Nouüetes PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET, NEW YORK, N.Y

Home , Euhoplites, Hoplitidae, Quenstedtoceras

.. ..AMtrRICAN MT]SEUM Nouüetes PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. IOO24 Number 2823, pp. 1-21, figs. l-68, tables 1,2 August 7, 1985

Internal Structures in the Early Whorls of Mesozoic Ammonites

NEIL H. LANDMAN' AND KLAUS BANDEL'

ABSTRACT

The first few septa and a§sociated structures in not concave, toward the aperture. In Quenstedt grows dorsally the early whorls of Me§ozoic ammonites were ocer4s, however, the second septum is only coDspicuous on the studied in a numb{ of genera including Qaez- into the proseptum and are also expressed in stedtoceras, Kosmoceras, Euhoplites' Hypacan- venter. These relationships corresponding §uture§ thoplites, Baculites, ar.d Scqphites a\d its related the shape and spacingofthe genira. Exceptionally well-preserved specimens on steinkerns of the initial who![s. genera in which the original §hell struc- i^.irfr tiul" obscuring matrix inside permitted ob- 3. In all preserved. the second septum is nacreous. servations of the spatial arangement of the first lure was prismatic. Therefore, in agreement with few septa and were supptemented by section§ pol- not and Khiami (1970), we prefer the sim- ished paraltet to the median plane. Our observa- Drushchits pler second septum and third septum for üons indicat€ that: terms p.imary septum and nacroseptum. respectively' l. The proseptum is a single structure and does ' developmetrt ofa prismatic attachmenl not consi;t oftwo septa. Prismatic attachment de- 4. The base ofthe proseptum, dorsal muscle posits ofthe caecum and siphuncle occur around ridge at the scais adoral ofeach septum. and wrinkles in rhe proseptal oPening. iust pioseptum and prosiphonal attachment sheels 2. In ali genera excepl Quenstedtoceras the sec- the the model of early ammonite ontogeny ond septum is moderatety di§tant from the pro- support proposed by Bandel (1982). septum and, in median section, i§ slightly convex, INTRODUCTION and identified co- The earlv whods of ammonite shells fea- for their laxonomic utility of character states that rep- ture a complex arrangement of internal ele- herent clusters (Hiatt, 1894; Grandjean, 1910; resent diferent ammonite groups that are es- ments on the basis of other Schindewoif, 1954; Arkell, 1957). Recently, tablished mainly These elements have also been Tanabe et al. (1979) studied these elements characters.

lAssistantcurator,Depaflmentoflnvertebrates,AmericanMuseumofNaluralHi§tory. universität Hambuig, 2000 Hamburg 13, wesr 2 professor. ceologisch-paläontologscrres Instirui uno Mu§eum, Germany.

ISSN 0003-0082 / Price $2.50 Copyight O Amencan Museum of Naural Hi§tory 1985 2 AMERICAN MUSEUM NOVITATES NO. 2823

