an african twin to the brazilian calamopleurus (actinopterygii: amiidae)

Zoological Journal of the Linnean Society (1998), 123: 179–195. With 8 figures

Article ID: zj980134

An African twin to the Brazilian Calamopleurus(Actinopterygii: Amiidae)

PETER L. FOREY

Department of Palaeontology, The Natural History Museum, Cromwell Road,London SW7 5BD

LANCE GRANDE

Department of Geology, Field Museum of Natural History, Roosevelt Road at Lake Shore Drive,Chicago, Illinois 60605, U.S.A.

Received October 1997; accepted for publication February 1998

A new species of amiid fish, Calamopleurus africanus sp. nov., is described on the basisof fragmentary material from ?Albian Kem Kem beds of southern Morocco. The new speciesshows several derived characters of the genus Calamopleurus such as ossified dermopteroticribs, an inferred loose association between the dermosphenotic and the skull roof, a gularplate with a scalloped posterior margin, and a hyomandibular with a very long posterior(opercular) process. It differs from the type species in the proportions of the frontals,supramaxilla and gular. The distribution of Calamopleurus and some other Lower Cretaceousfishes is discussed in the context of the presumed adjacency of west Africa and eastern Brazilduring much of the Mesozoic.

1997 The Linnean Society of London

ADDITIONAL KEY WORDS:—Calamopleurini – vicariant patterns – South America(eastern Brazil) – Africa (Morocco).

CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . 179Geographical and geological setting . . . . . . . . . . . . . . . 180Abbreviations . . . . . . . . . . . . . . . . . . . . . . 181Systematic palaeontology . . . . . . . . . . . . . . . . . . 182

Calamopleurus africanus sp. nov. . . . . . . . . . . . . . 182Discussion . . . . . . . . . . . . . . . . . . . . . . . 192Acknowledgements . . . . . . . . . . . . . . . . . . . . 194References . . . . . . . . . . . . . . . . . . . . . . . 194

INTRODUCTION

In recent years a variety of fossils have been recovered from the ?Lower Cretaceous(?Albian) of southern Morocco around the oases of Taouz and Erfoud. Although

1790024–4082/98/060179+17 $30.00/0 1998 The Linnean Society of London

P. L. FOREY AND L. GRANDE180

A

B

40 m

carbonate

marls andsandstones

cross beddedsandstones

ferruginoussandstones

sandstones

cross beddedsandstones

conglomerates unconformity

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Calcaire

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Libya

Taouz

Algeria

Mauritania

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Wes

tern

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Figure 1. A, type locality of Calamopleurus africanus sp. nov. The holotype was not found in situand the locality may only be identified as the Taouz area. B, section through the Kem Kem bedsunderlying the carbonate escarpment. The holotype almost certainly came from the ferruginoussandstones. Section from Russell (1996) after Joly (1962).

Cretaceous fossils from these localities have been known for many years (Lavocat,1949; Tabaste, 1963; Taquet, 1976) it is only within the last few years that moreintensive collecting has yielded a diverse and interesting fauna of fishes and tetrapods(Wenz, 1981; Russell, 1996; Sereno et al., 1996; Forey, in press a) which have provento hold significance for both stratigraphic correlation within Africa as well asconfirmation of the historical biogeographic link between South America and Africaat the dawn of the opening of the south Atlantic.

In this paper we describe a new species of Calamopleurus from Morocco, a genusof amiid fishes hitherto known only from two localities in eastern Brazil.

The material described here belongs to: (1) the Department of Palaeontology,The Natural History Museum, London, and specimen numbers have prefix BMNH;(2) the Department of Geology, Field Museum of Natural History, Chicago, andspecimen numbers have prefix FMNH.

GEOGRAPHICAL AND GEOLOGICAL SETTING

The material we describe comes from the Kem Kem area of southern Moroccoclose to the Oasis of Taouz (Fig. 1A). This locality contains sporadic outcrops ofcoarse-grained sandstones which grade upwards into gypsiferous marls, marlycarbonates succeeded by an overlying carbonate escarpment. Although the fossilsdescribed here were not found in situ it is clear from the attached matrix that theycome from the sandstones and probably from the ferruginous sandstones which liemidway up the section (Fig. 1B). In older literature (Lavocat, 1954; Joly, 1962;

