THE LAZARUS AMMONOID FAMILY GONIATITIDAE, the TETRANGULARLY COILED ENTOGONITIDAE, and MISSISSIPPIAN BIOGEOGRAPHY Author(S): DIETER KORN, CHRISTIAN KLUG, ROYAL H

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THE LAZARUS AMMONOID FAMILY GONIATITIDAE, THE TETRANGULARLY COILED ENTOGONITIDAE, AND MISSISSIPPIAN BIOGEOGRAPHY Author(s): DIETER KORN, CHRISTIAN KLUG, ROYAL H. MAPES Source: Journal of Paleontology, 79(2):356-365. Published By: The Paleontological Society DOI: http://dx.doi.org/10.1666/0022-3360(2005)079<0356:TLAFGT>2.0.CO;2 URL: http://www.bioone.org/doi/full/10.1666/0022-3360%282005%29079%3C0356%3ATLAFGT %3E2.0.CO%3B2

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THE LAZARUS AMMONOID FAMILY GONIATITIDAE, THE TETRANGULARLY COILED ENTOGONITIDAE, AND MISSISSIPPIAN BIOGEOGRAPHY

DIETER KORN,1 CHRISTIAN KLUG,2 AND ROYAL H. MAPES3 1Museum fuÈr Naturkunde der Humboldt-UniversitaÈt zu Berlin, Invalidenstraûe 43, D-10115 Berlin, Germany, Ͻ[email protected]Ͼ, 2PalaÈontologisches Institut und Museum, UniversitaÈt ZuÈrich, Karl-Schmid-Str. 4, CH-8006 ZuÈrich, Switzerland, Ͻ[email protected]Ͼ, and 3Department of Geological Sciences, Ohio University, Athens 45701, Ͻ[email protected]Ͼ

ABSTRACTÐA small early Late ViseÂan (Mississippian) ammonoid assemblage with Entogonites saharensis new species and Goniatites lazarus new species is described from the eastern Anti±Atlas of Morocco, being the ®rst African record of Entogonites. The family Goniatitidae is a typical Lazarus taxon, which, after a gap representing approximately 10 million years, reappears in the fossil record. The genera Entogonites and Goniatites have a wide paleogeographic distribution (northwest Laurentia, northern and southern Variscides, north Gondwana). This indicates ammonoid cosmopolitism at the genus level at the end of the middle ViseÂan, before late ViseÂan ammonoid provinces formed. Entogonites with tetrangularly coiled juvenile whorls and with a low aperture probably had a planktonic lifestyle.

