The largest known member of the mammalian order Multituberculata is the taeniolabidid Taeniolabis, which is known from Puercan (early Paleocene) localities in northern New Mexico, Utah, Montana, and southern Saskatchewan. A locality in the Ludlow Formation of southeastern Montana has produced remains of a new species, T. lamberti n. sp., which is based on a well-preserved dentary with teeth. Isolated teeth from the Tullock Formation of northeastern Montana are referred to T. lamberti n. sp. and Taeniolabis sp.

Taeniolabis triserialis, known exclusively from the San Juan Basin, New Mexico, is shown to be a junior synonym of T. taoensis. Taeniolabis sulcatus, the type species of the genus, is recognized as a nomen dubium and is synonymized with T. taoensis based on general morphology and occurrence in the same stratigraphic unit and collecting area (lower part of the Nacimiento Formation, San Juan Basin, New Mexico). The name T. taoensis is retained for this taxon in the interest of nomenclatorial stability. These synonymies limit to one the number of species of Taeniolabis recognized in the San Juan Basin, New Mexico. It is proposed that T. taoensis be designated the new type species of the genus Taeniolabis.

Fossil isopod crustaceans in the suborder Phreatoicidea have a known stratigraphic range from the Carboniferous to the Jurassic. Until now, all Mesozoic records of this group were thought to occur in fresh water habitats. A new phreatoicidean isopod fossil of the Triassic Luoping marine fauna, Yunnan Province, China, is described. The new species, based on several exceptionally complete specimens, is assigned to the genus Protamphisopus Nicholls and the family Amphisopidae Nicholls. This Chinese record is the first report of a Mesozoic-age phreatoicidean isopod outside of Gondwanan terranes, requiring a revision of known biogeographic patterns of the Phreatoicidea. Whether this record is from a marine habitat or is the result of a secondary deposition is not certain. Sottyella Racheboef, Schram and Vidal from the Carboniferous (Stephanian) Lagerstätte of Montceaules-Mines that was assigned to this suborder may be a decapod. Therefore, it has no relationship to this new species.

The Cretaceous Huitrín Formation in west-central Argentina records the final connection of the Neuquén Basin to the Pacific Ocean. This formation is comprised of a variety of continental to marginal-marine sediments deposited behind an Andean volcanic arc under warm, arid paleoclimatic conditions. Here we focus on a bivalve fauna from carbonate ramp deposits within the Barremian La Tosca Member of the Huitrín Formation. This fauna is very abundant and widely distributed within the basin but, surprisingly, it has not yet been studied in detail. In addition, paleoenvironmental affinities remain unresolved, with the fauna variously interpreted as having freshwater, brackish, and marine affinities. We studied the fauna's taxonomy and paleoecology based on more than 500 specimens collected at ten fossil localities in combination with new field observations. The bivalve assemblage was recorded from middle to outer carbonate ramp deposits and is composed of five taxa of marine affinity: Phelopteria huitriniana n. sp., Isognomon cf. I. nanus (Behrendsen), Placunopsis? pichi n. sp., Anthonya jarai n. sp., and Argenticyprina mulensis n. gen. n. sp.; the first three may be regarded as eurytopic and/or opportunistic. Reduced diversity, low evenness, overall small size (length <4 cm), thin shells, eurytopic or opportunistic life strategies, and high endemism point to a restricted marine setting for the La Tosca Member. The most important limiting factors likely were low primary productivity and fluctuating salinity and temperature, as conditions inferred for the unit include high evaporation rates combined with low continental runoff and reduced rainfall. Thick evaporite deposits below and above La Tosca Member and thin intercalated gypsum beds support a restricted, hypersaline setting.

The Holocystites Fauna is an enigmatic group of North American diploporitans that presents a rare window into unusual middle Silurian echinoderm communities. Multiple systematic revisions have subdivided holocystitids on the basis of presumed differences in oral area plating and respiratory structures. However, these differences were based on a fundamental misunderstanding of the homologous elements of the oral area and the taphonomic process; taphonomic disarticulation of the oral area formed the basis for the erection of Pentacystis and Osgoodicystis as separate genera, and Osgoodicystis is interpreted as the junior synonym of Pentacystis. Holocystitids show a conservative peristomial bordering plate pattern that is shared among all described genera. The peristome is bordered by seven interradially positioned oral plates as is typical for oral plate–bearing blastozoans. A second open circlet of facetal plates lies distal to the oral plates; five of these facetal plates bear facets for feeding appendages (lost on the A ambulacrum in some taxa), while two lateral facets (present in all taxa except Pustulocystis) do not. Holocystitid taxa show minor modifications to this basic peristomial bordering plate pattern. As thecal morphologies are highly variable within populations, taxonomic revision of holocystitids is based on modifications of the plating of the oral area.