1. The presence of two prosepta. Arkell (1957) cites Grandjean (1910) as describing two prosepta although the first definite ref- erence to this construction appears in Böh- mers' (1936) and Miller and Unklesbay's (1943) studies of Permian ammonites. Schindewolf (1954) disagreed with their de- scription, but recently, Drushchits and Do- guzhayeva (1974) and Tanabe, Fukuda, and Obata (1980) reported two prosepta in Me- sozoic ammonites. 2.T};.e relationship between the proseptum and second septum. Schindewolf (1928,1929, 1951, 1954) called the first and second septa the proseptum and primary septum, respectively, to emphasize their difference in shape. According to Erben, Flajs, and Siehl (1969), these two septa commonly lie very close to- gether and, in median section, run straight or concave toward the aperture as compared to later septa. However, Dauphin (1975) noted an exception to this rule, which she inter- I preted as an anomaly of growth. Frc. l. Generalized median cross section of To further complicate matters, the first two the protoconch and first whorl after Erben, Flajs, septa, like all succeeding septa, display pris- and Siehl (l 969) shows the caecum (C), prosiphon matic deposits which attach the septa to the (p), siphuncle (S), flange (F), proseptum (l), second siphuncle. These deposits, referred to as false (2), third (3), and fourth (4) septa. septal necks (Birkelund and Hansen,l91.4), cuffs (Drushchits, Doguzhayeva, and Lo- minadze, 1977), auxiliary deposits (Kulicki, studied to elucidate the ontogenetic devel- 1979), and prismatic attachment deposits opment and functional morphology of newly (Bandel, 1982), are conspicuous on larger sep- hatched ammonites (Bandel, 1982). ta. However, their distribution on the first As shown in a generalized median section few septa is sometimes confusing and may (fig. I after Erben, Flajs, and Siehl, 1969), obscure the identification ofthese septa and these morphologic features consist of the ini_ their spatial relationships. tial chamber or protoconch, the inner lip or 3. The structure of the second septum. The flange, the first septum proseptum, or theiec_ prismatic structure of the first septum is well ond septum orprimary septum, the third sep_ established, but the structure of the second. tum, the beginning of the siphuncle or cae_ septum is in dispute. Erben, Flajs, and Siehl cum, the attachment sheets of the caecum or (1969) enumerated 16 ammonite genera in prosiphons, and the siphuncle. which the second septum was prismatic. in_ Although these basic features are well es_ cluding Quenstedtoceras, Acanthoscaphites, ta^blished, they cannot always be clearly iden_ and Discoscaphites. The first nacreous sep_ tified because ofvariation in their shape and tum they observed was the third position. Identification septum, and is especially difficult they, therefore, called it the first nacrosep- in median sections in whictr a three_dimen_ tum- However, Birkelund and Hansen (1974, sional perspective is lacking. In this paper we Kulicki (1979), report and Bandel (19S2) have since the results of our investigations bn the noted that the internal second septum is nacreous in elements in several arimonite spec_ many ammonites. imens free of interior matrix. These ."rii, 4. The first few sutures. The prosuture and permit us to address a number of issues that subsequent sutures form at the contact have been raised in the literature. be_ tween the corresponding septa and the outer 3 I 985 LANDMAN AND BANDEL: MESOZOIC AMMONITES

TABLE I Age and Locality of Species Studied

Bandel et 1982 Discoscaphites conradi (Mor- Maastrichtian (Fox Hills South Dakota al" ton)Formation)Erbenetal.'1969 Bandel et al', 1982 Hoploscaphites nicolleri Maastrichtian (Fox Hills south Dakota (Owen) Formation) Hoploscaphites sp. Campanian South Dakota Bandel et al.' 1982 Clioscaphites vermiformis Santonian (Marias River Montana (Meek and Hayden) Shale) Iandman' 1982a Bandel et al" 1982 Pteroscaphites auriculatus Coniacian (Marias River Montana (Cobban) Shale) Landman' 1982a Landman' 1982a Sc'aphites preventricosus Cob- Coniacian (Marias River Montana ban Shale) West Birkelund and Han- Scaphites sp. Coniacian-Campanian Nugssuaq, Green- land sen, 1974 south Dakota Bandel et al" 1982 "scaphites cf. whitfieldi cob- Turonian (carlile shale) ban l'andman' 1982a Bandel et al',1982 scaphites whitfieldicobban Turonian (carlile shale) south Dakota l-andman, 1982a scaphites lar.vaeformisMeek Turonian (carlile shale) south Dakota and Hayden (Marias Montana l:ndman' 1982b "Baculites sp. juveniles Santonian fuver Shale; CodY Shale) (Lower Folkestone, England "Euhoplites sp. Albian Gault) ,Hypacanthoplites sp. Aptian Algermissen, Germany Erben et al" 1969 sp. callot ian (erratic boulders) Lukow, Poland "Quenstedtoceras Blind, 1979 Kulicki, 1979 Bandel,1982 Erben et al'' 1969 sp. Callovian (erratic boulders) Lukow' Poland "Kosmoceras Kulicki, 1979

' Exceptional Preservation.

