Digital 3D Reconstructions Research Articles

3D printing in anatomical lung segmentectomies: A randomized pilot trial

ObjectiveThis pilot study evaluated the impact of using a 3D printed model of the patient's bronchovascular lung anatomy on the mental workload and fatigue of surgeons during full thoracoscopic segmentectomy. DesignWe performed a feasibility pilot study of a prospective randomized controlled trial with 2 parallel arms. All included patients underwent digital 3D visual reconstruction of their bronchovascular anatomy and were randomized into the following two groups: Digital arm (only a virtual 3D model was available) and Digital + Object arm (both virtual and printed 3D models were available). The primary end-point was the surgeons’ mental workload measured using the National Aeronautics and Space Administration-Task Load Index (NASA-TLX) score. SettingBetween October 28, 2020 and October 05, 2021, we successively investigated all anatomic segmentectomies performed via thoracoscopy in the Thoracic Department of the Montsouris Mutualiste Institute, except for S6 segmentectomies and S4+5 left bi-segmentectomies. ParticipantsWe assessed 102 patients for anatomical segmentectomy. Among the, 40 were randomly assigned, and 34 were deemed analysable, with 17 patients included in each arm. ResultsComparison of the two groups, each comprising 17 patients, revealed no statistically significant difference in primary or secondary end-points. The consultation of the visual digital model was significantly less frequent when a 3D printed model was available (6 versus 54 consultations, p = 0.001). Notably, both arms exhibited high NASA-TLX scores, particularly in terms of mental demand, temporal demand, and effort scores. ConclusionIn our pilot study, 3D printed models and digital 3D reconstructions for pre-operative planning had an equivalent effect on thoracoscopic anatomic segmentectomy for experienced surgeons. The originality of this study lies in its focus on the impact of 3D printing of bronchovascular anatomy on surgeons, rather than solely on the surgical procedure.

A Digital 4D Information System on the World Scale: Research Challenges, Approaches, and Preliminary Results

Numerous digital media repositories have been set up during recent decades, each containing plenty of data about historic cityscapes. In contrast, digital 3D reconstructions of no longer extant cityscapes have so far almost solely been performed for specific cases and via manual modelling techniques. Within the Jena4D research group, we are investigating and developing methods and technologies for transferring historical media and their contextual information into 4D models. The next step will be to automate this process and extend it to the world scale. Our team are working on different facets of that endeavor: retrieving images, text, and object data from public sources; crowdsourcing and collecting qualitative data from contests and pupil labs; processing historical plans and photographs to extract spatial data; location-based mobile visualization; and collection-browsing interfaces. This article is intended to highlight (1) current challenges, (2) the state of the art, (3) our approach to 4D modelling and visualization on the world scale, and (4) results from testing demo cases in Dresden, Jena, and Amsterdam.

Interobserver reliability of biplanar radiography is unaffected by clinical factors relevant to individuals at risk of pathological lower limb torsion

BackgroundAssessments of lower limb torsion are ubiquitous in clinical gait analysis practice as pathologic lower limb rotational deformity may contribute to gait abnormalities, anterior knee pain, as well as other debilitating conditions. Understandably, the overall utility of any torsional assessment is dependent on the measurement method’s intrinsic accuracy, precision, and robustness to clinical interference factors. Recently, biplanar radiography (BPR) measurements of torsion have been shown to be both accurate and precise, but the robustness of BPR to potential interference factors is unknown. Research questionHow robust are BPR lower limb torsional assessments to six potential interference factors: amount of torsion, skeletal maturity, radiograph quality, prior osteotomy, presence of implants, and observer training background and experience? MethodsIn this retrospective cohort study, four observers of diverse backgrounds and experience generated digital 3D reconstructions of 44 lower limbs using BPR images obtained during standard of care visits (age range 7–35 years). From each reconstruction, four lower limb torsional parameters were computed: femoral torsion, femorotibial rotation, tibial torsion, and transmalleolar axis equivalent. The mean absolute deviation (MAD) of each torsional parameter – calculated across the four observers – was used as the measure of reliability and tested against all interference factors. ResultsResults demonstrated that the average MAD was 2.1 degrees for femoral torsion, 3.0 degrees for transmalleolar axis equivalent, 3.8 degrees for femorotibial rotation, and 4.7 degrees for tibial torsion. None of the six potential interference factors were found to systematically influence BPR reliability across all four torsional parameters. Of the factors found to statistically influence one or more torsional parameter, none affected MAD values to a clinically meaningful extent. SignificanceIn addition to being accurate and precise, BPR appears to be robust to several clinical factors relevant to children and young adults with or at risk for pathological lower limb torsion.

