Unique Turbinal Morphology in Horseshoe Bats (Chiroptera: Rhinolophidae)

The mammalian nasal fossa contains a set of delicate and often structurally complex bones called turbinals. Turbinals and associated mucosae function in regulating respiratory heat and water loss, increasing surface area for olfactory tissue, and directing airflow within the nasal fossa. We used high‐resolution micro‐CT scanning to investigate a unique maxilloturbinal morphology in 37 species from the bat family Rhinolophidae, which we compared with those of families Hipposideridae, Megadermatidae, and Pteropodidae. Rhinolophids exhibit numerous structural modifications along the nasopharyngeal tract associated with emission of high duty cycle echolocation calls via the nostrils. In rhinolophids, we found that the maxilloturbinals and a portion of ethmoturbinal I form a pair of strand‐like bony structures on each side of the nasal chamber. These structures project anteriorly from the transverse lamina and complete a hairpin turn to project posteriorly down the nasopharyngeal duct, and vary in length among species. The strand‐like maxilloturbinals in Rhinolophidae were not observed in our outgroups and represent a synapomorphy for this family, and are unique in form among mammals. Within Rhinolophidae, maxilloturbinal size and cross‐sectional shape were correlated with phylogeny. We hypothesize that strand‐shaped maxilloturbinals may function to reduce respiratory heat and water loss without greatly impacting echolocation call transmission since they provide increased mucosal surface area for heat and moisture exchange but occupy minimal space. Alternatively, they may play a role in transmission of echolocation calls since they are located directly along the path sound travels between the larynx and nostrils during call emission. Anat Rec, 300:309–325, 2017. © 2016 Wiley Periodicals, Inc.     

Maxilloturbinal Aids in Nasophonation in Horseshoe Bats (Chiroptera: Rhinolophidae)

Horseshoe bats (Family Rhinolophidae) show an impressive array of morphological traits associated with use of high duty cycle echolocation calls that they emit via their nostrils (nasophonation). Delicate maxilloturbinal bones inside the nasal fossa of horseshoe bats have a unique elongated strand-like shape unknown in other mammals. Maxilloturbinal strands also vary considerably in length and cross-sectional shape. In other mammals, maxilloturbinals help direct respired air and prevent respiratory heat and water loss. We investigated whether strand-shaped maxilloturbinals in horseshoe bats perform a similar function to those of other mammals, or whether they were shaped for a role in nasophonation. Using histology, we studied the mucosa of the nasal fossa in Rhinolophus lepidus, which we compared with Hipposideros lankadiva (Hipposideridae) and Megaderma lyra (Megadermatidae). Using micro-CT scans of 30 horseshoe bat species, we quantified maxilloturbinal surface area and skull shape within a phylogenetic context. Histological results showed horseshoe bat maxilloturbinals are covered in a thin, poorly vascularized, sparsely ciliated mucosa poorly suited for preventing respiratory heat and water loss. Maxilloturbinal surface area was correlated with basicranial width, but exceptionally long and dorsoventrally flat maxilloturbinals did not show enhanced surface area for heat and moisture exchange. Skull shape variation appears to be driven by structures linked to nasophonation, including maxilloturbinals. Resting echolocation call frequency better predicted skull shape than did skull size, and was specifically correlated with dimensions of the rostral inflations, palate, and maxilloturbinals. These traits appear to form a morphological complex, indicating a nasophonatory role for the strand-shaped rhinolophid maxilloturbinals. Anat Rec, 2018. © 2018 American Association for Anatomy.     

The Homology of the Pelvic Elements of Zygaspis quadrifrons (Squamata: Amphisbaenia)

Limb attenuation with element loss has occurred multiple times among the Squamata (lizards, snakes, and amphisbaenians). Although most of the attention has been focused on the appendicular bones, we found that the pelvic rudiments have been studied less thoroughly and recurring disagreement is common among different authors studying the same species. We studied the osteology of the pelvic region of female and male Zygaspis quadrifrons with high‐resolution X‐ray computed tomography data. We report an osteological landmark (acetabulum) not previously detected in this taxon, the presence of which has repercussions that call for a reconsideration of the primary homology hypothesis for the identity of these bones in amphisbaenians and other squamates. Finally, we observed that the acetabulum and limb rudiments in amphisbaenians (i.e., the stylopodium when present) are situated medial to the pelvic girdle, contrasting with the large majority of tetrapods where these structures are laterally oriented. Anat Rec, 297:1407–1413, 2014. © 2014 Wiley Periodicals, Inc.     

