Ben Creisler
Some additional recent non-dino papers that may be of interest:
Fernando F. Garberoglio, RaÃl O. GÃmez, SebastiÃn ApesteguÃa, Michael W. Caldwell, MarÃa L. SÃnchez & Gonzalo Veiga (2019)
A new specimen with skull and vertebrae of Najash rionegrina (Lepidosauria: Ophidia) from the early Late Cretaceous of Patagonia.
Journal of Systematic Palaeontology (advance online publication)
The limbed snake Najash rionegrina from the Cenomanian (early Late Cretaceous) of the La Buitrera Palaeontological Area (LBPA), northern Patagonia is a key taxon in any study of the origin and early evolution of snakes. The original concept of the taxon was based on the holotype and a number of referred specimens including an isolated partial skull; a conservative rebuttal argued this concept was too broad due to the lack of association between the holotype elements and the referred specimens. Here we describe a new snake specimen consisting of a partial skull and closely associated vertebrae from the La Buitrera Locality, one of many productive snake localities within the LBPA. The analysis of the vertebrae of the new specimen identifies distinct features shared with the vertebrae of the N. rionegrina holotype; the partial skull of the new specimen is also identical to the partial skull that formed part of the original concept of N. rionegrina. Phylogenetic analysis, using data from the type and referred specimens, and new materials described here, reconstructs N. rionegrina as a basal snake in a âmadtsoiidâ clade outside of crown-group Serpentes. These new morphologies, and autapomorphies recognized in character analyses, permit the construction of a new and expanded diagnosis of N. rionegrina.
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Michail Rovatsos, Ivan RehÃk, Petr Velenskà & LukÃÅ KratochvÃl (2018)
Shared ancient sex chromosomes in varanids, beaded lizards and alligator lizards.
Molecular Biology and Evolution, msz024 (advance online publication)
Sex determination in varanids, Gila monsters, beaded lizards and other anguimorphan lizards is still poorly understood. Sex chromosomes were reported only in a few species based solely on cytogenetics, which precluded assessment of their homology. We uncovered Z-chromosome specific genes in varanids from their transcriptomes. Comparison of differences in gene copy numbers between sexes across anguimorphan lizards and outgroups revealed that homologous differentiated ZZ/ZW sex chromosomes are present in Gila monsters, beaded lizards, alligator lizards and a wide phylogenetic spectrum of varanids. However, these sex chromosomes are not homologous to those known in other amniotes. We conclude that differentiated sex chromosomes were already present in the common ancestor of Anguimorpha living in the early Cretaceous or even in the Jurassic Period, 115-180 million years ago, placing anguimorphan sex chromosomes among the oldest known in vertebrates. The analysis of transcriptomes of Komodo dragon (Varanus komodoensis) showed that the _expression_ levels of genes linked to anguimorphan sex chromosomes are not balanced between sexes. Besides expanding our knowledge on vertebrate sex chromosome evolution, our study has important practical relevance for breeding and ecological studies. We introduce the first, widely applicable technique of molecular sexing in varanids, Gila monsters and beaded lizards, where reliable determination of sex based on external morphology is dubious even in adults.