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Zygodactylus ochlurus sp. nov.
Tobin L. Hieronymus, David A. Waugh & Julia A. Clarke (2019)
A new zygodactylid species indicates the persistence of stem passerines into the early Oligocene in North America.
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Background
The lake deposits of the informal Ruby Paper Shale unit, part of the Renova Formation of Montana, have yielded abundant plant fossils that document Late Eocene - Early Oligocene global cooling in western North America. A nearly complete small bird with feather impressions was recovered from this unit in in 1959, but has only been informally mentioned.
Results
Here we describe this fossil and identify it as a new species of Zygodactylus, a stem lineage passerine with a zygodactyl foot. The new taxon shows morphological traits that are convergent on crown Passeriformes, including an elongate hallux, reduced body size, and a comparative shortening of proximal limb elements. The fossil documents the persistence of this lineage into the earliest Oligocene (~â33âMa) in North America. It is the latest occurring North American species of a group that persists in Europe until the Miocene.
Conclusions
Eocene-Oligocene global cooling is known to have significantly remodeled both Palearctic and Nearctic mammal faunas but its impact on related avifaunas has remained poorly understood. The geographic and temporal range expansion provided by the new taxon together with avian other taxa with limited fossil records suggests a similar pattern of retraction in North America followed by Europe.
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Romainvilla kazakhstanensis sp. nov.
N. V. Zelenkov (2018)
The Earliest Asian Duck (Anseriformes: Romainvillia) and the Origin of Anatidae.
Doklady Biological Sciences 483(1): 225â227Â
A new species of the extinct duck Romainvillia from the Upper Eocene of Kazakhstan is described. This is the earliest duck from Asia, the first record of Romainvillia beyond France and the first reliable evidence of the presence of Romainvilliinae (regarded here as family) in Asia. This occurrence shows a wide range of Romainvillia and suggests a greater similarity of Late Eocene faunas of Western Europe and Asia than it was previously thought. The origin of Romainvilliidae and their presumable descendants Anatidae may be connected with adaptation to a new biotope, the shallowing Late Eocene epicontinental Asian basins (due to a global decrease in sea level).
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Nathan Upham, Jacob A Esselstyn & Walter Jetz (2019)
Ecological causes of uneven diversification and richness in the mammal tree of life.
bioRxiv 504803;
The uneven distribution of species in the tree of life is rooted in unequal speciation and extinction among groups. Yet the causes of differential diversification are little known despite their relevance for sustaining biodiversity into the future. Here we investigate rates of species diversification across extant Mammalia, a compelling system that includes our own closest relatives. We develop a new phylogeny of nearly all ~6000 species using a 31-gene supermatrix and fossil node- and tip-dating approaches to establish a robust evolutionary timescale for mammals. Our findings link the causes of uneven modern species richness with ecologically-driven variation in diversification rates, including 24 detected rate shifts. Speciation rates are a stronger predictor of among-clade richness than clade age, countering claims of clock-like speciation in large phylogenies. Surprisingly, rate heterogeneity in recent radiations shows limited association with latitude, despite the well-known richness increase toward the equator. Instead, we find a deeper-time association where clades of high-latitude species have the highest speciation rates, suggesting that species durations are shorter outside than inside the tropics. At shallower timescales (i.e., young clades), diurnality and low vagility are both linked to greater speciation rates and extant richness. High turnover among small-ranged allopatric species may erase the signal of vagility in older clades, while diurnality may adaptively reduce competition and extinction. These findings highlight the underappreciated joint roles of ephemeral (turnover-based) and adaptive (persistence-based) diversification processes, which manifest as speciation gradients in recent and more ancient radiations to explain the evolution of mammal diversity.
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Michael O. Day & Bruce S. Rubidge (2018)Â
Biesiespoort revisited: a case study on the relationship between tetrapod assemblage zones and Beaufort lithostratigraphy south of Victoria West.
Palaeontologia Africana 53: 51-65
The relationship between the tetrapod assemblage zones of the South African Karoo Basin and the lithostratigraphic divisions of the Beaufort Group is well-established, and provides an independent means of dating fossil occurrences. However, this relationship may not be consistent across the basin; a discrepancy exists between the historical tetrapod assemblages in the vicinity of Victoria West, Northern Cape Province, and the expected tetrapod assemblage zones based on mapped geology. In order to examine this disconnect, we collected fossils at two localities close to Biesiespoort railway station, a locality that was visited on a number of occasions by Robert Broom. Our fossil samples support the biostratigraphic determinations of Broom and thus confirm that the stratigraphic extent of the biozones at these localities differs from their type areas further south. The reasons for this are unclear but could be related to the northward younging of the lithological units, implying complex depositional processes, or result from difficulties in mapping. Nevertheless, caution should be exercised when using mapped geology near Victoria West as a guide to the age of fossils found there.
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Marianella Talevi & Soledad Brezina (2019)
Bioerosion structures in a Late Cretaceous mosasaur from Antarctica.
