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1. Cranial anatomy of the “round‐headed” Amphisbaenian Zygaspis quadrifrons ( Squamata, Amphisbaenia ) based on high‐resolution x‐ray computed tomography

   https://doi.org/10.1002/ar.25304  

   Bell, Christopher J. ; Cadena, Cristhian ; Meza, Antonio ; Rudie, Lauren ; Lewis, Patrick J. ( October 2023 , The Anatomical Record)

   Amphisbaenians are a poorly understood clade of fossorial lizards. Because of their derived anatomy and relative scarcity, the systematics of the clade and its placement within squamates has long been controversial. Traditional approaches grouped species into four assemblages according to burrowing behavior and cranial morphology, resulting in the recognition of “shovel‐headed,” “round‐headed,” “keel‐headed,” and “spade‐headed” morphotypes. Recent phylogenetic analyses do not support the monophyly of the taxa that share those morphotypes. Detailed analyses of cranial osteology were previously accomplished using high‐resolution x‐ray computed tomography (HRXCT) for the “shovel‐headed”Rhineura hatcherii(Rhineruidae) and the “spade‐headed”Diplometopon zarudnyi(Trogonophidae). A detailed description of the “round‐headed”Amphisbaena albawas previously completed based upon traditional “dry” skeletal specimens. Seven species of the “round‐headed”Blanus(Blanidae) were also analyzed using HRXCT. The goal of that project was a comparative analysis of all extant species ofBlanusrather than a detailed, bone‐by‐bone description of one species, but certainly is useful for comparison with another “round‐headed” taxon. The “round‐headed” morphotype is by far the most common among amphisbaenians and is much in need of further documentation. We use HRXCT imagery to provide additional data about the disparity in cranial morphology among amphisbaenians. Those data allow us to provide another detailed description of a “round‐headed” amphisbaenian, the poorly known southern African speciesZygaspis quadrifrons. HRXCT is ideal for this relatively rare and diminutive species. We are able to visualize and describe a detailed reconstruction of the entire skull as well as individual cranial elements. Comparisons with other species that were described in similar detail—D.zarudnyi,Spathorhynchus fossorium,R.hatcherii, andA.alba—and to a lesser degree withBlanus, reveal a complex mosaic of morphological features of the skull inZygaspis. Preliminary data suggest that intraspecific variation is present withinZ.quadrifrons, and interspecific variation among other species ofZygaspismay be sufficient for species‐level recognition based on cranial osteology. Our description is, therefore, also intended to serve as a baseline for comparative analysis of other specimens ofZ.quadrifronsand of other species within the genus.

    

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2. Reevaluation of the cranial osteology and phylogenetic position of the early crocodyliform Eopneumatosuchus colberti , with an emphasis on its endocranial anatomy

   https://doi.org/10.1002/ar.24777  

   Melstrom, Keegan M. ; Turner, Alan H. ; Irmis, Randall B. ( October 2021 , The Anatomical Record)

   Eopneumatosuchus colbertiCrompton and Smith, 1980, known from a single partial skull, is an enigmatic crocodylomorph from the Lower Jurassic Kayenta Formation. In spite of its unique morphology, an exceptionally pneumatic braincase, and presence during a critical time period of crocodylomorph evolution, relatively little is known about this taxon. Here, we redescribe the external cranial morphology ofE.colberti, present novel information on its endocranial anatomy, evaluate its phylogenetic position among early crocodylomorphs, and seek to better characterize its ecology. Our examination clarifies key aspects of cranial suture paths and braincase anatomy. Comparisons with related taxa (e.g.,Protosuchus haughtoni) demonstrate that extreme pneumaticity of the braincase may be more widespread in protosuchids than previously appreciated. Computed tomography scans reveal an endocranial morphology that resembles that of other early crocodylomorphs, in particular the noncrocodyliform crocodylomorphAlmadasuchus figarii. There are, however, key differences in olfactory bulb and cerebral hemisphere morphology, which demonstrate the endocranium of crocodylomorphs is not as conserved as previously hypothesized. Our phylogenetic analysis recoversE.colbertias a close relative ofProtosuchus richardsoniandEdentosuchus tienshanensis, contrasting with previous hypotheses of a sister group relationship with Thalattosuchia. Previous work suggested the inner ear has some similarities to semi‐aquatic crocodyliforms, but the phylogenetic placement ofE.colbertiamong protosuchids with a terrestrial postcranial skeletal morphology complicates paleoecological interpretation.

