The genus Otarion Zenker, 1833, first appears in the Wenlock simultaneously with Cyphaspis Burmeister, 1843, as the oldest known species of each occur together in the southern Mackenzie Mountains of the Canadian Northwest Territories. The genera are unambiguous sister groups, a relationship supported most compellingly by a uniquely derived and distinctive pattern of juvenile cephalic spines, shared also with the Carboniferous genus Namuropyge Richter and Richter, 1939. This sister group relationship permits the development of a robust and stratigraphically correlated hypothesis of relationship among the adequately known species of Otarion, Otarion, Cyphaspis, and Namuropyge constitute the tribe Otarionini. The Mississippian genus Dixiphopyge Brezinski, 1988, may also belong to Otarionini. Namuropyge is a paedomorph, likely derived from a Degree Six or Seven meraspid of an older species of uncertain position in the Otarion–Cyphaspis clade.

Three Wenlock species of Otarion occur in stratigraphic succession in a single section in the Mackenzie Mountains. Analysis of morphological change with time, and of sequential ontogenies, suggests that the Silurian history of the genus was dominated by incidents of peramorphosis.

New species are Otarion huddyi, O. beukeboomi, and O. coppinsensis. Otarion brauni Perry and Chatterton, 1979, is revised.

Species of the late Osagean and early Meramecian advanced cladid crinoid genera (suborder Poteriocrinina) Armenocrinus, Bollandocrinus, Corythocrinus, Cosmetocrinus, Culmicrinus, Cydrocrinus, Histocrinus, Hypselocrinus, Lebetocrinus, Ophiurocrinus, Poteriocrinites, Scytalocrinus, Springericrinus, and Ulrichicrinus from Illinois, Indiana, Iowa, and Missouri are redescribed and redefined from study of type material. Nomenclatural and systematic acts include the following: 1) Poteriocrinus tenuidactylus Worthen, 1882, is a senior synonym of Scaphiocrinus obscurus Wachsmuth and Springer, 1886, and is assigned to Armenocrinus; 2) P. verus Miller and Gurley, 1890, is assigned to Culmicrinus; 3) P. mammaeformis Worthen in Miller, 1889, is questionably assigned to Culmicrinus; 4) Cydrocrinus coxanus (Worthen, 1882) is a junior synonym of C. concinnus (Meek and Worthen, 1870); 5) Decadocrinus stellatus Lane and Howell, 1986, is questionably assigned to Histocrinus; 6) P. crawfordsvillensis Miller and Gurley, 1890, is a junior synonym of Hypselocrinus hoveyi (Worthen in Worthen and Meek, 1875); 7) Hypselocrinus boonvillensis (Miller, 1891) and H. neglectus (Miller and Gurley, 1896) are junior synonyms of H. arcanus (Miller and Gurley, 1890); 8) Hypselocrinus vansanti n. sp. is described; 9) Hypselocrinus indianensis (Meek and Worthen, 1865) is a nomem dubium; 10) Poteriocrinus arachnaeformis Worthen, 1882, is a valid species of Poteriocrinites; 11) P. cantonensis Miller and Gurley, 1890, is assigned to Scytalocrinus; 12) Ulrichicrinus coryphaeus (Miller, 1891), P. amoenus Miller, 1891, and P. brittsi Miller, 1891, are junior synonyms of U. agnatus (Miller, 1891); and 13) P. illinoisensis Worthen, 1882, is questionably assigned to Ulrichicrinus.

Bollandocrinus? sp. from the Keokuk Limestone might represent the first report of the genus from North America, being previously known only from the lower Carboniferous of Great Britain. Ophiurocrinus sp. from the Keokuk Limestone is the first report of this genus from the Osagean, being previously known only from the Chesterian of North America and the upper Carboniferous of Europe.

