using real world prescribing data and cost per MACE prevented.

Method

The latest statistical data collected by the Pharmaceutical Benefit Scheme (PBS), Australia was reviewed. PBS codes for coronary indications were selected. Yearly total prescriptions and cost were then compared between all three P2Y12 inhibitors. Linear trend modelling was used to observe general trends over the data collection period. Cost per mace was calculated from major DAPT ACS trials [4,5].

Results

Total yearly P2Y12 scripts have increased 2.5-fold in Australia between 2010 (403,880 scripts) and 2020 (994,826 scripts). Clopidogrel is the most prescribed P2Y12 inhibitor and has been for the last decade, representing 71% of P2Y12 prescriptions in 2020. Ticagrelor represented 26.2% of total prescriptions but accounts for 75% of PBS spending. More than $30 million is spent on ticagrelor yearly with a cost per MACE prevented of $72,637. Prasugrel was the least prescribed agent but was 41% more cost effective than ticagrelor before being removed from the Australian market. Prasugrel has a cost per MACE prevented of $42,993. Without prasugrel available, Clopidogrel scripts have increased 10% and ticagrelor scripts remain stable.

Conclusion

Clopidogrel remains the most prescribed P2Y12 agent in Australia, despite emergence of more potent P2Y12 inhibitors. Ticagrelor is increasingly prescribed but represents a disproportionately large burden of spending. Whilst Prasugrel is the most efficacious, cost effective and a guideline recommended P2Y12 inhibitor after ACS, it represented the minority of scripts before being withdrawn. Rather than use of a potent P2Y12 agent, clinicians are reverting to prescribing clopidogrel. Compared to other countries in the Asia Pacific region with access to prasugrel, Australian patients may be having higher rates of MACE post PCI at a higher cost compared to Ticagrelor. Abstract Figure.  Abstract Figure.

Complex macroevolutionary dynamics underly the evolution of the crocodyliform skull

All modern crocodyliforms (alligators, crocodiles and the gharial) are semi-aquatic generalist carnivores that are relatively similar in cranial form and function. However, this homogeneity represents just a fraction of the variation that once existed in the clade, which includes extinct herbivorous and marine forms with divergent skull structure and function. Here, we use high-dimensional three-dimensional geometric morphometrics to quantify whole-skull morphology across modern and fossil crocodyliforms to untangle the factors that shaped the macroevolutionary history and relatively low phenotypic variation of this clade through time. Evolutionary modelling demonstrates that the pace of crocodyliform cranial evolution is initially high, particularly in the extinct Notosuchia, but slows near the base of Neosuchia, with a late burst of rapid evolution in crown-group crocodiles. Surprisingly, modern crocodiles, especially Australian, southeast Asian, Indo-Pacific species, have high rates of evolution, despite exhibiting low variation. Thus, extant lineages are not in evolutionary stasis but rather have rapidly fluctuated within a limited region of morphospace, resulting in significant convergence. The structures related to jaw closing and bite force production (e.g. pterygoid flange and quadrate) are highly variable, reinforcing the importance of function in driving phenotypic variation. Together, these findings illustrate that the apparent conservativeness of crocodyliform skulls betrays unappreciated complexity in their macroevolutionary dynamics.

Biomechanical performance of the cranio-mandibular complex of the small notosuchian Araripesuchus gomesii (Notosuchia, Uruguaysuchidae)

Notosuchia is a clade of crocodyliforms that was highly successful and diverse in the Cretaceous of Gondwana. Araripesuchus gomesii is a small notosuchian from the Early Cretaceous of Brazil that belongs to Uruguaysuchidae, one of the subgroups of notosuchians that first radiated, during the Aptian-Albian. Here we present a finite element analysis of A. gomesii based on a model reconstructed from CT scans and performed using published bone properties for crocodiles. The adductor musculature and their respective attachment areas were reconstructed based on Extant Phylogenetic Bracket. Different functional scenarios were tested applying an estimated 158 N bite force: unilateral bite, bilateral bite, pullback, head-shake, and head-twist. The results obtained were compared with those of Alligator mississippiensis, one of its closest living relatives. In the different simulations, the skull and lower jaws of Araripesuchus suffers more stress in the head-shake movement, followed by the unilateral and pullback bites with stress focalized in the premaxillary region. In contrast, the head-twist is the one with smaller stress values. Araripesuchus possess an oreinirostral skull that may provide greater overall resistance in the different scenarios on average, unlike Alligator that has a platyrostral skull with less resistance to dorsoventral mechanical loads. Previous hypotheses that considered A. gomesii as omnivorous coupled with our results, its small size, and likely limited bite force, suggest this taxon probably fed on small prey and other trophic items that could catch and handle entirely with its mouth, such as insects and small vertebrates.

