Stig Walsh | National Museums Scotland (original) (raw)

Papers by Stig Walsh

Paläontologische Zeitschrift, 2008

Abstract: The first Cenozoic avian remains from Venezuela are described. The material comprises a... more Abstract: The first Cenozoic avian remains from Venezuela are described. The material comprises an associated right tarsometatarsus and tibiotarsus from the earliest Pliocene of the Codore Formation, northwestern Venezuela. The fossil-bearing horizon represents a deltaic ...

Systematics Association Special Volumes, 2007

There is, however, a practical problem in converting this sentiment into a coherent and productiv... more There is, however, a practical problem in converting this sentiment into a coherent and productive research programme; a problem that, we believe, lies at the heart of much of the criticisms traditionally made of morphological data.

Journal of anatomy, Jan 10, 2015

The evolution of the avian brain is of crucial importance to studies of the transition from non-a... more The evolution of the avian brain is of crucial importance to studies of the transition from non-avian dinosaurs to modern birds, but very few avian fossils provide information on brain morphological development during the Mesozoic. An isolated specimen from the Cenomanian of Melovatka in Russia was described by Kurochkin and others as a fossilized brain, designated the holotype of Cerebavis cenomanica Kurochkin and Saveliev and tentatively referred to Enantiornithes. We have previously highlighted that this specimen is an incomplete skull, rendering the diagnostic characters invalid and Cerebavis cenomanica a nomen dubium. We provide here a revised diagnosis of Cerebavis cenomanica based on osteological characters, and a reconstruction of the endocranial morphology (= brain shape) based on μCT investigation of the braincase. Absence of temporal fenestrae indicates an ornithurine affinity for Cerebavis. The brain of this taxon was clearly closer to that of modern birds than to Archae...

One approach to addressing long-standing concerns associated with the taxonomic impediment and th... more One approach to addressing long-standing concerns associated with the taxonomic impediment and the low reproducibility of taxonomic data is through development of automated species identification systems. Such systems can, in principal, be combined with either image-based, or image and text-based, taxonomic databases to add elements of expert-system functionality. Two generalized approaches are considered relevant in this context, morphometric systems based on some form of linear discriminant analysis (LDA), and artificial neural networks (ANN). In this investigation, digital images of 202 specimens representing seven modern planktonic foraminiferal species were used to compare and contrast these approaches in terms of system accuracy, generality, speed, and scalability. Results demonstrate that both approaches could yield systems whose models of morphological variation are over ninety per cent accurate for small datasets. Performance of distance and landmark-based LDA systems was enhanced substantially through application of least-squares superposition methods that normalize such data for variations in size and (in the case of landmark data) 2D orientation. Nevertheless, this approach is practically limited to the detailed analysis of small numbers of species by a variety of factors, including the complexity of basis morphologies, speed, and sample dependencies. An ANN variant based on the concept of a plastic self-organizing map combined with an n-tuple classifier was found to be marginally less accurate, but far more flexible, much faster, and robust to sample dependencies. Both approaches are considered valid within their own analytic domains, and both can benefit from various sorts of technology transfers. Based on these results (as well as others reviewed herein), it is concluded that fast and efficient, automated species-recognition systems can be constructed using available hardware and software technology and would be sufficiently accurate to be of great practical value notwithstanding the fact that the already impressive performance of current systems can be improved further with additional development.

The rapidly expanding interest in, and availability of, digital tomography data to visualize cast... more The rapidly expanding interest in, and availability of, digital tomography data to visualize casts of the vertebrate endocranial cavity housing the brain (endocasts) presents new opportunities and challenges to the field of comparative neuroanatomy. The opportunities are many, ranging from the relatively rapid acquisition of data to the unprecedented ability to integrate critically important fossil taxa. The challenges consist of navigating the logistical barriers that often separate a researcher from high-quality data and minimizing the amount of non- biological variation expressed in endocasts – variation that may confound meaningful and synthetic results. Our purpose here is to outline preferred approaches for acquiring digital tomographic data, converting those data to an endocast, and making those endocasts as meaningful as possible when considered in a comparative context. This review is intended to benefit those just getting started in the field but also serves to initiate further discussion between active endocast researchers regarding the best practices for advancing the discipline. Congruent with the theme of this volume, we draw our examples from birds and the highly encephalized non- avian dinosaurs that comprise closely related outgroups along their phylogenetic stem lineage.

