Lapworthella vandali n. sp. from the Lower-Middle Cambrian ...

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Lower-Middle Cambrian boundary interval of Morocco ... stones in the lower Middle Cambrian (Tissafinian Stage) of the Anti-Atlas, Morocco The new spccies is ...

First African lapworthellid:

Lapworthella vandali n. sp. from the

Lower-Middle Cambrian boundary interval of Morocco

ED LANDING, GERD GEYER & WOLFRAM HELDMAIER

LANDING, E., GEYER, G. & HELDMAIER, W. 1995. first African lapworthcllid: Lapworthella vandali n. sp. from the Lower-Middle Cam­ brian boundary interval of Morocco. - Bcringeria Spccial issue 2: 243-253, 3 text-figs., I pI.; WUrzburg. Abstract. Lapworthella vandali n. sp. is known from exceptionally large, nodose. slender sclerites reeovercd from thin shell-hash lime­ stones in the lower Middle Cambrian (Tissafinian Stage) of the Anti-Atlas, Morocco The new spccies is the largest known lapworthellid and is the first described lapworthellid from African and the western Gondwana in general. A second, informally descrihed species comes from coeval strata of the Anti-Atlas. • Tommotiida, Lapworthellidae, Lapworthella vandali n sp., systematics, Middle Cambrian, Morocco .

Zusammenfllssung. Lapworthella vandali n. sp. ist durch ungew()hnlieh gro~e, nodose und schlanke Sklcrite aus dOnncn Schillkalk­ Lagen aus dem unteren Mittelkambrium (Tissafin-Stufe) des marokkanischen Anti-Atlas reprasentiert. Die neue Art ist dcr gri:l~te Uber­ haupt bekannte Lapworthellide. Sie ist zugleieh die erste Lapworthelliden-Art, die aus Alrika und der westlichen Gondwana-Region besehrieben wird. Eine zweite, informell besehriebene Art stammt aus zeitl!quivalenten Schichten des Anti-Atlas . • Tommotiida, Lapworthellidae, Lapworthella vandali n sp., Systematik, Millelkambrium, Marokko .

Author's addresses: ED LANDING, New York State Geological Survey, The State Education Department, Albany, New York 12230, U.S.A .; GERD GEYER and WOLFRAM HELDMAIER, Institut I1Jr Palaontologie, l3ayrisehe JuliuS-Maximilians-Universitat, Pleieherwall I, D­ 97070 WUrzburg, Gennany.

Introduction Events in the Cambrian evolutionary radiation before

Lapworthellids were geographically widespread in

the appearance of the oldest trilobites included: 1) di­

the

Lower-Middle

Cambrian.

More

than

twenty

versification of Phanerozoic-aspect trace producers in

species have been described from the warm water

the earliest Cambrian and 2) the subsequent origin of

sequences of Laurentia (LOCHMAN, 1956; LANDING,

diverse metazoans with mineralized hard parts (e.g.,

1984; CONWAY MORRIS & FRITZ 1984), Australasia

LANDING 1994). Lapworthellids are a very early ap­

(CHEN & ZHANG 1980; YIN et aI., 1982; JIANG in LuO

pearing group of systematically problematical, skele­

et aI., 1982; DUAN, 1984; Q1AN & YIN, 1984; WANG et

talized organisms (LANDING et aI., 1989). They are

aI., 1984; QIAN & BENGTSON, 1989; CONWAY MORRIS

known from highly variable, cone-like, commonly

& CllEN , 1990; BENGTSON et aI., 1990; WANG, 1994),

transversely ridged, hollow, phosphatic sclerites that

and Siberia (MISSARZII EVSK Y,

1969;

MESHKOV A,

may have radial costae and transverse septa. Ontoge­

1969; MESHKOV A et aI., 1974; MAITIIEWS & MIS­

netically

lapworthellid sclerites are known

SARZHEVSKY, 1975; V ASIL'EVA, 1994) and from the

(LANDING, 1984; HINZ, 1987). This suggests that many

cool water sequences of Avalon (COBBOLD, 192 I;

sclerites were present on the outer surface of lap­

MAHH[WS,

worthellids and apparently formed a protective, spiny

BENGTSON & FLETCHER, 1983; LANDING , \988; LAN­

integuement on th is group of heavi Iy armored , benthic

DING & MURPHY, 1991) and Baltica (WIMAN, 1903;

organisms (BENGTSON, 1977; LANDING, 1984).