INTRODUCTION stratigraphic declarations can be made. What can be said is that HE MISSISSIPPIAN is a time in which the evolution of the Am- Entogonites does not co-occur in the same rocks with Maxigon- T monoidea is characterized by phases of rapid diversi®cation, iatites. Based on the presence of the genus Entogonites, however, but signi®cant character stasis is known from several lineages. the age of the assemblage described here can be determined as Adaptive radiations were probably triggered by sea level changes, B1 Zone or, more probably, earliest B2 Zone of Riley (1990). especially regressions, and subsequent partitioning of habitats. The examined material is housed in the Museum fuÈr Natur- Dispersal of species was probably forced by transgressive events. kunde, Berlin, catalogue numbers MB.C.5301 to MB.C.5326 and Mississippian ammonoids are well known from Late ViseÂan (cf. in the Institut fuÈr Geowissenschaften, TuÈbingen, catalogue num- Korn, 1988, for more literature) and Serpukhovian (cf. Gordon, ber GPIT 1851±97. 1965; Ruzhencev and Bogoslovskaya, 1971, for more literature) Abbreviations in the text are as follows: D, conch diameter; W, strata. In these periods, the ammonoids became extremely diverse, whorl height; H, whorl height; U, umbilical width; A, apertural height; WER, whorl expansion rate (i.e., the expansion rate of the but comparatively little is known about their Early and Middle 2 ViseÂan ancestry. Also, little is known about the paleogeographic whorl spiral; calculated [D/(D Ϫ A)] ). distribution of Early and Middle ViseÂan ammonoids, since oc- THE OLDEST RECORDS OF GONIATITES currences outside of England (Riley, 1996) are very rare. Different species of Goniatites appear almost synchronously Occurrences in North Africa have a signi®cant potential to ®ll within the various geographic regions in the Late ViseÂan. Strati- some gaps in the knowledge of Mississippian ammonoids. Faunas graphically well-dated occurrences are known from the Rheno- are already known from the base of the Mississippian to the Mos- hercynian (especially the Rhenish Massif and Harz Mountains), covian, and many genus zones are represented by rather diverse where Goniatites hudsoni Bisat, 1934 occurs immediately above assemblages. DeleÂpine (1941) published a monograph on Missis- the so-called Grimmeri Bed. This is a thin cherty shale horizon sippian ammonoids from Morocco, Pareyn (1961) described nu- that contains Entogonites grimmeri (Kittl, 1904a) in large quan- merous Late Tournaisian, ViseÂan, and Serpukhovian assemblages tities. A co-occurrence of these two species is known from only from northwest Algeria, and Conrad (1984) illustrated Late Tour- one locality (Medebach±Bromberg; Nicolaus, 1963), where they naisian and Early ViseÂan material from Central and South Algeria. were collected from manganese nodules immediately above the Recently, Korn et al. (1999) showed that well-preserved Late Vi- Grimmeri Bed. This suggests that in the Rhenish Massif the over- seÂan ammonoids occur in the vicinity of Erfoud and Taouz (east- lap of Entogonites and Goniatites is limited to a very thin horizon ern Anti±Atlas, Morocco). Middle and Late Tournaisian assem- of approximately 10 cm. blages also occur in this area (Korn et al., 2002, 2003). Co-occurrences of Entogonites and Goniatites are also known In the following, a low diversity fauna with species of Ento- from the Kiruktagiak River in the Brooks Range of Alaska (Gor- gonites Kittl, 1904b and Goniatites de Haan, 1825, most probably don, 1957), but the specimens of Entogonites borealis Gordon, of early Late ViseÂan age (B1 Zone or earliest B2 Zone of Riley, 1957 and Goniatites americanus Gordon, 1971 were collected 1990), is described. This fauna contains one of the stratigraphi- from an approximately 15 m thick rock unit and it is not clear if cally oldest known representatives of Goniatites, which co-occurs only one fossil horizon is represented there. In Utah these two with the distinctive Entogonites with its unique tetrangularly species were found in the Chainman Shale (Gordon, 1971) where coiled inner whorls, a morphology unduplicated in the history of Goniatites americanus occurs approximately 15 m above Ento- the Ammonoidea. gonites borealis. Titus and Riley (1997) reported a succession of Entogonites species from Utah, a lower bed with E. borealis, MATERIAL which they regard as a synonym of E. nasutus (Schmidt, 1941), All the material comes from 12 km southeast of the Dar Kaoua and a higher occurrence with E. grimmeri. Titus and Riley (1997) Oasis, 32 km southeast of Erfoud, eastern Anti±Atlas, Morocco found specimens of the genus Goniatites in both horizons, and (Fig. 1); it was surface collected and is most probably of early pointed out the cryptic origin of the genus. Late ViseÂan age (Fig. 2). It is the same locality from which the A second assemblage in which Entogonites and Goniatites co- fauna with Maxigoniatites Korn et al., 1999 and Beyrichoceras occur in the same horizon is the new Moroccan assemblage de- Hyatt, 1884, described by Korn et al. (1999), was recorded. Ex- scribed here. In this assemblage Entogonites saharensis n. sp. was posures in this area are virtually nonexistent, and hence, no exact found in the body chambers of Goniatites lazarus n. sp. 356 KORN ET AL.ÐGONIATITIDAE AND ENTOGONITIDAE 357

