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The Asterozoa as traditionally recognized is monophyletic, although ancestry within the Echinodermata is unknown. The asterozoan class Somasteroidea is most readily recognized by presence of series of simple ossicles termed virgals that extend laterally from each ambulacral ossicle. Virgal series reduction to two or three together with ossicular specializations provide apomorphies of the class Stenuroidea (new ranking). Both asteroid-like and ophiuroid-like configurations as well as expressions less suggestive of those of the surviving classes emerged within stenuroids during an early period of diversification. The classes Ophiuroidea and Asteroidea are separate lineages marked by virgal series reduction to a single ossicle and other ambulacral column specializations. It is uncertain whether one or both surviving classes were derived directly from somasteroids or originated through stenuroids. All three of the derived asterozoan classes can be argued to be either monophyletic and thereby justifying class status, or alternatively either paraphyletic or polyphyletic and thereby indicative of multiple plesions; here, monophyletic class-level status is favored for all three.
We report the oldest fossil occurrence of freshwater potamolepid sponges (Demospongiae, Spongillina, Potamolepidae) to date, originating from middle Eocene lake sediments accumulated in the Giraffe kimberlite maar, northern Canada. Sponges are represented by strongyle spicules that are gemmuloscleres. These are described herein as belonging to a new species, Potamophloios canadensis. Because the most similar extant potamolepid sponges inhabit subtropical to tropical water bodies, these observations provide further evidence of biogeographic reorganizations in response to warm high-latitude Eocene paleoclimates.
The development of the trilobite pygidium involves both an articulation process at the frontal part and the formation of new segments at the rear end, and hence the development of the meraspid pygidium entails complicated morphological changes. This study deals with the ontogeny of the Furongian (late Cambrian) ptychaspidid trilobite, Quadraticephalus elongatus (Kobayashi, 1935), from the Hwajeol Formation of the Taebaek Group, Taebaeksan Basin, Korea, with a special focus on the segmentation process during the meraspid pygidial development. Compared to the ontogeny of a ptychaspidid trilobite, Asioptychaspis subglobosa (Sun, 1924), which is assumed to be an ancestral species of Q. elongatus, the convexity of the cranidium of Q. elongatus increased in a slower rate; the yoked free cheek of Q. elongatus splits to form a ventral median suture in a later developmental stage; and, a rim-like ridge, which disappeared in the early holaspid pygidium of A. subglobosa, was maintained in the late holaspid period of Q. elongatus. These morphological changes with growth imply that paedomorphosis was involved in the evolution of Q. elongatus. Eleven stages are recognized for the meraspid pygidial development, which began with an accumulation phase during which the number of segments increased from three to seven, followed by an equilibrium phase with seven segments, and ended up with a depletion phase during which the number of segments within the pygidium decreased to four. During the depletion phase, the pygidial length did not increase or even slightly decreased. The onset of the epimorphic phase, in which the total number of trunk segments does not increase anymore, precedes the onset of the holaspid period, demonstrating that the developmental mode of Q. elongatus is protomeric.
Marrella, a well-known and important component of the Burgess Shale, was only previously found in the Burgess Shale and in the Kaili Biota. An exoskeleton attributed to Marrella is described herein from the lower part of the Balang Formation (Cambrian Series 2) in Paiwu, northwestern Hunan Province, China. It represents not only the third locality where the genus is found, but also the oldest known occurrence of this taxon.
