Morphometric variations between seasonal migrants of anadromous shad Tenualosa ilisha (Hamilton, 1822) from Hooghly Estuary, India

The morphometric variations between two seasonal migrants (winter and monsoon) of anadromous shad Tenualosa ilisha from Hooghly Estuary were evaluated and compared using geometric morphometrics (GM). Altogether, 128 fish samples of T. ilisha, comprising 64 samples each from winter and the monsoon season, were collected for two successive years (2017 and 2018) and 14 landmarks were digitised uniformly on each individual. Relative warps (RW), principal component analysis (PCA), canonical variate analysis (CVA) and discriminant function analysis (DFA) were used to determine shape variations between seasonal runs. The deformation grid of RW showed that monsoon specimens have a deeper body profile, whereas winter specimens have a slender body profile. The PCA showed low variance (40.45% for first two principal components) and high overlap among all the groups. The CVA-extracted Mahalanobis and Procrustes distances (3.473 and 0.032 respectively) between the two groups (winter and monsoon) were highly significant (P<0.0001). The DFA also separated two groups with high cross-validated classification rates (85.94 and 95.31% of winter and monsoon specimens respectively were correctly classified). Hence, the results of RW, CVA and DFA clearly indicate the existence of two morphologically distinct units of T. ilisha in Hooghly Estuary.

Evidence for prey preference partitioning in the middle Eocene high-diversity crocodylian assemblage of the Geiseltal-Fossillagerstätte, Germany utilizing skull shape analysis

The Geiseltal fossil collection from southern Sachsen-Anhalt Germany contains remarkably well-preserved fossils of middle Eocene age. These include several crocodylian skulls, representing at least four different genera with a fifth genus represented by two mandibular rami. As sites with this many crocodylian genera are unknown in modern ecosystems, it has been hypothesized that these crocodylians may have differences in habit as compared to living crocodylians. In order to test similarities between the Geiseltal crocodylians and extant species, an analysis was conducted using geometric morphometrics to quantify shape in crocodylian skulls of all living species (n= 218) and all well-preserved crocodylian skulls of the Geiseltal fauna (n= 28). A relative warps analysis was used to quantify and compare skull shape, revealingAllognathosuchusandBoverisuchusto be very distinct from each other as well as fromAsiatosuchusandDiplocynodon. Overlap in shape alone exists between someDiplocynodonand someAsiatosuchus, but there was significant difference in adult size. When compared with extant crocodylians, three Geiseltal genera occupied distinctly non-modern morphospace in the first two relative warps axes. Comparison of the diets of living crocodylians with similarly shaped skulls was used to reconstruct the prey preferences of the Geiseltal crocodylians, revealing differences in specialization. During the middle Eocene high global temperatures, partitioning of prey preference may have allowed this group to attain its higher than usual diversity, reducing the amount of direct competition.

Testing otolith morphology for measuring marine fish biodiversity

To check the suitability of otoliths for measuring biodiversity, the contour and shape of the sulcus acusticus of sagittal otoliths were described using geometric morphological analysis. Thirteen and fourteen points were used to define these structures respectively. Three current coastal fish assemblages of the north-western Mediterranean were selected for the present study. The results demonstrate that the relative warps generated in the geometric analysis explained both characteristics related to contour and the otolith sulcus. A comparative study with body fish shape using morphospaces and clusters revealed that otolith shape is a better variable for explaining the ecological structure of a fish assemblage. Moreover, three morphological indices (morphological richness (MR), morphological disparity and the morphogeometric index) were estimated from relative warps of otoliths and were compared with ecological, taxonomic, functional and morphological (from body shape) indices. MR increased with functional diversity and average taxonomic distinctness, reflecting the ecological and taxonomic character of otolith morphology. These findings suggest that otoliths could be a useful tool for studying the diversity of present and past fish assemblages.

The evolution of the fifth cervical vertebrae in Pelomedusoides (Testudines, Pleurodira): a preliminary analysis

Background. Crown-Pleurodira (i.e.: Cheloides and Pelomedusoides) possess a side-necked retraction mode with specialized cervical vertebrae (CV) anatomy. Moreover, there are distinctive ecological features among its lineages, as the convergent long neck in species of Chelidae and in the extinct pelomedusoid Araripemydidae. Also, the CV5-CV6 articulation is the major point of flexure in neck retraction and reflects a key point for the evolution of Pleurodira. Here we evaluated CV5 shape variation within some Pleurodira groups with emphasis on some Brazilian fossil species. Methods. We analyzed the fifth CV of eight species and 14 specimens comprising four pleurodiran clades (Chelidae, Araripemydidae, Bothremydidae and Podocnemididae) in order to assess the shape variation via geometric morphometry. All specimens were photographed in caudal view under the same protocol, and eight landmarks (LM) were picked at the left side of each vertebrae using TPSDig2. Data were Procrustes superimposed and a Relative Warps Analysis (RWA) was performed using TPSRelw v1.49. Results. RW1 and RW2 summarized 68.63% of the shape variance. The scatter of the specimens revealed distinctiveness between Podocnemidoidea (Podocnemididae+Bothremydidae) and Araripemys+Chelidae paraphyletic group. Such variation is due to (1) a medial contraction of the surface of the postzygapophysis, (2) a taller neural spine and (3) a more rounded vertebral condile towards Podocnemidoidea. Podocnemididae showed greater variation: a Podocnemis sextuberculata specimen (MZSP3218) is more alike to Cearachelys placidoi (Procrustes Distances, PD=0.17) than other podocnemidids and Bauruemys elegans resembles P. unifilis (PD=0.11). Also, other P. sextuberculata specimen (MZSP3217) is more alike to the Araripemys-Chelidae group. Discussion. Previous works have noticed the anatomical similarities between both longnecked chelids and A. barretoi, considering it as a convergence since they are from different clades. Our data showed the same pattern and, assuming the current phylogenetic relationships of Pleurodira, this might indicates similar feeding behavior between living Hydromedusa and Chelus and Araripemys. The Podocnemidoidea morphospace variation is consistent with the phylogeny, since C. placidoi is nested among Podocnemis spp., and this might indicate a more specialized CV5 for the former and a possible convergence with some Podocnemis species. Also, the resemblance of P. unifilis CV5 with B. elegans seems to indicate a morphotype similar to the podocnemidid ancestor for this living species. Despite our scanty sample, it shows a notable variation in Podocnemis spp. and at least two convergences among CV5 within Pleurodira. Further studies with additional sampling might shed light on a more complex evolution of CV specializations in side-necked turtles than previously assumed.

