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We report charadriiform and charadriiform-like birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). A partial skeleton of a small modern-type charadriiform is described as a new species, Charadriisimilis essexensis n. gen. n. sp., and most closely resembles taxa of the Charadrii (plovers, stilts, oystercatchers, and other “wader-like” shorebirds). Affinities to this clade were also supported by phylogenetic analyses, which placed the fossil as the sister taxon of either the Burhinidae or all crown group Charadrii. In addition, we identify specimens of the charadriiform-like taxon Scandiavis, which was before known only from the early Eocene Fur Formation in Denmark. Associated limb elements of two individuals are classified as Scandiavis cf. mikkelseni Bertelli et al., 2013, and remains of two further individuals are tentatively assigned to Scandiavis. The presence of a processus supracondylaris dorsalis on the previously unknown humerus corroborates charadriiform affinities of Scandiavis, whereas a plesiomorphic hypotarsus morphology indicates a position outside crown group Charadriiformes. Charadriisimilis essexensis is one of the earliest modern-type charadriiforms, and the holotype of the species is the most substantial early Paleogene fossil record of a charadriiform bird. Together with Scandiavis, as the best-represented taxon to be considered as a stem group charadriiform, it provides the basis for an improved understanding of the evolutionary history of charadriiform birds.
Acteonellids were one of the most significant groups of marine macro-invertebrates in the Late Cretaceous biota of the Tethyan Realm. They were common faunal elements associated with Cretaceous carbonate platform communities most notable for their abundance of rudist frameworks and thrived in coeval lagoons. The Upper Cretaceous fossil-bearing Karababa Formation, cropping out in southeastern Turkey, yields a remarkable assemblage of acteonellid gastropods and rudists. Cretaceous gastropods from sedimentary successions in Turkey barely have been studied over the past 80 years. The subgenus Trochactaeon, a very successful and widespread taxon of heterobranch gastropods within the family Acteonellidae, dominated acteonellid assemblages throughout the Late Cretaceous. In the present work, we present the first record of Trochactaeon (Trochactaeon) giganteus subglobosus from Turkey. It is from a single lower Campanian bed in the upper part of the Karababa Formation of the Gölbaşı region (south of Adıyaman), corresponding to the northwestern part of the Arabian Platform. This record complements information on the temporal and spatial distribution of Trochactaeon at the southern margin of the Tethyan Ocean during the last part of the Cretaceous Period. This discovery increases the documented diversity of the paleofauna from the Upper Cretaceous succession in southeastern Turkey and provides new insights into the paleoenvironment of the carbonate ramp of the northern Arabian plate, and the paleobiogeography of Campanian gastropods in general.
Decimeter-scale, elongate, fossil fronds from the Ediacara Range in South Australia were formally described as Rangea longa Glaessner and Wade, 1966, but the disparate nature of documented specimens has hindered their inclusion in global syntheses and has resulted in these fossils being assigned to at least five different genera in two different clades since their discovery. Detailed study of the type material from the Ediacara Range and the few specimens subsequently collected elsewhere in the Flinders Ranges reaffirms that these specimens represent a single species, with the apparent morphological variation between specimens entirely taphonomic and reflecting the obverse and reverse surfaces of these fronds coupled with the orientation of the frond axis and petaloids at different angles relative to the sea bottom on which they were preserved. The preserved architecture of these fronds constitutes three orders of branching microstructure that are strictly orthogonal to immediately higher and lower orders. This implies affinities with the arboreomorphs, but representing a new frond genus herein named Akrophyllas. Akrophyllas n. gen. differs from all other Ediacaran fronds in exhibiting a stalk that is visible only on one side of the frond and is internal to the other side where the first-order branches instead meet at a zigzag axial trace. Akrophyllas n. gen. was attached to a bulbous holdfast on the sea bottom, and evidence for current scours that formed in the lee of the fronds and for a strong current alignment of felled fronds with depositional overlap of adjacent fronds imply an upright, epibenthic lifestyle for Akrophyllas longa new combination.
An unusual worm, previously interpreted as the earliest leech, is described from the early Silurian (Llandovery, Telychian) Brandon Bridge Formation Lagerstätte (Waukesha Biota) of Wisconsin (~437 Ma). Lacking preserved internal organs, it is up to ~16 cm long, 8.2 mm wide, with ~250 annulations and a circular structure at one end, interpreted here as the broken end of a molt. It is therefore referred to Cycloneuralia incertae sedis.
