Journal of the Czech Geological Society 44/3ñ4(1999) 309

Secondary shell deposits in a new plectonotid gastropod genus (Bellerophontoidea, Mollusca) from the Early Devonian of Bohemia

Sekund·rnÌ schr·nkovÈ uloûeniny u novÈho plectonotidnÌho gastropodovÈho rodu (Bellerophontoidea, Mollusca) ze spodnÌho devonu »ech (Czech summary)

(2 text-figs)

JIÿÕ FR›DA

Czech Geological Survey, Kl·rov 3, 118 21 Praha 1, Czech Republic, [email protected]

Secondary shell deposits are described in a new plectonotid genus, Blodgettinotus, from the Boucotonotus-Palaeozygopleura Community of the Prague Basin (Bohemia). The new taxon was found in the uppermost part of the T¯ebotov Limestone (Daleje-T¯ebotov Formation; late Emsian, late Early Devonian). The genera Boucotonotus and Blodgettinotus share some shell characters and are placed in a new tribe Boucotonotini of the subfamily Plectonotinae. The occurrence of secondary shell deposits in bellerophontiform molluscs is discussed. It is suggested that they were developed independently in several groups of these molluscs; thus, this feature has limited significance for their suprageneric classification.

Key words: Paleozoic, Devonian, Gastropoda, Bellerophontoidea, secondary shell deposists, Prague Basin

Introduction derstanding of the early evolution of Mollusca, but the still poor knowledge of these molluscs has provided suf- The higher classification of a bellerophontiform molluscs, ficient space for many, often contradictory, speculations. one of the most frequently discussed group of the Paleo- In this short paper, an occurrence of secondary shell de- zoic molluscs, is still problematic (see Yochelson 1967, posits in a plectonotid bellerophontoidean is described for Horn˝ 1992, Peel 1991a,b, Wahlman 1992, and Fr˝da the first time. All the herein described specimens are de- 1999a for review). Unusual attention in this molluscan posited in the collection of Ji¯Ì Fr˝da, Czech Geological group has been caused by their key-position in evolutio- Survey, Prague. nary models describing phylogenetic relationships between the classes Monoplacophora and Gastropoda. Systematic part Knight (1952) considered bellerophontoideans to be tor- Subclass Amphigastropoda ted gastropods forming an intermediate group between Superfamily Bellerophontoidea MíCoy, 1851 isostrophic monoplacophorans and pleurotomarioidean Family Bucaniidae Ulrich and Scofield, 1897 archaeogastropods. On the other hand, Yochelson (1967, 1984) suggested that bellerophontoideans may be deri- Remarks: Recently Wahlman (1992) discussed the ved from pleurotomarioidean archaeogastropods and their suprageneric classification of bellerophontoidean mol- shells are secondarily symmetrical. In addition, Rollins luscs in detail and he again raised the Bucaniidae to fa- and Batten (1968) suggested that the bellerophontiform mily rank as their authors, Ulrich and Scofield (1897), and pleurotomarioidean gastropods originated indepen- had done. Koken (1925) considered this group to be only dently from monoplacophorans several times during the a subfamily of the Bellerophontidae. This opinion was Cambrian, Ordovician and Devonian, and thus gastropods later followed by Knight et al. (1960) and Horn˝ (1963). represent a polyphyletic group. Recently Bandel and Gel- Wahlman (1992) recognized four subfamilies within the dmacher (1996) recalled Naefís (1911) almost forgotten Bucaniidae: Bucaniinae Ulrich and Scofield, 1897, Sal- hypothesis considering bellerophontiform molluscs pingostomatinae Koken, 1925, Plectonotinae Boucot and (=Amphigastropoda) to represent gastropods in which the Yochelson, 1966, and his new subfamily Undulabucanii- torsion of the soft body occurred during the early ben- nae. Wahlman considered the family Tropidodiscidae to thic stage, resulting in a bilaterally symmetrical shell. be the most primitive family of all of the slit-bearing fa- This model seems to be evidenced by the discovery of milies. The family Bucaniidae was derived, according to a non-archaogastropod protoconch type in Bellerophon him, from tropidodiscid ancestors. The members of Plec- (Fr˝da 1998, 1999a). In contrast to all the above menti- tonotinae are considered to be more advanced Bucanii- oned models, Runnegar and Pojeta (1974) suggested that dae. Wahlman (1992) represents the last detailed study all bellerophontoideans are isostrophic monoplacopho- of the suprageneric classification of bellerophontoidean rans. Recent data of the protoconch morphology in the molluscs and this classification is also followed here. For bellerophontiform molluscs (Dzik 1978, 1981; Horn˝ this reason the subfamily Plectonotinae Boucot and Yo- 1993; Fr˝da 1998a, 1999a, c) suggest that they may re- chelson, 1966 is here also placed within the family Bu- present a polyphyletic group. To sum up, the bellerophon- caniidae. However, the family-level classification of the tiform molluscs are very important group(s) for our un- bellerophontoidean molluscs is still not stable and a new 310 Journal of the Czech Geological Society 44/3ñ4(1999)

