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Tuesday, June 3rd, 2025
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| 2:15a | [Paleontology • 2025] Primicaris larvaformis • A tiny Cambrian stem-mandibulate reveals Independent Evolution of Limb Ttagmatization and Specialization in early Euarthropods
Abstract The mandibulate euarthropods are the most speciose animal group, but the evolutionary gaps in origin of mandibulate body plan remain unresolved. Marrellomorphs, a common Paleozoic euarthropod group, had a long evolutionary history from Cambrian to Devonian. With computed microtomography, here we report the fine-scale soft-bodied morphoanatomy of the oldest marrellomorph Primicaris larvaformis, a millimeters-sized euarthropod from the ~ 518-million-year-old Chengjiang biota, China. Primicaris possesses a body plan featuring morphologically similar post-antennular biramous appendages, but also mandibulate diagnostic features including multi-segmented exopodites, a well-developed and differentiated hypostome-labrum complex, and a pancrustacean-like topological configuration of frontalmost three pairs of appendages. Phylogenetic analysis resolves Acercostraca and Marrellida as stem-Mandibulata. The undifferentiated post-antennular appendages in Primicaris suggest a possibility that the head appendages acquired a crown-mandibulate configuration before their morphological specialization in mandibulate origin. The emergence of novel appendage morphotypes in Acercostraca and Marrellida reveals that the complexity of limb tagmatization evolved independently in different Euarthropoda clades. Keywords: Computed tomography, Limb tagmatization, Euarthropod, Mandibulate, Chengjiang biota, Cambrian explosion
Systematic palaeontology Phylum Euarthropoda Lankaster, 1904. Order Acercostraca Lehmann, 1955. Genus Primicaris Zhang, Han, Zhang, Liu and Shu, 2003 Primicaris larvaformis Zhang, Han, Zhang, Liu and Shu, 2003 Emended diagnosis: Small euarthropod with a body length less than 6 mm. Undivided dorsal shield with up to twelve pairs of lateral marginal spines and a pair of posterior spines. One pair of uniramous antennules is followed by up to 14 homonomous pairs of biramous appendages (emended from ref. 13).  Yao Liu, Han Zeng, Fangchen Zhao, Yuyan Zhu, Yimeng Li, Zongjun Yin and Maoyan Zhu. 2025. A tiny Cambrian stem-mandibulate reveals Independent Evolution of Limb Ttagmatization and Specialization in early Euarthropods. Scientific Reports. 15: 19115. DOI: doi.org/10.1038/s41598-025-03544-0 [31 May 2025] | ||||
| 4:02p | [Paleontology • 2025] Lunataspis gundersoni • Exceptionally preserved Ovaries in An ancient Horseshoe Crab
Horseshoe crabs are an ancient lineage of aquatic chelicerate arthropods traditionally considered to be “living fossils” exhibiting limited morphological change throughout their evolution. This paradigm is challenged by the divergent morphologies of Paleozoic and Mesozoic xiphosurans in nonmarine environments, which show greater variation of prosomal carapace shape. Marine horseshoe crabs appear to exhibit a more conservative evolutionary history punctuated by marked increases in body size during the Carboniferous and Jurassic. However, interpretation of horseshoe crab evolutionary trends is complicated by uncertainty over whether the smaller Paleozoic species represent adults or juveniles. Here, we describe a diminutive 445-million-year-old horseshoe crab, Lunataspis gundersoni sp. nov., preserving details of ovarian structures in the prosoma. Unique among Xiphosura, the new species possesses an unusually prolongated prosoma, indicating early morphological variation within the group. However, the female reproductive system appears identical to that of extant Tachypleinae. Critically, the presence of eggs demonstrates that the specimens are adults and that horseshoe crabs were significantly smaller in size during the Paleozoic. Lunataspis gundersoni displays a mixture of divergent external and conserved internal anatomy that reveals mosaic evolutionary patterns and illustrates early morphological variation among marine Xiphosura.
