The Impact of Unstable Taxa in Coelurosaurian Phylogeny and Resampling Support Measures for Parsimony Analyses

Paleontological datasets often have large amounts of missing entries that result in multiple mostparsimonious trees. Highly incomplete and conflictive taxa produce a collapsed strict consensus andseveral methods have been developed for identifying these unstable or rogue taxa in optimal treesderived from phylogenetic analyses. In addition to decreasing consensus resolution, incomplete orconflictive taxa can also severely affect the support values of phylogenetic analysis in paleontologicaldatasets. Here, we explore a protocol for the identification of taxa that decrease jackknife supportvalues in parsimony analysis. The taxa identified are excluded from majority rule jackknife trees,revealing nodes that have either low or high support irrespective of the uncertainties in the placement of unstable taxa. A recently published dataset of coelurosaurian relationships based on 164taxa and 853 characters is explored using this protocol; our protocol detects a total of 40 unstabletaxa as the most detrimental for node supports. Major clades that are well supported in the reducedjackknife tree include Coelurosauria, Maniraptoriformes, Compsognathidae, Ornithomimosauria,Alvarezsauroidea, Therizinosauria, Oviraptorosauria. Clades with moderate support instead includeManiraptora, Pennaraptora, Paraves, Dromaeosauridae, Troodontidae, Anchiornithinae, and earlydiverging clades of Avialae.Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Goloboff, Pablo Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentin

Phylogenetic analysis of Gondwanan basal eusauropods from the Early-Middle Jurasic of Patagonia, Argentina

Los eusaurópodos no neosaurópodos del Jurásico de Gondwana son especies clave para la comprensión de la evolución del clado Sauropoda, aunque sus relaciones fi logenéticas siguen sin estar bien resueltas. Sin embargo, gracias a la revisión del holotipo de uno de los taxones más importantes del Jurásico Medio temprano de la Formación Cañadón Asfalto, Patagosaurus fariasi, bastantes de sus hipótesis fi logenéticas han de ser puestas en duda, basadas en la nueva información osteológica recogida durante la redescripción del holotipo de Patagosaurus. La nueva hipótesis filogenética aquí presentada muestra una relación cercana entre Patagosaurus y Cetiosaurus, del Jurásico Medio del Reino Unido. La cercanía fi logenética de Patagosaurus con Barapasaurus, publicada en numerosos análisis fi logenéticos, no se obtuvo en este nuevo análisis. En este caso, Patagosaurus aparece como un taxón más derivado que la mayoría de saurópodos del Jurásico Medio y Superior, aunque más basal que Mamenchisaurus, Omeisaurus, Turiasauria y Neosauropoda. Otro taxón que se encuentra normalmente emparentado con Patagosaurus, Volkheimeria, en nuestro análisis aparece varios nodos más basalmente que Patagosaurus. Esto muestra, junto con la presencia de otros taxones de saurópodos de la Formación de Cañadón Asfalto, que una diversidad evolutiva alta existió en el suroeste de Gondwana en el Jurásico Medio temprano, un patrón que también está presente en otros grupos fósiles (e.g., terópodos).Gondwanan Jurassic non-neosauropod eusauropods are key for the understanding of sauropod evolution, although their phylogenetic interrelationships remain poorly understood. However, following the revision of the holotype of a key taxon from the early Middle Jurassic Cañadón Asfalto Formation Patagonia, Argentina, Patagosaurus fariasi, the phylogenetic affinities need to be tested with new osteological information gathered during the redescription of the holotype of Patagosaurus. A new phylogeny presented here shows a close affiliation of Patagosaurus with Cetiosaurus from the Middle Jurassic of the UK. The close relationship of Patagosaurus with Barapasaurus, often found in previous phylogenies, was not recovered here. Instead, Patagosaurus is retrieved as more derived than most Early and Middle Jurassic sauropods, although more basal to Mamenchisaurus, Omeisaurus, turiasaurians, and neosauropods. Another sauropod taxon found together with Patagosaurus, Volkheimeria, is retrieved several nodes more basal than the former, which shows, together with evidence of several other sauropod taxa in the Cañadón Asfalto Formation, that a high evolutionary diversity existed in Southwest Gondwana in the early Middle Jurassic, a pattern which is also seen in fossil groups other than sauropods (e.g., theropods).Fil: Holwerda, Femke Marleen. No especifíca;Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentin

Phylogenetic analysis of Gondwanan basal eusauropods from the Early-Middle Jurassic of Patagonia, Argentina