AN AFRICAN TWIN TO THE BRAZILIAN CALAMOPLEURUS 181

Tabaste, 1963) the sandstones were simply referred to as Continental Intercalairebut are now known as the Kem Kem beds (Sereno et al., 1996). The Kem Kembeds attain a maximum depth of 200m and lie unconformably on Ordovician andDevonian rocks, but they are conformable with the overlying carbonates. At thebase of the carbonate sequence the ammonite Neolobites vibrayeanus dates this part ofthe sequence at the lower part of the Upper Cenomanian (96 million years). Thissets an upper age limit for the underlying Kem Kem beds. More precise dating canonly be done on the vertebrates contained within the Kem Kem beds. Sereno et al.(1996) mentioned the occurrence of nine species of sharks recognized on isolatedteeth. Some of these have been found in the Bahariya Formation of western Egypt,dated as Lower Cenomanian (Dominik & Schaal, 1984; Werner, 1989). Russell(1996) suggests an Albian age for the Kem Kem beds based on the dinosaursCarcharodontosaurus saharicus (Deperet & Savornin) which is also known from theAptian of Timimoun, Algeria, and Rebbachiasaurus garasbae Lavocat also known fromthe Albian of Tunisia. Of course, dating using only vertebrate fossils is usually ratherimprecise and somewhat circular in reasoning (e.g. eventually, the reason so manyRebbachiasaurus garasbae are from ‘Albian’ deposits is that when we find them, we usethem to date the deposits as Albian). Also, the Kem Kem beds, which may reachup to 200m in thickness, may range in age throughout Lower Cretaceous to UpperCenomanian. The Kem Kem beds are generally assumed to be freshwater (Russell,1996) but detailed palaeontological and sedimentological work remains to be done.

ABBREVIATIONS

Abbreviations and choice of anatomical terminology follow Grande & Bemis(1998).

ang angularao antorbitalarh articulatory head of hyomandibula

(covered with cartilage in life)arp ascending ramus of parasphenoidbo basioccipitalbtt displaced broken tooth tipcha anterior ceratohyalco coronoidd dentarydpt dermopteroticdpta thin laminar part of dermopterotic

overlapped by frontaldptr dermopterotic rib (thought to be

ossified tendons)epo epioccipitales extrascapularexo exoccipitalfm foramen magnumfnb foramen for orbital arteryfnvf foramen for vagus nervefr frontalfrc opening in frontal to supraorbital

canalfsal lateral foramen for the occipital artery

g gulargrpal groove for reception of palategx various branchial arch elementsh hyomandibulahmf foramen for hyomandibular trunkhp posterior process of hyomandibula for

articulation with opercularic intercalarl lachrymal (infraorbital 1)mcr median crest of gularmx maxillan nasalnf neural facet (articulatory area for

neural arch)oc occipital condyleodsp overlap surface on frontal for

dermosphenoticof olfactory recesspa parietalpar prearticularpas parasphenoidpaspr posterior process of parasphenoid

(posterior ‘wing’)pastp parasphenoid tooth patchpmx premaxilla


po1 postinfraorbital 1 (ventralpostinfraorbital)

po2 postinfraorbital 2 (dorsalpostinfraorbital)

ptf posttemporal fossaq quadrateroc rostral ossiclesmx supramaxilla

so subinfraorbitalsspo sphenoticsr sclerotic ringsu supraorbitalsuo supraoticts tooth socketvo vomervot vomerine teeth

SYSTEMATIC PALAEONTOLOGY

Subclass Actinopterygii Cope 1887Infraclass Actinopteri Cope 1872Series Neopterygii Regan 1923

Division Halecostomi Regan 1925Subdivision Halecomorphi Cope 1872

Order Amiiformes Hay 1929Family Amiidae Bonaparte 1838

Subfamily Vidalamiinae Grande & Bemis 1998Tribe Calamopleurini Grande & Bemis 1998

Genus Calamopleurus Agassiz 1841

Calamopleurus africanus sp. nov.(Figs 2–5, 6A, 6B, 7B, C)

Diagnosis. A species of Calamopleurus that differs from C. cylindricus in the followingfeatures. (a) Gular much narrower, with a maximum width equal to 30% of thelength (versus 60% of the length in C. cylindricus). (b) Posterior margin of gularbearing 10 small projections (versus 20 or more in C. cylindricus). (c) Gular bearinga small median crest on its ventral surface (absent in C. cylindricus). (d) Supramaxillarelatively long, equal to about 60% of the toothed length of the maxilla (versus 50%in C. cylindricus). (e) Frontal relatively narrow, with the maximum width equal to25% of the length (versus a width/length ratio of 30–33% for C. cylindricus).

Holotype. BMNH P.64809, a crushed head from the Kem Kem beds, ?Albian, Taouz,southeastern Morocco.

Referred material. BMNH P.64810, an isolated occiput, and BMNH P.64811, afragment of a right dentary. There are some morphological differences between theocciput and the holotype, but the differences may simply be ontogenetic. This needsto be verified with additional material.

Etymology: africanus, after the type locality.

