A diverse, well-preserved radiolarian assemblage is reported from the Sandbian age Climacograptus bicornis Graptolite Biozone. This new assemblage, recovered from the Pingliang Formation in the Guanzhuang section, China, includes six new species along with 13 other previously described taxa. Geminusphaera new genus incorporates G. grandis n. sp. and G. kongtongensis n. sp. and is proposed for inaniguttids constructed from two distinct porous spheres bearing seven or more primary spines. Protopylentonema new genus is introduced to incorporate pylomate entactinarians with five-rayed initial spicules. It includes P. ordosensis n. sp. as well as P. aperta, P. rimata, and P. insueta that were formerly assigned to Kalimnasphaera. Micro-computed tomography investigation of skeletal microstructure supports establishment of the new genera together with other new spumellarian species: Haplotaeniatum implexa n. sp., Inanigutta quadrispinosa n. sp., and Kalimnasphaera pingliangensis n. sp. It also indicates that family-level reassignment of Etymalbaillella from the Proventocitidae to the Ceratoikiscidae is appropriate.

Global distribution of Late Ordovician radiolarian occurrences highlights a strong preference for areas with equatorial to tropical sea surface temperatures. This must have led to ecological stress among radiolarian communities in adapting to global cooling in the Hirnantian.

UUID: http://zoobank.org/3d3f55b8-0e70-4f9f-9738-265750d8ec3a.

One of the oldest fossil horseshoe crabs figured in the literature is Entomolithus lunatus Martin, 1809, a Carboniferous species included in his Petrificata Derbiensia. While the species has generally been included within the genus Belinurus Bronn, 1839, it was recently used as the type species of the new genus Parabelinurus Lamsdell, 2020. However, recent investigation as to the appropriate authority for Belinurus (see Lamsdell and Clapham, 2021) revealed that all the names in Petrificata Derbiensia were suppressed in Opinion 231 of the International Commission on Zoological Nomenclature (1954) for being consistently nonbinomial under Article 11.4 of the International Code of Zoological Nomenclature (ICZN) (International Commission on Zoological Nomenclature, 1999). Despite the validation of several species names for anthozoans, brachiopods, and cephalopods described in Petrificata Derbiensia in subsequent rulings (International Commission on Zoological Nomenclature, 1956a, b), Belinurus lunatus has not been the subject of any subsequent Commission ruling or opinion, and so its use in Petrificata Derbiensia remains suppressed. The Belinurus lunatus species name was used in several subsequent publications during the 1800s, none of which made the name available under ICZN article 11.5; Parkinson (1811) is also suppressed for being nonbinomial, while Woodward (1830), Buckland (1837), Bronn (1839), and Baily (1859) refer to the species only as a synonym of Belinurus trilobitoides (Buckland, 1837) through citation to the suppressed Pretificata Derbiensia. The first author to make Belinurus lunatus an available name was Baldwin (1905), who used the name in reference to a new figured specimen from Sparth Bottoms, Rochdale, UK, but again as an explicit junior synonym of Belinurus trilobitoides (Buckland, 1837). Therefore, it was not until Eller (1938) treated B. lunatus as a distinct species from B. trilobitoides that B. lunatus became an available name as per ICZN Article 11.6.1 under the authorship of Baldwin (1905) following ICZN Article 50.7.

Polykampton recurvum n. isp. is the sixth ichnospecies of the ichnogenus Polykampton Ooster, 1869. It is a horizontal structure composed of a median cylindrical tunnel and narrow, usually back-curved lateral lobes located in alternating position. It occurs 2–3 cm below the top of single beds in the Maastrichtian–Paleocene deep-sea turbiditic marlstones of the Monte Antola Unit in the Northern Apennines. The lobes of P. recurvum n. isp. are actively filled with gray mudstone from above through the permanently open median tunnel. The trace fossil belongs to the category sequestrichnia, which is typical of oxygenated deep-sea environments characterized by seasonal or episodic supply of organic matter into a generally oligotrophic environment. P. recurvum n. isp. was produced by a “worm,” probably a polychaete, which adapted to seasonal or only episodic supply of organic matter to the deep-sea floor. The tracemaker stored the organic-rich mud in the lobes for nutrition during times of low organic matter availability on the seafloor.

