The individual bones of the adult cranium of the gray short-tailed opossum, Monodelphis domestica (Wagner, 1842) are described and illustrated in multiple views based on CT scans. The author previously reported on the outer bony surfaces of the skull of Monodelphis Burnett, 1830, and the current contribution is a companion piece, paying particular attention to the inner bony surfaces (within the endocranium and nasal cavity) and the facets between individual cranial elements, including the ethmo- and frontoturbinals.

Comments are provided on the internal nasal floor skeleton, which in M. domestica includes a fused conglomerate formed by the medial palatine processes of the premaxillae, the vomer, the ethmoid, the presphenoid, and the orbitosphenoids. This conglomerate includes horizontal shelves just dorsal to the hard palate, and occurs widely in marsupials but is currently unknown in monotremes and placentals.

New specimens of Late Jurassic and Early Cretaceous decapods from Argentina document new species and new occurrences. Pehuenchia Rusconi, 1948, originally placed within Palinura and subsequently placed within Callianassidae or Mecochiridae, is herein referred to Mecochiridae. The type species, Pehuenchia tellecheai Rusconi, 1948, is herein illustrated photographically for the first time. A second species of Pehuenchia is herein referred to a new genus, resulting in Zapalianassa, new genus, and Zapalianassa magna (Rusconi, 1948), new combination, and additional specimens of the species are illustrated. A new species of the mecochirid genus Huhatanka, Huhatanka australis, in southern Argentina extends the geographic range from the Western Interior Seaway and the geologic range from the late Early Cretaceous to the early Early Cretaceous. A species of Huhatanka described from Iran is herein moved to Meyeria, resulting in Meyeria iranica (Yazdi et al., 2010), new combination. Additional specimens of Protaxius paucisaetosus Andrada et al., 2022, extend the range of the species southward. Late Jurassic and Early Cretaceous decapod occurrences in Argentina are currently known from Glypheidea, Astacidea, and Axiidea.

Previously unreported material of leptictids (Mammalia: Leptictida) is described from three latest Eocene localities in Montana: Pipestone Springs (Ch3), McCarty's Mountain (Ch2), and Diamond O Ranch (Du–Ch1). Additional and more complete specimens of Leptictis acutidens (Douglass, 1901) from its type locality are also described. The first specimens of Leptictis intermedius (Douglass, 1905) outside of the type locality of McCarty's Mountain are described from the Diamond O Ranch fauna. Although previously suggested as a synonym of Leptictis montanus (Douglas, 1905), L. intermedius is recognized as a distinct species based on its smaller size, cranial features (narrower zygomatic arch, single squamosal sinus canal, large suprameatal foramen), and dental features (paraconule transversely elongated and more lingual than metaconule on P5–M3; and metacone moderately to well developed on M3).

Leptictis thomsoni (Matthew, 1903) is referred to a new genus, Stenoleptictis based on previously undescribed lower dentitions and crania from both Pipestone Springs (type locality) and McCarty's Mountain. The most diagnostic characters of Stenolepticis thomsoni (Matthew, 1903), new combination, are the lingually narrower upper cheek teeth with reduced anterior cingula and the presence of more lateral, lyrate parasagittal crests on the cranium, features unreported in any other leptictids.