NEW EMSIAN (LATE EARLY DEVONIAN) GASTROPODS FROM ...

J. Paleont., 78(1), 2004, pp. 111–132 Copyright q 2004, The Paleontological Society 0022-3360/04/0078-111$03.00

NEW EMSIAN (LATE EARLY DEVONIAN) GASTROPODS FROM LIMESTONE MOUNTAIN, MEDFRA B-4 QUADRANGLE, WEST-CENTRAL ALASKA (FAREWELL TERRANE), AND THEIR PALEOBIOGEOGRAPHIC AFFINITIES AND EVOLUTIONARY SIGNIFICANCE ´ DA JIRˇÍ FRY

AND

ROBERT B. BLODGETT

Czech Geological Survey, Kla´rov 3, 118 21 Praha 1, Czech Republic, and Department of Paleontology, Universita¨t Hamburg, Bundesstraße 55, D-20146 Hamburg, Germany, ,[email protected]., and Department of Zoology, Oregon State University, Corvallis 97331, ,[email protected]. ABSTRACT—A significant number of small-sized gastropods are described from Emsian (late Early Devonian) strata on the south flank of Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska, providing the first detailed taxonomic inventory of Emsian gastropods from the Farewell terrane of southwestern and west-central Alaska. The fauna is distinctly of Old World Realm character, and contains not a single species in common with Emsian faunas of nearby nonaccreted rocks of western Canada and east-central Alaska (‘‘Western Canada Province’’ of Blodgett et al., 2001a). The genera Balbinipleura Bandel and Fry´da, 1996 and Nanochilina Fry´da, 1998, as well as the subgenus Palaeozygopleura (Rhenozyga) Fry´da, 2000, are reported for the first time in the Devonian of the Western Hemisphere. The gastropod fauna includes members of three (i.e., Archaeogastropoda, Caenogastropoda, and Heterobranchia) of the five modern gastropod subclasses, illustrating that these gastropod lineages were separated from each other since the Early Devonian. New taxa include the new genera Arctozone, Farewellia, and Medfrazyga, represented by the new species Arctozone cooki, Farewellia heidelbergerae, and Medfrazyga clauticae. Further new species include Quadricarina (Quadricarina?) noklebergi, Balbinipleura krawczynskii, Decorospira lepaini, Decorospira? minutula, Palaeozygopleura (Rhenozyga) reifenstuhli, and Nanochilina gubanovi. In addition, the following previously described gastropods are also discussed and illustrated: Alaskiella medfraensis Fry´da and Blodgett, 1998; Alaskacirrus bandeli Fry´da and Blodgett, 1998; and Kuskokwimia moorei Fry´da and Blodgett, 2001a.

INTRODUCTION

paper we describe a number of significant new smallsized gastropod taxa present in a richly diverse, silicified gastropod fauna discovered in Emsian strata on the south flank of Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska (Fig. 1). Other gastropods previously described or illustrated from this locality can be found in Blodgett et al. (1988) [Euomphalopterus sp., Sinistracirsa sp. (5Alaskacirrus bandeli Fry´da and Blodgett, 1998), and Hesperiella sp. (5Alaskiella medfraensis Fry´da and Blodgett, 1998)], Blodgett and Rohr (1989) [Chlupacispira spinosa Blodgett and Rohr], Blodgett and Johnson (1992) [Straparollus (Eleutherospira) medfraensis Blodgett and Johnson], Fry´da and Blodgett (1998) [Alaskacirrus bandeli and Alaskiella medfraensis], and Fry´da and Blodgett (2001a) [Kuskokwimia moorei]. The gastropods described here are particularly important because their exceptionally fine preservation permits study of intact protoconchs, providing critical new data on the phylogeny of many larger gastropod taxa. In addition, they also provide a better glimpse into the biotic composition of Emsian (a time interval of heightened global endemism) gastropod faunas from Alaskan accretionary terranes, thereby, providing invaluable biogeographic information on the probable origins of some of these terranes.

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AGE AND GEOLOGICAL SETTING

The described gastropod taxa are from a highly diverse, gastropod-dominated fauna recovered from a 1.5 m thick, silicified, richly fossiliferous rubble zone in an unnamed Devonian limestone unit. The locality (field number 83RB9) occurs on the south flank of Limestone Mountain, SW¼, NE¼, sec. 26, T26S, R23E, Medfra B-4 quadrangle, west-central Alaska, latitude 638169010N, longitude 1548329440W (see Fig. 1 for location). This silicified horizon occurs 13.7–15.2 m above the base of a carbonate sequence that is at least 100 m thick. About 40 species of gastropods, most of which are relatively small sized, dominate the fauna. Other molluscs are present but less common, including bivalves, scaphopods, orthoconic cephalopods, tentaculitids, and small, indeterminate juvenile ammonoids. Other accessory faunal

elements include brachiopods, solitary rugose and tabulate corals, lamellar stromatoporoids, and ostracodes. The overall aspect of the fauna is indicative of an undifferentiated Emsian (late Early Devonian) age. On the basis of regional stratigraphic correlations and faunal composition, the host beds appear to be slightly younger than the earliest Emsian (Polygnathus dehiscens Zone) Soda Creek Limestone (Blodgett et al., 2000), the type section of which is situated to the northeast in the Medfra B-3 quadrangle. The dominance of the fauna by a highly diverse assemblage of gastropods, together with the abundance of the tubular stromatoporoid genus Amphipora in underlying and overlying strata, indicates a relatively shallow-water (shallow part of the photic zone), inner carbonate platform environment. The locality is situated within the Nixon Fork terrane of Patton (1978), which was recognized by Decker et al. (1994) to be genetically related with the adjacent Mystic and Dillinger terranes. All of these terranes were reduced in rank to subterranes of a larger terrane, termed by Decker et al. (1994) as the Farewell terrane (see Fig. 1.1 for location). On the basis of the paleobiogeographic affinities of various early and middle Paleozoic (Cambrian-Devonian) age faunas from the component subterranes, the Farewell terrane is most closely allied with Siberia (notably Kolyma, Taimyr, Kuznetsk Basin), as well as the Urals. It seems most likely that this terrane represents a continental margin sequence that has been rifted away from the Siberian continent (Blodgett and Brease, 1997; Blodgett, 1998; Blodgett and Boucot, 1999; Blodgett et al., 2002; Boucot and Blodgett, 2001; GarciaAlcalde and Blodgett, 2001). In addition, recently published data on biogeographic affinities of the early Mesozoic (Triassic) gastropod fauna of the Alaskan terranes (Chulitna, Farewell, Alexander, and Wrangellia) suggest that the Chulitna-Farewell-Alexander terrane assemblage was separated during Late Triassic time by a reproductively significant distance from the Wrangellia-Wallowa terrane couplet in differing tropical areas within the Panthalassa Ocean (Blodgett et al., 2001b; Blodgett and Fry´da, 2001; Fry´da and Blodgett, 2001b). These facts suggest that the wandering path of the Farewell terrane from its supposed position in

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FIGURE 1—Generalized maps showing location of the fossil locality in the Farewell terrane of west-central Alaska. 1, Arrow shows a position of the Limestone Mountain (LM) within the Farewell terrane. 2, Exact location of the fossil locality (field number 83RB9) that occurs on the south flank of Limestone Mountain, SW¼, NE¼, sec. 26, T26S, R23E, Medfra B-4 quadrangle, west-central Alaska. Numbered sections are one mile (1.61 km) square.

early Paleozoic time as a continental margin sequence of the Siberian continent to its present position in west-central Alaska was probably very complex. BIOGEOGRAPHIC AFFINITIES OF THE FAUNA

The study of the biogeographic distribution of Devonian gastropods has been undertaken later (Forney et al., 1981; Blodgett, 1992; Blodgett and Fry´da, 1999; Blodgett and Johnson, 1992; Blodgett et al., 1986, 1987, 1988, 1990) than has that of betterknown groups such as brachiopods, rugose corals, and trilobites. Nonetheless, the fundamental biogeographic patterns are very similar to those of the aforementioned faunal groups. The overall aspect of the Limestone Mountain gastropod fauna is Old World Realm. About half the generic or subgeneric taxa found in the Limestone Mountain fauna (Blodgett et al., 1988; Blodgett and Rohr, 1989; Blodgett and Johnson, 1992; Fry´da and Blodgett, 1998, 2001a; and present paper) are restricted to the Old World Realm faunas of Emsian and/or Middle Devonian age. The Old World Realm generic or subgeneric taxa from Limestone Mountain include Euomphalopterus Roemer, 1876; Straparollus (Eleutherospira) Blodgett and Johnson, 1992; Quadricarina (Quadricarina) Blodgett and Johnson, 1992; Balbinipleura; Decorospira Blodgett and Johnson, 1992; Palaeozygopleura (Rhenozyga); and Nanochilina. Slightly younger (Eifelian) age gastropods from the Farewell terrane are also of Old World Realm character (Blodgett, 1992, 1993; Blodgett and Cook, 2002; Blodgett and Rohr, 1989; Blodgett et al., 2002). The Limestone Mountain fauna is from the Farewell terrane (Decker et al., 1984) of southwestern and west-central Alaska, an accreted terrane that according to its Paleozoic fauna and flora appears to probably represent a rifted continental margin sequence from Siberia or the Urals (Blodgett, 1998; Blodgett and Boucot, 1999; Blodgett et al., 2002; Boucot and Blodgett, 2001; GarciaAlcalde and Blodgett, 2001). Of special paleobiogeographic note is the fact that the Emsian gastropod fauna of the Farewell terrane

shares not a single species with Emsian faunas of nearby nonaccreted rocks of western Canada and east-central Alaska (Western Canada Province of Blodgett et al., 2001a) or with that of the Great Basin (Nevada Province). The Western Canada Province was part of the Old World Realm during Emsian time, while the Nevada Province belonged to the Eastern Americas Realm during Pragian-early Emsian time, but whose gastropod fauna subsequently became more Old World Realm in character during later Emsian time. The most similar Emsian age gastropod fauna from North America is that of Kasaan Island, off the eastern coast of Prince of Wales Island, southeast Alaska (Blodgett and Fry´da, personal observation). The Kasaan Island fauna is from the Alexander terrane, another accreted terrane that appears to be of Siberian and/ or Uralian affinity (Blodgett et al., 2002). The Kasaan Island gastropod fauna has not yet been subject to a detailed taxonomic study, but like the fauna of Limestone Mountain contains a number of genera that are known primarily from European parts of the Old World Realm during the later part of the Early Devonian (notably the Czech Republic, Carnic Alps, and the Massif Armoricain), such as Oriostoma Munier-Chalmas, 1876; Tubina Owen, 1859; and Coelocaulus Oehlert and Oehlert, 1888. SYSTEMATIC PALEONTOLOGY