Bathymodiolin mussels are a group of bivalves associated with deep-sea hydrothermal vents and other reducing deep-sea habitats, and they have a particularly rich early Cenozoic fossil record in western Washington State, U.S.A. Here we recognize six species from middle Eocene to latest Oligocene deep-water methane seep deposits in western Washington. Two of them are new: Vulcanidas? goederti from the middle Eocene Humptulips Formation and Bathymodiolus (sensu lato) satsopensis from the late Oligocene part of the Lincoln Creek Formation. Very similar to the latter but more elongate are specimens from the early Oligocene Jansen Creek Member of the Makah Formation and are identified as B. (s.l.) aff. satsopensis. Bathymodiolus (s.l.) inouei Amano and Jenkins, 2011 is reported from the Lincoln Creek Formation. Idas? olympicus Kiel and Goedert, 2007 was previously known from late Eocene to Oligocene whale and wood falls in western Washington and is here reported from Oligocene seep deposits of the Makah and Pysht Formations. Vulcanidas? goederti occurs at a seep deposit from a paleodepth possibly as great as 2000 m, suggesting that its living relative, Vulcanidas insolatus Cosel and Marshall, 2010, which lives at depths of only 150–500 m, is derived from a deep-water ancestor. The bathymodiolins in western Washington indicate that the group originated at least in the middle Eocene and underwent a first diversification in the late Eocene to Oligocene. Early ontogenetic shells of all fossil species investigated so far, including the middle Eocene Vulcanidas? goederti, reflect planktotrophic larval development indicating that this developmental mode is an ancestral trait of bathymodiolins.

Two Permian fusulinid faunas, including nine species belonging to six genera, from the northern Tengchong Block, Southwest China, are studied and compared with the coeval fusulinid faunas from other blocks with Gondwana-affinity and South China. in the Kongshuhe section, the fauna is dominated by Eoparafusulina in the lower part of the Dadongchang Formation and possibly suggests an age of Sakmarian, while in the Shanmutang section, the fauna from the middle of the Dadongchang Formation mainly consists of Chusenella mingguangensis n. sp. and Monodiexodina gigas n. sp., indicating a Wordian to Capitanian age. Study has also demonstrated that fusulinid faunas from the Tengchong Block shared similar features with the contemporary faunas from the Baoshan Block and Sibumasu Block in the low generic and specific diversities and the absence of the taxa commonly found in Cathaysia Tethys areas, such as the Pseudoschwagerinidae, Verbeekinidae, and Neoschwagerinidae. However, visible differences in species composition still exist between the faunas of the Tengchong Block and those of the other two blocks, revealing an apparent regional feature in the faunas of the Tengchong Block.

Cretaceous non-marine deposits are widespread in China and have been studied comprehensively. The Songliao Basin in northeast China is thought to be well suited for investigation of Cretaceous biostratigraphy. However, despite much research having been conducted in the basin, little is known about its Late Cretaceous biostratigraphy and paleoenvironment. Here, we establish a high-resolution biostratigraphy of the Late Cretaceous based on ostracods from borehole SK1(n) in the Songliao Basin, northeast China. As part of the present study, 45 species assigned to 20 genera have been recovered, with one new species (Ilyocypris bisulcata n. sp.) and five ostracod assemblages: the Cypridea gunsulinensis–Mongolocypris magna assemblage, which is marked by the first occurrence (F.O.) of Ilyocyprimorpha with nodes and spines; the Ilyocyprimorpha–Limnocypridea sunliaonensis–Periacanthella assemblage, which ranges from the F.O. of Ilyocyprimorpha with nodes and spines to the F.O. of Strumosia sp.; the Strumosia inandita assemblage from the F.O. of Strumosia sp. to the lower occurrence (L.O.) of Strumosia inandita; the Talicypridea amoena–Metacypris kaitunensis–Ziziphocypris simakovi assemblage from the F.O. of Mongolocypris apiculata (Cea) and Talicypridea amoena to the F.O. of Ilyocypris sp.; and the Ilyocypris assemblage from the F.O. of Ilyocypris sp. to the L.O. of Ilyocypris bisulcata n. sp.

Moreover, the zonal fossil Ilyocypris bisulcata n. sp. of Zone 5 is here described for the first time from the upper Mingshui Formation, and Paleocene charophyte genera including Neochara and Grovesicahra have been found to coexist with the Zone 5 fauna. The age of the Ilyocypris Assemblage is assigned to the latest Maastrichtian to the earliest Danian.