Ammonitina. Euhoplites be- wall. How do the shape and spacing of these family within superfamily within the same early sutures reflect the spatial relationships lons,s to another Hypacanthoplites, Baculites, an.d ofthe first few septa? subärder. Scaphites and its allied genera represent three diffirent superf;amilies within Ancylocera- MATERIAL AND METHODS tina. Altogeiher, these genera range geologi- to Maastrichtian and Resolving these issues requires well-pre- cally from Callovian western Europe to west- retaining the original shell for geographically from served mat;rial Western Interior of However, study of the three-di- ä."-Cie""tut a to the sectioning. Many of these genera have mensiontl geometry of the internal elements North America. previously been studied with scanning elec- further requires specimens free ofany interior (SEM; table 1). matrix. Suih preservation is rare but has been iron microscoPY free of obscuring matrix were in a variety of Mesozoic ammo- Specimens discovered and viewed under SEM' Subse- nites which, thereby, dictated the taxonomic dissected of parts of the shell sometimes composition of the material studied (tables quent removal new features and such specimens 1, 21. These ammonites fell into two subor- &posed (table *.i" .t"*u-ined. Specimens filled with ma- Oäri emmonitina and Ancyloceratina in belol;.g trix, on the other hand, were embedded 2). kosmoceras and Quenstedtoceras parallel to super- and ground and polished to two separate families in the same "poiy 4 AMERICAN MUSEUM NOVITATES NO. 2823

TABLE 2 The proseptum, the proseptal opening, and Taxonomic Distribution of Species Studied the second septum are further exposed in specimens in which the caecum is removed Suborder Ammonitina or not preserved (figs. a-7). Such specimens Superfamily Stephanocerataceae reveal a necklike attachment the prosep- Family Kosmoceratidae of Subfamily Kosmoceratinae tum which develops near the median plane Kosmoceras sp. and curves in an adoral direction. This struc- Family Cardioceratidae ture rides ventrally on the wall of the first Subfamily Cardioceratinae whorl and precedes the second septum. Quenstedtoceras sp. The interrelationships of these features are Superfamily Hoplitaceae displayed in a series ofsections prepared par- Family Hoplitidae allel to the median plane from a single spec- Subfamily Hoplitinae imen (figs. 8-13). In the most lateral section Euhoplites sp. (fig. 8), the proseptum stretches as a single, Suborder Ancyloceratina unbroken structure. The flange projects Superfamily Deshayesitaceae above Family Parahoplitidae it but only becomes conspicuous toward the Subfamily Acanthohoplitinae median plane. In this and all subsequent sec- Hypacanthoplites sp. tions, the second septum is adoral ofthe pro- Superfamily Turrilitaceae septum (to the right in these figures) and sep- Family Baculitidae arate from it. In the next most-lateral section Baculites sp. (fig. 9), the proseptum develops a local thick- Superfamily Scaphitaceae ening where its necklike attachment begins Family Scaphitidae to emerge. These two features subsequently Subfamily Scaphitinae separate (fig. l0) except at their dorsal and Scap hites whitfteldi Cobban ventral ends. In the next section (fig. Scaphites lamaeformis Meek and Hayden I l), the proseptum opens up expose part S c ap h iles p revenff i c o sus Cobban to of the Pteroscap hites auriculatus (Cobban) caecum. The opening of the proseptum is Clioscaphites vermiformis (Meek and Hayden) wider than that of its necklike attachment H op loscap hites nicolleti (Owen) which, therefore, is still unbroken at this point. Discos cap h it e s c o nrad i (Morton) In the last section (fig. l2), however, both these structures open up onto the siphuncle and caecum and are only conspicuous just the median plane. The polished surfaces were below the flange. Ventrally, the proseptum etched with EDTA for several minutes to pre- and its necklike attachment are inconspic- pare acetate peels. Peels were coated with gold uous and spaced moderately far apart. They have and viewed under SEM. All illustrated spec_ diverged on the venter as the median plane imens are either in the collections of the was approached. Additional prismatic American Museum of Natural History deposits connect the proseptum and its neck- (AMNH) or the Yale peabody Museum like attachment to the siphuncle and caecum (YPM). Scale bars in all illustrarions are 40 and are especially well developed on the dor- pm unless noted otherwise. sal side (figs. 12, l3). The second septum is adoral and slightly convex toward tlie aper- RESULTS ture. The proseptum and its necklike attach_ | . S cap hit es, C lioscap hit es, pteros cap hites, ment are prismatic in microstructure and Hoploscaphites, and Discoscaphites dis_ (igs. 2_ play a groove around their openings (fig. I"^ all these genera, 6). l5l: the protoconc[ typ_ The necklike attachment of the p.oseftum ically features a bulbous caecum which is at_ develops near the median plane where ii sur_ tached to the wall of the first chamber by rounds the distal end ofthe caecum and forms short prosiphonal sheets. proseptum The an adorally directed bend on the venter. The forms a median saddle. The proximat end of second septum is nacreous and separate from the initial chamber consists projecting of a the proseptum. The two septa only intersect flange above the caecum (figs. 2, 3). on the extreme lateral maryins (fig. 4). 5 1985 LANDMAN AND BANDEL: MESOZOIC AMMONITES