Morphological association between muscle attachments and ossification sites in the late cartilaginous skull of tuatara embryos.

During development, the embryonic cartilaginous skull in most vertebrates is partially replaced by bones with endochondral and perichondral ossifications. Muscle attachments are thought to influence the patterns of ossification and, hence, the differentiation of the skull. To investigate the association between muscle attachments and early ossifications of reptilian embryos, we conducted digital 3D reconstructions of the cranium, the head, and the neck musculature from a histological section series of a late term embryonic tuatara, Sphenodon punctatus, with a total body length of 52 mm. As the sole living rhynchocephalian species, it is an important outgroup in comparative studies of squamate evolution. We found that head and neck muscles are largely associated with early ossification of the basal plate and the palatoquadrate, and with three other ossifications in an older specimen with a total body length of 72 mm. These results suggest that tensile forces resulting from embryonic muscle contraction are largely, but not exclusively, correlated with the area of endochondral ossification in the chondrocranium and palatoquadrate in tuatara. Beyond little-known genetic factors, the complexity of chondrocranial architecture, the progress of its development, and the effect of multiple muscle transmitting forces in the chondrocranium must be considered to provide a more comprehensive discussion of the mechanical properties of the embryonic skull.

Supporting Online and On-Site Digital Diverse Travels

Cultural-heritage research has created a vast amount of information regarding heritage objects and sites. At the same time, recent efforts on the digitization of cultural heritage have provided novel means of documenting tangible cultural resources including digital images, videos, audio testimonies, and 3D reconstructions. Furthermore, ethnographic research is nowadays combined with advanced capturing technologies such as motion capture to record the intangible dimensions of heritage as these are manifested through human expression in dance, heritage crafts, etc. This amount of information is now available and should be used to create novel forms of experiential access to cultural heritage powered by the web and mobile technologies mixed with novel interaction paradigms such as virtual and augmented reality. In this article, a platform is presented that facilitates a cloud-based web application to support location-based narratives on cultural-heritage resources provided through map-based or story-based representation approaches. At the same time, the platform through the power of modern mobile devices can provide these experiences on the move using location-based and image recognition-based augmented reality to facilitate multiple usage contexts. The platform was implemented to support the goal of the project CuRe, in the context of the “Greece-Germany” bilateral collaboration action.

Space-filling and benthic competition on coral reefs.

Reef-building corals are ecosystem engineers that compete with other benthic organisms for space and resources. Corals harvest energy through their surface by photosynthesis and heterotrophic feeding, and they divert part of this energy to defend their outer colony perimeter against competitors. Here, we hypothesized that corals with a larger space-filling surface and smaller perimeters increase energy gain while reducing the exposure to competitors. This predicted an association between these two geometric properties of corals and the competitive outcome against other benthic organisms. To test the prediction, fifty coral colonies from the Caribbean island of Curaçao were rendered using digital 3D and 2D reconstructions. The surface areas, perimeters, box-counting dimensions (as a proxy of surface and perimeter space-filling), and other geometric properties were extracted and analyzed with respect to the percentage of the perimeter losing or winning against competitors based on the coral tissue apparent growth or damage. The increase in surface space-filling dimension was the only significant single indicator of coral winning outcomes, but the combination of surface space-filling dimension with perimeter length increased the statistical prediction of coral competition outcomes. Corals with larger surface space-filling dimensions (Ds > 2) and smaller perimeters displayed more winning outcomes, confirming the initial hypothesis. We propose that the space-filling property of coral surfaces complemented with other proxies of coral competitiveness, such as life history traits, will provide a more accurate quantitative characterization of coral competition outcomes on coral reefs. This framework also applies to other organisms or ecological systems that rely on complex surfaces to obtain energy for competition.