The Araripe Basin is the most extensive interior basin in northeastern Brazil, comprising areas of Ceará, Piauí and Pernambuco states. The Santana Formation, attributed to the Aptian–?lower Albian age of the basin, is subdivided into two members, Crato and Romualdo, which bear an abundant fossil record of plant fragments, arthropods and vertebrates, especially 3D-preserved fishes. The present study focuses on the taxonomy, ontogeny and paleoecology of two ostracode species from the Romualdo Member and the top section of the Crato Member (Ipubi layers), Harbinia salitrensis (Krömmelbein and Weber, 1971) emend. and H. alta new species. The ontogenetic series for both species are illustrated, except for the A-8 instar; H. salitrensis is also redescribed. The present work is also the first to produce quantitative information about the paleoecology of the Santana Formation based on ostracode populations. The results obtained from analyses of the population age-structure of both species, in addition to dominance (Simpson) and diversity index (Shannon) values, corroborated previous data on the studied sequence. According to these results, the strata were deposited in a limnic, low-to-moderate energy environment with salinity levels varying from oligohaline to mesohaline. The new data indicate the possibility of these environments also being hypersaline.

A crinoid and stelleroid fauna is described from the Famennian (Late Devonian) Broken Rib Member of the Dyer Formation of the White River Plateau, Colorado. The fauna postdates the Late Devonian extinction event. Six new crinoid species described, including the new genus Tarassocrinus, are: Strimplecrinus dyerensis, Catactocrinus? torus, Hypselocrinus? bisonensis, Gilmocrinus? albus, Eireocrinus? coloradoensis, and Tarassocrinus synchlydus. The cladid-dominated crinoid fauna is transitional between earlier Devonian and later Carboniferous faunas. It contains the first report of Cupressocrinites (a Famennian Lazarus taxon) and Eireocrinus? in North America and extends ranges of several Carboniferous genera into the Late Devonian. A preliminary revision of the Rhenocrinidae is recommended. The family Glossocrinidae is recognized, and the Cupressocrinitidae are transferred to the Gasterocomacea.

A new stelleroid genus and species, Pleiadeaster inceptus (Asteroidea; family unknown), and an ophiuroid, Ophiopolytretus aethus (Ophiuroidea; Lapworthuridae?) are named. In addition, Hudsonaster (Hudsonasteridae; Asteroidea) and two unassigned asteroids are present, and three further stelleroids cannot be assigned to the class level. Pleiadeaster and Hudsonaster are important because they suggest that the Late Devonian might have been a time of transition for asteroids. Ophiopolytretus aethus is an oegophiurid ophiuroid with distinctive respiratory? pores penetrating the disk plates.

The late Namurian Hindostan Whetstone beds are among the oldest Pennsylvanian strata recognized in the Illinois Basin. Trace-fossil holotypes of Haplotichnus indianensis, Plangtichnus erraticus, and Treptichnus bifurcus were first described and illustrated from these nonmarine strata with line drawings without reference to scale in a relatively obscure work by S. A. Miller (1889). These holotypes are refigured and redescribed in this paper. Based on examination of holotype collections, the Ordovician “Feather-stitch Trail” of Wilson (1948) is judged not to be congeneric with Treptichnus. The ichnogenus Ancorichnus, which is present in the Hindostan Whetstone beds, superficially resembles Haplotichnus; however, Haplotichnus lacks the internal meniscae characteristic of Ancorichnus.

The following new Toernquistiidae from Whiterockian (Llanvirn to lower Caradoc) strata of the Precordillera, western Argentina, are described: Chomatopyge canasi new species, Lasarchopyge benedettoi new genus and species, Lasarchopyge correae new genus and species, Lasarchopyge new species A, and Paratoernquistia sanchezae new genus and species. Phylogenetic analysis suggests that the Toernquistiidae Hupé, 1953 (including Chomatopyge, Lasarchopyge, Mesotaphraspis, Paratoernquistia, and Toernquistia) is closely related to but distinct from the Dimeropygidae Hupé, 1953 (including Ischyrotoma, Ischyrophyma and Dimeropyge). It is difficult to find unique synapomorphies that unite toernquistiids and dimeropygids into a monophyletic group that excludes other proetides (e.g., hystricurids), although details of their ontogenies are similar. Several species of Toernquistiidae are known from the Argentine Precordillera (one species previously described), and other species of this family have been described from Australia, Baltica, China, Kazakhstan and Laurentia. Members of the Dimeropygidae are known only from Baltica and Laurentia.