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F cl \\.t.' ''-L.- - i,äs,'.. 2 proto- whitfieldi. 2. Scaphites cf' whitfieldi (AM.N}{ 42899)' Interior of the Frcs. 2-3. Scaphites cf. (YPM tf," ptot"p*- (fl, nange (D, (C)' 3' Scaphites cf' whitfuldi 6239)' "ri"i-.*""f. tn""t, (p) tt. caecum"na (c) "t""u-to the protoconch wall' ili;;;;"rph".;i "täiit

and the flange projects These relationships are supported by ob- stretches undivided The second septum is separate and servations of the corresponding sutures on above it. (to rieht in these figures)' In the steinkems of the inital whorls (figs' 14, 15) adoral the (fig. 23), the necklike attachment The prosuture is angustellate, bu1 the neck- next section proseptum begins to emerge Nearer like ättachment of the proseptum forms a of the plane (fig.24). both the prosep- saddle, which is superimposed above the median small open up onto ventral saddle of the prosuture. The ac- tum and its necklike attachment the although these suture is distincfly separated from the caecum and siphuncle, tual second here' The second prosuture and the two only join on the features are not preserYed the at lhis point' A 6nal lateral margins. This arrangemenl seotum is still unbroken extrÄme (fig.25) reveals the flrst two been obserYed it Scaphites and all its mädian section has attachment oIthe prosep- i"lat"d g"t ..a studied from Nofth America seora. the necklike tum. and the septal neck of the second sep- and Greenland. -"i. second septum is slightly convex Baculites (figs. 16-26). Protoconchs of tum. The the caecum was not pre- toward the aperture. this genus in which and its necklike attach- flange, proseptum, and pro- The proseptum serväd reveat the priimatic. The second septum is opening (flgs. 16. l7). The proseptum -*t ui" seplal and displays a prochoanitic septal disolavs wrinl'Jes on its lareral lobes and on nu"."or. especially well developed on below the flange (figs l8' 2l)' neck which is iti.*r.n.lo, side (fig.25). Examination of A ridee occurs at the attachment ofthe pro- tlie renral (fig' ln .i"int"-. of the initial whorls reYeals that ..otrit ro the proloconch wall l8) prosep- necklike ar- the short necklike attachment of the itä p.o."ptat opening. a shon The pro- proseptum occurs which tum is not expressed as a saddle' tu"h-."t'of the suture are distinct and bend on the venter (figs' ."i"* second iorms a smatt adoräl ""a (tg 26)' septum lies at a mod- moderatelY far aPart iJ. t s. zor. rh" t.cond (frgs. A single pro- proseptum (flg l S)' 3. Euhoptites 27-34) ..ut.-- dirrun.. lrom the a caecum with prepared paratlel to the to"on"t oi tt ia genus reveals Ä sedes ofsections proslphonal attachment sheet' a ptutt" furtherieveal the geometry of ioutulur. -"äiur, " äna ßange projecling above the septa (figs. 22-25)' ltt the most prJ.ipru-. i the first iwo 27). T]ne caecum also displavs lateral section $g. 22\, the proseptum ä""""i" tni. 6 AMERICAN MUSEUM NOVITATES NO. 2823