The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled dissent over their status within the arthropods. Pycnogonids figure prominently in recent analyses of anterior limb homologies and ancestral crown-group euarthropod relationships, with support for the concept of Pycnogonida as sister taxon to Euchelicerata now contested by proponents of a more basal position between Radiodonta and all other arthropods. A challenge to further elucidation of their phylogenetic position is the exceptional rarity and disjunct distribution of pycnogonids in the fossil record, due largely to their fragile unmineralized exoskeletons. New fossil discoveries therefore have the potential to add significantly to knowledge of their evolution, paleoecology, and paleobiogeography. Here we report the first known occurrence of fossil pycnogonids from rocks of Ordovician age, bridging a 65 Myr gap between controversial late Cambrian larval forms and a single documented Silurian specimen. The new taxon, Palaeomarachne granulata n. gen. n. sp., from the Upper Ordovician (ca. 450 Ma) William Lake Konservat-Lagerstätte deposit in Manitoba, Canada, is also the first reported from Laurentia. It is the only record thus far of a fossil sea spider in rocks of demonstrably shallow marine origin. Four incomplete, partially disarticulated molts represent a relatively large, robust animal with a series of five segment-like elements in a ‘head' region that does not incorporate the first of four preserved limb-bearing trunk segments. This unique pattern may reflect the plesiomorphic condition prior to complete fusion of anterior ‘head' elements and first trunk segment to form a cephalosoma, as seen in all eupycnogonids. Palaeomarachne granulata is interpreted as occupying a basal stem-group position in the Pycnogonida.
The thickness ratios of shells (=whorl breadth/shell diameter) in the heteromorphic scaphitid ammonoid Scaphites planus (Yabe, 1910) from the lower middle Turonian in the Oyubari and Kotanbetsu areas of Hokkaido, Japan were examined in order to determine their mode of migration. The thickness ratios of S. planus differ significantly between the two localities, which suggest that these different populations did not frequently migrate between the two areas (currently ∼130 km apart, although the actual distance during Turonian is uncertain due to the presence of faults and folds between the two areas). There is no difference in hatchling diameters between the two areas, suggesting that the thickness ratios became manifested after the post-hatchling stage due to limited migration with in a nektobenthic habitat. This study suggests that scaphitid ammonoids became nektobenthic with limited migration at a stage earlier than previously thought (not during the transition from normal to abnormal coiling). The limited migration in scaphitid ammonoids might relate to their higher evolutionary volatility.
Fine-grained sandstones and siltstones of Late Cretaceous to Eocene age in Antarctica and Tierra del Fuego yield an association of well-known shallow-marine trace fossils. Among them stick out complex spreite burrows, which are formally described as Euflabella n. igen. and subdivided into five ichnospecies with different burrowing programs and occurrences. As shown by concentrations of diatoms, radiolarians, foraminifers, and calcispheres in particular backfill lamellae, the unknown trace makers lived on fresh detritus from the surface as well as the burrowed sediment. In some ichnospecies, vertical sections show that the spreite is three-dimensionally meandering in upward direction and that upper laminae tend to rework the upper backfill of the folds underneath. This could mean a second harvest, after cultivated bacteria had time to ferment refractory sediment components, which the metazoan trace maker had been unable to digest before.
The fossils originally assigned to the family Hydrophilidae (Coleoptera, Polyphaga) from the late Miocene locality of Öhningen (southern Germany) are revised. Nine hydrophilid species are recognized, most of them representing the tribe Hydrophilini. Five species are reliably assigned to genera: Hydrochara noachica (Heer, 1847), n. comb. (=Hydrophilus rehmanniHeer, 1847, n. syn.), Hydrobiomorpha braunii (Heer, 1847), n. comb. (=Hydrous escheriHeer, 1862, n. syn.), Hydrobiomorpha heeri n. sp., Hydrophilus spectabilisHeer, 1847 (=Hydrophilus knorrii Heer, 1847, n. syn., =Hydrophilus giganteusHeer, 1862, n. syn.), and Hydrophilus vexatoriusHeer, 1847. Two taxa are treated as Hydrophilini incertae sedis: Hydrophilopsis elongataHeer, 1862, and Hydrous ovalisHeer, 1862. Two species represent Hydrophilidae incertae sedis: Escheria ovalisHeer, 1847 and E. bellaHeer, 1862. The fossil genus HydrophilopsisHeer, 1862 likely represents the modern genera SternolophusSolier, 1834 or HydrobiomorphaBlackburn, 1888, the fossil genus EscheriaHeer, 1847 likely represents some modern genus within the Hydrophilini or Hydrobiusini. Six taxa are excluded from the Hydrophiloidea: Helophorus magnusHeer, 1862, H. exilisHeer, 1862 (possibly belonging to Curculionidae), Hydrobius couloniHeer, 1862 and H. godetiHeer, 1862 (both possibly belonging to Curculionidae: Zygopinae), Hydrophilus braunii var. minorHeer, 1862, and Hydrophilus stenopterusHeer, 1862 (likely a leaf fossil). Our revision revealed a rather high amount of inaccurate family and genus assignments and a moderate amount of species-level synonymy in the original treatment of Öhnigen fauna by O. Heer. The diversity of the hydrophilid beetles in Öhningen is thus lower than previously reported, but still being slightly higher compared to other European Paleogene and Neogene localities.