Arthropoda Gravenhorst, 1843 Chelicerata Heymons, 1901 Xiphosura Latreille, 1802 Lunataspis Rudkin, Young & Nowlan, 2008 Lunataspis gundersoni sp. nov. Etymology. Named in honor of the late Gerald Gunderson, co-discoverer of the Big Hill biota. Diagnosis. Xiphosura with curved genal expansion of prosomal carapace; low ophthalmic ridges present posterior to lateral eyes; cardiac lobe comprising slight swelling without lateral furrows; opisthosoma with two freely articulating tergites anterior to thoracetron; thoracetron comprising six fused segments, segmental boundaries expressed axially; postabdomen comprising four freely articulating ankylosed segments, pretelsonic segment elongated; axial nodes present centrally on each opisthosomal segment excepting the pretelson; telson lanceolate. Differentiated from other Lunataspis species by the shovel-shaped anterior prolongation of the prosomal carapace. James C. Lamsdell; Amanda R. Falk; Thomas A. Hegna and Ronald C. Meyer. 2025. Exceptionally preserved Ovaries in An ancient Horseshoe Crab. Geology. DOI: doi.org/10.1130/G53317.1 [May 29, 2025] | ||||
| 4:02p | [Entomology • 2025] Caliphaea sinuofurcata • A New Species of Caliphaea (Odonata: Calopterygidae) from Arunachal Pradesh, India
Abstract We describe a new species, Caliphaea sinuofurcata sp. nov., based on two male and one female specimens collected from Upper Siang District and Lower Dibang Valley District, Arunachal Pradesh, India. The newly described species can be distinguished from its congeners by characteristic shape of paraproct and genital ligula. Additionally, we provide illustrations of the male caudal appendages for all known Caliphaea spp. Odonata, species description, species discovery, Indian Odonata, Dibang valley, Upper Siang District  Caliphaea sinuofurcata sp. nov. Dattaprasad SAWANT, Shantanu JOSHI, Ujwala PAWAR, Viraj NAWGE and Krushnamegh KUNTE. 2025. Caliphaea sinuofurcata sp. nov. (Odonata: Zygoptera: Calopterygidae) from Arunachal Pradesh, India. Zootaxa. 5637(1); 139-154. DOI: doi.org/10.11646/zootaxa.5637.1.6 [2025-05-20] | ||||
| 4:11p | [Herpetology • 2025] Paragehyra tsaranoro • A New microendemic Gecko (Squamata: Gekkonidae: Paragehyra) from the small forest fragments of south-eastern Madagascar
Abstract Historically, herpetological research in Madagascar has largely overlooked small forest fragments outside the country protected area network. Despite substantial declines in species diversity compared to large continuous forests, these fragments continue to sustain diverse herpetological communities and frequently harbour microendemic species. We describe a new gecko belonging to the genus Paragehyra, apparently microendemic to small and isolated forest fragments surrounding the Andringitra Massif in south-eastern Madagascar. Paragehyra tsaranoro sp. nov. is different from its congeneric species based on genetic distances in mitochondrial markers (16S and COI), phylogenetic position, and the lack of haplotype sharing at one nuclear locus (POMC). The new species is also distinguishable from its congeners based on a combination of 14 morphological characters. New genetic and morphological data are also provided for the sympatric P. felicitae and we propose a new assessment of its conservation status within the IUCN Red List. Paragehyra tsaranoro sp. nov. and P. felicitae are mostly found in forest fragments managed by local communities (community-managed reserves) outside legally protected areas. This study highlights the importance of community-based management for the conservation of local herpetofauna, particularly in regions heavily impacted by anthropogenic pressure and largely unsuitable for forest-dwelling species. The findings emphasise the importance of conducting research on small forest fragments, as they are essential for completing the inventory of Malagasy herpetofauna. Key words: Community-based management, deforestation, integrative taxonomy, mitochondrial DNA, morphology, nuclear DNA, reptiles
Paragehyra tsaranoro sp. nov. Francesco Belluardo, Costanza Piccoli, Javier Lobón-Rovira, Ivo Oliveira Alves, Malalatiana Rasoazanany, Franco Andreone, Gonçalo M. Rosa and Angelica Crottini. 2025. A New microendemic Gecko from the small forest fragments of south-eastern Madagascar (Squamata, Gekkonidae, Paragehyra). ZooKeys. 1240: 1-38. DOI: doi.org/10.3897/zookeys.1240.151016 |
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