A B

C D

Fig. 1. Blodgettinotus ornatus sp. nov. from the uppermost part of the T¯ebotov Limestone (Daleje-T¯ebotov Formation; late Emsian, late Early Devonian). A ñ dorsal view of holotype showing a trilobate dorsum in juvenile whorl, x45, B ñ apertural view of holotype, parietal region covered by inductural shell deposits, x40, C ñ paratype A, dorsal view showing inductural shell deposits of Euphemitesñtype, x32, D ñ detail view of figure 1B, x92. detailed revision is necessary which will also consider cave sinus at the lateral shell lobe; collabral ribs and lu- much new data published during last ten years. The shell nulae regularly spaced; umbilicus narrow or filled by se- characters of some plectonotids like those placed here in condary shell deposits. the new tribe Boucotonotini seem to be closer to mem- Remarks: Boucot and Saul (in Saul ñ Boucot ñ Finks bers of the Bellerophontidae than to the Bucaniidae. 1963) transferred the genus Plectonotus from the family However, the higher position of the subfamily Plectono- Sinuitidae to the Bellerophontidae because they found tinae is not the subject of this study and remains opened a true slit and selenizone in Plectonotus fraternus (Reed for future studies. 1908) from the Devonian of Ghana. Horn˝ (1963) on the basis this discovery also placed Plectonotus near the ge- Subfamily Plectonotinae Boucot and Yochelson, 1966 nus Tetranota within the subfamily Bucaniinae. The se- Tribe Boucotonotini nov. lenizone was later discovered also in the type species of Plectonotus, Plectonotus derbyi Clarke, 1899 (Boucot Type genus: Boucotonotus Fr˝da and Manda, 1997 1965; Peel 1974; Boucot et al. 1986). Boucot and Yochel- Diagnosis: Members of Plectonotinae ornamented by son (1966) established a new subfamily Plectonotinae for distinct collabral ribs; aperture bearing an anteriorly con- ìmoderately large slit-bearing bellerophontid gastropods Journal of the Czech Geological Society 44/3ñ4(1999) 311