FIGURE 2ÐStratigraphic distribution of the Mississippian genera of the Goniatitidae, displaying the gap in the record that spans from the latest Tournaisian to the Middle ViseÂan. FIGURE 1ÐMap of the eastern Anti±Atlas with the fossil locality indi- cated by a star located approximately midway between the communi- ties of Rissani and Taouz and about 5 km west of Erg Chebbi. Goniatitidae. Evidence is missing from the latest Tournaisian and the early and middle ViseÂan rocks (Fig. 2). This pattern of stratigraphic distribution of representatives of the family Goniatitidae displays the characteristic expression of the Lazarus Effect. The THE ANCESTRY OF GONIATITES gap in the record, spanning approximately 10 Ma (Menning et The stratigraphically distant early Late Tournaisian Progonia- al., 2000), remains problematic. tites Korn et al., 2003 displays a conch and suture morphology which is very close to Goniatites. Unfortunately, no ornament is EVOLUTIONARY TRENDS WITHIN GONIATITES known from Progoniatites, except for almost straight, coarse un- All species of Goniatites have a similar conch morphology, and dulations on steinkerns. The suture line is, except for the wider differences are mainly expressed by the ornament and suture. external lobe with its straight ¯anks, very similar to Goniatites Some species possess only crenulated growth lines, while in oth- (Fig. 3). ers there is a very strong crenulation, causing a spiral ornament. Interestingly, the suture line of Progoniatites much more close- The suture line is the most distinctive character within Goniatites. ly resembles that of stratigraphically younger species of Gonia- It shows a V-shaped or Y-shaped external lobe with a median tites, such as G. ®mbriatus Foord and Crick, 1897, than that of saddle that has a height of 0.35±0.50 of the external lobe depth. the older taxon G. lazarus n. sp. The ventrolateral saddle is al- The ventrolateral saddle is narrowly rounded, angular, or even ready angular in Progoniatites, and the median saddle is higher pointed, and the adventive lobe is V-shaped with a more or less (0.4) than in G. lazarus (0.34). sinuous ventral ¯ank (Fig. 3). Progoniatites is known from early Late Tournaisian rocks of As Figure 4 shows, the distribution of characters within Gon- the North Urals (Kusina, 2000; ``Zhifangoceras karense''), Thu- iatites displays a mosaic pattern. The characters median saddle ringia (Schindewolf, 1926, 1939; ``Glyphioceras angustiloba- height, shape of the external lobe, shape of the ventrolateral sad- tum''), and North Africa (Conrad and Pareyn, 1968; ``Goniatites dle, and spiral ornament are, for instance, not at all correlated. cf. crenistria''). Similar forms are not known from the latest Tour- Thus, it is dif®cult to reconstruct evolutionary lineages within naisian Erdbach Limestone and its lateral equivalents, although Goniatites based on these characters. these are well known and contain comparatively rich ammonoid A trend towards wider external lobes and higher median sad- assemblages. Members of the Goniatitidae then reappear in the dles can be observed in the stratigrapic succession of Goniatites highest beds with Entogonites, and Goniatites lazarus is one of species (Drahovzal, 1972; Drahovzal and Quinn, 1972). Strati- the oldest known species of Goniatites. graphically older species, such as G. hudsoni and G. antiquatus There are no obvious reasons for the gap in the record of the Bisat, 1934, have an external lobe which has half the width of its 358 JOURNAL OF PALEONTOLOGY, V. 79, NO. 2, 2005

FIGURE 3ÐExternal suture lines of species of Goniatites de Haan, 1825. 1, Goniatites hudsoni Bisat, 1934, specimen WMN 11071 from RuÈthen, ϫ3, D ϭ 30 mm, from Korn, 1990. 2, Goniatites crenistria Phillips, 1836, specimen WMN 10080 from Herdringen, ϫ4, W ϭ 22.0 mm, from Korn, 1988. 3, Goniatites ®mbriatus (Foord and Crick, 1897), specimen WMN 11063 from Nehden, ϫ4, D ϭ 23 mm, from Korn, 1990. 4, Goniatites spirifer Roemer, 1850, specimen WMN 11071 from Scharfenberg, ϫ3.5, D ϭ 27 mm, from Korn, 1990. 5, Progoniatites maghribensis Korn et al., 2003, holotype GPIT 1875±78 from Taouz, ϫ6, D ϭ 15 mm, from Korn et al., 2003. 6, Goniatites lazarus n. sp., holotype GPIT 1851±97 from Erfoud, ϫ2, D ϭ 36 mm, W ϭ 27 mm. 7, Goniatites lazarus n. sp., paratype MB.C.5307 from Erfoud, ϫ2, D ϭ 42 mm, W ϭ 32 mm. depth, and the median saddle has a value of 0.35 of the external varies between species within these three genera; it may be either lobe depth. In the stratigraphically younger species, such as G. acute or narrowly rounded. ®mbriatus and G. spirifer Roemer, 1850, these ratios are 0.60 and 0.45, respectively (Fig. 5). This trend towards wider external PALEOBIOGEOGRAPHY OF ENTOGONITES AND GONIATITES lobes and higher median saddles is a feature of subsequent evo- Mississippian ammonoid faunas demonstrate increasing provin- lution within the Goniatitidae (Korn, 1997). cialism during the younger part of the subsystem. As Korn et al. (2002, 2003) demonstrated, Middle Tournaisian and early Late DESCENDANTS OF GONIATITES Tournaisian faunas from Morocco closely resemble their time There are no intermediate forms known which connect Gon- equivalents from other regions such as the western United States, iatites with their stratigraphically younger descendants such as south and central Europe, the Urals, and Central Asia. In contrast Arnsbergites Korn, 1988, Paraglyphioceras BruÈning, 1923, and to this, late ViseÂan and Serpukhovian faunas display striking pro- Hibernicoceras Moore and Hodson, 1958. These younger descen- vincialism (Korn, 1997). Korn et al. (1999) distinguished four dants differ from Goniatites in their evolute inner whorls, their paleogeographic realms, the Subvariscan, Laurentian, North wider external lobe, and their higher median saddle. Genera with Gondwanan, and Kazakhian. completely involute species are only Goniatitella Korn, 1988 Goniatite faunas of Late Tournaisian and Late ViseÂan age are (with Y-shaped external lobe and well-rounded ventrolateral sad- widely distributed and diverse. Early and Middle ViseÂan sedi- dle; Korn, 1988) and Hypergoniatites Ruzhencev and Bogoslov- mentary rocks, however, have yielded only sparse ammonoid fau- skaya, 1970 (with rapidly expanding whorls and thus a much nas, and very few localities are known (Riley, 1996). Thus, the higher aperture than in Goniatites; Ruzhencev and Bogoslov- exact time in which ammonoid cosmopolitism turned into provin- skaya, 1971). cialism remains unknown. More or less direct descendants of Goniatites are the genera However, the record of Entogonites in Morocco provides evi- Arnsbergites, Paraglyphioceras, and Lusitanoceras Pereira de dence of continuing ammonoid cosmopolitism at least until the Sousa, 1923, which belong to three independent evolutionary lin- end of the Middle ViseÂan. Morphologically very similar species eages (Korn, 1997). All have wider external lobes than Goniatites of the genus have been recorded from very distant places in Alas- and higher median saddles. The form of the ventrolateral saddle ka, Utah, central and southeastern Europe, and North Africa. This KORN ET AL.ÐGONIATITIDAE AND ENTOGONITIDAE 359