Repository information.CˇGU JF refers to the Czech Geological Survey (Prague), Jirˇ´ı Fry´da collection, the repository where the type specimens are deposited. Class GASTROPODA Cuvier, 1797 Subclass ARCHAEOGASTROPODA Thiele, 1925 Discussion.Modern Archaeogastropoda may be characterized by several apomorphic features of their soft body parts (see Salvini-Plawen and Haszprunar, 1987; Haszprunar, 1993; SalviniPlawen and Steiner, 1996; and Ponder and Lindberg, 1997, for reviews). However, the name Archaeogastropoda has been used

FRY´DA AND BLODGETT—DEVONIAN GASTROPODS FROM ALASKA differently since Thiele (1925) established it and there is still no consensus among neontologists on how to use the term (see discussion of Hickman, 1988 and Haszprunar, 1993). Usage of this name for fossil gastropods is even more difficult, because there are no data on their soft part anatomy. In addition, the limited number of available shell features as well as the frequent homoplastic similarity of their shells considerably restricts correct determination of the phylogenetic relationships between fossil and modern archaeogastropods. On the other hand, the mode of early shell development as well as shell structure can help to determine the higher taxonomic position of some fossil gastropod groups. Unfortunately, the rarity of Paleozoic gastropods with either wellpreserved protoconchs or shells limits the utility of these shell characters. Among modern marine gastropods there are only two groups, Patellogastropoda (5Docoglossa) and Archaeogastropoda (Vetigastropoda 5 Rhipidoglossa), which never produce a true larval shell (protoconch II), and their protoconch consists only of an embryonic shell (protoconch I; Bandel, 1982). Undoubted members of the Patellogastropoda are unknown from the Paleozoic (Hedegaard et al., 1997; Fry´da, 2001). For this reason the majority of Paleozoic gastropods with an archaeogastropod-type protoconch were thought to belong to the Archaeogastropoda. However, Ponder and Lindberg (1997) have suggested that the Patellogastropoda probably were derived from Paleozoic coiled ancestors. In addition, it should also be considered that the diversity of the Paleozoic archaeogastropods was probably higher (similar to the present) and that they included many extinct groups (Fry´da, 1999a). The presence (or absence) as well as the nature of the selenizone have been considered to be very important shell features for family-level classification of Paleozoic archaeogastropods (see Wenz, 1938; Knight et al., 1960). Bandel and Fry´da (1996) analyzed these features and pointed out that the family-level classification of Paleozoic slit-bearing archaeogastropods used by Knight et al. (1960) is of little use and needs revision. In addition, Paleozoic slit-bearing gastropods include groups other than members of the Archaeogastropoda. Nu¨tzel and Bandel (2000) described late Paleozoic slit-bearing gastropod genera that according to their protoconch morphology belonged without doubt in the Caenogastropoda. Taken together, the higher-level position of the majority of Paleozoic archaeogastropod genera is uncertain and their present classification (Knight et al., 1960) needs a new revision. Nevertheless, we use this classification here because no newer classification, involving all Paleozoic gastropods, has been previously published. Superfamily PLEUROTOMARIOIDEA Swainson, 1840 Family EOTOMARIIDAE Wenz, 1938 Genus QUADRICARINA Blodgett and Johnson, 1992 Type species.Quadricarina glabrobasis Blodgett and Johnson, 1992, from the Eifelian of Nevada. Other included species.Quadricarina (Quadricarina) n. sp. A Blodgett and Johnson, 1992 (Eifelian); Quadricarina (Blodgettina?) n. sp. B Blodgett and Johnson, 1992 (Eifelian); Q. (Q.?) lenticularis (Goldfuss, 1844) (Givetian); Q. (B.) reticulata Fry´da, 2000, (Givetian); Q. (Q.?) noklebergi n. sp. (Emsian). Discussion.Blodgett and Johnson (1992) included four Middle Devonian species in their new genus. Three species, including its type species Quadricarina glabrobasis, come from the Eifelian of Nevada, the fourth is Pleurotomaria lenticularis Goldfuss, 1844, from the Givetian (late Middle Devonian) of Germany. The turbiniform, phaneromphalous shells of Quadricarina species are characterized by a selenizone bordered by two pairs of revolving cords. The gently concave selenizone is situated at mid-whorl height and the shell ornament consists of fine collabral ribs. Later,

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Fry´da (2000) described another species of Quadricarina from the Givetian (late Middle Devonian) of Germany, which differs from previously described species of Quadricarina in having a low spire with a distinctly raised selenizone and reticulate shell ornamentation. For this reason, he placed it in a new subgenus, Quadricarina (Blodgettina), of the latter genus. Quadricarina (Quadricarina?) noklebergi n. sp. has a much higher spire than all other species of Quadricarina. The type species of Quadricarina (Quadricarina), Q. (Q.) glabrobasis Blodgett and Johnson, 1992, has a spiral angle of about 110 degrees. The type species of Quadricarina (Blodgettina), Q. (B.) reticulata, has a lower spire and its spiral angle is about 115 degrees. In contrast to these species, the spiral angle in Quadricarina (Quadricarina?) noklebergi n. sp. is about 65 degrees. In this respect it resembles the late Emsian (late Early Devonian) Paraoehlertia parva Fry´da, 1998a, which is the type species of Paraoehlertia Fry´da, 1998a and the selenizone of which (see Fry´da, 1998a, plate 1, figs. 1–2) is also bordered by two pairs of revolving cords like that of Quadricarina. However, Quadricarina (Quadricarina?) noklebergi n. sp., as well as other species of Quadricarina, have a narrower selenizone and a cyrtoconoid shell. A cyrtoconoid shell and selenizone bordered by two pairs of revolving cords are shell features also found in the Early Devonian genus Oehlertia Perner, 1907. Species of the latter genus have, in contrast to Quadricarina and Paraoehlertia, low whorls and a deep and wide umbilicus. Taken together, Quadricarina (Quadricarina?) noklebergi n. sp. fits best among known eotomariid genera with Quadricarina (Quadricarina). However, it shares some shell features with Quadricarina (Blodgettina) (reticulate ornamentation) and Paraoehlertia (relatively high spired shell). For this reason, we tentatively place it in Quadricarina (Quadricarina). A more detailed morphological analysis is not made at this time because several undescribed species belonging to this group are known. QUADRICARINA (QUADRICARINA?) NOKLEBERGI new species Figure 2.1–2.5 Diagnosis.Small, high spired species of Quadricarina with distinctly cyrtoconoid spire and fine reticulate ornament; diameter of protoconch about 0.23 mm. Description.Small, turbiniform, distinctly cyrtoconoid shell having up to six whorls; spire higher than wide; selenizone situated just above lower suture and forming shell periphery on adult whorls; width of selenizone about one-fourth of distance between sutures; selenizone slightly protruding above the whorl surface and bordered by two pairs of revolving cords; distance of outer pair of cords forming margin of selenizone about three times higher than the width of selenizone; inner pair of cords thinner than outer cords; upper and lower whorl surfaces convex; shell base rounded and phaneromphalous; whorl joins preceeding whorl just below selenizone; selenizone higher on more juvenile whorls and starting from about end of first whorl (Fig. 2.1–2.3); shell ornamentation consisting of fine spiral and collabral threads forming a reticulate pattern (Fig. 2.5); diameter of protoconch about 0.23 mm (Fig. 2.4). Etymology.In honor of Warren J. Nokleberg, Western Region, U.S. Geological Survey, Menlo Park, California. Types.Holotype, CˇGU JF 785, Figure 2.2, 2.4–2.5; paratype A, CˇGU JF 786, Figure 2.1; paratype B, CˇGU JF 787, Figure 2.3; paratype C, CˇGU JF 813; and paratype D, CˇGU JF 814. Occurrence.Known only from its type locality. Discussion.Quadricarina (Quadricarina?) noklebergi n. sp. differs from all other species of Quadricarina by its much higher and distinctly cyrtoconoid spire. From species of Quadricarina (Quadricarina) it also differs in having a finely reticulate shell ornamentation. Species of Quadricarina (Blodgettina) have a

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FIGURE 2—Quadricarina (Quadricarina?) noklebergi n. sp. 1, Oblique view on paratype A, CˇGU JF 786, 325; 2, 4–5, holotype, CˇGU JF 785; 2, lateral view, 329; 4, detailed view showing protoconch morphology, 385; 5, apical view showing reticulate shell ornamentation, 328; 3, paratype B, CˇGU JF 787, 325.

very low spire and more raised selenizone in contrast to that of Quadricarina (Quadricarina?) noklebergi n. sp. Quadricarina (Quadricarina?) noklebergi n. sp. is the first species of Quadricarina in which a preserved protoconch was found. The diameter of its protoconch (about 0.23 mm) is slightly smaller than that of Paraoehlertia parva (0.34 mm in the type species of Paraoehlertia). Quadricarina (Quadricarina?) noklebergi n. sp. is the oldest and first known Early Devonian species of Quadricarina.