B A

C D

Fig. 2. AñC. Boucotonotus mareki from the uppermost part of the T¯ebotov Limestone (Daleje-T¯ebotov Formation, late Emsian, late Early Devonian). A ñ dorsal view showing the distinct, regularly spaced collabral ribs and lunulae, CGU JF 148, x38. B ñ abapertural view of the same shell, x35, C ñ lateral view showing a periumbilical smooth ridge formed by the secondary shell deposits, CGU JF 148, x27. D ñ Blodget- tinotus ornatus sp. nov., holotype, lateral view showing coinductural and inductural shell deposits, x33. having a prominent raised median lobe that forms a tri- da (1997) introduced a new taxon Boucotonotus as a sub- lobed cross sectionì. According to these authors Plecto- genus of Plectonotus, but they noted that it may repre- notus Clarke, 1899 represents the only known genus of sent a separate genus because of its unusual shell featu- this subfamily. Peel (1974) redescribed the genus Trito- res. In contrast to species of Plectonotus (Plectonotus) nophon ÷pik, 1953, which is based on Kokenospira (Tri- and Plectonotus (Plectonotoides), the aperture of Bou- tonophon) trimetra ÷pik, 1953. This author placed in cotonotus bears an anteriorly concave sinus at the Tritonophon most of the forms earlier assigned to Plec- lateral shell lobe. In addition, it differs from Plectono- tonotus trilobatus (Sowerby in Murchison, 1839). The tus (Plectonotus), Plectonotus (Plectonotoides), and Tri- genus Tritonophon Opik, 1953 according to Peel (1974) tonophon by its distinct collabral ornamentation of both is distinguished from the genus Plectonotus Clarke, 1899 the shell and selenizone. The shells of Blodgettinotus gen. by ìits more pronounced trilobation producing a narrow nov. bear the same shell characters (i.e., distinct collabral and strongly vaulted median lobeî. Boucot et al. (1986) ribs; aperture bearing an anteriorly concave sinus at the established the subgenus Plectonotus (Plectonotoides), lateral shell lobe) as Boucotonotus, which are unknown based on the relatively small Lower Devonian species, amongst other plectonotids. For this reason, Boucotono- Plectonotus gaspensis Clarke, 1908. Wahlman (1992) tus is considered here to be a separate genus related to transferred the Ordovician genus Tetranota to the subfa- Blodgettinotus gen. nov. Both genera share the above mily Plectonotinae and noted its similarity to genus Ko- mentioned shell features, but having a different dorsum kenospira of the subfamily Bucaniinae. Fr˝da and Man- in the adult shell (see below) and are placed here in a new 312 Journal of the Czech Geological Society 44/3ñ4(1999) tribe Boucotonotini to emphasize their closer phyloge- gularly spaced lunulae (Figs 1AñD, 2D). The shells of netic connection within the Plectonotinae. Boucotonoti- species belonging to the subgenera Plectonotus (Plecto- ni show some shell characters (very narrow or closed notus) and Plectonotus (Plectonotoides) are smooth, with umbilicus, globose adult shell of Blodgettinotus) which only growth lines developed on their shell surface. In are closer to members of the Bellerophontidae than to the some species of the subgenus Plectonotus (Plectonotoi- Bucaniidae. On the other hand, Plectonotini nom. nov., des), such as Plectonotus (Plectonotoides) boucoti Peel, including Plectonotus (Plectonotus), Plectonotus (Plec- 1974 and Plectonotus (Plectonotoides) cherylae Peel, tonotoides), Tritonophon, and Tetranota, are considered 1974 (see also Peel 1991, fig. 14), the shell is ornamen- to be more primitive Plectonotinae. The above mentio- ted by very fine spiral lirae. A similar type of shell or- ned data, however, suggests that this problem needs more namentation is also developed in some species of Trito- detailed study, as does the whole suprageneric classifi- nophon ÷pik, 1953 (Peel 1974). The aperture of cation of bellerophontoidean molluscs. Blodgettinotus bearing an anteriorly concave sinus at the Included