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1. Late Cretaceous sturgeons (Acipenseridae) from North America, with two new species from the Tanis site in the Hell Creek Formation of North Dakota

   https://doi.org/10.1017/jpa.2022.81  

   Hilton, Eric J.; Grande, Lance (January 2023, Journal of Paleontology)

   Abstract Although the Cretaceous is widely regarded as a time of great evolutionary transition for the freshwater fish fauna of North America, the fossil record of this period is notoriously poor, consisting mostly of fragments and isolated skeletal elements. Exceptions include the acipenseriforms, discussed in this paper, and some exceedingly rare teleosts. Here we describe two new species of well-preserved sturgeons (Acipenseridae) from the Tanis site in the Late Cretaceous Hell Creek Formation of North Dakota. The type and referred materials were preserved in a loosely consolidated matrix. † Acipenser praeparatorum n. sp. is represented by multiple body fossils (including the head and relatively complete postcranial remains) and a specimen of an intact, three dimensionally preserved skull and pectoral girdle. This taxon can be diagnosed based on features of the opercular elements (exceptionally tall and narrow branchiostegal). The second species, † Acipenser anisinferos n. sp., is represented by a partially preserved skull, and can be diagnosed by a relatively elongate preorbital region (i.e., snout) and the absence of thorn-like spines on the skull roofing bones. Most known sturgeon fossils from the Cretaceous are represented only by undiagnosable fragmentary remains (i.e., scutes and pectoral-fin spines) or poorly preserved partial skeletons (e.g., † Protoscaphirhynchus ), with † Priscosturion and † Anchiacipenser (both monotypic) being rare exceptions. Therefore, the newly discovered Tanis fossils give a rare glimpse into the evolution of Acipenseridae at a critical time in the phylogenetic history of acipenseriforms, and suggest significant morphological and taxonomic diversity early in the evolution of this group. UUID: http://zoobank.org/375b586a-2dd8-4a31-b6c4-42151e6e8fc8 

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2. Environmental factors affecting feather taphonomy

   https://doi.org/https://doi.org/10.3390/ biology11050703  

   Schweitzer MH; Zheng W; Equall N. (April 2022, Biology)

   Feathers are arguably the most complex integumentary structures in the entire animal kingdom. The evolutionary origins of feathers are still debated, but growing evidence from both molecular studies in extinct theropods [1–8] and living birds (e.g., [9–18]), as well as numerous fossil discoveries of structures morphologically consistent with feathers (e.g., [4,19–25]) indicate that feathers arose from filamentous structures first identifed in some theropod dinosaurs and birds more than 160 million years ago (e.g., [2,26,27]). However, some data suggest that integumentary structures similar to those from which feathers derived may have been present at the base of Dinosauria [28,29] or perhaps, the base of Archosauria ([30,31] and references therein). Because modern feathers are not biomineralized in life (contra [32,33]) their persistence in the fossil record is counterintuitive, but critical. The impressions of feathers in sediments surrounding skeletal elements led to the identification of Archaeopteryx as the first bird [34,35], but there was no organic trace with this specimen to suggest that any original material remained. However, the first specimen attributed to Archaeopteryx was a single, isolated feather [36]. This specimen presented differently from feather impressions surrounding the skeletal remains, instead visualized as a carbonized trace clearly distinct from the embedding sediments, suggesting that taphonomic processes resulting in preservation differed between the isolated feather and the skeletal specimen. The environmental factors resulting in these different modes of preservation remain relatively unexplored. 

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3. First sequencing of ancient coral skeletal proteins

   https://doi.org/10.1038/s41598-020-75846-4  

   Drake, Jeana L.; Whitelegge, Julian P.; Jacobs, David K. (December 2020, Scientific Reports)

   null (Ed.)

   Abstract Here we report the first recovery, sequencing, and identification of fossil biomineral proteins from a Pleistocene fossil invertebrate, the stony coral Orbicella annularis . This fossil retains total hydrolysable amino acids of a roughly similar composition to extracts from modern O. annularis skeletons, with the amino acid data rich in Asx (Asp + Asn) and Glx (Glu + Gln) typical of invertebrate skeletal proteins. It also retains several proteins, including a highly acidic protein, also known from modern coral skeletal proteomes that we sequenced by LC–MS/MS over multiple trials in the best-preserved fossil coral specimen. A combination of degradation or amino acid racemization inhibition of trypsin digestion appears to limit greater recovery. Nevertheless, our workflow determines optimal samples for effective sequencing of fossil coral proteins, allowing comparison of modern and fossil invertebrate protein sequences, and will likely lead to further improvements of the methods. Sequencing of endogenous organic molecules in fossil invertebrate biominerals provides an ancient record of composition, potentially clarifying evolutionary changes and biotic responses to paleoenvironments. 

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4. An Enigmatic Miniaturized and Attenuate Whole Lizard from the Mid-Cretaceous Amber of Myanmar

   https://doi.org/doi.org/10.3099/MCZ49.1  

   DAZA, JD; BAUER, AM; STANLEY, EL; BOLET, A; DICKSON, B; LOSOS, JB (November 2018, Breviora)

   We report the discovery of a new genus and species of amber-preserved lizard from the mid-Cretaceous of Myanmar. The fossil is one of the smallest and most complete Cretaceous lizards ever found, preserving both the articulated skeleton and remains of the muscular system and other soft tissues. Despite its completeness, its state of preservation obscures important diagnostic features.We determined its taxonomic allocation using two approaches: we used previously identified autapomorphies of squamates that were observable in the fossil; and we included the fossil in a large squamate morphological data set. The apomorphy-based identification of this specimen, including comparative data on trunk elongation in squamates, suggests its allocation to the stem-group Anguimorpha. Results from the phylogenetic analysis places the fossil in one of four positions: as sister taxon of either Shinisaurus crocodilurus or Parasaniwa wyomingensis, at the root of Varanoidea, or in a polytomy with Varanoidea and a fossorial group retrieved in a previous assessment of squamate relationships. It is clear that this fossil has many similarities with anguimorph squamates and, if this taxonomic allocation is correct, this fossil would represent the first amber-preserved member of stem Anguimorpha ever recorded, and the smallest known member of that group. It further emphasizes the role of amber inclusions in expanding our understanding of the diversity of Cretaceous lizard communities. 

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5. Paleoenvironments, taphonomy, and stable isotopic content of the terrestrial, fossil-vertebrate–bearing sequence of the El Disecado Member, El Gallo Formation, Upper Cretaceous, Baja California, México

   https://doi.org/10.1130/GES02207.1  

   Fastovsky, David E.; Montellano-Ballesteros, Marisol; Fricke, Henry C.; Ramezani, Jahandar; Tsukui, Kaori; Wilson, Gregory P.; Hall, Paul; Hernandez-Rivera, Rene; Alvarez, Geraldo (June 2020, Geosphere)

   null (Ed.)

   Abstract The Late Campanian (Late Cretaceous), upper part of the El Disecado Member, El Gallo Formation, Baja California, México, preserves a rich fossil assemblage of microvertebrates and macrovertebrates, silicified logs, macroscopic plant remains, and pollen that was likely deposited as the distal part of a subaerial fan. The unit was episodic and high energy, with its salient features deriving from active river channels and sheet, debris-flow deposits. Landscape stability is indicated by the presence of compound paleosol horizons, containing Fe2O3 mottling in B horizons, cutans, and calcium carbonate concretions. All of these features indicate wet/dry cyclicity in subsurface horizons, likely attributable to such cyclicity in the climate. Drainage was largely to the north and to a lesser extent, the west; however, some current flow to the south and east is preserved which, in conjunction with the proximal location of marginal marine deposits, suggest the influence of tides in this setting. The fossil vertebrates preserved in this part of the El Disecado Member are almost exclusively allochthonous, preserved as disarticulated isolated clasts in hydraulic equivalence in the braided fluvial system. A relatively diverse microvertebrate assemblage is preserved, the largest components of which are first, dinosaurs, and second, turtles. Non-tetrapod fossils are relatively uncommon, perhaps reflecting an absence of permanent standing water in this depositional setting. Here we report a high-precision U-Pb date of 74.706 + 0.028 Ma (2σ internal uncertainty), obtained from zircons in an airfall tuff. The tuff is located low within the sequence studied; therefore, most of the sedimentology and fossils reported here are slightly younger. This date, which improves upon previously published 40Ar/39Ar geochronology, ultimately allows for comparison of these El Gallo faunas and environments with coeval ones globally. Primary stable isotopic nodules associated with roots in the paleosols of the terrestrial portion of the El Disecado Member are compared with ratios from similar sources from coeval northern and eastern localities in North America. Distinctive latitudinal gradients are observed in both δ13C and δ18O, reflecting the unique southern and western, coastal geographic position of this locality. These differences are best explained by differences in the floras that populated the northern and eastern localities, relative to the southern and western floras reported here. 

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