UUID: http://zoobank.org/49555117-1c39-4658-8b49-3f3e2f47ba27

A revision of the rhinocerotid material from the Negev (Israel), dating back to the early Miocene (MN3 in the European Mammal Biochronology), highlights the presence of Brachypotherium and a taxon close to Gaindatherium in the Levantine corridor. A juvenile mandible, investigated using CT scanning, displays morphologically distinct characters consistent with Brachypotherium cf. B. snowi rather than with other Eurasian representatives of this genus. Some postcranial remains from the Negev, such as a humerus, display features that distinguish it among Miocene taxa. We attribute these postcrania to cf. Gaindatherium sp., a taxon never recorded outside the Siwaliks until now. This taxon dispersed into the Levantine region during the late early Miocene, following a pattern similar to other South Asian taxa. Brachypotherium cf. B. snowi probably occurred in the Levantine region and then in North Africa during the early Miocene because its remains are known from slightly younger localities such as Moghara (Egypt) and Jebel Zelten (Libya). The occurrence cf. Gaindatherium sp. represents a previously unrecorded range expansion out of Southeast Asia. These new records demonstrate the paleogeographic importance of the Levantine region showcasing the complex role of the Levantine corridor in intercontinental dispersals between Asia and Europe as well as Eurasia and Africa.

In the first half of the nineteenth century, a marked shift occurred in our understanding and treatment of the chelicerate fossil record, with the differentiation and recognition of entirely extinct genera for the first time. At the heart of this taxonomic revolution were the Eurypterida (sea scorpions) and Xiphosura (horseshoe crabs), although both groups were in fact considered crustaceans until Lankester's (1881) seminal comparative anatomical study of the extant xiphosuran Limulus Müller, 1785 and modern scorpions. The oldest available eurypterid genus is Eurypterus deKay, 1825; the oldest available fossil arachnid genus name is that of the scorpion Cyclophthalmus Corda, 1835. However, there has been considerable historical confusion over the oldest available fossil xiphosuran genus name, which has been recognized alternately as Belinurus König (with a publication date of either 1820 or 1851) or the synonymous Bellinurus Pictet, 1846. Most recent treatments (e.g., Selden and Siveter, 1987; Anderson and Selden, 1997; Anderson et al., 1997; Lamsdell, 2016, 2021; Bicknell and Pates, 2020) have favored Bellinurus Pictet, 1846 as the available name; however, Haug and Haug (2020) recently argued that Belinurus König, 1820 is valid and has priority, a position then followed by Lamsdell (2020), prompting a reinvestigation of the taxonomic history of the genus. Upon review, it is clear that neither of the previously recognized authorities for Belinurus are accurate and that the two candidate type species for each genus are, in fact, synonyms. Given the convoluted and at times almost illogical history of the competing names, along with the most recent controversy as to which has priority, we present a complete history of the treatment of the genus to resolve the issue.