Unexpected larger distribution of paleogene stem-rollers (AVES, CORACII): new evidence from the Eocene of Patagonia, Argentina

Here we present the first record of a stem-Coracii outside the Holarctic region, found in the early Eocene of Patagonia at the Laguna del Hunco locality. Ueekenkcoracias tambussiae gen. et sp. nov. consists of an incomplete right hind limb that presents the following combination of characters, characteristic of Coracii: relatively short and stout tibiotarsus, poorly developed crista cnemialis cranialis, short and wide tarsometatarsus, with the tuberositas m. tibialis cranialis located medially on the shaft, and curved and stout ungual phalanges. Although the presence of a rounded and conspicuous foramen vasculare distale and the trochlea metatarsi II strongly deflected medially resemble Primobucconidae, a fossil group only found in the Eocene of Europe and North America, our phylogenetic analysis indicates the new taxon is the basalmost known Coracii. The unexpected presence of a stem-Coracii in the Eocene of South America indicates that this clade had a more widespread distribution than previously hypothesized, already extending into the Southern Hemisphere by the early Eocene. Ueekenkcoracias tambussiae represents new evidence of the increasing diversity of stem lineages of birds in the Eocene. The new material provides novel morphological data for understanding the evolutionary origin and radiation of rollers and important data for estimates of the divergence time of the group.

Extinction of herbivorous dinosaurs linked to Early Jurassic global warming event

Sauropods, the giant long-necked dinosaurs, became the dominant group of large herbivores in terrestrial ecosystems after multiple related lineages became extinct towards the end of the Early Jurassic (190-174 Ma). The causes and precise timing of this key faunal change, as well as the origin of eusauropods (true sauropods), have remained ambiguous mainly due to the scarce dinosaurian fossil record of this time. The terrestrial sedimentary successions of the Cañadón Asfalto Basin in central Patagonia (Argentina) document this critical interval of dinosaur evolution. Here, we report a new dinosaur with a nearly complete skull that is the oldest eusauropod known to date and provide high-precision U-Pb geochronology that constrains in time the rise of eusauropods in Patagonia. We show that eusauropod dominance was established after a massive magmatic event impacting southern Gondwana (180-184 Ma) and coincided with severe perturbations to the climate and a drastic decrease in the floral diversity characterized by the rise of conifers with small scaly leaves. Floral and faunal records from other regions suggest these were global changes that impacted the terrestrial ecosystems during the Toarcian warming event and formed part of a second-order mass extinction event.

2-year real-world outcomes of prasugrel, ticagrelor or clopidogrel therapy following percutaneous coronary intervention from a large multi-centre Australian registry

Background

Real-world data comparing outcomes for prasugrel, ticagrelor or clopidogrel use in patients undergoing percutaneous coronary intervention (PCI) is limited, with only smaller cohorts or 12-month observations available.

Methods

Data was collected prospectively from a total of 14 sites around Australia, from November 2008 until March 2019. The cohort included consecutively enrolled patients presenting electively or following acute coronary syndromes who were prescribed dual antiplatelet therapy following PCI. There were no exclusion criteria. The primary end point was the composite of death, myocardial infarction, or stroke at 1 year and 2 years after PCI. Secondary end points included safety, which was the incidence of major bleeding (BARC 3,4 or 5) at discharge.

