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690 results for “Geometric morphometrics”
Data from: Geometric morphometric analysis applied to theropod tracks from the lower Cretaceous (Berriasian) of Spain
Geometric morphometric methods applied to theropod tracks from the Huérteles Formation (Berriasian, Spain) are here shown to be invaluable for drawing comparisons between theropod tracks with different preservation modes (true tracks, shallow undertracks and natural casts) or differing in the preservation of anatomical features (e.g. digital pads). Principal components analysis and thin-plate spline methods can quantitatively distinguish between the broad groups of tracks in a sample and establish the main differences between them. These methods offer a promising approach for estimating ichnodiversity, achieved by evaluating just the morphology of the tracks independent of other factors such as size. The theropod tracks of the Huérteles Formation can be classified into two broad groups: minute-to-medium-sized gracile theropod tracks (Kalohipus bretunensis) and medium-to-large-sized robust theropod tracks (Iberosauripus). The presence of a third group of more gracile medium-to-large-sized theropod tracks (Megalosauripus) cannot be proven with certainty on the basis of the current data. These results indicate that the theropod ichnodiversity of the Huérteles Formation is probably lower than that estimated by means of conventional methods alone (e.g. qualitative description of the tracks) and that many of the described theropod morphotypes may represent extramorphological or ontogenetic variations of other morphotypes.
Data from: Geometric morphometric analyses of worn cheek teeth help identify extant and extinct gophers (Rodentia: Geomyidae)
Studies of the biostratigraphy and palaeoecology of fossil vertebrate assemblages require large samples of accurately identified specimens. Such analyses can be hampered by the inability to assign isolated and worn remains to specific taxa. Entoptychine gophers are a diverse group of burrowing rodents found in Oligo-Miocene deposits of the western United States. In both entoptychines and their extant relatives the geomyines, diagnostic characters of the occlusal surface of the teeth are modified with wear, making difficult the identification of many isolated fossil teeth. We use geometric morphometrics to test the hypothesis that tooth shape informs taxonomic affinities and expected levels of morphological variation across gopher taxa. We also incorporate data from microcomputer tomography to investigate changes in occlusal surface shape through wear within individuals. Our analyses demonstrate the usefulness of our approach in identifying extant geomyines to the genus, subgenus and species levels, and fossil entoptychines to the genus and, in some cases, the species level. Our results cast doubt on the validity of some species within Entoptychus and suggest future revisions to entoptychine taxonomy. The amounts of morphological divergence observed among fossil and extant genera are similar. Fossil species do not differ greatly from extant ones in that regard either. Further work evaluating the morphological variation within and across entoptychine species, including unworn teeth and osteological material, will allow revised analyses of the biostratigraphy and palaeoecology of important Oligo-Miocene mammalian assemblages of the western United States and help to infer the phylogenetic relationships and evolution of gophers.
Data from: Taxonomic revision of genus Ablattaria Reitter (Coleoptera, Silphidae) employing geometric morphometrics
The genus Ablattaria Reitter, 1884 (Coleoptera: Silphidae: Silphinae) is revised. Four taxa are recognized as valid species: Ablattaria arenaria (Kraatz, 1876), A. cribrata (Ménétries, 1832), A. laevigata (Fabricius, 1775) and A. subtriangula Reitter, 1905. Ablattaria laevigata var. meridionalis Ganglbauer, 1899 is newly treated as a junior subjective synonym of A. laevigata. Lectotypes are designated for Phosphuga arenaria Kraatz, 1876, Ablattaria arenaria var. punctigera Reitter, 1884, Ablattaria arenaria var. alleoni Portevin, 1926, Silpha cribrata Ménétries, 1832, Silpha laevigata Fabricius, 1775, Silpha gibba Brullé, 1832, Ablattaria gibba var. costulata Portevin, 1926, Ablattaria gibba var. distinguenda Portevin, 1926, Ablattaria gibba var. punctata Portevin, 1926 and Ablattaria subtriangula Reitter, 1905. The distribution of all taxa is mapped, based on material examined. Geometric morphometric methods were used to evaluate shape variability in Ablattaria. Results indicated sexual dimorphism in all species. Shape inconsistency was found between the sexes of all taxa when tested independently. The first two relative warp axes indicated 65.17% shape variation in males and 65.72% in females. Canonical variate analysis separated the taxa studied. There was minimal overlap between some groups in both sexes. Differences in body shape between populations of A. laevigata from Central Europe, Italy and Greece + Turkey were also examined. Relative warps implied 58.01% shape variability on both axes in males and 64.78% in females. CVA revealed noticeable overlaps between the groups, although the Italian population demonstrated a higher separation in both sexes.