Remarks. The new species is known only from skull elements and therefore cannotbe differentiated from Calamopleurus mawsoni (Woodward), Neocomian, Brazil. Thelatter species is known by a single specimen showing postcranial elements (Grande& Bemis, 1998: 443–447). Another probable close relative, Maliamia gigas Patterson& Longbottom, Eocene, Mali, is a monotypic calamopleurin genus known only bya few skull fragments (Grande & Bemis, 1998: 447–449). Differentiation of Maliamia


from Calamopleurus is based on the number of premaxillary teeth. Maliamia has 8,and Calamopleurus has five or six (Grande & Bemis, 1998). Maliamia is a problematictaxon because most of the bones containing the diagnostic features of Calamopleurusare yet unknown (i.e. not preserved) in Maliamia. More precise identification anddifferential diagnosis of Maliamia must await the discovery of better material.

Description. The holotype is a three-dimensional but distorted and crushed head inwhich much of the left lower part of the head has been pushed to the right. Theleft premaxilla has been rotated and pushed up beneath the vomerine region, andmany of the dermal bones of the left side have been lost as have the parietals inthe skull roof. All bones of the opercular series are missing. However, four of thesynapomorphies of Calamopleurus can be clearly seen (see Grande & Bemis, 1998,for a full list). There are long ossified ‘ribs’ attached to the dermoterotic, a gular inwhich the posterior margin is scalloped, an inferred loosely attached dermosphenoticand a hyomandibula with a very long opercular process. All four are described indetail below. Also, tooth patterns on the cornoids and vomer are diagnostic ofCalamopleurini (sensu Grande & Bemis, 1998: 405, characters C, D).

All specimens are preserved in a coarse-grained, deep red ferruginous sandstonein which the sand grains, although rounded, are of very different sizes implyingdeposition in a high energy environment. Preparation was done with a needle whicheasily removed the loosely consolidated matrix. The bone is well preserved butfractured.

The skull in dorsal view (Fig. 2) shows numerous dermal elements and parts ofthe neurocranium. Both parietals are missing exposing the underlying supraoticbone (suo, Fig. 2). Lying posteriorly are isolated elements of the branchial arches.Most of the dermal bones are ornamented with very coarse ridges, grooves andtubercles as in C. cylindricus. Scaling the holotype of C. africanus to the proportionsseen in C. cylindricus, the length of the frontals (45mm) and the lower jaw (80mm)would suggest a fish of about 470mm SL (for comparative measurements of C.cylindricus see Grande & Bemis, 1998, table 110), which is in the lower part of therange for known specimens of C. cylindricus. However, the other fragments (BMNHP.64810 and BMNH P.64811) assigned to this species came from larger fishes.

Both frontals are preserved; the left (fr, Fig. 2) is virtually complete save for theextreme anterior tip while the right lacks the postero-lateral corner and is fractureddue to the mid-line of the skull having caved in. Most of the frontal is heavilyornamented with the centre of radiation lying laterally and above the posterior halfof the orbit. The extreme anterior end is unornamented where it dips down intothe olfactory recess which in life housed the olfactory sac. Laterally, posterior to theorbit, there is another unornamented shelf (odsp, Fig. 2) which lies above thesphenotic (spo). Comparison with C. cylindricus implies that the dermosphenotic (notseen in the specimen) was loosely associated with the skull roof, and this is a derivedfeature of the genus (in other amiids it is firmly sutured to the skull roof ). A finalfeature of the frontal may be noted. There is a descending lamina from the undersideof the frontal which forms part of the interorbital wall. A similar development isseen in C. cylindricus, but poor preservation of many amiids in this region does notallow us to specify the generality of this feature.

Above the orbit and lateral to the frontal of the right side there is a double seriesof supraorbitals (su, Fig. 2). Within the inner series, which abuts the frontal, thereare two supraorbitals, the posterior of which shows canal openings from an anterior


B

A

Figure 2. Calamopleurus africanus sp. nov. The holotype (BMNH P.64809) in right dorsolateralview, with anterior facing right. The full extent of the brachial arches is not shown. Various boneslater prepared out of this specimen are illustrated in Figs 3–6. A, photograph; B, line drawing of A.Scale bars=2cm.

spur of the infraorbital canal. The anterior inner supraorbital is substantially largerthan the posterior. In C. cylindricus there may be two or three—and the numbermay vary from side to side of the same individual (Grande & Bemis, 1998: fig. 297).One small outer supraorbital can be seen lying lateral to the anterior innersupraorbital. In C. cylindricus there are two or three. The fact that only a single one


is seen in BMNH P. 64809 is probably due to incomplete preservation of theseelements. Supraorbitals are not firmly sutured to the skull roof in amiids (e.g. Grande& Bemis, 1998: 412) and appear to be some of the first elements to have disarticulatedfrom the skull after death.

