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Monday, October 28th, 2024
| Time | Event | ||||||
| 9:36a | [Paleontology • 2024] Quaestio simpsonorum • A New motile animal with implications for the Evolution of axial polarity from the Ediacaran of South Australia
Abstract Fossils of the Ediacara Biota preserve the oldest evidence for complex, macroscopic animals. Most are difficult to constrain phylogenetically, however, the presence of rare, derived groups suggests that many more fossils from this period represent extant groups than are currently appreciated. One approach to recognize such early animals is to instead focus on characteristics widespread in animals today, for example multicellularity, motility, and axial polarity. Here, we describe a new taxon, Quaestio simpsonorum gen. et sp. nov. from the Ediacaran of South Australia. Quaestio is reconstructed with a thin external membrane connecting more resilient tissues with anterior-posterior polarity, left-right asymmetry and tentative evidence for dorsoventral differentiation. Associated trace fossils indicate an epibenthic and motile lifestyle. Our results suggest that Quaestio was a motile eumetazoan with a body plan not previously recognized in the Ediacaran, including definitive evidence of chirality. This organization, combined with previous evidence for axial patterning in a variety of other Ediacara taxa, demonstrates that metazoan body plans were well established in the Precambrian. Keywords: axial polarity, chirality, Ediacara Biota, motility, symmetry  Quaestio simpsonorum gen. et sp. nov. Scott D. Evans, Ian V. Hughes, Emily B. Hughes, Peter W. Dzaugis, Matthew P. Dzaugis, James G. Gehling, Diego C. García-Bellido and Mary L. Droser. 2024. A New motile animal with implications for the Evolution of axial polarity from the Ediacaran of South Australia. Evolution & Development. DOI: doi.org/10.1111/ede.12491 scientist discovers one of the earth’s earliest animals in Australian outback | ||||||
| 12:02p | [Herpetology • 2024] Brachycephalus dacnis • Among the World’s Smallest Vertebrates: A New miniaturized Flea-toad (Brachycephalidae) from the Atlantic Rainforest
Abstract The genus Brachycephalus includes miniaturized toadlets with two distinct morphotypes: brightly colored species with a bufoniform phenotype and smaller, cryptic species with a leptodactyliform phenotype. The diversity of leptodactyliform species is still underappreciated, and we generally lack fundamental information about their biology. Recent sampling efforts, including DNA analyses and recordings of advertisement calls, have improved our understanding of this group. In the present study, we describe a new species of Brachycephalus, one of the smallest vertebrates known. This new species is distinguished from its congeners by a combination of morphological, bioacoustic, and genetic data. Despite being among the smallest frogs globally (the second smallest amphibian species), it exhibits skeletal traits typical of larger frogs, such as the presence of cranial bones that are lost or fused in other miniature frogs, including other Brachycephalus. Our description underscores how new discoveries within the megadiverse fauna of the Atlantic Forest—a rich biodiversity hotspot—can provide insights into phenotypic variation, including vertebrate body size. By describing this new species, we also aim to revisit the hypothesis that the type series of B. hermogenesi includes two species, potentially including individuals of the species described here.
Brachycephalus dacnis sp. nov. Diagnosis–The new species is assigned to the genus Brachycephalus because of its miniature body size, fewer phalanges and toes than a typical frog, fingers and toe tips not expanded but apically pointed, and toes lacking circumferential grooves. The new species can be diagnosed from its congeners by the following combination of characters: (1) “leptodactyliform” body shape; (2) adult body length (SVL) smaller than 1 cm; (3) distinct and functional toes II and V; (4) presence of vestigial fingers I and IV; (5) distinct iris; (6) absence of dark markings on the skin over the pectoral region; (7) dark black or pale brown marbled venter with small white blotches in preserved specimens; (8) and advertisement call composed of one or two multi-pulsed (3–7 pulses) note with dominant frequency between 8.01 and 8.44 kHz, note duration between 0.03–0.08 s (when isolated), up to 0.41 s (when in pairs), and absence of attenuated notes. Etymology–The specific epithet name ‘dacnis’ honors the Projeto Dacnis private reserve and NGO that has supported biodiversity research since 2010 in the municipalities of São José dos Campos, Miracatu and Ubatuba (where the new species was discovered), state of São Paulo, Brazil. The name is used as an invariable noun in apposition to the generic name. Luís Felipe Toledo, Lucas Machado Botelho, Andres Santiago Carrasco-Medina, Jaimi A. Gray, Julia R. Ernetti, Joana Moura Gama, Mariana Lucio Lyra, David C. Blackburn, Ivan Nunes amd Edelcio Muscat. 2024. Among the World’s Smallest Vertebrates: A New miniaturized Flea-toad (Brachycephalidae) from the Atlantic rainforest. PeerJ. 12:e18265 DOI: doi.org/10.7717/peerj.18265 | ||||||
| 3:01p | [PaleoMammalogy • 2024] Unveiling the Neuroanatomy of Josephoartigasia monesi and the Evolution of Encephalization in Caviomorph Rodents
Abstract Caviomorph rodents are an exceptional model for studying the effects of ecological factors and size relations on brain evolution. These mammals are not only speciose and ecologically diverse but also present wide body size disparity, especially when considering their fossil relatives. Here, we described the brain anatomy of the largest known rodent, Josephoartigasia monesi, uncovering distinctive features within this species regarding other taxa. Albeit resembling extant pacarana Dinomys branickii, J. monesi stands out due to its longer olfactory tract and well-developed sagittal sinus. Challenging the previous hypothesis that giant rodents possessed comparatively smaller brains, we found that J. monesi and another giant extinct rodent, Neoepiblema acreensis, are within the encephalization range of extant caviomorphs. This was unraveled while developing the a Phylogenetic Encephalization Quotient (PEQ) for Caviomorpha. With PEQ, we were able to trace brain-size predictions more accurately, accounting for species-shared ancestry while adding the extinct taxa phenotypic diversity into the prediction model. According to our results, caviomorphs encephalization patterns are not the product of ecological adaptations, and brain allometry is highly conservative within the clade. We challenge future studies to investigate caviomorphs encephalization within different taxonomic ranks while increasing the sampled taxa diversity, especially of extinct forms, in order to fully comprehend the magnitude of this evolutionary stasis. Keywords: Adaptive regimes, Allometric trends, Brain evolution, Cranial endocast, South America, Brain Structure and Function 
José Darival Ferreira, Andrés Rinderknecht, Jamile de Moura Bubadué, Luiza Flores Gasparetto, Maria Teresa Dozo, Marcelo R. Sánchez-Villagra and Leonardo Kerber. 2024. Unveiling the Neuroanatomy of Josephoartigasia monesi and the Evolution of Encephalization in Caviomorph Rodents. Brain Structure and Function. 229; 971–985. DOI: doi.org/10.1007/s00429-024-02762-y |
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