Neuroanatomy and inner ear labyrinths of the narwhal,Monodon monoceros,and beluga,Delphinapterus leucas (Cetacea: Monodontidae)

Narwhals (Monodon monoceros) and belugas (Delphinapterus leucas) are the only extant members of the Monodontidae, and are charismatic Arctic‐endemic cetaceans that are at risk from global change. Investigating the anatomy and sensory apparatuses of these animals is essential to understanding their ecology and evolution, and informs efforts for their conservation. Here, we use X‐ray CT scans to compare aspects of the endocranial and inner ear labyrinth anatomy of extant monodontids and use the overall morphology to draw larger inferences about the relationship between morphology and ecology. We show that differences in the shape of the brain, vasculature, and neural canals of both species may relate to differences in diving and other behaviors. The cochleae are similar in morphology in the two species, signifying similar hearing ranges and a close evolutionary relationship. Lastly, we compare two different methods for calculating 90var – a calculation independent of body size that is increasingly being used as a proxy for habitat preference. We show that a ‘direct’ angular measurement method shows significant differences between Arctic and other habitat preferences, but angle measurements based on planes through the semicircular canals do not, emphasizing the need for more detailed study and standardization of this measurement. This work represents the first comparative internal anatomical study of the endocranium and inner ear labyrinths of this small clade of toothed whales.     

The Circumorbital Bones of the Gekkota (Reptilia: Squamata)

The enormous variation of the orbit in lepidosaurs is better conceptualized in terms of composition and configuration. Broadly, the orbit varies from having totally closed rim to being open posteriorly. Two processes are responsible for changes in the components of the circumorbital series, element loss and fusion. The resulting contacts among elements are the main factors determining orbital configuration. Here, we present a revision of the gekkotan circumorbital bones in the general context of the Lepidosauria. From observations of a sample of 105 species of gekkotans prepared using different techniques, we describe the main changes in the orbit and corroborate the presence or absence of some of the ambiguous elements such as the lacrimal and the jugal. The supraorbital bones of squamates are reviewed and some problems of homology are evaluated using recent phylogenenetic hypothesis. Anat Rec, 2010. © 2009 Wiley‐Liss, Inc.     

Functional asymmetry of the brain and bone marrow in hemopoiesis in (CBAxC57Bl/6)F(1) mice

The role of functional asymmetry of the brain and bone marrow in the formation of exogenous 8-day splenic CFU was studied in (CBA×C57Bl/6)F1 mice. The intensity of hemopoiesis depended on the motor asymmetry of donors and recipients of bone marrow cells and differed for bone marrow transplantations from the right and left femoral bones.     

Intercondylar notch width and the risk for anterior cruciate ligament rupture in the osteoarthritic knee: evaluation by plain radiography and CT scan

We measured the intercondylar notch morphometrically from radiographs and CT scans of 30 osteoarthritic knees. Our purpose was to assess the accuracy of the standing posteroanterior 30° flexion view in determining whether there is a critical notch width that might predict a higher risk for rupture of the anterior cruciate ligament due to osteophytes. A correlation was found between measurements made on radiographs and CT scans and the appearance of the anterior cruciate ligament at operation. A narrow notch (less than 12 mm wide) was associated with absence of the anterior cruciate ligament.     

Cranial joint histology in the mallard duck (Anas platyrhynchos): new insights on avian cranial kinesis

The evolution of avian cranial kinesis is a phenomenon in part responsible for the remarkable diversity of avian feeding adaptations observable today. Although osteological, developmental and behavioral features of the feeding system are frequently studied, comparatively little is known about cranial joint skeletal tissue composition and morphology from a microscopic perspective. These data are key to understanding the developmental, biomechanical and evolutionary underpinnings of kinesis. Therefore, here we investigated joint microstructure in juvenile and adult mallard ducks (Anas platyrhynchos; Anseriformes). Ducks belong to a diverse clade of galloanseriform birds, have derived adaptations for herbivory and kinesis, and are model organisms in developmental biology. Thus, new insights into their cranial functional morphology will refine our understanding of avian cranial evolution. A total of five specimens (two ducklings and three adults) were histologically sampled, and two additional specimens (a duckling and an adult) were subjected to micro‐computed tomographic scanning. Five intracranial joints were sampled: the jaw joint (quadrate‐articular); otic joint (quadrate‐squamosal); palatobasal joint (parasphenoid‐pterygoid); the mandibular symphysis (dentary‐dentary); and the craniofacial hinge (a complex flexion zone involving four different pairs of skeletal elements). In both the ducklings and adults, the jaw, otic and palatobasal joints are all synovial, with a synovial cavity and articular cartilage on each surface (i.e. bichondral joints) ensheathed in a fibrous capsule. The craniofacial hinge begins as an ensemble of patent sutures in the duckling, but in the adult it becomes more complex: laterally it is synovial; whereas medially, it is synostosed by a bridge of chondroid bone. We hypothesize that it is chondroid bone that provides some of the flexible properties of this joint. The heavily innervated mandibular symphysis is already fused in the ducklings and remains as such in the adult. The results of this study will serve as reference for documenting avian cranial kinesis from a microanatomical perspective. The formation of: (i) secondary articular cartilage on the membrane bones of extant birds; and (ii) their unique ability to form movable synovial joints within two or more membrane bones (i.e. within their dermatocranium) might have played a role in the origin and evolution of modern avian cranial kinesis during dinosaur evolution.     