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Ftcs' 4-7' scaphites cf. whitfizldi. 4. scaphites cf. whitfieldi (ypM 6240). view into the interior of the protoconch and first whorl rLveals the präseptum (l), necklike attachment ofthe proseptum (upper arrow)' and ventral traces of the-second (2) and-third ijj r"pt. it i"ooo septum only intersects the proseptum at the extreme lateral maryins (middle u.ro*). " proseptum ä par-r* ridge occurs at the base of the (lower arrow)' The caecum änd siphuncle ur" not p."-r"*"ä .'i. scapnrtes cf. whitfieldi (AMNH 429oo)' Interior of the protoconch and firsiwhorl rto*r j.oöiu-m proseptum tri" (l), flange (F), opening of the with its necklike attachment (arrow), andseco"o r"pi"." iä1.'i. scaphites cf. whitfieldi (AMNH 42900)' close-up ofthe specimen in figuie 5 reveals the prr,"pr.,* al),?änee (D, and necklike of the proseptum (middle arrow). ioaitlo.rut-prismatic artachmenr arrow) occur on the of the siphuncle (upper necklike attachment of the proseptum."ä;h;;t;"posits A groove (lower opening of the proseptum. arrow) occurs around the 7. sca.phites *h;tfi;i;;@;;§i+äöji. ii"* ri.; ih; n..1-*iä.irooure back into the protoconch across theproseptum(t;.ano"r. second gept-um (2) reveals the necklike ofthe proseptum (left arrow) and the p.ä"rro"niti. attachment septal neck ärtne'säcona septum (right arrow).

FIcs' 8-13' scaphites p-reventricosus (AMryg 42902). prepared parallel Five serial sections of the same specimen to the median plane (scalL bar 20 pm). 8.'Th; (l)' flange (F)' ;.rt äral section shows the proseptum and second septum (2).'9' I; th" ,r"*t mostJateral proseptum (arrow) section, the necklike attachment of the besins to emerge. 10. In this section, th" p.;;;;ü; (l) (arrow) display an and its neckrike attachment incipient t"pututiorr. I I .- h ,r"*t reveal part ;" io-rä ,ä"ii.", it proseptum (r has opened of the caecum (c). The nect

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Frcs. l4-15. scaphites cf. whitfieldi. 14. scaphites cf. whitfuldi (AMNH 42903). ventrar view ofthe prosuture (1), second suture (2), and third suture (3). The saddle (arrow) formed by the necklike attach- m9n! gf- the proseptum is superimposed above the median saddle of ihe prosuture. 15. Scaphites cf. whitfieldi (AlMN}l 42904). Doßal view of a steinkem shows that the prosuture ( I ) and second suture (2) are distinctly separated.

delicate prosiphonal strands attaching it to a furrow or a siphuncular attachment deposit the protoconch wall (fig. 29). Removal ofthe (figs. 38,40,42). This fearure is not nearlv dorsal shell further exposes the proseptum as well developed, however, as in Baculitis and second septum and reyeals that these 1wo and, Scaphites and, its related genera. The sec- septa are distinct bolh ventrally and dorsally ond septum is a moderate distance apart from and are a moderate distance apart (figs. 28, the proseptum and in the median plane rests 30). On the interior surface ofthe dorsal shell. dorsally on the wall of the protoconch and muscle scars appear adoral ofthe septal lobes not on the proseptum (frgs. 41, 42). (figs. 31, 32). The muscle field adoral of the 5. Quenstedtoceras (figs. 43-59). proto- proseptum is elongate. It may consist of a conchs ofthis genus free of matrix reyeal pair the of scars, although subsequent scars are proseptum, flange, and caecum (figs. 43-45). single. The caecum rests in lhe median saddle ofthe The proseptum prismatic is in contrast to proseptum and is attached to the walls ofthe the second and all later septa which are na- protoconch by prosiphonal sheets displaying creous. All septa show outer layers of a ho- wrinkles (fig. 45). The flange of the protoi mogeneous structure which originally may conch projects above the caecum (flg. 44). A have been (figs. organic 33, 34). prismatic ridge occurs at the attachment 4. Hypacanthopliles (figs. of 35-42). The pro_ the proseplum to the protoconch wall (fig. toconch, caecum, flange, and prosiphonal at- 43). lachment sheets of this genus are exposed in The proseptum is a single prismatic srruc- seweral specimens free ofmatrix (figs. 35_3g). ture. The second septum is nacreous and The prosiphonal sheers typically ionsisl of grows dorsally into the midheighl pro_ broad bands with ofthe shoner a achment threads sept-um toward the median plane (figs.47,49, (figs. 35, 37). Variation in the shape of these 53. 571._Ventrally. however. the two features may represen( septa are species-speiific or in_ distinctly separaled on rhe venter (figs. dividual differences. 47, Specimens without the 49, 54,56). This construction produces caecum preserved reveal the opening -53, of the a relatiyely small second chamber composed proseptum and the spacing of subsequent of two wedge-forming sections on either side septa (figs. 38-42). Around the proseptal of the siphuncle (figs. 47 , 49, 53). opening we observe a structure which is either These relationships are further clarified in l 985 LANDMAN AND BANDEL: MESOZOIC AMMONITES 9

