Asymmetry of Early Paleozoic trilobites

Smith, Loren H.

doi:10.1111/j.1502-3931.1998.tb00496.x

Cited by 15 publications

(8 citation statements)

References 49 publications

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“…). Such fluctuating asymmetry was already demonstrated by Smith () on linear measurements on early Cambrian trilobites, suggesting that early trilobites possessed genetic or developmental mechanisms comparable to those of younger trilobites.…”

Section: Relation Between Development and Evolutionsupporting

confidence: 60%

Morphological disparity and developmental patterning: contribution of phacopid trilobites

Crônier

2013

Palaeontology

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In trilobites as in many others extinct organisms, our understanding of the mechanisms of evolution is based on morphological and ontogenetic features. Data from ontogenetic development are essential to provide an insight into the origins of evolutionary changes. In phacopid trilobites, detailed studies of ontogenetic series have been achieved using quantitative methods. A comparison of ontogenetic trajectories of closely related species has been conducted to understand how the both morphological disparity and developmental patterning of different ontogenetic stages were structured and to determine how the environmental or developmental con-straints influenced morphological changes in trilobites. Study of such morphological disparity in developmental evolution requires knowledge of morphological features and timing and rate of development among closely related species. At a macroevolutionary scale, such quantitative studies should allow us (1) to determine the impact of individual ontogenies on morphological diversification and (2) to identify the evolutionary patterns in Phacopidae during 100 Ma of existence.

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Section: Relation Between Development and Evolutionsupporting

confidence: 60%

Morphological disparity and developmental patterning: contribution of phacopid trilobites

Crônier

2013

Palaeontology

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“…Smith [295] studied asymmetry in nine genera of early Paleozoic (lower Cambrian through Silurian) trilobites (Trilobita: Arthropoda). The idea that the Cambrian Explosion was due, in part, to lax developmental constraints suggested that fluctuating asymmetry might decline through the Paleozoic.…”

Section: Fossil Materialsmentioning

confidence: 99%

Fluctuating Asymmetry: Methods, Theory, and Applications

et al. 2010

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Fluctuating asymmetry consists of random deviations from perfect symmetry in populations of organisms. It is a measure of developmental noise, which reflects a population's average state of adaptation and coadaptation. Moreover, it increases under both environmental and genetic stress, though responses are often inconsistent. Researchers base studies of fluctuating asymmetry upon deviations from bilateral, radial, rotational, dihedral, translational, helical, and fractal symmetries. Here, we review old and new methods of measuring fluctuating asymmetry, including measures of dispersion, landmark methods for shape asymmetry, and continuous symmetry measures. We also review the theory, developmental origins, and applications of fluctuating asymmetry, and attempt to explain conflicting results. In the process, we present examples from the literature, and from our own research at "Evolution Canyon" and elsewhere.

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“…There are few studies applying the FAlhomozygosity correlation to the fossil record (see review in Palmer 1986). However, several examples include the examination of FA in Pliocene horses (Van Valen 1962), the analysis of patterns of antisymmetry in Jurassic brachiopods (Fursich &Palmer 1984), the measurement of FA in lower Paleozoic trilobites (Smith 1998), and the study of dental anomalies in upper Eocene anthracoteriids related to inbreeding (Ducrocq et al 1995).…”

Section: Cranial Fluctuating Asymmetry: Implications For Developmentamentioning

confidence: 99%

Ecomorphological study of large canids from the lower Pleistocene of southeastern Spain

Palmqvist

Arribas

Martı́nez-Navarro³

1999

LET

102

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An ecomorphological analysis of the skeletal remains of large canids, Canis (Xenocyon) falconeri and Canis etruscus (Mammalia, Carnivora, Canidae), preserved in an assemblage of large mammals from the lower Pleistocene site at Venta Micena (Guadix-Baza Basin, Orce, Granada, southeastern Spain) is reported. Mean body mass of adult individuals was estimated to be around 10 kg for C. etruscus and approximately 28 kg for C. falconeri using multiple regression.A comparative study of tooth measurements in modern canids, using principal components and discriminant function analysis, infers quite different ecomorphological adaptations and feeding behavior for both fossil species. The craniodental morphology of C. falconeri is similar to that shown by extant hypercarnivorous canids whose diet include more than 70% of vertebrate meat, whereas C. etruscus shows a cranial morphology similar to those of modern omnivorous species, thus indicating a dietary niche in which vertebrate meat represented less than 70% of its diet, with other feeding resources making up the balance. These results suggest that there was a marked ecological segregation between both sympatric species of large canids. The find of a complete skull of C. falconeri showing bilateral asymmetry and marked dental anomalies could suggest high levels of genetic homozygosis in the population which inhabited this region during early Pleistocene times, possibly as a consequence of isolation and the low number of individuals. This may have subsequently led to the extinction of C. falconeri in the Western fringe of Europe. The survival of this pathological individual to adulthood indicates that this species may have developed cooperative behavior similar to that of modern African wild dogs. OCANIS (XENOCYON) FALCONER], CANIS ETRUSCUS, ecomorphology, principal component analysis, discriminant analysis, cranial fluctuating asymmetry, Venta Micena, lower Pleistocene. Paul Palmqvist [Paul.Palmqvist@uma.es],

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Asymmetry of Early Paleozoic trilobites

Cited by 15 publications

References 49 publications

Morphological disparity and developmental patterning: contribution of phacopid trilobites

Morphological disparity and developmental patterning: contribution of phacopid trilobites

Fluctuating Asymmetry: Methods, Theory, and Applications

Ecomorphological study of large canids from the lower Pleistocene of southeastern Spain

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