Los eusaurópodos no neosaurópodos del Jurásico de Gondwana son especies clave para la comprensión de la evolución del clado Sauropoda, aunque sus relaciones fi logenéticas siguen sin estar bien resueltas. Sin embargo, gracias a la revisión del holotipo de uno de los taxones más importantes del Jurásico Medio temprano de la Formación Cañadón Asfalto, Patagosaurus fariasi, bastantes de sus hipótesis fi logenéticas han de ser puestas en duda, basadas en la nueva información osteológica recogida durante la redescripción del holotipo de Patagosaurus. La nueva hipótesis filogenética aquí presentada muestra una relación cercana entre Patagosaurus y Cetiosaurus, del Jurásico Medio del Reino Unido. La cercanía fi logenética de Patagosaurus con Barapasaurus, publicada en numerosos análisis fi logenéticos, no se obtuvo en este nuevo análisis. En este caso, Patagosaurus aparece como un taxón más derivado que la mayoría de saurópodos del Jurásico Medio y Superior, aunque más basal que Mamenchisaurus, Omeisaurus, Turiasauria y Neosauropoda. Otro taxón que se encuentra normalmente emparentado con Patagosaurus, Volkheimeria, en nuestro análisis aparece varios nodos más basalmente que Patagosaurus. Esto muestra, junto con la presencia de otros taxones de saurópodos de la Formación de Cañadón Asfalto, que una diversidad evolutiva alta existió en el suroeste de Gondwana en el Jurásico Medio temprano, un patrón que también está presente en otros grupos fósiles (e.g., terópodos).Gondwanan Jurassic non-neosauropod eusauropods are key for the understanding of sauropod evolution, although their phylogenetic interrelationships remain poorly understood. However, following the revision of the holotype of a key taxon from the early Middle Jurassic Cañadón Asfalto Formation Patagonia, Argentina, Patagosaurus fariasi, the phylogenetic affinities need to be tested with new osteological information gathered during the redescription of the holotype of Patagosaurus. A new phylogeny presented here shows a close affiliation of Patagosaurus with Cetiosaurus from the Middle Jurassic of the UK. The close relationship of Patagosaurus with Barapasaurus, often found in previous phylogenies, was not recovered here. Instead, Patagosaurus is retrieved as more derived than most Early and Middle Jurassic sauropods, although more basal to Mamenchisaurus, Omeisaurus, turiasaurians, and neosauropods. Another sauropod taxon found together with Patagosaurus, Volkheimeria, is retrieved several nodes more basal than the former, which shows, together with evidence of several other sauropod taxa in the Cañadón Asfalto Formation, that a high evolutionary diversity existed in Southwest Gondwana in the early Middle Jurassic, a pattern which is also seen in fossil groups other than sauropods (e.g., theropods).Fil: Holwerda, Femke Marleen. No especifíca;Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentin

The enamel microstructure of Manidens condorensis: New hypotheses on the ancestral state and evolution of enamel in Ornithischia

Previous studies on enamel microstructure in Ornithischia have focused on derived lineages of this clade based on species from the northern hemisphere. Here we describe the enamel microstructure of Manidens condorensis from the late Early Jurassic of Argentina that belongs to Heterodontosauridae (interpreted as the basal-most clade of Ornithischia). Enamel microstructure in the cheek teeth lacks a basal unit layer, presents incipient divergent crystallite as the dominant enamel type and parallel crystallite enamel type (with or without incrementing lines). Enamel of maxillary and dentary teeth differs from each other in enamel distribution (asymmetric vs. symmetric), structure (presence vs. absence of tubules, and less vs. more abundant parallel crystallite enamel with incrementing lines) and ordering (regular ordering of enamel types vs. in patches). The enamel microstructure of Manidens is the simplest of all known Ornithischia, and is more similar to that of the sauropodomorph Plateosaurus than to the one reported for the basal theropod Coelophysis. Similarities within Ornithischia are present with pachycephalosaurids and, to a lesser extent, with ankylosaurs. Phylogenetic optimization of enamel characters in Ornithischia allows the inference of new ancestral states for the internal nodes of the major lineages and to highlight evolutionary transformations: (i) absence of a basal unit layer and presence of parallel crystallite and incipient divergent columnar enamel as the ancestral state for Ornithischia; (ii) the shared presence of incipient divergent columnar units or poorly developed divergent columnar enamel in Pachycephalosauridae and Thyreophora represents a retention of the plesiomorphic ornithischian condition; (iii) the wavy enamel of Dryomorpha evolved from the ancestral incipient divergent columnar units present in Ornithopoda and; (iv) enamel thickness and asymmetry has independently evolved at least four times in Ornithischia.Fil: Becerra, Marcos Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentin

A middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates.Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Rauhut, Oliver W. M.. Ludwig Maximilians Universitat; Alemani

Probable basal allosauroid from the early Middle Jurassic Canadon 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

The postcranial anatomy of Coloradisaurus brevis (Dinosauria: Sauropodomorpha) from the Late Triassic of Argentina and its phylogenetic implications

