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Friday, August 22nd, 2025
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| 1:03a | [Botany • 2025] Erythrostemon guatemalensis (Leguminosae: Caesalpinioideae) • A New Endangered tree Species from the Pacific Slope highlands of Guatemala
Summary A new tree species, Erythrostemon guatemalensis Eisermann & G.P.Lewis (Leguminosae: Caesalpinioideae: Caesalpinieae), is described and illustrated based on morphological characters. The species occurs in montane, seasonally dry, tropical forest in the Pacific slope highlands of Guatemala, Departamento Sacatepéquez. Phenology data is derived from four years of field observations. Erythrostemon guatemalensis is morphologically similar to E. nicaraguensis (G.P.Lewis) Gagnon & G.P.Lewis but differs in several character details. The two species are allopatrically distributed with a distance of 450 km between their population localities and they occur at different elevations. Molecular analyses place this new taxon into a species group with E. exostemma (Sessé & Moc. ex DC.) Gagnon & G.P.Lewis, E. hughesii (G.P.Lewis) Gagnon & G.P.Lewis and E. nicaraguensis. Key Words: Caesalpinia group, Central America, endemism, Fabaceae, pine-oak forest, montane seasonally dry tropical forest, volcanic highlands 
Erythrostemon guatemalensis Eisermann & G.P.Lewis sp. nov. Type: Guatemala, Departamento Sacatepéquez, Municipio de Antigua Guatemala, Finca El Pilar ...  Knut Eisermann, Gwilym P. Lewis, Félix Forest, Edeline Gagnon, Laszlo Csiba, Javier Aju and Juliet Williamson. 2025. Erythrostemon guatemalensis (Leguminosae: Caesalpinioideae: Caesalpinieae), A New Endangered tree Species from the Pacific Slope highlands of Guatemala. Kew Bulletin. DOI: doi.org/10.1007/s12225-025-10300-0 [05 July 2025] | ||||||||||
| 4:07a | [PaleoMammalogy • 2025] Megabalaena sapporoensis • A New member of a large and archaic balaenid (Mysticeti: Balaenidae) from the Late Miocene of Sapporo, Hokkaido, Japan partly fills a gap of Right Whale Evolution
ABSTRACT The family Balaenidae (right whales) includes two genera and four extant species, all of which are endangered and giant animals measuring approximately 17 to 20 m in length. The history of the Balaenidae spans about 20 million years. Several small sized extinct balaenids from the Pliocene have been identified. However, half of this history remains unknown owing to a 9-million-year gap from 15.2 to 6.1 m.y.a. in the fossil record. A well-preserved fossil balaenid skeleton, designated SMAC 2731, from the Late Miocene approximately 9 m.y.a. in Sapporo, Hokkaido, Japan, is named as Megabalaena sapporoensis gen. et sp. nov. This specimen preserves the skull, periotics in situ, tympanic bullae, right mandible, basihyal-thyrohyal, right stylohyal, sternum, seven cervical vertebrae, nine thoracic vertebrae, and 16 more posterior vertebrae, rib fragments, scapulae, and left forelimb elements. All preserved vertebral epiphyses are fused, indicating that SMAC 2731 was physically mature. Notably, M. sapporoensis can be distinguished from other balaenids by its excavated orbit in dorsal view with a large postorbital process, dorsoventrally high anterior part of the involucrum of the tympanic bulla, long compound posterior process, high coronoid process and deeper subcondylar furrow of the mandible, incipient cervical fusion (C2+C3 only), and its slender forelimb bones, including the humerus, radius and ulna. Based on a bizygomatic width of 2.2 m, the estimated total length of the holotype of M. sapporoensis is 12.7 m. Overall, M. sapporoensis indicates that balaenids diversified prior to the Late Miocene. Keywords: Balaenidae; new genus; new species; Tortonian; gigantism; Japan
