Returning to the roots: resolution, reproducibility, and robusticity in the phylogenetic inference of Dissorophidae (Amphibia: Temnospondyli)

The phylogenetic relationships of most Paleozoic tetrapod clades remain poorly resolved, which is variably attributed to a lack of study, the limitations of inference from phenotypic data, and constant revision of best practices. While refinement of phylogenetic methods continues to be important, any phylogenetic analysis is inherently constrained by the underlying dataset that it analyzes. Therefore, it becomes equally important to assess the accuracy of these datasets, especially when a select few are repeatedly propagated. While repeat analyses of these datasets may appear to constitute a working consensus, they are not in fact independent, and it becomes especially important to evaluate the accuracy of these datasets in order to assess whether a seeming consensus is robust. Here I address the phylogeny of the Dissorophidae, a speciose clade of Paleozoic temnospondyls. This group is an ideal case study among temnospondyls for exploring phylogenetic methods and datasets because it has been extensively studied (eight phylogenetic studies to date) but with most (six studies) using a single matrix that has been propagated with very little modification. In spite of the conserved nature of the matrix, dissorophid studies have produced anything but a conserved topology. Therefore, I analyzed an independently designed matrix, which recovered less resolution and some disparate nodes compared to previous studies. In order to reconcile these differences, I carefully examined previous matrices and analyses. While some differences are a matter of personal preference (e.g., analytical software), others relate to discrepancies with respect to what are currently considered as best practices. The most concerning discovery was the identification of pervasive dubious scorings that extend back to the origins of the widely propagated matrix. These include scores for skeletal features that are entirely unknown in a given taxon (e.g., postcrania in Cacops woehri) and characters for which there appear to be unstated working assumptions to scoring that are incompatible with the character definitions (e.g., scoring of taxa with incomplete skulls for characters based on skull length). Correction of these scores and other pervasive errors recovered a distinctly less resolved topology than previous studies, more in agreement with my own matrix. This suggests that previous analyses may have been compromised, and that the only real consensus of dissorophid phylogeny is the lack of one.

Sizing Up Swords: Correlated Evolution of Antlers and Tusks in Ungulates

Most sexual weapons in sexual combat and visual displays of dominance (e.g., antlers, horns) show positively allometry with body size for both growth during development and evolution across species, but allometry in species with more than one sexual weapon is unstudied. We examined the allometric relationships between body size and tusks (pure combat weapons) and/or antlers (both a visual signal and combat weapon) from forty-three artiodactyl species including the muntjaks (Muntiacinae), which uniquely have both antlers and tusks. We found that in Muntiacinae antler length scales positively allometrically with skull length, whereas tusk size scales isometrically suggesting greater energy investment in antlers as signals over tusks as combative weapons when both are present. Interspecifically, we found that species who possess only one weapon (either solely tusked or solely antlered) scaled positively allometrically with body mass, and the latter relationship levels off at larger body sizes. In our tusk analysis, when we included Muntiacinae species the positive allometric trend was not conserved resulting in an isometric relationship suggesting the possession of antlers negatively affect the energy investment in tusks as weapons. Overall, our findings show that species that possess dual weapons unproportionally invest energy in the development and maintenance of their multiple weapons.

Digital 3D models of theropods for approaching body-mass distribution and volume

The aim of this work is to obtain diverse morphometric data from digitized 3D models of scientifically accurate palaeoreconstructions of theropods from eight representative families. The analysed polyvinyl chloride (PVC) models belong to the genera Coelophysis, Dilophosaurus, Ceratosaurus, Allosaurus, Baryonyx, Carnotaurus, Giganotosaurus, and Tyrannosaurus. The scanned 3D models were scaled considering different body-size estimations of the literature. The 3D analysis of these genera provides information on the skull length and body length that allows for recognition of major evolutionary trends. The skull length/body length in the studied genera increases according with the size of the body from the smallest Coelophysis with a ratio of 0.093 to ratios of 0.119–0.120 for Tyrannosaurus and Giganotosaurus, the largest study theropods. The study of photogrammetric 3D models also provides morphometric information that cannot be obtained from the study of bones alone, but knowing that all reconstructions begin from the fossil bones, such as the surface/volume ratio (S/V). For the studied theropod genera surface/volume ratio ranges from 35.21 for Coelophysis to 5.55 for Tyrannosaurus. This parameter, closely related to the heat dissipation, help in the characterization of the metabolism of extinct taxa. Accordingly, slender primitive forms of the Early Jurassic (i.e. Coelophysis and Dilophosaurus) had relatively smaller skulls and higher mass-specific metabolic rates than the robust large theropods of the Cretaceous (i.e. Giganotosaurus and Tyrannosaurus). This work presents a technique that, when applied to proper dinosaur models, provides extent and accurate data that may help in diverse study areas within the dinosaur palaeontology and palaeobiology.