Olenellid trilobites from the lower Cambrian of the Iberian Peninsula are very scarce and poorly studied, making them difficult to compare with defined species and to include in biostratigraphic and paleobiogeographic analyses. Based on newly collected specimens, we revise the species ‘Callavia? lotzei’ Richter and Richter, 1941 from the ‘Cumbres beds’ of Cumbres de San Bartolomé and the ‘Herrerías shale’ of Cañaveral de León, Sierra del Bujo, and Hinojales (Huelva, Spain), and ‘Paradoxides choffati’ Delgado, 1904 from the Vila Boim Formation of Elvas (Portugal). The new material indicates that Callavia? lotzei is a junior synonym of ‘P. choffati.’ The Iberian species are here assigned to Callavia Matthew, 1897, for which morphological characters are reassessed, offering a valuable opportunity to discuss characters previously misinterpreted for this genus. Traditionally assigned to the Olenelloidea Walcott, 1890, Callavia lacks some of the diagnostic characters of this superfamily and is here assigned to Judomioidea Repina, 1979. A new diagnosis for this genus is provided, and Sdzuyomia Lieberman, 2001 is considered to represent a junior synonym of Callavia. The genus Callavia is distributed across the western margin of Gondwana, from the western Mediterranean region (Iberia and Morocco) throughout all the Avalonia sectors (UK, eastern Newfoundland, and Massachusetts). Its presence in Iberia supports the faunal links between the West Gondwana domain and Avalonia during Cambrian Series 2. The Iberian records of Callavia choffati are assigned to the middle part of the regional Marianian Stage (uppermost Cambrian Stage 3 to the lowermost Cambrian Stage 4) and correlates with the Callavia Biozone of Avalonia (lower Branchian Series).

Protandrous sex change (sex change from male to female) is one of the diverse sexual expressions exhibited by bivalves, but its expression in the shell is quite rare. Previous studies on living and fossil astartids suggest a relationship between protandrous sex change and the formation of crenulations on the ventral shell margin at later ontogenetic stages. Here we report the formation of such crenulations in the Early Jurassic astartid Nicaniella rakoveci (Kuhn, 1935) from the Amaltheenton Formation at Buttenheim, Franconia. This is the earliest known record of protandrous hermaphroditism in fossil bivalves, predating previous reports by at least 13 Myr. A principal component analysis of linear size measurements and Fourier shape analysis of the shell outlines revealed that the outline of Nicaniella rakoveci specimens varies from subquadrate to subcircular, but this variation is independent of the presence or absence of crenulations and therefore not associated with sex. Crenulated specimens exhibit a lower height/inflation ratio than non-crenulated ones, suggesting that the protandrous females have more inflated valves than the males. The formation of crenulations was probably related to allocation of resources for reproduction. The most likely function of the crenulations was to increase the internal shell volume in the female stage to accommodate more eggs rather than being an adaptation against predation as often assumed for other bivalves. The formation of crenulations is part of the protandrous life history and probably is controlled by a genetic mechanism that is also responsible for sex change.

Dragastanella transylvanica n. gen. n. sp. is described. Its calcified skeleton contains numerous voids, partly related to the molds of soft parts of the alga, but also related to lack of calcification. Interpretation of these voids, especially their attribution to original structures (e.g., primary lateral versus reproductive organ), has important implications for the taxonomic position of the alga, even at the family level. Examination of key sections that include the boundary between sterile and fertile parts of the alga excludes the occurrence of external reproductive organs. Unusual, paired pores in the outer part of the mineralized skeleton reflect an asymmetry within the whorl, excluding the presence of secondary laterals. The alga is characterized by a cylindrical to club-shaped thallus bearing only phloiophorous primary laterals arranged in whorls and flaring outwards, forming a cortex. Mineralized lenticular reproductive organs containing cysts set in the equatorial plane (Russoella-type gametophores) occur inside primary laterals (cladosporous arrangement of the reproductive organs). These characters support establishment of the new genus Dragastanella. Dragastanella transylvanica n. gen. n. sp. resembles species previously referred to Zittelina (Zittelina hispanica and Zittelina massei) and Triploporella (Triploporella matesina and Triploporella carpatica). Except for Triploporella carpatica, whose mineralized skeleton does not permit confident attribution to either Triploporella or Dragastanella n. gen., the other species must be ascribed to Dragastanella n. gen. Therefore, the following new combinations are proposed: Dragastanella hispanica n. comb., Dragastanella massei n. comb., and Dragastanella matesina n. comb. Despite widely overlapping biometrical measurements, these species can be differentiated by the size and location of their reproductive organs, the pattern of calcification around the primary laterals, and relationships among structural parameters such as the size of laterals, number of laterals per whorl, and distance between whorls.