Facies (2019) 65: 5
Bioerosive structures in the cortical region of a vertebra from a mosasaur fall in the LÃpez de Bertodano Formation (Upper Maastrichtian) in Seymour Island (Isla Marambio), Antarctica, are reported. The traces studied are similar but not coincident with the described microborings in other fossil bone remains. The morphology and extension of these bioerosive structures are considered as the result of the activity of endolithic organisms on the original vascular channels of the bone. They are approximately straight, anastomosed, and commonly filled with an opaque mineral and framboidal pyrite. As most of the bone structure is well preserved, only the small portion of the cortical region was exposed to the microorganisms' activity. This would mean that the mosasaur individual died well earlier than the burial event. This is their first report of this type of bioerosive structures in a mosasaur fall.
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D. I. Pashchenko (2018)
A New Interpretation of the Crocodile Forelimb Morphological Features as Adaptation to Parasagittal Quadrupedal Locomotion on the Ground.
Doklady Biological Sciences 483(1): 235â238Â
We describe the crocodile forelimb features that distinguish them from other reptiles. Reduction of the clavicle and a change in the coracoid shape seem to be another way of maintaining the efficient step length, while the antebrachium and manus transformations create peculiar oblique manus position on the ground to promote the forelimb parasagittalization.
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Zuohuan Qin, Dangpeng Xi, Zhongye Shi, Yankang Xu, Feng Wei, Zhiqiang Yu, Baoxu Wu & Xiaoqiao Wan (2019)
LagerstÃtte fossils from the Lower Cretaceous Yixian Formation of the Pingquan Basin, North China: stratigraphical correlation and palaeoenvironmental implications.
Lethaia (advance online publication)
The Lower Cretaceous Yixian Formation in northeast China mainly contains the Jehol Biota. Notable investigations of the area have led to the discovery of feathered dinosaurs, angiosperms and numerous other exceptionally wellâpreserved fossils. The Yixian Formation is mostly composed of basalts interbedded with siliciclastic sediments that can be divided into several beds (from lower to upper layers, the Jianshangou Bed, Dawangzhangzi Bed and Jinggangshan Bed). However, the stratigraphy and fossils of the Yixian Formation in the northern Hebei Province are less understood than those of the western Liaoning. This study carried out a sectional excavation on a lacustrine deposit outcrop of the Yixian Formation from the Pingquan Basin in northern Hebei (the Shimen section). This fieldwork resulted in a detailed lithostratigraphical description of 52 layers, including three abundant fossil layers found within a fineâgrained clastic deposit that is 15.48 m thick. A preliminary palaeontological record was also created from primary observations and from information from previous investigations. Representative fossils included the lizard Jeholacerta formosa, fish Lecoptera sp. tadpole shrimp Chenops yixianensis conchostracans Eosestheria, dragonfly Samarura and the palaeobotanical conifers Liaoningocladus boii and Schizolepis. Comparing the lithostratigraphy and biostratigraphy of this section with other Lower Cretaceous sections in the western Liaoning, the lacustrine strata of the Shimen section correlate to the lower part of the Yixian Formation's Dawangzhangzi Bed. Based on the analysis of the characteristics of the sediment and the typical types of the plants from this section, it is suggested that the Pingquan Basin is a small volcanicâsediment basin, in temperate palaeoclimate during its deposition period.
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Gloria Arratia, Hans-Peter Schultze, and Helmut Tischlinger (2019)
On a remarkable new species of Tharsis, a Late Jurassic teleostean fish from southern Germany: its morphology and phylogenetic relationships
Fossil Record 22: 1-23
A complete morphological description, as preservation permits, is provided for a new Late Jurassic fish species (Tharsis elleri) together with a revision and comparison of some morphological features of Tharsis dubius, one of the most common species from the Solnhofen limestone, southern Germany. An emended diagnosis of the genus Tharsis -- now including two species -- is presented. The new species is characterized by a combination of morphological characters, such as the presence of a complete sclerotic ring formed by two bones placed anterior and posterior to the eye, a moderately short lower jaw with quadrate-mandibular articulation below the anterior half of the orbit, caudal vertebrae with neural and haemal arches fused to their respective vertebral centrum, and parapophyses fused to their respective centrum. A phylogenetic analysis based on 198 characters and 43 taxa is performed. Following the phylogenetic hypothesis, the sister-group relationship Ascalaboidae plus more advanced teleosts stands above the node of Leptolepis coryphaenoides. Both nodes have strong support among teleosts. The results confirm the inclusion of Ascalabos, Ebertichthys and Tharsis as members of this extinct family. Tharsis elleri n. sp. (LSID urn:lsid:zoobank.org:act:6434E6F5-2DDD-48CF-A2B1-827495FE46E6, date: 13 December 2018) is so far restricted to one Upper Jurassic German locality â Wegscheid Quarry near Schernfeld, EichstÃtt â whereas Tharsis dubius is known not only from Wegscheid Quarry, but also from different localities in the Upper Jurassic of Bavaria, Germany, and Cerin in France.