Endothelin B Receptor Mutant Exhibits Craniofacial Dysmorphology Resembling Domestication Syndrome

Background: ETB-/- mutation is a major cause of HSCR, a neurocristopathy known for its enteric nervous system failure. Other than regulating ENCC migration, ETB mediates ET-1 clearance. Consequently, ETB may indirectly affect ET-1/ETA signaling, which controls CNCC migration and craniofacial development. Interestingly, it was hypothesized that “domestication syndrome” arise from changes in neural crest determining genes, including ETA and ETB. While ETA-/- animals are known to suffer severe dysmorphology resembling CATCH22 syndrome, we hypothesize that sl/sl rat, an ETB-/- HSCR model animal, may exhibit subtle craniofacial changes through indirect control. These features may share resemblance to those of domestication syndrome. Methods: Ten rat pups with an average age of 88 hours were anaesthetized with 5% isoflurane and culled via exsanguination. Tail tips were removed for genotyping. Head tissue were stained in 1.5% iodine for two weeks prior to micro-CT scanning. In vivo micro-CT scanning of cranial specimen was performed followed by ex vivo micro-CT scanning of 2 samples for image quality control. 3D visualization and analyses were performed using open-source program, Drishti. Cephalometric measurements were made based on selected craniofacial landmarks. Comparisons were made between sl/sl rats and the control group, which consisted of wild-type and heterozygotes. Results: Subtle reductions in facial measurements were seen in sl/sl rats when compared with the control group, ranging from 1.4% to 15%. These changes were observed in cranial, maxillary and mandibular parameters: total skull length, nasal length, nasal width, nasal cavity width, interorbital width, interlens distance, inner and outer canthal distance, maximal skull height, cranial length, intracranial length and width, interorbital width, and interzygomatic width. Consistently, craniofacial ratio indices showed sl/sl rat has a flatter cranium (skull height/skull length: 0.393 vs 0.413) and a shorter but broader nose (nasal-width/nasal-length: 0.794 vs 0.874). Additionally, subtle dystopia canthorum may be presented in sl/sl rat based on increased W index. While there was no discrepancy in dental number and morphology between the control and sl/sl groups, dimensional difference was detected. Conclusions: This study demonstrated subtle craniofacial changes are presented in ETB-/- HSCR model, supporting the idea that ETB regulates CNCC migration. The findings also implicate HSCR patient may have predisposing risks for conditions such as obstructive sleep apnea, cleft palate, or dental malocclusion. Lastly, these changes share resemblance with described domestication syndrome, supporting NCC-determining gene, ETB, may play a role in the formation of domestication.

Morphometric characteristics of skull and face parameters in fetuses and newborns

Modern science has a significant number of diagnostic methods: craniological, anatomical, ultrasound, radiological. The development of new research methods, such as ultrasound and X-ray methods (magnetic resonance imaging), forms the concept of ultrasound and X-ray norms at different stages of human development. Now it is important to study the anatomical variability of people, morphometric characteristics, relationships of organs, anatomical structures, their parts at all stages of human development. The purpose of the work is to establish normative morphometric parameters of the skull and face in fetuses and newborns, followed by construction of mathematical models. The study was performed on 57 preparations of human fetuses 4-10 months and 7 newborns using adequate anatomical methods: macropreparation, topographic anatomical sections, computed tomography, craniometry. The main parameters of the facial and cerebral skull were measured with the help of a centimeter tape, a thick, sliding compass and a caliper. Statistical analysis of the obtained data was performed using a licensed program RStudio. It is established that according to the graphs of the average values of the parameters of the skull and face, there are two periods of accelerated and two periods of slow development. For transverse skull length, face width and skull height, two periods of accelerated development from the 6th to the 8th month of fetal development and from the 9th month of fetal development to the neonatal period and two periods of delayed development from the 5th to the 6th months and from the 8th to the 9th month of fetal development were revealed. For the total height of the face – periods of accelerated development – from the 4th to the 6th month of fetal development and from the 7th to the 9th month of fetal development, periods of delayed development – from the 6th to the 7th month of fetal development and from the 9th month of fetal development to the neonatal period. On the basis of arithmetic mean data of transverse skull length, face width, skull height, total face height, models for predicting normative morphometric parameters in fetuses and newborns are constructed. The constructed models will serve as a norm for the subsequent determination of certain morphometric deviations to establish variants of the structure and malformations of the skull and face. Thus, our systematized data on the features of spatio-temporal transformations of morphometric parameters of transverse skull length, face width, skull height, total face height with subsequent construction of mathematical models will contribute to the individualization of the norm, improvement of early diagnosis methods and development of new methods for surgical correction of congenital defects of the skull and face.