POULSEN , 1942; BENGTSON, 1980; BERG-MADSEN,

fused

1973; LANDING et aI., 1980, \989;

E.

244

LANDING, G. GEYER

1981; HINZ, 1987). This report describes the excep­ tionally large sclerites of a new lapworthellid that is the first-known species of the family from the African margin of the Gondwanan continent. Evaluation of the new species has led to a reexamination of the criteria used to differentiate the sclerites of lapworthellids. The classic trilobite and archaeocyathan biostrati­ graphy of the Cambrian of Morocco (e.g., HUPE, 1953;

& W.

IIELDMAIER

DEBRENNE, 1964) has been supplemented by recent work on small shelly fossils from the Atlas and Anti­ Atlas Mountains (e.g., GEYER, 1986). This activity has featured acetic and formic acid disaggregation of lime­ stone samples from the Lower and Middle Cambrian. In the course of this work, numerous sclerites of a new lapworthellid have been recovered.

Localities, depositional setting, and age Lower-Middle Cambrian strata unconformably overlie late Precambrian metamorphic, volcanoclastic, and intrusive rocks of the Jbel Sarhro massif (see DES­ TOMOES et aI., 1985: Fig. 32) The lapworthellids of this report were recovered at the Jbel Arhouri, Tizi n'Telgane, and Ikkis localities on the eastern and northern margins of the Jbel Sarhro (Fig. 1). Cambrian sections in this part of the Jbel Sarhro are either similar to those in the central High Atlas range if the deposits of the lower Middle Cambrian Jbel Wawrmast Forma­ tion, or Tissafinian Stage of GEYER (I 990a), uncon­ formably overlie the upper Precambrian, and the

4

I :.

,'"

I

~B'LE" !\

. r,!.

'!

Lower Cambrian is not present, or the Jbel Wawrmast Formation (see DESTOMBES et aI., 1985; GEYER, 1989; GEYER & LANDING, this volume) rests unconformably on slightly older, upper Lower Cambrian or even lower Middle Cambrian strata. This situation reflects the paleogeographic situation at the northern rim of the Souss basin, where the eastern High Atlas regions formed a topographic high during deposition of the Lower Cambrian sediments. The Jbel Wawrmast Formation is generally a mono­ tonous sequence of greenish or, more rarely, bluish­ geen, fine-grained sandstones. The lower part of the

' . \ I

!

Marrakech

Taroudannt

Agadir

.. Zagora

,

­

Bou Rbia

'"

o

, ' ,' ,

I

100 km

'

Fig 1. Generalized map of the lligh Atlas and Anti-Alias region s. Morocco, showing lajlwolihdlid localities at Ikkis, .lbel Arhouri, Tizi n'Tclgane, and BOll Rbia . Areas with Neoproterol.Oic(,!)-Cambrian rock s den sely stipjlled, areas jln;sumcd or known to include NcoproterozoicO)-Cambrian rocks marked by small stipples, and outcrojls or older Neoproterolo ic rock and clystalline basement marked by pattern orsmnll crosses.

24 5

Firs! African lapworthcllid

At Tizi n'Telgane, several overlapping sections were measured above the upper Lower Cambrian Tazlaft Formation (Fig. 2). Above a thin basal cong lomerate, the TNTE-ll section has an extraordinarily thick (ca. 4 m) echinodeml-trilobite-grainstone with many inter­ calated stromatolitic crusts and rare LLH-type stro­ matolites, which includes sample horizon TNTE-II­ 6.35 and which is overlain by a I m-thick nodular, stromatolitic limestone. Sclerites of Lapworthella vandali n. sp. were recov­ ered from a trilobite hash-dominated, 6 em-thick, "Micmacca breccia" limestone that lies 27.9 m above the base of the Jbel Arhouri section (sample JAR-26.4; 200 g disaggregated, about 80 sclerites recovered). Further lithologic and paleontologic details of this hor­ izon are described in the field guide for MOROCCO '95 (GEYER et aI. , this volume) . A much larger number of lapworthellid sclerites were recovered at section II of the Tizi n'Telgane lo­ cality (sample TNTE-I1-6.35; 8 kg, about 280 sclerites recovered). Sample TNTE-1I-6.35 came from a 40 em thick, stromatolitic packstone with planar stromatolitic laminae every 1-2 cm and an interval of low (5 em)