Cranial Nerves: Morphology and Clinical Relevance

This Special Issue entitled “Cranial Nerves: phylogeny, ontogeny, morphology and clinical significance” has been divided into two consecutive volumes. This second volume is devoted to morphology and clinical relevance. Articles in this volume examine these topics from a macroscopic point of view and with a surgical interest. This volume includes articles on oculomotor nerves III, IV, and VI and their course in the orbit; intracranial and extracranial views of the V and VII pairs; and branching patterns of IX, X, XI, and XII pairs with medical significance. Together, these articles provide a general overview of cranial nerves' gross anatomical organization, as well as improving on the knowledge necessary for clinical approaches. Anat Rec, 302:555–557, 2019. © 2019 Wiley Periodicals, Inc.     

Ontogeny of the Early Triassic Cynodont Thrinaxodon liorhinus (Therapsida): Cranial Morphology

The cranial morphology of 68 Thrinaxodon liorhinus specimens, ranging in size from 30 to 96 mm in basal skull length, is investigated using both qualitative and quantitative analyses. From this comprehensive survey, we determined that nine cranial features, including five in the temporal region, separated the sample into four ontogenetic stages. A bivariate analysis of 60 specimens indicated that the skull generally increased in size isometrically, with the exception of four regions. The orbit had negative allometry, a result consistent with other ontogenetic studies of tetrapods, whereas the length of the snout, palate, and temporal region showed positive allometry. The last trend had strong positive allometry indicating that during ontogeny the length of the sagittal crest increased at a much faster rate than the rest of the skull. The large number of changes in the temporal region of the skull of Thrinaxodon may indicate a greater development of the posterior fibres of the temporalis musculature from an early ontogenetic stage. For example, the posterior sagittal crest developed much earlier in ontogeny than the anterior crest that formed in adults, and bone was deposited dorsally creating a unified posterior sagittal crest rather than having a suture that spanned the entire depth of the skull roof. In combination with the isometric height of the zygomatic arch and the almost complete absence of the zygomatic arch angulation, these ontogenetic changes suggest that there was greater development of the temporalis relative to the masseter muscles, indicating a strong posterodorsal movement of the mandible in Thrinaxodon. Anat Rec, 298:1440–1464, 2015. © 2015 Wiley Periodicals, Inc.     

Cranial Muscle Development in the Model Organism Ambystoma mexicanum: Implications for Tetrapod and Vertebrate Comparative and Evolutionary Morphology and Notes on Ontogeny and Phylogeny

There is still confusion about the homology of several cranial muscles in salamanders with those of other vertebrates. This is true, in part, because of the fact that many muscles present in early ontogeny of amphibians disappear during development and specifically during metamorphosis. Resolving this confusion is important for the understanding of the comparative and evolutionary morphology of vertebrates and tetrapods because amphibians are the phylogenetically most plesiomorphic tetrapods, concerning for example their myology, and include two often used model organisms, Xenopus laevis (anuran) and Ambystoma mexicanum (urodele). Here we provide the first detailed report of the cranial muscle development in axolotl from early ontogenetic stages to the adult stage. We describe different and complementary types of general muscle morphogenetic gradients in the head: from anterior to posterior, from lateral to medial, and from origin to insertion. Furthermore, even during the development of neotenic salamanders such as axolotls, various larval muscles become indistinct, contradicting the commonly accepted view that during ontogeny the tendency is mostly toward the differentiation of muscles. We provide an updated comparison between these muscles and the muscles of other vertebrates, a discussion of the homologies and evolution, and show that the order in which the muscles appear during axolotl ontogeny is in general similar to their appearance in phylogeny (e.g. differentiation of adductor mandibulae muscles from one anlage to four muscles), with only a few remarkable exceptions, as for example the dilatator laryngis that appears evolutionary later but in the development before the intermandibularis. Anat Rec, 296:1031–1048, 2013. © 2013 Wiley Periodicals, Inc.     