Basal sauropodomorphs from the Upper Triassic Los Colorados Formation of northwestern Argentina have been known for several decades but most of them are only briefly described. New postrcanial remains of Coloradisaurus brevis, the most gracile sauropodomorph from this unit, are described here and evaluated within a phylogenetic context. These materials belong to a single individual and include elements of the vertebral column, pectoral girdle, incomplete forelimb, pelvis, and hindlimb. These elements share autapomorphic features with the type specimen of Coloradisaurus brevis, and provide novel and unique features that diagnose this taxon, such as pubic apron with semicircular cross section and with a depression on its anterior surface, distal surface of the tibia deflected and facing posterodistally, and well-developed pyramidal dorsal process of the posteromedial corner of the astragalus. Several postcranial characters of Coloradisaurus are exclusively shared with Lufengosaurus, from the Lower Jurassic of China. The inclusion of this information in two recent phylogenetic datasets depicts Coloradisaurus as closely related to Lufengosaurus and well nested within Plateosauria. Both datasets used indicate strong character support for the inclusion of Coloradisaurus and Lufengosaurus within Massospondylidae.Fil: Apaldetti, Graciela Cecilia. Universidad Nacional de San Juan. Museo de Ciencias Naturales; ArgentinaFil: Pol, Diego. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Yates, Adam. University of the Witwatersrand, Bernard Price Institute for Palaeontological Research; Sudáfric

Cranial anatomy of Gracilisuchus stipanicicorum and its evidence for maturity

Romer, 1972, a basal suchian from the upper Carnian levels of the Chañares Formation (Upper Triassic, Ischigualasto-Villa Unión Basin), is nested within Gracilisuchidae along with Turfanosuchus dabanensis Young, 1973 and Yonghesuchus sangbiensis Wu, Liu and Li, 2001. A recent study described in detail its postcranial anatomy and phylogenetic relationships, but a thorough revision of its cranial anatomy is still missing. Several diagnostic cranial characters are present, and some differences among the hypodigm can be interpreted as ontogenetic variation. Gracilisuchus has large orbit openings (35–42 % of the skull table), comparable with Euparkeria capensis Ewer, 1965 (35 %), but larger than Turfanosuchus (30 %), Yonghesuchus (25 %) and paracrocodylomorphs. The supratemporal fenestra is quadrangular and wider than long, contrasting with most archosauriforms with longer than wide or subequal fenestrae. A small triangular postparietal is present in one specimen of Gracilisuchus (MCZVP 4117), as in basal archosauriforms (e.g., Euparkeria, Erythrosuchus africanus Broom, 1905). Some cranial characters, along with postcranial features, suggest a probably younger ontogenetic stage for the holotype specimen (PULR 08), including its skull length (73 mm) that represents 80–85 % of the skull length of the referred specimens, an interparietal suture visible along the entire interparietal contact (fused posteriorly in the referred specimens). However, the anteriorly open interparietal suture, the unpreserved occipital condyles, and the large orbits in every specimen, suggest that probably none of them reached somatic maturity. Skeletochronological studies of the available specimens would be important to test this hypothesis.Fil: Lecuona, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Desojo, Julia Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; ArgentinaFil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaReunión de Comunicaciones de la Asociación Paleontológica ArgentinaLa PlataArgentinaAsociación Paleontológica Argentin

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.Fil: Felice, Ryan N.. Colegio Universitario de Londres; Reino Unido. Natural History Museum; Reino UnidoFil: Pol, Diego. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Goswami, Anjali. Natural History Museum; Reino Unid

A Middle Jurassic heterodontosaurid dinosaur from Patagonia and the evolution of heterodontosaurids

Heterodontosauridae is a morphologically divergent group of dinosaurs that has recently been interpreted as one of the most basal clades of Ornithischia. Heterodontosaurid remains were previously known from the Early Jurassic of southern Africa, but recent discoveries and studies have significantly increased the geographical and temporal range for this clade. Here, we report a new ornithischian dinosaur from the Middle Jurassic Cañadón Asfalto Formation in central Patagonia, Argentina. This new taxon, Manidens condorensis gen. et sp. nov., includes well-preserved craniomandibular and postcranial remains and represents the only diagnostic ornithischian specimen yet discovered in the Jurassic of South America so far. Derived features of its anatomy indicate that Manidens belongs to Heterodontosauridae, as the sister taxon of Heterodontosaurus and other South African heterodontosaurids. The presence of posterior dentary teeth with high crowns but lacking extensive wear facets in Manidens suggests that this form represents an intermediate stage in the development of the remarkable adaptations to herbivory described for Heterodontosaurus. The dentition of Manidens condorensis also has autapomorphies, such as asymmetrically arranged denticles in posterior teeth and a mesially projected denticle in the posteriormost teeth. At an estimated total length of 60-75 cm, Manidens furthermore confirms the small size of basal heterodontosaurids.Fil: Pol, Diego. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rauhut, Oliver Walter Mischa. Ludwig Maximilians Universitat; AlemaniaFil: Becerra, Marcos. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentin