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1. Middle to Late Paleocene Leguminosae fruits and leaves from Colombia

   https://doi.org/10.1071/SB19001  

   Herrera, Fabiany; Carvalho, Mónica R.; Wing, Scott L.; Jaramillo, Carlos; Herendeen, Patrick S. (January 2019, Australian Systematic Botany)

   Leguminosae are one of the most diverse flowering-plant groups today, but the evolutionary history of the family remains obscure because of the scarce early fossil record, particularly from lowland tropics. Here, we report ~500 compression or impression specimens with distinctive legume features collected from the Cerrejón and Bogotá Formations, Middle to Late Paleocene of Colombia. The specimens were segregated into eight fruit and six leaf morphotypes. Two bipinnate leaf morphotypes are confidently placed in the Caesalpinioideae and are the earliest record of this subfamily. Two of the fruit morphotypes are placed in the Detarioideae and Dialioideae. All other fruit and leaf morphotypes show similarities with more than one subfamily or their affinities remain uncertain. The abundant fossil fruits and leaves described here show that Leguminosae was the most important component of the earliest rainforests in northern South America c. 60–58 million years ago. 

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2. Reassessing floral diversity at Río Pichileufú, earliest middle Eocene of Río Negro, Argentina

   https://doi.org/10.26879/1383  

   Rossetto-Harris, Gabriella; Wilf, Peter (January 2024, Palaeontologia Electronica)

   The Río Pichileufú (RP) fossil locality contains one of Patagonia’s only well-dated middle Eocene floras, deposited ca. 47.7 Ma during the onset of global temperature decline and South America's tectonic isolation. In 1938, Edward W. Berry described 135 species from RP based on compressed angiosperm leaves and rare reproductive structures. The flora was considered highly diverse and to have predominantly Neotropical affinities; however, many of Berry’s identifications were botanically incorrect, confusing interpretations of composition, diversity, and biogeography. Only a fraction of the flora has been studied since, and substantial new collections have remained unevaluated. Here, we reassess the fossil leaves from RP, creating a stable platform for systematic and ecological analyses. We use a morphotype approach to bypass the numerous prior taxonomic errors, while preserving nomenclatural links to specimens. We jointly consider the type and cohort (n = 696) and recent (n = 1286) collections. We validate 82 leaf morphotypes in the type collections, much lower than Berry’s estimate of 131, and consider 43 species as indeterminate. We find that 44 historical species were improperly split, lumped, or misaligned to existing names. At least 12 plant families and 30 plant genera initially reported from the site are unreliable, including Poaceae, Cannabaceae, Ericaceae, Hydrangeaceae, and Rosaceae. However, considering all the collections, we recognize 158 total leaf morphotypes. Reliable taxa include ginkgophytes, Norfolk Island pines (Araucaria), legumes (Fabaceae), soapberries (Sapindaceae), and laurels (Lauraceae). Although Berry's initial assessment of diversity at RP was significantly overestimated, including new material re-establishes the flora as exceptionally diverse. 

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3. Can Geometric Morphometric Analyses of Limb Shape Reveal Ecomorphological Patterns Across the Evolutionary History of Synapsida?

   Lungmus, J. K.; Angielczyk, K. D. (April 2019, Journal of morphology)

   Extant Mammalia are the only living representatives of the larger clade known as Synapsida, which has a continuous fossil record from around 320 million years ago to today. Despite the fact that much of the ecological diversity of mammals has been considered in light of limb morphology, the deep time origin of synapsid limb diversity and its influence on ecological diversity has received less attention. Here, we present shape analyses focusing on the forelimbs of the two earliest synapsid radiations (“pelycosaurs”, and pre-mammaliaforme Therapsida) in comparison to a broad sample of extant Mammalia. Using an expansive geometric morphometric data set, comprised of 384 fossil specimens and 148 extant mammalian specimens, we sought evidence for ecomorphological signals that could provide insight on the ecology of the earliest synapsids. Collecting shape data of humeral and ulnar elements from an extant sample representing multiple known eco morphologies provided the framework for a comparative exploration of extinct ecomorphologies, associated specifically with locomotion. Our results show that distal humeral shape is not informative of broad locomotor ecomorphologies in early fossil Synapsida. In contrast, proximal humeral shape shows a more complex pattern that suggests shape similarity between basal synapsids and members of extant Perissodactyla, and certain highly derived fully fossorial mammals, as just two examples. Overall, however, our findings suggest general shape analyses may have limited utility when analyzing for ecological-signal across deep time. Considering skeletal morphology in a holistic framework that considers unique combinations of shapes, as well as the use of biomechanically focused indices (such are functional proportions), may help to elucidate the more nuanced ways that locomotor ecology influenced limb shape in some of the earliest amniote radiations. 

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4. RECONSTRUCTING THE CLIMATE AND ECOLOGY OF AN EARLY MIOCENE TROPICAL FOREST ON THE FLANKS OF THE TINDERET VOLCANO, NYANZA PROVINCE, WESTERN KENYA

   Munyaka, Venanzio; Oginga, Kennedy; Cote, Susanne; Head, Jason J; Lukens, William; Kinyanjui, Rahab N; Manthi, Fredrick Kyalo; McNulty, Kieran P; Hall, Abigail S; Tegart, A (July 2024, University of Michigan Papers on Paleontology)

   Eastern African terrestrial ecosystems in the Early Miocene are characterized by habitat heterogeneity resulting from local rifting, climate variation, and biogeography. These dynamic landscapes profoundly influenced the evolutionary trajectories of hominoids and other mammals. In western Kenya, a collection of Early Miocene fossil-rich sites (ca. 20 Ma) proximate to the extinct Tinderet Volcano, offers a unique window into understanding habitat preferences and ecological drivers to the evolution of hominoids. Here, we present data from one of the sites, Koru 16, with evidence of remarkably preserved fossil fauna, fossil leaves, tree stump casts, and paleosols, to provide invaluable insights into the ancient ecological dynamics of the region. We use multiple proxies to reconstruct the paleoclimate and paleoecology of the Koru 16 site. The lithofacies of the Koru 16 area are characterized as interbedded ash and weakly developed paleosols indicating episodic landscape disturbance from eruptions of the volcano followed by intervals of stability. Paleosol features together with paleoclimate estimates using two models based on elemental weathering (RF-MAP and PPM) indicate warm and wet conditions. More than 1000 fossil leaves collected from two stratigraphic locations at Koru 16 yielded seventeen morphotypes which were identified across both localities and displaying different distributions of morphotypes between them. The average leaf size of morphotypes form both localities is mesophyll to megaphyll and mean annual precipitation estimates using multiple leaf physiognomic methods indicate >2000 mm/yr. Leaf lifespan estimates derived from the leaf mass per area (MA) proxy suggest that the site was predominantly characterized by evergreen taxa, with limited deciduous taxa. The distribution of MA is consistent with tropical rainforests and tropical seasonal forests in equatorial Africa, indicating similarities in leaf characteristics and ecological patterns. Tree stump casts corroborate this observation, as they indicate an open forest, with density similar to modern tropical forests that support large-bodied primates. The fauna includes a medium- sized pythonid, and at least two species of apes, along with other mammalian taxa typical for the early Miocene. Our comprehensive paleoclimate and paleoecological analyses suggest that the Koru 16 site was very warm and wet, which is a climate conducive for a tropical seasonal forest transitioning into a rainforest biome. This environmental reconstruction underscores the broad distribution of Early Miocene apes in a variety of habitats, and calls into question a recent hypothesis that apes only lived in environments with a significant open component. 

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5. A New Genus and Species Representing the First Leafhopper (Hemiptera: Cicadellidae) from Eocene Rovno Amber

   https://doi.org/10.11646/palaeoentomology.3.2.7  

   DIETRICH, CHRISTOPHER H.; PERKOVSKY, EVGENY E. (April 2020, Palaeoentomology)

   null (Ed.)

   Rovnotettix brachypterus gen. et sp. nov. is described and illustrated from Eocene Rovno (Ukraine) amber and tentatively placed in subfamily Bathysmatophorinae, tribe Malmaemichungiini. The new fossil is the first cicadellid described from Rovno amber from the Volyn region and the second brachypterous leafhopper adult described from the fossil record. It does not appear to be closely related to Brevaphrodella Dietrich & Gonçalves from Eocene Baltic amber, indicating that multiple flightless cicadellid lineages, now mostly associated with dry habitats with patchy vegetation, had evolved in Europe by the Eocene. 

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