Dart formation in Helix aspersa (Mollusca,Gastropoda)

Summary Dart formation in Helix aspersa has been investigated by SEM of isolated darts at progressive stages in their development, and by histology of dart sacs at the same times. Dart formation begins at the tip of a tubercle where a small group of epithelial cells secrete an organic material filling a small CaCO₃ cone that is the first mineralized part of the shaft. Subsequent secretory activity by an increasing area of the tubercle epithelium results in an increase in the diameter and anterior lengthening of the shaft. Continued secretion by the tubercle and dart sac epithelium produces the flare and finally the corona. A pattern of deposition is also evident in the fine structure of the mineral. In the shaft and vanes there is an inner layer of spherulitic prismatic structure which is covered by a layer of irregular patches of simple prismatic structure. The outermost layer of the shaft and vanes has a continuous simple prismatic structure. Two layers are present in the flare, an inner granular amorphous layer and an outer spherulitic prismatic layer. The corona consists of a single rarefied prismatic layer. A mechanism of dart formation is suggested that involves two types of organic matrix, calcifying and non-calcifying. Measurements of the calcium content of darts, dart sacs, and collars indicate that the hemolymph is the probable source of calcium for the dart.     

On an unknown lamprey holotype (Petromyzon macrostomus Burmeister 1868) and the genus Exomegas Gill 1883 from South America

The taxonomy of the South American genus Exomegas Gill 1883 has been unstable owing to the unknown status of the type specimen of its type species, Petromyzon macrostomus Burmeister 1868. Here the authors announce the finding of the holotype in the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” ichthyology collection. Whereas Exomegas type species is recognized based on its holotype, Exomegas gallegensis (Smitt 1901) new status is proposed. These preliminary results resolve a century-long taxonomic uncertainty and foster a nomenclatural arrangement for a Southern Hemisphere lamprey genus.     

New information on the postcranial skeleton of Massetognathus ochagaviae Barberena, 1981 (Eucynodontia,Traversodontidae), from the Middle Triassic of Southern Brazil

New postcranial remains of Massetognathus ochagaviae are described based on a new specimen collected at the Dinodontosaurus Assemblage Zone from the Middle Triassic of Southern Brazil. Several isolated teeth collected together with the postcranial skeleton allowed a taxonomic assignation of the specimen to M. ochagaviae. Its postcranial morphology is quite similar to Massetognathus pascuali, especially regarding the morphology of the transverse process of presacral vertebrae (i.e. laminar in the anterior most and rounded in the posterior most presacral vertebrae); humerus (i.e. the head is dorsally deflected with a ‘fan-shaped’ distal end a deltopectoral crest abruptly ending at the middle of shaft); and femur (with a bulbous and dorsomedially inclined femoral head, lesser trochanter which abruptly begins near the intertrochanteric fossa and extending up to the middle of the femoral shaft and the medial condyle more pronounced and ventrally projected than the lateral one). On the other hand, the clavicle of M. ochagaviae is less lateromedially elongated than in M. pascuali.     

Prozostrodon brasiliensis,a probainognathian cynodont from the Late Triassic of Brazil: second record and improvements on its dental anatomy

Probainognathian cynodonts are conspicuous elements of the Assemblage Zones of the Triassic Santa Maria Supersequence in southern Brazil. Within this group, the derived clade Prozostrodontia, in which the crown group Mammalia is included, is taxonomic diverse in the Hyperodapedon and Riograndia AZs. We describe here the second known specimen (CAPPA/UFSM 0123) of Prozostrodon brasiliensis, until now only represented by its holotype. CAPPA/UFSM 0123 includes a right dentary with dentition. As in the holotype of P. brasiliensis, it has four lower incisors, pc4 with conspicuous cusp a, and small cusps b, c, and d, pc5-pc6 of ‘triconodont’ type with cusps a > c > b > d, with continuous lingual cingulum bearing up to six small discrete cusps, length of the lower tooth row more than half the length of the dentary, and relatively deep horizontal ramus of the dentary. The new specimen is about 25% smaller than the holotype and there is not a diastema between the canine and postcanine teeth, indicating its juvenile condition. Based on both known specimens of P. brasiliensis, a discussion on tooth replacement is presented, showing that the adult individual has more postcanine tooth morphotypes than the juvenile one.     