A new genus and species of edrioasteroid grade echinoderm, Kailidiscus chinensis, is described from the Kaili Biota of the basal lower Middle Cambrian Kaili Formation from Guizhou Province, China. This echinoderm has a strong resemblance to isorophid edrioasteroids, bearing a well-developed peripheral rim, long curved ambulacra, and slightly imbricate interambulacral plating at maturity. However, the presence of pore-bearing, double biserial floor plates, tiered cover plates, lack of radially positioned oral frame plates, and unincorporated hydropore/gonopore are unknown in isorophids. Many of these features bear strong resemblance to eocrinoids and helicoplacoids, attesting to the plesiomorphic nature of this taxon. Despite the obvious anatomical differences, specimens of this species preserve a complete ontogeny that resembles that of isorophids. Juveniles show a discoidal theca with straight ambulacra that transitions to an inflated theca with strongly curved ambulacra with maturity.

The last 15 years of field work along the beaches and bluffs of the Colville River, on Alaska's Arctic Coastal Plain, have produced a diverse record of high-latitude dinosaurs. Seven families and eight genera are documented with several other families and genera possibly being represented by less diagnostic remains and only a few scattered elements (Table 1; Nelms, 1989; Gangloff, 1994, 1998; Fiorillo et al., 1999; Fiorillo and Gangloff, 2000, 2001). Virtually all of the common major groups of theropods and ornithopods typical of the Late Cretaceous of northern North America are present. Most of the skeletal remains are found in rocks assigned to the Prince Creek Formation of the Colville Group (Detterman et al., 1963, 1975; Phillips, 1990). The diversity of the dinosaur record in Alaska has been significantly increased with the discovery of abundant tracks and trackways along the North Slope and Arctic Coastal Plain over the last six years. The majority of the ichnofossil record is contained in various terrestrial coal-bearing rocks assigned to the Early Cretaceous Nanushuk Group (Ahlbrandt et al., 1979). The dinosaur biozone spans the upper part of the Nanushuk group and all of the Colville Group, ranging from the mid to Late Cretaceous (Albian to Maastrichtian; Mull, 1985). The already diverse and abundant record of dinosaur skeletal fossils was increased by the discovery in 1999 of the first evidence of pachycephalosaurs from this region (Fig. 1). This taxon is now represented by a nearly complete left squamosal and the contiguous, posterior, basal part of the dome. The highly thickened bone with characteristic prismatic internal structure accompanied by the distinctive ornamentation diagnostic of this group allows for an unequivocal identification to the subfamily level. The specimen (UAM # AK-493-V-001, Fig. 2.2) is most of the left squamosal and includes a portion of a thickened dome. The specimen is bounded on three sides by parted sutures interpreted as representing the contacts with the quadrate, exoccipital, and the narrow descending portion of the parietal bone (see Fig. 2.2, 2.4). The remaining margin exhibits a broken surface that reflects the polygonal prismatic internal structure of a part of the parietal-frontal dome. The sutures are well preserved and show little or no evidence of fluvial abrasion or weathering due to subaerial exposure prior to burial.

Caridroit, De Wever, and Dumitrica (1999) promoted stauraxon (Radiolaria) to an order, order Latentifistularia, and De Wever et al. (2001) proposed a classification using family and genus levels. However, the taxonomy of this order in genus level is still problematic because some genera were named according to broken specimens. A radiolarian fauna with a high diversity was collected from the late Changxingian in southern Guanxi, China. These specimens are very well preserved so that they are rare material for roundly describing the characters of some genera. They are identified as 42 species belonging to 16 genera and 5 families. Fifteen new species and one new genus are described, some genera are discussed, and some species are revised.

Bivalves have pursued an infaunal lifestyle since early in their history. Trace fossils that have been attributed to the infaunal activity of bivalves include Hillichnus, Lockeia (=Pelecypodichnus), Lophoctenium, Protovirgularia, Ptychoplasma, Siphonichnus and Scalichnus. Re-evaluation of the ichnogenera Siphonichnus and Scalichnus supports consolidation into a single ichnogenus, Siphonichnus, which has taxonomic precedence.

Siphonichnus, as redefined herein, presently includes four ichnospecies. Siphonichnus eccaensis Stanistreet et al. is an unlined vertical tube characterized by concave downward laminae penetrated by a single central shaft and is interpreted to reflect downward burrowing in response to net erosion during the life span of the animal. Siphonichnus phiale (Hanken et al., 2001) is characterized by concave upwards laminae and reflects equilibrichnial behavior by the tracemaker. Siphonichnus lepusaures n. isp. is characterized by concave upwards laminae with a pair of vertically oriented, unlined tubes at the top and is interpreted as the dwelling trace of a bivalve with paired siphons responding to sediment aggradation. Siphonichnus sursumdeorsum n. isp. is characterized by concave upwards laminae in its basal third and convex upwards laminae in its upper third and is interpreted as the dwelling trace of a bivalve exhibiting equilibrichnial behavior in a dynamic depositional setting. Consolidation of these ichnotaxa into a single ichnogenus simplifies the ichnotaxonomy and provides a means of assessing the sedimentological significance of bivalve-generated dwelling/equilibrium/escape structures.