FIGURE 5ÐPlot of sutural measurements, showing the ontogenetic de- velopment and species differences in the height of the median saddle (ratio of the total depth of the external lobe).

1960; cf. Librovitch, 1957; McCaleb, 1968; Ruzhencev and Ga- nelin, 1971). Some of these (Soliclymenia, Diaboloceras, Paral- egoceras Hyatt, 1884) have ribbed shells, which resemble Ento- gonites. The functional properties of tetrangular or triangular FIGURE 4ÐCharacter matrix demonstrating the mosaic pattern in the dis- coiling is not yet known. tribution of the most important characters of species of Goniatites. The body chamber length and orientation of the apertural mar- Abbreviations: EL, external lobe; MS, median saddle of external lobe; gin of the living animal can be calculated from the whorl expan- VLS, ventrolateral saddle; nr, narrowly rounded; ac, acute. Data source: sion rate, which describes the opening rate of the whorl spiral G. americanus, Gordon (1957); G. multiliratus, Gordon (1962); G. (Saunders and Shapiro, 1986; Okamoto, 1996; Klug, 2001). Using hudsoni, Korn (1990); G. antiquatus, Bisat (1934); G. crenistria, Korn this calculation, Entogonites with a whorl expansion rate of 1.60 (1988); G. ®mbriatus, Korn (1988); G. spirifer, Korn (1990); G. sphaericus, Korn (1988); G. crenifalcatus, Bogoslovskaya (1966); G. had an almost horizontally orientated aperture (Fig. 7). With such shimanskyi, Bogoslovskaya (1966); G. stenumbilicatus, Kullmann an orientation, the minute Entogonites belongs to the ammonoids (1961); G. olysya, Korn in Skompski et al. (2001). with a planktonic lifestyle. The wide paleogeographic distribution of the genus, which was probably caused by the mid-ViseÂan trans- gression, supports this interpretation. shows that at this time interval the formation of barriers by the SYSTEMATIC PALEONTOLOGY Variscan Orogeny was not completed, and populations on the Family GONIATITIDAE de Haan, 1825 shelves of northwestern Laurentia, the northern and southern Var- Genus GONIATITES de Haan, 1825 iscides, and North Gondwana were in communication (Fig. 6). Goniatites DE HAAN, 1825, p. 39. Goniatites is a globally distributed genus, but it is not clear if Glyphioceras HYATT, 1884, p. 328. this wide geographic range occurred at the time of the stratigraph- Goniatites DE HAAN, 1825. RUZHENCEV AND BOGOSLOVSKAYA, 1971, p. ically oldest species of the genus. According to current knowl- 207 (see for more complete synonymy). edge, Goniatites is represented by endemic species in the various Goniatites DE HAAN, 1825. KORN, 1988, p. 81. regions. No central European species, for instance, are recorded from regions outside the northern Variscides. An explanation for Type species.Conchiliolithus Nautilites (sphaericus) Martin, this cosmopolitism with numerous very similar species of Gon- 1809 (nom. nud.) ϭ Ammonites sphaericus Sowerby, 1814, p. 116 iatites in the various regions can be seen in the ViseÂan transgres- (Opinion 420 ICZN, 1956). sion (Ross and Ross, 1987) that may have enabled the dispersal Diagnosis.Goniatitidae with moderately large, thickly dis- of ammonoids. coidal to globular conch. Aperture and whorl expansion rate low This communication was interrupted during the late ViseÂan. to moderate (WER 1.45 to 2.00). Suture line with narrow, V- Faunas of this time span are especially well known from the Sub- shaped or Y-shaped external lobe and moderately high median variscan realm. Only periodically, after major eustatic transgres- saddle. Ventrolateral saddle asymmetric, narrowly rounded or sions, can similar faunas be found globally (Korn, 1997). The late acute. Large, V-shaped adventive lobe. Ornament with strongly ViseÂan was therefore the time in which the major Carboniferous crenulated growth lines which run in convex or biconvex course; ammonoid provinces were separated. some species with ®ne spiral ornament. Discussion.For the most recent revisions of the genus see Korn (1988). RECONSTRUCTION OF THE LIVING ENTOGONITES SAHARENSIS N. SP. Species of Entogonites are characterized by their small size GONIATITES LAZARUS new species (maximum of 20 mm conch diameter). They can be regarded as Figures 3.6, 3.7, 8.1, 8.2, 8.4, 8.5, 9.3 micromorphs and display super®cial resemblance to some Late Diagnosis.Goniatites with pachyconic conch at 40 mm dm Devonian ammonoids. The most conspicuous character of Ento- (ww/dm 0.70) and thickly discoidal conch at 70 mm diameter gonites is the tetrangular coiling of the juvenile whorls, which is (ww/dm 0.55). Umbilicus almost closed (uw/dm ϭ 0.03) in all unique among Paleozoic ammonoids. Triangularly coiled ammo- growth stages. Low aperture, moderate whorl expansion rate noids are more frequent. They occur in the latest Devonian (So- (1.95). Suture line with V-shaped external lobe with slightly sin- liclymenia Schindewolf, 1937 and wocklumeriids, cf. Schinde- uous ¯anks, moderately high median saddle (one-third of the sym- wolf, 1937; Korn, 1995) and in the middle Pennsylvanian metric, narrowly rounded ventrolateral saddle). Shell ornament (Diaboloceras Miller and Furnish, 1940; Yakutoceras Popov, with crenulated growth lines with convex course. 360 JOURNAL OF PALEONTOLOGY, V. 79, NO. 2, 2005

