Eotaphrosphys gen. nov.
Motelomama gen. nov.
A. PÃrez-GarcÃa (2018)
New genera of Taphrosphyina (Pleurodira, Bothremydidae) for the French Maastrichtian 'Tretosternum' ambiguum and the Peruvian Ypresian 'Podocnemis' olssoni.
HIstorical Biology (advance online publication)
Two poorly known members of Bothremydidae, previously recognized as representatives of the genus Taphrosphys, but subsequently considered as not attributable to any of the genera so far defined, are analyzed here. Two genera are defined for these members of Taphrosphyina, each one of them being characterized by autapomorphies and by a unique character combination. The French Maastrichtian (Upper Cretaceous) species 'Tretosternum' ambiguum is attributed to the new genus Eotaphrosphys, and the Peruvian Ypresian (lower Eocene) form 'Podocnemis' olssoni to the new genus Motelomama. Eotaphrosphys is the oldest named genus of Taphrosphyina, and the only one defined in Mesozoic levels. Eotaphrosphys ambiguum is the only member of this clade recognized in Europe, Motelomama olssoni representing the only one identified in the South American record.
ZooBank LSID for the genus Eotaphrosphys ambiguum is: urn:lsid:zoobank.org:act:16FAD98A-DA04-4933-AD99-88663CE74D6C
ZooBank LSID for the genus Motelomama gen is: urn:lsid:zoobank.org:act:3E832D96-29B1-4589-B397-B57768DB39A9
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And because it's World Lizard Day (August 14):
Aaron X. Sun, Ricardo Londono, Megan L. Hudnall, Rocky S. Tuan, and Thomas P. Lozito (2018)
Differences in neural stem cell identity and differentiation capacity drive divergent regenerative outcomes in lizards and salamanders.
Proceedings of the National Academy of Sciences 201803780 (advance online publication)
Significance
The evolutionary changes behind the loss in regenerative potential from salamanders to mammals remain largely elusive. Lizards, representing an intermediary species between the two, possess a limited ability to regenerate their tails. Here, we probe the mechanisms behind the differing regenerative patterns between lizards and salamanders, and we find that neural stem cells within the regenerated spinal cords are distinct cell populations that regulate divergent tail regeneration patterns. This finding sheds light on the factors that govern regenerative ability as well as the loss of this capability and brings us one step closer to eventually elucidating strategies to allow for mammalian regeneration.
Abstract
While lizards and salamanders both exhibit the ability to regenerate amputated tails, the outcomes achieved by each are markedly different. Salamanders, such as Ambystoma mexicanum, regenerate nearly identical copies of original tails. Regenerated lizard tails, however, exhibit important morphological differences compared with originals. Some of these differences concern dorsoventral patterning of regenerated skeletal and spinal cord tissues; regenerated salamander tail tissues exhibit dorsoventral patterning, while regrown lizard tissues do not. Additionally, regenerated lizard tails lack characteristically roof plate-associated structures, such as dorsal root ganglia. We hypothesized that differences in neural stem cells (NSCs) found in the ependyma of regenerated spinal cords account for these divergent regenerative outcomes. Through a combination of immunofluorescent staining, RT-PCR, hedgehog regulation, and transcriptome analysis, we analyzed NSC-dependent tail regeneration. Both salamander and lizard Sox2+ NSCs form neurospheres in culture. While salamander neurospheres exhibit default roof plate identity, lizard neurospheres exhibit default floor plate. Hedgehog signaling regulates dorsalization/ventralization of salamander, but not lizard, NSCs. Examination of NSC differentiation potential in vitro showed that salamander NSCs are capable of neural differentiation into multiple lineages, whereas lizard NSCs are not, which was confirmed by in vivo spinal cord transplantations. Finally, salamander NSCs xenogeneically transplanted into regenerating lizard tail spinal cords were influenced by native lizard NSC hedgehog signals, which favored salamander NSC floor plate differentiation. These findings suggest that NSCs in regenerated lizard and salamander spinal cords are distinct cell populations, and these differences contribute to the vastly different outcomes observed in tail regeneration.
News:
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Gopal Murali, Sami Merilaita & Ullasa Kodandaramaiah (2018)
Grab my tail: Evolution of dazzle stripes and colourful tails in lizards.
Journal of Evolutionary Biology (advance online publication)
Understanding the functions of animal coloration has been a longâstanding question in evolutionary biology. For example, the widespread occurrence of striking longitudinal stripes and colourful tails in lizards begs for an explanation. Experiments have suggested that colourful tails can deflect attacks towards the tail (the 'deflection' hypothesis), which is sacrificable in most lizards, thereby increasing the chance of escape. Studies also suggest that in moving lizards, longitudinal body stripes can redirect predatorsâ strikes towards the tail through the 'motion dazzle' effect. Despite these experimental studies, the ecological factors associated with the evolution of such striking colourations remain unexplored. Here, we investigated if predictions from motion dazzle and attack deflection could explain the widespread occurrence of these striking marks using comparative methods and information on ecoâphysiological variables (caudal autotomy, diel activity, microhabitat, and body temperature) potentially linked to their functioning. We found both longitudinal stripes and colourful tails are associated with diurnal activity and with the ability to lose the tail. Compared to stripeless species, striped species are more likely to be groundâdwelling and have higher body temperature, emphasizing the connection of stripes to mobility and rapid escape strategy. Colourful tails and stripes have evolved multiple times in a correlated fashion, suggesting that their functions may be linked. Overall, our results together with previous experimental studies support the notion that stripes and colourful tails in lizards may have protective functions based on deflective and motion dazzle effects.