Bumbalavis anatoides gen. et sp. nov.
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N.V. Zelenkov (2021)
A revision of the Palaeocene-Eocene Mongolian Presbyornithidae (Aves: Anseriformes).
Paleontological Journal 55(3): 83-91 (Russian edition)
DOI: 10.31857/S0031031X21030132
https://www.elibrary.ru/item.asp?id=45690970Â
Remains of stem anseriforms Presbyornithidae dominate among the avian materials from the Tsagaan-Khushu locality in southern Mongolia (Naran-Bulak Formation; Upper PaleoceneâLower Eocene). Revision of the materials previously attributed to Presbyornis showed that they actually belong to two taxa of Presbyornithidae plus one or two taxa of stem flamingos (stem Phoenicopterimorphae). The relatively large presbyornithids are morphologically similar to smaller specimens of Presbyornis pervetus Wetmore, 1926 from the Lower Eocene of the United States. Another small form is described here as Bumbalavis anatoides gen. et sp. nov. and appears to be morphologically more derived than Presbyornis. Thus, Mongolian materials do not confirm the presence of significant body size dimorphism in Presbyornis. Flamingos from Tsagaan-Khushu are tentatively assigned to Juncitarsidae, to which further belongs the holotype of Presbyornis mongoliensis Kurochkin et Dyke, 2010.
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Feet must mediate substrate interactions across an animal's entire range of limb poses used in life. Metatarsals, the âbones of the sole,â are the dominant pedal skeletal elements for most tetrapods. In plantigrade species that walk on the entirety of their sole, such as living crocodylians, intermetatarsal mobility offers the potential for a continuum of reconfiguration within the foot itself. Alligator hindlimbs are capable of postural extremes from a belly sprawl to a high walk to sharp turns--how does the foot morphology dynamically accommodate these diverse demands? We implemented a hybrid combination of marker-based and markerless X-ray Reconstruction of Moving Morphology (XROMM) to measure 3-D metatarsal kinematics in three juvenile American alligators (Alligator mississippiensis) across their locomotor and maneuvering repertoire on a motorized treadmill and flat-surfaced arena.
We found that alligators adaptively conformed their metatarsals to the ground, maintaining plantigrade contact throughout a spectrum of limb placements with non-planar feet. Deformation of the metatarsus as a whole occurred through variable abduction (two-fold range of spread) and differential metatarsal pitching (45Â arc of skew). Internally, metatarsals also underwent up to 65Â of long axis rotation. Such reorientation, which correlated with skew, was constrained by the overlapping arrangement of the obliquely expanded metatarsal bases. Such a proximally overlapping metatarsal morphology is shared by fossil archosaurs and archosaur relatives. In these extinct taxa, we suggest that intermetatarsal mobility likely played a significant role in maintaining ground contact across plantigrade postural extremes.
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Squamates (lizards, snakes, and their kin such as amphisbaenians, or "worm lizards") represent the world's most diverse clade of terrestrial vertebrates with ~11,000 described extant species, representing key components in many of the world's most diverse ecosystems. With an evolutionary history dating back at least to the Middle Triassic at 242 Ma, the squamate Tree of Life also features numerous diverse but extinct branches, with hundreds of fossil species found all over the world. Despite their biological relevance both today and in the geological past, there remains a centuries-old controversy on how the major lineages of squamates are related to each other, with a direct impact on studies in ecology, evolution, paleontology, toxinology, and other fields. Here, we provide a historical overview of this long research tradition, from 19th century naturalists to 21st century phylogenomics, with special emphasis on several recent advances over the last two decades. These insights have had a dramatic effect on our understanding of the squamate Tree of Life and clarify several possible future research agendas. We provide an integrative perspective derived from genomics, morphology, and the fossil record and propose several points of synthesis in our current knowledge of broadscale squamate evolution and systematics. Key topics of interest include dating the origin and early evolution of lizards, the phylogenetic origin of snakes, the evolution of venom, recent agreements between morphological and molecular squamate evolutionary trees, genomic patterns of evolution, and the integration of morphological and molecular data sets. We conclude by providing perspectives on possible advancements in the field, directing researchers to promising future lines of investigation that are necessary to further expand our synthetic knowledge of squamate evolution.
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Abstract Âonly for now:
David S. Berman, ÂStuart S. Sumida, ÂAmy C. Henrici, Diane Scott and Thomas Martens (2021)
The Early Permian Bolosaurid Eudibamus cursoris: Earliest Reptile to Combine Parasagittal Stride and Digitigrade Posture During Quadrupedal and Bipedal Locomotion.
Frontiers in Ecology and Evolution (abstract only)
doi: 10.3389/fevo.2021.674173
https://www.frontiersin.org/articles/10.3389/fevo.2021.674173/abstract
A comprehensive skeletal description is presented here for the first time of the lower Permian (Artinskian) reptile Eudibamus cursoris from the Bromacker locality of Germany since its brief description in 2000 as the only known bolosaurid represented by an essentially complete, well-preserved articulated skeleton. Included in the description here is a superbly preserved, partial, articulated second specimen of E. cursoris discovered at the same locality that includes a short portion of the vertebral column associated with the pelvis and right hindlimb. Descriptions of the holotype and new specimen add substantially to features of the skull and postcranium that not only confirm a bolosaurid assignment, but also add significantly to an already long list of structural features supporting an ability unique among Paleozoic vertebrates to reach relatively high bipedal and quadrupedal running speeds employing a parasagittal stride and digitigrade stance with the limbs held in a near vertical posture. Structural differences between the two specimens are seen only in the tarsi and are attributed to different stages of ontogenetic ossification.
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A.V. Uliakhin, ÂP.P. Skutschas Â& P. G. Saburov (2021)
Age variability in the histological structure of the postcranial skeleton of Platyoposaurus stuckenbergi (Temnospondyli, Archegosauridae) from the Middle Permian of Eastern Europe.
Paleontological Journal 55(3): 70-82 (Russian edition)
DOI: 10.31857/S0031031X21030120
https://www.elibrary.ru/item.asp?id=45690967Â
The microanatomical and histological structure of different-sized femurs and hypocentra of the archegosauroid amphibian Platyoposaurus stuckenbergi from the Middle Permian (Urzhum horizon, Estemmenosuchus uralensis zone) of Eastern Europe is described, a comparative characteristic of age variability is given, and ecological features of the species are also considered. P. stuckenbergi femurs are characterized by the complete absence of calcified cartilage and the presence of up to 15 lines of arrested growth (LAGâs); hypocentra - osteoporotic structure, lack of calcified cartilage and LAGâs. Microanatomical and morphological features indicate the predominantly aquatic lifestyle of Platyoposaurus as an active predator of river and lake habitats.
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