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The fossilized skull of a small extinct amphisbaenian referable to Rhineura hatcherii Baur is described from high-resolution X-ray computed tomographic (HRXCT) imagery of a well-preserved mature specimen from the Brule Formation of Badlands National Park, South Dakota. Marked density contrast between bones and surrounding matrix and at bone-to-bone sutures enabled the digital disarticulation of individual skull elements. These novel visualizations provide insight into the otherwise inaccessible three-dimensionally complex structure of the bones of the skull and their relationships to one another, and to the internal cavities and passageways that they enclose. This study corrects several previous misidentifications of elements in the rhineurid skull and sheds light on skull construction generally in "shovel-headed" amphisbaenians. The orbitosphenoids in R. hatcherii are paired and entirely enclosed within the braincase by the frontals; this is in contrast to the condition in many extant amphisbaenians, in which a large azygous orbitosphenoid occupies a topologically distinct area of the skull, closing the anterolateral braincase wall. Rhineura hatcherii retains a vestigial jugal and a partially fused squamosal, both of which are absent in many extant species. Sculpturing on the snout of R. hatcherii represents perforating canals conveying sensory innervation; thus, the face of R. hatcherii receives cutaneous innervation to an unprecedented degree. The HRXCT data (available at www.digimorph.org) corroborate and extend previous hypotheses that the mechanical organization of the head in Rhineura is organized to a large degree around its burrowing lifestyle.

This article presents a detailed description and illustration of the skull of Liotyphlops albirostris in comparison to the skulls of Typhlophis squamosus, Leptotyphlops dulcis, and Typhlops jamaicensis, based on high-resolution X-ray computed tomography (HRXCT). The skull of T. squamosus is illustrated and discussed in detail for the first time. A number of uniquely shared derived characters is identified that support the monophyly of the clade Anomalepididae. Anomalepidids retain some features that are plesiomorphic relative to other scolecophidians, such as the presence of a supratemporal (except in Anomalepis) and ectopterygoid. The homology of the element located posteroventral to the eyeball in anomalepidids and variably referred to as a jugal or postorbital (or a fusion of both in Anomalepis) remains unknown. Scolecophidians exhibit a highly derived skull morphology adapted to head-first burrowing. Both anomalepidids and typhlopids evolved a condition known as an "outer shell design," but did so in different ways. Leptotyphlopids combine elements of both the anomalepidid and typhlopid snout morphologies.

Abstract-We performed a battery of analyses on 17 samples of the Almahata Sitta meteorite, identifying three main lithologies and several minor ones present as clasts. The main lithologies are (1) a pyroxene-dominated, very porous, highly reduced lithology, (2) a pyroxene-dominated compact lithology, and (3) an olivine-dominated compact lithology. Although it seems possible that all three lithologies grade smoothly into each other at the kg-scale, at the g-scale this is not apparent. The meteorite is a polymict ureilite, with some intriguing features including exceptionally variable porosity and pyroxene composition. Although augite is locally present in Almahata Sitta, it is a minor phase in most (but not all) samples we have observed. Low-calcium pyroxene (<5 mole% wollastonite) is more abundant than compositionally defined pigeonite; however, we found that even the low-Ca pyroxene in Almahata Sitta has the monoclinic pigeonite crystal structure, and thus is properly termed pigeonite. As the major pyroxene in Almahata Sitta is pigeonite, and the abundance of pigeonite is generally greater than that of olivine, this meteorite might be called a pigeonite-olivine ureilite, rather than the conventional olivine-pigeonite ureilite group. The wide variability of lithologies in Almahata Sitta reveals a complex history, including asteroidal igneous crystallization, impact disruption, reheating and partial vaporization, high-temperature reduction and carbon burning, and re-agglomeration.

The skull of the trogonophid amphisbaenian Diplometopon zarudnyi is described from high-resolution X-ray computed tomographic (HRXCT) imagery of a whole museum specimen preserved in ETOH. The skull was digitally resliced and disarticulated into individual elements, producing novel visualizations that allow detailed morphological analysis of its three-dimensionally complex structure. The prefrontal and jugal are absent in Diplometopon. The septomaxilla is present but hidden entirely from superficial view. In contrast to previous studies, we recognize a splenial fused to the compound bone of the mandible and a squamosal fused to the otic-occipital complex. Comparison of Diplometopon to the two other amphisbaenians previously described in comparable detail, Rhineura hatcherii and Amphisbaena alba, reveals a mosaic of cranial similarities and differences. Both Diplometopon and Rhineura exhibit a craniofacial angulation and expanded rostral blade related to use of the head as a digging tool, but the detailed architecture of these features is quite different. Additionally, whereas the snout of Rhineura exhibits a high degree of sculpturing and sensory innervation, this is not the case in Diplometopon. Unlike in Rhineura and Amphisbaena, the cranial elements of Diplometopon do not exhibit an extensive degree of overlap or complex interlocking sutures; instead, most of the cranial elements lie in loose apposition to each other. The degree to which this mosaic of features reflects functional demands, shared ancestry, and/or convergence is unclear in the absence of a stable hypothesis of amphisbaenian phylogeny.