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[dinosaur] Thylacosmilus + boreoeutherian teeth + Patagopipa + more

Ben Creisler

Recent non-dino stuff that may be interest:

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AnalÃa M. Forasiepi, Ross D.E. Macphee & Santiago HernÃndez del Pino (2019)
Caudal cranium of Thylacosmilus atrox (Mammalia, Metatheria, Sparassodonta), a South American predaceous sabertooth.
Bulletin of the American Museum of Natural History 433: 1-66
doi: Âhttps://doi.org/10.1206/0003-0090.433.1.1

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The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.


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Tesla A. Monson, ÂJeanâRenaud Boisserie, ÂMarianne F. Brasil, ÂSelene M. Clay, ÂRena Dvoretzky, ÂShruti Ravindramurthy, ÂChristopher A. Schmitt, ÂAntoine Souron, ÂRisa Takenaka, ÂPeter S. Ungar, ÂSunwoo Yoo, Michael Zhou, ÂMadeleine E. Zuercher Â& Leslea J. Hlusko (2019)
Evidence of strong stabilizing effects on the evolution of boreoeutherian (Mammalia) dental proportions.
Ecology and Evolution (advance online publication)
doi: https://doi.org/10.1002/ece3.5309

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The dentition is an extremely important organ in mammals with variation in timing and sequence of eruption, crown morphology, and tooth size enabling a range of behavioral, dietary, and functional adaptations across the class. Within this suite of variable mammalian dental phenotypes, relative sizes of teeth reflect variation in the underlying genetic and developmental mechanisms. Two ratios of postcanine tooth lengths capture the relative size of premolars to molars (premolarâmolar module, PMM), and among the three molars (molar module component, MMC), and are known to be heritable, independent of body size, and to vary significantly across primates. Here, we explore how these dental traits vary across mammals more broadly, focusing on terrestrial taxa in the clade of Boreoeutheria (Euarchontoglires and Laurasiatheria). We measured the postcanine teeth of N = 1,523 boreoeutherian mammals spanning six orders, 14 families, 36 genera, and 49 species to test hypotheses about associations between dental proportions and phylogenetic relatedness, diet, and life history in mammals. Boreoeutherian postcanine dental proportions sampled in this study carry conserved phylogenetic signal and are not associated with variation in diet. The incorporation of paleontological data provides further evidence that dental proportions may be slower to change than is dietary specialization. These results have implications for our understanding of dental variation and dietary adaptation in mammals.


Patagopipa corsolini gen. & sp. nov.

Alexis M. Aranciaga Rolando, Federico L. Agnolina & JuliÃnCorsolini (2019)
A new pipoid frog (Anura, Pipimorpha) from the Paleogene of Patagonia. Paleobiogeographical implications.
Une nouvelle grenouille pipoÃde (Anoures, Pipimorpha) du PalÃogÃne de Patagonie. Implications palÃobiogÃographiques.
Comptes Rendus Palevol (advance online publication)
doi: https://doi.org/10.1016/j.crpv.2019.04.003

The aim of the present contribution is to describe a new genus and species of Pipoidea from the Huitrera Formation (Eocene) from Patagonia, Argentina. The new genus shows a unique combination of characters indicating that it is a valid taxon different from other pipimorphs, including the coeval Llankibatrachus truebae. The phylogenetic analysis resulted in the nesting of the new taxon within a previously unrecognized endemic clade of South American aglossans. This new clade turns out to be the sister-group of crown-group Pipidae. This phylogenetic proposal reinforces the hypothesis sustaining the dispersal of pipids between Africa and South America through an island chain or a continental bridge across the Atlantic Ocean by Early Tertiary times.




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Chen Yang, ÂJinmin Zhao, ÂRaul E. Diaz Â& Nan Lyu (2019)
Development of sexual dimorphism in two sympatric skinks with different growth rates.
Ecology and Evolution (advance online publication)
doi: https://doi.org/10.1002/ece3.5358

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Sexual size dimorphism (SSD) is widespread in animals, especially in lizards (Reptilia: Squamata), and is driven by fecundity selection, maleâmale competition, or other adaptive hypotheses. However, these selective pressures may vary through different life history periods; thus, it is essential to assess the relationship between growth and SSD. In this study, we tracked SSD dynamics between a "fadingâtail color skink" (blue tail skink whose tail is only blue during its juvenile stage: Plestiodon elegans) and a "nonfade color" tail skink (retains a blue tail throughout life: Plestiodon quadrilineatus) under a controlled experimental environment. We fitted growth curves of morphological traits (body mass, SVL, and TL) using three growth models (Logistic, Gompertz, and von Bertalanffy). We found that both skinks have maleâbiased SSD as adults. Body mass has a higher goodness of fit (as represented by very high R2 values) using the von Bertalanffy model than the other two models. In contrast, SVL and TL for both skinks had higher goodness of fit when using the Gompertz model. Two lizards displayed divergent life history tactics: P. elegans grows faster, matures earlier (at 65 weeks), and presents an allometric growth rate, whereas P. quadrilineatus grows slower, matures later (at 106 weeks), and presents an isometric growth rate. Our findings imply that speciesâ and sexâspecific tradeâoffs in the allocation of energy to growth and reproduction may cause the growth patterns to diverge, ultimately resulting in the dissimilar patterns of SSD.


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