FIGURE 6ÐPaleogeographic map for the North Atlantic region during the Tournaisian (after Scotese, 1997; image by R. Blakey, Flagstaff, Arizona), showing the distribution of the genera Entogonites Kittl, 1904b and Goniatites. [AK±Alaska; YU±Yukon; UT±Utah; NV±Nevada; OK±Oklahoma; AR±Arkansas; SP±South Portugal; IR±Ireland; BE±Belgium; RH±Rhenish Massif and Harz Mountains; GB±England; MS±Moravia and Silesia; HC±Holy Cross Mountains; SU±South Urals; NU±North Urals; CM±Cantabrian Mountains; AA±Anti-Atlas; BO±Bosnia].

Description.As typical for many goniatite species, the whorl MB.C.5307 (Fig. 3.7). At 42 mm conch diameter, the sutural el- width/conch diameter ratio becomes lower during ontogeny. At ements are narrower and more elongate than in the holotype. The 35 mm conch diameter, the holotype has a pachyconic conch (Fig. external lobe width is only 0.53, and the median saddle has a 8.1, 8.2), and paratype MB.C.5308 is, at 70 mm conch diameter, height of 0.34. The ¯anks of the ventral lobe are slightly sinuous, thickly discoidal. In all stages, the venter is broadly rounded and and the ventrolateral saddle is well rounded. is thickest near the almost completely closed umbilicus. Etymology.The species is named after the biblical Lazarus The ornament of the three specimens consists of ®ne, crenu- (who rose from the dead), and the Lazarus Effect in the fossil lated growth lines. These have a low and wide projection on the record, because of the reappearance of the family Goniatitidae ¯anks and a wide and shallow external sinus (Fig. 9.3). The ho- with its possibly oldest species Goniatites lazarus after a long gap lotype shows the suture line at 36 mm conch diameter (Fig. 3.6). in the fossil record. In this stage, the V-shaped external lobe has a width of 0.64 of Types.Holotype GPIT 1851±97 (Fig. 8.1, 8.2); and two para- its height (measured at one-half the depth of the lobe) and the types, MB.C.5307 and MB.C. 5308. The three specimens repre- median saddle has a height of 0.34 of the external lobe depth. sent growth stages between 35 and 70 mm diameter. The ventrolateral saddle is almost symmetric with slightly sinuous Occurrence.Twelve km southeast of the Dar Kaoua Oasis, ¯anks, and its top is narrowly rounded. The adventive lobe is V- 32 km southeast of Erfoud, eastern Anti±Atlas, Morocco; surface shaped and almost symmetric; it is wider than the ventrolateral collected material most probably of early Late ViseÂan age (B1 saddle. A different suture line can be seen in the paratype Zone or earliest B2 Zone of Riley, 1990). KORN ET AL.ÐGONIATITIDAE AND ENTOGONITIDAE 361