The holotypes of the upper Pleistocene Crocuta crocuta spelaea (Goldfuss, 1823: Hyaenidae) and Panthera leo spelaea (Goldfuss, 1810: Felidae) of the Zoolithen Cave hyena den (South Germany) and their palaeo‐ecological interpretation

The rediscovered holotype skulls of Late Pleistocene Panthera leo spelaea ( Goldfuss, 1810 ) (Felidae) and Crocuta crocuta spelaea ( Goldfuss, 1823 ) (Hyaenidae) from the Zoolithen Cave at Burggeilenreuth, southern Germany, are discussed. The cave became famous mainly due to its rich cave bear bone remains from the late Saalian (OIS 6–8) to Eemian/Weichselian (OIS 3–6) including additionally a third holotype of Ursus spelaeus Rosenmüller, 1794 (Ursidae). The ‘Felis spelaea’ holotype represents an adult male with a strong bite mark on the saggital crest, which was in an early stage of healing. Compared with other European Late Pleistocene lion skulls and skeletons, and with modern African lions, it provides evidence of intraspecific conflict between male Ice Age lions. The holotype of ‘Hyaena spelaea’ is one of several hundred hyena remains from a well‐frequented hyena den cave. The cave was used intensively by Late Pleistocene hyena clans, for collecting lion carcasses in addition to their accustomed prey, as happened in many caves throughout Europe. Ice Age spotted hyena clans might have killed Ice Age steppe lions for many reasons, such as fights over prey and territory, and the protection of cubs, but they did not always scavenge on their carcasses. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 822–831.     

A new species of the sclerorhynchid sawfish Borodinopristis from the Campanian (Upper Cretaceous) of North Carolina,USA

Elasmobranch fossils recovered from Campanian marine exposures at Elizabethtown, Bladen County, NC, include species from at least seven genera of sharks and four genera of batoids. Of particular interest is the recovery of multiple isolated rostral spines from a new sclerorhynchid sawfish, Borodinopristis shannoni, sp. nov. Species of Borodinopristis are known from oral teeth and/or rostral spines (‘rostral teeth’ for some authors). In species known from the latter, the spines differ from those of other sclerorhynchids by the presence of one or more ‘collared’ barbs on the posterior margin of the crown. Unlike the previously described B. schwimmeri, the rostral spines of the new species have well-developed hooked barbs with collars (curved, connected crests) extending asymmetrically onto the dorsal and ventral surfaces of the spine, as well as small, rudimentary barbs. Also unlike B. schwimmeri, the anterior margin of the spine is strongly convex and there is no enamelled collar at the base of the crown. The new species also occurs in the Upper Cretaceous of the Gulf Coastal Plain.     

Molecular phylogeny and biogeography of African diploid barbs, ‘Barbus’, and allies in Africa and Asia (Teleostei: Cypriniformes)

African diploid barbs (‘Barbus’, Clypeobarbus, Barboides, etc.) are a group of small cyprinids with a body size less than 20 cm and widely distributed in drainages across Africa. These species constitute a significant component of African freshwater fish fauna. This study is the first to focus on the molecular systematics and biogeography of African diploid barbs ‘Barbus’ and its African and Asian allies using both mitochondrial and nuclear genes. We test for monophyly of groups, determine interspecific relationships and estimate the time of divergence of 52 species of ‘Barbus’ and allies using two mitochondrial and four nuclear genes. Resulting trees demonstrate that ‘Barbus’ and allies (Systomus, Barboides, Clypeobarbus and African tetraploid barbs) form a strongly supported clade; however, ‘Barbus’ is not resolved as monophyletic. Divergence time analyses identify the separation between Systomus and ‘Barbus’ plus African allies may have occurred around 26 MYA. In addition to the phylogenetic results, these findings highlight the need for more thorough taxonomic and systematic studies on ‘Barbus’ and allies using morphological and additional molecular data and greater taxon sampling, including the type species of the genus Enteromius, ‘Barbus’ potamogalis.     