A new acanthocladiid bryozoan genus from the Permian of the Glass Mountains of Texas, U.S.A., reveals a distinctive morphology and a growth pattern unique amongst members of the extinct stenolaemate Order Fenestrata. Adlatipora fossulata n. gen. n. sp. forms small pinnate expansions with moderately robust main stems and shorter laterally placed pinnae. Colonies developed from small basal discs that exhibit a unique multilayered skeletal structure, from which a circlet of first generation autozooids bud from the ancestrula; these become the bases of branches. In Adlatipora autozooecia are organized into diagonal rows that alternate along branches and are separated into right-handed or left-handed forms. A fossula is developed from the distal margin of autozooecial apertures. Proximal pores are located adjacent to autozooecial apertures and are remnants of fossulae. These pores probably acted as an anal pore providing a passageway for fecal products.
The genus NeseuretusHicks, 1873 is the most abundant trilobite of the Ordovician siltite succession of the Andouillé and Traveusot Formations in the French Armorican massif. The systematics of some species of Neseuretus is still unclear. Armorican and Iberian domains formed part of a distinctive paleobiogeographical province in the Ordovician and, while five Neseuretus species were defined in Iberia that follow each other through time, from the Middle to the Upper Ordovician, only one Neseuretus species, N. tristani, has been identified in the Armorican massif so far. The discovery of new fossil deposits in the Ménez-Belair syncline has led to the identification and re-description of three Neseuretus taxa: Neseuretus avus Hamman, 1977 from the early-middle Darriwilian, Neseuretus tristani (Brongniart in Desmarest, 1817) from the late–middle Darriwilian to late Darriwilian and Neseuretus tardus (Hammann, 1983) from the Darriwilian–Sandbian boundary and early Sandbian. Morphological characters of the cephalon and pygidium were determined that can definitively distinguish the three identified taxa. These results stem from both traditional and geometric (outline and landmark-based) morphometric analyses. The three taxa follow each other through time and constitute a morphological sequence that contributes to improving the stratigraphy of the Middle and Upper Ordovician.
Onset of maturity in trilobites is generally considered to occur when the last trunk segment is released into the thorax, marking the start of the holaspid stage. Here we describe striking morphological changes that occur within the holaspid ontogeny of Lonchopygella megaspina Zhou inZhou et al., 1977, which include the effacement of dorsal furrows, the rapid and complete degeneration of pygidial lateral spines, and the increasing prominence of a pygidial axial spine. These notable changes, which are not coincident with the onset of the holaspid phase, emphasize that the onset of maturity in trilobites should be viewed on a character-by-character basis before assessing whether the exoskeleton as a whole can be described as mature. The holaspid pygidial condition in L. megaspina may represent an intermediate step in an evolutionary transition in the number, form, and allocation of segments in the tsinaniid trunk. Pygidial transition from a dynamically changing complement of segments in the meraspid phase to a static complement in the holaspid phase was accompanied by a marked change in the extent to which segment boundaries defined pygidial structure. Attaining this static complement allowed subsequent pygidial development to emphasize its structure as an integrated unit in which internal segmental boundaries became diffuse, a continuous margin to become prominent, and an elongated terminal spine, first evident at onset of epimorphic growth, to develop allometrically. Trilobite body development suggests that while the segmented construction placed constraints on how morphology varied, the influence of these constraints diminished following completion of thoracic segment construction. Selective premium for a distinct posterior tagma might favor the early ontogenetic acquisition of such a structure, and could have been a driver of the repeated trend toward caudalization witnessed among derived trilobite clades.