Genus BALBINIPLEURA Bandel and Fry´da, 1996 Type species.Balbinipleura bohemica Bandel and Fry´da, 1996, from the Pragian (middle Early Devonian) Praha Formation of the Prague Basin. Other species included.Early Carboniferous Balbinipleura koninckii Bandel and Fry´da, 1996; Givetian (late Middle Devonian) Balbinipleura? sextalineata Heidelberger, 2001; and Emsian (late Early Devonian) Balbinipleura krawczynskii n. sp. Discussion.Balbinipleura differs from most known genera

FRY´DA AND BLODGETT—DEVONIAN GASTROPODS FROM ALASKA usually placed in the family Eotomariidae by the two spiral ribs present above and below the selenizone. The Devonian Bembexia Oehlert and Oehlert, 1888 resembles Balbinipleura in the latter shell character, but differs in having weaker collabral ribs and a wider spiral angle. The Permian genus Pagodina Wanner, 1942 has a whorl profile similar to Balbinipleura, but differs in having many spiral ribs on its base. The Silurian genus Ulrichospira Donald, 1905 differs from Balbinipleura by the absence of spiral ribs on its upper whorl surface. The Middle Devonian genus Kersadiella Blodgett, Fry´da, and Racheboeuf, 1999 is probably the closest genus to Balbinipleura, but differs in having finer collabral ribs and a somewhat differing whorl profile with a much lower situated selenizone on the outer whorl surface of the spiral whorls. In addition, Kersadiella also differs in having its collabral ribs initially inclined forward beneath the selenizone, whereas in Balbinipleura they are inclined backwards (compare Bandel and Fry´da, 1996, fig. 2, and Blodgett et al., 1999, fig. 6.3). Balbinipleura krawczynskii n. sp. differs from the other described species of Balbinipleura in not having collabral ribs below the selenizone. Its weaker collabral ribs also resemble those in Kersadiella. The type and hitherto only known species of Kersadiella has, however, a much lower selenizone. On the other hand, Balbinipleura krawczynskii n. sp. has exactly the same morphology and development of the first three whorls as the type species of Balbinipleura (see description below and compare figs. 2.4–8 in Bandel and Fry´da, 1996, and Fig. 3.12 here). For this reason we place this new species in the genus Balbinipleura. BALBINIPLEURA KRAWCZYNSKII new species Figure 3.6–3.9, 3.12 Diagnosis.Small species of Balbinipleura lacking collabral ornamentation below the selenizone; collabral ribs above selenizone orthocline and regularly spaced; having a spiral angle of about 45 degrees; diameter of protoconch about 0.25 mm. Description.Small, turbiniform, dextrally coiled shell with up to five whorls; spiral angle of about 45 degrees; sutural slope angle of impressed suture about 7 degrees; concave selenizone bordered by two spiral cords, the lower of which forms the periphery; two accessory sharp spiral cords present, one located high on upper whorl face between upper suture and selenizone, the other visible just above the lower suture; selenizone lacking any ornamentation; ornament above selenizone consists of orthocline and regularly spaced, collabral ribs that cross the upper spiral cord and form distinct tubercles at their points of intersections; upper spiral cord lies closer to selenizone than to upper suture; lower spiral cord slightly above lower suture; shell surface below selenizone lacking collabral ornamentation; diameter of protoconch about 0.25 mm; whorl following protoconch rounded and bearing a keel slightly above midwhorl; selenizone visible approximately from second whorl in the position of the latter’s keel; during shell ontogeny the selenizone changes its position from above midwhorl to its middle (Fig. 3.12); lower spiral cord appearing from about the beginning of second whorl; upper spiral cord developing slightly later; collabral ribs visible from third whorl; spiral angle of the first three whorls higher than that of the whorls forming the teleoconch. Etymology.In honor of Wojciech Krawczyn´ski, our friend and Paleozoic gastropod specialist from Sosnowiec, Poland. Types.Holotype, CˇGU JF 788, Figure 3.6–3.9, 3.12. Occurrence.Balbinipleura krawczynskii n. sp. is known only from its type locality. Discussion.The Emsian Balbinipleura krawczynskii n. sp. differs from the type species, the Pragian Balbinipleura bohemica, in its lack of collabral ribs below the selenizone. In addition, its upper spiral cord is situated closer to the selenizone. The latter

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characters differentiate it also from the Early Carboniferous Balbinipleura koninckii. Balbinipleura? sextalineata has a much wider shell with a protruding selenizone (see Heidelberger, 2001, pl. 3, fig. 3). These characters distinguish the latter species from all known species of Balbinipleura. For these reasons and because of the lack of additional shell characters in Balbinipleura? sextalineata, we consider its genus-level position uncertain. Balbinipleura krawczynskii n. sp. seems to be closest to the Pragian type species, Balbinipleura bohemica, from among all known species of the genus. Family GOSSELETINIDAE Wenz, 1938 Subfamily COELOZONINAE Knight, 1956 Discussion.Knight et al. (1960) placed the subfamily Coelozoninae Knight, 1956 in the family Gosseletinidae Wenz, 1938. They diagnosed the Gosseletinidae as uniting pleurotomarioideans having a ‘‘short labral slit and flat selenizone, generally without bordering threads.’’ Among the two subfamilies placed in the Gosseletinidae, the Coelozoninae unites forms with a ‘‘broad and short slit’’ and the Gosseletininae those with a ‘‘narrow slit and selenizone above mid-whorl’’ (Knight et al., 1960). However, these criteria are difficult to use because there are morphological transitions among members of both subfamilies (i.e., compare the shapes of Euryzone Koken, 1896; Coelozone Perner, 1907; Umbotropis Perner, 1903; and Humboldtiella Blodgett and Fry´da, 1999). The newly described genus, Arctozone, is close to the latter two genera and so we tentatively place it in the Coelozoninae. ARCTOZONE new genus Type species.Arctozone cooki n. sp. from the Emsian (late Early Devonian) of the Nixon Fork subterrane of the Farewell terrane, west-central Alaska. Species included.Only the type species is known. Diagnosis.Small-sized coelozoninid shell with ornament of numerous, fine spiral threads; selenizone broad and flat, inclined at 45 degrees from horizontal, situated at juncture between upper and outer whorl surfaces; selenizone bordered by two fine spiral cords and bearing one spiral cord in its middle (Fig. 4); spiral angle about 110 degrees; shell base widely rounded and phaneromphalous; protoconch relatively small; selenizone starting roughly from second whorl and being situated high on whorl; during subsequent growth selenizone is moving abapically to its peripheral position at more adult whorls. Etymology.The genus name Arctozone is derived from a combination of the Greek words, Arktos (north) and Zone (belt or girdle). Discussion.Among all genera placed in the Gosseletinidae, Arctozone n. gen. most closely resembles the Devonian species of Umbotropis and Humboldtiella. Arctozone n. gen. has an almost identical general shell shape to Umbotropis (compare Fig. 3.1–3.5 with that of Fry´da and Bandel, 1997, pl. 5, figs. 5–7). The latter genus is known only from the Lower Devonian strata of Europe (Perner, 1903; Chlupaćˇ and Vaneˇk, 1957; Fry´da and Bandel, 1997) and Australia (Tassell, 1982). Arctozone n. gen. differs from Umbotropis in having a shell and selenizone ornamented by spiral cords. The ornament of the shell of Arctozone n. gen. resembles that found in the type species of Humboldtiella, Humboldtiella undulata (Roemer, 1843). However, Humboldtiella has a low shell with a nearly flat upper shell surface and with deeply impressed sutures. Similar to Umbotropis, Humboldtiella also lacks a spiral cord in the middle of the selenizone. ARCTOZONE COOKI new species Figures 3.1–3.5, 3.10–3.11, 4 Diagnosis.Because of monotypy, see that of genus. Description.Small, low-spired shell with up to five adult

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FRY´DA AND BLODGETT—DEVONIAN GASTROPODS FROM ALASKA

FIGURE 4—Illustration showing reconstruction of Arctozone cooki n. sp.

whorls; spiral angle about 110 degrees; upper whorl surface very weakly convex; lateral and basal parts of whorl rounded without any angulation; selenizone broad and flat, inclined at 45 degrees from horizontal, situated at juncture between upper and outer whorl surfaces; succeeding whorls joining preceding whorls just below selenizone; selenizone bordered on either side by a fine spiral cord and bears one spiral cord in its middle; lower spiral cord bordering selenizone forms the shell periphery in adult whorls; shell base rounded and broadly phaneromphalous with a deep umbilicus; ornament consists of fine spiral threads which are numerous and closely spaced on both the upper and outer whorl surfaces; selenizone starting roughly from second whorl and situated high on whorl; during subsequent shell growth selenizone moves abapically to its peripheral position in the more adult whorls; diameter of relatively small protoconch about 0.16 mm. Etymology.In honor of Alex G. Cook, our friend and Devonian gastropod specialist, Queensland Museum, Brisbane, Australia. Types.Holotype, CˇGU JF 789, Figure 3.1, 3.3, 3.4, 3.10, 3.11; paratype A, CˇGU JF 790, Figure 3.2, 3.5; paratype B, CˇGU JF 811; paratype C, CˇGU JF 812. Occurrence.Arctozone cooki n. sp. is known only from its type locality. Discussion.Until now there are only two gosseletinid genera with known protoconchs, Euryzone and Umbotropis. The diameter of the protoconch in Arctozone cooki n. sp. is less than half that of Umbotropis rihai Fry´da and Bandel, 1997 (pl. 5, figs. 5– 7) and Euryzone delphinuloides (personal observation, Fry´da). Superfamily MICRODOMATOIDEA Wenz, 1938 Family MICRODOMATIDAE Wenz, 1938 Discussion.Wenz (1938) based his new subfamily Microdominae on the Carboniferous genus Microdoma Meek and Worthen, 1867 and placed it together with the Trochonematinae, Holopeinae, and questionably the Bucanospirinae in the family Trochonematidae. Later Knight et al. (1960) changed this concept

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and raised Wenz’s subfamily to the level of a superfamily, uniting two families, Microdomatidae and Elasmonematidae, within it. Also the generic content of Microdomatidae was changed. Knight et al. (1960) included in the family Microdomatidae the following gastropod genera: the Carboniferous Microdoma, the Ordovician Daidia Wilson, 1951; the Devonian Episfaxis Perner, 1903 and Pagodea Perner, 1903; and the Permian Glyptospira Chronic, 1952. Later, Horny´ (1991) excluded the Devonian genus Episfaxis from the Microdomatidae. On the other hand, during more recent years several additional, mainly Devonian, genera were placed in the latter family. Linsley (1968) added a new genus Copidocatomus from the Anderdon Limestone (Eifelian) of Ontario, Canada, to the Microdomatidae. Blodgett and Johnson (1992) described a new microdomatid genus Decorospira, uniting three species from Eifelian (early Middle Devonian) strata of Alaska and Nevada. Slightly later, Horny´ (1992) established two new microdomatid genera, Dongiovannia and Petrochus, from the Early Devonian of the Prague Basin. The first genus was synonymized by Blodgett and Fry´da (1999) with Decorospira. Horny´ (1992) suggested that the Late Ordovician genus Threavia Lamont, 1946 might belong to the Microdomatidae. In 1993, Blodgett added another microdomatid genus, the Eifelian age Dutrochus Blodgett, 1993, from the Cheeneetnuk Limestone of westcentral Alaska. Later Blodgett and Fry´da (1999) united the Devonian genera Decorospira, Dutrochus, and Roemeriella Blodgett and Fry´da, 1999 within a new subfamily Decorospirinae of the Microdomatidae. Fry´da et al. (2001) added a new Upper Ordovician microdomatid genus, Eopagodea Fry´da and Rohr, 2001, to the Microdomatidae and suggested the necessity of a new revision of the family-level taxonomy of the superfamily Microdomatoidea. The recent discovery of protoconchs and original shell structure in the type species of Microdoma, Microdoma conicum Meek and Worthen, 1867 (Bandel et al., 2002), from the Pennsylvanian Buckhorn Asphalt (Oklahoma, USA), reveals important new data on the higher taxonomic position of the superfamily Microdomatoidea. The shell of Microdoma conicum bears an inner nacreous layer and their shell layers resemble those of modern trochoids (Bandel et al., 2002). This observation together with occurrence of an archaeogastropod-type protoconch in Microdoma indicates placement of the latter genus as well as the Microdomatoidea within the Archaeogastropoda. Subfamilies included.Microdomatinae Wenz, 1938 (Ordovician-Permian) and Decorospirinae Blodgett and Fry´da, 1999 (Devonian). Subfamily DECOROSPIRINAE Blodgett and Fry´da, 1999 Discussion.According to Blodgett and Fry´da (1999), the Decorospirinae unites microdomatid gastropods with a subequally developed ornament of closely spaced, collabral threads that are prosocline on the upper and outer whorl surfaces, and opisthocyrt on the basal whorl surface, intersecting with spiral threads to yield a distinctive reticulate ornament, weakly nodose at the juncture of spiral and collabral elements. This subfamily ranges from Emsian (late Early Devonian) to Frasnian (early Late Devonian). The occurrence of an archaeogastropod-type protoconch in the late