genera: both lateral shell lobes is similar to that in Boucotono- Boucotonotus Fr˝da and Manda, 1997 tus. This character also differentiates Bouconotus and Blodgettinotus gen. nov. Blodgettinotus from Plectonotus Clarke, 1899 and Tri- tonophon ÷pik, 1953. Blodgettinotus gen. nov. Species included: Only the type species Blodget- tinotus ornatus gen. et sp. nov. is hitherto known. Type species: Blodgettinotus ornatus gen. et sp. nov.; late Em- sian (late Early Devonian); Prague Basin, Bohemia. Blodgettinotus ornatus sp. nov. Etymology: Blodgettinotus, in honour of the American paleonto- Text-figs 1AñD, 2D logist Robert B. Blodgett who has contributed much to our knowledge of Devonian gastropods. Holotype: Specimen »G⁄ JF 770, figured here as Figs 1A, B, D, 2D. Diagnosis: Small plectonotid shell ornamented by P aratype: Specimen »G⁄ JF 771, figured here as Fig. 1C. distinct collabral ribs; dorsum of juvenile whorls distinct- Type horizon: The uppermost part of the T¯ebotov Limestone, Daleje-T¯ebotov Formation; late Emsian, late Early Devonian. ly trilobate with selenizone occupying the full width of Type locality: HolynÏ near Prague, central Bohemia. the upper surface of the median lobe; dorsum of later Etymology: ornatus (Lat.), bearing ornament. (adult) whorl rounded; selenizone ornamentation consi- sting of distinct lunulae; collabral ribs and lunulae regu- Diagnosis: Because of monotypy, see that of genus. larly spaced; umbilici covered by coinductural shell de- Description: Bellerophontid with bilaterally symme- posits; inner lip in adult whorl covered by inductural shell trical shell having height/width ratio slightly less than 1; deposits with reticulate ornamentation; inductural depo- early whorls distinctly trilobate (Fig. 1A) but gerontic sits form several spiral ribs of Euphemites-type in geron- whorl rounded (Fig. 1C); relatively wide selenizone oc- tic shells. cupying the full width of the upper surface of the medi- Comparison: Blodgettinotus gen. n. is closest to an lobe in juvenile shell whorls; selenizone width about Boucotonotus Fr˝da and Manda, 1997 among all belle- 1/5 of dorsum width; flat central lobe low, separated from rophontoidean genera. The former genus may be distin- the lateral lobes by very shallow furrow on each side; guished from the latter by shape of its dorsum and pre- lateral lobes gently arched; umbilici covered by smooth sence of characteristic inductural deposits in the adult coinductural deposits; anterior margin of the aperture shell, as well as by a slightly wider shell. The dorsum of with narrow sinus having in its middle a wide slit; width the gerontic whorl in all species of Boucotonotus is dis- of the sinus about 1/2 of dorsum width; flat selenizone tinctly trilobate (see Horn˝ 1963, Pl. 28, Figs 1, 3; Fr˝- generated by slit forms the upper surface of the median da ñ Manda 1997, Pl. 1, Fig. 6; herein Fig. 2A, B) but it lobe; apertural margin runs from the selenizone obliquel- is rounded in Blodgettinotus gen. nov. In addition, the ly forwards, at position of interlobe furrow it abruptly adult shells of the latter genus is partly covered by in- turns backwards and then curves smoothly towards cir- ductural shell deposits forming a characteristic ornamen- cumbilical region to form an anteriorly concave, shallow tation (Figs 1AñD, 2D), in contrast to Boucotonotus in sinus at the lateral shell lobe (Fig. 1A); shell ornamen- which only a smooth periumbilical ridge (Fig. 2C) for- ted by distinct collabral ribs; selenizone ornamentation med probably by coinductural shell deposits was found. consisting of distinct lunulae; collabral ribs and lunulae This smooth periumbilical ridge is also found in Blodget- regularly spaced and their distance about 1/3 of seleni- tinotus gen. n. (Fig. 2D). zone width (Fig. 1AñC); inner lip of adult whorl cove- The new genus Blodgettinotus may be easily distin- red by inductural shell deposits with reticulate ornamen- guished from species of Plectonotus (Plectonotus) Clar- tation (Fig. 1D); the distance between the spiral threads, ke, 1899 and Plectonotus (Plectonotoides) Boucot, Rohr, as well as that between the radial threads forming the Gray, Faria and Colbath, 1986 by its distinct shell orna- reticulate ornamentation is the same and equal to about mentation, the shape of its aperture and adult dorsum. 