Jbel Wawrmast Formation has lithologically variable, brownish, reddish, or green; winnowed to arenaceous; and nodular to bedded limestone with abundant trilo­ bite and echinoderm hash. These limestone beds in the lower part of the Jbel Wawrmast Fomlation have been traditionally known as "Breche a lvficmacca". This lower part of the fOmlation is termed the "Breche a Micmacca Member" (GEYER, 1989), and all of the Lap worthella-bearin g samples were collected from this member. The Jbel Wawrmast Formation at Jbel Arhouri, Tizi n'Telgane, and Bou Rbia represents high energy conditions for basal conglomerates and shell­ hash beds. However, most parts of the formation re­ flect a relatively low energy, shallow, siliciclastic shelf deposition that is succeeded by hummocky cross­ stratified sandstones and fine grained sandstones of the Jbel Afraou Formation (W . HELDMAIER, unpub . data). The greenish, fine-grained sandstone-dominated Jbel Wawrmast Formation nonconformably overlies late Precambrian granitoids at the Jbel Arhouri section (GEYER et aI. , this volume) . The base of the fOmlation is formed by a con glomerate which is directly overlain by stromatol itic Iimestones and shell-hash beds. 30­

II

c:=. =

25 ­

JAR - 26.4

."

20­

9 8

15 ­

I

ISS

ISS

c6

' '

ccM nodules

7

==

II

6

= 10­

5

TNTE II - 6,35

ee G

4



3

"""'­

egl

.Nv...

Qzte

2



~c

n:lc ~~

sll1

211m

sand

2

u

~

gravel

0.2

63

mm

n:lc n:lc n:lc si lt

21'm

sa nd

2

grave l

0.2

63

~

~

mm

Fig. 2. Parti al strati graphic sections at Jbel Arhouri (left) and Tizi n'Tclgane TNTE-ll (right). Scales indicate thicknesses in meters (measured from the base of the Jbel Wawrmast Formation). Abbrevi ation s: ecG: (echinoderm) grainstone with brachi opod shells and trilob it\: sr bites; e\:M: mud ston.;; [,SS : tine-grained sandstone ; Qtze: qu artzites; cgl : conglomerate; wavy raltern : stromatolitic crusts.

11

E. LANDING, G. GEYER & W. IIELDMAlfR

246

SH-V stromatolites in the middle of the bed. No de­ terminable trilobite remains were found in the sample, but the unsoluble residue includes a number of small shelly fossils. A trilobite-rich' limestone sample from the Jbel Wawrmast Formation at "lkkis" yielded a small num­ ber of sclerites of L. vanda/i (5 specimens). This sam­ ple (150 g disaggregated), a partly dolomitized shell bed with large trilobite fragments and brachiopod valves, was collected by 1. HINDERMEYER in 1954 and reported in HUPE's (\959) unpublished dissertation . Nevertheless, the "lkkis" locality (i.e., sample BM I of GEYER, 1990b) is problematical. 1. HINDERMEYER (written commun. to W. HELDMAIER) no longer has in­ formation about the site, while !-IuPE (1959) has noted that "Ikkis" is 40 km east of Boumalne at coordinates "472.5/85.5" (equal to modem Lambert coordinates 472.5/486.5). However, that distance does not match with these coordinates, and no topographic or cultural feature with this name is present at or close to that lo­ cation. Nevertheless, a settlement termed "Ikhis" is lo­ cated some 20 km south of Timatraounine, and the co­ ordinates point to a locality slightly west of the Jbel Arhouri section. The lithologies of HINDERMEYER's Ikkis sample includes pure lumachellic limestones, strongly dolomitized and even silicified rocks. Their variable faunas are dominated by tri lobites and bra­ chiopods. The lapworthellids were dissolved from the lumachellic limestones, which have an unusually highly diverse fauna of well preserved trilobites, inclu­ ding Cepha/opyge, La/ikingaspis, Kingaspidoides, Acanthomicmacca, and "Paradoxides".