← FIGURE 3—1–5, 10–11, Arctozone cooki n. sp.; 1, 3, 4, 10, 11, holotype, CˇGU JF 789; 1, 3, lateral views, 322; 4, oblique view showing shell ornamentation, 322; 10, apical view, 322; 11, oblique basal view showing shell ornamentation, 317; 2, 5, juvenile shell, paratype A, CˇGU JF 790, 350; 2, lateral view; 5, oblique view showing protoconch morphology. 6–9, 12, Balbinipleura krawczynskii n. sp.; holotype, CˇGU JF 788; 6, apical view showing protoconch morphology, 328; 7–9, lateral views; 7, 328; 8, 328; 9, 332; 12, enlarged view of 8 showing change of selenizone position during early shell ontogeny, 345.

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Emsian Decorospira pragensis (Horny´, 1992) supports the placement of the Decorospirinae within the family Microdomatidae to the Archaeogastropoda (JF). Genera included.Decorospira, Dutrochus, and Roemeriella. Genus DECOROSPIRA Blodgett and Johnson, 1992 DECOROSPIRA LEPAINI new species Figure 5.1–5.4, 5.6 Diagnosis.Decorospira with relatively high whorls; strongly angular whorl surface between sutures consists of three distinct parts, due to the presence of two strong, rounded spiral cords; upper cord being more prominent; whorl surface between lower spiral cord and lower suture wide; shell apex acute; diameter of first preserved whorl about 0.15 mm. Description.Small, high-spired, dextrally coiled, turbiniform shell consisting of at least seven whorls; shell higher than wide and with a spiral angle of about 45 degrees; sutures deeply incised; whorl about two times wider than distance between sutures; whorl profile strongly angular, due to the presence of two strong, rounded spiral cords; upper cord being more prominent; whorl surface between sutures consists of three distinct parts, an upper whorl surface between upper suture and upper spiral cords, middle whorl surface bounded on either side by the upper and lower spiral cords, and a lower whorl surface between the lower spiral cord and the lower suture; upper whorl surface gently convex and declined at about 40 degrees from plane perpendicular to the shell axis; middle whorl surface distinctly concave; upper spiral cord forms whorl periphery; lower whorl surface in more adult whorls bearing additional, weaker spiral cords, roughly in the middle between lower spiral cord and lower suture; distance between lower cord and lower suture approximately equal to that between upper and lower cords; rounded shell base minutely phaneromphalous or anomphalous; ornamentation consisting of numerous, closely spaced collabral threads, which intersect with the spiral cords to produce a prominent reticulate pattern; a weakly pustulose swelling is present at each intersection; collabral threads declined backwards across the middle and lower whorl surfaces at about 70 degrees from the upper suture and continuing on basal shell surface; early shell poorly preserved; diameter of first preserved whorl about 0.15 mm. Etymology.In honor of David L. LePain, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska. Types.Holotype, CˇGU JF 791, Figure 5.1–5.4; paratype A, CˇGU JF 792, Figure 5.6; paratype B, CˇGU JF 810. Occurrence.Known only from its type locality. Discussion.Decorospira lepaini n. sp. differs from the type species of Decorospira, Decorospira tasselli Blodgett and Johnson, 1992, from the early Eifelian of west-central Alaska, in having the whorl surface between sutures divided into three parts. The whorl surface between the lower suture and lower spiral cord is relatively wide in Decorospira lepaini n. sp. (its width is about the same as the distance of the upper and lower spiral cords, Fig. 5.1, 5.3, 5.4) because the lower suture is situated low on the whorl and relatively far from the lower spiral cord. In contrast with Decorospira tasselli the lower suture is situated at or slightly below the lower spiral angulation (see Blodgett and Johnson, 1992, pl. 15, figs. 1–5). The latter shell character differentiates Decorospira lepaini n. sp. from the other two North American Eifelian species, Decorospira gilberti Blodgett and Johnson, 1992 and Decorospira rigbyi Blodgett and Johnson, 1992 (see Blodgett and Johnson, 1992, pl. 15, figs. 6–11). On the other hand, this shell character resembles that of the late Emsian Decorospira pragensis (Horny´, 1992) from the Prague Basin. However, Decorospira lepaini n. sp. can be distinguished from the latter species by the shape of its shell apex and relatively higher whorls. The shell apex in the first species is acute (Fig. 5.4) but is domelike in

Decorospira pragensis. In addition, during shell ontogeny the upper spiral cord is distinctly developed on the whorls of Decorospira lepaini n. sp. having a diameter of about 0.5 mm or more. On the other hand, the first two whorls in Decorospira pragensis are rounded without any angulation and bear only collabral ornamentation. The protoconch size in Decorospira pragensis is much higher than in Decorospira lepaini n. sp. In the latter species the diameter of the first preserved whorl is about 0.15 mm, but in Decorospira pragensis the diameter of the first whorl bearing the protoconch is about 0.6 mm. DECOROSPIRA? MINUTULA new species Figure 5.5 Diagnosis.Small, high-spired Decorospira-like shell with a prominent angulation forming the whorl periphery; collabral threads regularly spaced and prosocline; aperture elliptical and shell base anomphalous; shell apex acute with the diameter of the first whorl about 0.1 mm. Description.Small, high-spired, dextrally coiled, turbiniform shell with a spiral angle of about 40 degrees; whorl profile strongly angular due to the presence of a strong, rounded spiral cord situated centrally between the sutures and forming the whorl periphery; whorl width about double the distance between sutures; sutures weakly incised; upper whorl surface flat or slightly concave and inclined at about 45 degrees from the horizontal; whorl surface below angulation smoothly curved onto anomphalous shell base; elliptical aperture slightly higher than wide; shell ornamentation consisting of regularly spaced, prosocline collabral threads; shell apex acute with the diameter of the first whorl about 0.1 mm. Etymology.The species name refers to its very small shell. Type.Holotype, CˇGU JF 793, Figure 5.5. Occurrence.Known only from its type locality. Discussion.This species is based upon a single, well-preserved specimen which resembles in some shell characters (acute shell apex with a very small first whorl; shape of the first three whorls; regularly spaced, prosocline collabral threads) the coeval Decorospira lepaini n. sp. However, Decorospira? minutula n. sp. can be distinguished from the latter species by the differing whorl profile of the more adult whorls. Two distinct spiral cords that divide the whorl surface into three distinct parts are present in Decorospira lepaini n. sp. starting from its fourth whorl (Fig. 5.5). On the other hand, only a single spiral cord forming the whorl periphery is present in Decorospira? minutula n. sp. The whorl profile of the latter species resembles the Eifelian species of Decorospira, especially Decorospira gilberti. In addition to the absence of the lower spiral cord in Decorospira? minutula n. sp., the latter species differs from the coeval Decorospira lepaini n. sp. in having a narrower shell and weaker spiral cord centrally situated between the sutures, i.e., lower than the upper spiral cord in Decorospira lepaini n. sp. Comparison of Decorospira? minutula n. sp. with Eifelian species of Decorospira that have a similar whorl profile is more difficult because their early whorls are poorly known. Nevertheless, the Eifelian species may be distinguished from the Decorospira? minutula n. sp. by their wider spire. Decorospira? minutula n. sp. is questionably placed in the genus Decorospira because of the presence of only a single spiral cord and its relatively narrow shell. Superfamily PORCELLIOIDEA Koken, 1895 Discussion.Bandel (1993) expressed the opinion that members of the Paleozoic family Porcelliidae evolved during the Triassic into members of the Mesozoic Cirridae. For this reason, Bandel (1993) united both the families in the superfamily Cirroidea. This systematic approach was followed by several authors


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FIGURE 5—1–4, 6, Decorospira lepaini n. sp.; 1–4, holotype, CˇGU JF 791; 1, lateral view, 321; 2, oblique apical view, 328; 3, oblique lateral view, 328; 4, lateral view, 326; 6, oblique lateral view of paratype A, CˇGU JF 792, 328. 5, Decorospira? minutula n. sp.; apertural view of holotype, CˇGU JF 793, 340.

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FIGURE 6—1, 2, 4, 6, Alaskiella medfraensis; holotype, CˇGU JF 565; 1, oblique view of the sinistrally coiled teleoconch with a deeply concave apical depression formed by the umbilicus of the dextrally coiled initial portion of the shell, 323; 2, apertural view, 325; 4, lateral view of abapertural side showing inclined heterostrophic coiling, 323; 6, detailed view showing the lateral side of the youngest whorl visible in the ‘‘sutural window’’ between the last dextral and the first sinistral whorls, 350. 3, 5, Alaskacirrus bandeli; 3, paratype B, CˇGU JF 576, apertural view, 330; 5, holotype, CˇGU JF 574, oblique view showing heterostrophic coiling, 350.