1/4 of selenizone width; smooth periumbilical ridge se- The shell of Blodgettinotus is ornamented by distinct, parating dorsolateral and circumbilical regions projects regularly spaced collabral ribs and its selenizone by re- about 1/4 of a volution from the aperture (Fig. 2D); this Journal of the Czech Geological Society 44/3ñ4(1999) 313 rounded ridge is formed by coinductural shell deposits; vy callus instead of ribs (see Horn˝ 1963, fig. 15). The in the most adult whorl inductural deposits form several reticulate ornamentation of the inductural deposits in spiral ribs of Euphemites-type (Fig. 1C); shell structure Blodgettinotus ornatus sp. nov. is very similar to that in and protoconch unknown. Paleuphemites petrboki (compare Horn˝ 1963, Pl. XLIII, Remarks: Blodgettinotus ornatus sp. nov. is rare and fig. 1 and herein Figs 1B, D). Also a change of morpho- only two complete shell are hitherto known from its type logy of the inductural shell deposits in gerontic shells is locality. a character shared by both genera. Secondary shell deposits limited to the parietal regi- Secondary shell deposits in bellerophontiform on and portions of the umbilical region were also previ- molluscs ously described in some representatives of the family Si- nuitidae [e. g., Sinuites cancellatus (Hall 1847), Sinuites Secondary shell deposits are secreted on the surface of granistriatus (Ulrich 1897), and Sinuites (Strangulites) gastropod shells by flaps of their mantle and also occur strangulatus (Perner 1903)] (see Knight 1941; Horn˝ in several groups of the bellerophontiform molluscs. The 1990; Wahlman 1992). Fr˝da and Marco (1996) descri- Carboniferous-Permian members of the family Euphemi- bed a Middle Ordovician species of genus Hispanosinu- tidae Knight, 1956, represent a typical group of such bel- ites, Hispanosinuites peeli, the shell of which is entirely lerophontiform molluscs. Secondary shell deposits enti- covered by secondary shell deposits. This genus of their rely cover the outer surface of their shells. The shell new subfamily Hispanosinuitinae was interpreted as structure of the representatives of this family has been stu- a member of a highly specialized phylogenetic lineage died and interpreted by many authors (Weller 1930; Mo- separated from the morphological range of the genus Si- ore 1941; Yochelson 1960; McClintock 1967; Harper ñ nuites during the Early Ordovician. Similar secondary Rollins 1985; etc.). Moore (1941) described secondary shell deposits were described in ìSinuitesì by Horn˝ shell deposits in Euphemites Warthin, 1930, in detail and (1996). Rollins (1966) described thick, padlike parietal used the terms ìinducturaî, ìperinducturaî and ìcoindu- deposits in the Devonian genus Ptomatis. Recently, high- cturaî. The inductura is a secondary shell layer extending ly ornamented secondary shell deposits were found in from the inner side of the aperture over the parietal regi- genus Branzovodiscus Fr˝da, 1999, which was tentatively on, columellar lip, and part or all of the outer shell surfa- placed in the subfamily Bucanellinae of the Sinuitidae ce. In Euphemites, Moore (1941) used the term inductu- because of its resemblance with genus Sinuitina Knight, ra for layers on the outer shell surface bearing numerous 1945 in terms of its general shell shape as well as of its spiral costae. This author concluded that the inductura had helmet-shaped dorsum (subgenus Sinuitina (Sinuitina)). been secreted by a forward-growing posterior flap of the The genus