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Vase-shaped microfossil (VSM) assemblages from early diagenetic carbonate nodules in >742 ± 6 Ma black shales of the Chuar Group, Grand Canyon, provide evidence for affinities with testate amoebae. Not only are VSMs exceptionally preserved in Chuar rocks, they exhibit a much higher degree of morphological diversity than was previously known. Using the taxonomy of modern testate amoebae as a guide, nine new species and eight new genera of VSMs are described, augmenting the eight species and two genera already recognized. Taxa described here are Melanocyrillium hexodiademaBloeser, 1985, Trigonocyrillium horodyskii (Bloeser, 1985) n. comb., T. fimbriatum (Bloeser, 1985) n. comb., Cycliocyrillium simplex n. sp., C. torquata n. sp., Bonniea dacruchares n. sp., B. pytinaia n. sp., Trachycyrillium pudens n. sp., Palaeoarcella athanata n. sp., Hemisphaeriella ornata n. sp., Bombycion micron n. sp., and Melicerion poikilon n. sp. All of the test characters observed in VSM taxa (e.g., collars; indentations; hexagonal symmetry; lobed, triangular or invaginated apertures; curved necks) occur in modern testate amoeban taxa, though not always in the same combinations. Some VSM species have characters found today in diverse extant taxa, making it difficult to assess their relationships. A few species, however, have character combinations that closely approximate those found in specific genera of both lobose and filose testate amoebae, suggesting that at least stem group, and possibly crown group, representatives of these taxa were present ∼742 Ma.
These fossils indicate that ecosystems were diverse and complex, that eukaryotic biomineralization had already evolved, and that the last common ancestor of animals fungi had already appeared by ∼750 Ma.
Moderately diverse Middle Ordovician sponge faunas of Darriwilian (late Arenig to early Llanvirn) age have been discovered in outcrops in the Bachu-Kalpin area of the Tarim platform of Xinjiang, China. These are the first reported occurrences of early Paleozoic sponges from Xinjiang, China. These sponges occur in the Yijianfang and Dawangou Formations, which are of nearly the same age, but crop out in different areas of the platform margin. Fossil sponges discovered to date are the anthaspidellid lithistid sponges Archaeoscyphia minganensis (Billings, 1859); Hudsonospongia cyclostomaRaymond and Okulitch, 1940; Calycocoelia profunda sichuanensisDeng, 1990; Calycocoelia sp.; Pseudopalmatohindia sp.; Aulocopium sp.; Annulospongia tarimensis n. gen. and sp.; Rhopalocoelia kalpinensis n. sp.; Rhopalocoelia bachuensis n. sp.; and Zittelella xinjiangensis n. sp. They are preserved in reefal limestones and are associated with Calathium, cyanobacteria, and bryozoans, like in many North American assemblages.
Two new genera and three new species of shallow-marine, warm-water gastropods are reported from outcrops of various Cretaceous formations between British Columbia and Baja California. The potamidid Cedrosia pacifica new genus and species is from Turonian strata on Cedros Island, west coast of Baja California, Mexico. It is the earliest potamidid known from the rock record of the Pacific Slope. Alamirifica corona new genus and species, whose suprageneric relationships are uncertain, is from Turonian strata in southern California. The holotype has a round and rimmed aperture most similar to the photine buccinid NeoteronPilsbry and Lowe, 1932. The holotype also has a pyramidal spire most similar to some fossil cerithioideans traditionally placed in the potamidid PyrazusMontfort, 1810, but the type species of Pyrazus does not have a pyramidal spire. Future work might reveal that Alamirifica belongs to a new family.
Four other Pacific Slope species are tentatively assigned to Alamirifica: the Aptian A.? harrissi (Allison, 1955); the Coniacian A.? ursa new species; the late Coniacian to early Campanian A.? harveyi (Whiteaves, 1903); and the poorly preserved Turonian Alamirifica? sp.
As presently known, Cedrosia and Alamirifica were endemic to the study area, but they strongly resemble some Old World Tethyan gastropods. The distribution of A.? harveyi lends support to a relatively northern site of deposition for the Nanaimo Group.
Protamphisopus wianamattensis (Chilton, 1918) from the Middle Triassic (Anisian) Ashfield Shale in the Sydney Basin, Australia, is the earliest-known freshwater representative of the basal isopod suborder Phreatoicidea. In contrast, the late Paleozoic Palaeophreatoicidae species, which are morphologically distinct from extant families, are found in marine or estuarine facies. Comparison of Protamphisopus wianamattensis with living Phreatoicidea permits the external morphology of the fossils to be reconstructed and the species to be coded for cladistic analysis using a revised and expanded character set developed for living phreatoicideans. In resulting parsimonious trees as well as immediately suboptimal trees, Protamphisopus is nested within clades related to the family Amphisopodidae. Although not included in the analysis, the Late Permian Protamphisopus reichelti Malzahn (in Glaessner and Malzahn, 1962) appears to be a member of the Palaeophreatoicidae, rather than among the crown group of the Phreatoicidea. Therefore, a minimum age of Middle Triassic can be assigned to the basal branches within the phreatoicid crown group. The minimum age for the colonisation of fresh water by the suborder is also established although, given the advanced position of Protamphisopus wianamattensis in the cladograms, the habitat shift may have occurred earlier. The biogeographic distribution of extant Phreatoicidea on fragments of Gondwana is consistent with early Mesozoic origins for the major clades of this isopod suborder.