Frcs.16-2l.Baculitessp.16.Baculitessp.(AMNH429o5).Viewintotheprotoconchshowsthepreserved' 17' nu"gä irre caecum and siphuncle are not proseptum (1), prosepti"ö"i;;,-;;J «ö. proseptum of tf," ipecimen in figure 16 reveals the flange (F), Baculitessp. (AMNH 4äö:öür.-rp of the proräptum. A-short_.r.:'Ljik;attachnient (arrow) occurs at the opening (l), and opening of tn. (l) of the same specrmen rn l&'aocutitri'"1i.1äMnH +-los1. crore-up of the proseptum ;;ö;#. A.frismatic tidg" o"ct"t at the attachment of the proseptum figure l6 reveals *.i"uäi"pp.. same "..*1. tS. Biculitis sp' (AMNH 42905)' Overview of the to the wall of the protolil;"d;;;".ro*1. reveals the short necklike figure 16 after mäst of the proseptum (1) has been .removed specimen in 20' Baculites sp' (AMNH 42905)' proseptum (arrow) adapical.of tr[ t"io"J i"pt"m(2)' attachment of the '""d proseptum (arrow) magnified from prosäp^t'uä-(ii ;."krik.-uiän-."t-of the The junction or trre iu.t ortn" p.oreptrr- (l) just below the flange figure t9 (white box). zi.Eiiitärrp. tevrNn-+zioäj. (F) displaYs wrinkles. l0 AMERICAN MUSEUM NOVITATES NO. 2823 '. t *;*--\ 'f:., -: '/,l:' , \.\ \. .\ ,2 .r\\[ 1' ti. , ,§ tt F,. 21.. \\i -A \

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Ftcs' 22-25' Baculites sp. 22. Baculites sp. (AMNH 42go7). Lateral section through the protoconch and first whorl reveals the proseptum rrl, nangL.o, aoo seconosium 42907). rzl. 23. Baculitessp. (AMNH More median section of the specimeä in 6gure 22 sh;;;'th" proseptum (r), second septum (2)' The.necklike flange (F), and attachment (arrowftf tne prosepium begins to emerge. sp' (AMNH 42907)' still more median 24. Baculites section.of the .n.aiä"" i-"'li[ure zz shows the proseptum (l), necklike attachment of the proseptum (arrows), na"g"^to,-""ä-r""ä"0 septum (2).25. Baiutites sp. (YPM 6241)' A median section through the protoconctrlnä fr'rst wtroiirerrears trre proseptum (l), necklike (arrows), flange (F1, u"J tt" ;fj|ff|,t,J,f,iliX:""T.""m '".o"ä '"p,r- (2) with; *eri-äe.,,eropeo more detailed views through the median flange (figs. 51,52,58). Ventrally, however, plane. Dorsally, the second septrrm may ap_ it is a distinct structure a moderäie distance pear as a rudiment below the proseptu- a.rd from the proseptum (figs. 4g, 50, 51, Sq_Si, 198 5 LANDMAN AND BANDEL: MESOZOIC AMMONITES It