The Early Ordovician (late Tremadocian; Stairsian) trilobite Gonioteloides Kobayashi has long been known from a small number of pygidia assigned to a single formally named species, and its affinities have not been assessed. Silicified material from western Utah and southeastern Idaho includes six distinct species assigned to the genus, one of which is the type species. Two others (G. moffitti and G. pankowskii) are new and formally named. An additional three species that are clearly new but known from sparse material are described in open nomenclature. Gonioteloides has a stratigraphic distribution through five consecutive trilobite zones in the mid-Stairsian Stage (upper Tremadocian). Although exoskeletal morphology of three species is almost completely known, the phylogenetic affinity of the taxon remains difficult to determine. It is tentatively assigned to Dimeropygidae Hupé.

UUID: http://zoobank.org/23257d6c-262b-4ef5-ae4e-cc431777e67e

The new fossil micromammal assemblage of Çapak represents a mixture of both Anatolian and European faunal elements. The locality is very important for understanding faunal evolution in the less well-known time interval at the end of the early Miocene of western Anatolia. In Çapak, nine species of rodents and one species of ochotonid were encountered: the hamsters Democricetodon gracilis, Megacricetodon primitivus, Eumyarion aff. E. montanus, Cricetodon cf. C. aliveriensis, Cricetodon sp., and Karydomys cf. K. strati, the mole-rat Debruijnia sp., the squirrel Aliveria luteyni, the dormouse Myomimus tanjuae n. sp., and the pika Albertona balkanica. The assemblage is referable to Anatolian local zone E or MN unit 4. The relative abundance of the various genera is markedly different from that of the older early Miocene assemblages, suggesting that the environment in Anatolia became drier and had a more open landscape.

UUID: http://zoobank.org/75f3276c-dcd8-4090-b2f6-d8fc8d3c3f7c

An assemblage of 50 species of small shelly fossils is described from Cambrian Series 2 (Stage 4) strata in North Greenland, the present day northernmost part of the paleocontinent of Laurentia. The fossils are derived from the basal member of the Aftenstjernesø Formation at Navarana Fjord, northern Lauge Koch Land, a condensed unit that accumulated in a sediment-starved outer ramp setting in the transarctic Franklinian Basin, on the Innuitian margin of Laurentia. Most other small shelly fossil assemblages of similar age and composition from North America are described from the Iapetan margin of Laurentia, from North-East Greenland south to Pennsylvania. Trilobites are uncommon, but include Serrodiscus. The Australian bradoriid Spinospitella is represented by a complete shield. Obolella crassa is the only common brachiopod. Hyoliths, including Cassitella, Conotheca, Neogloborilus, and Triplicatella, are abundant and diverse, but most are represented just by opercula. Sclerites interpreted as stem-group aculiferans (sachitids) are conspicuous, including Qaleruaqia, the oldest described paleoloricate, Ocruranus?, Inughuitoconus n. gen., and Hippopharangites. Helcionelloid mollusks are diverse, but not common; they are associated with numerous specimens of the bivalve Pojetaia runnegari. The fauna compares best with that of the upper Bastion Formation of North-East Greenland, the Forteau Formation of western Newfoundland, and the Browns Pond Formation of New York, but several taxa have a world-wide distribution. Many specimens are encrusted with crystals of authigenic albite. New species: Anabarella? navaranae, Stenotheca? higginsi, Figurina? polaris, Hippopharangites groenlandicus, Inughuitoconus borealis, and Ocruranus? kangerluk.