Results

A total of 12,940 patients were included over a 11-year period. Patients receiving prasugrel were more likely to be male, younger (mean age 62.3+8.7 years), obese and present with STEMI than those receiving either ticagrelor or clopidogrel (all p<0.001). At 2 years the primary end point occurred in 120 of the 2968 patients (2.8 per 1000pyr) in the ticagrelor group, 446 of 9280 (2.7 per 1000pyr) patients in the clopidogrel group and 21 of 692 (1.8 per 1000pyr) prasugrel group (p=0.03). Major bleeding was observed in 0.2% in the ticagrelor group, 0.4% clopidogrel group and 0.1% in the prasugrel group (p=0.21).

Conclusion

For the first time we have shown in a large cohort of patients treated by PCI for ACS or CAD significantly lower 2-year rates of death, myocardial infarction and stroke amongst patients who received prasugrel than among those who received either clopidogrel or ticagrelor. The incidence of major bleeding did not differ between antiplatelet therapies.

Funding Acknowledgement

Type of funding source: None

Braincase anatomy of Almadasuchus figarii (Archosauria, Crocodylomorpha) and a review of the cranial pneumaticity in the origins of Crocodylomorpha

Almadasuchus figarii is a basal crocodylomorph recovered from the Upper Jurassic levels of the Cañadón Calcáreo Formation (Oxfordian-Tithonian) of Chubut, Argentina. This taxon is represented by cranial remains, which consist of partial snout and palatal remains; an excellently preserved posterior region of the skull; and isolated postcranial remains. The skull of the only specimen of the monotypic Almadasuchus was restudied using high-resolution computed micro tomography. Almadasuchus has an apomorphic condition in its skull shared with the closest relatives of crocodyliforms (i.e. hallopodids) where the quadrates are sutured to the laterosphenoids and the otoccipital contacts the quadrate posterolaterally, reorganizing the exit of several cranial nerves (e.g. vagus foramen) and the entry of blood vessels (e.g. internal carotids) on the occipital surface of the skull. The endocast is tubular, as previously reported in thalattosuchians, but has a marked posterior step, and a strongly projected floccular recess as in other basal crocodylomorphs. Internally, the skull of Almadasuchus is heavily pneumatized, where different air cavities invade the bones of the suspensorium and braincase, both on its dorsal or ventral parts. Almadasuchus has a large basioccipital recess, which is formed by cavities that excavate the basioccipital and the posterior surface of the basisphenoid, and unlike other crocodylomorphs is connected with the basisphenoid pneumatizations. Ventral to the otic capsule, a pneumatic cavity surrounded by the otoccipital and basisphenoid is identified as the rhomboidal recess. The quadrate of Almadasuchus is highly pneumatized, being completely hollow, and the dorsal pneumatizations of the braincase are formed by the mastoid and facial antra, and a laterosphenoid cavity (trigeminal diverticulum). To better understand the origins of pneumatic features in living crocodylomorphs we studied cranial pneumaticity in the basal members of Crocodylomorpha and found that: (a) prootic pneumaticity may be a synapomorphy for the whole clade; (b) basisphenoid pneumaticity (pre-, postcarotid and rostral recesses) is a derived feature among basal crocodylomorphs; (c) quadrate pneumatization is acquired later in the history of the group; and (d) the rhomboidal sinus is a shared derived trait of hallopodids and crocodyliforms. The marine thallatosuchians exhibit a reduction of the pneumaticity of the braincase and this reduction is evaluated considering the two phylogenetic positions proposed for the clade.