The evolution of the fifth cervical vertebrae in Pelomedusoides (Testudines, Pleurodira): a preliminary analysis

Background. Crown-Pleurodira (i.e.: Cheloides and Pelomedusoides) possess a side-necked retraction mode with specialized cervical vertebrae (CV) anatomy. Moreover, there are distinctive ecological features among its lineages, as the convergent long neck in species of Chelidae and in the extinct pelomedusoid Araripemydidae. Also, the CV5-CV6 articulation is the major point of flexure in neck retraction and reflects a key point for the evolution of Pleurodira. Here we evaluated CV5 shape variation within some Pleurodira groups with emphasis on some Brazilian fossil species. Methods. We analyzed the fifth CV of eight species and 14 specimens comprising four pleurodiran clades (Chelidae, Araripemydidae, Bothremydidae and Podocnemididae) in order to assess the shape variation via geometric morphometry. All specimens were photographed in caudal view under the same protocol, and eight landmarks (LM) were picked at the left side of each vertebrae using TPSDig2. Data were Procrustes superimposed and a Relative Warps Analysis (RWA) was performed using TPSRelw v1.49. Results. RW1 and RW2 summarized 68.63% of the shape variance. The scatter of the specimens revealed distinctiveness between Podocnemidoidea (Podocnemididae+Bothremydidae) and Araripemys+Chelidae paraphyletic group. Such variation is due to (1) a medial contraction of the surface of the postzygapophysis, (2) a taller neural spine and (3) a more rounded vertebral condile towards Podocnemidoidea. Podocnemididae showed greater variation: a Podocnemis sextuberculata specimen (MZSP3218) is more alike to Cearachelys placidoi (Procrustes Distances, PD=0.17) than other podocnemidids and Bauruemys elegans resembles P. unifilis (PD=0.11). Also, other P. sextuberculata specimen (MZSP3217) is more alike to the Araripemys-Chelidae group. Discussion. Previous works have noticed the anatomical similarities between both longnecked chelids and A. barretoi, considering it as a convergence since they are from different clades. Our data showed the same pattern and, assuming the current phylogenetic relationships of Pleurodira, this might indicates similar feeding behavior between living Hydromedusa and Chelus and Araripemys. The Podocnemidoidea morphospace variation is consistent with the phylogeny, since C. placidoi is nested among Podocnemis spp., and this might indicate a more specialized CV5 for the former and a possible convergence with some Podocnemis species. Also, the resemblance of P. unifilis CV5 with B. elegans seems to indicate a morphotype similar to the podocnemidid ancestor for this living species. Despite our scanty sample, it shows a notable variation in Podocnemis spp. and at least two convergences among CV5 within Pleurodira. Further studies with additional sampling might shed light on a more complex evolution of CV specializations in side-necked turtles than previously assumed.

AN APPLICATION OF THE RELATIVE WARPS ANALYSIS TO PROBLEMS IN HUMAN PALEONTOLOGY - WITH NOTES ON RAW DATA QUALITY

This study investigates the use of geometric morphometrics as well as methodological aspects specifically related to its application in paleoanthropology. Based on lateral photographs taken from a fossil sample of 58 specimens, a relative warps analysis was computed in order to assess the variation of cranial shape among various hominin groups. The fossil sample represents Middle and Late Pleistocene populations commonly assigned to H. erectus, H. neanderthalensis, archaic H. sapiens as well as anatomically modern H. sapiens. The preliminary results indicate that several fossil skulls considered as belonging to archaic H. sapiens have a distinct shape compared to modern humans. The results suggest that these hominins are not as closely related to modern humans as previously thought. Instead, their morphometric affinities suggest that they are as distinct from modern humans as are the Neandertals. Methodological aspects, such as raw data accuracy and the use of type 2 and 3 landmarks that are directly related to this type of quantitative analysis and that potentially affect their results, are discussed.

Long in the tooth: evolution of sabertooth cat cranial shape

Sabertooths exhibit one of the most extreme feeding adaptations seen in mammals. The functional consequences of accommodating extremely elongate upper canine teeth are severe, resulting in a well-documented suite of cranial modifications. We used geometric morphometric methods to study the evolution of overall shape in the skulls of extant and extinct feline and machairodontine felids, as well as extinct nimravids. Trends in skull evolution were evaluated by using relative warps analysis and tested for association with body size and canine tooth length. Primitive sabertooths from all lineages exhibit cranial shapes more similar to conical-toothed cats, despite the presence of moderately developed saberteeth. More-derived forms in both nimravids and felids diverge in skull morphospace to form two distinct sabertooth types (dirk-toothed and scimitar-toothed) that differ in canine shape. Skull shape in conical-toothed cats is strongly associated with body size, but not canine length. However, within each sabertooth lineage, skull shape is significantly correlated with canine length, suggesting that gape-related demands drove the evolution of sabertooth skull morphology.