The right nasal (n, Fig. 2) is preserved nearly in life position immediately anteriorto the frontal and above the posterior end of the premaxilla. As in C. cylindricus it isa small triangular bone carrying the supraorbital canal along the medial border andonly partially covering the olfactory recess. It appears to be relatively larger thanin C. cylindricus. The position of the nasal suggests that it failed to meet its antimere(unlike the adult nasals of most other amiid genera which meet in the mid-line andcompletely cover the olfactory recess).

The premaxilla (pmx, Fig. 2) of the right side is seen in dorsal view although themedial edge has been tipped in towards the mid-line and is incomplete. The olfactoryrecess (of ) is very large and well developed as in other amiids and is separated bya pronounced ridge from the deep notch in the posterior margin of the premaxillawhich receives the head of the maxilla. Lying on this ridge there are fragments oftwo small ossicles. The posterior is probably a fragment of the antorbital (ao) whilethe anterior is a small rostral ossicle (roc) containing a tube which carried the lateralportion of the ethmoid commissure. The oral border of the premaxilla shows socketsor tooth bases for four very large teeth but this is an incomplete count since themedial edge of both premaxillae cannot be seen (C. cylindricus carries five or sixpremaxillary teeth: Grande & Bemis, 1998). Based on the shape of the preservedportion of premaxilla, there were no more than five or six premaxillary teeth in C.africanus.

At the posterior end of the skull the dermopterotics (dpt, Figs 2, 3C, 3D) arepreserved, the right more complete than the left. They are elongate with a sinuoussutural connection to both the frontals and parietals (not preserved). The lateraledge carries the otic division of the cranial lateral line. The posterior edge isdeveloped as an unornamented shelf and the posterolateral corner extends back aslong slender processes called dermopterotic ribs in Grande & Bemis (1998). In C.africanus there are at least seven of these ribs, one of which is branched and thelongest of which is about the same length as the main body of the dermopterotic (dptr,Fig. 3C, D). The presence of these ribs is one of the most obvious synapomorphies ofCalamopleurus where they reach back beneath both the extrascapular and theposttemporal (Grande & Bemis, 1998: fig. 297). The extrascapular (es) is identicalto that of C. cylindricus, but many other amiids have similar-shaped extrascapulars,and we interpret this similarity as having no particular significance.

In dorso-lateral view (Fig. 2) much of the infraorbital series and the jaws may beseen. The infraorbital series contains the large triangular lachrymal (l, infraorbital1) plus three small rectangular subinfraorbitals (so, terminology of Grande & Bemis,1998) which have collapsed into the orbit. The two postinfraorbitals (sensu Grande& Bemis, 1998) are also present but they too have collapsed so that the only partsvisible are the dorsal edge of the ventral postinfraorbital (po1), and the anterioredge of the dorsal postinfraorbital (po2). This means that their complete shapescannot be seen. However, it is obvious that the ventral postorbital is substantiallylonger than the dorsal, as in C. cylindricus but unlike the situation in Amia where thetwo postinfraorbitals are normally of equal size. A small portion of the ossifiedsclerotic ossicle (sr) remains deep within the orbit.

The maxilla (mx, Fig. 2) is identical to that of C. cylindricus, the salient points


D

C

A B

hp

hmf

grpal

arh

Figure 3. Calamopleurus africanus sp. nov. A and B, hyomandibula from right side of holotypein lateral view; anterior facing right; C, demopterotic of the right side removed from holotype (Fig. 2)in dorsal view; D, specimen from C drawn in mesial view. Scale bars=2cm.

being the broad notch developed at the posterior margin (a common feature ofhalecomorph fishes) and the stout head of the maxilla which curves medially; thisis best seen on the broken left maxilla which is exposed in ventral view. There are20 teeth or sockets preserved in the maxilla. Grande & Bemis (1998: table 114)noted that the number of teeth were relatively stable in adult C. cylindricus and thatnumber ranged from 21 to 28, although all but one individual (11 were counted)had 24–28. However, they also noted that the number of maxillary teeth of Amiaincreased with age. Thus, the number of maxillary teeth may be a diagnosticcharacter of the species, but we have not included it in the diagnosis because wecannot be certain this was the maximum count present in C. africanus. The elongate


supramaxilla (smx) is a broad bone posteriorly with a marked anterior taper as inC. cylindricus, but is only loosely attached to the maxilla, as judged by the lack of aclear overlap surface. In C. africanus the supramaxilla is equal to 60% of the lengthof the toothed margin of the maxilla, whereas in C. cylindricus it is equal to onlyabout half of that length.

