David M. Rohr

Oldest termite nest from the Upper Cretaceous of west Texas

Wood borings and insect frass from the Upper Cretaceous of Texas are interpreted to be the oldest known termite nest, the oldest known termite fecal pellets, and one of the few examples of trace-fossil evidence of social behavior in insects. It illustrates a form of behavioral fixity insofar as coprolite form, feeding habits, and substrate are concerned.

Silurian-age fossils from the Paleozoic Paraná Basin, southern Brazil

This paper is the first example of how Middle Ordovician to Lower Silurian land plant microfossils, commonly present in otherwise unfossiliferous or poorly fossiliferous, nonmarine, or nearshore facies, may be used for biostratigraphic purposes. This new information permits the recognition of a broad regional unconformity extending from the Parana Basin to Arabia. Conclusive evidence for the presence of Silurian rocks in the Parana Basin of southeastern Brazil is developed. The age is based on organic microfossils, including tetrahedral tetrads of land-plant spores and phytoplankton (“acritarchs” and prasinophytes) that were recovered from body- and trace-fossil-bearing rocks of the northeastern Parana Basin. Both the plant spores and phytoplankton indicate an Early Silurian (early Llandoverian) age, and support the previous permissive Silurian age assignment based on the trace fossil Arthrophycus and invertebrate body fossils.

Maclurina manitobensis (Whiteaves) (Ordovician Gastropoda); the largest known Paleozoic gastropod

The concept of the Ordovician gastropod genus Maclurites Le Sueur, 1818, at present includes much variation. Maclurina Ulrich in Ulrich and Scofield, 1897, is removed as a subjective synonym of Maclurites and reestablished as a separate genus. Species of Maclurites with spiral grooves on the outer whorl surface and a relatively small umbilicus are transferred to Maclurina. Maclurina manitobensis (Whiteaves, 1890) forms a distinctive part of the Late Ordovician-age “Arctic Ordovician fauna.” An unusually large specimen (25 cm in diameter) from the Bighorn Dolomite (Upper Ordovician), Wyoming, is illustrated; this Wyoming specimen is the volumetrically largest Paleozoic gastropod ever reported.

Ordovician (Whiterockian) gastropods of Nevada; Bellerophontoidea, Macluritoidea, and Euomphaloidea

Gastropods are abundant in the Middle Ordovician (Whiterockian) Antelope Valley Formation of Nevada. Because Whiterockian rocks are absent in much of central and eastern North America, these Nevada gastropods play a significant role in understanding the Early to Middle Ordovician transition of the class. The shell and operculum of a new genus and species of macluritoid, Monitorella auricula , is described. New euomphaloid taxa include Walcottoma frydai n. gen. and sp., Rossospira harrisae n. gen. and sp., Barnesella measuresae n. sp., Helicotoma gubanovi n. sp., Lytospira yochelsoni n. sp., and Malayaspira hintzei n. sp.

Late Ordovician nearshore faunas and depositional environments, northwestern Maine

The Little East Lake Formation represents a spectrum of Late Ordovician (Ashgill) nearshore environments. These physical environments are characterized by a variety of quartz- and feldspar-rich sandstone and slate. Depositional environments include neritic nearshore, beach, tidal flat, and alluvial(?). The beach and neritic nearshore environments contain a variety of fossil invertebrates. The majority of the brachiopod fauna is confined to two taxa: Eodinobolus rotundus Harper, 1984, and Dalmanella testudinaria ripae Mitchell, 1978 (in Cocks, 1978). Some of the specimens have been broken and abraded suggesting transport within the beach swash zone. Gastropods include Lophospira cf. L. milleri (Hall), Lophospira(?), Trochonemella cf. T. notabilis (Ulrich and Scofield), and Daidia cerithioides (Salter). Tidal-flat environment contains the trace fossils Palaeophycus and Planolites. The Late Ordovician (Caradoc and Ashgill) sedimentary basins developed subsequent to the collisional Taconian orogeny, wherein an arc accreted to the eastern Laurentian margin. Prior paleomagnetic reconstructions place the southeastern continental margin of Laurentia at approximately 25° south latitude during the Late Ordovician. Using these reconstructions, the siliciclastic Ashgill rocks discussed here would have been deposited in an elongated, northeast-trending basin on the southeastern Laurentian margin. The fauna developed along this margin, but in contrast to possibly adjacent Irish and Scottish assemblages, was located in much shallower water.

Silurian Gastropoda from Southeastern and West-Central Alaska

Abstract Additional Silurian (Ludlovian) gastropods are described from the Heceta Formation in the Alexander terrane on Prince of Wales Island, southeastern Alaska. Species include Spinicharybdis krizi n. sp., Spinicharybdis boucoti n. sp., Morania wagneri n. sp., Haplospira craigi n. sp., Australonema sp., Pachystrophia cf. gotlandica (Lindström,1884), and Medfrazyga gilmulli n. sp. An additional new Silurian species, Morania nixonforkensis n. sp., is described from the Nixon Fork subterrane of the Farewell terrane of west-central Alaska. The spine-bearing Spinicharybdis is placed into a new subfamily Spinicharybdiinae together with Hystricoceras Jahn, 1894. Joint occurrences of genera Beraunia, Coelocaulus, and Morania, as well as members of subfamily Spinicharybdiinae in the gastropod fauna from the Heceta Formation, support its close relationship with gastropod fauna of Bohemia. Additionally, the occurrence of the genus Medfrazyga suggests a faunal link between the Alexander and Farewell terranes of Alaska. Medfrazyga gilmulli n. sp. is the oldest known and the only early Paleozoic member of the family Palaeozygopleuridae.