Four species of rhinoceros occur together in the Barstovian (middle Miocene) faunas of southeast Texas, a unique situation in the Miocene of North America. Two are assigned to normal contemporary High Plains species of Aphelops and Teleoceras, and two to dwarf species of Peraceras and Teleoceras. The dwarf Peraceras is a new species, P. hessei. The dwarf Teleoceras is assigned to Leidy's (1865) species “Rhinoceros” meridianus, previously referred to Aphelops. “Aphelops” profectus is here reassigned to Peraceras.

The late Arikareean (early Miocene) Derrick Farm rhino, erroneously referred to “Caenopus premitis” by Wood and Wood (1937), is here referred to Menoceras arikarense. Menoceras barbouri is reported from the early Hemingfordian (early Miocene) Garvin Gully local fauna of southeast Texas. The rhinos from the early Clarendonian Lapara Creek Fauna are tentatively referred to Teleoceras cf. major.

The three common genera of middle late Miocene rhinoceroses of North America (Aphelops, Peraceras, Teleoceras) are rediagnosed. Aphelops and Peraceras are more closely related to the Eurasian Aceratherium and Chilotherium (all four together forming the Aceratheriinae) than they are to the American Teleoceras. Contrary to Heissig (1973), Teleoceras is more closely related to the living rhinoceroses and their kin (together forming the Rhinocerotini) than it is to the Aceratheriinae.

Rosette-shaped problematica are relatively common structures in the Phanerozoic rock record. Historically, they have been accorded a variety of names and documented from various shallow to deep marine environments. Unfortunately, the detailed interpretation of many such structures as biogenic (trace fossils, medusoids, or other body fossils; see, for example, Häntzschel, 1970, 1975) or nonbiogenic (for example, Pickerill and Harris, 1979) in origin still remains to be resolved. However, a detailed analysis of one such structure by Fürsich and Bromley (1985), namely Dactyloidites Hall, 1886, convincingly demonstrated its biogenic origin. The distinctive morphology of Dactyloidites and its synonyms was interpreted by Fürsich and Bromley (1985) to result from successive probings of an essentially stationary deposit-feeding, worm-like organism, possibly possessing a proboscis, to produce a rosetted, vertical spreiten with a centrally located, vertical or subvertical shaft.

Purgatorius titusi, represented by 51 teeth and jaw fragments, is described from the lower Paleocene Bear Formation of the Crazy Mountains Basin in south-central Montana. Several synapomorphies, including a weak postprotocingulum and mesial inflection of molar trigonids, are indicative of the taxon's “plesiadapiform” affinities. Other features, such as wider stylar shelf and a less squared lingual outline on upper molars, are more primitive than those of Purgatorius unio, heretofore the earliest occurring species of well-represented primatomorphs.

The Arco Hills Formation contains abundant lingulate, strophomenate, and rhynchonellate brachiopods, echinoderms, corals, bryozoans, and rare vertebrate and trilobite fossil fragments. Fossils are equally abundant in carbonate and siliciclastic units; however, silicified brachiopods are limited to carbonate lithologies which occasionally have minor amounts of siliciclastic sediment. These silicified brachiopods were extracted for taxonomic, taphonomic, and paleoecologic description. Chesterian brachiopod assemblages of the Cordilleran region are poorly described and this work represents the only systematic treatment of Chesterian macrofossil assemblages in Idaho. Fifteen genera (23 species) of brachiopods are presented from Arco Hills Formation, including two new species: Anthracospirifer arcoensis and Composita idahoensis, described herein.

Phacopida from upper Whiterock (Lower Caradoc) horizons in the Las Aguaditas Formation of San Juan Province, Argentina, include the calymenid Platycalymene trapezoidalis (Baldis and Pöthe, 1995) and the encrinurids Frencrinuroides edseli new species, Lasaguaditas oweni new genus and species, and Walencrinuroides? new species A. Sulcocalymene Baldis and Pöthe, 1995, a purported subgenus of Flexicalymene, is a junior subjective synonym of Platycalymene Shirley, 1936. Platycalymene is now known from Avalonia, Baltica, Laurentia (Scotland), and the Precordillera. Emending the cladistic analysis of Ordovician Encrinurinae by Lespérance and Desbiens (1995), the monophyly and membership of Frencrinuroides and Walencrinuroides are ambiguous. Frencrinuroides edseli is closely related to species from eastern Laurentia. Lasaguaditas new genus is superficially cybelinid-like in some respects but shares several derived characters with the Encrinurinae. All three encrinurinid species in the Las Aguaditas Formation possess two instars in the protaspid period, a general pattern in Ordovician encrinurinid ontogeny.