Evolutionary Integration and Modularity in the Archosaur Cranium

Complex structures, like the vertebrate skull, are composed of numerous elements or traits that must develop and evolve in a coordinated manner to achieve multiple functions. The strength of association among phenotypic traits (i.e., integration), and their organization into highly-correlated, semi-independent subunits termed modules, is a result of the pleiotropic and genetic correlations that generate traits. As such, patterns of integration and modularity are thought to be key factors constraining or facilitating the evolution of phenotypic disparity by influencing the patterns of variation upon which selection can act. It is often hypothesized that selection can reshape patterns of integration, parceling single structures into multiple modules or merging ancestrally semi-independent traits into a strongly correlated unit. However, evolutionary shifts in patterns of trait integration are seldom assessed in a unified quantitative framework. Here, we quantify patterns of evolutionary integration among regions of the archosaur skull to investigate whether patterns of cranial integration are conserved or variable across this diverse group. Using high-dimensional geometric morphometric data from 3D surface scans and computed tomography scans of modern birds (n = 352), fossil non-avian dinosaurs (n = 27), and modern and fossil mesoeucrocodylians (n = 38), we demonstrate that some aspects of cranial integration are conserved across these taxonomic groups, despite their major differences in cranial form, function, and development. All three groups are highly modular and consistently exhibit high integration within the occipital region. However, there are also substantial divergences in correlation patterns. Birds uniquely exhibit high correlation between the pterygoid and quadrate, components of the cranial kinesis apparatus, whereas the non-avian dinosaur quadrate is more closely associated with the jugal and quadratojugal. Mesoeucrocodylians exhibit a slightly more integrated facial skeleton overall than the other grades. Overall, patterns of trait integration are shown to be stable among archosaurs, which is surprising given the cranial diversity exhibited by the clade. At the same time, evolutionary innovations such as cranial kinesis that reorganize the structure and function of complex traits can result in modifications of trait correlations and modularity.

Probable basal allosauroid from the early Middle Jurassic Cañadón Asfalto Formation of Argentina highlights phylogenetic uncertainty in tetanuran theropod dinosaurs

Tetanurae, the most successful clade of theropod dinosaurs, including modern birds, split into three major clades early in their evolutionary history: Megalosauroidea, Coelurosauria, and Allosauroidea. The oldest tetanurans occur in the earliest Middle Jurassic, but the early fossil record of the clade is still poor. Here we report one of the oldest known and most complete pre-Late Jurassic tetanuran, the probable allosauroid Asfaltovenator vialidadi gen. et sp. nov., which has an unusual character combination, uniting features currently considered to be apomorphic of different tetanuran lineages. A phylogenetic analysis resulted in a monophyletic Carnosauria (Allosauroidea + Megalosauroidea), and the inclusion of the new taxon significantly changes topology within carnosaurs. The analysis shows concentrated homoplasy in proximal nodes at the base of Tetanurae, and a temporal peak at the Pliensbachian-Toarcian extinction event, recently identified as a potential driver of tetanuran radiation. These results highlight the complex morphological evolution in the early radiation of tetanuran theropods, in which convergences and parallelisms were extremely common. This pattern seems to be a common feature in rapid radiation events of major clades of vertebrates and might explain the common difficulties to unravel phylogenetic relationships of important lineages at the base of major clades.

Ontogenetic changes in the body plan of the sauropodomorph dinosaur Mussaurus patagonicus reveal shifts of locomotor stance during growth

Ontogenetic information is crucial to understand life histories and represents a true challenge in dinosaurs due to the scarcity of growth series available. Mussaurus patagonicus was a sauropodomorph dinosaur close to the origin of Sauropoda known from hatchling, juvenile and mature specimens, providing a sufficiently complete ontogenetic series to reconstruct general patterns of ontogeny. Here, in order to quantify how body shape and its relationship with locomotor stance (quadruped/biped) changed in ontogeny, hatchling, juvenile (~1 year old) and adult (8+ years old) individuals were studied using digital models. Our results show that Mussaurus rapidly grew from about 60 g at hatching to ~7 kg at one year old, reaching >1000 kg at adulthood. During this time, the body's centre of mass moved from a position in the mid-thorax to a more caudal position nearer to the pelvis. We infer that these changes of body shape and centre of mass reflect a shift from quadrupedalism to bipedalism occurred early in ontogeny in Mussaurus. Our study indicates that relative development of the tail and neck was more influential in determining the locomotor stance in Sauropodomorpha during ontogeny, challenging previous studies, which have emphasized the influence of hindlimb vs. forelimb lengths on sauropodomorph stance.