(Fry´da, 1997, 1999a; Fry´da and Blodgett, 1998; Blodgett and Fry´da, 1999; Heidelberger, 2001). Recently, Phillipe Bouchet (Paris) advised us (personal commun.) that Koken (in Zittel, 1895) has to be considered as the author of the family Porcelliidae, rather than Broili (1924) as has been stated by Knight et al. (1960). Due to this fact the Porcelliidae have to be regarded as an older family predating the Cirridae Cossmann, 1916. Because the rules of zoological nomenclature indicate that the name of the superfamily has to be derived from the oldest family name, the superfamily name Cirroidea must be replaced by the Porcellioidea. Family PORCELLIIDAE Koken, 1895 Subfamily AGNESIINAE Knight, 1956 Genus ALASKIELLA Fry´da and Blodgett, 1998 ALASKIELLA MEDFRAENSIS Fry´da and Blodgett, 1998 Figure 6.1–6.2, 6.4, 6.6 Discussion.Shells of the Agnesiinae exhibit an unusual changing in the coiling of their shells from dextral to sinistral (sinistral heterostrophy). Similar to all Porcellioidea, the shell axes of the dextrally coiled early shell and teleoconch are parallel (anastrophy). The only exception to this is the Emsian Alaskiella

medfraensis, which is the only previously known archaeogastropod exhibiting inclined heterostrophy (Fry´da and Blodgett, 2001a). Shell heterostrophy (anastrophic as well as inclined heterostrophic coiling) has been considered an apomorphy of the Heterobranchia, and it occurs in all members of the Heterobranchia where planktotrophic larvae are developed. However, as shown by Fry´da and Blodgett (2001a), heterostrophy in the Heterobranchia and Archaeogastropoda (Porcellioidea) is not homologous. In members of the Heterobranchia, the timing of the change of the coiling manner (from sinistral to dextral or vice versa) is always connected with the ontogenetic stage when the true larval shell (protoconch II) terminates and the teleoconch starts to form. In contrast to the Heterobranchia, the change of coiling manner in the Porcellioidea occurs during early teleoconch ontogeny. In addition, the Porcellioidea, like all members of the Archaeogastropoda, never develop a true larval shell (protoconch II) and formation of their teleoconch starts just after the completion of the embryonic shell (protoconch I). Thus, Alaskiella medfraensis Fry´da and Blodgett, 1998 represents an excellent example of parallel evolution among gastropod shells (i.e., origin of inclined heterostrophy).

FRY´DA AND BLODGETT—DEVONIAN GASTROPODS FROM ALASKA Family ?CIRRIDAE Cossmann, 1916 Genus ALASKACIRRUS Fry´da and Blodgett, 1998 ALASKACIRRUS BANDELI Fry´da and Blodgett, 1998 Figure 6.3, 6.5 Discussion.As shown by Fry´da and Blodgett (1998), the shell characters of Alaskacirrus fit well with the diagnosis of the family Cirridae Cossmann, 1916, as emended by Bandel (1993). For these reasons, they placed their new genus in this family and suggested that the family Cirridae was separated from the family Porcelliidae since at least Early Devonian time. On the other hand, Fry´da and Blodgett (1998) pointed out that the unusual shell of Alaskacirrus does not fit well with the diagnoses of any of the subfamilies uniting the Mesozoic genera of the Cirridae. Recently several new Devonian porcellioidean gastropods without selenizone were recognized. Among the modern archaeogastropods there are large taxa uniting forms with shells having or lacking a selenizone like the modern members of the Seguenzioidea or Scissurelloidea (Marshall, 1983; Bandel, 1998). Fossil slit-bearing gastropods also have probably lost this shell feature several times in different lineages (Bandel and Fry´da, 1996). Recently, such a loss of the selenizone was documented within the Devonian family Scoliostomatidae Fry´da, Blodgett, and Lenz, 2002 (Fry´da et al., 2002). Because the majority of the middle and late Paleozoic porcellioideans have not been revised or remain undescribed it is impossible to determine whether the Devonian porcellioideans without a selenizone represent a natural group or if the loss of a selenizone happened independently in several porcellioidean branches. Thus, the family-level position of Alaskacirrus bandeli needs to be re-evaluated in the future on the basis of new data concerning Paleozoic Porcellioidea. Superfamily MURCHISONIOIDEA Koken, 1896 Family MURCHISONIIDAE Koken, 1896 Discussion.Knight et al. (1960) placed the family Murchisoniidae Koken, 1896 together with the family Plethospiridae Wenz, 1938 into the superfamily Murchisonioidea Koken, 1896, of the suborder Murchisoniina Cox and Knight, 1960. The latter suborder was considered by Knight et al. (1960, p. 290) to be ‘‘a stock derived from the Archaeogastropoda and still retaining certain features of that order, but showing advances in some characters along lines of evolution that led to Caenogastropoda.’’ Thus, the murchisoniids have been considered to represent transitional forms between the Archaeogastropoda and the Caenogastropoda. In this context, recent studies of protoconch morphology in the Devonian and Carboniferous murchisoniids have revealed important new data for the evaluation of the latter hypothesis. Fry´da and Manda (1997) found that several Lochkovian, Pragian, Emsian, and Eifelian age (Devonian) species of Murchisonia d’Archiac and deVerneuil, 1841, and other closely related genera have an archaeogastropod-type protoconch consisting only of an embryonic shell (protoconch I). These gastropods were interpreted as members of the Archaeogastropoda (Fry´da, 1999a). Unfortunately, Givetian (late Middle Devonian) murchisoniids including also the type species of Murchisonia, M. bilineata (Dechen, 1832) have provided no well-preserved protoconchs. Nevertheless, the teleoconch shape of some of Givetian (late Middle Devonian) murchisoniids is very similar to those with the archaeogastropod-type protoconchs (e.g., Blodgett et al., 1999). However, Murchisonia underwent an explosive radiation of elaborate and bizarre shapes and ornament during the Middle Devonian (see Andree, 1928; Paeckelmann, 1922; Heidelberger, 2001). This complex plexus is not well studied and probably involved members of other families as shown by Blodgett and Cook (2002). In addition, Nu¨tzel and Bandel (2000) described late Paleozoic slitbearing gastropod genera resembling the murchisoniids, but developing a true larval shell (protoconch II) and, thus, belonging

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to the Caenogastropoda. For these reasons, we consider the higher systematic position of the superfamily Murchisonioidae to be uncertain. FAREWELLIA new genus Type species.Farewellia heidelbergerae n. sp. from the Emsian (late Early Devonian) strata of the Medfra quadrangle, westcentral Alaska. Diagnosis.High-spired murchisoniid with selenizone close to upper suture; rounded whorls ornamented below selenizone by regularly spaced, opisthocline threads; flat whorl surface above selenizone bearing only prosocline growth lines. Etymology.After the accreted Farewell terrane of southwestern and west-central Alaska, from which this gastropod was obtained. Discussion.Among murchisoniid genera, Farewellia n. gen. most closely approaches the genus Hormotoma Salter, 1859, in that both genera have a similar whorl shape bearing a deep sinus generating a narrow selenizone. However, the new genus differs in having a much narrower shell and a selenizone that is situated much closer to the upper suture. In addition, the shell of the Early Devonian Farewellia n. gen. is ornamented by regularly spaced, opisthocline threads below the selenizone (Fig. 7.3, 7.4). The very high position of the selenizone in Farewellia heidelbergerae n. sp. is an unusual shell feature that distinguishes it from all other murchisoniid genera. Only the Silurian Leptorima Perner, 1907, based on Murchisonia oehlerti Perner, 1903, also has a very high selenizone. Farewellia n. gen. differs from it in having a slender, high-spired shell, while Leptorima has a turbiniform shell. The protoconch in Farewellia heidelbergerae n. sp. is unknown, so its higher systematic position is uncertain. However, because its general shell shape resembles those found in other Silurian and Devonian murchisoniids, we tentatively place it here. FAREWELLIA HEIDELBERGERAE new species Figure 7.1–7.5, 7.8 Diagnosis.Because of monotypy, see that of genus. Description.Small, very high-spired shell with rounded whorls; spiral angle about 12 degrees; narrow selenizone situated close to upper suture; selenizone flat, inclined at about 45 degrees from horizontal; width of selenizone about one-sixth of distance between sutures; whorl profile about selenizone flat or slightly concave; whorls below selenizone strongly and evenly rounded; sutures deep; shell base rounded and anomphalous; flat whorl surface above selenizone bearing only prosocline growth lines; whorl surface below selenizone ornamented by regularly spaced, opisthocline threads; shell base smooth (Fig. 7.3, 7.4); initial part of shell unknown. Etymology.In honor of Doris Heidelberger, our friend and Paleozoic gastropod specialist, Oberursel, Germany. Types.Holotype, CˇGU JF 794, Figure 7.1, 7.2, 7.5; paratype A, CˇGU JF 795, Figure 7.3, 7.4; paratype B, CˇGU JF 808; paratype C, CˇGU JF 809. Occurrence.Farewellia heidelbergerae n. sp. is known only from its type locality on the south flank of Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska. Subclass UNCERTAIN Superfamily LOXONEMATOIDEA Koken, 1889 Discussion.Loxonematoidea Koken, 1889 are a very common group of Paleozoic gastropods and their higher taxonomic position was recently discussed by several authors (Bandel, 1991; Nu¨tzel, 1997; Fry´da and Bandel, 1997; Fry´da, 1999a, 1999b). The different protoconch morphologies found in the middle and late Paleozoic loxonematoideans indicates that this superfamily (sensu

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FIGURE 7—Farewellia heidelbergerae n. sp.; 1, 2, 5, holotype, CˇGU JF 794, lateral views, 313, 312, 312, respectively; 3, 4, paratype A, CˇGU JF 795; 3, lateral view showing shell ornamentation, 322; 4, oblique basal view showing smooth shell base, 322.

