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1. The Anatomy of Asilisaurus kongwe , a Dinosauriform from the Lifua Member of the Manda Beds (~Middle Triassic) of Africa

   https://doi.org/10.1002/ar.24287  

   Nesbitt, Sterling J. ; Langer, Max C. ; Ezcurra, Martin D. ( December 2019 , The Anatomical Record)

   The diagnosis of Dinosauria and interrelationships of the earliest dinosaurs relies on careful documentation of the anatomy of their closest relatives. These close relatives, or dinosaur “precursors,” are typically only documented by a handful of fossils from across Pangea and nearly all specimens are typically missing important regions (e.g., forelimbs, pelves, skulls) that appear to be important to help resolving the relationships of dinosaurs. Here, we fully describe the known skeletal elements ofAsilisaurus kongwe, a dinosauriform from the Middle Triassic Manda Beds of the Ruhuhu Basin of Tanzania. The taxon is known from many disarticulated and partially articulated remains and, most importantly, from a spectacularly preserved associated skeleton of an individual containing much of the skull, pectoral and pelvic girdles, forelimb and hindlimb, and parts of the vertebral column including much of the tail. The unprecedented detail of the anatomy indicates thatAsilisaurus kongwehad a unique skull that was short and had both a premaxillary and dentary edentulous margin, but retained a number of character states plesiomorphic for Archosauria, including a crocodylian‐like ankle configuration and a rather short foot with well‐developed metatarsals I and V. Additionally, character states present across the skeleton ofAsilisaurus kongwesuggest it is more closely related toSilesaurus opolensisthan to dinosaurs; thus suggesting high homoplasy and parallel trends within Silesauridae and within lineages of early dinosaurs. The anatomy ofAsilisaurus kongweand detailed description of early members of clades found outside Dinosauria are clearly needed to untangle the seemingly complex character evolution of the skeleton within avemetatarsalians. Anat Rec, 303:813–873, 2020. © 2019 American Association for Anatomy

    

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2. A description of a Denazinemys nodosa specimen (Testudinata, Baenidae) from the Late Cretaceous Kaiparowits Formation of southern Utah

   https://doi.org/10.3897/fr.26.102520  

   Spicher, Gaël E. ; Sertich, Joseph J. ; Girard, Léa C. ; Joyce, Walter G. ; Lyson, Tyler R. ; Rollot, Yann ( July 2023 , Fossil Record)

   Denazinemys nodosais a Late Cretaceous representative of the North American turtle clade Baenidae diagnosed, among others, by a shell surface texture consisting of raised welts. We provide a detailed description of a partial skeleton from the late Campanian Kaiparowits Formation of Utah, USA, including bone-by-bone analysis of its cranium based on images obtained using micro-computed tomography. A revised phylogenetic analysis confirms placement ofDenazinemys nodosaclose toEubaena cephalicaandBoremysspp. within the clade Eubaeninae. Comparison with a second skull from the Kaiparowits Formation previously assigned toDenazinemys nodosaquestions its referral to this taxon. An assortment of specimens from the Early to Late Campanian of Mexico and the USA had previously been referred toDenazinemys nodosabased on shell surface texture alone, even though this characteristic is known to occur in other baenids. Our review of all available material concludes thatDenazinemys nodosais currently only known from the Late Campanian of New Mexico and Utah.

    

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3. 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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4. 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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5. The Cephalic Osteoderms of Varanus komodoensis as Revealed by High‐Resolution X‐Ray Computed Tomography

   https://doi.org/10.1002/ar.24197  

   Maisano, Jessica A. ; Laduc, Travis J. ; Bell, Christopher J. ; Barber, Diane ( June 2019 , The Anatomical Record)

   Osteoderms constitute a morphological system that plays an important role in squamate systematics. However, their study and visualization have always been difficult due to their isolated occurrence in the skin, among the first organs to be removed during the skeletonization process. High‐resolution X‐ray computed tomography (HRXCT) offers a nondestructive means of visualizing osteoderms both in their natural relationship to each other and to the underlying cranial bones. Although it is often stated thatVaranus komodoensishas a “chain mail” of osteoderms, this morphological system was never described in this taxon. Further, given its size, it might be expected thatV.komodoensiswould present the extreme of osteoderm development in extant varanids, a group that tends to have weakly developed osteoderms or none at all. Indeed, our HRXCT scan of a 19‐year‐old captive individual reveals an elaborate mesh of cephalic osteoderms that are incredibly numerous and morphologically diverse. We describe this skeletal system and compare it to the cephalic osteoderms in other varanoids. Anat Rec, 302:1675–1680, 2019. © 2019 American Association for Anatomy

    

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