Isolated marginal tooth crowns of the early Campanian mosasaur Hainosaurus Dollo, 1885, from the Kristianstad Basin and the Vomb Trough, southern Sweden, are described and illustrated. The teeth have been collected from a narrow stratigraphic interval corresponding to the highest belemnite zone in the lower part of the European two-fold division of the Campanian stage. A reexamination of dental and skeletal characters in two alleged species of Hainosaurus, ‘H.’ pembinensis Nicholls, 1988 and ‘H.’ gaudryi (Thévenin, 1896), and detailed comparisons with the corresponding elements in H. bernardi Dollo, 1885 and Tylosaurus proriger (Cope, 1869a), strongly indicate that ‘H.’ pembinensis and ‘H.’ gaudryi are both Tylosaurus Marsh, 1872. Diagnostic features of Hainosaurus include a very small infrastapedial process on the quadrate (conspicuous protuberance in Tylosaurus), flattened, symmetrically bicarinate marginal teeth (asymmetric and conical in Tylosaurus), short and wide pygal centra, and anteriorly situated intermediate caudal vertebral centra with dorsoventrally thin transverse processes (markedly triangular centra and thick processes in Tylosaurus).

Six Early Silurian Rhodocrinitacea (Crinoidea, Camerata) are recognized from the Brassfield Formation of Ohio. Previously only a single Early Silurian rhodocrinitacean was known. The new forms include Kyreocrinus constellatus n. gen., n. sp.; Rhachicrinus wrighti n. gen., n. sp.; Silfonocrinus siluricus n. gen., n. sp.; Stereoaster squamosus Foerste; Xysmacrinus greenensis n. gen., n. sp.; and Turbocrinus punctum n. gen., n. sp. Rhachicrinus and Silfonocrinus are assigned to the Opsiocrinidae, which previously included two Devonian genera; Turbocrinus is assigned to the Anthemocrinidae; and Kyreocrinus, Stereoaster and Xysmacrinus are assigned to the Rhodocrinitidae.

The Opsiocrinidae are thought to be derived from the Reteocrinidae; and a possible basis for subdividing the Rhodocrinidae is proposed, based on the arms, plating in regular interrays, presence of median ray ridges and calyx shape.

Calceocrinids are unique crinoids with the crown movably hinged to a recumbent stem. The crown was raised for feeding by closing the hinge and bending the proximal stem. While resting, the crown lay parallel to the stem with the hinge opened. Allometric equations for four species reflect a combination of ontogeny, adult body size, phylogeny, habitat, and functional morphology. The hinge of most adult calceocrinids is extended into ear-like projections which made the crown more stable on the seafloor. For the hinge moment versus the effective weight of the crown, positive allometry characterized taxa that lived in agitated environments, whereas isometry was adequate for quiet-water species. The adult body size provides a secondary effect on the data for crinoids from the same type of environment. Here, the initial intercepts are transposed so that larger animals functioned like smaller ones. The equations are independent of phylogenetic position. All species exhibit positive allometry of the length and number of plates in the arms. The food-gathering capacity of a crinoid is estimated by the number of food-catching tube-feet multiplied by the width of the food grooves, whereas the soft parts that must be fed are proportional to the crown volume. The ratio of food-gathering capacity to crown volume is either fixed or decreases slightly in larger crinoids. Statistical tests reveal that all species follow a single developmental pattern for these two parameters. However, some of the evolutionary changes in the arms permitted calceocrinids to retain an adequate food-gathering capacity into larger adult body sizes.