Parazophocrinus callosusStrimple, 1963, is redescribed as a cladid crinoid belonging to the Codiacrinidae. Parazophocrinus is a reasonably large cladid crinoid that is composed primarily of basal plates, radial plates, and oral plates; arms are absent; and the anal opening is along the side of the aboral cup. The radial plates are hypertrophied laterally, producing a disc-shaped aboral cup, and this very unusual crinoid is considered to be neotenic. Presumably, feeding in Parazophocrinus occurred only with tube feet projected through opened oral plates or from epidermal nutrient uptake. Typical codiacrinids may lack arms, may have the anal opening from the side of the aboral cup, and commonly have prominent oral plates; but in contrast to Parazophocrinus, they are small to very small in size. This small size and arrested development is considered progenetic.
Parazophocrinus is the second oldest genus in the Codiacrinidae. Apparently, when developmental controls broke down during the early evolution of this family, both neotenic and progenetic crinoids evolved. However, ultimately, the Parazophocrinus morphology, a large crinoid lacking arms, was not successful through time. Thus, although more than one heterochronic pathway was possible, functional and ecologic constraints determined which developmental pathway would have long-term success.
Emphereaster missouriensis new genus and species, Ambigaster, new genus, and Delicaster, new genus are assigned to the Carboniferous asteroid family Neopalaeasteridae Schuchert. The neopalaeasterids are similar to but separable from the Carboniferous Monasteridae, Calliasterellidae, and Fandasteridae, n. fam., in ambulacral and other characters. The several families indicate that late Paleozoic asteroids were diverse although poorly documented.
Similarities between late Paleozoic stem-group and post-Paleozoic crown-group asteroids allow argumentation on ossicular homologies. In species with only a single row of arm marginals, an earlier suggestion that certain disk ossicles are superomarginals is rejected. Enlarged proximal adambulacrals fill space on the actinal surface whereas actinal ossicles, generally lacking in Paleozoic asteroids, provide the space-filling service in crown-group asteroids.
The body wall beyond the ambulacral column and accessory ossicles traditionally have been stressed in the classification of asteroids of all ages. Because of body wall homoplasies, many older taxonomic concepts do not identify monophyletic late Paleozoic clades, nor do they indicate the derivation of the crown group. Ambulacral characters in contrast are conservative through long periods of geologic time, improving phylogenetic resolution as more taxonomic data become available. Now-available ambulacral skeletal data for certain Carboniferous genera suggest membership in lineages basal to the post-Paleozoic crown group.
Emphereaster missouriensis and most neopalaeasterids are stoutly constructed suggesting a defensive mechanism against durophagous chondrichthyan fish that co-occur with the holotype of Emphereaster. Abundant sponge spicules within the disk of the holotype suggest it fed on sponges, a prey type widely exploited by living asteroids.
Fourteen species of echinoids ranging in age from early to late Eocene, including four new species, are described from Texas. New taxa include Schizaster (Schizaster) caddoensis from the Reklaw and Weches Formations (Claiborne Group, middle Eocene), Schizaster (Schizaster) stenzeli and Eupatagus texanus from the Weches Formation, and Schizaster (Paraster) susana from the Caddell Formation (Jackson Group, upper Eocene). Fibularia meyeri (Aldrich, 1921) and Fibularia alabamensisCooke, 1959 are synonymized with Fibularia texana (Twitchell, 1915) from the Weches and Cook Mountain Formations (Claiborne Group, middle Eocene). Other reported species are Linthia hollandiBarry, 1942, from the Sabinetown Formation (Wilcox Group, lower Eocene); Gagaria sp., Protoscutella tuomeyi (Twitchell, 1915), Protoscutella mississippiensis mississippiensis (Twitchell, 1915), Maretia arguta (Clark, 1915), and Linthia? sp. from the Weches Formation; Spatangus? sp. and Eupatagus carolinensis? Clark, 1915 from the Cook Mountain Formation, and Periarchus lyelli (Conrad, 1834) from the Cook Mountain and Caddell Formations. These echinoids are sensitive indicators of depositional environment, in particular their distribution serves as a marker for stenohaline (open marine) environments and illustrates the biogeographic variability along the northeast Texas coast during the Eocene.