    

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3. Morphological specialization to nectarivory in Phyllostomus discolor ( Wagner , 1843) ( Chiroptera : Phyllostomidae )

   https://doi.org/10.1002/ar.25147  

   Quinche, Laura L. ; Santana, Sharlene E. ; Rico‐Guevara, Alejandro ( December 2022 , The Anatomical Record)

   Dedicated nectarivory is a derived feeding habit that requires specialized cranial and soft‐tissue morphologies to extract nectar from flowers. Nectarivory has evolved many times in terrestrial vertebrates, and in four bat families (Pteropodidae, Phyllostomidae, Vespertilionidae, and Mystacinidae). Within phyllostomids, specializations to nectarivory have been well documented in two subfamilies, Glossophaginae and Lonchophyllinae. However, nectarivory has also evolved independently in the genusPhyllostomus(subfamily Phyllostominae). SincePhyllostomusspecies have an omnivorous diet with a high consumption of nectar, they can be used to explore the basic morphological modifications linked to evolving a nectarivorous habit. Here, we focused on describing and comparing the morphological features potentially associated with nectarivory inPhyllostomus discolor. We present the first detailed tongue and palate morphological descriptions forP. discolorand perform skull morphometric analysis including 10 species. We found hair‐like papillae on the tongue ofP. discolor, a convergent feature with Glossophaginae and nectarivorous Pteropodids; these papillae likely confer an advantage when feeding on nectar.P. discolordoes not show skull morphological features characteristic of nectarivorous bats, such as a long and narrow snout. We pose that the consumption of a variety of food, such as hard insects and fruits, and the large size ofP. discolorrelative to specialized nectarivores may create trade‐offs against morphological specialization of the skull towards nectarivory. In contrast, a long and mobile tongue with hair‐like papillae may be an evolutionary solution for nectar extraction that does not have a major impact on this species' ability to feed on other resources.

    

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4. The complex trophic anatomy of silver carp, Hypophthalmichthys molitrix , highlighting a novel type of epibranchial organ

   https://doi.org/10.1002/jmor.20891  

   Cohen, Karly Elizabeth ; Hernandez, L. Patricia ( October 2018 , Journal of Morphology)

   Hypophthalmichthys molitrix,silver carp, is an invasive Asian carp that has become increasingly widespread and ecologically destructive within the upper Mississippi River Basin. Its complex trophic anatomy may help explain the apparent efficiency with which they consume phytoplankton, outcompeting native filter feeders. This cypriniform species is characterized by trophic synapomorphies that include a palatal organ, loss of upper pharyngeal jaws, and a hypertrophied lower pharyngeal jaw. However, in silver carp these structures have become greatly modified and diverge from the more basal condition that characterizes species such as goldfish. The trophic apparatus of silver carp is composed of discrete structures that are functionally coupled: filtering plates, paired epibranchial organs (EBO), a modified palatal organ composed of large muscular folds that interdigitate with the filtering plates, and hypertrophied lower pharyngeal jaws and teeth. The filtering plates fill a significant portion of the buccal cavity, especially since the distal parts of these filtering plates make up a key component of the EBOs. EBOs, food aggregating structures found in many teleosts, are thought to have independently evolved at least six times. Ranging in complexity from small slits on the dorsal wall of the pharyngeal cavity to exceedingly intricate spiraling structures, EBOs are morphologically diverse among filter‐feeding fishes. Despite this morphological diversity and broad taxonomic distribution, little is known regarding the functional anatomy of the EBO. Moreover, the EBO in silver carp is distinct from the organs previously described in other species, being created by four independent pharyngeal involutions (instead of the more typical one or two) that form spiral‐shaped pharyngeal tubes surrounded by circumferential muscle. On each side of the head greatly hypertrophied hyomandibulae and opercles are connected to the anterior cartilaginous caps of the bilateral EBOs via enlarged muscles. Given that these fish are pump filter feeders we hypothesize that the opercula may compress and expand the EBOs during pumping causing food to be moved posteriorly toward the pharyngeal jaws.

    

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5. Vertical Clinging and Leaping Ahead: How Bamboo Has Shaped the Anatomy and Physiology of Hapalemur

   https://doi.org/10.1002/ar.24183  

   Hemingway, Holden W. ; Burrows, Anne M. ; Omstead, Kailey M. ; Zohdy, Sarah ; Pastor, Juan Francisco ; Muchlinski, Magdalena N. ( June 2019 , The Anatomical Record)

   Hapalemur sps. andProlemur simus(bamboo lemurs, collectively) stand out from the relatively homogeneous lemurids because they are bamboo feeders and vertical clingers and leapers. This unique diet presents equally unique challenges, like its verticality, toughness, and toxicity. The bamboo lemurs share the generalized anatomy of the other lemurids, but also display some well‐documented skeletal adaptations, perhaps to overcome the problems presented by their specialization. Soft‐tissue adaptations, however, remain largely unexplored. Explored here are possible soft‐tissue adaptations inHapalemur griseus. We compareH.griseuswith other lemurids,Propithecus,Galago,Tarsier, and a tree shrew. Based on the available anatomical and physiological data, we hypothesize thatHapalemurandProlemurspecies will have differences in hindlimb morphology when compared with other lemurids. We predict thatH.griseuswill have more hindlimb muscle mass and will amplify muscle mass differences with increased type II muscle fibers. Relative hindlimb muscle mass inH.griseusis less than other prosimians sampled, yet relative sural muscle mass is significantly heavier (P< 0.01) inH.griseus. Results show that the soleus muscle ofH.griseushas a higher amount of type II (fast) fibers in plantarflexors. These findings indicate althoughH.griseusshares some generalized lemurid morphology, its diet of bamboo may have pushed this generalized lemurid to an anatomical extreme. We suspect additional bamboo‐specific adaptations in their anatomy and physiology will be uncovered with further examination into the anatomy of the bamboo lemurs. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc. Anat Rec, 303:295–307, 2020. © 2019 American Association for Anatomy

    

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