Several dinosaurs, notably Ouranosaurus and Spinosaurus, have vertebral columns marked by prominent arrays of elongated neural spines. Using pelycosaurian sailbacks like Dimetrodon as analogies, popular orthodoxy holds that the tall spines served as supporting struts for dorsal sails of purported thermoregulatory function, especially heat dissipation in tropical climates. It is argued here that the neural spines of Ouranosaurus, Spinosaurus, and several other long-spined dinosaurs favor bison-like humps rather than sails: 1) in functional morphology and relative elongation they are dissimilar to pelycosaur spines but homoplastically converge on the spines of high-withered ungulates; 2) the usefulness of a sail in thermoregulation has been exaggerated—in large tetrapods it would have been fairly efficient as a thermal amplifier but ineffective as a radiator; hence large sail-bearing dinosaurs in open tropical climates are improbable; 3) the insulation properties of humps favor gigantothermy, the most likely thermobiological model for large dinosaurs.

Dinosaur humps are probable adaptations for: 1) energy storage, maintenance of gigantothermy, and heat-shielding in unshaded habitats; 2) long-distance migration from feeding to nesting grounds across terrains of variable productivity; and 3) lipid conservation for production of large clutches of eggs at the nesting site. Because sacral, caudal, or dorsal humps were relatively common traits among certain groups, the fashionably anorexic image of many large dinosaurs must be emended.

A new, low-density trilobite body cluster from an Upper Ordovician Kope Formation mudstone in the Cincinnati region is characterized by well-preserved, articulated specimens. This cluster is polytaxic, size-segregated, and shows an unusual variety of flexure postures in the most common taxon, Flexicalymene aff. granulosa. Specimens show internal pyritization and associated pyritefilled tubular burrows, and were preserved by rapid deposition of mud from a sediment-laden flow. Size-segregation among species, but size-consistency within species, coupled with sedimentological data and apparently haphazard body orientation data, suggest that the trilobites represent a biological association, rather than the product of mechanical sorting. While the majority of specimens are inverted, many are dorsal-up, and some are inclined to bedding. Postures include prone (i.e., nonflexed), simple dorsal or ventral flexure, and complex stances that combine both dorsal and ventral flexure. Flexure pattern appears largely unrelated to sediment compaction. We interpret the cluster as an association of live trilobites that were entombed in situ. Specimens may have inverted prior to burial as a behavioral posture, or as a response to onset of burial. The animals were likely preserved in the process of escaping, as they tried to free themselves from being buried. This is in contrast to the tightly enrolled stance in some trilobites, especially other Flexicalymene, commonly associated with rapid burial events, and indicates a new behavioral aspect of trilobite paleobiology. The distribution of associated burrows suggests that the rotting carcasses attracted scavengers.

Four distinct fossil turtle assemblages (Chelonia) are recognized from the Panama Canal Basin. The oldest, from the late Eocene–early Oligocene Gatuncillo Formation, is dominated by podocnemidid pleurodires. The early Miocene Culebra Formation includes both podocnemidids and trionychids. The early to middle Miocene Cucaracha Formation includes taxa classified in Geoemydidae (including Rhinoclemmys panamaensis n. sp.), Kinosternidae (represented by Staurotypus moschus n. sp.), large testudinids, trionychids, and podocnemidids, and finally, the late Miocene Gatun Formation records cheloniid sea turtles. These fossils include the oldest known representatives of Rhinoclemmys, the oldest record of kinosternids in Central America with a more extensive southern paleodistribution for Staurotypus and staurotypines in general, early occurrences of giant tortoises in the Neotropics, the oldest occurrence of soft-shell turtles in the tropics, the oldest late Eocene–early Oligocene Neotropical occurrences of podocnemidids. The Panamanian fossil turtles represent clades that are primarily endemic to North America, showing their very early arrival into the Neotropics prior to the complete emergence of the Isthmus of Panama, as well as their first contact with Caribbean-South American pleurodires by the early Miocene.

A fossilized nest found in a 17 Ma paleosol on Rusinga Island is similar in many respects to those constructed by bees. The nest consists of subellipsoidal cells arranged in paired, parallel rows, which are themselves arranged in clusters. Typical cells average approximately 6 mm by 3.5 mm, and have curved dorsal surfaces and nearly flat ventral surfaces. The nest is here referred to a new ichnospecies: Celliforma habari. The cell shape and nest architecture are most like those of modern bees of the subfamily Halictinae (Apoidea: Halictidae), and probably were constructed by bees with a societal structure that was at least communal and quite possibly more highly social. The nest suggests a subhumid to humid climate and angiosperm-dominated vegetation for Rusinga Island during Early Miocene time.