FIGURE 7ÐReconstruction of the living Entogonites saharensis n. sp. Upper left, original size; lower right, ϫ5.

Discussion.Goniatites lazarus shows similarities to G. cren- Pericyclus nasutus Schmidt, 1941. This species was originally istria Phillips, 1836, but the latter species has a wider umbilicus described from specimens found in the Harz Mountains (Schmidt, (uw/dm Ͼ 0.12 at dm 60 mm), which is almost closed in G. 1941; Weyer, 1972) and was later reported from the Rhenish Mas- lazarus. The course of the growth lines provides additional criteria sif (Nicolaus, 1963; Korn, 1988) and Upper Silesia (Bojkowski, for separation of the two species: in G. crenistria, the growth lines 1979). are biconvex with distinctive ventrolateral projection, whereas in Entogonites borealis Gordon, 1957. Described from the Brooks G. lazarus their course is largely convex with barely visible pro- Range of Alaska (Gordon, 1957) and later reported from Utah jections (Fig. 9). Goniatites antiquatus has a similar conch, but (Gordon, 1971; Titus and Riley, 1997). A questionable record of its external lobe has a narrower base than in G. lazarus. The this species was published from Ireland (Hodson, 1958). suture line of G. lazarus shows slightly sinuous ¯anks of the Entogonites saharensis n. sp. Described herein from the eastern external lobe, which are almost straight in G. crenistria and G. Anti±Atlas of Morocco. antiquatus. Diagnosis.Entogonitidae with small, discoidal conch. Aper- Another species without spiral ornament is G. hudsoni, but this ture and whorl expansion rate low (WER 1.60). Inner whorls taxon has a globular conch. G. hudsoni has slightly sinuous ¯anks tetrangularly coiled, adult whorls spirally coiled. Ornament with of the external lobe, but has an acute ventrolateral saddle. The dichotomizing riblets which run with biconvex course and form conch form, growth line course, and suture line of G. americanus a prominent ventrolateral projection and a moderately deep ex- is closest to G. lazarus. Goniatites americanus also has a very ternal sinus. narrow umbilicus and a narrowly rounded ventrolateral saddle. Discussion.For the last revision of the genus see Korn The main difference between the two species is that G. ameri- (1988). Entogonites is one of the most enigmatic Mississippian canus bears spiral lines which are absent in G. lazarus. ammonoid genera. All species of this genus have diminutive Family ENTOGONITIDAE Ruzhencev and Bogoslovskaya, 1971 conchs (maximally 20 mm conch diameter) and show an outstand- Genus ENTOGONITES Kittl, 1904b ing morphology with tetrangularly coiled inner whorls, fastigate ribs, and a more or less striking ventrolateral projection of the Tetragonites KITTL, 1904a, p. 677. aperture. Entogonites KITTL, 1904b, p. 322. The phylogenetic origin of Entogonites is not yet solved. It has Entogonites KITTL, 1904b. KORN, 1988, p. 46. been shown in several reports (e.g., Nicolaus, 1963; Korn, 1988) Type species.Tetragonites Grimmeri Kittl, 1904a, p. 677. that Entogonites occurs in the upper part of the Mississippian Included species.Tetragonites Grimmeri Kittl, 1904a. The cherty series of the Rhenish Massif. Only a few sections yielded species was originally described from specimens found near Sa- both E. nasutus and E. grimmeri in ascending order, and the oc- rajewo in Bosnia (Kittl, 1904a, 1904b) and was later reported currences of the two species do not overlap. Apart from Nomis- from the Rhenish Massif (Schmidt, 1925; Nicolaus, 1963; Korn, moceras vittiger (Phillips, 1836), which is common in these beds, 1988, 1990), North Moravia (Patteisky, 1930), Upper Silesia (Ko- other goniatites are very rare. rejwo and Teller, 1968), Cornwall (Butcher and Hodson, 1960), Entogonites grimmeri occurs rarely in the uppermost 3 m of Devon (Riley in Jackson, 1991), Lancashire (Calver and Rams- the Kieselkalk Formation. The species became extinct immedi- bottom, 1961), and Utah (Titus and Riley, 1997). ately after a mass occurrence in the so-called Grimmeri Bed. This 362 JOURNAL OF PALEONTOLOGY, V. 79, NO. 2, 2005