The typical Mississippian shallow-water deposits of the Jiusi and Shangsi formations are well exposed in the Yashui section in southern Guizhou, South China. The strata are composed mainly of platform limestones intercalated with shales and sandstones. Conodonts obtained from the limestones are dominated by two assemblages of cavusgnathids: the Cavusgnathus aff. Cav. unicornis and Clydagnathus windsorensis assemblage from the upper Jiusi Formation and the Cavusgnathus unicornis assemblage from the lowest Shangsi Formation. Vogelgnathus campbelli (Rexroad, 1957) is reported for the first time in Eastern Paleotethys and is characterized by small lateral denticles. The evolutionary first occurrence of Cavusgnathus unicornis Youngquist and Miller, 1949 is recognized as a marker for the regional Shangsian stage. This biostratigraphic datum is interpreted to be correlative with other shallow-water conodont zones marked by Cavusgnathus unicornis s.l. and similar species from North America and Europe.
All genera based on fossil type species belonging to the family Mactridae are alphabetically listed in this work. The oldest records of the Mactridae come from Cretaceous deposits of North America. However, this group of bivalves has been worldwide recorded from the Paleogene and Neogene. An emended diagnosis for each genus is herein provided. In addition to that, type species, type localities, and occurrences are included. For each genus, a remarks section includes the most recent published taxonomic opinions. Nevertheless, in some cases, new taxonomic decisions based on morphological analysis of types have been taken. Genera based on extant type species are excluded from this work. Forty-five genera are listed herein and type material has been reproduced wherever possible. Ionesimactra nom. nov. is proposed as a replacement name for Caspimactra Ionesi (non Caspimactra Ali-Zade and Kabakova). This work constitutes the basis for future revisions related to fossil taxa of the family Mactridae from different regions.
Crinoids were major constituents of late Carboniferous (Pennsylvanian) marine ecosystems, but their rapid disarticulation rates after death result in few well-preserved specimens, limiting the study of their growth. This is amplified for cladids, who had among the highest disarticulation rates of all Paleozoic crinoids due to the relatively loose suturing of the calyx plates. However, Erisocrinus typus Meek and Worthen, 1865 has been found in unusually large numbers, most preserved as cups but some as nearly complete crowns, in the Barnsdall Formation in Oklahoma. The Barnsdall Formation, a Koncentrat Lagerstätte, is composed predominantly of fine- to medium-grained sandstone, overlain by mudstone and shale; severe compaction of the fossils in the mudstone and shale layer in this formation allowed for exceptional preservation of the plates. Herein, we summarize a growth study based on 10 crowns of E. typus, showcasing a well-defined growth series of this species from the Barnsdall Formation, including fossils from juvenile stages of development, which are rarely preserved. We used high-resolution photographs imported into ImageJ and recorded measurements of the cup and arms for all nondistorted or disarticulated plates. Results show that the plates of the cup grew anisometrically with both positive and negative allometry. The primibrachial plates of E. typus grew with positive allometry. The brachial plates started as uniserial (i.e., cuneiform) as juveniles but shifted to be biserial. Erisocrinus typus broadly shares similar growth trajectories with other cladids. These growth patterns provide insight into feeding strategies and can aid in understanding crinoid evolutionary paleoecological trends.
The Cambrian (Jiangshanian, Sunwaptan) Honey Creek Formation in the Wichita Mountains region of Oklahoma yielded a new fauna dominated by Monocheilus Resser, 1937 (senior synonym of Stigmacephalus Resser, 1937) in association with Ptychaspis Hall, 1863. It occupies the same stratigraphic position as similar faunas in the Upper Mississippi Valley and Alberta, lying a little above an interval characterized by species of Taenicephalus Ulrich and Resser in Walcott, 1924 and Orygmaspis Resser, 1937. Revision of Ptychaspis bullasa Lochman and Hu, 1959 from type material from Idaho and sclerites attributed to the species from Texas reveals a plexus of pseudocryptic species that share tuberculate sculpture on the cranidium. New species are Monocheilus reginae, Monocheilus richardi, Ptychaspis occulta, and Ptychaspis matuszaki.