Three successive species of Neohipparion are recognized from the Gulf Coastal Plain: N. affine from the early Clarendonian Lapara Creek Fauna of Texas; N. trampasense from the very late Clarendonian and early Hemphillian of Florida; and N. eurystyle from the late early and late Hemphillian of Florida. Numerous specimens from the Love Site, Alachua County, Florida, as well as from other faunas of similar age from Florida, Kansas, and Nebraska (e.g., the Xmas-Kat Quarries), are referred to N. trampasense. This species is ancestral to all later species of Neohipparion, as it shares with them many advanced dental characters, but often in a rudimentary or intermediate form. Five valid species constitute the monophyletic genus Neohipparion, which ranges from the late Barstovian to the latest Hemphillian (late Miocene through earliest Pliocene) in North America. A close phylogenetic relationship between Neohipparion and “Merychippus” republicanus and/or Pseudhipparion is proposed based on similarities of cranial and dental features.

Here we reconstruct a new tubular, serially divided organism with a bilateral morphology from the Ediacaran of South Australia. The organism, Plexus ricei new genus new species, was a broadly curving tube that resided on the Ediacaran seafloor. Plexus ricei individuals range in size from 5 to 80 cm long and 5 to 20 mm wide, and are comprised of two main components: a rigid median tubular structure and a fragile outer tubular wall. Plexus ricei is preserved as an external mold on bed soles, and as a counterpart cast on bed tops in sandstones interpreted to represent deposition between storm and fairweather wave-base. The phylogenetic affinities of P. ricei are uncertain; P. ricei symmetry implies a bilaterian origin, but a lack of defined anterior and posterior ends precludes definitive assignment.

More than five thousand specimens of nine species of articulate brachiopods from the Waynesville-Liberty Formation (Late Ordovician) of southeastern Indiana were analyzed for the percentage of specimens disarticulated and the ratio of pedicle to brachial valves. Among biconvex species, the rhynchonellid Hiscobeccus capax displayed the highest ratio (2.66) of articulated to disarticulated specimens, an observation attributed to its cyrtomatodont hinge. The six orthid species from the same assemblages have much higher frequencies of disarticulated valves and deltidiodont hinges, which did not necessitate breakage of the teeth or sockets in order to disassociate the valves. Platystrophia clarksvillensis has the highest percentage of articulated specimens among the orthids, a fact attributed to the hydrodynamic stability of this species and the interlocking of the valves by the plicae around the commissure. The largest of the three concavo-convex taxa, Rafinesquina ponderosa, has the highest ratio of articulated to disarticulated specimens (3.03) and requires the fastest current velocities to transport the shells based on flume experiments.

Additionally, the deltidiodont hinge of R. ponderosa is more complex than those of Strophomena planumbona and Leptaena richmondensis, which might have increased the amount of jostling necessary to disarticulate the valves. The infrequency of brachial valves of H. capax, Hebertella occidentalis, Plaesiomys subquadrata, S. planumbona, and R. ponderosa and the pedicle valves of L. richmondensis probably reflects the comparative mechanical weaknesses of these valves given the high frequency of fragments in the biosparites, which resemble tempestites. Pedicle valves of orthids and rhynchonellids are up to 10 times thicker posteriorly relative to corresponding points on the opposite valve. Brachial valves of L. richmondensis are more than four times thicker anteriorly relative to the pedicle valve. The occurrence of posterior remnants of the fragmented brachial valve still hinged to the unfractured pedicle valve support the idea that the thinner valve is mechanically much weaker.