FIGURE 8ÐGoniatites lazarus n. sp. and Entogonites saharensis n. sp. from the eastern Anti±Atlas of Morocco. 1, 2, Goniatites lazarus n. sp., lateral and dorsal views of the holotype, GPIT 1851±97, ϫ1.5. 3, Prolecanites sp. and a paratype of Entogonites saharensis n. sp., MB.C.5303, ϫ1.25. 4, 5, Goniatites lazarus n. sp., ventral and lateral views of the paratype, MB.C.5307, ϫ1. 6, Close-up of part of the body chamber of the same specimen with two paratypes of Entogonites saharensis n. sp. (arrows pointing at specimens) and a disarticulated trilobite identi®ed as Archegonus sp., ϫ2. 7, 8, Entogonites saharensis n. sp., lateral and dorsal views of the holotype, MB.C.5301, ϫ5. 9, Entogonites saharensis n. sp., lateral and dorsal views of a paratype, MB.C.5304, ϫ10. 10, Entogonites saharensis n. sp., lateral and dorsal views of a paratype, MB.C.5305, ϫ10. 11, 12, Entogonites saharensis n. sp., lateral and dorsal views of a paratype, MB.C.5302, ϫ10.

TABLE 1ÐConch dimensions (mm) and proportions of Goniatites lazarus n. sp. from Dar Kaoua.

Specimen D W H U A WER W/D W/H U/D Holotype GPIT 1851±97 38.6 27.0 19.8 1.2 8.9 1.95 0.70 1.36 0.03 Paratype MB.C.5308 69.6 38.6 37.8 2.2 Ð Ð 0.55 1.02 0.03 Paratype MB.C.5307 46.5 31.8 25.3 1.5 Ð Ð 0.68 1.27 0.03 KORN ET AL.ÐGONIATITIDAE AND ENTOGONITIDAE 363

TABLE 2ÐConch dimensions (mm) and proportions of Entogonites saharensis n. sp. from Dar Kaoua.

Specimen D W H U A WER W/D W/H U/D Holotype MB.C.5301 9.35 3.05 2.65 4.55 2.05 1.64 0.33 1.15 0.49 7.30 2.65 2.10 3.55 Ð Ð 0.36 1.26 0.49 Paratype MB.C.5303 11.20 Ð 2.90 5.40 ÐÐÐÐ0.48 Paratype MB.C.5306 7.60 2.80 2.20 3.40 Ð Ð 0.37 1.27 0.45 Paratype MB.C.5304 4.55 1.70 1.15 2.40 0.95 1.60 0.37 1.48 0.53 Paratype MB.C.5305 2.45 Ð 0.70 1.25 ÐÐÐÐ0.51 Paratype MB.C.5302 2.20 1.15 0.70 1.05 0.45 1.58 0.52 1.64 0.48 is an index horizon of 3 cm thickness which could be recognized characteristic ornament. These riblets extend transversely over the in most sections of the Rhenish Massif (Nicolaus, 1963) and the ¯anks and dichotomize in the ventrolateral area where they are Harz Mountains. It is a dark-gray cherty laminated and burrow- bent forward to form a low salient. They extend almost trans- mottled shale, in which E. grimmeri and accompanying goniatites versely over the venter. Constrictions were not seen in this spec- are crushed. At some localities, E. grimmeri occurs in extremely imen. large numbers with rare accompanying benthic organisms such as The third ontogenetic stage is seen in the holotype (Fig. 8.7, chonetid brachiopods, trilobites, and crinoids. Neither the ances- 8.8). It begins at 3.5 mm conch diameter and is again regularly tors nor the descendants of Entogonites are known. coiled. The relative width of the umbilicus is only slightly re- In most of the occurrences, Entogonites is rare or represented duced, and the whorl cross section is oval and slightly depressed. by few specimens. This is in contrast to the wide geographic At 9 mm conch diameter, most of the riblets dichotomize ventro- distribution; as Figure 6 demonstrates, Entogonites is reported laterally, with nondichotomizing, intercalated, or trichotomizing from practically all the major paleogeographic realms. riblets occurring rarely. Their projection is still rather low, and a shallow external sinus is formed. On the last whorl, the ribs be- ENTOGONITES SAHARENSIS new species come narrower and sharper: up to 6 mm diameter, they are wider Figure 8.3, 8.6±8.12 than their interspaces, but at larger diameters, they are the same Diagnosis.Entogonites with wide umbilicus (uw/dm 0.50). width or less. Constrictions are absent. Third to seventh whorls strictly tetrangularly coiled. Forty round- Paratype MB.C.5303 is the largest specimen with almost 14 ed riblets per whorl that dichotomize ventrolaterally. Ventrolateral mm conch diameter (Fig. 8.3). The last portion of the whorl is projection of the riblets low. partly obscured by siliceous matrix, but half of the whorl is ex- Description.Paratype MB.C.5302 (Fig. 8.11, 8.12) is the cellently preserved. The ornament is principally the same as in smallest specimen (2.2 mm conch diameter). Its whorl outline is the holotype, usually with dichotomizing ribs, which form a mod- subquadrate with widely rounded corners, but the umbilicus of erately high ventrolateral salient. The ribs are almost as wide as the last preserved whorl is almost square-shaped. Except for weak their interspaces. umbilical riblets, no distinct ornament is preserved in the stage A complete suture line could not be seen in the material. Only smaller than 1.5 mm. From the beginning of their appearance, the fragments are visible in the holotype. riblets tend to dichotomize in the mid¯ank area, but there are also Etymology.The species is named after the Sahara Desert, in simple ribs. These riblets form a low ventrolateral projection and which the specimens were collected. extend nearly transversely across the venter. At 2.2 mm diameter, Types.Holotype MB.C.5301; and ®ve paratypes, the ribs are particularly strong near the umbilicus and become MB.C.5302-MB.C.5306 (Fig. 8.7, 8.8). weaker after their split in the middle of the ¯ank. Shallow con- Occurrence.Twelve km southeast of the Dar Kaoua Oasis, strictions occur at intervals of 90 degrees. 32 km southeast of Erfoud, eastern Anti±Atlas, Morocco; surface