Sinuitina was placed in the subfamily Buca- mantle. The perinductura is a secondary shell layer secre- nellinae by Knight et al. (1960). However, the shell mor- ted by the mantle flap and reflected back over the outer phology of Sinuitina and Branzovodiscus seems to be far apertural lip. This shell layer obscures the growth lines from that of the type genus Bucanella Meek, 1871. The and is the innermost of three outer shell layers. In Euphe- ripple-like pattern of slightly irregular ribs in the mid- mites, the perinductura is the layer on the outer shell sur- dle of dorsum of Sinuitina (Globosinuitina) Fr˝da, 1998 face and is either smooth and unornamented or bears no- may also be the result of perinductural secondary shell des or nodose ridges. The coinductura is a secondary shell deposits. layer extending over the inner lip within the aperture and The occurrence of secondary shell deposits limited to covering only a small part of the inductura. Yochelson the parietal region was noted by Wahlman (1992) also (1960) suggested that the coinductura was secreted by the in the genera Bucania and Salpingostoma belonging to same part of the mantle as the inductura, in contrast with the family Bucaniidae, as well as in genus Carinariop- Mooreís (1941) opinion that there was no obvious corre- sis of the family Carinaropsidae. Secondary shell depo- lation between the coinductura and inductura. sits are also known among members of the subfamily Horn˝ (1962, 1963) described a new euphemitid ge- Bellerophontinae such as Bellerophon and Kodymites. nus, Paleuphemites, shells of which bear well developed These deposits are typically smooth, without any orna- secondary shell deposits but only in the parietal and um- mentation and they are restricted only to the inner lip and/ bilical regions. This genus is based on Paleuphemites or they fill the umbilici. Secondary shell deposits of si- petrboki Horn˝, 1962 from the Dvorce-Prokop Limesto- milar morphology also occurs in the genera Cymbularia ne of Praha Formation (Pragian, middle Early Devoni- Koken, 1896, Prosoptychus Perner, 1903, and Coelocy- an) of the Prague Basin. Paleuphemites petrboki was in- clus Perner, 1903, belonging to the subfamily Cymbula- terpreted as the oldest representative of the family rinae Horn˝, 1963. Euphemitidae. The shells of the latter species have an in- Wahlman (1992) discussed the functional significan- ner lip covered by parietal inductura generating longitu- ce of the secondary shell deposits in bellerophontiform dinal (spiral) ribs forming a reticulate ornamentation with molluscs. According to him, these deposits serve two intersecting collabral ribs (see Horn˝ 1963, fig. 14). Ac- functions. First, they add weight to the part of the shell cording to this author, in the gerontic shells of Paleuphe- that lies on the central portion of the foot and so help to mites petrboki the inductural deposits are formed by hea- stabilize the shell under higher energy conditions. Mo- 314 Journal of the Czech Geological Society 44/3ñ4(1999) dification of the design of the parietal shell region is con- ñ (1998b): Some new and better recognized Devonian gastropods from sidered to be a second reason for the development of se- the Prague Basin (Bohemia): part II. ñ Bulletin of the Czech condary shell deposits. However, the considerable vari- Geological Survey, 73, 4, 355ñ363, Praha. ñ (1999a): Higher classification of the Paleozoic gastropods inferred ability in terms of the shape, position and ornamentation from their early shell ontogeny. ñ Journal of the Czech Geological of the secondary shell deposits in the bellerophontiform Society, 44: 137ñ153. molluscs suggests that these deposits were developed for ñ (1999b): Three new gastropod genera from the Early Devonian of many different reasons. Bohemia. ñ Bulletin of the Czech Geological Survey, 74, 1, 31ñ38. ñ (1999c): Suggestions for polyphyletism of Paleozoic