Although Ptychodus teeth are well known in Late Cretaceous marine deposits in North America and Europe and a few specimens with jaw elements have been discovered, the taxonomic position of the shark genus Ptychodus is enigmatic due to the lack of preservation of diagnostic material other than teeth. These sharks possessed a pavement dentition suited to a diet of hard-shelled macroinvertebrates (durophagy), leading several studies to variously describe Ptychodus as a batoid, a hybodont shark, or a selachimorph. Members of the Selachimorpha share one dental synapomorphy, a triple-layered enameloid (TLE) consisting of an outer shiny-layered enameloid (SLE) of randomly oriented hydroxyapatite crystallites, a middle layer of parallel-bundled enameloid (PBE), and an inner layer of tangled-bundled enameloid (TBE). Batoids and hybodonts both have teeth with single crystallite enameloid (SCE). We examined teeth from Ptychodus collected from the Lincoln Limestone of the Greenhorn Formation of Barton County, Kansas, and compared their enameloid ultrastructure with that of a Carboniferous hybodontiform and the Cretaceous lamniform shark Squalicorax curvatus Williston, 1900. Scanning electron microscopic examination of Ptychodus shows that crystallite bundling in the form of a TLE is evident in these teeth. The PBE is most apparent at transverse enameloid ridges of Ptychodus teeth. Columns of dentine penetrate into the tooth enameloid, and the crystallites near the dentine are randomly oriented. These observations bolster the argument that Ptychodus is a genus of highly specialized selachimorph shark, rather than a hybodont or batoid.

Extant medusozoans (phylum Cnidaria) are dominated by forms showing tetraradial symmetry, but stem-group medusozoans of early Cambrian age collectively exhibit tetra-, bi-, penta-, and hexaradial symmetry. Moreover, the developmental and evolutionary relationships between four-fold and other types of radial symmetry in medusozoans remain poorly understood. Here we describe a new hexangulaconulariid, Septuconularia yanjiaheensis new genus new species, from Bed 5 of the Yanjiahe Formation (Cambrian Stage 2) in the Three Gorges area of Hupei Province, China. The laterally compressed, biradially symmetrical periderm of this species possesses 14 gently tapered faces, the most of any hexangulaconulariid described thus far. The faces are bordered by longitudinal ridges and crossed by short, irregularly spaced transverse ribs. Longitudinally, the periderm consists of three regions that probably correspond, respectively, to an embryonic stage, a transient juvenile stage, and a long adult stage. Septuconularia yanjiaheensis may have been derived from six-faced Hexaconularia (Fortunian Stage), which is morphologically intermediate between Septuconularia yanjiaheensis and Arthrochites. Furthermore, conulariids sensu stricto, carinachitids, and hexangulaconulariids may constitute a monophyletic group united by possession of an organic or organophosphatic periderm exhibiting longitudinal (corner) sulci, a facial midline, and offset of transverse ribs along the facial midline.

UUID: http://zoobank.org/01a972aa-aef3-4eef-a9a5-c2d8c3dda615

Five Jurassic through Oligocene sea stars are described; all are assignable to modern genera and two (Tethyaster jurassicus; Mediaster hayi) represent new species. Tethyaster and Pseudarchaster are morphologically similar but represent separate orders; occurrence of both in Jurassic sediments suggests close common ancestry. Many post-Paleozoic sea stars appear enduring, perhaps because of broad ecological tolerances and construction; the fossils described here probably are not unique as asteroid living fossils.

A collection of small crinoids and crinoid debris from the Ashgill (Rawtheyan?) of Cnwce, near St. Clears, Dyfed, southwest Wales includes numerous crowns of Aithriocrinus strahani n. gen. and sp. incertae familiae, an indeterminate 10–armed camerate(?) and an indeterminate multiple-armed camerate. Aithriocrinus strahani was previously considered to be a cincinnaticrinid, but it is undoubtedly dicyclic and therefore a cladid. This is the only diverse fauna of complete crinoids known from the Welsh Ashgill.

The monobathrid camerate Xenocrinus S. A. Miller is easily recognized from its disarticulated columnals, which are square in outline. Xenocrinus columnals are now recognized from three Hirnantian localities in Wales. Xenocrinus became extinct during the Hirnantian and not at the Rawtheyan–Hirnantian boundary, as has been suggested on the basis of crown material.

Eight species of brachyuran decapod crustaceans are recorded from coastal outcrops of Island Sandstone between Perpendicular Point and Punakaiki, Westland, New Zealand. The fauna consists of three raninids—Laeviranina pororariensis (Glaessner), L. keyesi n. sp., Lyreidus bennetti n. sp.; two portunids—Rhachiosoma granuliferum (Glaessner), Pororaria eocenica Glaessner; a goneplacid—Carcinoplax temikoensis n. sp.; and two majids—Leptomithrax griffini n. sp., Notomithrax allani n. sp. Together, they form the most diverse brachyuran assemblage yet described from New Zealand. The decapods are preserved in unusual elliptical masses, with their long axes typically parallel to bedding, containing superbly preserved cuticle often surrounded by well-formed fecal pellets, probably of decapod origin. The accumulations are interpreted to be mechanical concentrations within depressions produced by decapods or associated spatangoid echinoids. Although seven of the species have been recorded only from the Island Sandstone, Rhachiosoma granuliferum (Glaessner) is now known to occur in the correlative deep-water facies of the Kaiata Formation in North Westland, as well as in the Tapui Sandstone, North Otago (middle Eocene), and from coeval rocks at Snowdrift Quarry, southeast Otago. The raninids suggest comparison with congeneric forms from Snowdrift Quarry and the Tapui Sandstone, as well as with the La Meseta Formation, Seymour Island, Antarctica. Based upon associated foraminiferans, a Kaiatan–Runangan (late Eocene) age is assigned to this fauna. The occurrences of Carcinoplax, Leptomithrax, and Notomithrax represent paleobiogeographic and stratigraphic records for the genera.