Paratype MB.C.5305 (Fig. 8.10) has a conch diameter of ap- collected material most probably of early Late ViseÂan age (B1 proximately 2.5 mm with four whorls and is the specimen that Zone or earliest B2 Zone of Riley, 1990). The specimens come best displays the early ontogeny. The inner two whorls are ser- from two different lithologies: 1) from sideritic lumachels com- penticonic, spirally coiled, and smooth. In the next stage, from posed of productid brachiopods, bryozoan colonies, rugose corals, the third whorl on, the umbilicus is strictly tetrangular. The last and ammonoids (Prolecanites sp. and Beyrichoceras sp.); and 2) preserved volution has a quadrate outline. Forty riblets form the from body chambers of single larger goniatites (Goniatites lazarus n. sp., Beyrichoceras sp.), in which minute specimens of various ammonoids are assembled. All growth stages up to 13 mm conch diameter are represented by well-preserved material. Discussion.Entogonites grimmeri (Kittl, 1904a) has the same conch dimensions and ratios as Entogonites saharensis, but pos- sesses sharper riblets which in juveniles form a strikingly tongue- shaped ventrolateral projection. Entogonites nasutus (Schmidt, 1941) also has a rather low ventrolateral projection of the riblets, but displays irregular splitting of the riblets. Entogonites nasutus and E. borealis Gordon, 1957 both have narrower umbilici (uw/ dm 0.35) than E. saharensis (uw/dm 0.50).

FIGURE 9ÐDiagrams showing the growth-line course of species of Gon- ACKNOWLEDGMENTS iatites, ϫ2. 1, Goniatites crenistria, specimen WMN 10080 from Her- dringen (from Korn, 1988), D ϭ 39.6 mm, W ϭ 25.4 mm. 2, G. This study is mainly based on material discovered by M. crenistria, holotype BM NH c282 from Bolland, D ϭ 36.8 mm, W ϭ M'Barak (Erfoud) and collected by Mr. Bruno Fecte. We are also 24.2 mm. 3, G. lazarus n. sp., holotype GPIT 1851±97 from Erfoud, indebted to W. Gerber (TuÈbingen) for producing the digital im- D ϭ 36 mm, W ϭ 27 mm. ages, and E. Bickford as well as J. Clark (TuÈbingen, Seattle) for 364 JOURNAL OF PALEONTOLOGY, V. 79, NO. 2, 2005 assistance during the production of the manuscript. Finally, we KOREJWO, K., AND L. TELLER. 1968. Stratigra®a karbonu z wiercen Mar- thank N. Riley (Nottingham), A. Titus (Kanab), D. Work (Au- sowice 1 i Koniusza 1 (niecka miechowska). 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