LI Yunfeng, HUANG Wei, WANG Hongshan, David L. DILCHER, TAN Xiao, LI Tao, NA Yuling, SUN Chunlin (2018)
The First Discovery of the Easternmost Jehol Biota from Southeastern Jilin, China. ÂÂ
Acta Geologica Sinica 92(4): 1649-1650
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Celeste PÃrez-Ben, Ana MarÃa BÃez & Rainer Schoch [2018]
Morphological evolution of the skull roof in extinct temnospondyl amphibians mirrors conservative ontogenetic patterns.
Paleorxiv preprintÂ
Understanding the evolution of development is essential to unravel how morphological evolution proceeds in phenotypic space and how the resulting morphological disparity originates. In particular, the study of ontogenetic allometric patterns and their evolution is relevant because allometry is thought to constrain morphological evolution to specific directions and to promote morphological change by producing pronounced phenotypic differences along phenotypic lines of least evolutionary resistance. The extinct clade of temnospondyl amphibians enables a unique opportunity to investigate the interplay between developmental and morphological evolution in deep time because individuals of different growth stages are known for numerous species. Temnospondyls lived during the Paleozoic and Mesozoic in a wide range of habitats and had different life cycles (e.g., metamorphosing, neotenic). In spite of this, cranial morphology is markedly conserved within the clade. Herein, we investigate whether the ontogenetic allometric patterns of the skull roof in temnospondyls are also conserved or reflect the variety of their ecological adaptations and life-cycles and examine the extent to which the ontogenetic allometry may account for the adult cranial morphology. Using geometric morphometric techniques, we computed the ontogenetic allometries of 13 temnospondyl species and the evolutionary allometry of the clade. A conserved pattern of morphological change during ontogeny not associated to phylogeny or life-style is recovered across the clade. Furthermore, the evolutionary allometry strongly resembles the conserved ontogenetic changes of shape. These results suggest strong ancestral constraints in cranial development, which, in turn, may explain the low morphological disparity in the group.
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Ferrequitherium sweeti gen. et sp. nov.
Craig S. Scott (2018)
Horolodectidae: a new family of unusual eutherians (Mammalia: Theria) from the Palaeocene of Alberta, Canada.
Zoological Journal of the Linnean Society, zly040,Â
Although the magnitude of the CretaceousâPalaeogene extinction event, and the timing and tempo of the subsequent diversification of Mammalia, continue to be debated, the evidence to date unequivocally indicates that one mammalian group in particular, the Eutheria, benefitted enormously from the selective nature of the extinctions and flourished during the Palaeocene. Western Canada has long been an important region in documenting this diversification, with a fossil record that includes significant parts of the Palaeocene. I report here on the discovery of an unusual new eutherian from rocks of earliest Late Palaeocene age (earliest Tiffanian North American Land Mammal Age) in south-western Alberta. The new mammal, named Ferrequitherium sweeti gen. et sp. nov., closely resembles a second, slightly younger eutherian, Horolodectes sunae, in the major features of the molar dentition, but differs in having comparatively unspecialized premolars. The results of phylogenetic analyses under varying conditions show strong support for a close evolutionary relationship between Ferrequitherium gen. nov. and Horolodectes, and form the basis for naming a new family, the Horolodectidae fam. nov. Horolodectids first appear near the onset of chron 26r in south-western Alberta, at the beginning of the Late Palaeocene, and may have been one of several eutherian immigrants into the Alberta Basin during mammalian faunal turnover near the EarlyâLate Palaeocene boundary.
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Christian de MUIZON, Sandrine LADEVÃZE, CharlÃne SELVA, Robin VIGNAUD & Florent GOUSSARD (2018)
Allqokirus australis (Sparassodonta, Metatheria) from the early Palaeocene of Tiupampa (Bolivia) and the rise of the metatherian carnivorous radiation in South America.