Wenz, 1938 and Knight et al., 1960) is a polyphyletic group uniting members of Caenogastropoda, Heterobranchia, and Archaeogastropoda (Bandel, 1991; Nu¨tzel, 1997; Fry´da and Bandel, 1997; Fry´da, 1999a, 2000). Fry´da and Bandel (1997) reported large protoconchs (with the diameter of the first whorl ranging from 0.3 to 0.5 mm) in some Early Devonian members of the families Loxonematidae (Katoptychia Perner, 1907 and Stylonema Perner, 1907) and Palaeozygopleuridae (Palaeozygopleura). These protoconchs have less than one whorl and were interpreted as a nonplanktotrophic protoconch I consisting only of an embryonic shell. The absence of a true larval shell (protoconch II) and the presence of a large embryonic shell in these gastropods were compared with the type of shell development found in the Archaeogastropoda. For this reason these gastropods with very slender, high-spired shells were united in the new group Stylogastropoda (Fry´da and Bandel, 1997). Nu¨tzel (1997) also interpreted the large protoconchs of the Devonian Palaeozygopleuridae as being clearly nonplanktotrophic, but the higher taxonomic position of that family was considered to be uncertain. Nu¨tzel (1997) also suggested that the nonplanktotrophic nature of the Palaeozygopleuridae may be the result by their living in a deeper-water environment. Fry´da (1999b) described an additional Early Devonian species, Pragozyga costata Fry´da, 1999b, with a large protoconch formed only by the first half of the whorl (Fry´da, 1999b, fig. 3D, 3E). Even though our knowledge of the protoconch morphologies found in pre-Carboniferous loxonematoideans is limited, it is very unusual that all known Devonian loxonematoideans with wellpreserved early shells (i.e., Loxonematidae and Palaeozygopleuridae) have large lecithotrophic protoconchs. This fact cannot be easily explained by their living in deeper-water environments as

Nu¨tzel (1997) suggested. Fry´da (1999b) noted that these gastropods were found in different limestone facies deposited in variable depths including the shallow-water reefal environment. Only new detailed studies of the Devonian loxonematoideans with well-preserved protoconchs may help to solve question of whether they are Archaeogastropoda with an unusual teleoconch shape, Caenogastropoda with unusually large, nonplanktotrophic larval shells, or something different. Family PALAEOZYGOPLEURIDAE Horny´, 1955 (emended by Knight, Batten, Yochelson, and Cox, 1960) Discussion.The opinions on the generic composition of the family Palaeozygopleuridae and its relationship to Pseudozygopleuridae Knight, 1930 and Loxonematidae Koken, 1889 have changed several times (Hoare and Sturgeon, 1980; Hoare, 1980; Fry´da, 1993; Nu¨tzel, 1997). According to Licharev (1970), the differences in the type of protoconch ornamentation of the Palaeozygopleuridae and Pseudozygopleuridae do not have higher taxonomic significance. For this reason he proposed the placement of the family Palaeozygopleuridae into the family Pseudozygopleuridae as a junior synonym. On the other hand, Hoare and Sturgeon (1978) expressed the opinion that the Pseudozygopleuridae illustrate a remarkable consistency in the nature of the protoconch, which readily differentiates it from other families of Loxonematoidea. This approach was also supported by new data on Early Devonian members of the Loxonematidae and Palaeozygopleuridae (Fry´da and Bandel, 1997; Fry´da, 1999a). Fry´da (1993) noted that neither of the teleoconch characters, which had previously been used in the differentiation of the families Loxonematidae and Palaeozygopleuridae, could be used for a reliable


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Subgenus PALAEOZYGOPLEURA (RHENOZYGA) Fry´da, 2000 Type species.Loxonema retrostriatum Kirchner, 1915, from the Middle Devonian of Germany. Included species.Species of Palaeozygopleura (Rhenozyga) are known from the Givetian (late Middle Devonian) of Germany [the type species, Palaeozygopleura (Rhenozyga) retrostriatum (Kirchner, 1915) as well as several other species which need revision] from the Frasnian (early Late Devonian) of Poland (Krawczyn´ski, 2002) and Middle Devonian of Australia (Fry´da, 2000; Palaeozygopleura (Rhenozyga) machenryi Cook, 1997). The latter species is known from the Burkedin Limestone of late Eifelian to early Givetian age (Talent et al., 2002). Palaeozygopleura (Rhenozyga) reifenstuhli n. sp. represents the first record of this subgenus from North America and is also its oldest known species. Diagnosis.Subgenus of Palaeozygopleura with orthocline or slightly opisthocyrt collabral costae; whorl between sutures strongly arched; shell cyrtoconoid or with straight sides.

FIGURE 8—Illustration showing reconstruction of Farewellia heidelbergerae n. sp.

distinction between these two families. Also protoconch morphology in the both Loxonematidae and Palaeozygopleuridae (Fry´da and Bandel, 1997; Fry´da, 1999a, 1999b) cannot be used for their differentiation. Thus, a new evaluation of all available shell characters is needed together with new material for a solution of the family level taxonomy of the middle and early Paleozoic loxonematoideans. Genus PALAEOZYGOPLEURA Horny´, 1955 Type species.Zygopleura alinae Perner, 1907, from the Praha Formation (Pragian, Early Devonian) of the Prague basin. Discussion.The gastropod genus Palaeozygopleura was established for a relatively diversified group from Early Devonian strata of the Prague Basin. Later, a number of the Devonian and Carboniferous gastropods from Europe (Horny´, 1955; Batten, 1966), Asia (Likharev, 1968, 1970), Australia (Tassell, 1982; Cook, 1997; Cook and Camilleri, 1997), and North America (Linsley, 1968, Rollins et al., 1971; Thein and Nitecki, 1974; Gordon and Yochelson, 1987; Blodgett et al., 1988) were placed in this genus. Unfortunately, no data exists concerning the protoconch morphology in the majority of these species. Some of them (the Carboniferous species) probably belong to the genus Pseudozygopleura (family Pseudozygopleuridae). This fact complicates the usage of subgeneric categories established within the genus Palaeozygopleura [i.e., P. (Palaeozygopleura) Horny´, 1955; P. (Palaeozyga) Horny´, 1955; P. (Bojozyga) Horny´, 1955; P. (Bohemozyga) Fry´da and Bandel, 1997; P. (Rhenozyga) Fry´da, 2000]. The Devonian representatives of Palaeozygopleura are known from Europe (Horny´, 1955; Karczewski, 1980; Fry´da 1993, 2000; Fry´da and Bandel, 1997; Heidelberger, 2001; Krawczyn´ski, 2002); Central Asia (Vostokova, 1966), Australia (Tassell, 1982; Cook, 1997; Cook and Camilleri, 1997), Alaska (Blodgett et al., 1988), eastern North America (Linsley, 1968; Rollins et al., 1971) and Iran (Fry´da, personal observation); thus, they show an Old World Realm and Eastern Americas Realm distribution.

PALAEOZYGOPLEURA (RHENOZYGA) REIFENSTUHLI new species Figure 9.4, 9.5, 9.7–9.9 Diagnosis.Small species of Palaeozygopleura (Rhenozyga) with fine ornamentation; diameter of first whorl slightly less than 0.3 mm. Description.Small gastropod with a high-spired, dextrally coiled shell consisting of at least six whorls; shell sides slightly convex; lateral sides of whorls strongly arched; sutures deep; spiral angle about 20 degrees; lateral sides of whorls curves uniformly onto the basal part without any edge; shell base rounded and anomphalous; aperture circular; shell ornament consists of prominent, orthocline, collabral costae; diameter of first whorl slightly less than 0.3 mm (Fig. 9.7); position of boundary between protoconch and teleoconch unknown. Etymology.In honor of Rocky R. Reifenstuhl, Alaska Division of Geological and Geophysical Surveys, Fairbanks, Alaska. Types.Holotype, CˇGU JF 796, Figure 9.4, 9.5; paratype A, CˇGU JF 797, Figure 9.7, 9.8; paratype B, CˇGU JF 798, Figure 9.9; paratype C, CˇGU JF 806; paratype D, CˇGU JF 807. Occurrence.Known only from its type locality. Discussion.Palaeozygopleura (Rhenozyga) reifenstuhli n. sp. differs from the type species, Palaeozygopleura (Rhenozyga) retrostriatum, by its much finer shell ornamentation. The number of collabral costae in Palaeozygopleura (Rhenozyga) reifenstuhli n. sp. varies from 40 to 50 per whorl revolution in whorls having a width of about 1 mm, which is about double that found in the type species. The latter character distinguishes Palaeozygopleura (Rhenozyga) reifenstuhli n. sp. from Palaeozygopleura (Rhenozyga) machenryi, and Late Devonian (Frasnian) species of Palaeozygopleura (Rhenozyga) figured by Krawczyn´ski (2002). The Emsian Palaeozygopleura (Rhenozyga) reifenstuhli n. sp. represents the first Early Devonian member of the subgenus, thus, increasing its stratigraphic range now from the Emsian (late Early Devonian) to the Frasnian (early Late Devonian). MEDFRAZYGA new genus Type species.Medfrazyga clauticae n. sp. from the Emsian (late Early Devonian) of the Nixon Fork subterrane of the Farewell terrane, west-central Alaska. Diagnosis.Slender, high-spired and multiwhorled palaeozygopleurid shell with high and narrow whorls and deep sutures; whorl profile strongly convex; sutural slope angle high; outer apertural lip strongly and asymmetrically opisthocyrt (Figs. 9.1–9.3, 10); shell base anomphalous and smooth; aperture circular; shell ornament consists of prominent, regularly spaced, asymmetrically opisthocyrt costae; costae disappearing slightly below the lower suture; large nonplanktotrophic protoconch.

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FIGURE 9—1–3, 6, 10, Medfrazyga clauticae n. sp.; 1–3, 6, holotype, CˇGU JF 799; 1, 2, apertural and lateral views, 322; 3, apertural view, 328; 6, oblique apical view showing large protoconch, 340; 10, paratype A, CˇGU JF 800, lateral view showing shell ornamentation, 316. 4, 5, 7–9, Palaeozygopleura (Rhenozyga) reifenstuhli n. sp.; 4, 5, holotype, CˇGU JF 796, apertural and abapertural views, 330; 7, 8, paratype A, CˇGU JF 797; 7, apical view showing large protoconch, 360; 8, detailed view of apical part of shell, 380; 9, paratype B, CˇGU JF 798, lateral view, 330.


FIGURE 10—Illustration showing reconstruction of Medfrazyga clauticae n. sp.

