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Friday, September 16th, 2022
| Time | Event | ||||
| 5:53a | [Paleontology • 2022] Ibirania parva • A New nanoid titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Brazil
Abstract Titanosaurian sauropods are known to exhibit remarkable body size disparity, with some taxa famed for nearing the zenith of terrestrial vertebrate body size. Here, we describe a new titanosaurian – Ibirania parva gen. et sp. nov. – from the Upper Cretaceous (Santonian–Campanian) São José do Rio Preto Formation of Bauru Basin, n which represents one of the smallest sauropods known to date. The new taxon is diagnosed by seven autapomorphies and had an estimated body length of 5.7 m. Histological and μCT scan analyses showed that this new taxon is represented by skeletally mature individuals, which had attained somatic maturity prior to death. Phylogenetic analyses recovered the new taxon deeply nested within Saltasaurinae, a clade previously known by small-sized forms. Ibirania parva gen. et sp. nov. brings new information indicating that the body size reduction in some titanosaurians could be driven by recurrent ecophysiographical settings, present in South America prior to the diversity peak attained by the group during the Campanian–Maastrichtian. Keywords: Bauru Basin, Growth Patterns, Histology, Nanism, Saltasauridae, São José do Rio Preto Formation    Bruno A. Navarro, Aline M. Ghilardi, Tito Aureliano, Verónica Díez Díaz, Kamila L. N. Bandeira, André G. S. Cattaruzzi, Fabiano V. Iori, Ariel M. Martine, Alberto B. Carvalho, Luiz E. Anelli, Marcelo A. Fernandes and Hussam Zaher. 2022. A New nanoid titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Brazil. Ameghiniana. 59(5); 317-354. DOI: 10.5710/AMGH.25.08.2022.3477  | ||||
| 7:31a | [Botany • 2018] Impatiens hukaungensis (Balsaminaceae) • A New Rheophyte from northern Myanmar [New or Noteworthy Plant Collections from Myanmar (10)]
A new species, Impatiens hukaungensis J. Murata & Nob. Tanaka (Balsaminaceae), is described from Kachin State, northern Myanmar. This species is characterized by decumbent stem, oblanceolate leaves, 2-flowered simple raceme, white with purple mottled dorsal petal and purple dolabriform lateral united petals. Morphological characters, including its 2-flowered raceme and short fusiform capsules, as well as results of molecular phylogenetic analyses based on sequences of plastid atpB-rbcL region, suggest this new species belongs to Impatiens sect. Uniflorae Hook. f. & Thomson. It shows a rheophytic habit and grows along streams with high water-level differences. Key words: Balsaminaceae, Impatiens, Kachin, Myanmar, rheophyte.
Impatiens hukaungensis J. Murata & Nob. Tanaka, sp. nov. Diagnosis: This species has morphologically similar species hitherto described from Myanmar and its adjacent regions based on flowers. It is well characterized by a combination of the following characters; decumbent habit, narrowly oblanceolate leaves, 2-flowered simple raceme, white with purple mottled dorsal petal and purple dolabriform lateral united petals. Etymology: The specific epithet is derived from the type locality, one of the largest nature reserves in Myanmar, Hukaung Valley Tiger Reserve.  Nobuyuki Tanaka, Tetsuo Ohi-Toma, Yu Ito, Mu Mu Aung and Jin Murata. 2018. New or Noteworthy Plant Collections from Myanmar (10): Impatiens hukaungensis (Balsaminaceae), A New Rheophyte from the Northern Region. Journal of Japanese Botany. 93(1); 23–30. http://www.jjbotany.com/pdf/JJB93-1_23-3 | ||||
| 1:37p | [Paleontology • 2022] Opisthiamimus gregori • A nearly Complete Skeleton of A New Eusphenodontian from the Upper Jurassic Morrison Formation, Wyoming, USA, provides insight into the Evolution and Diversity of Rhynchocephalia (Reptilia: Lepidosauria)
Abstract We describe a new, small-bodied rhynchocephalian reptile, Opisthiamimus gregori gen. et sp. nov., from the Upper Jurassic Morrison Formation of Wyoming, USA. Whereas many fossil rhynchocephalians are based on isolated incomplete jaws, the holotype of O. gregori includes most of the skull and postcranium and therefore represents one of the most complete specimens of Rhynchocephalia known from North America. We used micro-computed tomography to examine its skeletal anatomy in detail and to develop a three-dimensional reconstruction of the skull. The skull of O. gregori is similar to that of several non-neosphenodontian rhynchocephalians such as Planocephalosaurus (e.g. large orbits) and Clevosaurus (e.g. parietal parasagittal crests) yet exhibits a suite of other features related to the