DISCUSSION The intemal features in all of the ammonites sludied are basically very similar. The proseptum, or frrst septum, always develops al the transition from the cuplike protoconch into the planispiral first whorl (Erbon, Flajs, and Siehl, 1969). It closes offthe spherical to elliptical protoconch and appears to form a continuation ofthe flange. Its median portion consists ofa circular opening whose diameter equals the whorl heighl. This opening is ori- ented in a nearly vertical position between the flange and outer shell wall. The prosep- joins the outer wall to form 1wo lateral Frc- 26. Baculites sp. (AMNH 42908). ventral tum saddle. view ofthe prosuture ( l) and §econd §urure (2) on lobes and a median we a steinkem ofthe early whorls. In none of the genera studied did observe two prosepla. In Baculites aIJ.d in Sca- phites and its allied genera. the proseplum is 58). Prismatic deposits attach both septa to a single structure, although a necklike attach- the siphuncle and caecum and form elongate ment surrounds the proseptal opening. A sin- grooves (flgs. 48, 5 l, 52, 54, 55, 58). The third gle proseptum is also the rule irt Hypacan- septum is separate from the second septum ihoplites, Euhoplites, Kosmoceras, and both ventmlly and dorsally (fig. 50). Quenstedtoceras. lt Quenstedtoceras, lhe pro- Muscle scars occur on the interior surface second septum grows dorsally into the of the dorsal shell (fig. 46). The first scar oc- septum and may appear in median section as part of as a pair in the second chamber on either a rudimentary structure on the dorsal curs previ- side of the proseptal opening on the adoral the proseptum. This rudiment was face of the proseptum. The second scar is ously described by Erben, Flajs, and Siehl (1982), elongate and occurs in the third chamber (1969) and Bandel although Kulicki prismatic deposit of above the siphuncle. The third and all sub- i1979) regarded it as a sequent sqrrs are single and adoral ofthe dor- the proseptum. are com- sal lobes. Prismatic attachment deposits the openings ofthe On steinkems of the initial who s, the pro- monly developed around previously been de- and second suture are separated on the first few septa and have suture Kulicki (1979) and venter (fig. 59). The second suture displays scribed in Kaszoceras by Kulicki (1979) and shallow lateral lobes. \n Ouensredloceras by and in Scaphites 6. Kosmoceras (figs. 60-68). In proto- Baniel 1l 982.1. kr Baculites genera an adorally directed conchs ofthis genus free of matrix we observe and its-allied develops around the the caecum, flange, and first few septa (figs' necklike attachment also to rhe smaller 61. 64, 65). The proseplum is a single proseptal opening in addition 60. The prismatic deposits structure. It is prismatic and displays a pris- prismaric deposiis. the siphuncle and caecum matic attachment to the caecum and siphun- äthch the septa to elongate grooves as shown in cle (frgs. 66.67). The second septum is na- and may form - Bandel and Boletzky (l 979) creous and is separated from the pros€p1um Quenstödtoceras (1982) have suggested that these both ventrally and dorsallv (figs. 62' 63' 65)' Äd Bandel deposits are implicated in the In one specimen the second septum forms a prismatic from the chambers into the short adäpical spur below the siphuncle (fig' iransfer ofliquid is attached to the pro- On steinkerns of the initial whorls, the siphuncle. The caecum 62). prosiphonal sheets displaying ventral pans ofthe prosuture and second su- toionch by More finely divided attachments ture artdistinctly separate (fig. 68) The lat- wrinkles. occur between the caecum and the walls eral lob€s ofthe sacond sutule are more arched also the protoconch, as shown in Euhoplites than those \n Que nstedtoceras ' of t2 AMERICAN MUSEUM NOVITATES NO. 2823