CETACEA Brisson, 1762 NEOCETI Fordyce and de Muizon, 2001 MYSTICETI Gray, 1864 CHAEOMYSTICETI Mitchell, 1989 BALAENIDAE Gray, 1825 Megabalaena gen. nov Type species. Megabalaena sapporoensis sp. nov. Etymology. The generic name, Megabalaena , is named derived from ancient Greek megas meaning great, large and mighty, and the type genus name of the family Balaenidae. Megabalaena sapporoensis sp. nov. Locality and horizon. SMAC 2731 was found at a riverbed of Toyohira River in Sapporo City, Hokkaido, Japan, by Kazuhisa Mori on 10 October 2008: Latitude 42°58'1.24"N, longitude 141°13'18.01"E (Figure 1 and Figure 2). SMAC 2731 was found from the upper part of the Toyama Formation. At the fossil area, the diatomaceous siltstone Toyama Formation is distributed. Diatomaceous siltstone of the Toyama Formation is exposed at the type locality ... Etymology. Named after the fossil locality, Sapporo City. Diagnosis. Megabalaena sapporoensis is a member of the Balaenidae because it has a combination of these character states such as a posteriorly pointed anterior edge of the supraorbital process lateral to the ascending process of the maxilla with the skull in dorsal view (Character 31, state 0), laterally oriented postorbital process in dorsal view (Character 38, state 1), confluent posterior border of the zygomatic process of the squamosal and exoccipital in dorsal view (Character 67, state 1), dorsoventrally higher than long parietal in lateral view (Character 76, state 1), anterolaterally directed zygomatic process of the squamosal in dorsal view (Character 86, state 2), distinctly higher than long squamosal including the zygomatic and postglenoid processes (Character 92, state 1), short squamosal fossa (Character 96, state 1), foramen pseudovale opening posteriorly between the squamosal and pterygoid (Character 118, state 1), and posteriorly diverging basioccipital crests in ventral view (Character 125, state 0). ..
Yoshihiro Tanaka, Toshiyuki Kimura, Tatsuya Shinmura, Hiroto Ohira, and Hitoshi Furusawa. 2025. A New member of a large and archaic balaenid from the Late Miocene of Sapporo, Hokkaido, Japan partly fills a gap of Right Whale Evolution. Palaeontologia Electronica. 28(2): a37. DOI: doi.org/10.26879/1549 [August 2025]  Plain Language Abstract: The right whale family (Balaenidae) includes four extant species in two genera such as the Balaena and Eubalaena, all of which are endangered and giant animals about 17 to 20 m in length. The history of the right whale group spans about 20 million years. Several small-sized extinct fossil right whales from the Pliocene have been identified. However, half of this history remains unknown owing to a 9-million-year gap from 15.2 to 6.1 million years ago in the fossil record. A well-preserved fossil right whale skeleton (SMAC 2731) from the late Miocene (approximately 9 m.y.a.) of Sapporo, Hokkaido, Japan, is named as the new species Megabalaena sapporoensis. This specimen preserves the skull, ear bones, right lower jaw, hyoid bones, sternum, back bones, ribs, scapulae, and left forelimb elements. All preserved vertebral epiphyses are fused, indicating that SMAC 2731 was physically mature. Notably, M. sapporoensis can be distinguished from other balaenids by its large postorbital process of the skull and unfused cervical vertebrae, except for the axis and third cervical vertebra, and its slender forelimb long bones, including the humerus, radius and ulna, which are about twice slenderer than these of extant balaenids. Based on a bizygomatic width of 2.2 m, the estimated total length of the holotype of M. sapporoensis is 12.7 m. Overall, M. sapporoensis enhances our understanding of balaenid diversity, suggesting that it expanded earlier than the late Miocene. | ||||||||||
| 10:18a | [Paleontology • 2025] Istiorachis macarthurae • The Origins of Neural Spine Elongation in iguanodontian dinosaurs and the Osteology of A New sail-back styracosternan (Ornithischia: Iguanodontia) from the Lower Cretaceous Wealden Group of England