Additional lapworthellid sclerites, assigned to Lap­ wor/hella sp. indet. A, were recovered from the Bou Rbia section at the southern flank of the EI Graara massive. The Lapworthella-bearing sample BRB­ 145 .7 represents a 30cm-thick limonitic, lumachellic limestone bed that comes from the lower part of the Breche a Micmacca Member. The available fauna has a rela-tively low diversity and includes only Kingaspi­ do ides, Acanthomicmacca, and "Paradoxides" scler­ ites, hyo-lith conchs, and a few fragments of additional small shelly fossils. The trilobites from the JAR-26.4, TNTE-1I-6.35, Ikkis-BM I, and BRB-145.7 samples all represent the Cepha/opyge no/abilis Zone, the second zone (C2) of GEYER'S (1990a) Tissafinian Stage, or Moroccan lower Middle Cambrian. The Cepha/opyge no/abilis Zone is limited to the lower part of the Jbel Wawrmast Forma­ tion (and the partly coeval Tamanart Formation) at all localities in southern Morocco (GEYER, 1990b), and this means that the sample from Ikkis also came from this part of the formation . No international agreement exists on definition and global correlation of the Lower-Middle Cambrian boundary. For this reason, the Cepha/opyge nOlabilis Zone can be regarded as falling in the lower part of the Moroccan Middle Cambrian but is the probable equiv­ alent of the uppermost Lower Cambrian of Avalonian and Baltic sections (GEYER, 1990a, \990c). It hence correlates most probably not only with part of the "Proto/enus limestone" but possibly also with the overlying Lapwor/hella limestone of Comley (GEYER, 1990c).

Systematic paleontology Order Tommoti ida MISSARZIIEVSKY 1970 (1969) emend. LANDING 1984 Family Lapworthellidae MISSARZHEVSKY 1966 emend. LANDING 1984 Lapworthella COBBOLD 1921 emend. LANDING 1984

Type species: Lapworlhel/a nigra C01380LD 1921 0 cornu WIMAN 1903).

=

Slenolheca

Lapworlhella vanda/i n. Sp. Figs 3A-G, PI. I, fi gs 1-17

Etymology Named for the Germanic Vandal tribes that crossed from Spain to Morocco and set up a number of north African king­ doms in the flft.h century.

Holotypc: Specimcn in PI. I, fig . 5 (NYSM 15468). - Type locality and stratum: Sample JAR-26.4 at the Jbel Arhouri section in the Jbcl Wawrmast Formation. - Age: Lower Middle Cambrian, lower Tis­ salinian Stage, Cepha/opyge nolabilis Zone. - Material studied: 348 sclerites from the Jbel Arhouri (sample JAR-26.4), Tizi n'Telgane (sample TNTE-II-6.35), and Ikkis (sample BM I) localities. Diagnosis: Lapworthella species with very large (up to ca. 4 mm), straight to recurved and slightly helicoid, elongate and gently tapering (apical angle 6-15°, rarely 20°), transversely ridged (2 .9-5 .7 ridges/mm) sclerites with variable cross-sections, radially to apically in­ cI ined rounded nodes or large spines on transverse

ridges. Description: Aperturally and apically broken speci­ mens reach a length of 3.72 mm (PI. I, fig. I). This suggests that unbroken sclerites reached at least 4.0

First African lapworthcllid

mm. The sclerites are slender, with apical angles of the broadest surfaces ranging from 9° (PI. I, fig. 6) to 15° (PI. I, fig. I). The widest element recovered in this study has an apical angle of 20° (PI. I, fig. 7). Lateral profi les range from straight (PI. I, figs. 7, 11-13) to gently curved and recurved (PI. I, figs. 1-6, 9, 10, 14-17), with or without a slight torsion (PI. I, figs . 3,6, 10). Cross sections of the elements may be circular (PI. I, fig. 8) and range from weakly to strongly com­ pressed ellipses to quadrate, rhomboid, and rounded­ triangular (Fig. 3A-G). Major transverse ridges that are normal to oblique to the growth axis characterize the sclerites (e.g. , PI. I, figs. 2, 7, II, 13 , 14 vs. PI. I. figs. 4, 5,10,14). These ridges may be gently flexed apically on the broader faces of the sclerites (PI. I, fig. 16). The spacing of the major ridges ranges from 2.9/mm (PI. I, fig. 2) to 5.7/mm (PI. I, fig. 6). Fine transverse growth lines form a rare surficial ornament on the inter-ridge areas (PI. I, fig. 16).