Morphological Data Sets Fit a Common Mechanism Much More Poorly than DNA Sequences and Call Into Question the Mkv Model

The Mkv evolutionary model, based on minor modifications to models of molecular evolution, is being increasingly used to infer phylogenies from discrete morphological data, often producing different results from parsimony. The critical difference between Mkv and parsimony is the assumption of a "common mechanism" in the Mkv model, with branch lengths determining that probability of change for all characters increases or decreases at the same tree branches by the same exponential factor. We evaluate whether the assumption of a common mechanism applies to morphology, by testing the implicit prediction that branch lengths calculated from different subsets of characters will be significantly correlated. Our analysis shows that DNA (38 data sets tested) is often compatible with a common mechanism, but morphology (86 data sets tested) generally is not, showing very disparate branch lengths for different character partitions. The low levels of branch length correlation demonstrated for morphology (fitting models without a common mechanism) suggest that the Mkv model is too unrealistic and inadequate for the analysis of most morphological data sets. [Bayesian analysis; Mkv model; morphological data; phylogenetics.].

The Long Bone Histology of the Sauropodomorph, Antetonitrus ingenipes

This analysis of the long bone microstructure of Antetonitrus ingenipes fills a crucial gap in our understanding of the growth dynamics of sauropodomorph dinosaurs. The bone histology of basal Sauropodomorpha are often characterized by zonal tissue, and contrasts with that of more derived sauropod taxa which show a shift toward the deposition of uninterrupted fibrolamellar bone (with lines of growth being either absent or only present in the outer circumferential layer). In Antetonitrus, growth patterns in the youngest individuals exhibit uninterrupted fibrolamellar bone without any growth marks. Sub-adult individuals, also exhibit highly vascularized fibrolamellar bone throughout the cortex, as in more derived Sauropods and Mussaurus, but growth lines occur intermittently (although not regularly) throughout the cortex as in Lessemsaurus. This indicates that Antetonitrus does not exhibit the growth dynamics previously considered characteristic of Sauropoda. Despite this, the largest (and possibly the oldest femur, NMQR 1705/163) does show an incipient external fundamental system (EFS). Our findings further suggest that growth marks are decoupled from bone size, which indicates a level of developmental plasticity in this taxon. Modulations or textural shifts in the pattern of vascular channel arrangements throughout the fibrolamellar bone in the cortex may be related to periods of resource limitations, although the lack of consistency of these modulations suggest that it is unlikely due to seasonal fluctuations. Localized bands of radial fibrolamellar bone, followed by resumption of normal growth in two samples are interpreted as evidence of a disease infliction, and subsequent recovery thereof. Anat Rec, 301:1506-1518, 2018. © 2018 Wiley Periodicals, Inc.

Forelimb muscle and joint actions in Archosauria: insights from Crocodylus johnstoni (Pseudosuchia) and Mussaurus patagonicus (Sauropodomorpha)

Many of the major locomotor transitions during the evolution of Archosauria, the lineage including crocodiles and birds as well as extinct Dinosauria, were shifts from quadrupedalism to bipedalism (and vice versa). Those occurred within a continuum between more sprawling and erect modes of locomotion and involved drastic changes of limb anatomy and function in several lineages, including sauropodomorph dinosaurs. We present biomechanical computer models of two locomotor extremes within Archosauria in an analysis of joint ranges of motion and the moment arms of the major forelimb muscles in order to quantify biomechanical differences between more sprawling, pseudosuchian (represented the crocodile Crocodylus johnstoni) and more erect, dinosaurian (represented by the sauropodomorph Mussaurus patagonicus) modes of forelimb function. We compare these two locomotor extremes in terms of the reconstructed musculoskeletal anatomy, ranges of motion of the forelimb joints and the moment arm patterns of muscles across those ranges of joint motion. We reconstructed the three-dimensional paths of 30 muscles acting around the shoulder, elbow and wrist joints. We explicitly evaluate how forelimb joint mobility and muscle actions may have changed with postural and anatomical alterations from basal archosaurs to early sauropodomorphs. We thus evaluate in which ways forelimb posture was correlated with muscle leverage, and how such differences fit into a broader evolutionary context (i.e. transition from sprawling quadrupedalism to erect bipedalism and then shifting to graviportal quadrupedalism). Our analysis reveals major differences of muscle actions between the more sprawling and erect models at the shoulder joint. These differences are related not only to the articular surfaces but also to the orientation of the scapula, in which extension/flexion movements in Crocodylus (e.g. protraction of the humerus) correspond to elevation/depression in Mussaurus. Muscle action is highly influenced by limb posture, more so than morphology. Habitual quadrupedalism in Mussaurus is not supported by our analysis of joint range of motion, which indicates that glenohumeral protraction was severely restricted. Additionally, some active pronation of the manus may have been possible in Mussaurus, allowing semi-pronation by a rearranging of the whole antebrachium (not the radius against the ulna, as previously thought) via long-axis rotation at the elbow joint. However, the muscles acting around this joint to actively pronate it may have been too weak to drive or maintain such orientations as opposed to a neutral position in between pronation and supination. Regardless, the origin of quadrupedalism in Sauropoda is not only linked to manus pronation but also to multiple shifts of forelimb morphology, allowing greater flexion movements of the glenohumeral joint and a more columnar forelimb posture.