Abstract The Wealden Group of southern England was deposited during the late Berriasian to early Aptian interval. It records a critical time in the development of iguanodontian dinosaur diversity, which increased from low levels during the Jurassic to higher levels in the Aptian and Albian. A new iguanodontian dinosaur, Istiorachis macarthurae gen. et sp. nov. from the Wessex Formation (Wealden Group) of the Isle of Wight, exhibits hyperelongation of the dorsal and caudal neural spines, suggesting that it possessed a possible sail structure. Ancestral state reconstruction for the relative height of dorsal neural spines in iguanodontians demonstrates that modest elongation began with Ankylopollexia in the Late Jurassic and elongation became established during the Berriasian stage of the Early Cretaceous, albeit with widely disparate values. Hyperelongation of neural spines occurred more sporadically throughout the Cretaceous, being recorded most often in the Barremian and early Aptian. Possible explanations for neural spine elongation in Ankylopollexia include biomechanical advantage, perhaps related to greater mass and a locomotory shift towards quadrupedalism, and visual signalling driven either by sexual selection or species recognition, or both. The function of elongate neural spines was probably pluralistic and differed in different taxa. No single explanation fully supports the variation seen throughout the Cretaceous. Keywords: Iguanodontia, diversity, sexual signalling, Isle of Wight, ossified tendons, Barremian  SYSTEMATIC PALAEONTOLOGY DINOSAURIA Owen 1842 ORNITHISCHIA Seeley 1888 ORNITHOPODA Marsh 1881 IGUANODONTIA Baur 1891 ANKYLOPOLLEXIA Sereno 1986 STYRACOSTERNA Sereno 1986 Genus Istiorachis nov. Derivation of name: The name is derived from the Ancient Greek words ἱστίον (istion), meaning a sail, and ῥάχις (rachis), the spine or backbone. It refers to the probable sail-back appearance of the dinosaur. Istiorachis macarthurae sp. nov. Derivation of name: The species name honours Dame Ellen MacArthur, an English sailor who in 2005 set a world record for the fastest solo non-stop voyage around the world on her first attempt and who also founded the Ellen MacArthur Cancer Trust for young people on the Isle of Wight. Holotype: MIWG 6643 is a partial skeleton composed of the following elements: one cervical vertebra, eight dorsal vertebrae, three dorsal rib heads, a partial sacrum, seven caudal vertebrae, both pubes and both ischia. Location & horizon: MIWG 6643 was excavated by the late Mr Nicholas Chase from the ‘Black Band’ (bed L11 in Stewart 1978), a plant debris bed cropping out c. 100 m east of Grange Chine, lying above the Grange Chine Sandstone in the Wessex Formation. The site is a c. 1.5-m-thick bed that has occasionally yielded dinosaur remains, including IWCMS 1997.550, the holotype specimen of the tyrannosauroid theropod Eotyrannus lengi (Hutt et al. 2001; Naish & Cau 2022). Unfortunately the excavation site was poached and an unknown amount of the skeleton was taken before collection could be completed. Diagnosis: Istiorachis macarthurae differs from all other iguanodontians by possessing one autapomorphy, namely two anterior parasagittal tuberosities present on the ventral surface of a posterior dorsal vertebra, marking a change from vertebrae with a ventral keel to a flat surface. A posterior cervical vertebra has a damaged anteroventral process at the base of the neural spine, potentially representing a second autapomorphy. Istiorachis macarthurae also possesses the following features, which, although not unique to the taxon, occur in a unique character combination. An interpostzygapophyseal fossa and tubular cavity is located between the origin of the postzygapophyses and above the neural canal: a similar fossa is also seen in ...
Jeremy A. F. Lockwood, David M. Martill and Susannah C. R. Maidment. 2025. The Origins of Neural Spine Elongation in iguanodontian dinosaurs and the Osteology of A New sail-back styracosternan (Dinosauria, Ornithischia) from the Lower Cretaceous Wealden Group of England. Papers in Palaeontology. DOI: doi.org/10.1002/spp2.70034 [21 August 2025] |
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