c

c

-----=> 0

~F f'ig 3. Apcrtural cross sections of Lapwonhel/a vandali n. sp. scicrilcs. magnifications arc approximate. A, Paratypc NYSM 15464, x 22 (sec PI. I, Ilg. I) ; [3, Paralypc NYSM 15479, x 22 (PI. I, "g . 16)~ C, Paratype NYSM 15469, x 22 (PI. I , fig. 6); D, Paralype NYSM 15470, x 31 (PI. I, fig . 7); E, Paratype NYSM 15476, x 22 (PI. I, "g. 13); f', Paratype NYSM 15480, x 37 (PI. I, IIg. 17)~ G, Paratypc NYSM 15478, x 22 (PI. I, lig. 15). Radially to apically inclined nodes (e.g., PI. I, figs . 2, 4, 6, IS, 16) occur on the major ridges of the scle­ rites . Well preserved sclerites show that these nodes can have the form of relatively large spines (PI. I, figs. 8, 9) that can reach 0.24 mm in length (PI. I, fig. 5, ridges 4-7 from aperture). These nodes and spines are obscured in elements that were abraded before final burial (PI. I, fig. 7). The node spacing ranges from 10/mm (PI. I, fig. 4, ridge closest to aperture) to 21.5/mm (PI. I, fig. 2, second ridge above aperture).

247

Comparison and discussion: Western workers have ap­ preciated the high degree of ontogenetic variability in the sclerites of lapworthellid species since MAlTIIEWS' (1973) illustration of the variation in one Avalonian form. Speci,es differentiation is problematical in this tommotiid family, and illustration of a relatively large number of sclerites is required to understand the scle­ rotome of single species (e.g., CONWAY MORRIS in BENGTSON et aI., 1990: 122). Sclerite variability has led to contrasting taxonomic practices. LANDING (1984) agreed with BENGTSON (1977) that variation in shape (curvature and cross section) does not provide a way to differentiate species but questioned BENGTSON's use of the density of structural elements (node and ridge spacing) as spe­ cies-specific characters. These considerations led HINZ (1987) to propose that most named lapworthellid spe­ cies are synonyms and based on sclerites derived from a variable sclerotome. A number of nodose lapworthellid species (i.e., forms with sclerites with radially or apically pointing nodes on the transverse ridges) have been named from the trilobite-bearing, upper Lower Cambrian and Lower-Middle Cambrian boundary interval. Two Australian species (in BENGTSON et a!. 1990) have the "unique features" suggested by LANDING (1984) for confident differentiation and differ from the Moroccan sclerites of this report. Lapworthella Jasciculata CON­ WA YMORRIS & BENGTSON (in BENGTSON et aI., 1990) has radial interridge fascicu lae that extend onto the ridges to produce a nodose appearance, and the stubby sclerites of L. puttapensis BENGTSON & CONWAY MORRIS J 990 have closely spaced nodes that produce a tuberculate appearance on the wide ridges. Illustrated L. Jasciculala and L. pullapensis sclerites are much smaller (0.5-0.6 mm) than the Moroccan specimens. Four lapworthellid "species" named by POULSEN (1942) on the basis of differences in the cross sections of single scJerites from the island of Bornholm, Swe­ den (i.e., L. bornholmensis, L. cobboldi, L. quadran­ gularis, and L. subtriangularis), are all synonymous (BERG-MADSEN, 1981). Lapworthella bornholmensis sclerites differ from the Moroccan specimens by having: 1) an ornament similar to L. jasciculata (CONW AY MORRIS in BENGTSON et aI., 1990), 2) higher apical angles (20-32°; POULSEN, 1942), and 3) a seemingly smaller size (up to J.33 mm; POUI.SEN,