bellerophonti- form molluscs inferred from their protoconch morphology. ñ 65th Conclusions Annual Meeting, American Malacological Society, Pittsburgh, 30. Fr˝da, J. ñ GutiÈrrezñMarco, J. C. (1996): An unusual new sinuitid The above short overview clearly shows that secondary mollusc (Bellerophontoidea, Gastropoda) from the Ordovician of shell deposits occurs in many groups of almost all known Spain. ñ J. Paleont., 70, 4, 598ñ605. families of the Bellerophontoidea. This shell feature was Fr˝da, J. ñ Manda, ä. (1997): A gastropod faunule from the Monograptus uniformis graptolite Biozone (Early Lochkovian, Early Devonian) probably independently developed for several different in Bohemia. ñ Mitteilungen aus dem Geologisch-Pal‰ontologischen reasons. The significance of secondary shell deposits for Institut der Universit‰t Hamburg, 80: 59ñ122. the suprageneric classification of the bellerophontoide- Hall, J. (1847): Paleontology of New York, 1, Containing descriptions of an molluscs seems to be limited. Also, the evolutionary the organic remains of the lower division of the New York System: relationships of bellerophontoideans with such deposits Albany, N.Y., C. Van Benthuysen, 338 pp. Harper, J. A., ñ Rollins, H. B. (1985): Infaunal or semi-infaunal are probably much more complicated than were sugges- bellerophont gastropods: analysis of Euphemites and functionally ted by Fr˝da and Marco (1996). The herein described related taxa. Lethaia, 18:21ñ37. occurrence of the secondary shell deposits in Blodgetti- Horn˝, R. (1962): New genera of Bohemian Lower Paleozoic notus ornatus sp. nov. belonging to the subfamily Plec- Bellerophontina. ñ VÏstnÌk ⁄⁄G, 37:473ñ476. tonotinae is a further contribution to our knowledge of ñ (1963): Lower Paleozoic Bellerophontina (Gastropoda) of Bohemia. ñ Sbornik ⁄⁄G, ¯ada P, 2:57ñ164. this shell feature in bellerophontoidean molluscs. ñ (1990): SvalovÈ vtisky u Sinuites (Strangulites) (Mollusca) z ËeskÈho ordoviku. [Muscle scars in Sinuites (Strangulites) (Mollusca) from Acknowledgments. This publication is based on the work the Ordovician of Bohemia]. ñ »asopis N·rodnÌho Muzea, ÿada p¯ÌrodovÏdeck·†155 (for 1986) 3ñ4:109ñ118. sponsored by the U. S. ñ Czechoslovak Science and Tech- ñ (1992): V˝voj n·zoru na klasifikaci cyklomyarnich mÏkk˝ö˘ nology Joint Fund in cooperation with the Czech Geo- (Mollusca, Monoplacophora). ñ »asopis N·rodnÌho Muzea, ÿada logical Survey and U. S. Geological Survey under Pro- p¯ÌrodovÏdn·, 157, 1ñ4:13ñ50. ject Number 95057. I also wish to acknowledge Robert ñ (1993): Shell morphology and mode of life of the Lower Devonian B. Blodgett (Corvallis, Oregon) and Dave M. Rohr (Al- cyclomyan Neocyrtolites (Mollusca, Tergomya). ñ »asopis N·rodnÌho Muzea, ÿada p¯ÌrodovÏdn·, 162, 1ñ4:57ñ66. pine, Texas) for improving language and for their help- ñ (1996): Secondary shell deposits and presumed mode of life in ful, critical reviews of this paper. Sinuites. ñ Acta musei Nationalis Pragae, Serie B, 51, 1ñ4:89ñ103. 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Sekund·rnÌ schr·nkovÈ uloûeniny u novÈho plectonotidnÌho gastropodovÈho rodu (Bellerophontoidea, Mollusca) ze spodnÌho devonu »ech

Sekund·rnÌ schr·nkovÈ uloûeniny jsou pops·ny u novÈho plectonotidnÌho rodu Blodgettinotus z†gastropodovÈho spoleËenstva Boucotonotus- Palaeozygopleura praûskÈ p·nve. Tento taxon byl nalezen v nejvyööÌ Ë·sti t¯ebotovsk˝ch v·penc˘ (dalejsko-t¯ebotovskÈ souvrstvÌ, pozdnÌ ems, nejv˝ööÌ spodnÌ devon). Na z·kladÏ zjiötÏnÌ nÏkter˝ch spoleËn˝ch znak˘ jsou rody Boucotonotus a Blodgettinotus umÌstÏny do novÈho tribu Boucotonotini pat¯ÌcÌ do podËeledi Plectonotinae. Je diskutov·n v˝skyt sekund·rnÌch schr·nkov˝ch uloûenin u bellerophontoformnÌch mÏkk˝ö˘. Tyto uloûeniny se pravdÏpodobnÏ vyvinuly nez·visle v r˘zn˝ch skupin·ch tÏchto mÏkk˝ö˘ a majÌ tedy omezen˝ v˝znam pro jejich klasifikaci. 316 Journal of the Czech Geological Society 44/3ñ4(1999)