Etymology.After the Medfra quadrangle, west-central Alaska, where it was discovered. Discussion.Medfrazyga n. gen. resembles species of Palaeozygopleura (the type genus of the family Palaeozygopleuridae) in their collabral ornamentation, but may be distinguished from its various subgenera by its higher whorls bearing asymmetrically, strongly opisthocyrt costae. In addition Medfrazyga n. gen. differs from the P. (Palaeozygopleura), based on the Pragian (middle Early Devonian) Zygopleura alinae Perner, 1907, in having much higher whorls. In contrast to the first genus, P. (Palaeozygopleura) is ornamented by slightly arched, opisthocline costae (see Fry´da and Bandel, 1997, pl. 7, figs. 5, 6). The same shell features differentiate Medfrazyga n. gen. from P. (Palaeozyga) Horny´, 1955, which is based on the early Eifelian (early Middle Devonian) Palaeozygopleura (Palaeozyga) bohemica (see Fry´da and Bandel, 1997, pl. 8, figs. 1–6). Species of the subgenus P. (Bojozyga) Horny´, 1955 also have a slender shell like that of Medfrazyga n. gen., but the latter genus can be distinguished by its much more convex whorls (see Horny´, 1955, pl. 3, figs. 5, 6, pl. 3). Palaeozygopleura (Bohemozyga) Fry´da and Bandel, 1997 differs from Medfrazyga n. gen. in having fine, strongly opisthocline costae, and in having only slightly convex lateral whorl sides and very large protruding protoconch (see Fry´da and Bandel, 1997, pl. 9, figs. 5–7). In contrast to Medfrazyga n. gen., species of P. (Rhenozyga) are ornamented with orthocline or slightly opisthocyrt collabral costae. The strongly convex whorls in Medfrazyga n. gen. resemble those found in the genus Pragozyga Fry´da, 1999b, which is based on Pragozyga costata. However, the latter genus differs from Medfrazyga in having much lower whorls, and widely spaced, orthocline threads (see Fry´da, 1999b, fig. 3A–E). The Givetian (late Middle Devonian) Nodoloxonema Blodgett,

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Fry´da, and Racheboeuf, 1999, based on Nodoloxonema plusquelleci Blodgett, Fry´da, and Racheboeuf, 1999, resembles Medfrazyga in its possession of an apertural sinus, but differs in having a single spiral row of nodes situated at about midwhorl height (see Blodgett et al., 1999, fig. 7.6, 7.7). A deep, asymmetrical sinus in the outer apertural lip has been considered to be a primitive shell character and is found in the early loxonematoidean gastropods such as the Silurian genus Loxonema Phillips, 1841. The deep, asymmetrical sinus gradually disappears during their later phylogeny (see discussion in Horny´, 1955; Knight et al., 1960; and Fry´da, 1993). The shells of later loxonematids often bear a shallow, symmetrical sinus or an opisthocline outer apertural lip. The same morphological trend is found in the family Palaeozygopleuridae (see discussion in Horny´, 1955 and Fry´da, 1993). The apertural sinus in Medfrazyga clauticae n. sp. resembles that present in the oldest known species of Palaeozygopleura, the early Lochkovian (lowermost Devonian) Palaeozygopleura chlupaci Fry´da, 1993 (see Fry´da, 1993, fig. 2). However, the former species has a deep suture and a much deeper apertural sinus (Fig. 9.1–9.3, 9.10). On the other hand, the whorls in Palaeozygopleura chlupaci are slightly adpressed onto the preceding whorls; thus, the whorl profile is moderately concave closely below the upper suture. Nevertheless, the occurrence of a deep apertural sinus in the genus Medfrazyga and in the oldest Paleozygopleura suggests possible phylogenetic relationships. The large size protoconch in Medfrazyga clauticae n. sp. (diameter of first whorl is about 0.35 mm; Fig. 9.6) resembles that in known members of the Devonian Loxonematoidea. This fact also supports the placement of Medfrazyga n. gen. into this group. MEDFRAZYGA CLAUTICAE new species Figures 9.1–9.3, 9.6, 9.10, 10 Diagnosis.Because of monotypy, see that of genus. Description.Medium-sized palaeozygopleurid with slender, high-spired, dextrally coiled shell, having up to 11 whorls; sides of shell approximately straight; spire angle about 15 degrees; whorl profile strongly and symmetrically convex; whorls high and narrow; deep sutures; sutural slope angle high, about 20 degrees; lateral part of whorl curving uniformly onto shell base, forming a smooth curvature without any edge; shell base anomphalous and smooth; outer apertural lip strongly and asymmetrically opisthocyrt; aperture circular; shell ornament consists of prominent, regularly spaced, asymmetrically opisthocyrt costae; beginning at the upper suture, the costae initially are inclined in a prosocline direction and gradually curve in an orthocline direction, and finally end in an opisthocline direction to form a wide, asymmetrical arched sinus; sinus culminates slightly above the middle of the whorl; costae disappearing slightly below the lower suture; angle between costae and the upper suture is about 35 degrees, the angle between the costae and the lower suture is about 50 degrees; large nonplanktotrophic protoconch; diameter of first whorl about 0.35 mm; position of boundary between protoconch and teleoconch unknown. Etymology.In honor of Karen H. Clautice, Alaska Division of Geological and Geophysical Surveys, Fairbanks, Alaska. Types.Holotype, CˇGU JF 799, Figure 9.1–9.3, 9.6; paratype A, CˇGU JF 800, Figure 9.10; paratype B, CˇGU JF 804; paratype C, CˇGU JF 805. Occurrence.Medfrazyga clauticae n. sp. is known only from its type locality on the south flank of Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska. Subclass CAENOGASTROPODA Cox, 1960 Superfamily SUBULITOIDEA Lindstro¨m, 1884 Discussion.Paleozoic gastropods traditionally placed in the superfamily Subulitoidea Lindstro¨m, 1884 represent a highly variable group known from Ordovician to Permian time. However,

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the higher taxonomic position of the superfamily remains enigmatic. The type species of Subulites, representing the type genus of the family Subulitidae, is based on the Middle Ordovician Subulites subelongatus (Orbigny, 1850), which has a large, slender, spindle-shaped, smooth shell, but for which nothing is known regarding its protoconch morphology. The gastropod genera placed in the Subulitoidea are morphologically convergent due to the lack of teleoconch characters. On the other hand, studies of protoconch morphologies in presumed subulitoidean genera have revealed that the middle (Fry´da and Bandel, 1997; Fry´da and Manda, 1997; Fry´da, 1999c, 2001) and late Paleozoic (Nu¨tzel et al., 2000; Nu¨tzel and Cook, 2002; Bandel, 2002a) ‘‘subulitoideans’’ developed a true larval shell. However, among these middle and late Paleozoic ‘‘subulitoideans’’ there are several different protoconch types. Because of the lack of any information concerning the protoconch morphology of Subulites subelongatus, the higher taxonomic position of Subulites as well as of all early Paleozoic subulitoideans is uncertain. The development of orthostrophically coiled larval shells (protoconch II) in middle and late Paleozoic ‘‘subulitoideans’’ has revealed that at least these gastropods belong to the subclass Caenogastropoda Cox, 1960. Representatives of the subfamily Prokopiconchinae Fry´da, 2001 (Soleniscidae Knight, 1931), like the Emsian (late Early Devonian) Balbiniconcha cerinka Fry´da, 2001, are the oldest hitherto known members of the Caenogastropoda (Fry´da, 2001). A caenogastropod-type protoconch morphology was also well documented in the late Paleozoic Soleniscidae Knight, 1931 and Meekospiridae Knight, 1956 (Nu¨tzel et al., 2000). On the other hand, some Devonian gastropod genera (i.e., Chuchlina Fry´da and Manda, 1997; Zenospira Fry´da and Bandel, 1997; and Havlicekiela Fry´da, 1999c), which closely resemble subulitoidean gastropods in their teleoconch morphology, develop true larval shells with an openly coiled first whorl (Fry´da and Bandel, 1997; Fry´da and Manda, 1997). The latter gastropod genera were placed in the family Chuchlinidae Fry´da and Bandel, 1997 (belonging to the Peruneloidea Fry´da and Bandel, 1997). An openly coiled first whorl of the larval shell was also documented in the Carboniferous genera Imogloba Nu¨tzel, Erwin, and Mapes, 2000 and Chlorozyga Nu¨tzel and Cook, 2002. The latter two genera closely resemble members of the Chuchlinidae, but have a distinctively ornamented larval shell and are placed in the family Imoglobidae Nu¨tzel, Erwin, and Mapes, 2000, of the Peruneloidea (Nu¨tzel et al., 2000; Nu¨tzel and Cook, 2002). Larval shells characteristic of the Peruneloidea are relatively common in the Ordovician and Silurian strata and their relative abundance decreases in the Devonian (Fry´da and Rohr, in press). The youngest members are known from the Carboniferous. According to Fry´da (1998b, 1999a, 2001) the Peruneloidea have a long stratigraphic range and may be considered to be an independent gastropod group at the ordinal level (Perunelomorpha), which represents the ancestral group (or basal group) of the Caenogastropoda or even of the whole Apogastropoda. However, the relationship of the Ordovician-Carboniferous Peruneloidea and the middle and late Paleozoic ‘‘subulitoideans’’ (Soleniscidae and Meekospiridae) to the early Paleozoic Subulitoidea is still uncertain. Genus NANOCHILINA Fry´da, 1998c Type species.Nanochilina holynensis Fry´da, 1998c, from the uppermost part of the Trˇebotov Limestone (Daleje-Trˇebotov Formation, late Emsian, late Early Devonian) of the Prague basin. Other species included.Nanochilina gubanovi n. sp. (Emsian) and several undescribed species from the Early Devonian of Europe and eastern Australia. Discussion.The genus Nanochilina was placed by Fry´da (1998c) into the Subulitidae because of its teleoconch features.

Recent discoveries of protoconch morphology in some middle and late Paleozoic ‘‘subulitoideans’’ (Fry´da and Bandel, 1997; Fry´da and Manda, 1997; Nu¨tzel et al., 2000; Fry´da, 2001; and Nu¨tzel and Cook, 2002), as well as the excellent preservation of Nanochilina gubanovi n. sp., enables a new evaluation of its family level position. Nanochilina gubanovi n. sp. has orthostrophic early whorls with an elevated spire and the diameter of the first preserved whorl is about 0.1 mm. In these features Nanochilina resembles some members of the Soleniscidae. Within the latter family, Nanochilina could be placed into the subfamily Prokopiconchinae Fry´da, 2001 because of the distinct collabral ornamentation of its teleoconch. However, Nanochilina in some of its teleoconch features (general shell shape and ornamentation) resembles some peruneloidean species (compare species of Nanochilina with Chlorozyga decussata (Yoo, 1988) and Chuchlina minuta Fry´da and Manda, 1997). Similarly, Chlorozyga (belonging to the family Imoglobidae of the Peruneloidea) closely resembles Balbiniconcha (subfamily Prokopiconchinae of family Soleniscidae) in its teleoconch features, but differs by the type of protoconch ornamentation and the shape of the first protoconch whorl (see Fry´da, 2001 and Nu¨tzel and Cook, 2002). Unfortunately, the shape of the first whorl in Nanochilina is still unknown and so we leave its family-level position open. NANOCHILINA GUBANOVI new species Figure 11.2–11.7 Diagnosis.Small species of Nanochilina with finer and more opisthocline ribs than the type species. Description.Small dextrally coiled, subulate shell; whorls between sutures moderately and symmetrically arched; whorls of teleoconch strongly adpressed, outer lip straight, opisthocline, without slit or sinus; shell base slightly convex; aperture oval with maximum diameter subparallel to shell axis; columellar lip of aperture smooth with no callus or lamella; shell ornamentation consisting of regularly spaced, opisthocline, collabral ribs; early whorls orthostrophic with elevated spire; diameter of the first preserved whorl about 0.1 mm. Etymology.In honor of Alexander Gubanov, our friend and Paleozoic gastropod specialist, Uppsala, Sweden. Types.Holotype, CˇGU JF 801, Figure 11.2–117; paratype A, CˇGU JF 802; paratype B, CˇGU JF 803. Occurrence.Nanochilina gubanovi n. sp. is known only from its type locality on the south flank of Limestone Mountain, westcentral Alaska. This is the first occurrence of this genus in North America. Discussion.Nanochilina gubanovi n. sp. differs from the type species, Nanochilina holynensis, in its finer and more opisthocline ribs. The ribs of the type species in lateral view are opisthocline and roughly parallel with the shell axis (Fig. 11.1), but the ribs are distinctly more opisthocline in Nanochilina gubanovi n. sp. (Fig. 11.2–11.4). In addition, Nanochilina gubanovi n. sp. has more collabral ribs on whorls of the same width than does Nanochilina holynensis. Subclass HETEROBRANCHIA Gray, 1840 Order UNCERTAIN Family KUSKOKWIMIIDAE Fry´da and Blodgett, 2001a Genus KUSKOKWIMIA Fry´da and Blodgett, 2001a Type species.Kuskokwimia moorei Fry´da and Blodgett, 2001a, from the Emsian (late Early Devonian) of west-central Alaska. KUSKOKWIMIA