1942). Lapworthella cornu (WIMAN, 1903) from Sweden , L. schodackensis (LacHMAN, 1956) from eastern New York State, and L. dentata MISSARZIIEVSKY, 1969

24R

E. LANDI NG, G. GEY ER & W. HELDMAlrR

from Siberia have nodose sclerites that do not have "unique" structural features appropriate to a species­ level differentiation (LANDING, 1984). The most thor­ ough biometrical documentation has been done on large collections of L. schodackensis sclerites. Size (up to 1.6 mm), ridge spacing (14-50/mm), and node spacing (35-144/mm) of L. schodackensis sclerites (LANDING, 1984) overlap Siberian L. denlala sclerites (see BENGTSON, 1980), and L. schodackensis is re­ garded as the senior synonym (LANDING, 1984; CON­ WA y MORRIS in BENGTSON et a!., 1990). Lapworlhella schodackensis sclerites are much smaller, have much denser ridge and node spacings, and can have greater apical angles (40-50°; LANDING, 1984: Text-fig. 2G & 2M) than the Moroccan sclerites. Lapworlhe//a cornu remains poorly understood . BENGTSON'S (1980) ill ustrat ions and measurements of the holotype and a second specimen indicate a species with sclerites simi lar to those in the Moroccan collec­ tions. The Swedish sclerites are slender and relatively large (at least 2.12 mm) and have a node spacing (12­ 16/mm) that overlaps the Moroccan specimens. How­ ever, the ridge spacing in the two sclerites of L. cornu illustrated by BENGTSON (1977) is 7-7.6/mm, a density never approached in the Moroccan collections and about twice the mean ridge spacing measured in 35 specimens (3.6/mm). if BENGTSON (1980) is correct in synonymizing the English Avalonian sclerites brought to L. dentala by MATTIIEWS (1973) with L. cornu, this would mean that L. cornu sclerites have apical angles that reach 60° (e.g ., MATTIIEWS: PI. 8, fig. 8), and its sclerotome had much broader sclerites than those in the Moroccan collections. BENGTSON (1980) noted the presence of densely spaced minor growth lines between the ridges in L. cornu and MATrIlEWS' (1973) specimens; these minor lines are rarely present in the Moroccan specimens. Similarly, the large spine-like nodes present in the Moroccan specimens do not seem to appear in the Swedish and English sclerites. Denticulate sclerites from the trilobite-bearing Lower Cambrian (Branchian Series) of Avalonian England were illustrated by MATTIIEWS (1973) as Lapworlhe//a denlala and were left in open nomen­ clature as Lapworlhella by HINl (1987) . MA1l'IIEWS' (1973) and HINZ' (1987) material was recovered from a stratigraphic interval (Slrenuella through Lapworlhe//a Limestones) that includes the topotype horizon from

which COBBOLD (1921) described the genotype species L. nigra. MATI'IIEWS (1973) concluded that his nodose specimens were not conspecific with L. nigra; he noted that COBBOLD'S (1921) spartan description and illus­ tration (six figures) of the limited type collection did not indicate the presence of nodes. However, pre-burial abrasion by wave and current transport obliterates these nodes (e.g., HINZ, 1987), and their absence in COBBOLD's (1921) type collection does not preclude a synonymy with L. nigra. The size (up to 3 mm), apical angle (13-41°), and ridge spacing (6-9/ mm) in COB­ BOLD's (1921) illustrated specimens overlap MAT­ TIIEW'S (1973) and HINl' (1987) material, and syn­ onymy is likely. The larger apical angle (up to 60°; e.g., MATrHEWS, 1973: PI. 8, fig. 8) and denser ridge spacing (5.2-11.8/mm; MATI'HEWS, 1973 : 144) in the Engl ish specimens di ffer from the Moroccan sclerites .

Lapworlhella sp. indet. A Material studied : About 40 fragmentary scicritcs from section Bou Rbia, sample 13RB-1457 .