Samples from outcrops of the Miocene Solimões and Barreiras formations from the central and coastal Amazon regions of Brazil were analyzed palynologically. Assemblages of fossil fungi were identified, and are described herein, and their relevance to paleoenvironmental and paleoclimatic studies in tropical regions discussed. The fungal assemblage comprises four spore groups, 19 species belonging to 12 genera. Additionally, two new species are proposed. The samples from the Solimões Formation contain the following taxa: Mediaverrunites elsikii, Mediaverrunites mulleri, Monoporisporites sp., Fusiformisporites crabbii, and Multicellites cingulatus. The presence of these suggests river channel margins colonized by freshwater vegetation, where seasonal fluctuations of water table and rainfall produce wetter substrates. The samples from the Barreiras Formation showed higher species and generic diversity than those from the Solimões Formation with Hypoxylonites minutus, Hypoxylonsporites ater, Hypoxylonites sp., the new species Inapertisporites multiporus n. sp., Pluricellaesporites regularis, Lacrimasporonites levis, Monoporisporites annulatus, Spirotremesporites simplex, Dyadosporites novus, Dyadosporites sp., and Multicellaesporites attenuates. All of these correspond to parasitic fungi from a range of from tropical wetlands. Spegazzinites sp. and Dicellaesporites aculeolatus, good indicators of marine influence and mangrove presence, were also identified in the samples from the Barreiras Formation. Furthermore, the fungal spore taxa Inapertisporites multiporus, Mediaverrunites elsikii, Mediaverrunites mulleri, Pluricellaesporites regularis, and Spirotremesporites simplex serve as stratigraphic indicators when combined with miospore index taxa such as Crassoretitriletes vanraadshooveni, Grimsdalea magnaclavata and Fenestrites longispinosus indicating a Miocene age for these sediments in the Amazon region.
A new arthropod, Kootenichela deppi n. gen. n. sp., is described from the Stanley Glacier exposure of the middle Cambrian (Series 3, Stage 5) Stephen Formation in Kootenay National Park (British Columbia, Canada). This taxon possesses a number of primitive arthropod features such as an elongate, homonomous trunk (consisting of at least 29 segments), poorly sclerotised trunk appendages, and large pedunculate eyes associated with an anterior (ocular) sclerite. The cephalon encompasses a possible antenna-like appendage and enlarged raptorial appendages with a bipartite peduncle and three spinose distal podomeres, indicative of megacheiran (“great-appendage” arthropod) affinities. The relationships of megacheirans are controversial, with them generally considered as either stem-euarthropods or a paraphyletic stem-lineage of chelicerates. An extensive cladistic analysis resolved Kootenichela as sister-taxon to the enigmatic Worthenella cambria from the middle Cambrian (Series 3, Stage 5), Burgess Shale Formation in Yoho National Park (British Columbia), which is herein reinterpreted as a megacheiran arthropod. Based on their sister-group relationship, both taxa were placed in the new family Kootenichelidae, to which Pseudoiulia from the Chengjiang biota is also tentatively assigned. All of these taxa possess an elongate, multi-segmented body and subtriangular exopods. This family occupies a basal position within a paraphyletic Megacheira, the immediate outgroup of Euarthropoda (crown-group arthropods). The resultant topology indicates that analyses that have resolved megacheirans as stem-chelicerates have done so because they have rooted on inappropriate taxa, e.g., trilobitomorphs and marrellomorphs.
A revision of the Cenozoic Ampullinidae and Naticidae from a wide range of localities and stratigraphic units in Patagonia revealed the occurrence there of thirteen species referable to these families. Ampullinid species described are Tejonia? tapia (Feruglio, 1935); Tejonia arroyoensis n. sp. and Pseudamaura dubia (Petersen, 1946). Naticids are represented by the following valid species: “Natica”entrerianaBorchert, 1901; Euspira patagonica (Philippi, 1845); Notocochlis borrelloi (Brunet, 1995); Bulbus subtenuis (Ihering, 1897); Polinices santacruzensisIhering, 1907; Polinices puntarenasensisIhering, 1907; “Polinices”ortmanniIhering, 1907 (nomen dubium); Polinices mina n. sp.; Glossaulax secundum (Rochebrune and Mabille, 1885); and Darwinices claudiae n. gen. n. sp.