UUID: http://zoobank.org/160a17b1-3166-4fcf-9849-a3cabd1e04a3

In this study, middle to late Mississippian microfossil assemblages from the Maritimes Basin of eastern Canada (Nova Scotia, SW Newfoundland, and New Brunswick) are closely compared to those from Western Paleotethys basins. The comparison is focused mainly on foraminifers and calcareous algae. Most foraminifers and algae described from the Maritimes Basin are considered cosmopolitan, and the occurrence in western Europe and northern Africa of taxa previously considered endemic to the North America Realm suggests a close paleobiogeographic relationship. This European/African correlation is further supported by other foraminiferal/algal taxa, the importance of which were previously overlooked, including: Plectogyranopsis ex gr. P. hirosei (Okimura, 1965), Mikhailovella Ganelina, 1956, Koktjubina windsorensis (Mamet, 1970), Polysphaerinella bulla Mamet, 1973, Mstinia Dain in Dain and Grozdilova, 1953, Haplophragmina Reitlinger, 1950, Omphalotis Shlykova, 1969, Pseudolituotuba Vdovenko, 1971, Pseudoendothyra Mikhailov, 1939, Saccamminopsis (Sollas, 1921) Vachard and Cózar, 2003, Kamaenella Mamet and Roux, 1974, and Anthracoporellopsis Maslov, 1956. Some species recorded in the Maritimes Basin have been typically recorded in Britain and Ireland in the southern platform of Laurussia. This implies a connection via the Rhenohercynian Ocean, whereas statistical analyses suggest that Maritimes Basin assemblages are closer to those of the Gondwana platform, which could have been established via the Paleotethys Ocean, and also with terranes northwest of the Variscan Front, in which its most logical connection should be with a still-open Rheic Ocean during the Visean and early Serpukhovian. Those taxa demonstrate a more-or-less continuous faunal and microfloral interchange between the Maritimes Basin and the Western Paleotethys paleobiogeographic realm. Furthermore, the width of the Paleotethys and Rheic oceans separating these regions is not considered excessive, particularly during the late Visean and early Serpukhovian.

The middle Eocene Washakie Formation of Wyoming, USA, provides a rare window, within a single depositional basin, into the faunal transition that followed the early Eocene warming events. Based on extensive examination, we report a minimum of 27 species of carnivorous mammals from this formation, more than doubling the previous taxic count. Included in this revised list are a new species of carnivoraform, Neovulpavus mccarrolli n. sp., and up to ten other possibly new taxa. Our cladistic analysis of early Carnivoraformes incorporating new data clarified the array of middle Eocene taxa that are closely related to crown-group Carnivora. These anatomically relatively derived carnivoraforms collectively had an intercontinental distribution in North America and east Asia, exhibiting notable variations in body size and dental adaptation. This time period also saw parallel trends of increase in body size and dental sectoriality in distantly related lineages of carnivores spanning a wide range of body sizes. A new, model-based Bayesian analysis of diversity dynamics accounting for imperfect detection revealed a high probability of substantial loss of carnivore species between the late Bridgerian and early Uintan North American Land Mammal ‘Ages’, coinciding with the disappearance of formerly common mammals such as hyopsodontids and adapiform primates. Concomitant with this decline in carnivore diversity, the Washakie vertebrate fauna underwent significant disintegration, as measured by patterns of coordinated detection of taxa at the locality level. These observations are consistent with a major biomic transition in the region in response to climatically induced opening-up of forested habitats.

UUID: http://zoobank.org/9162f1a6-a12c-4d55-ba1d-dc66e8cda261

New, distinctive, well-preserved and previously undescribed constituents of a Middle Ordovician (middle Darriwilian, Dw2) radiolarian assemblage from the Table Cove Formation in Newfoundland are described. Three-dimensional X-ray micro-computed tomography (μ-CT) facilitates detailed examination of key specimens revealing hitherto unknown details of the internal morphologies of key lower Paleozoic taxonomic groups, among which a lack of knowledge has previously impeded resolution of higher taxonomic rankings.