Description: The sclerites are preserved as fragmen­ tary, limonitic encrustations, which do not permit recogn ition of morphologic detai Is . The sclerites are slender, with straight to gently curved lateral profiles. Cross sections of the elements of the elements are usually subrectagular to rhomboid with well-rounded corners. Transverse ridges are very prominent and form a conspicuous ornament, whereas growth. Iines and nodes are not recognizable . Although the preservation certainly obscures growth lines, it is unlikely that large nodes were originally present and abraded before burial. Comparison and discussion: The species is represented by a number of fragmentary sclerites, which generally suffered considerable deformation and are imperfectly preserved so that a precise description and determina­ tion is not possible. However, they represent a species that differs confidently from Lapworlhe//a vandali n. sp. in having comparatively coarse and prominent transverse ridges, probably without larger nodes. Further investigations will target additional, better preserved material to reveal morphological details that may sufficiently characterize the species.

rirst Ali-ican lapworthellid

249

Conclusions Over 400 lapworthellid sclerites have been recovered

very slender and particularly large elements with

from the lower lbel Wawrmast Formation of southern

widely spaced ridges and development of sharp, large,

Morocco. The sclerites from the lbel Sarhro and Jbel

spine-like nodes. The wide geographic distribution of

Ougnate areas are regarded as representing a new no­

nodose lapworthellids in the late Early Cambrian and

dose lapworthellid, Lapworlhella vandali n. sp. The

Lower-Middle Cambrian boundary interval is regarded

number of structural features that can be compared in

as having lead to the development of endemic popula­

nodose lapworthellid sclerites is limited to variations

tions and species of nodose lapworthellids.

in shape and density of such structural elements as

An additional species from the EI Graara region,

ridge and node spacing and has led to proposals that all

central Anti-Atlas, is represented by only imperfectly

of these nodose sclerites belong to one species. The

preserved sclerites and awaits further investigation for

relatively large collection of sclerites from the Jbel

precise description.

Sarhro-lbel Ougnate indicate a sclerotome featuring

Acknowledgments E. LANDING gratefully acknowledges support from

sciences, University of WUrzburg, and financial sup­

National Science Foundation grant EAR94-15773, G .

port for field work from the Deutsche Forschungsge­

GEYER a Heisenberg grant and . financial support of

meinschaft (DFG).

field work by the Deutsche Forschungsgemeinschaft

Illustrated

specimens

are

reposited

tn

Paleontology Collection of the New

Graduiertenkolleg

Museum (NYSM), Albany. R. H. FAKUNDINY and W.

"Geowissenschaftliche

Gemein­

schaftsforschung in Afrika" from the Faculty of Geo­

York

the

(DFG). W. HELDMAIER acknowledges a grant of the

State

M. KELLY provided reviews of the manuscript.

References OENGTSON, S. 1977. Aspects of problematic fossils in the Early Palaeozoic . - Acta Univ . Upsaliensis, Abstr. Uppsala' Diss. rac . Sci . 415: 71 p.,9 figs .; Uppsala.

Mountains, northwestern British Columbia, Canada, with comments on possible levels of competition in the Early Cambrian. - Pall1onl. Z. 58 (3/4): 197-209, 3 figs .; Stullgart.

BENGTSON, S. 1980. Redescription of the Lower Cambrian Lap­ warlheffa cornu . - Geo!. F()ren . Stockholm F()rhand!. 102: 53-55,2 figs., I tab., Stockholm.

DEllItENNE, F. 1964. Archaeocyatha. Contribution a I'etude des faunes cambriennes du Maroc, de SaJ'daigne et de France. " Notes Mem . Servo geo!. Maroc 179: 371 p, 52 pIs .; Rabat.

BENGTSON, S., CONWAY MORRIS , S., COOPER, B. J., JELL, P A. & RUNNEGAR, B. N. 1990. Early Cambrian fossils from South Australia. - Assoc. Australasian I'alaeontols, Mem. 9: 364 p., 218 figs ., I tab; Brisbane.

DESTOMBES, J., HOllARD, H. & WlllEFERT, S. 1985. Lower Palaeo­ zoic Rocks of Morocco. - In : HOllAND, C. H. (ed.). Lower Palaeozoic Rocks of the World . Vo!. 4. Lower Palaeozoic of north-wcstern and west-central Africa: 91-336, 68 figs .; Chichester, New York, Brisbane, Toronto, Singapore (John Wiley & Sons)

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Lower Cambrian se diment

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