Tongue and Upper Airway Dimensions: A Comparative Study between Three Popular Brachycephalic Breeds

Relative macroglossia has been identified in brachycephalic compared to mesaticephalic dogs. This study assessed the tongue volume comparing three common brachycephalic breeds, including 30 French bulldogs, 30 pugs, and 15 English bulldogs. Computed tomography scans of intubated dogs with the hard palate suspended were examined for total tongue volume and cross-sectional areas (CSAs) of the tongue, oropharynx, soft palate, and nasopharyngeal airways at three levels: 1, caudal tip of the hard palate; 2, caudal tip of the hamulus; 3 cranial to the basihyoid bone. Tongue volume normalized to bodyweight, was significantly higher in English and French bulldogs than in pugs. Normalized to skull length, CSA of the tongue was smaller in pugs than in French and English bulldogs. At level 3, French bulldogs had larger oropharyngeal CSA than English bulldogs and pugs. Soft palate CSA was the largest in English bulldogs at level 3. At levels 1 and 2, soft palate and nasopharyngeal CSA was the smallest in pugs. At level 3, French bulldogs had higher total airway/soft tissue ratios than pugs. The smaller tongue volume in pugs questions the accuracy of the term macroglossia in this breed and these findings should be considered if surgical correction is sought.

Cranial morphology of captive mammals: a meta-analysis

Background Captive facilities such as zoos are uniquely instrumental in conservation efforts. To fulfill their potential as bastions for conservation, zoos must preserve captive populations as appropriate proxies for their wild conspecifics; doing so will help to promote successful reintroduction efforts. Morphological changes within captive populations may be detrimental to the fitness of individual animals because these changes can influence functionality; thus, it is imperative to understand the breadth and depth of morphological changes occurring in captive populations. Here, we conduct a meta-analysis of scientific literature reporting comparisons of cranial measures between captive and wild populations of mammals. We investigate the pervasiveness of cranial differences and whether cranial morphological changes are associated with ecological covariates specific to individual species, such as trophic level, dietary breadth, and home range size. Results Cranial measures of skull length, skull width, and the ratio of skull length-to-width differed significantly between many captive and wild populations of mammals reported in the literature. Roughly half of captive populations differed from wild populations in at least one cranial measure, although the degree of changes varied. Carnivorous species with a limited dietary breadth displayed the most consistent changes associated with skull widening. Species with a more generalized diet displayed less morphological changes in captivity. Conclusions Wild and captive populations of mammals differed in cranial morphology, but the nature and magnitude of their cranial differences varied considerably across taxa. Although changes in cranial morphology occur in captivity, specific changes cannot be generalized for all captive mammal populations. The nature of cranial changes in captivity may be specific to particular taxonomic groups; thus, it may be possible to establish expectations across smaller taxonomic units, or even disparate groups that utilize their cranial morphology in a similar way. Given that morphological changes occurring in captive environments like zoos have the potential to limit reintroduction success, our results call for a critical evaluation of current captive husbandry practices to prevent unnecessary morphological changes.