MOOREI Fry ´ da and Blodgett, 2001a Figures 12.1–12.6, 13 Description.See Fry´da and Blodgett (2001a, p. 42–43). Discussion.As mentioned by Fry´da and Blodgett (2001a) the


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FIGURE 11—1, Nanochilina holynensis; 1, lateral view of holotype, CˇGU JF 720, 318. 2–7, Nanochilina gubanovi n. sp.; holotype, CˇGU JF 801; 2–4, lateral, oblique abapertural, and apertural views, 328, 322, 3, respectively, 19; 5, 6, oblique apical and apical views showing shell ornamentation, 335, 333, respectively; 7, lateral view showing a smooth shell base, 326.

discovery of Kuskokwimia moorei Fry´da and Blodgett, 2001a in Emsian (late Early Devonian) strata was somewhat unexpected. The shell of the type species is small and ovoid with a rapidly expanded dextral spire (Fig. 12.2–12.4) and an anastrophic, sinistrally coiled protoconch. Such a teleoconch type was not known among Paleozoic Heterobranchia, even though it may be found among post-Paleozoic heterobranch gastropods such as the Acteonoidea. Subsequently, Bandel and Heidelberger (2002) reported the discovery of an additional Devonian heterobranch gastropod, Palaeocarboninia jankei Bandel and Heidelberger, 2002, from the Givetian (late Middle Devonian) of Germany. The latter species has a smooth, valvatiform, dextrally coiled teleoconch and a sinistral, anastrophic (coaxial heterostrophic) protoconch. Bandel and Heidelberger (2002) noted the close similarity of the Devonian Palaeocarboninia and the Triassic Carboninia Bandel, 1996, the latter having a less elevated spire. For this reason, Bandel and Heidelberger (2002) and Bandel (2002b) suggested that the latter taxa may be connected with the post-Paleozoic marine

Valvatoitea. There is some resemblance in the teleoconch shape between Kuskokwimia and some late Paleozoic subulitoidean genera such as Girtyspira. However, as recently shown by Nu¨tzel et al. (2000), Girtyspira has an orthostrophic protoconch similar to that of the Meekospiridae (see also Kollmann and Yochelson, 1976). The family Meekospiridae, as well as other late Paleozoic (Nu¨tzel et al., 2000) and middle Paleozoic (Fry´da, 2001) members of the Subulitoidea, belong without doubt to the subclass Caenogastropoda. Thus, two middle Paleozoic (Devonian) genera of the Heterobranchia, Kuskokwimia and Palaeocarboninia, have no known counterpart among the late Paleozoic Heterobranchia, but similar forms may be found from the Triassic upwards to the Recent (their absence is probably only the result of our poor knowledge of Paleozoic gastropods). The gastropods belonging to the Heterobranchia have been well known from late Paleozoic strata for more than 100 years (Donald, 1898). These gastropods have slender, high-spired, multiwhorled shells bearing a sinistral protoconch and were united by

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FIGURE 12—1–6, Holotype of Kuskokwimia moorei. 1, Lateral view, 311; 2, apertural view, 315; 3, oblique apertural view, 313; 4, lateral view showing inner apertural lip, 315; 5, apical view showing concave depression formed by umbilicus of sinistrally coiled protoconch, 316; 6, detailed view of aperture showing slightly curved lamella on lower part of inner lip, 320.

FIGURE 13—Illustration showing reconstruction of Kuskokwimia moorei.

Knight (1931) in the family Streptacididae. The members of this family are relatively common in Carboniferous faunal communities (Donald, 1898; Knight, 1931; Batten, 1966; Anderson et al., 1985, 1990; Yoo, 1994). Bandel (1996) suggested raising the Streptacididae to superfamily rank and to unite the Streptacididae Knight, 1931 (bearing a smooth teleoconch) and the Donaldinidae Bandel, 1994 (bearing a teleoconch ornamented by spiral ribs). The youngest Streptacidioidea (Donaldina Knight, 1933; Streptacis Meek, 1872, Laxella Pan and Erwin, 2002) were recently found in Late Permian strata of South China (Pan and Erwin, 2002; Bandel, 2002b). The genus Heteroloxonema Fry´da, 2000, based on the Givetian (late Middle Devonian) Turritella moniliformis Goldfuss, 1844, from Germany, represents probably the oldest known streptacidoidean genus. Besides the members of the Streptacidoidea, there is also a fossil record for an additional group of Heterobranchia among late Paleozoic gastropods. Pan and Erwin (2002) described an extraordinary well-preserved gastropod fauna from Late Permian strata of South China. Among these gastropods they described a new species, Straparollus minutus, with a small planispirally coiled shell bearing a beautifully preserved heterobranch protoconch (see Pan and Erwin, 2002, figs. 10.6–10.11). There is no doubt that this species does not belong to the Euomphaloidea, as

FRY´DA AND BLODGETT—DEVONIAN GASTROPODS FROM ALASKA Pan and Erwin (2002) suggested, but rather to the Heterobranchia. As shown by several authors (Yoo, 1994; Bandel and Fry´da, 1998; and Nu¨tzel, 2002), Devonian to Permian gastropods belonging to the Euomphaloidea (Euomphalomorpha) have a characteristically large, openly coiled protoconch, which is formed only by an embryonic shell (protoconch I), and a true larval shell is lacking (Fry´da, 2001). The shell of ‘‘Straparollus’’ minutus Pan and Erwin, 2002 bears a true larval shell (protoconch II), which is distinctly sinistrally coiled (see Pan and Erwin, 2002, figs. 10.7–11). In addition, this shell closely resembles species of the Late Triassic heterobranch genus Stuoraxis Bandel, 1996. We therefore transfer ‘‘Straparollus’’ minutus to a different gastropod subclass, to the Heterobrachia, and to the genus Stuoraxis Bandel, 1996, which is the type genus of the family Stuoraxidae Bandel, 1996. This new evaluation of the systematic position of the Late Permian ‘‘Straparollus’’ minutus distinctly shows that the family Stuoraxidae Bandel, 1996 (belonging to the heterobranch superfamily Architectonicoidea Gray, 1850) began in Paleozoic time. Taken together, in Paleozoic time there were at least three different groups belonging to the subclass Heterobranchia Gray, 1840: the Streptacidoidea Knight, 1931 (?Middle Devonian, Early Carboniferous-Late Permian; Allogastropoda Haszprunar, 1985), Stuoraxidae (Late Permian, Architectonicoidea Gray, 1850); and the Devonian Kuskowimia Fry´da and Blodgett, 2001a, and Palaeocarboninia Bandel and Heidelberger, 2002. The higher taxonomic positions of the Devonian genera within the Heterobranchia are still uncertain. CONCLUSIONS

The data presented by the new Emsian gastropods from the Farewell terrane (west-central Alaska) contribute to both our knowledge of the paleobiogeographic position of the Farewell terrane as well as to the phylogeny of the Paleozoic gastropods. The following facts are worthy of note: 1. The paleobiogeographic affinities of the Emsian gastropod genera from the Farewell terrane (i.e., Straparollus (Eleutherospira), Quadricarina (Quadricarina), Balbinipleura, Euomphalopterus, Decorospira, Palaeozygopleura (Rhenozyga), Nanochilina) are definitively of Old World Realm character. However, at the species level, none of the species found in the Limestone Mountain fauna are known from nonaccretionary rocks of western North America (i.e., the Western Canada Province or Nevada Province), and are more closely allied with contemporaneous faunas of the European part of the Old World Realm. This is concordant with the Siberian and/or Uralian aspects of other elements of the Farewell terrane Paleozoic biota. 2. Quadricarina (Quadricarina?) noklebergi n. sp. is the oldest and hitherto first Early Devonian species of Quadricarina. It is its first species with a preserved protoconch, the morphology of which supports its placement to the Archaeogastropoda. 3. All Early Devonian members of the Palaeozygopleuridae and Loxonematidae had large protoconchs (with diameter of the first whorl ranging from about 0.3 to 0.5 mm). The protoconch sizes in both of the Emsian palaeozygopleurids from the Farewell terrane (i.e., Palaeozygopleura (Rhenozyga) reifenstuhli n. sp. and Medfrazyga clauticae n. sp.) also fit in this size range. Palaeozygopleura (Rhenozyga) reifenstuhli n. sp. represents the first record of this subgenus from North America. It is also its oldest known species. 4. The occurrence of Nanochilina gubanovi n. sp. and Balbinipleura krawczynskii n. sp. in the Early Devonian of the Farewell terrane represent the first record of the genera Nanochilina and Balbinipleura from North America.

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5. The Emsian gastropod fauna from the Farewell terrane (westcentral Alaska) includes the Archaeogastropoda, Caenogastropoda, and Heterobranchia, showing that these gastropod lineages were separated from one another since the Early Devonian. ACKNOWLEDGMENTS

The work was supported by the Alexander von Humboldt-Stiftung and grant 205/01/0143 (Grant Agency of the Czech Republic) to Fry´da. We thank the Alaska Division of Geological and Geophysical Surveys for providing helicopter support to Blodgett, which allowed for the collection of the studied fauna. We also thank K. Bandel (Germany), V. Krawczynski (Poland), and R. D. Hoare (Ohio) for their thoughtful reviews of the manuscript. REFERENCES

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