The lower jaw is poorly preserved. Parts of the right dentary (d), angular (ang),prearticular (par) and coronoid (co) may be seen, but all are broken and thereforetheir shapes are incompletely known. In as much as is visible there are no obviousdifferences from these bones in C. cylindricus. At least 13 tooth sockets are presentbut this is an incomplete count. The teeth in the maxilla, premaxilla and dentaryhave rounded bases, a constricted waist and acrodin caps which are all stronglycarinate (keeled with sharp edges). Carinate acrodin tooth caps, which reach toabout half the total length of the teeth (e.g. Grande & Bemis, 1998: fig. 286F) isone of several characters thought to be diagnostic of Vidalamiinae (sensu Grande &Bemis, 1998), although this feature also occurs convergently in other non-amiidgroups (e.g. Caturidae) and possibly in some species of Amiopsis. The coronoids (co,Figs 2, 5C, 5D) clearly have only a single row of teeth (Fig. 5C, D), which is aderived character diagnostic of Calamopleurini (sensu Grande & Bemis, 1998). Amiidsother than members of the tribe Calamopleurini have multiple rows of teeth on thecoronoids.

The gular (g, Fig. 6A, B) is fractured and incomplete on the left side but itsmargin can easily be restored, based on what is preserved, to show both similaritiesand differences with that of C. cylindricus. The gular is triangular with the apex nearthe mandibular symphysis. The posterior edge is scalloped which is a synapomorphywith C. cylindricus. There are marked differences in the relative size and proportionsof the gular between C. africanus and C. cylindricus (Fig. 6). In the former the gularplate is narrow and elongate, well over half the length of the lower jaw (even thoughthat length must be estimated) and the gular is 2.4 times as long as wide. It alsobears a small but distinct median crest (mcr, Fig. 6B) at the anterior end. In C.cylindricus the length of the gular is about half that of the lower jaw (Grande &Bemis, 1988: figs 300, 302), and the bone is only 1.6 times as long as wide andthere is no median crest (Fig. 6 and Grande & Bemis, 1988: fig. 303E).

The parietals are missing on the holotype, providing a clear view of a largesupraotic bone (suo, Fig. 2). This element is a diamond-shaped thick endochondralbone lying in the mid-line beneath the presumed position of the parietals. Grande& Bemis (1998) also found a large supraotic in C. cylindricus and they also recordthe distribution of this bone in other halecomorphs and teleosts. The homology andtaxonomic distribution of the supraotic is at present problematic, mainly becausethree-dimensionally preserved material is needed to verify its presence or absence(Gardiner et al., 1996; Grande & Bemis, 1998). Beneath the supraotic the portionsof the paired exoccipitals can be seen in the holotype which are developed as twosmall processes surrounding the foramen magnum. The basioccipital, which is bestseen in an additional specimen (bo, Fig. 7C) forms the floor of the foramen magnumand is marked by paired neural facets (nf, Fig. 7B) for occipital neural arches (seealso below where a separate occiput is described).

The sphenotic (spo, Fig. 2) of both sides may be seen, the right more completethan the left. One significant feature is that the dorsal surface shows a small patchof ornament-like rugosity as in Amia and various other halecomorphs (Grande &Bemis, 1998). After we photographed and drew the gular on the holotype and only


B

A

vo

ts

pas

pastp

arp

oc

pasprfnb

Figure 4. Calamopleurus africanus sp. nov. Parasphenoid and vomer of holotype (Fig 2) in ventralview, after removal of gular (Fig. 6A). See Fig. 5A, B for details of vomer. Anterior facing left. B is adrawing of A. Gular removed and enlarged in Fig. 6A and B. Scale bars=2cm.

known skull (Fig. 6), we covered it with Carbowax, removed it from the skull, andimbedded it in polyester resin for protection. This enabled us to prepare the specimenfurther to expose the parasphenoid and vomer (Fig. 4). The parasphenoid of C.africanus sp. nov. (pas, Fig. 4) is very similar in shape to that of C. cylindricus, exceptthat it is much narrower (e.g. compare Fig. 4 to Grande & Bemis, 1998: fig. 309).Like the Brazilian species, the new species has elongate posterior processes or ‘wings’of the parasphenoid extending well posterior to the occipital condyle. Althoughthese processes are broken and incomplete in the holotype (paspr, Fig. 4), even theremaining parts extend well posterior to the occiput. The extreme elongation ofthese elements may be another diagnostic character of Calamopleurus or possiblyCalamopleurini, but the condition is unknown in C. mawsoni and Maliamia.

