Late Givetian Ammonoids from Hassi Nebech (Tafilalt Basin, Anti-Atlas, Southern Morocco)
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Fossil Record 16 (1) 2013, 5–65 / DOI 10.1002/mmng.201300001 Late Givetian ammonoids from Hassi Nebech (Tafilalt Basin, Anti-Atlas, southern Morocco) Jrgen Bockwinkel1, R. Thomas Becker*,2 and y Volker Ebbighausen3 1 Dechant-Fein-Str. 22, 51375 Leverkusen, Germany. E-mail: [email protected] 2 Institut fr Geologie und Palontologie, WWU Mnster, Corrensstr. 24, 48149 Mnster, Germany. E-mail: [email protected] 3 deceased on 3rd June 2011 Abstract Received 7 January 2012 The Hassi Nebech area of the SE Tafilalt (Tafilalt Basin, Anti-Atlas, Morocco) yielded Accepted 3 September 2012 the richest and most diverse late Givetian ammonoid fauna on a global scale. Above the Published 20 February 2013 distinctive regional “Lower Marker Bed” (Synpharciceras clavilobum Zone), abundant loosely collected limonitic specimens derive from hypoxic shales of the Taouzites taou- zensis to Petteroceras errans zones. The ontogenetic morphometry and intraspecific variability of a total of 30 species representing five families, the Acanthoclymeniidae, Taouzitidae, Pharciceratidae, Petteroceratidae, and Tornoceratidae, are documented. New taxa are: Pseudoprobeloceras praecox n. sp., Scaturites minutus n. gen. n. sp., Darkao- ceras velox n. sp., Pharciceras decoratum n. sp., Ph. fornix n. sp., Ph. subconstans n. sp., Ph. involutum n. sp., Lunupharciceras incisum n. sp., Transpharciceras procedens n. gen. n. sp., Stenopharciceras progressum n. sp., Pluripharciceras n. gen. (type species: Syn- pharciceras plurilobatum Petter, 1959), Plu. orbis n. sp., Synpharciceras frequens n. sp., Lobotornoceras bensaidi n. sp., Nebechoceras eccentricum n. gen. n. sp., and Phoenixites lenticulus n. sp.. The documentation of conch and particularly suture ontogeny and in- traspecific variability necessitates a revised diagnosis for ten taxa. Manticoceras ponti- Key Words formis Termier & Termier, 1950, Probeloceras costulatum Petter, 1959, and Pseudopro- beloceras nebechense Bensad, 1974 are regarded as subjective junior synonyms of Ps. Devonian pernai (Wedekind, 1918). Sandbergeroceras acutum Termier & Termier, 1950 is a sub- Ammonoidea jective synonym of Taouzites taouzensis (Termier & Termier, 1950). Pharciceras appla- Ontogeny natum Bensad, 1974 is transferred to Extropharciceras. Other forms (Ph.aff.tridens, Systematics Ph. cf. subconstans n. sp., Extropharciceras n. sp. 2, Ex. cf. arenicum, Ex. cf. applana- Biostratigraphy tum, Synpharciceras sp., Plu. cf. plurilobatum) are described in open nomenclature. Additional supporting information may be found in the online version of this article at the publisher’s web-site Introduction Moroccan pharciceratid faunas (Bockwinkel et al. 2009), the eastern Anti-Atlas is the best region on a The Devonian succession of the eastern Anti-Atlas (Ta- global scale to investigate such assemblages, based both filalt and Maider) of southern Morocco has been cele- on the shear number of available, well-preserved speci- brated in numerous publications for its open marine mens, and on the globally highest beta (regional) diver- faunas, notably for its ammonoids. Such a study is of sity. This earlier study dealt with the fauna from the particular interest, because the late Givetian was a very “Lower Marker Bed” of Dar Kaoua, which is continued peculiar time in ammonoid evolution (e.g., House here by a detailed description of the limonitic fauna 1985) because of the rapid complication of septa in se- from overlying shales of the famous Hassi Nebech re- parate lineages of the distinctive families Taouzitidae, gion in the more basinal setting of the south-eastern Pharciceratidae, and Petteroceratidae. As outlined in Tafilalt. More than 1,800 specimens have been investi- our first contribution on the revision and description of gated, which fall in 30 species. For comparison, there * Corresponding author # 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 6 Bockwinkel, J. et al.: Late Givetian ammonoids from Morocco Figure 1. Global distribution of Late Givetian ammonoids. 