A new giant titanosaur sheds light on body mass evolution among sauropod dinosaurs

Titanosauria was the most diverse and successful lineage of sauropod dinosaurs. This clade had its major radiation during the middle Early Cretaceous and survived up to the end of that period. Among sauropods, this lineage has the most disparate values of body mass, including the smallest and largest sauropods known. Although recent findings have improved our knowledge on giant titanosaur anatomy, there are still many unknown aspects about their evolution, especially for the most gigantic forms and the evolution of body mass in this clade. Here we describe a new giant titanosaur, which represents the largest species described so far and one of the most complete titanosaurs. Its inclusion in an extended phylogenetic analysis and the optimization of body mass reveals the presence of an endemic clade of giant titanosaurs inhabited Patagonia between the Albian and the Santonian. This clade includes most of the giant species of titanosaurs and represents the major increase in body mass in the history of Titanosauria.

Novel insight into the origin of the growth dynamics of sauropod dinosaurs

Sauropod dinosaurs include the largest terrestrial animals and are considered to have uninterrupted rapid rates of growth, which differs from their more basal relatives, which have a slower cyclical growth. Here we examine the bone microstructure of several sauropodomorph dinosaurs, including basal taxa, as well as the more derived sauropods. Although our results agree that the plesiomorphic condition for Sauropodomorpha is cyclical growth dynamics, we found that the hypothesized dichotomy between the growth patterns of basal and more derived sauropodomorphs is not supported. Here, we show that sauropod-like growth dynamics of uninterrupted rapid growth also occurred in some basal sauropodomorphs, and that some basal sauropods retained the plesiomorphic cyclical growth patterns. Among the sauropodomorpha it appears that the basal taxa exploited different growth strategies, but the more derived Eusauropoda successfully utilized rapid, uninterrupted growth strategies.

Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny

Background

Macelognathus vagansMarsh, 1884 from the Late Jurassic Morrison Fm. of Wyoming was originally described as a dinosaur by Marsh and in 1971 Ostrom suggested crocodilian affinities. In 2005, Göhlich and collaborators identified new material of this species from Colorado as a basal crocodylomorph. However, a partial skull found in association with mandibular and postcranial remains was not described.

Methods

Due to the small size and delicate structures within the braincase, micro CT studies were performed on this specimen. The new anatomical information was incorporated in a phylogenetic dataset, expanding both character and taxon sampling.

Results

This new material reinforces the non-crocodyliform crocodylomorph affinities of Macelognathusas it bears a large otic aperture, unfused frontals and lacks ornamentation on the dorsal cranial bones. The internal structures also support these affinities as this specimen bears traits (i.e., heavily pneumatized and expanded basisphenoid; the presence of additional pneumatic features on the braincase; and the otoccipital-quadrate contact) not present in most basal crocodylomorphs. Furthermore, the presence of a wide supraoccipital and a cranioquadrate passage are traits shared with Almadasuchus from the early Late Jurassic of Argentina. Macelognathus was recovered as one of the closest relatives of crocodyliforms, forming a clade (Hallopodidae) with two other Late Jurassic taxa (Almadasuchus and Hallopus).

Discussion

The clade formed by Almadasuchus + Hallopus + Macelognathus, the Hallopodidae, is characterized by a higher degree of suturing of the braincase, posteriorly closed otic aperture (paralleled in mesoeucrocodylians) and cursorial adaptations. Also, the phylogenetic position of this lineage of derived crocodylomorphs as the sister group of Crocodyliformes implies a large amount of unsampled record (ghost lineage), at least 50 million years.