Toyotamaphimeia is an extinct crocodylian lineage whose name is derived from a mythological Japanese princess. Here, we re-examine the type specimens of a long-forgotten species: Tomistoma taiwanicus from the Pleistocene of Tainan (Taiwan) and revise its taxonomic status to Toyotamaphimeia taiwanicus n. comb., leading to the first recognized species of Toyotamaphimeia outside Japan. Our phylogenetic analyses also support this taxonomic assignment and, more interestingly, further suggest an East Asian lineage. In addition, Toyotamaphimeia taiwanicus n. comb. represents a tropical species, resolving a long-standing puzzle of why Toyotamaphimeia only inhabited a much higher latitudinal area (Japan). Given the large body size of Toyotamaphimeia taiwanicus n. comb. (~7 m) and the fact that it is geologically older than Toyotamaphimeia machikanensis from Japan, we propose a novel evolutionary scenario: the genus Toyotamaphimeia originated in Taiwan and evolved to a large body size with gigantothermic physiology, which resulted in migration out of Taiwan and dispersal farther north to Japan. Our taxonomic identification shows the presence of an extinct endemic crocodylian species from the Pleistocene of Taiwan with large-scale paleogeographic implications. This study, with our recent progress in vertebrate paleontology in Taiwan, should provoke more in-depth paleontological research on the Pleistocene extinction.
The phylum Bryozoa had long been the only major phylum unknown from the Cambrian and by inference the Cambrian Explosion of biodiversity. When described in 2010 as a late Cambrian cryptostome bryozoan, Pywackia baileyi Landing in Landing et al., 2010 became the oldest known bryozoan (early Cambrian bryozoans have since been described). Controversy remains about the phylum-level identification of Pywackia Landing in Landing et al., 2010—one study proposed an interpretation of Pywackia as an octocoral. No previous studies of the skeletal microstructure of Pywackia have employed the analysis of petrographic thin sections and high-magnification scanning electron microscopy. These two methods, with the addition of data from previous studies, are employed in this analysis of skeletal microstructure, a feature often important for higher-level taxonomic identification. Although many candidate groups were considered, Pywackia's distinctive pillar and laminae, porous skeleton like many Cnidaria, topology of the body walls, and growth of modules are consistent with a cnidarian affinity. Pywackia skeletons with primary microstructure were 100% phosphate mineral and were collected from a setting of pervasive phosphatic replacement, which leaves uncertainty as to the original skeletal composition. Pywackia is not assigned here to a cnidarian class and likely represents an early, rare, short-lived cnidarian evolutionary group.
Walcottaspis vanhornei (Walcott, 1914) is a large, late Cambrian trilobite with a unique pygidial morphology known only from a narrow outcrop belt of the St. Lawrence Formation in the Upper Mississippi Valley. Found in carbonate-rich layers within heterolithic facies that represent the toesets of a prograding shoreface, it is restricted to a single or small number of parasequences. Only four specimens of any of its sclerites have been illustrated previously. Here holaspid examples of all its biomineralized sclerites are described and illustrated, along with a morphometric analysis of cranidial landmarks and landmarks plus semilandmarks for the pygidium. Ontogenetic allometry accounts for 29% of the variance among holaspid cranidia and includes a relative shortening and narrowing of the palpebral lobe and a reduction in the relative length and width of the frontal area. Notable pygidial phenotypic variation occurs in the extent of the postaxial region and in the proportion of the structure occupied by the axis. Phylogenetic analysis suggests that W. vanhornei is sister taxon to Dikelocephalus minnesotensis Owen, 1852, which also occurs in the St. Lawrence Formation and has a broadly similar cephalon but distinctive trunk. The holaspid pygidium of W. vanhornei is uniquely characterized by the interpleural furrows of the first two segments becoming abruptly obsolete on approaching the axial furrow. Some pygidia show narrow, shallow, flat-bottomed grooves etched into the internal sides of the dorsal surface or doublure that apparently represent infestation of the live trilobite.