1 ¼ NW Territorries, 2 ¼ Kentucky, 3 ¼ New York State, 4 ¼ Rhenish Massive, 5 ¼ Harz Mountains, 6 ¼ Sudetes, 7 ¼ Cantabrian Mountains, 8 ¼ Westiberian Chains (Celtiberia), 9 ¼ Pyrenees, 10 ¼ Montagne Noire, 11 ¼ Graz Palaeozoic, 12 ¼ eastern Dra Valley, 13 ¼ Maider, 14 ¼ Tafilalt, 15 ¼ Ben Zireg region, 16 ¼ Ougarta, 17 ¼ Saoura Valley, 18 ¼ Ahnet, 19 ¼ Rudny Altai, 20 ¼ Semipalatinsk region, eastern Kazakhstan, 21 ¼ Guangxi, South China. J. ¼ Japan, KO. ¼ Kolyma, N. EUR. ¼ northern Europe, N. AM. ¼ North America, S. AM. ¼ South America, S. EUR. ¼ southern Europe, N. CH. ¼ North China, KAZ. ¼ Kazakhstan, TM. ¼ Tarim Basin, TB. ¼ Tibet, S. CH. ¼ South China, IC. ¼ Indochine, B. ¼ Burma, MA. ¼ Malyasia, AUST. ¼ Australia, NZ. ¼ New Zealand, MAD. ¼ Madagascar. Plate tectonic re- construction altered from Heckel & Witzke (1979), preferred to other Devonian world reconstructions because of the placing of Asian plates. are currently only ca. 20 named species for all of the foud region by Termier (1929) and Clariond (1934), it late Givetian of the Rhenish Massive, the region with is the first North African locality from which a late Gi- the next highest documented diversity. vetian goniatite was illustrated (Synpharciceras n. sp. For a brief review of the palaeogeographic distribution aff. clavilobus in Schindewolf 1940, here included in (Fig. 1) of pharciceratid faunas and of previous reports Syn. clavilobum). Based on the Marcais and Clariond from the Anti-Atlas, the reader is referred to Bockwinkel Collection, Termier & Termier (1950) briefly described et al. (2009). The late Givetian ammonoid zonation and from the same series of outcrops, but then named Oued conodont correlation within the Tafilalt region was sum- Kseir (which lies to the East) and Tazoult Nehra (a marized by Becker & House (2000a, 2000b) and Aboussa- marker hill to the North), the following six species: lam & Becker (2007). The applied zonal key for correla- Koenenites lamellosus (= Mzerrebites sp. and Darkao- tion, with MD ¼ Middle Devonian and UD ¼ Upper ceras velox n. sp.) Devonian, is also shown in the concise geological time Pharciceras taouzensis (placed in Taouzites by Korn scale of IUGS (Ogg et al. 2008). The late Givetian succes- 2001; partly including Synpharciceras plurilobatum) sion of the Tafilalt consists of the following ammonoid Pharciceras tridens (partly including an Extropharci- succession: MD III-B ¼ Mzerrebites erraticus Zone; MD ceras) III-C ¼ Synpharciceras clavilobum Zone; MD III-D Pharciceras tafilense (= Synpharciceras frequens n. sp.) ¼ Taouzites taouzensis Zone; MD III-E ¼ Petteroceras Pharciceras kseirense (placed in Stenopharciceras by errans Zone. Montesinos & Henn 1986) Pharciceras lunulicosta (? = Synpharciceras frequens Locality and Stratigraphy n. sp.) Bensad (1974) added 11 species from the main shale The Hassi Nebech area in the south-eastern Tafilalt levels of the same locality. (Fig. 2) exposes an Early to Late Devonian succession in an elongated, ca. WNW-ESE striking band of low Tornoceras simplex (= probably Nebechoceras eccentri- outcrop for several kilometres, starting ca. 19 km east- cum n. gen. n. sp.) northeast from Taouz. Following early records of phar- Tornoceras frechi (= partly Lobotornoceras bensaidi ciceratids in rather generalized faunal lists for the Er- n. sp.) museum-fossilrecord.wiley-vch.de # 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Fossil Record 16 (1) 2013, 5–65 7 Figure 2. Location of the Hassi Ne- bech area in the SE Tafilalt (modified from Kaufmann 1998). Pharciceras cf. meridionale (= Darkaoceras velox 305601900, W 0034700400), just 50 m east of Section 1a, n. sp.) has been investigated in detail by Aboussalam (2003) Pharciceras applanatum (here re-assigned to Extrophar- and does not reach the main pharciceratid levels. Nodu- ciceras) lar limestones at its top gently dip to the South and fall Pharciceras cf. applanatum (= Pharciceras fornix in the basal late Givetian Mzerrebites erraticus Zone n. sp.) (hermanni and cristatus ectypus conodont zones). Higher Pharciceras n. sp. (e.p. ¼ Stenopharciceras kseirense) strata are covered by soil. Synpharciceras clavilobum (= Syn. clavilobum, Syn. fre- Section 2 is the succession that first was studied by quens n. sp., and Syn.aff.frequens n. sp.) Bensad (1974) and Bensad et al. (1985). It lies ca. Synpharciceras aff. clavilobum (= Synpharciceras fre- 2 km east of Section 1b, at N 305600400, W 0034600300, quens n. sp.) and exposes middle Givetian argillaceous beds with Beloceras ? disciforme (placed in Meropharciceras by maenioceratids to Middle Frasnian nodular limestones Becker & House 1993) with Sandbergeroceras and Naplesites, followed by Me- Petteroceras errans sobeloceras, early Beloceras and Carinoceras. As out- Petteroceras n. sp. (= Pett. errans) lined in Bensad et al. (1985), the sedimentary sequence Pseudoprobeloceras nebechense (= Pseudoprobeloceras indicates deeper deposition than in the Givetian/Fras- pernai and Ps. praecox n. sp.) nian boundary section in the central Tafilalt. This is consistent with assignment of the Hassi Nebech region Three Givetian-Frasnian sections have been measured to a Tafilalt Basin by Wendt et al. (1984) and Wendt since 1997, numbered 1a, 1b, and 2 (Becker & House (1988). Bensad et al. (1985) proposed that Section 2 field numbering, see Aboussalam 2003). Details of could become the type-section of a formally defined Section 1a have not yet been published but topmost Pharciceras Stage but the local conodont record is poor Middle Givetian nodular