A new specimen of Teleidosaurus calvadosii (Eudes-Deslongchamps, 1866) (Crocodylia,Thalattosuchia) from the Middle Jurassic of France

Our understanding of early metriorhynchid evolution, the highly specialised pelagic clade of Mesozoic crocodylomorphs, is hampered by the paucity of basal metriorhynchoids and how poorly preserved most of these fossils are. This means the transition from a ‘gharial-like’ body-plan to a ‘pseudo-dolphin-like’ one, which characterises metriorhynchoid evolution, is still poorly understood. Herein the Middle Jurassic taxon Teleidosaurus calvadosii (J.A. Eudes-Deslongchamps, 1866) is re-evaluated. The holotype of T. calvadosii was destroyed during World War Two, as were all referred specimens. All that survived are plaster casts of the holotype. However, a recently discovered specimen from the middle Bathonian of Ecouché, Normandy, France is herein referred to T. calvadosii. This specimen preserves the antorbital region, an incomplete mandible and one cervical vertebra. This specimen is designated as neotype of T. calvadosii. The new specimen allows to re-evaluate the anatomy of T. calvadosii, in particular the antorbital fenestra, which has been misunderstood. Moreover, a comparison is made between the French Middle Jurassic metriorhynchoids Teleidosaurus and Eoneustes. Both genera appear as valid and E. bathonicus is considered to be a nomen dubium.     

Taxonomic and phylogenetic reassessment of the early neotheropod dinosaur Camposaurus arizonensis from the Late Triassic of North America

Abstract: Camposaurus arizonensis, a small theropod dinosaur from the early–middle Norian of Arizona (USA), is widely considered the oldest known neotheropod. However, despite its importance, Camposaurus is the subject of taxonomic and phylogenetic uncertainty and is often considered a nomen dubium, largely because of a fragmentary holotype. We here reassess the holotype of Camposaurus and identify two autapomorphies: the posterior edge of the tibial articular surface for the fibula offset as a sharp and prominent ridge and the absence of an anteriorly expanded medial condyle of the astragalus. We therefore consider Camposaurus to be a valid and diagnostic taxon of basal theropod dinosaur. For the first time, we include Camposaurus in a phylogenetic analysis, which confirms its neotheropod placement and recovers it as a close relative of Coelophysis rhodesiensis within Coelophysoidea sensu stricto. The position of Camposaurus as the oldest neotheropod provides an important calibration point, but necessitates long ghost lineages, indicating that our knowledge of the early evolutionary history of theropod dinosaurs is still patchy. Furthermore, our phylogenetic analysis recovers a polytomy at the base of Neotheropoda, as most parsimonious trees disagree in recovering a monophyletic or paraphyletic ‘traditional’ Coelophysoidea. This suggests that basal theropod phylogeny remains in a state of flux, and the monophyly of ‘traditional’ Coelophysoidea remains an open question.     

On a cranial bony nodular protuberance on Mourasuchus pattersoni Cidade et al. 2017 (Crocodylia,Alligatoroidea) from the late Miocene of Venezuela

Mourasuchus pattersoni, from the late Miocene Urumaco Formation of Venezuela, is the fourth and most recent species described for the genus. The holotype, and only known specimen, is comprised of an almost complete skull with both mandibular rami and several postcranial remains. In ventral view, the right palatine bone has a spherical, nodular bony protuberance located on the anterior portion, near the suture with the maxilla. Unfortunately, we cannot assign a specific diagnosis based only on macroscopic inspection. Its appearance, form and location are compatible with three conditions: torus palatinus, a common benign intraoral bone overgrowth; osteoma, a benign neoplasical overgrowth of the bone; and hamartoma, an overgrowth of normal bone tissue that can only be differed from an osteoma by histological features. While occurrences of torus palatinus or hamartomas are not yet known in the nonhominid vertebrate fossil record, there are previous records of osteomas in fossil vertebrates, including in crocodylians, such as a specimen assigned to ‘Crocodylus sp.’ from the Eocene, aside from several records for living crocodylians. Future studies are needed to uncover an accurate diagnosis of this unusual structure and help increase our knowledge of paleopathology in fossil crocodylomorphs in general, especially in the Caimaninae clade.     

Changes of Skull Proportions in Ontogeny of Barbus canis from Lake Kinneret and of the Lake Tana large-mouthed barbs, Barbus intermedius Complex

Skull proportions of Barbus canis individuals drastically change during their life. Yearlings have skull proportions characteristic for barbs of the NEC phenetic group (sensu Mina et al. 2001 Environ. Biol. Fish. 61: 242–252), but with age become similar to those of the Lake Tana large-mouthed morphotypes which acquire their specific features at 3–7 years old while at earlier ages they have skull proportions of a NEC form identified as 'intermedius' sensu Nagelkerke et al. (1994 Environ. Biol. Fish. 39: 1–21). The large-mouthed Lake Tana barbs originated from an ancestral NEC form through peramorphosis, but in relation to B. canis they are paedomorphic in skull proportions. B. canis supposedly originated from a NEC form as a consequence of an adaptive radiation that took place in western Asia.