Unbiased analysis of obesity related, fat depot specific changes of adipocyte volumes and numbers using light sheet fluorescence microscopy.

In translational obesity research, objective assessment of adipocyte sizes and numbers is essential to characterize histomorphological alterations linked to obesity, and to evaluate the efficacies of experimental medicinal or dietetic interventions. Design-based quantitative stereological techniques based on the analysis of 2D-histological sections provide unbiased estimates of relevant 3D-parameters of adipocyte morphology, but often involve complex and time-consuming tissue processing and analysis steps. Here we report the application of direct 3D light sheet fluorescence microscopy (LSFM) for effective and accurate analysis of adipocyte volumes and numbers in optically cleared adipose tissue samples from a porcine model of diet-induced obesity (DIO). Subcutaneous and visceral adipose tissue samples from DIO-minipigs and lean controls were systematically randomly sampled, optically cleared with 3DISCO (3-dimensional imaging of solvent cleared organs), stained with eosin, and subjected to LSFM for detection of adipocyte cell membrane autofluorescence. Individual adipocytes were unbiasedly sampled in digital 3D reconstructions of the adipose tissue samples, and their individual cell volumes were directly measured by automated digital image analysis. Adipocyte numbers and mean volumes obtained by LSFM analysis did not significantly differ from the corresponding values obtained by unbiased quantitative stereological analysis techniques performed on the same samples, thus proving the applicability of LSFM for efficient analysis of relevant morphological adipocyte parameters. The results of the present study demonstrate an adipose tissue depot specific plasticity of adipocyte growth responses to nutrient oversupply. This was characterized by an exclusively hypertrophic growth of visceral adipocytes, whereas adipocytes in subcutaneous fat tissue depots also displayed a marked (hyperplastic) increase in cell number. LSFM allows for accurate and efficient determination of relevant quantitative morphological adipocyte parameters. The applied stereological methods and LSFM protocols are described in detail and can serve as a guideline for unbiased quantitative morphological analyses of adipocytes in other studies and species.

Dermatologic Scar Assessment With Stereoscopic Imaging and Digital Three-Dimensional Models: A Validation Study.

We evaluated a new handheld stereoscopic imaging system capable of visualizing scars with digital three-dimensional (3D) models and providing automated morphometric estimates. The objective was to validate the repeatability and accuracy of intra- and inter-investigator scan results. Engineered metal plates with depressed and elevated model scars (n = 72) were scanned six times by one investigator. In vivo hypertrophic and atrophic scars (n = 15) were scanned once by three investigators. The repeatability of morphometric estimates was assessed using coefficients of variation (CVs) to compare the variation among multiple scan results for both models and in vivo scars, with 0% reflecting a perfect match. Scar estimates from digital 3D reconstructions were compared with the known dimensions of physical model scars and with ruler measurements of in vivo scars. A total of 48 model scars and 12 in vivo scars were eligible for automated analyses with the imaging system's proprietary software. Intra-investigator scan results for the model scars were repeatable, with low variance for all parameters: volume, area, length, and depth/height (CV: 1.8-3.1%). By comparison, inter-investigator scans of real in vivo scars resulted in slightly higher median CVs (4.4-7.3%; P < 0.05). 3D model scar estimates correlated well with the known physical dimensions of model scars for all parameters (P < 0.001) and accurately reflected the measurements of in vivo scars (P < 0.001). The six in vivo scars situated on the chest and abdomen showed the highest inter-investigator variation, due to respiratory movement artifacts. Stereoscopic imaging of scars generates accurate and repeatable measurement estimates that show little intra- and inter-investigator-based assessment variation. The best results are achieved by minimizing subject movement. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Accuracy of computed radiography in osteometry: A comparison of digital imaging techniques and the effect of magnification

