Some recent non-dino papers:
Giovanne M. Cidade, Jonas P. Souza-Filho, Annie Schmaltz Hsiou, Christopher A. Brochu & Douglas Riff (2019)
New specimens of Mourasuchus (Alligatorioidea, Caimaninae) from the Miocene of Brazil and Bolivia and their taxonomic and morphological implications.
Alcheringa (advance online publication)Â
Mourasuchus is one of the most peculiar crocodylians of all time, showing an unusual 'duck-faced' rostrum with thin, gracile mandibles. It includes four species restricted to the South American Miocene. Here, we describe ten late Miocene specimens of Mourasuchus, nine from the SolimÃes Formation of Brazil and one from Bolivia. All specimens are assigned to M. arendsi, but this assignment may change as the diversity and relationships within Mourasuchus are better understood. We also discuss several issues pertinent to the morphology of Mourasuchus: the presence of a braincase neomorph (the laterocaudal bridge), hypotheses about sexual dimorphism, the function of the squamosal âhornsâ the presence of possible thermoregulatory functions in the genus. Additionally, the paleogeographic distribution of Mourasuchus in the Miocene of South America is also discussed.
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Lutz Kettler and Catherine Carr (2019)
Neural maps of interaural time difference in the American alligator: a stable feature in modern archosaurs.
Journal of Neuroscience 2989-18
Detection of interaural time differences (ITD) is crucial for sound localization in most vertebrates. The current view is that optimal computational strategies of ITD detection depend mainly on head size and available frequencies, although evolutionary history should also be taken into consideration. In archosaurs, which include birds and crocodiles, the brainstem nucleus laminaris (NL) developed into the critical structure for ITD detection. In birds, ITDs are mapped in an orderly array or place code, whereas in the mammalian medial superior olive, the analog of NL, maps are not found. As yet, in crocodilians topographical representations have not been identified. However, non-topographic representations of ITD cannot be excluded due to different anatomical and ethological features of birds and crocodiles. Therefore, we measured ITD-dependent responses in the NL of anesthetized American alligators of either sex and identified the location of the recording sites by lesions made after recording. The measured extracellular field potentials, or neurophonics, were strongly ITD tuned and their preferred ITDs correlated with the position in NL. As in birds, delay lines, which compensate for external time differences, formed maps of ITD. The broad distributions of best ITDs within narrow frequency bands were not consistent with an optimal coding model. We conclude that the available acoustic cues and the architecture of the acoustic system in early archosaurs led to a stable and similar organization in today's birds and crocodiles although physical features, like internally coupled ears, head size or shape, and audible frequency range, vary among the two groups.
SIGNIFICANCE STATEMENT
Interaural time difference (ITD) is an important cue for sound localization, and the optimal strategies for encoding ITD in neuronal populations are the subject of ongoing debate. We show that alligators form maps of ITD very similar to birds, suggesting that their common archosaur ancestor reached a stable coding solution different from mammals. Mammals and diapsids evolved tympanic hearing independently, and local optima can be reached in evolution that are not considered by global optimal coding models. Thus, the presence of ITD maps in the brain stem may reflect a local optimum in evolutionary development. Our results underline the importance of comparative animal studies and show that optimal models must be viewed in the light of evolutionary processes.
News:
Alligator study reveals insight into dinosaur hearing
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Emily J. Lessner, Cortaiga A. Gant, Tobin L. Hieronymus, Matthew K. Vickaryous & Casey M. Holliday (2019)
Anatomy and ontogeny of the mandibular symphysis in Alligator mississippiensis.
The Anatomical Records (advance online publication)
Crocodylians evolved some of the most characteristic skulls of the animal kingdom with specializations for semiâaquatic and ambush lifestyles, resulting in a feeding apparatus capable of tolerating high biomechanical loads and bite forces and a head with a derived sense of trigeminalânerveâmediated touch. The mandibular symphysis accommodates these specializations being both at the end of a biomechanical lever and an antenna for sensation. Little is known about the anatomy of the crocodylian mandibular symphysis, hampering our understanding of form, function, and evolution of the joint in extant and extinct lineages. We explore mandibular symphysis anatomy of an ontogenetic series of Alligator mississippiensis using imaging, histology, and whole mount methods. Complex sutural ligaments emanating about a midlineâfused Meckel's cartilage bridge the symphysis. These tissues organize during days 37â42 of in ovo development. However, interdigitations do not manifest until after hatching. These soft tissues leave a hub and spokeâlike bony morphology of the symphyseal plate, which never fuses. Interdigitation morphology varies within the symphysis suggesting differential loading about the joint. Neurovascular canals extend throughout the mandibles to alveoli, integument, and bone adjacent to the symphysis. These features suggest the Alligator mandibular symphysis offers compliance in an otherwise rigid skull. We hypothesize a fused Meckel's cartilage offers stiffness in hatchling mandibles prior to the development of organized sutural ligaments and mineralized bone while offering a scaffold for somatic growth. The porosity of the dentaries due to neurovascular tissues likely allows transmission of sensory and proprioceptive information from the surroundings and the loaded symphysis.
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Paradorsetisaurus postumus gen. et sp. nov.
Xenostius futilus gen. et sp. nov.
V. R. Alifanov (2019)Â
Lizards of the Families Dorsetisauridae and Xenosauridae (Anguimorpha) from the Aptian-Albian of Mongolia.
Paleontological Journal 53(2): 72-83 (Russian edition) [English translation not yet posted]
DOI: 10.1134/S0031031X19020028
Paradorsetisaurus postumus gen. et sp. nov. and Xenostius futilus gen. et sp. nov. are two new lizards from the AptianâAlbian of Mongolia, described within of the families Dorsetisauridae and Xenosauridae (Diploglossa, Anguimorpha) respectively. Also the paper includes sections which discuss the taxonomic composition and relationships in latter families as well as the formation of the diversity in Central Asian lizards during the early Cretaceous.