Matthew Baron

University of Cambridge | Cam · Department of Earth Sciences

The systematic position of the unusual Late Jurassic dinosaur Chilesaurus diegosaurezi remains an area of real uncertainty. Originally thought to be an unusual theropod, Chilesaurus has, since its first discovery, been suggested to either be a sauropodomorph dinosaur, an early diverging, ‘transitional’ ornithischian, or a more ‘derived’ neornithisc...

The origin and evolutionary relationships of ornithischian dinosaurs are topics that have undergone a series of substantial revisions. At present there are several competing hypotheses concerning the relationship between Ornithischia and the other principal clades of Dinosauria. Some hypotheses have posited a tree topology within Dinosauria that im...

Our understanding of the pterosaurs' place within the reptilian lineage has had a long and complex history. The unusual morphology of pterosaurs, which is inextricably linked to their habit of powered flight, has generated numerous proposals over the years regarding their exact origin and systematic position. Though it was concluded early on in pte...

The early gnathostome genus Mesacanthus is well represented in both Lower Old Red Sandstone and Middle Old Red Sandstone assemblages of northern and central Scotland. This ‘acanthodian’ taxon is currently thought to comprise two valid species: M. mitchelli and M. pusillus. Although the whereabouts of the holotype of M. mitchelli (NHMUK PV P560) is...

The pterosaurs first appear in the fossil record in the middle of the Late Triassic. Their earliest representatives are known from Northern Hemisphere localities but, by the end of the Jurassic Period, this clade of flying reptiles achieved a global distribution, as well as high levels of diversity and disparity. Our understanding of early pterosau...

The origin and early evolutionary history of the dinosaurs is a topic that has recently gone through a period of renewed interest and academic debate. For 130 years, one way of classifying the various dinosaur subgroups persisted as the accepted model, with increasing levels of research in the past quarter-century also providing evidence for the hy...

Tail elongation is a trait common to many sauropod dinosaurs. In certain members of Diplodocidae, for example, the total caudal vertebrae count is as high as 70 to 80 bones, making a total estimated tail length for mature animals that is in excess of 10 metres. A number of competing hypotheses have been suggested to explain the function of this ‘hy...

A comprehensive analysis of early dinosaur relationships raised the possibility that the group may have originated in Laurasia (Northern Hemisphere), rather than Gondwana (Southern Hemisphere) as often thought. However, that study focused solely on morphology and phylogenetic relationships and did not quantitatively evaluate this issue. Here, we in...

My first conference poster on the taxonomic questions surrounding the Devonian acanthodian fish Mesacanthus. Key words: Morphometrics; Orcadian Basin; Devonian; Taxonomy; Anatomy; Fish; Scotland;

Ornithischian dinosaurs were important and often dominant members of Cretaceous ecosystems around the world. However, the early evolution of this interesting and diverse clade during the Late Triassic-Early Jurassic remains poorly understood. Lesothosaurus diagnosti-cus from the Upper Elliot Formation of South Africa and Lesotho (?Hettangian-Sinemu...

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Taxa

Anatomical Characters

In our work, we reanalysed phylogenetic datasets for dinosaurs. This included a dataset assembled by Langer et al. [1] which was further modified by Baron et al. [2]. The dataset analysed in our paper incorporated the modifications made by Baron et al. [2] to the coding of multiple characters in Pisanosaurus, which was not made explicit in our manu...

The holotype specimen of the Late Triassic dinosauriform Caseosaurus crosbyensis is redescribed and evaluated phylogenetically for the first time, providing new anatomical information and data on the earliest dinosaurs and their evolution within the dinosauromorph lineage. Historically, Caseosaurus crosbyensis has been considered to represent an ea...

Assessments of dinosaur macroevolution at any given time can be biased by the historical publication record. Recent studies have analysed patterns in dinosaur diversity that are based on secular variations in the numbers of published taxa. Many of these have employed a range of approaches that account for changes in the shape of the taxonomic abund...

Assessments of dinosaur macroevolution at any given time can be biased by the historical publication record. Recent studies have analysed patterns in dinosaur diversity that are based on secular variations in the numbers of published taxa. Many of these have employed a range of approaches that account for changes in the shape of the taxonomic abund...

For 130 years dinosaurs have been divided into two distinct clades – Ornithischia and Saurischia. This dissertation looks at the earliest evolution of the clade Dinosauria by focusing upon the interrelationships of the major subsidiary clades within it. It does this following examination, comparison and description of early dinosaur material, and b...

Two recent studies have independently recovered Pisanosaurus mertii – long thought to represent the oldest known member of Ornithischia – within Silesauridae. These finds are expanded upon here, as are the implications of this hypothesis. Based upon these finds, it now appears that Ornithischia was absent in the Triassic Period entirely, which cons...

A recent study of early dinosaur evolution using equal-weights parsimony recovered a scheme of dinosaur interrelationships and classification that differed from historical consensus in a single, but significant, respect; Ornithischia and Saurischia were not recovered as monophyletic sister-taxa, but rather Ornithischia and Theropoda formed a novel...

The enigmatic dinosaur taxon Chilesaurus diegosuarezi was originally described as a tetanuran theropod, but this species possesses a highly unusual combination of features that could provide evidence of alternative phylogenetic positions within the clade. In order to test the relationships of Chilesaurus, we added it to a new dataset of early dinos...

For 130 years, dinosaurs have been divided into two distinct clades—Ornithischia and Saurischia. Here we present a hypothesis for the phylogenetic relationships of the major dinosaurian groups that challenges the current consensus concerning early dinosaur evolution and highlights problematic aspects of current cladistic definitions. Our study has...

Lesothosaurus diagnosticus from the upper Elliot Formation of South Africa and Lesotho (?Hettangian-Sinemurian) is an important early representative of Ornithischia. In previous studies it has been recovered in several positions on the ornithischian tree including as the earliest known member of Thyreophora, the earliest known member of Neornithisc...

We describe new specimens of the basal ornithischian dinosaur Lesothosaurus diagnosticus Galton, 1978 collected from a bonebed in the Fouriesburg district of the Free State, South Africa. The material was collected from the upper Elliot Formation (Early Jurassic) and represents the remains of at least three individuals. These individuals are larger...

Mesacanthus is a common and speciose genus of acanthodian fish from Lower Old Red Sandstone and Middle Old Red Sandstone assemblages (representing the Lower Devonian and Middle Devonian respectively) and is well represented in many palaeoichthyology collections in the UK. Based upon descriptions given during the 19th century, specimens of the genus...