GEODIVERSITAS 40 (16): 363-459
The present paper describes a disarticulated skull of Allqokirus australis Marshall & Muizon, 1988, a basal sparassodont (Metatheria, Mammalia) from the early Palaeocene (c. 65 Ma.) of Tiupampa (Bolivia). The specimen includes the rostrum and palate with right premaxilla, both maxillae, left lacrimal, palatines and most upper teeth. The second largest element includes the frontals, the left squamosal, the parietals, the supraoccipital, the basisphenoid, the presphenoid, the alisphenoid, and part of the pterygoids. The nasals, basioccipital and exoccipitals are missing. Other elements are the left petrosal, the right jugal and squamosal, and both dentaries. The elements of the specimen allow for a good reconstruction of the skull, which is thoroughly described and compared to that of other sparassodonts and to the Tiupampa pucadelphyids, Pucadelphys and Andinodelphys. The dental morphology of Allqokirus australis is extremely similar to that of Patene simpsoni from the early Eocene of Itaboraà (Brazil) and presents distinct (although incipient) carnivorous adaptations. Furthermore, some characters of the ear region (e.g. medial process of the squamosal, deep groove for the internal carotid artery at the ventral apex of the petrosal) are also present in most other sparassodonts and in the pucadelphyids from the same locality. A parsimony analysis performed on the basis of a data matrix of 364 characters and 38 taxa placed Allqokirus in a sparassodont clade (the Mayulestidae) that also included Mayulestes and Patene. This family constitutes the sister group of all other sparassodonts. Our analysis also retrieved a large clade composed of the sparassodonts and the pucadelphyids, formally named Pucadelphyda n. superord. This superorder represents the large metatherian carnivorous radiation of the Tertiary of South America, which is first known at Tiupampa, and which started to diversify probably slightly earlier, during the late Cretacous in South America. So far, no representative of Pucadelphyda has been discovered in North America. At Tiupampa, Allqokirus and Mayulestes are the largest metatherians of the fauna and they fill the predaceous mammalian ecological niche. They are the earliest representatives of Sparassodonta, a successful metatherian carnivorous radiation which persisted in South America until the late Pliocene, i.e., during more than 63 Ma.
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Gregg F. Gunnell, Doug M. Boyer, Anthony R. Friscia, Steven Heritage, Fredrick Kyalo Manthi, Ellen R. Miller, Hesham M. Sallam, Nancy B. Simmons, Nancy J. Stevens & Erik R. Seiffert (2018)
Fossil lemurs from Egypt and Kenya suggest an African origin for Madagascar's aye-aye.
Nature Communications 9, Article number: 3193
In 1967 G.G. Simpson described three partial mandibles from early Miocene deposits in Kenya that he interpreted as belonging to a new strepsirrhine primate, Propotto. This interpretation was quickly challenged, with the assertion that Propotto was not a primate, but rather a pteropodid fruit bat. The latter interpretation has not been questioned for almost half a century. Here we re-evaluate the affinities of Propotto, drawing upon diverse lines of evidence to establish that this strange mammal is a strepsirrhine primate as originally suggested by Simpson. Moreover, our phylogenetic analyses support the recognition of Propotto, together with late Eocene Plesiopithecus from Egypt, as African stem chiromyiform lemurs that are exclusively related to the extant aye-aye (Daubentonia) from Madagascar. Our results challenge the long-held view that all lemurs are descended from a single ancient colonization of Madagascar, and present an intriguing alternative scenario in which two lemur lineages dispersed from Africa to Madagascar independently, possibly during the later Cenozoic.
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NicolÃs Mongiardino Koch & Jacques A. Gauthier (2018)
Noise and biases in genomic data may underlie radically different hypotheses for the position of Iguania within Squamata.
PLoS ONE 13(8): e0202729.
Squamate reptiles are a major component of vertebrate biodiversity whose crown-clade traces its origin to a narrow window of time in the Mesozoic during which the main subclades diverged in rapid succession. Deciphering phylogenetic relationships among these lineages has proven challenging given the conflicting signals provided by genomic and phenomic data. Most notably, the placement of Iguania has routinely differed between data sources, with morphological evidence supporting a sister relationship to the remaining squamates (Scleroglossa hypothesis) and molecular data favoring a highly nested position alongside snakes and anguimorphs (Toxicofera hypothesis). We provide novel insights by generating an expanded morphological dataset and exploring the presence of phylogenetic signal, noise, and biases in molecular data. Our analyses confirm the presence of strong conflicting signals for the position of Iguania between morphological and molecular datasets. However, we also find that molecular data behave highly erratically when inferring the deepest branches of the squamate tree, a consequence of limited phylogenetic signal to resolve this ancient radiation with confidence. This, in turn, seems to result from a rate of evolution that is too high for historical signals to survive to the present. Finally, we detect significant systematic biases, with iguanians and snakes sharing faster rates of molecular evolution and a similarly biased nucleotide composition. A combination of scant phylogenetic signal, high levels of noise, and the presence of systematic biases could result in the misplacement of Iguania. We regard this explanation to be at least as plausible as the complex scenario of convergence and reversals required for morphological data to be misleading. We further evaluate and discuss the utility of morphological data to resolve ancient radiations, as well as its impact in combined-evidence phylogenomic analyses, with results relevant for the assessment of evidence and conflict across the Tree of Life.