Late Ordovician jawed polychaete (Annelida) faunas from the type Cincinnatian region in the tri-state area of Indiana, Ohio, and Kentucky, North America, are discussed on the basis of an extensive and unique collection of more than 50,000 well-preserved scolecodonts. Approximately 40 to 50 multi-element species belonging to a dozen families are identified. Scolecodonts of polychaetes with prionognath, and particularly labidognath, type of jaw apparatus markedly dominate, whereas those of placognath and ctenognath taxa are very rare. The most common and/or characteristic genera include OenonitesHinde, 1879; KettneritesŽebera, 1935; Atraktoprion, Kielan-Jaworowska, 1962; RamphoprionKielan-Jaworowska, 1962; ProtarabellitesStauffer, 1933a; Kalloprion, Kielan-Jaworoska, 1962; Leptoprion, Kielan-Jaworowska, 1966; HadoprionEriksson and Bergman, 1998; MochtyellaKielan-Jaworowska, 1961; and Tetraprion? Kielan-Jaworowska, 1966. Members of the family Polychaetaspidae, particularly Oenonites species, generally dominate in abundance and number of species. The second most abundant family typically is either Ramphoprionidae or Paulinitidae. Overall, the taxonomic diversity seems to increase from the deeper water, shale-dominated, Edenian Kope Formation and upward in the succession to the shallower water, limestone-dominated, Richmondian Whitewater Formation. Five more or less distinct scolecodont associations were identified that are of potential biostratigraphic utility. Most families and genera identified have intercontinental distribution and can be identified also in approximately coeval strata of the Baltic paleocontinent. However, the faunal composition differs between these regions, especially at the species level.
Chondrichthyan spines and dermal denticles are reported from the Middle Pennsylvanian Minturn Formation, Eagle County, Colorado. The most common element is a dorsal finspine referred to Ctenacanthus buttersiSt. John and Worthen, 1883. Some of the specimens are more complete distally than the holotype and only previously figured specimen of C. buttersi. Less common remains include a dorsal finspine referred to Acondylacanthus nuperusSt. John and Worthen, 1883, a smooth-ribbed dorsal finspine close to “Ctenacanthus” furicarinatusNewberry, 1875, a spine fragment probably referrable to Physonemus sp., and two large-noded dorsal finspines probably referrable to two different species of Bythiacanthus. Dermal denticles are referred to Petrodus patelliformisM'Coy, 1848. Ctenacanthus buttersi finspines and some large cladodont teeth, referred to “Symmorium” occidentalis(Leidy), 1859, may belong to the same species. This conjecture is based mainly on the relative abundances of chondrichthyan teeth found at the same locality.
The fossil snake species Haasiophis terrasanctusTchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description of Haasiophis. The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges. Haasiophis cannot be considered a juvenile specimen of Pachyrhachis. The implications of the presence of well-developed hind limbs in Haasiophis, Pachyrhachis, and Podophis for the cladistic analysis of the phylogenetic interrelationships of these fossil snakes is discussed. The presence of well-developed hind limbs in Pachyrhachis and Haasiophis also creates methodological problems for the cladistic analysis of the phylogenetic relationships of these fossil snakes. Scenarios of snake origins are reviewed and found to be deficient in the absence of a well-corroborated hypothesis of snake relationships within Squamata.
The chelonian fauna of the Portezuelo Formation (Turonian-Coniacian), outcropping at Sierra del Portezuelo (Neuquén province, Argentina), is reported. Two new taxa of pleurodiran turtles are described. One of them is Prochelidella portezuelae new species, a short-necked chelid closely related to extinct species of the Lohan Cura (Albian), Candeleros (Cenomanian), and Bajo Barreal (Turonian) formations from northwestern and central Patagonia, and to the extant species of the genus Acanthochelys. The other is Portezueloemys patagonica new genus and species, a member of the epifamily Podocnemidoidea, and is considered the sister group of the family Podocnemididae. This discovery confirms the coexistence in northwestern Patagonia of a north gondwanan component (Pelomedusoides) and a south gondwanan element (Chelidae) during the Turonian-Coniacian.
Land hermit crabs (Coenobitidae) are widespread and abundant in Recent tropical and subtropical coastal environments, yet little is known about their fossil record. A walking trace, attributed to a land hermit crab, is described herein as Coenobichnus currani (new ichnogenus and ichnospecies). This trace fossil occurs in an early Holocene eolianite deposit on the island of San Salvador, Bahamas. The fossil trackway retains the distinctive right and left asymmetry and interior drag trace that are diagnostic of modern land hermit crab walking traces. The overall size, dimensions and shape of the fossil trackway are similar to those produced by the modern land hermit crab, Coenobita clypeatus, which occurs in the tropical western Atlantic region. The trackway was compared to other arthropod traces, but it was found to be distinct among the arthropod traces described from dune or other environments. The new ichnogenus Coenobichnus is proposed to accommodate the asymmetry of the trackway demarcated by left and right tracks. The new ichnospecies Coenobichnus currani is proposed to accommodate the form of the proposed Coenobichnus that has a shell drag trace.