Avian Ancestors: A Review of the Phylogenetic Relationships of the Theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae

  title={Avian Ancestors: A Review of the Phylogenetic Relationships of the Theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae},
  author={Federico L. Agnolin and Fernando E Novas},
  journal={Avian Ancestors},
The phylogenetic affinities and morphological peculiarities of the bird-like dinosaur Borogovia gracilicrus from the Upper Cretaceous of Mongolia
The lack of a falciform ungual, and the distinctive morphology of the second toe in B. gracilicrus are interpreted as a derived specialization among Troodontidae and not as retention of the plesiomorphic condition of non-paravian theropods.
Differential locomotor and predatory strategies of Gondwanan and derived Laurasian dromaeosaurids (Dinosauria, Theropoda, Paraves): Inferences from morphometric and comparative anatomical studies
The distinctive morphological evolutionary pathways of these two dromaeosaurid clades seem to have been influenced by the particular locomotor and predatory specializations that characterized each of these lineages.
Osteology of Unenlagia comahuensis (Theropoda, Paraves, Unenlagiidae) from the Late Cretaceous of Patagonia
Detailed analysis of Unenlagia anatomy resulted in the recognition of one possible additional Unenlagiidae synapomorphy (i.e., the presence of cup‐like iliac articulation on ischium), lending support to the interpretation that unen lagiids are stem‐Avialae.
New troodontid theropod specimen from Inner Mongolia, China clarifies phylogenetic relationships of later‐diverging small‐bodied troodontids and paravian body size evolution
A new troodontid (LH PV39) recovered from the Upper Cretaceous Wulansuhai Formation, Inner Mongolia, China, is described, highlighting the dorsoventrally compressed sacral centra. The completely
Comments on the Morphology of Basal Paravian Shoulder Girdle: New Data Based on Unenlagiid Theropods and Paleognath Birds
The present paper aims to review some important topics on pectoral girdle anatomy related to flight origins and test whether Ostrom’s ideas still remain valid under this new context, based on available phylogenetic and anatomical frameworks.
Feather Evolution in Pennaraptora
The origin and early evolution of complex feathers and flight abilities in paravian theropods were not linear processes, but more complex than previously thought.
Assesment and interpretation of negative forelimb allometry in the evolution of non-avian Theropoda
It is proposed that proportionally longer arms of juveniles became adult traits in the small-sized and paedomorphic Aves, which suggests negative allometry of the forelimb in the ontogeny of most non-avian theropods.
A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight
All parsimonious results support the hypothesis that each early paravian clade was plesiomorphically flightless, raising the possibility that avian flight originated as late as the Late Jurassic or Early Cretaceous.
Paravian Phylogeny and the Dinosaur-Bird Transition: An Overview
It is concluded that troodontid affinities of anchiornithines, and dromaeosaurids affinITIES of microraptorians and unenlagiids are dismissed in favor of sister group relationships with Avialae, and main phylogenetic hypotheses that compete some topics about the non-avian dinosaur-bird transition are analyzed.


Anatomy of Mahakala omnogovae (Theropoda: Dromaeosauridae), Tögrögiin Shiree, Mongolia
Several interesting features of Mahakala omnogovae have implications for deinonychosaurian and avialan character evolution and for understanding patterns of size variation and size change within paravian theropods.
The tenth skeletal specimen of Archaeopteryx
The tenth skeletal specimen of the Upper Jurassic Archaeopterygidae is described and demonstrates the presence of a hyperextendible second toe in archaeopteryx, supporting previous assumptions that Archaeoperyx was only facultatively arboreal.
The theropod ancestry of birds: new evidence from the late cretaceous of madagascar
Rahona has a robust, hyperextendible second digit on the hind foot that terminates in a sicklelike claw, a unique characteristic of the theropod groups Troodontidae and Dromaeosauridae.
An Archaeopteryx-like theropod from China and the origin of Avialae
It is demonstrated that many features formerly regarded as being diagnostic of Avialae, including long and robust forelimbs, actually characterize the more inclusive group Paraves (composed of the avialans and the deinonychosaurs), which challenges the centrality of Archaeopteryx in the transition to birds.
The Evolution of the Antorbital Cavity of Archosaurs: A Study in Soft-Tissue Reconstruction in the Fossil Record with an Analysis of the Function of Pneumaticity
Resolution of the antorbital cavity is correctly viewed as a “soft-tissue problem,” and is addressed within the context of the extant phylogenetic bracket (EPB) approach for reconstructing the unpreserved features of fossil organisms.
A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight
Change in theropod body size leading to flight's origin was not unidirectional, and the two dinosaurian lineages most closely related to birds, dromaeosaurids and troodontids, underwent four independent events of gigantism, and in some lineages size increased by nearly three orders of magnitude.
A short-armed dromaeosaurid from the Jehol Group of China with implications for early dromaeosaurid evolution
Recent discoveries of basal dromaeosaurids from the Early Cretaceous Jiufotang and Yixian formations of Liaoning, China, add significant new information about the transition from non-avian dinosaurs
Four-winged dinosaurs from China
New evidence is provided suggesting that basal dromaeosaurid dinosaurs were four-winged animals and probably could glide, representing an intermediate stage towards the active, flapping-flight stage of proavians.
A new feathered dinosaur fossil that fills a morphological gap in avian origin
  • 2008