Like all Vidalamiinae (sensu Grande & Bemis, 1998), Calamopleurus africanus sp. nov.has a narrow, weakly developed parasphenoid tooth patch (pastp, Fig. 4). This toothpatch does not extend posterior to the ascending rami of the parasphenoid (unlikein Amiinae where it does extend posterior to the rami; see Grande & Bemis, 1998:fig. 135). The ascending rami (arp, Fig. 4) point lateral and slightly anterior andbear strong grooves distally (spiracular groove). These grooves are also present in


B D

A C

btt

vot

tsts

ts ts

Figure 5. Calamopleurus africanus sp. nov. Bones removed from holotype (Fig. 2). A and B, rightvomer in ventral view, anterior facing left. Removed from ventral side of holotype (Fig. 4). C and D,anterior coronoid in dorsal view, anterior facing left. Scale bars=2mm.

C. cylindricus (although not described in Grande & Bemis, 1998) and many otherhalecomorphs. At the posteroventral proximal end of each ascending ramus thereis a well-developed foramen for the orbital artery (fnb, Fig. 4). The aortic notchdeeply separates the posterior processes of the parasphenoid.

The right vomer is well preserved in the holotype (vo, Figs 4, 5A, 5B), suturedto the anterior end of the parasphenoid. We removed this bone from the parasphenoidfor closer examination. It has a single anterior marginal row of five teeth followedposteriorly by a row of two more teeth nearly perpendicular to the anterior marginalrow (Fig. 5A, B). This is very similar to the pattern in Calamopleurus cylindricus (seeGrande & Bemis, 1998: 426) and Maliamia (Patterson & Longbottom, 1989: 830).This pattern is considered to be a derived character of Calamopleurini (Grande &Bemis, 1998). Some of the vomerine teeth are represented only by tooth sockets (ts,Fig. 5A, B) in the only preserved vomer. The teeth, like those of the maxilla andpremaxilla, are sharply pointed recurved conical teeth with carinate tips.

We also removed part of the palate from the ventral side of the holotype. Itcontains two dermopalatines and the anterior part of the ectopterygoid, all inarticulation. As in C. cylindricus (and almost all amiids), the dermopalatines bear largeteeth, and the ectopterygoid bears smaller teeth that grade into minute teethposteriorly. The teeth of the dermopalatines and anterior ectopterygoid are allcontained in a continuous marginal row, as in C. cylindricus (e.g. see Grande & Bemis,1998: fig. 309).

The hyoid arch is known from the hyomandibula, anterior and posterior cer-atohyal. The hyomandibula (Fig. 3A, B) is particularly distinctive. It is a relativelyflat bone. The fan-shaped head narrows before dividing to a very long opercular


process (hp) which is directed posterodorsally—a synapomorphy of Calamopleurus,and a posteroventral shaft, pierced on the lateral surface by the foramen andassociated groove for the hyomandibula and mandibular branches of the facial nerve(hmf ). The ventral (morphologically anterior) edge of the hyomandibula bears adeep groove (grpal) which must have received the dorsal edge of the metapterygoidregion of the palate (not preserved).

The ceratohyal elements are only preserved on the right side where anterior andposterior elements lie in tandem and are typically amiid in form. The anteriorceratohyal (cha, Fig. 2) is very long, nearly equal in length to the lower jaw. Anteriorlyit is very thick but becomes considerably flattened and blade-like posteriorly. Theposterior ceratohyal is relatively tiny and the sutural surface with the anteriorceratohyal is much shorter implying that there was a considerable mass of cartilagesurrounding the ventral edge of the posterior ceratohyal as in Amia calva.

There are several gill arch elements present in the specimen behind the mainpart of the skull. They are generally elongate which is a feature of Calamopleurus (seeGrande & Bemis, 1998, for discussion of the functional significance). They beardeep branchial grooves on their aboral surfaces, as in the Brazilian species and mostor all other halecomorphs.

A single isolated occipital is assigned to this taxon by virtue of its great similaritywith articulated specimens of C. cylindricus and almost certainly belongs to C. africanussp. nov. This occiput (Fig. 7B, C) comes from an individual larger than the holotypeand consists of epioccipitals, exoccipitals, a partially preserved intercalar of the rightside, basioccipital, parasphenoid and, possibly, a fused first vertebral centrum. Theoccipital region is very long with the exoccipital, basioccipital and parasphenoidreaching well posterior to the level of the epioccipital (Fig. 7C) as in C. cylindricusand Amia (in most amiids the occiput is unknown so there may be no phylogeneticsignificance in this similarity). The epioccipital (epo) meets its partner in the midline,it forms the medial wall of the posttemporal fossa (ptf ) and is tightly sutured withthe exoccipital. As Grande & Bemis (1998) note, the medial suture of the epioccipitalsof C. cylindricus is very different from the condition in Amia where these bones arewell separated by cartilage. In C. cylindricus and Amia the epioccipital is eitherseparated by cartilage from the exoccipital (Fig. 7A) or comes into contact over avery short distance. In C. africanus there is a very tight and interdigitating sutureover the entire epioccipital/exoccipital contact (Fig. 7B). It is possible that thisdifference is ontogenetic rather than taxonomic. We note it here as an observationworth checking in other specimens.