The Cambrian (Miaolingian; Wuliuan) Spence Shale Lagerstätte of northern Utah and southern Idaho is one of the most diverse Burgess Shale-type deposits of Laurentia. It yields a diverse fauna consisting of abundant biomineralized and locally abundant soft-bodied fossils, along a range of environments from shallow-water carbonates to deep-shelf dark shales. Panarthropods are the dominant component throughout the deposit, both in time and space, but whereas the trilobites and agnostoids are abundant, most of the soft-bodied taxa are only known from very few specimens. Additionally, the knowledge of soft-bodied panarthropods is currently largely limited to locations in the Wellsville Mountains of northeastern Utah. This contribution describes 21 new soft-bodied panarthropods from six locations, including the first occurrences of soft-bodied panarthropods in the High-Creek, Smithfield Creek, Spence Gulch, and Two-Mile Canyon localities. Additionally, we report the presence of bradoriids— i.e., Branchiocaris pretiosa Resser, 1929, Perspicaris? dilatus Robison and Richards, 1981, Naraoia? sp. indet., Thelxiope cf. T. palaeothalassia Simonetta and Delle Cave, 1975, and Tuzoia guntheri Robison and Richards, 1981—for the first time from the Spence Shale Lagerstätte; the first reported occurrence outside of the Burgess Shale for Thelxiope cf. T. palaeothalassia; and the first Wuliuan occurrence of Tuzoia guntheri. We also report on a new hurdiid carapace element and additional specimens of Buccaspinea cooperi? Pates et al., 2021, Dioxycaris argenta Walcott, 1886, Hurdia sp. indet., and Tuzoia retifera Walcott, 1912. This new material improves our understanding of the panarthropod fauna of the Spence Shale Lagerstätte and substantially increases our understanding of the distribution of the described taxa in time and space.
The suborder Phacopina, characterized by schizochroal eyes, is among the most common groups of trilobites in Devonian strata. The marine sediments of the Famennian in western Junggar, Xinjiang, contain abundant low-disparity phacopids, which have previously been designated to Omegops accipitrinus mobilis, Phacops circumspectans tuberculosus, and Omegops cornelius on the basis of small numbers of poorly preserved specimens. In this study, these phacopids were identified as two new species of Omegops, O. honggulelengensis n. sp. and O. xiangi n. sp., on the basis of nearly 200 well-preserved specimens. The intraspecific variations of eye lenses of these specimens were quantitatively analyzed. On the basis of differences in the total number, number of dorsoventral files, and arrangement of the eye lenses, the absence of lenses in the middle part of the visual surface, and asymmetry of the number and/or arrangement of lenses in the two eyes, it was concluded that the reasons for intraspecific variation in eye lenses of Late Devonian Omegops from western Junggar were different from previously described factors but were likely genetic or embryological malfunctions or abnormalities caused by pathological conditions. Diversity of lenses in the schizochroal eyes shows that the number and arrangement of eye lenses was not stable in Phacopina. Therefore, many specimens are needed for quantitative study to determine the true characteristics of the number or arrangement of eye lenses when these features are used in the systematic taxonomy of Phacopina.
Two specimens of Metaconularia manni (Roy, 1935) from the lower Middle Silurian Scotch Grove Formation (eastern Iowa) exhibit well-defined, relict soft parts replicated in silica. One of these specimens bears phosphatic periderm, whereas the other specimen is a mold. Present within the erect, undistorted apical region of the specimen preserving periderm, on opposite sides of the peridermal cavity, are two small, elongate masses of silica located near the midlines of two of the four faces. Present in the central portion of the other specimen, at a somewhat greater distance from the apex, are five pairs of hollow, elongate, keeled pouch-like bodies (hereafter pouches), the long axes of which converge on the center of the fossil. Each pair of pouches is associated with a short, narrow, gently curved or broadly U-shaped tube, also composed of silica. Additionally, two of the pouch/tube combinations are associated with a pair of rectilinear furrows that correspond to the paired internal carinae that straddled the conulariid's facial midlines. We interpret the paired pouches and short tubes in the moldic specimen as relic conulariid soft parts homologous, respectively, to the interradial gonads and retractor muscles of extant, stauromedusan and polypoid scyphozoan cnidarians. Unlike most conulariids, which exhibit four faces, this individual had five faces, an aberrant morphology known in one other conulariid. The two small masses in the other specimen are more difficult to interpret, but they, too, could be relic gonads or longitudinal muscles. These interpretations suggest that, as in certain extant scyphozoans, at least one conulariid lost the free-living, sexual medusoid life phase.