Ferreira-Cardoso, S., Araújo, R., Castanhinha, R., Walsh, S., Martins, R.M.S., Martins, G.G. (201... more Ferreira-Cardoso, S., Araújo, R., Castanhinha, R., Walsh, S., Martins, R.M.S., Martins, G.G. (2014). The Floccular Complex: neuroanatomy as a tool to unveil paleoecology. Journal of Vertebrate Paleontology, Program and Abstracts, 2014, p.128.

This study evaluated the relative functions of pitch contours in infant-directed speech (IDS) by ... more This study evaluated the relative functions of pitch contours in infant-directed speech (IDS) by comparing it with adult- (ADS) and foreigner-directed speech (FDS). The shape of pitch contours derived from target words in speech samples was analysed using two novel algorithmic methods and a standard qualitative approach. Our findings indicate that IDS is very distinct from ADS and FDS, whilst

Zoological Journal of the Linnean Society, 2012

ABSTRACT

Despite a long history of research, relationships within fossil and extant Sphenisciformes remain... more Despite a long history of research, relationships within fossil and extant Sphenisciformes remain unclear. This is largely because most fossil species were described on the basis of either the tarsometatarsus or humerus. Neither of these elements is particularly phylogenetically informative, and the extent of intraspecific morphological variation also remains unknown. Herein we investigate a new approach -the use of artificial neural-net (ANN) technology -to determine whether either of these elements can be reliably used to identify extant species. The DAISY ANN system was able to recognise most species from either tarsometatarsal or humerus morphology, but its success rate improved when the species training sets were combined into generic groups, indicating the need for larger image libraries. Our preliminary results suggest that these elements can allow reliable identifications for most taxa, but that the tarsometatarsus is on the whole a better element for this purpose. These results also demonstrate the potential for artificial neural-net technology to address problems in avian taxonomy.

Palaeontology, 2002

A new monachine phocid pinniped assemblage from the north-central coast of Chile is described. Th... more A new monachine phocid pinniped assemblage from the north-central coast of Chile is described. The material was recovered from a marine bonebed of the Bahõ Âa Inglesa Formation which, based on macro-and microfossil evidence, is probably Late Miocene±Early Pliocene in age. At least two genera, Acrophoca and Piscophoca (both originally described from the Pisco Formation of Peru), are present. The Chilean material is signi®cantly different from that of the two described species from the Pisco Formation and probably represents new species, though these are not named pending description of new material reported from Peru. The postcrania are morphologically intermediate between the northern Phocini and southern Lobodontini. The Bahõ Âa Inglesa Formation pinniped assemblage represents the ®rst occurrence of fossil seals in Chile, and provides valuable information regarding the late Neogene radiation of monachines in the Southern Hemisphere. The occurrence of Acrophoca sp. in beds underlying a condensed Mio-Pliocene bonebed suggests that these strata are no older than Late Miocene.

Journal of Biogeography, 2005

... Stig Walsh works primarily on the systematics, evolution and distribution of Tertiary seabird... more ... Stig Walsh works primarily on the systematics, evolution and distribution of Tertiary seabirds in the Southern Hemisphere, focusing on Sphenisciformes and Pelecaniformes. Editor: Brett Riddle. Get PDF (356K). More content like this. ...

Acta Zoologica, 2009

Milner, A.C., Milner, A.R and Walsh, S.A. 2009. A new specimen of Baphetes from N ¥® any, Czech R... more Milner, A.C., Milner, A.R and Walsh, S.A. 2009. A new specimen of Baphetes from N ¥® any, Czech Republic and the intrinsic relationships of the Baphetidae.

In vertebrates, the endocranial surface records some degree of information about the size and som... more In vertebrates, the endocranial surface records some degree of information about the size and sometimes shape of the brain that it originally housed. These impressions represent palaeoneurology's basic data. Starting in the early 1800s, workers in palaeoneurology have attempted to determine how the brain of vertebrates has evolved through time. Early palaeoneurologists relied on the chance finds of damaged skulls or endocranial casts, and made qualitative assessments of the shape and size of the original brain in these fossils. Jerison introduced quantitative approaches to analysis of brain size, and this is still used today. Recent advances in noninvasive imaging have increased the number of taxa for which brain morphology is known, and it may now be possible to apply quantitative analysis even to the relative size of brain regions. If correlations between behaviour, sensory adaptation and relative brain region size are found using such approaches, palaeoneurology may be able to offer a line of evidence to complement inference of behaviour from skeletal adaptations in extinct taxa.