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Thylacocephalans are enigmatic euarthropods, known at least from the Silurian to the Cretaceous. Despite remaining uncertainties concerning their anatomy, key features can be recognised such as a shield enveloping most of the body, hypertrophied compound eyes, three pairs of raptorial appendages and a posterior trunk consisting of eight up to 22 segments bearing appendages and eight pairs of gills. Well-known for its euarthropod diversity, the La Voulte-sur-Rhône Lagerstätte (Callovian, Middle Jurassic, France) has provided many remains of four thylacocephalan species so far: Dollocaris ingens, Kilianicaris lerichei, Paraostenia voultensis and Clausocaris ribeti. In this paper, we study the type material as well as undescribed material. The re-description of La Voulte thylacocephalans reveals an unexpected diversity, with the description of two new species, Austriocaris secretanae sp. nov. and Paraclausocaris harpa gen. et sp. nov., and of specimens of Mayrocaris, a taxon originally described from Solnhofen Lagerstätten. We also reassign Clausocaris ribeti to Ostenocaris. The reappraisal of La Voulte thylacocephalans also provides important insight into the palaeobiology of Thylacocephala. New key anatomical features are described, such as an oval structure or a putative statocyst, which indicate a nektonic or nektobenthic lifestyle. Finally, we document a juvenile stage for Paraostenia voultensis.
The family Plectopylidae is divided into two subfamilies: Sinicolinae subfam. nov. (included extant genera: Gudeodiscus Páll-Gergely, 2013, Endothyrella Zilch, 1959, Halongella Páll-Gergely, 2015, Sicradiscus Páll-Gergely, 2013, Sinicola Gude, 1899) and Plectopylinae Möllendorff, 1898 (included genera: Chersaecia Gude, 1899, Hunyadiscus Páll-Gergely, 2016, Naggsia Páll-Gergely & Muratov, 2016, Plectopylis Benson, 1860). The Eocene fossil Plectopyloides Yen, 1969 is classified into the Sinicolinae. The Plectopylinae are revised mainly based on historical type and non-type material, and the material of the Florida Museum of Natural History, collected in Thailand in the 1980s. The following species-group taxa are described as new: Chersaecia auffenbergi sp. nov., Chersaecia densegyrata sp. nov., Chersaecia mogokensis sp. nov., Chersaecia reversalis sp. nov., Chersaecia scabra sp. nov., Chersaecia shiroiensis subnagaensis subsp. nov., Hunyadiscus tigrina sp. nov., Naggsia oligogyra sp. nov., Plectopylis crassilabris sp. nov., Plectopylis malayana sp. nov. and Plectopylis thompsoni sp. nov. The genus Endoplon Gude, 1899 is treated as a synonym of Chersaecia. Consequently, the two species classified in Endoplon are members of Chersaecia: Chersaecia brachyplecta (Benson, 1863) comb. nov. and Chersaecia smithiana (Gude, 1897) comb. nov. The genus Plectopylis is redefined, and includes only species with fused anterior and posterior lamellae. Thus, the following species are moved from Plectopylis to Chersaecia: Chersaecia feddeni (Blanford, 1865) comb. nov., Chersaecia goniobathmos (Ehrmann, 1922) comb. nov., Chersaecia leucochila (Gude, 1897) comb. nov., Chersaecia magna (Gude, 1897) comb. nov. and Chersaecia woodthorpei (Gude, 1899) comb. nov. Altogether thirteen species and varieties are moved to the synonymy of valid species: Helix (Plectopylis) brachydiscus Godwin-Austen, 1879 syn. nov., Helix (Plectopylis) ponsonbyi Godwin-Austen, 1888 syn. nov., Plectopylis (Chersaecia) kengtungensis Gude, 1914 syn. nov., Plectopylis (Chersaecia) degerbolae Solem, 1966 syn. nov., Plectopylis lissochlamys Gude, 1897 syn. nov., Helix repercussa Gould, 1856 syn. nov., Plectopylis achatina var. obesa Gude, 1898 syn. nov., Plectopylis achatina var. infrafasciata Gude, 1898 syn. nov. Plectopylis achatina var. venusta Gude, 1898 syn. nov., Plectopylis achatina var. castanea Gude, 1898 syn. nov., Plectopylis achatina var. breviplica Gude, 1898 syn. nov., Plectopylis achatina var. repercussoides Gude, 1899 syn. nov., Plectopylis linterae var. fusca Gude, 1898 syn. nov. Plectopylis (Chersaecia) simplex Solem, 1966 is a subspecies of Chersaecia perarcta (Blanford, 1865), whereas Plectopylis muspratti Gude, 1897 is a subspecies of Chersaecia nagaensis (Godwin-Austen, 1875).
Illustrated Multiple-choice questions (iMCQs) form an integral part of written tests in anatomy. In iMCQs, the written question refers to various types of figures, e. g. X-ray images, micrographs of histological sections, or drawings of anatomical structures. Since the inclusion of images in MCQs might affect item performance we compared characteristics of anatomical items tested with iMCQs and non-iMCQs in seven tests of anatomy courses and in two written parts of the first section of the German Medical Licensing Examination (M1).
In summary, we compared 25 iMCQs and 163 non-iMCQs from anatomy courses, and 27 iMCQs and 130 non-iMCQs from the written part of the M1 using a nonparametric test for unpaired samples. As a result, there were no significant differences in difficulty and discrimination levels between iMCQs and non-iMCQs, the same applied to an analysis stratified for MCQ formats.
We conclude that the illustrated item format by itself does not seem to affect item difficulty. The present results are consistent with previous retrospective studies which showed no significant differences of test or item characteristics between iMCQs and non-iMCQs.
The species richness of the aquatic (non-marine) gastropod family Hydrobiidae Stimpson, 1865 reaches its peak in the European region partly because other areas, such as North Africa, remain to be extensively surveyed. Most of the hydrobiid species described in North Africa have been ascribed to the subfamilies Pseudamnicolinae, Hydrobiinae and the genus Mercuria. Little is known about the presence of other hydrobiid subfamilies. This study examines several specimens of gastropods collected from two springs in Tunisia. Based on a comprehensive literature review and rigorous anatomical and molecular comparisons with known species from North Africa, Europe and Asia Minor of similar morphology, we here describe a new genus, Bullaregia gen. nov., and new species Bullaregia tunisiensis gen. et sp. nov. Although the shell shape of this Tunisian species resembles that of European hydrobiid genera such as Belgrandiella, it differs in other anatomical structures (i.e., penis with a glandular strap-like lobe, and two seminal receptacles, SR1 pedunculate, SR2 sessile and less developed). Using maximum likelihood and Bayesian approaches, phylogenetic relationships inferred from mtCOI sequences point to an independent evolutionary lineage for this new taxon outside Belgrandiella and other known hydrobiid subfamilies.