Abstract Introduction Osteometric data may be obtained using digital imaging techniques, such as post-mortem computed tomography (PMCT) and digital radiography, non-invasively and without ethical objection. Osteometric data from PMCT is known to be as accurate as taking direct measurements. Digital radiography is more accessible and affordable than PMCT but is limited due to the magnification of its subjects. Objectives To investigate the viability of implementing digital radiographic techniques for measurement of long bones, and to establish whether magnification can be accurately corrected for. Materials and Methods Twenty hind pig (Sus scrofa) legs were imaged using computed radiography (CR) and PMCT, and osteometric data obtained from the digital images and 3D CT volume reconstructions. Direct measurements were taken following maceration. A calibration object was imaged using CR, to provide magnification correction factors. Results Accuracy was determined by mean absolute error (AE), giving values of 3.3 ± 2.5 mm for PMCT (MPR), 2.4 ± 1.3 mm for PMCT (3D), 11.1 ± 7.4 mm for CR (PA), and 18.3 ± 14.5 mm for CR (LAT). PMCT data was more accurate than CR data. Through applying correction for magnification, CR data became closer to the direct measurement data, and stature estimation was substantially altered. Conclusion Magnification in computed radiography affects osteometric data and resulting stature estimations. Applying correction factors may be a viable option for improving accuracy. For digital radiography to be used reliably in forensic anthropology, further empirical research is needed to validate a magnification correction method.

Virtual Research Environment for digital 3D reconstructions – Standards, thresholds and prospects

Since the 1990s the application of the digital 3D reconstruction and computer-based visualisation of culturalheritage increased. The virtual reconstruction and 3D visualisation revealed a new “glittering” research space forobject-oriented disciplines such as archaeology, art history and architecture. Nevertheless the academicsconcerned with the uprising technology recognised early the lack of documentation standards in the 3Dprojects leading to the loss of information, findings and the fusion of knowledge behind the digital 3Drepresentation. Based on the methodological fundamentals of the digital 3D reconstruction the potentials andchallenges in the light of emerging Semantic Web and Web3D technologies will be introduced. The presentationsubscribes a scientific methodology and a collaborative web-based research environment followed by crucialfeatures for this kind of projects. As the groundwork a human- and machine-readable “language of objects” andthe implementation of this semantic patterns for spatial research purposes on destroyed and/or never realisedtangible cultural heritage will be discussed. Using examples from the practice the presentation explains therequirements of the Semantic Web (Linked Data), the role of controlled vocabularies, the architecture of the VREand the impact of a customised integration of interactive 3D models within the WebGL technology. Thepresentation intends to showcase the state-of-the-art on the way to a digital research infrastructure. The focuslies on the introduction of scholarly approved and sustainable digital 3D reconstruction, complaint withrecognised documentation standards and following the Linked Data requirements.

Digital 3D reconstructions using histological serial sections of lung tissue including the alveolar capillary network.

Grothausmann R, Knudsen L, Ochs M, Mühlfeld C. Digital 3D reconstructions using histological serial sections of lung tissue including the alveolar capillary network. Am J Physiol Lung Cell Mol Physiol 312: L243-L257, 2017. First published December 2, 2016; doi:10.1152/ajplung.00326.2016-The alveolar capillary network (ACN) provides an enormously large surface area that is necessary for pulmonary gas exchange. Changes of the ACN during normal or pathological development or in pulmonary diseases are of great functional impact and warrant further analysis. Due to the complexity of the three-dimensional (3D) architecture of the ACN, 2D approaches are limited in providing a comprehensive impression of the characteristics of the normal ACN or the nature of its alterations. Stereological methods offer a quantitative way to assess the ACN in 3D in terms of capillary volume, surface area, or number but lack a 3D visualization to interpret the data. Hence, the necessity to visualize the ACN in 3D and to correlate this with data from the same set of data arises. Such an approach requires a large sample volume combined with a high resolution. Here, we present a technically simple and cost-efficient approach to create 3D representations of lung tissue ranging from bronchioles over alveolar ducts and alveoli up to the ACN from more than 1 mm sample extent to a resolution of less than 1 μm. The method is based on automated image acquisition of serially sectioned epoxy resin-embedded lung tissue fixed by vascular perfusion and subsequent automated digital reconstruction and analysis of the 3D data. This efficient method may help to better understand mechanisms of vascular development and pathology of the lung.