proal shearing mechanism that becomes increasingly elaborated among more phylogenetically nested taxa such as Sphenodon (e.g. lateral palatine tooth row parallels maxillary tooth row along its entire length, pyramidal dentary teeth with mesial shearing crests). The postcranial skeleton of O. gregori exhibits characteristics typical of a terrestrial rhynchocephalian. Our phylogenetic analyses use a substantially updated data set of 118 characters and 46 taxa, and both maximum parsimony and Bayesian frameworks. Results place O. gregori inside Eusphenodontia but outside Neosphenodontia, and therefore in a key position for contributing to character polarity for more deeply nested clades such as Clevosauridae, Sphenodontidae and Pleurosauridae. We also erect Leptorhynchia taxon nov., composed primarily of aquatically adapted taxa (e.g. Pleurosaurus, Sapheosaurus), which is supported by both cranial and postcranial characters. Because O. gregori is not particularly closely related to the other named Morrison rhynchocephalians (e.g. Opisthias rarus), it increases both the alpha and beta taxonomic diversities within the formation. Similarly, major differences in body size and inferred diet of the Morrison taxa imply considerable concomitant palaeoecological diversity just prior to a major global decline in rhynchocephalian diversity around the close of the Jurassic. Keywords: Rhynchocephalia, Eusphenodontia, Late Jurassic, Morrison Formation, phylogeny, diversity   Systematic palaeontology Lepidosauria Haeckel, 1866 (sensu Evans 1984) Rhynchocephalia Günther, 1867 (sensu Gauthier et al. 1988) Sphenodontia Williston, 1925 Eusphenodontia Herrera-Flores, Stubbs, Elsler & Benton 2018 Opisthiamimus gen. nov. Type and only species: Opisthiamimus gregori sp. nov. Derivation of name: From Opisthias (a genus of the clade Rhynchocephalia) and the Greek ‘mimos’ (μῖμος, meaning mimic; latinized to mimus), referring to the morphological similarities of the dentary and dentary teeth between this taxon and Opisthias. Derivation of name: The species epithet ‘gregori’ recognizes Joseph Gregor, a dedicated Smithsonian volunteer who skillfully prepared the holotype and referred specimens. Diagnosis: Opisthiamimus gregori gen. et sp. nov. is a small-bodied (snout-vent length ∼85 mm) member of Rhynchocephalia based on the presence of four unambiguous synapomorphies: (1) jugal dorsal process extends posteriorly 33% or more of the anteroposterior length of the lower temporal fenestra; (2) lower temporal bar bowed laterally beyond the limit of the adductor chamber; (3) dentary posterior process elongate, reaching articular glenoid level; and (4) splenial absent. Opisthiamimus gregori is a member of Sphenodontia based on the presence of three unambiguous synapomorphies: (1) lacrimal absent; (2) distal marginal tooth attachment acrodont; and (3) weak overlap or imbrication between adjacent distal maxillary teeth. Opisthiamimus gregori is a member of Acrosphenodontia in possessing all 14 unambiguous character states of that major clade: (1) parietal parasagittal crest poorly developed; (2) dentary mentonian process poorly developed; (3) mandibular symphysis oval; (4) anterodorsal tip of dentary with conical, anterodorsally projected successional tooth that does not project beyond anterior margin angle of dentary; (5) mesial notch above dentary symphysis confluent with medial surface of subdental ridge/postsymphyseal lamina; (6) dentary symphysis not split by Meckelian canal; (7) pre-coronoid portion of dentary moderate in length and height; (8) coronoid process of dentary moderately tall; (9) mesial marginal tooth attachment acrodont; (10) distal maxillary teeth with small flanges; (11) mesiodistal length of distal dentary teeth greater than apicobasal height; (12 and 13) distal dentary teeth with a mesiolabial and mesiolingual crest; and (14) pterygoid with two tooth rows. Opisthiamimus gregori belongs to Eusphenodontia based on the presence of a single unambiguous synapomorphy: marginal dentition with conspicuous wear facets. Opisthiamimus gregori is the sister taxon to the Clevosauridae + Neosphenodontia in having a shorter fourth metacarpal relative to the third. 
David G. DeMar Jr., Marc E. H. Jones and Matthew T. Carrano. 2022. A nearly Complete Skeleton of A New Eusphenodontian from the Upper Jurassic Morrison Formation, Wyoming, USA, provides insight into the Evolution and Diversity of Rhynchocephalia (Reptilia: Lepidosauria). Journal of Systematic Palaeontology. 2093139. DOI: 10.1080/14772019.2022.2093139  |
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