A diverse and well-preserved radiolarian assemblage from the Malongulli Formation, New South Wales, Australia, contains 13 species representing 10 genera and six families. One new genus, Wiradjuri, is introduced to accommodate pre-Devonian single-shelled entactiniid taxa, and one new species, Secuicollacta malongulliensis, is recorded together with some previously described forms. The microstructures of the “rotasphaerid structure/primary unit” and the “ectopic spicule” are investigated to validate their roles as fundamental units in the Secuicollactidae, together with comprehensive documentation of the previously enigmatic Pseudorotasphaera internal skeleton.
The results of this investigation suggest that, among all radiolarian genera that survived the Late Ordovician Mass Extinction event (LOME) and transitioned into the Silurian, Secuicollacta, Haplotaeniatum, and Palaeoephippium maintained stable body plans during the transition and were more successfully established. The selective advantages these lineages had during the LOME were most likely spontaneous outcomes of the mode of structural development involving sequential skeletogenesis and a tendency to evolve toward simpler body plans.
Evidence from the earliest-known crinoids (Tremadocian, Early Ordovician), called protocrinoids, is used to hypothesize initial steps by which elements of the calyx evolved. Protocrinoid calyces are composed of extraxial primary and surrounding secondary plates (both of which have epispires along their sutures) that are unlike those of more crownward fossil and extant crinoids in which equivalent calycinal plating is strongly organized. These reductions inspired several schemes by which to name the plates in these calyces. However, the primary-secondary systems seen in protocrinoids first appeared among Cambrian stem radial echinoderms, with primaries representing centers around which secondaries were sequentially added during ontogeny. Therefore, the protocrinoid calyx represents an intermediate condition between earliest echinoderms and crownward crinoids. Position and ontogeny indicate certain primaries remained as loss of secondaries occurred, resulting in abutting of primaries into the conjoined alternating circlets characteristic of crinoids. This transformative event included suppression of secondary plating and modification or, more commonly, elimination of respiratory structures. These data indicate subradial calyx plate terminology does not correspond with most common usage, but rather, supports an alternative redefinition of these traditional expressions. Extension and adoral growth of fixed rays during calyx ontogeny preceded conjoined primaries in earliest crinoids. Restriction with modification or elimination of calyx respiratory structures also accompanied this modification. Phylogenetic analyses strongly support crinoid origination from early pentaradiate echinoderms, separate from blastozoans. Accordingly, all Tremadocian crinoids express a distinctive aggregate of plesiomorphic and apomorphic commonalities; all branch early within the crinoid clade, separate from traditional subclass-level clades. Nevertheless, each taxon within this assemblage expresses at least one diagnostic apomorphy of camerate, cladid, or disparid clades.
The terminal Ediacaran Shibantan biota (~550–543 Ma) from the Dengying Formation in the Yangtze Gorges area of South China represents one of the rare examples of carbonate-hosted Ediacara-type macrofossil assemblages. In addition to the numerically dominant taxa—the non-biomineralizing tubular fossil Wutubus and discoidal fossils Aspidella and Hiemalora, the Shibantan biota also bears a moderate diversity of frondose fossils, including Pteridinium, Rangea, Arborea, and Charnia. In this paper, we report two species of the rangeomorph genus Charnia, including the type species Charnia masoni Ford, 1958 emend. and Charnia gracilis new species, from the Shibantan biota. Most of the Shibantan Charnia specimens preserve only the petalodium, with a few bearing the holdfast and stem. Despite overall architectural similarities to other Charnia species, the Shibantan specimens of Charnia gracilis n. sp. are distinct in their relatively straight, slender, and more acutely angled first-order branches. They also show evidence that may support a two-stage growth model and a epibenthic sessile lifestyle. Charnia fossils described herein represent one of the youngest occurrences of this genus and extend its paleogeographic and stratigraphic distributions. Our discovery also highlights the notable diversity of the Shibantan biota, which contains examples of a wide range of Ediacaran morphogroups.
Two rare, phosphatized, tubular microfossils of uncertain affinity, probably algal, are described from the Portfjeld biota (Ediacaran) of North Greenland. Portfjeldia aestatis n. gen. n. sp. preserves two tubules, one of which branches, within an annulated outer sheath. Its morphology can be compared to that of the much larger Ramitubus from the Weng'an biota of South China. An unnamed long, parallel-sided tubule occupied the postmortal cavity formed within diagenetically mineralized specimens of the cyanobacterium Jiangispirellus.