High-quality digital 3D reconstruction of the terminal pathway of a heart stab wound

High-quality digital 3D reconstructions of microscopic findings have been involved in anatomical and histopathological research, but their potentialities in forensic pathology may also be of particular interest. We here present the use of such methods to furtherly analyse a heart stab wound in a suicidal case. External examination revealed multiple incised wounds on the wrists, three stab wounds at the neck and a single stab wound on the chest. At autopsy, injuries to the neck and wrists were superficial whereas the thoracic stab wound penetrated the chest wall and pericardium. Heart examination showed an 8-mm-long stab wound on the anterior surface of the left ventricle. Heart sectioning and inspection of the correspondent internal aspect of the left ventricle did not show a macroscopic injury, but the irregularity of the trabeculae carneae did not permit to exclude a microscopic pathway. Thus, the heart wall including the stab wound was paraffin-embedded and subjected to complete sectioning for microscopic analysis along all the wound extension. Every 10th section was stained with haematoxylin-eosin and was acquired by using a Leica DMR microscope and a high resolution digital camera. The three-dimensional aspect of the lesion was reconstructed with a software system for 3D computer graphics. Microscopic examination and 3D reconstruction demonstrated that the lesion extended to the internal surface of the ventricle wall, although for a very limited extension. 3D reconstruction also showed a certain curvilinear pattern of the lesion in the myocardium, consistent with myocardial contraction at the moment of injury and consequent vitality of the lesion. Moreover, 3D reconstruction permitted to obtain the dimensions of the intra-myocardial injury (corrected for shrinkage and evaluated in the context of muscle contraction), also permitting to furtherly confirm the identification of the knife involved. In conclusion, the present case is indicative of how complete microscopic sectioning and 3D reconstruction may add further information about characteristics of injuries of forensic interest.

Analysis of human dentition from Early Bronze Age: 4000-year-old puzzle.

This paper presents the first ever paleodontological investigation of human remains from an archeological site in Central Europe dating from the Early Bronze Age and attributed to the Strzyzow Culture. It corroborates the knowledge gained from archeological, anthropological and genetical investigations. Our study aimed to assess dental status, dental morphology and dental pathologies as well as tooth wear and enamel hypoplasia based on visual inspection and stereomicroscopic investigation. The research was supported by CBCT imaging to obtain digital images and 3D reconstructions as well as 2D radiographs essential for dental age estimation. All of the 191 teeth discovered showed morphological similarity, with adult teeth showing similar color, shape and size. A maxillary molar presenting with a unique root morphology and a mandibular molar with a rare occlusal surface were found. Both permanent and deciduous dentition presented significant tooth wear. A few specimens displayed signs of dental caries, periapical pathology and antemortem tooth loss. Three individuals exhibited linear enamel hypoplasia. CBCT provided high-quality 2D images useful for dental age estimation by non-destructive methods. Estimated dental age correlated with the age estimated by other anthropological methods. In one case, this was crucial because of insufficient material for anthropological analysis. The presented studies have proved that besides the skeleton, teeth can be used as a fundamental tool in assessing the overall health and living conditions of paleopopulations. It would seem that there is potential for considerable development to be made in the research and investigation of paleodontological material using CBCT.

Adapting anatomy teaching to surgical trends: a combination of classical dissection, medical imaging, and 3D-printing technologies.

Many regions worldwide report difficulties in recruiting applicants to surgery. One strategy proposed to reverse this trend consists of early exposure of medical students to the field. Against this backdrop, the present study presents an innovative approach for anatomy teaching, integrating a surgically relevant trend: 3D printing. Whole-body computed tomography (CT) was made of two cadavers. Twelve students performed measurements and 3D reconstructions of selected anatomical structures (Osirix, Mimics). 3D printed (3DP) models were obtained (ZPrinter 310 Plus), and the students completed the analogous measurements on these replicas. Finally, classical anatomical dissection was performed and the same parameters were measured. The differences between the values obtained by the three modalities were submitted to standard statistical analysis (Wilcoxon two-tail paired test). Qualitative comparison of the digital 3D reconstructions based on the students' manual CT segmentation and the anatomical reality showed excellent correlation. Quantitatively, the values measured on the CT images and the physical models created by 3D printing differed from those measured on the cadavers by less than 2mm. Students were highly appreciative of the approach (CT, 3DP, cadaver). Their average satisfaction score was 5.8 on a 1-6 scale. This study shows that the approach proposed can be achieved. The results obtained also show that CT-based 3D printed models are close to the authentic anatomic reality. The program allows early and interactive exposure of medical students to a surgically relevant trend-in this case 3D printing.