A Jurassic pterosaur from Patagonia and the origin of the pterodactyloid neurocranium

Pterosaurs are an extinct group of highly modified flying reptiles that thrived during the Mesozoic. This group has unique and remarkable skeletal adaptations to powered flight, including pneumatic bones and an elongate digit IV supporting a wing-membrane. Two major body plans have traditionally been recognized: the primitive, primarily long-tailed paraphyletic "rhamphorhynchoids" (preferably currently recognized as non-pterodactyloids) and the derived short-tailed pterodactyloids. These two groups differ considerably in their general anatomy and also exhibit a remarkably different neuroanatomy and inferred head posture, which has been linked to different lifestyles and behaviours and improved flying capabilities in these reptiles. Pterosaur neuroanatomy, is known from just a few three-dimensionally preserved braincases of non-pterodactyloids (as Rhamphorhynchidae) and pterodactyloids, between which there is a large morphological gap. Here we report on a new Jurassic pterosaur from Argentina, Allkaruen koi gen. et sp. nov., remains of which include a superbly preserved, uncrushed braincase that sheds light on the origins of the highly derived neuroanatomy of pterodactyloids and their close relatives. A µCT ray-generated virtual endocast shows that the new pterosaur exhibits a mosaic of plesiomorphic and derived traits of the inner ear and neuroanatomy that fills an important gap between those of non-monofenestratan breviquartossans (Rhamphorhynchidae) and derived pterodactyloids. These results suggest that, while modularity may play an important role at one anatomical level, at a finer level the evolution of structures within a module may follow a mosaic pattern.

Using dental enamel wrinkling to define sauropod tooth morphotypes from the Cañadón Asfalto Formation, Patagonia, Argentina

The early Middle Jurassic is regarded as the period when sauropods diversified and became major components of the terrestrial ecosystems. Not many sites yield sauropod material of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic-early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and mandibular material as well as isolated teeth found at different localities. In this study, an assemblage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa, which are also distinguished by associated postcranial material. This study thus shows that enamel wrinkling can be used as a tool in assessing sauropod diversity.

A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians

A new notosuchian crocodyliform from the Late Cretaceous Bauru Group found in the southeastern State of São Paulo (Brazil) is described here. The new taxon, Caipirasuchus stenognathus, is referred as a new species of the recently erected genus Caipirasuchus within the clade Sphagesauridae based on a phylogenetic analysis of basal mesoeucrocodylians. Caipirasuchus stenognathus is represented by an almost complete skull and lower jaw that has autapomorphic characters that distinguish it from other species of Sphagesauridae. These autapomorphies include: maxilla forming part of the orbital margin (absence of lacrimal-jugal contact), nasal with smooth depressions on the posterior region close to the contact with the maxilla and lacrimal, postorbital with posterior palpebral facet that extends posteriorly underneath the ear-flap groove, and a distinct anterior process of the medial flange of the retroarticular process. Additionally, the new taxon lacks autapomorphic features described in other sphagesaurids. The phylogenetic analysis results in a monophyletic genus Caipirasuchus, that is the sister group of a clade fomed by Sphagesaurus huenei, Caryonosuchus pricei, and Armadillosuchus arrudai. Sphagesaurids also include a basal clade formed by Adamantinasuchus navae and Yacarerani boliviensis. Other notosuchian taxa, such as Mariliasuchus amarali, Labidiosuchus amicum, Notosuchus terrestris, and Morrinhosuchus luziae are successive sister taxa of Sphagesauridae, forming a clade of advanced notosuchians that are restricted to the Late Cretaceous of South America. These results contrast with most previous phylogenetic hypotheses of the group that depicted some members of Sphagesauridae as more closely related to baurusuchids, or found Asian (e.g., Chimaerasuchus) or African (Malawisuchus, Pakasuchus) forms nested within advanced notosuchians that are, according to our analysis, endemic of the Late Cretaceous of South America.