The recovery of well-preserved silicified larvae from the early Tournaisian of Montagne Noire, southern France, allows the first description of the early ontogeny of proetoid trilobites, survivors of the end-Devonian Hangenberg extinction event. The fauna comprises various taxa that can only partly and tentatively be assigned to the genera Liobolina, Diacoryphe, and Pedinocoryphe without specific attribution. The close resemblance of these larvae to previously described proetoid larvae from the Ordovician and Devonian emphasizes the ontogenetic homogeneity of this superfamily. Moreover, it supports the view that the Proetida is composed of two clades: the Aulacopleuroidea/Bathyuroidea group and the Proetoidea. The Carboniferous anaprotaspides exhibit an unusually wide size-range that may provide evidence of the acquisition of an extended planktonic period in the early ontogeny of at least some Carboniferous proetoids. This change in the ontogenetic strategy may have enabled proetoid trilobites to survive during the end-Devonian biocrises.

Acritarch biostratigraphic and δ13C chemostratigraphic data from the Krol A Formation in the Solan area (Lesser Himalaya, northern India) are integrated to aid inter-basinal correlation of early–middle Ediacaran strata. We identified a prominent negative δ13C excursion (likely equivalent to EN2 in the lower Doushantuo Formation in the Yangtze Gorges area of South China), over a dozen species of acanthomorphs (including two new species—Cavaspina tiwariae Xiao n. sp., Dictyotidium grazhdankinii Xiao n. sp.), and numerous other microfossils from an interval in the Krol A Formation. Most microfossil taxa from the Krol A and the underlying Infra-Krol formations are also present in the Doushantuo Formation. Infra-Krol acanthomorphs support a correlation with the earliest Doushantuo biozone: the Appendisphaera grandis-Weissiella grandistella-Tianzhushania spinosa Assemblage Zone. Krol A microfossils indicate a correlation with the second or (more likely, when δ13C data are considered) the third biozone in the lower Doushantuo Formation (i.e., the Tanarium tuberosum-Schizofusa zangwenlongii or Tanarium conoideum-Cavaspina basiconica Assemblage Zone). The association of acanthomorphs with EN2 in the Krol Formation fills a critical gap in South China where chert nodules, and thus acanthomorphs, are rare in the EN2 interval. Like many other Ediacaran acanthomorphs assemblages, Krol A and Doushantuo acanthomorphs are distributed in low paleolatitudes, and they may represent a distinct paleobiogeographic province in east Gondwana. The Indian data affirm the stratigraphic significance of acanthomorphs and δ13C, clarify key issues of lower Ediacaran bio- and chemostratigraphic correlation, and strengthen the basis for the study of Ediacaran eukaryote evolution and paleobiogeography.

UUID: http://zoobank.org/5289fdb2-0e49-4b3b-880f-f5b21acab371.

Three homocrinid crinoids from the Upper Ordovician Maquoketa Formation of northern Iowa and southern Minnesota are described: Ectenocrinus simplex (Hall), Drymocrinus strimplei new species, and Sygcaulocrinus typus Ulrich. Ectenocrinus simplex is relatively abundant, geographically widespread in the Appalachians and midcontinent of North America, and long-ranging in time (Middle Ordovician Shermanian to Upper Ordovician Maysvillian). The aboral cup of ectenocrinids underwent transpositional allometry during its evolution so that juvenile cups from the Upper Ordovician Maquoketa Formation resemble the adult cups of ancestral individuals from the Middle Ordovician. Sygcaulocrinus typus exhibits a unique expanded proximal stem consisting of three-to-five large columnals throughout its post-larval development. These columnals are rigidly joined to the aboral cup. Consequently, the proximal generative zone for new columnals is displaced below the proximal part of the stem. In addition, the columnals in the proximal stem of S. typus mainly grow with stong positive allometry with respect to the aboral cup. Essentially, the growth vectors of the proximal columnals converge on those of the aboral cup plates.