Data from: Taxonomic and evolutionary pattern revisions resulting from geometric morphometric analysis of Pennsylvanian Neognathodus conodonts, Illinois Basin
Conodont fossils are highly valuable for Paleozoic biostratigraphy and for interpreting evolutionary change, but identifying and describing conodont morphologies, and characterizing gradual shape variation remain challenging. We used geometric morphometrics (GM) to conduct the first landmark-based morphometric analysis of the biostratigraphically useful conodont genus Neognathodus. Our objective is to assess whether previously defined morphotype groups are reliably distinct from one another. As such, we reevaluate patterns of morphologic change in Neognathodus P1elements, perform maximum likelihood tests of evolutionary modes, and construct novel, GM-based biozonations through a Desmoinesian (Middle Pennsylvanian) section in the Illinois Basin. Our GM results record the entire spectrum of shape variability among Neognathodus morphotypes thus alleviating the problem of documenting and classifying gradual morphologic transitions between morphotypes. Statistically distinct GM groups support previously established classifications of N. bassleri, N. bothrops, and N. roundyi. Statistically indistinct pairs of GM groups do not support literature designations of N. medadultimus and N. medexultimus, and N. dilatus and N. metanodosus, and we synonymize each pair. Maximum likelihood tests of evolutionary modes provide the first statistical assessment of Neognathodus evolutionary models in the Desmoinesian. The most likely evolutionary models are an unbiased random walk or a general random walk. We name four distinct biozones through the Desmoinesian using GM results and these align with previous biozonation structure based on the Neognathodus Index (NI) illustrating that Neognathodus-based biostratigraphic correlations would not change between GM or NI methods. The structural similarity between both biozonations showcases that determining GM-based biozones is not redundant, as this comparison validates using landmark-based GM work to construct viable biozonations for subsequent stratigraphic correlations. Although this study is limited to the Illinois Basin, our quantitative methodology can be broadly applied to additional genera to test taxonomic designations, interpret statistically-robust evolutionary patterns, and construct valid biozones for this significant chordate group.
Data from: Dealing with allometry in linear and geometric morphometrics: a taxonomic case study in the Leporinus cylindriformis group (Characiformes: Anostomidae) with description of a new species from Suriname
To achieve maximum efficacy, taxonomic studies that seek to distinguish amongst species must first account for allometric shape variation within species. Two recently developed software packages (SMATR and MorphoJ) offer regression-based allometric approaches that are notable for their statistical power and ease of use and that may prove highly useful to taxonomists working with linear or geometric morphometric data. We investigate species delimitation of the slender-bodied fishes in the Leporinus cylindriformis group using these programs and demonstrate the utility of the allometric corrections that they provide. Without allometric correction, many pairs of species are difficult to distinguish on the basis of morphometrics, but once regressions are used to account for marked allometric variation within species, most of the recognized species in this group can be readily distinguished with linear or geometric morphometrics, particularly using variation in the depth of the body. Both approaches returned congruent patterns of separation amongst putative species, but the geometric approach in MorphoJ distinguished amongst four more pairs of species than did the linear approach in SMATR and appears to provide slightly more statistical power. Based on distinctive morphometrics, meristics, and coloration, a highly elongate species of Leporinus from the Suriname, Corantijn, and Coppename rivers of Suriname is described herein as a new species, Leporinus apollo sp. nov. The unique L. cylindriformis holotype from Porto de Moz, Brazil differs in morphology, meristics, and pigmentation from specimens commonly referred to that species from the main basin of the Amazon; the latter specimens may represent an additional undescribed species. The L. cylindriformis holotype itself may represent a rare species or a specimen collected at the edge of its native range. Measurements of the holotype and paratype of Leporinus niceforoi, which were collected in the Amazonian slope of Colombia, differ substantially from similarly pigmented and putatively conspecific specimens from Amazonian portions of Ecuador and Peru. Recently collected specimens from Colombia are needed to determine whether the observed morphometric variation encompassed by the current concept of L. niceforoi indicates a morphocline within a single species, suggests the presence of multiple cryptic species, or results from shrinkage of the types. In all these cases, linear or geometric morphometric data can reliably differentiate amongst species, but only after one accounts for allometric shape variation. The new SMATR and MorphoJ software packages both offer easy and effective approaches to such allometrically informed taxonomy, and may prove useful to any systematist working on taxa that change shape as they grow.
FIGURE 5 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 5. Relative deformations grids show the variation in the mean shape of the second abdominal segment for (a) females and (b) males.
FIGURE 4 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 4. Scatter plot of first versus second principal component axes for the total variation of the second abdominal pleura shape for females and males in Neocaridina davidi.
FIGURE 1 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 1. Location of landmarks and semilandmarks on each anatomic structure in Neocaridina davidi. (a) carapace; (b) second abdominal pleura; left side, lateral view.