A new fossil from the Jurassic of Patagonia reveals the early basicranial evolution and the origins of Crocodyliformes

Extant crocodylians have a limited taxonomic and ecological diversity but they belong to a lineage (Crocodylomorpha) that includes basal and rather generalized species and a highly diverse clade, Crocodyliformes. The latter was among the most successful groups of Mesozoic tetrapods, both in terms of taxonomic and ecological diversity. Crocodyliforms thrived in terrestrial, semiaquatic, and marine environments, and their fossil diversity includes carnivorous, piscivorous, insectivorous, and herbivorous species. This remarkable ecological and trophic diversity is thought only to occur in forms with a completely akinetic skull, characterized by a functionally integrated and tightly sutured braincase-quadrate-palate complex. However, the patterns of evolutionary change that led to the highly modified skull of crocodyliforms and that likely enabled their diversification remain poorly understood. Herein, a new basal crocodylomorph from the Late Jurassic of Patagonia is described, Almadasuchus figarii gen. et sp. nov. The new taxon is known from a well-preserved posterior region of the skull as well as other craniomandibular and postcranial remains. Almadasuchus figarii differs from all other crocodylomorphs in the presence of six autapomorphic features, including the presence of a large lateral notch on the upper temporal bar, an otic shelf of the squamosal that is wider than long, a deep subtriangular concavity on the posterolateral surface of the squamosal, and an elongated pneumatopore on the ventral surface of the quadrate. Phylogenetic analysis focused on the origin of Crocodyliformes places Almadasuchus as the sister group of Crocodyliformes, supported by synapomorphic features of the skull (e.g. subtriangular basisphenoid, absence of basipterygoid process, absence of a sagittal ridge on the frontal, and a flat anterior skull roof with an ornamented dorsal surface). New braincase information provided by Almadasuchus and other crocodylomorphs indicates that most of the modifications on the posterior region of the skull of crocodyliforms, including the strongly sutured braincase, quadrate, and the extensive secondary palate appeared in a stepwise manner, and pre-dated the evolutionary changes in the snout, jaws, and dentition. This indicates that the progressively increased rigidity of the skull provided the structural framework that allowed the great ecological diversification of crocodyliforms during the course of the Mesozoic. The phylogenetic pattern of character acquisition inferred for the strongly sutured (akinetic) skull and the appearance of more diverse feeding behaviours that create high mechanical loads on the skull provides another interesting parallel between the evolution of Mesozoic crocodyliforms and the evolutionary origins of mammals.

Major radiations in the evolution of Caviid rodents: reconciling fossils, ghost lineages, and relaxed molecular clocks

BACKGROUND

Caviidae is a diverse group of caviomorph rodents that is broadly distributed in South America and is divided into three highly divergent extant lineages: Caviinae (cavies), Dolichotinae (maras), and Hydrochoerinae (capybaras). The fossil record of Caviidae is only abundant and diverse since the late Miocene. Caviids belongs to Cavioidea sensu stricto (Cavioidea s.s.) that also includes a diverse assemblage of extinct taxa recorded from the late Oligocene to the middle Miocene of South America ("eocardiids").

RESULTS

A phylogenetic analysis combining morphological and molecular data is presented here, evaluating the time of diversification of selected nodes based on the calibration of phylogenetic trees with fossil taxa and the use of relaxed molecular clocks. This analysis reveals three major phases of diversification in the evolutionary history of Cavioidea s.s. The first two phases involve two successive radiations of extinct lineages that occurred during the late Oligocene and the early Miocene. The third phase consists of the diversification of Caviidae. The initial split of caviids is dated as middle Miocene by the fossil record. This date falls within the 95% higher probability distribution estimated by the relaxed Bayesian molecular clock, although the mean age estimate ages are 3.5 to 7 Myr older. The initial split of caviids is followed by an obscure period of poor fossil record (referred here as the Mayoan gap) and then by the appearance of highly differentiated modern lineages of caviids, which evidentially occurred at the late Miocene as indicated by both the fossil record and molecular clock estimates.

CONCLUSIONS

The integrated approach used here allowed us identifying the agreements and discrepancies of the fossil record and molecular clock estimates on the timing of the major events in cavioid evolution, revealing evolutionary patterns that would not have been possible to gather using only molecular or paleontological data alone.