Twenty-seven archaeospiculid and entactinarian taxa are described and illustrated including six new species: Westernbrookia polygonata n. sp., Neopalaeospiculum piccadilliensis n. sp., Ramuspiculum laxum n. sp. Spongentactinia nazarovi n. sp., Aspiculum irregulare n. sp., and Nyfrieslandia ramosissima n. sp. The investigation extends the known ranges of the species: Pararcheoentactinia reedae Won and Iams, 2002; Sphaeroentactinia robusta Won and Iams, 2015; Varispiculum ectospiculatum Won and Iams, 2015; and Svalbardospiculum multifurcatum (Won, Iams, and Reed, 2005), together with the genus Echidnina to the mid-Darriwilian.

UUID: http://zoobank.org/74826b7b-bb86-45d5-ad23-e6e65e0706df.

This is the first of two comprehensive taxonomic works on the early Miocene (ca. 23–20 Ma) bryozoan fauna associated with coral reefs from the Siamaná Formation, in the remote region of Cocinetas Basin in the La Guajira Peninsula, northern Colombia, southern Caribbean. Fifteen bryozoan species in 11 families are described, comprising two cyclostomes and 13 cheilostomes. Two cheilostome genera and seven species are new: Antropora guajirensis n. sp., Calpensia caribensis n. sp., Atoichos magnus n. gen. n. sp., Gymnophorella hadra n. gen. n. sp., Cribrilaria multicostata n. sp., Cribrilaria nixor n. sp., and Figularia bragai n. sp. Eight species are identified only at genus level and remain in open nomenclature. Of the species found, 27% have erect colonies and 73% encrusting colonies. Both types contributed to the reef framework and produced sediment. The observed bryozoan diversity was higher in the barrier reefs than in the lagoonal patch reefs.

UUID: http://zoobank.org/5c8468ef-31b0-4e7e-ba93-60a2e2f30b76.

Diverse and abundant fossil taxa have been described in the lower Cambrian Shipai Formation in the Three Gorges area of Hubei Province, South China, but the taxonomy and diversity of the co-occurring brachiopod fauna are still far from clear. Here we describe the brachiopod fauna recovered from the Shipai Formation in the Three Gorges area of South China, including representatives of the subphylum Linguliformea: linguloids (Lingulellotreta ergalievi, Eoobolus malongensis, and Neobolidae gen. indet. sp. indet.), and an acrotretoid (Linnarssonia sapushanensis); and representatives from the subphylum Rhynchonelliformea: the calcareous-shelled Kutorginates (Kutorgina sinensis, Kutorgina sp., and Nisusia liantuoensis). This brachiopod assemblage and the first occurrence of Linnarssonia sapushanensis shell beds permit correlation of the Shipai Formation in the Three Gorges area of Hubei Province with the Stage 4 Wulongqing Formation in the Wuding area of eastern Yunnan. This correlation is further strengthened by the first appearance datum (FAD) of the rhynchonelliform brachiopod Nisusia in the upper silty mudstone of both the Shipai and Wulongqing formations. The new well-preserved material, derived from siliciclastic rocks, also gives critical new insights into the fine shell structure of L. sapushanensis. Microstructural studies on micromorphic acrotretoids (like Linnarssonia) have previously been restricted to fossils that were acid-etched from limestones. This is the first study to carry out detailed comparative ultrastructural studies on acrotretoid shells preserved in siliciclastic rocks. This work reveals a hollow tube and solid column microstructure in the acrotretoid shells from the Shipai Formation, which is likely to be equivalent of traditional column and central canal observed in shells dissolved from limestones.