Morphometric structural diversity of a natural armor assembly investigated by 2D continuum strain analysis.

Many armored fish scale assemblies use geometric heterogeneity of subunits as a design parameter to provide tailored biomechanical flexibility while maintaining protection from external penetrative threats. This study analyzes the spatially varying shape of individual ganoid scales as a structural element in a biological system, the exoskeleton of the armored fish Polypterus senegalus (bichir). X-ray microcomputed tomography is used to generate digital 3D reconstructions of the mineralized scales. Landmark-based geometric morphometrics is used to measure the geometric variation among scales and to define a set of geometric parameters to describe shape variation. A formalism using continuum mechanical strain analysis is developed to quantify the spatial geometry change of the scales and illustrate the mechanisms of shape morphing between scales. Five scale geometry variants are defined (average, anterior, tail, ventral, and pectoral fin) and their functional implications are discussed in terms of the interscale mobility mechanisms that enable flexibility within the exoskeleton. The results suggest that shape variation in materials design, inspired by structural biological materials, can allow for tunable behavior in flexible composites made of segmented scale assemblies to achieve enhanced user mobility, custom fit, and flexibility around joints for a variety of protective applications.

Project “The Wooden Treasure. Preserving Heritage Design Future” – 3D visualization as a form of monument's protection

The region of Lublin has a rich tradition of the usage of timber in construction. A few dozen years ago wood was still the predominant building material in villages, towns and on the outskirts of big cities. Small multicultural towns were a characteristic element of the cultural landscape of the region. The wooden buildings of these towns compose one of the most unique phenomena in Polish and architecture. To this day some examples of particular small towns’ buildings were preserved. The main aim of the project is to create digital 3D reconstructions of five small towns of the Lublin region and a model illustrating wooden architecture of the Norwegian town of Larvik in different historical periods. All models will be accesible online on multimedia service dedicated to wooden architecture and methods of its conservation and will have connection with inventory of the most representative monuments of wooden architecture of the Lublin region, uploaded and shared via the Internet.

Comparative thorax morphology of death-feigning flightless cryptorhynchine weevils (Coleoptera: Curculionidae) based on 3D reconstructions

The thorax morphology, especially the muscles and the tracheal system of three flightless species of Cryptorhynchinae is examined by digital 3D reconstructions based on synchrotron X-ray microtomography and compared to other Curculionidae. Wings, metanepisternites, and muscles functional in flight are fully reduced in the species examined: Kyklioacalles roboris (Curtis), Trigonopterus scharfi Riedel and Trigonopterus vandekampi Riedel. All three share the same set of thoracic muscles, but differences exist in the shape and size of muscles. Both Trigonopterus species examined have a conspicuous fan-shaped branch of Musculus mesosterni primus contracting pro- and mesothorax, interpreted as an adaption to their thanatosis defense strategy. Trigonopterus vandekampi furthermore shows a marked increase in the size of two metacoxal muscles, which may be functional in this species' thanatosis blocking mechanisms. The metathoracic spiracle of all Trigonopterus species is located at the side of the metaventrite externally and not in the subelytral space as in other beetles. It is hypothesized that this translocation was triggered by the need to improve oxygen supply during thanatosis, when both the mesothoracic spiracle and the subelytral cavity are tightly sealed from the outside.

Nervous systems in 3D: A comparison of Caridean, anomuran, and brachyuran zoea‐I (DECAPODA)

Using serial semi-thin sections and digital 3D-reconstructions we studied the nervous systems of zoea-I larvae in three decapod species, Hippolyte inermis (Leach, 1815), Porcellana platycheles (Pennant, 1777), and Pachygrapsus marmoratus (Fabricius, 1787). These taxa represent three decapod lineages, that is, Caridea, Anomura, and Brachyura, each characterized by specific zoea-I morphology. Special attention was paid to development of ganglia, neuropil composition, and segmental nerves. In all zoeae studied, the overall elements, for example, the segmental ganglia, their neuropils and most of the nerves of the adult decapod nervous system are present. Ongoing differentiation processes are observable as well, most obvious in segments with well-developed limbs the ganglia are in a more advanced stage of differentiation and more voluminous compared to segments with only limb buds or without externally visible limb anlagen. Intra- and interspecific comparisons indicate that neuromere differentiation thus deviates from a simple anterior-posterior gradient as, for example, posterior thoracic neuromeres are less developed than those of the pleon. In addition, the differences in the progress of the development of ganglia between the studied taxa can best be attributed to heterochronic mechanisms. Taxon and stage-specific morphologies indicate that neuronal architecture reflects both, morphogenesis to the adult stage and specific larval adaptions, and provides sets of characters relevant to understanding the corresponding phylogeny.