Endocasts and brain evolution in Anthracotheriidae (Artiodactyla,Hippopotamoidea)

Anthracotheres are a fossil family of ‘Suiformes’ from the Old World, North and Central America. They are known from the middle Eocene to the late Pliocene, and are suggested to be the stem group of Hippopotamidae. Yet, their soft anatomy remains poorly known. In this study we describe the virtual endocast of the late Oligocene anthracothere Microbunodon minimum, reconstructed using microtomography, as well as the natural endocast of Merycopotamus medioximus from the late Miocene. These are the first anthracothere endocasts ever described. Particular attention is given to the relative proportions of the brain, the neocortex, the cerebellum and the olfactory bulbs. The ‘backward shift’ of the pituitary of M. minimum, and the possible presence of a K lobe in M. medioximus, is discussed. Previous statements that some endocranial characters were subject to convergence among mammals are also corroborated.     

Morphometric Study of Phylogenetic and Ecologic Signals in Procyonid (Mammalia: Carnivora) Endocasts

Endocasts provide a proxy for brain morphology but are rarely incorporated in phylogenetic analyses despite the potential for new suites of characters. The phylogeny of Procyonidae, a carnivoran family with relatively limited taxonomic diversity, is not well resolved because morphological and molecular data yield conflicting topologies. The presence of phylogenetic and ecologic signals in the endocasts of procyonids will be determined using three‐dimensional geometric morphometrics. Endocasts of seven ingroup species and four outgroup species were digitally rendered and 21 landmarks were collected from the endocast surface. Two phylogenetic hypotheses of Procyonidae will be examined using methods testing for phylogenetic signal in morphometric data. In analyses of all taxa, there is significant phylogenetic signal in brain shape for both the morphological and molecular topologies. However, the analyses of ingroup taxa recover a significant phylogenetic signal for the morphological topology only. These results indicate support for the molecular outgroup topology, but not the ingroup topology given the brain shape data. Further examination of brain shape using principal components analysis and wireframe comparisons suggests procyonids possess more developed areas of the brain associated with motor control, spatial perception, and balance relative to the basal musteloid condition. Within Procyonidae, similar patterns of variation are present, and may be associated with increased arboreality in certain taxa. Thus, brain shape derived from endocasts may be used to test for phylogenetic signal and preliminary analyses suggest an association with behavior and ecology. Anat Rec, 297:2318–2330, 2014. © 2014 Wiley Periodicals, Inc.     

Maternal cradling and infant nipple preferences in rhesus monkeys (Macaca mulatta)

This study investigated lateral biases in nipple preferences, maternal cradling, carrying, and retrieval in 41 rhesus macaque (Macaca mulatta) mother–infant dyads living in two captive social groups. Observations were made during the first 6 weeks of infant life using a combination of scan sampling and ad-libitum sampling techniques. Infants exhibited a significant left-nipple preference in the first weeks of life but the bias decreased with infant age. Mothers showed a left-arm bias in carrying their infants but no significant lateral bias in cradling or retrieval. Our results suggest that the left-side cradling bias reported in studies of humans and some other primates reflects a bias in the infant's nipple preference rather than in maternal behavior. The infants' preference for the left nipple is consistent with both Salk's (1960) heartbeat hypothesis and with more recent hypotheses linking this lateral bias with brain asymmetry and hemispheric specialization for mother–infant communication. © 1998 John Wiley & Sons, Inc. Dev Psychobiol 32: 305–312, 1998     

Endocranial morphology of the piciformes (Aves,Coraciimorphae): Functional and ecological implications

We used three-dimensional digital models to investigate the brain and endosseous labyrinth morphology of selected Neotropical Piciformes (Picidae, Ramphastidae, Galbulidae and Bucconidae). Remarkably, the brain morphology of Galbulidae clearly separates from species of other families. The eminentiae sagittales of Galbulidae and Bucconidae (insectivorous with high aerial maneuverability abilities) are smaller than those of the toucans (scansorial frugivores). Galbula showed the proportionally largest cerebellum, and Ramphastidae showed the least foliated one. Optic lobes ratio relative to the telencephalic hemispheres showed a strong phylogenetic signal. Three hypotheses were tested: (a) insectivorous taxa that need precise and fast movements to catch their prey, have well developed eminentiae sagittales compared to fruit eaters, (b) species that require high beak control would show larger cerebellum compared to other brain regions and higher number of visible folia and (c) there are marked differences between the brain shape of the four families studied here that bring valuable information of this interesting bird group. Hypotheses H1 and H2 are rejected, meanwhile H3 is accepted.