The exoccipital (exo, Fig. 7) is developed similarly to that in C. cylindricus with amedial contact with its antimere above the foramen magnum (fm) and posteriorprocess lateral to the foramen magnum. The posterior edge of each lateral processconsists of unfinished bone, and this suggests that this passed into a cartilage coveredsurface. Furthermore this may have abutted against the anterior edge of a neuralarch, the basal attachment of which may be seen as depressions in the dorsal surfaceof the first fused vertebral centrum.

The basioccipital (bo) is very long and sutured to the exoccipital above throughan interdigitating suture. It is assumed that a vertebral centrum is fused with thebasioccipital posteriorly, forming the occipital condyle (oc, Fig. 7), because there isa pair of depressions which must have received the bases of occipital neural arches(nf ). It should be emphasized that no suture may be seen between the basioccipitaland presumed centrum. The lateral face of the basioccipital (Fig. 7C) is excavated


B

C

A

mcr

Calamopleurus africanus sp. nov.

Calamopleurus cylindricus

Figure 6. Calamopleurus. Gulars in ventral view, anterior facing left. A and B, from C. africanus sp.nov., holotype (Fig. 2). B is drawn from A, restoration of left margin in dashed line. C, C. cylindricus,drawn for comparison from FMNH PF11848. Scale bars=2cm.

as a shallow groove which deepens posteriorly to end immediately in front of aforamen which allowed passage to an occipital artery (fsal).

The intercalar (ic, Fig. 7), which is only partly preserved on the right side, is, asusual in amiids, a substantial bone. In this specimen the large foramen for the vagus


Figure 7. Calamopleurus. Occipital region. A, C. cylindricus, occiput in posterior view, from Grande &Bemis (1998: fig. 303B); B and C, isolated occiput assigned to C. africanus sp. nov.; B, cameralucida drawing of occiput in posterior view (BMNH P.64810). Note the closer union of epiotic andexoccipital in C. africanus sp. nov. than in C. cylindricus. Scale bars=2cm.

nerve (fnvf ) is bordered dorsally by the intercalar and ventrally by the exoccipital,and is completely enclosed by bone. Grande & Bemis (1998: 417) note that thereis variation between individuals of C. cylindricus in the contributions to the borderof this foramen made by the intercalar and exoccipital.

DISCUSSION

This new Moroccan fossil can be unequivocally assigned to the genus Calamopleurusbased on four synapomorphies: the presence of dermopterotic ribs, the elongateopercular process of the hyomandibular, the inferred loose connection between theskull roof and the dermosphenotic and the shape of the gular plate with a fimbriateposterior margin. Also, the arrangement of teeth on the cornonoids in a single row,and the specialised arrangement of teeth on the vomer further assign the species toCalamopleurini. Two further characters may be of relevance: the small nasalsseparated in the mid-line and the posterior extension of the parasphenoid wellposterior to the occiput; but the conditions of these features are poorly known inmany amiids and we are uncertain of the generality of these potential Calamopleuruscharacters. There are two other species of Calamopleurus: the type species from easternBrazil, with which this new species has been compared in the above description,and C. mawsoni Woodward, a species known only by the type specimen from theIlhas Formation (?Neocomian) of Bahia, eastern Brazil. The latter is known onlyfrom postcranial material and therefore cannot be compared to this new species.The only other known member of the tribe Calamopleurini is Maliamia gigas Patterson& Longbottom, a very incompletely known species from the Eocene of Mali, westernAfrica. At present we see no reason to doubt that C. africanus is the sister-species to


Figure 8. Some principal localities of Cretaceous fishes plotted onto a contemporaneous reconstructedpalaeogeographic map: Lower Cretaceous coastline heavy line, present coastline light line. Map basedon the Hauterivian reconstruction of Smith et al. (1994). Deposits (most are areas rather than pointlocalities): 1. Ilhas Formation, Brazil (Neocomian); 2. Cocobeach Series, Rio Muni (Neocomian); 3.Bokungu Series, Congo (Neocomian); 4. Elrhaz Formation, Niger (Aptian); 5. ‘Continental Intercalaire’,Algeria (Aptian); 6. Kem Kem beds, Morocco (?Albian); 7. Santana Formation, Brazil (Apto-Albian);8. Bahariya Formation, Egypt (?Cenomanian).