Chapter 15 Biogeography of Ordovician and Silurian gastropods, monoplacophorans and mimospirids

Abstract The biogeographical distribution of Ordovician and Silurian gastropods, monoplacophorans and mimospirids has been analysed on a generic level. The dataset contains 334 genera and 2769 species, yielding 1231 records of genera with 2274 occurrences worldwide. There is a bias towards eastern Laurentia, Baltica and Perunica records. Some 53.1% of the records are Ordovician. The study demonstrates that these molluscs are well suited to being used to improve understanding of Ordovician and Silurian biogeographical provinciality. Specific points are that: a Lower Ordovician assemblage is evident in Laurentia; the fauna of the Argentinean Precordillera is Laurentian until the Darriwilian, when taxa are shared with North China; Late Silurian gastropods from the Alexander terrane (SE Alaska) are unknown in Laurentia, but support a rift origin of this terrane from NE Siberia; Perunica, Ibero-Armorica and Morocco cluster together throughout the Ordovician but Perunica and Morocco are closer; Darriwilian–Sandbian deep-water Bohemian taxa occur in Baltica; a Laurentian–Baltica proximity is unsupported until the Silurian; Siberia clusters with North China and eastern Laurentia during the Tremadocian–Darriwilian; during the Gorstian–Pridoli Siberia clusters with the Farewell and Alexander terranes; North China may have been close to Laurentia and the Argentinean margin of Gondwana; and the affinity of Tarim taxa is problematic.

SHELL HETEROSTROPHY IN EARLY ORDOVICIAN MACLURITELLA KIRK, 1927 AND ITS IMPLICATIONS FOR PHYLOGENY AND CLASSIFICATION OF MACLURITOIDEA (GASTROPODA)

Abstract Study of the oldest macluritid gastropod, Macluritella stantoni Kirk, 1927 from the Lower Ordovician of Colorado, has revealed that its early whorls are openly and dextrally coiled, in contrast to those in later teleoconchs which are sinistrally coiled. This is the first documentation of heterostrophic coiling in members of the Macluritoidea, which have been considered to be dextrally hyperstrophic. Juvenile M. stantoni may be interpreted as dextrally orthostrophic and, thus, it had the same type of soft-body-shell arrangement as the vast majority of living and fossil gastropods. This intepretation also suggests that the Macluritoidea evolved from the dextrally orthostrophic gastropods, and their dextral hyperstrophy is derived and not a primary feature. In addition, occurrence of shell heterostrophy in M. stantoni brings additional evidence that the Macluritoidea and Onychochiloidea are not closely related taxa. Relationships between the Macluritoidea and Euomphaloidea are still uncertain. This study provides the oldest evidence (Early Ordovician) for shell heterostrophy in the class Gastropoda.

MIDDLE ORDOVICIAN (WHITEROCKIAN) GASTROPODS OF WESTERN NEWFOUNDLAND: MACLURITOIDEA AND EUOMPHALOIDEA

Abstract Gastropods that occur in the Anomalorthis brachiopod zone in the Spring Inlet Member of the Table Point Formation and in the Orthidiella brachiopod zone of the Shallow Bay Formation of the Cow Head Group are documented. Gastropods from western Newfoundland comprise part of the Toquima-Table Head fauna, and six of the seven genera described here are also found in Whiterockian strata of Nevada. Four species assigned to Monitorella Rohr, 1994, Maclurites Le Sueur, 1818, and Malayaspira Kobayashi, 1958, originally described by E. Billings in 1865 from Middle Ordovician (Whiterockian) strata of Newfoundland are revised. Five species of Helicotoma Salter, 1859, Malayaspira Kobayashi, 1958; Lytospira Koken, 1896; Rossospira Rohr, 1994; and Pachystrophia Perner, 1903, not previously reported from Newfoundland are also described. The probable opercula of Monitorella crenulata (Billings, 1865), and Maclurites emmonsi (Billings, 1865), are also illustrated for the first time.

Late leonardian plants from west Texas: the youngest paleozoic plant megafossils in north america.

Abundant Permian plant megafossils were discovered in the Del Norte Mountains of Brewster County, Trans-Pecos Texas. The flora is dominated by a new and distinctive type of gigantopteroid leaves. Marine invertebrates are closely associated, and this admixture of continental and marine fossils indicates a deltaic depositional setting, probably on the southern margin of the Permian Basin. Conodonts indicate correlation with the uppermost Leonardian Road Canyon Formation in the Glass Mountains. These are the youngest Paleozoic plant megafossils known in North America; they add an important paleontological element to the classic Permian area of this Continent.