FIGURE 3 in Geometric morphometrics uncovers a new species of ponyfish (Teleostei: Leiognathidae: Equulites), with comments on the taxonomic status of Equula berbis Valenciennes
FIGURE 3. Landmarks (1) rostral tip of premaxilla, (2) posterior end of nuchal spine, (3) anterior insertion of dorsal fin, (4) posterior insertion of dorsal fin, (5) dorsal insertion of caudal fin, (6) midpoint of caudal border of hypural plate, (7) ventral insertion of caudal fin, (8) posterior insertion of anal fin, (9) anterior insertion of anal fin, (10) dorsal base of pelvic fin, (11) ventral end of lower jaw articulation, (12) posterior end of maxilla, (13) anterior margin through midline of eye, (14) posterior margin through midline of eye, (15) dorsal end of opercle, (16) dorsal base of pectoral fin. Base figure is modified from Nelson (2006).
FIGURE 5 in Geometric morphometrics uncovers a new species of ponyfish (Teleostei: Leiognathidae: Equulites), with comments on the taxonomic status of Equula berbis Valenciennes
FIGURE 5. Holotype of Equulites absconditus (AMNH 249306; 74.0 mm SL, adult male) showing the distinct sexspecific translucent flank patch that concentrates light on the body during photic display.
FIGURE 4 in Geometric morphometrics uncovers a new species of ponyfish (Teleostei: Leiognathidae: Equulites), with comments on the taxonomic status of Equula berbis Valenciennes
FIGURE 4. Canonical variates analysis showing two distinct shape groups along CV 1 individuals and the holotype.
FIGURE 2 in Geometric morphometrics uncovers a new species of ponyfish (Teleostei: Leiognathidae: Equulites), with comments on the taxonomic status of Equula berbis Valenciennes
FIGURE 2. Specimens of Group A morphotype (A—Western Indian Ocean) and Group B morphotype (B—Eastern Indian Ocean)
FIGURE 3 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 3. Relative deformations grids illustrating the variation in the mean shape of the carapace for (a) females and (b) males.
FIGURE 2 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 2. Scatter plot of first versus second principal component axes for the total variation of the carapace shape for females, juvenile females and males of Neocaridina davidi.
Figure 4 in Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)
Figure 4. ANOVA of male length and width trait measurements by mountain range and subspecies: A, male head width; B, male body length; C, male leg length; D, male head length; E, female head width; F, female body length; G, female leg length; H, female head length. Black string, median; open box, first interquartile; bar, second interquartile.
Figure 3 in Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)
Figure 3. Maximum-likelihood tree of Scaphinotus petersi populations from combined 28S rDNA, COI, and ND1 + mtRNA data. The out-group, Sphaeroderus lecontei, is removed to show greater detail. Specimen numbers are removed, but the subspecies and mountain range from which they were collected is indicated. Specimens from all subspecies in Table 1 are represented in the molecular phylogeny. Support for major branches is indicated by Bayesian posterior probability/ maximum likelihood bootstrap values. *Bayesian posterior probability greater than 95%. Scale bar units are substitutions per site.
Figure 1. A in Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)
Figure 1. A, study location; distribution area of Scaphinotus petersi is circled. Habitats above 1830 m a.s.l. are shown in black, and habitats between 1500 and 1830 m a.s.l. are shown in grey. B, shaded relief map of study area. Black dots denote the sampling localities of S. petersi used in this study (see Table 1), abbreviated as follows: C, Chiricahua Mountains; H, Huachuca Mountains; P, Pinal Mountains; PN, Pinaleño Mountains; R, Rincon Mountains; SA, Sierra Ancha Mountains; SC, Santa Catalina Mountains; SR, Santa Rita Mountains; WM, White Mountains. Figure modified from Ober et al. (2011).
Figure 2. A in Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)
Figure 2. A, head shape landmarks on female Scaphinotus petersi biedermani from Rincon Mountains. Pronotum shape landmarks: (B) Scaphinotus petersi kathleenae male from Santa Rita Mountains; (C) Scaphinotus petersi biedermani female from Rincon Mountains.
Figure 5 in Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)
Figure 5. Scatter plots of canonical variate analyses (CVA) for pronotum shape: CV1 versus CV2 of (A) female and (B) male pronota. Legend indicates the mountain ranges from where the specimen was collected. For both plots, shape deformation of pronotum is shown for the extreme points of each axis. A dotted line separates populations in clade A of the phylogenetic tree from those in clade B.
Figure 2 in Using geometric morphometrics for integrative taxonomy: an examination of head shapes of milksnakes (genus Lampropeltis)
Figure 2. The eleven landmarks used for geometric morphometric analyses (A) and the Procrustes superimpostition consensus of the landmarks averaged across all specimens (B).
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