C. cylindricus, but knowledge of the head of C. mawsoni may necessitate revision ofthis view. In any event the biogeographic implications remain the same: namelythat this new discovery adds cladistic vicariance evidence to the community betweenwest Africa and eastern Brazil in the late Lower Cretaceous.

Other bony fishes known from the Kem Kem beds include a notopterid (Forey,in press a), a semionotid (Lepidotes? sp.) and the coelacanth (Mawsonia). Notopteridswere previously unknown as fossil or Recent taxa from South America, and thesemionotid remains to be described. The Santana Formation of eastern Brazil alsocontains an unusual semionotid, Araripelepidotes temnurus (Agassiz) (see Maisey, 1991;Thies, 1996), but the interrelationships of semionotiform fishes are still too poorlyknown to say if the Moroccan form is more closely related to the Brazilian one thanto species from other areas. Mawsonia is known from the Brazilian Santana Formation(Apto-Albian) and Ilhas Formation (Neocomian) as well as seven sites in the LowerCretaceous of Africa and one from the ?Cenomanian (Fig. 8). The genus Mawsoniais immediately recognisable by the pattern of bones within the postparietal shieldin which the lateral extrascapulars have been incorporated as an extra pair ofroofing bones, the lachrymojugal is long and narrow and reaches well forward intothe ethmoid region, and the bones of the supraorbitotectal series are as broad as


the nasoparietal series. Several African species have been described (Wenz, 1975,1980) but some of these are very poorly diagnosed. At least two are valid (M. lavocatiand M. tegamensis Wenz: see Forey, 1998). M. libyica Weiler from the ?Cenomanianof Egypt is a nomen nudum (all type material has been destroyed: Wenz, 1981). Thesister-group to the genus Mawsonia is Axelrodichthys araripensis known only from theSantana Formation. Despite the interrelationships of the Mawsonia species remainingunknown, the vicariant pattern at the generic level repeats that of Calamopleurus.

Other cladistic vicariant patterns between these two areas which have beendiscussed (Patterson, 1975; Forey, in press b) involve slightly older occurrences. [Thetaxonomy of some of the groups compared by Patterson has since been revised (e.g.his “Urocles” mawsoni is what we refer to here as Calamopleurus mawsoni followingGrande & Bemis, 1998]. A sister-group pairing exists between the gonorhynchiformfishes Dastilbe from several Brazilian localities (Neocomian–Aptian: Maisey, 1991)and Parachanos from the Cocobeach Series (Neocomian: Casier & Taverne, 1971;Patterson, 1975) of Rıo Muni. A second sister-group pairing is evident between theclupeiform fishes Ellimmichthys longicostatus (Cope) from the Ilhas Formation, Brazil,and Ellimmichthys goodi (Eastman) from the Cocobeach Series (Neocomian) of RıoMuni.

In addition to these sister-group pairings there are several other recorded sim-ilarities of taxa between the Santana Formation and the Elrhaza Formation ofGadoufaoua, Niger. Buffetaut & Rage (1993) record the great similarity betweenthe crocodile Araripesuchus gomesii Price (Brazil) and A. wegeneri Buffetaut (Africa), theturtles Araripemys barretoi Price (Brazil) and A. sp. de Broin (Africa) and Teneremys sp.de Broin (Brazil) and T. lapparenti (de Broin) (Africa).

It is to be emphasized that the relationships of most of these species are notdemonstrably sister-group pairings, but none of these genera is known to occuroutside of these areas. Thus the vicariant relationships shown by species ofCalamopleurus, Mawsonia, Ellimmichthys and Dastilbe/Parachanos all support the geologicalevidence suggesting both plate and depositional continuity between eastern Braziland north and west Africa during the Lower Cretaceous. Such conclusions may betested further with description of additional Moroccan taxa (e.g. Lepidotes? sp.) andbetter phylogenetic resolution of the groups to which they belong.

ACKNOWLEDGEMENTS

We are grateful to Steve McCarroll (FMNH) for the detailed preparation of theholotype specimen, to John Weinstein (FMNH) for photographic assistance, and toLori Grove (FMNH) for labelling the figures. PLF would like to acknowledge receiptof a Robert O. Bass scholarship which allowed him to carry out this work at theField Museum. His thanks go to the Committee administering this scholarship. LGthanks the U.S. National Science Foundation for funding his work on halecomorphfishes (including the species described here) with the following grants: NSF DEB-9119561 (to Grande & Bemis) and NSF DEB-9220938 (to Bemis & Grande).

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an african twin to the brazilian calamopleurus (actinopterygii: amiidae)

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