In this study, a new assemblage of Ediacaran metazoan fossils is reported from the basal Stáhpogieddi Formation on the Digermulen Peninsula of Arctic Norway, including Anulitubus n. gen. Moczydłowska in Moczydłowska et al., Anulitubus formosus n. gen. n. sp. Moczydłowska in Moczydłowska et al., Coniculus n. gen. Moczydłowska in Moczydłowska et al., Coniculus elegantis n. gen. n. sp. Moczydłowska in Moczydłowska et al., Fistula n. gen. Moczydłowska in Moczydłowska et al., and Fistula crenulata n. gen. n. sp. Moczydłowska in Moczydłowska et al. The specimens are three-dimensionally preserved and include tubular and conical skeletons that are morphologically distinguished by their body-wall constructions, radial symmetry, polarity, segmentation, and annulation. The skeletons are interpreted to be biomineralized by primary silica based on computed micro-tomographic, petrographic, geochemical, and spectroscopic evidence of originally rigid body wall with layers of constant thicknesses, composed of opal, microcrystalline quartz, and an admixture of carbonaceous material, which differ from the host sediment mineralogy and do not show replacement or encrustation. The fossil-bearing interval immediately overlies strata of Gaskiers age and can be bracketed within 580–541 Ma, but it is estimated to be ca. 575 Ma on the basis of averaged sedimentation rates and biostratigraphic correlations with Ediacaran biota found in up-section deposits of ca. 558–555 Ma. Future new findings of such fossils in different preservation modes and further multi-collector inductively coupled plasma mass spectrometry, which shows the silicon fractionation and traces its biogenic origin versus inorganic mineralization, may corroborate the interpretation of biogenic silicification of these earliest skeletal fossils.

UUID: https://zoobank.org/6bccada1-870e-47b0-b819-82685152ea54

The filter-feeding organ of some extinct brachiopods is supported by a skeletal apparatus called the brachidium. Although relatively well studied in Atrypida and Athyridida, the brachidial morphology is usually neglected in Spiriferida. To investigate the variations of brachidial morphology in Spiriferida, 65 species belonging to eight superfamilies were analyzed. Based on the presence/absence of the jugal processes and normal/modified primary lamellae of the spiralia, four types of brachidium are recognized. Type-I (with jugal processes) and Type-II (without jugal processes), both having normal primary lamellae, could give rise to each other by losing/re-evolving the jugal processes. Type-III, without jugal processes, originated from Type-II through evolution of the modified lateral-convex primary lamellae, and it subsequently gave rise to Type-IV by evolving the modified medial-convex primary lamellae. The evolution of brachidia within individual evolutionary lineages must be clarified because two or more types can be present within a single family. Type-III and Type-IV are closely associated with the prolongation of the crura, representing innovative modifications of the feeding apparatus in response to possible shift in the position of the mouth towards the anterior, allowing for more efficient feeding on particles entering the mantle cavity from the anterior gape. Meanwhile, the modified primary lamellae adjusted/regulated the feeding currents. The absence of spires in some taxa with Type-IV brachidium might suggest that they developed a similar lophophore to that in some extant brachiopods, which can extend out of the shell.

Members of the echinoid order Spatangoida, a highly diverse and abundant marine invertebrate clade, were important denizens of the Cretaceous Western Interior Seaway (WIS), an epicontinental seaway that divided North America in two during an interval of greenhouse conditions between roughly 100 and 65 million years ago. A phylogenetic analysis of spatangoids was conducted using a character matrix of 32 characters from 21 species. Species that occur in the WIS were considered comprehensively, and species from other regions such as South America, Europe, and North Africa were also incorporated into the analysis. Phylogenetic patterns retrieved are largely congruent with preexisting family-level classifications; however, species within several genera, especially Hemiaster and Heteraster, need to be reassigned so that classification better reflects phylogeny. The genera Washitaster and Heteraster are closely related, as are Mecaster, Palhemiaster, and Proraster; Pliotoxaster, Macraster, and Hemiaster; and Micraster and Diplodetus. Biogeographic patterns were also considered using the phylogeny, and several episodes of vicariance and range expansion were identified. These were possibly related to some of the various major episodes of sea-level rise and fall during the Cretaceous. In particular, Valangian–mid-Aptian regressions may have caused vicariance within Heteraster and Washitaster while other early spatangoid vicariance may be related to regressions during the late Aptian–early Cenomanian. Further, vicariance caused by regressions during the mid-Cenomanian–Maastrichtian may have driven diversification within Micraster and Diplodetus. Last, transgressions during the late Aptian–early Cenomanian seem to have spurred prominent range expansions in Mecaster and Hemiaster.