Comparative anatomy of the heart–glomerulus complex of Cephalodiscus gracilis (Pterobranchia): structure, function, and phylogenetic implications

Cephalodiscus gracilis Harmer, 1905 is a semi-sessile deuterostome that shares with fish-like chordates pharyngeal gill slits and a dorsally situated brain. In order to reveal structures potentially homologous among deuterostomes and to infer their functional roles, we investigated the axial complex, associated blood vessels and structures of C. gracilis using transmission electron microscopy, light microscopy, and digital 3D reconstructions. We describe the smooth, bipartite cephalic shield retractor muscles that originate as solid compact muscles and fan out to traverse the protocoel as individual muscle cells. The axial complex consists of a cap-shaped coelomic sac, the pericardium that surrounds the central heart. The pericardium is constituted of myoepithelial cells, with the cells facing the heart being thicker and richer in myofilaments. A prominent dorsal median blood vessel opens into the heart, which gives rise to a short median ventral vessel that opens into the paired glomeruli connected to the ventral side of the stomochord. The tip of the curved stomochord rests precisely above the connection of the dorsal median vessel with the heart, a position that would allow the stomochord to function as a valve facilitating unidirectional blood flow. Glomeruli are lined by podocytes of the spacious protocoel and are considered to be the site of ultrafiltration. Two pairs of blood vessels enter the median dorsal blood vessel from the tentacles. The median dorsal blood vessel is separated from the brain by a thin basement membrane. This arrangement is consistent with the hypothesis that blood vessels in the tentacles increase oxygen supply for the brain. Based on detailed similarities, the heart–glomerulus complex of C. gracilis is considered homologous with the heart–glomerulus complex in Rhabdopleura spp., and Enteropneusta, and the axial complex in Echinodermata. In addition, we hypothesize homology to the excretory complex including Hatschek’s nephridium in Cephalochordata. Thus, the heart–glomerulus complex does not support a sister-group relationship between Echinodermata and Hemichordata, whereas the organization of the cephalic shield retractor muscles is consistent with the evolution of pterobranchs within enteropneusts.

Digital Reconstruction of the Otic Region and Inner Ear of the Non-Mammalian Cynodont Brasilitherium riograndensis (Late Triassic, Brazil) and Its Relevance to the Evolution of the Mammalian Ear

The external anatomy of the petrosal, the bony labyrinth of the inner ear, and the stapes of Brasilitherium riograndensis (specimen UFRGS-PV-1043-T) were investigated by digital 3D reconstructions based on μCT scan images. Brasilitherium is the most basal taxon bearing a distinct promontorium, although less inflated than that of Morganucodon and still lacking a flat medial facet. A bony wall formed by the petrosal separates the cochlear canal and the vestibule from the brain cavity, with an internal acoustic meatus bearing distinct foramina for the facial nerve (VII) and vestibulocochlear nerve (VIII). The semicircular canals are irregular in shape, the anterior canal being the largest and the lateral one the smallest. Brasilitherium has an elongated but straight cochlear canal. The stapes resembles the morphology of derived non-mammaliaform cynodonts, such as Probainognathus and Pachygenelus, and differs from Thrinaxodon. By the allometric relationship of the cochlear canal and the estimated body mass, Brasilitherium can be grouped with Yunnanodon and Morganucodon in a regression line, which is below the line of mammals and above the line of non-avian reptiles. Brasilitherium fits in a sequence of gradual elongation of the cochlear canal associated with the enhancement in the capacity to hear higher frequencies. Among the constraints that might have triggered these transformations in small, insectivorous, and possibly nocturnal Mesozoic cynodont taxa is the improvement of detecting acoustically active insects.