Tooth replacement patterns in the Early Triassic epicynodont Galesaurus planiceps (Therapsida, Cynodontia)

Sixteen specimens of the Early Triassic cynodont Galesaurus planiceps (including eight that were scanned using micro-computed tomography) representing different ontogenetic stages were assembled to study the dental replacement in the species. The growth series shows that the incisors and postcanines continue to develop and replace, even in the largest (presumably oldest) specimen. In contrast, replacement of the canines ceased with the attainment of skeletal maturity, at a basal skull length of ~90 mm, suggesting that Galesaurus had a finite number of canine replacement cycles. Additionally, the functional canine root morphology of these larger specimens showed a tendency to be open-rooted, a condition not previously reported in Mesozoic theriodonts. An alternating pattern of tooth replacement was documented in the maxillary and mandibular postcanine series. Both postcanine series increased in tooth number as the skull lengthened, with the mandibular postcanine series containing more teeth than the maxillary series. In the maxilla, the first postcanine is consistently the smallest tooth, showing a proportional reduction in size as skull length increased. The longer retention of a tooth in this first locus is a key difference between Galesaurus and Thrinaxodon, in which the mesial-most postcanines are lost after replacement. This difference has contributed to the lengthening of the postcanine series in Galesaurus, as teeth continued to be added to the distal end of the tooth row through ontogeny. Overall, there are considerable differences between Galesaurus and Thrinaxodon relating to the replacement and development of their teeth.

The paleobiology and paleoecology of South African Lystrosaurus

Lystrosaurus was one of the few tetrapods to survive the end-Permian mass extinction (EPME), the most catastrophic biotic crisis in Phanerozoic history. The significant increased abundance of this genus during the post-extinction Early Triassic recovery period has made Lystrosaurus an iconic survivor taxon globally and ideal for studying changes in growth dynamics during a mass extinction. There is potential evidence of a Lilliput effect in Lystrosaurus in South Africa as the two Triassic species that became highly abundant after the EPME are relatively smaller than the two Permian species. In order to test this hypothesis a detailed examination of the body size and life history of Permo-Triassic Lystrosaurus is required. In this study, the basal skull length and growth patterns of the four South African Lystrosaurus species from the Karoo Basin, L. maccaigi, L. curvatus, L. murrayi and L. declivis, were examined using cranial measurements and bone histology. The basal skull length measurements show that the Triassic species are smaller than the Permian species and supports previous studies. The osteohistology examination of all four species reveal rapidly forming fibrolamellar bone tissues during early to mid-ontogeny. Growth marks are common in L. maccaigi and L. curvatus, but rare and inconsistent in the purely Triassic L. murrayi and L. declivis. The inconsistency of the growth marks in these latter two taxa suggests the presence of developmental plasticity. This feature may have been advantageous in allowing these species to alter their growth patterns in response to environmental cues in the post-extinction Early Triassic climate. An overall transition to slower forming parallel-fibered bone is observed in the largest individuals of L. maccaigi, but absent from the limb bones of the other species. The absence of such bone tissue or outer circumferential lamellae in L. curvatus, L. murrayi and L. declivis indicates that even the largest collected specimens do not represent fully grown individuals. Although L. murrayi and L. declivis are smaller in size, the lack of a growth asymptote in the largest specimens indicates that adult individuals would have been notably larger and may have been similar in size to large L. maccaigi and L. curvatus when fully grown. Thus, the previously described Lilliput effect, recognized by some authors in the Karoo fossil record (such as the therocephalian Moschorhinus kitchingi), may be a product of high juvenile excess mortality in the Triassic rather than a strict “dwarfing” of Lystrosaurus species. The lifestyle of Lystrosaurus was also re-examined. Although previous studies have proposed an aquatic lifestyle for the genus, the similar morphology and bone microanatomy to several other large terrestrial Permo-Triassic dicynodonts supports a fully terrestrial mode of life.

Morphometrics of the indian false vampire bat (Megaderma lyra) from district Jhelum, Pakistan

During the present study thirteen Megaderma lyra bats were observed roosting in dark, domed shaped room of Rohtas Fort, district Jhelum. Out of these, six specimens were captured from the roosting site, using hand net. All captured specimens were male. These bats were identified through their unique facial features, an erect and elongated nose-leaf, large oval ears that joined above the forehead and no tail. Mean head and body length of captured specimens was 80 mm, forearm length was 67 mm while average lengths of 3rd, 4th and 5th metacarpals were 51.73 mm, 55.17 mm and 60.42 mm, respectively. Mean skull length was 29.84 mm, breadth of braincase was 12.77 mm. Average Penis length of two specimens was 6.6 mm and total bacular length was 3.08 mm respectively. This is the first record of Megaderma lyra from district Jhelum.