t -tt

,s ,gß. ry.',

Ftcs' 27-32' Euhoplites sp. (AMNH 27261a).27. Interior of the protoconch shows the proseprum ( 1)' flange (F), caecum (c), and prosiphon (p). 28. view or tt .p""i-'"n in flgure 27 after much of the proseptum and dorsal wall has been removed " reveals the caecum (Cl, riptr""är" (sr, fi;";i;l"pr" tr, 2,3, 4)' The second §eptum (2) is distinct from the p.or"ptr^ tttü up of the proseptum (l) 1i I and dorsally. 29. close- and caecum (c) from ng;.e z'tJ (*hi;;;;;i ".rt."lly.e,reals the delicate prosiphonal attachment strands (p) betw-een the caecum (c) anä protoconch wau, ä0. view of the specimen in figure 28 after part of the caecum (c) has been remäve{ sec9nJr"il; ö) is distinct from the proseprum (1) and displays a short adapical spur (arrow). 1!e 31. view of the dorsal ,t ortn. .p""i-"" li'äg*" zz reveals muscle scars adoral ofthe^proseptum (l) and the lobes ofthe next"tt few septa (2, 3, 4). 32. close- up offigure 3l suggests that the first scär actuaily oit*" r"pär"" "o"rirtr but connecting scars. t985 LANDMAN AND BANDEL: MESOZOIC AMMONITES t3

FICS.33_34.Euhoplitessp.(AMNH2726la)(scalebar4pm).33-Theprismaticlayerofthepro- septirmissandwichedbetweenlayersofamolehomogeneousmaterialwhichoriginatlymayhavebeen ärärll. :a. itt" ,"creous layer oi the second septum is similarly sandwiched between layers ofa more ho-mogeneous material which originally may have been organic'

Wr;§'l '- :,: / -.-"i 38 (AMNH 20952a)' Interior of the pro- FrGS. 35-38. Ilypacanthopliles sp' 35' Hypacanthopli'e§.sp proseprum (D, and iange (F). 36. Hypacanthop_lites sp. toconch show§ the caecum «cl, p-r:,pn". ipl, box) revials minute prosiphonal attach- (AMNH 20952a). Ctor"-up of tn" ,p"i'i-i"ri'iir äe"r"lS (wirite (ci"J *at' ' HvpacanrhoDt es se (AMNH 20q52b) #;;;i;;;";;;;" the caecum ;;"t;';;;t .3t (R 38' tnä'"-uJ""rn prosipt'on (p)' pros"ptu- (l)' aad flange Interior of the protoconch *itr, tCi, (F) proseptum 2ogsici' r"te'i"' ofthe piotoconch shows the flanse and ;;';;;;;rh;;ir;;;;. iÄvNn of the proseplum' necklike attachment (arrow) occurs around the opening iiiäi".t.i.. "r',ä; t1 AMERICAN MUSEUM NOVITATES NO.2823

2 Frcs. 39-42. Hypacanthoplites sp. (AMNH 2o952d). 39. view into the interior of the protoconch reveals the proseptum (l), flange (D, and second septum (2). The caecum i, p."r"*"a. +0. cior"_ up of the specimen in figure 39 shows the flange (F) and proseprum (l). A "otfurräw or st o.t ,r"ctiit attachment (arow) occurs around rhe opening ofrhe proseptum. 41. säme specimen in ngur. " part proseptum i9;ü]i of the (l) removed reveals the flange @, second (2), third (3), and fourth (l1""ptu. li. Close-up of figure 4l shows proseprum the 11.1, opening of the prosefum *ith ir, n ..o* i"ä*i nung. (D. and the second septum (2) and its opening.

a;rd, Hyacanthoplites, arrd previously have (1982b), and in Euhoplites, the first seprum beer_called parrial septa by Shimizu ( 192{ is prismatic and the second septum ii na- and Tanabe er al. ( 1979). creous. The microstructure of the proseptum and These detailed observations on the micro_ second septum was observed in all genera slructure of the frrst two septa necessitate a except H ypaca nt h op I i t ?s. ln ue n t e sted oceras revision in the terminology used to describe and Kosmoceras the proseptum is prismatic them. The term proseptum emphasizes and the second septum the is nacreous! as pre- uniqueness of the first septum compared viously documented by Kulicki to {1979) and all later septa. Howeyer, the second and third Bandel ( I982). Similarty. in Scaphirer and its septa are commonly called rhe primary sep_ allied genera the proseptum is prismatic and tum and nacroseptum, respectively; this im_ the second septum is nacreous as suggested plies that the first nacreous septum is the third by Birkelund and Hansen (1974) in c;trasl septum. Our observations indicate, to the to Erben. Flajs. and Siehl ( 1969). y. Fina in contrary, however, that in all genera studied Baculites. as previously shown by Landman nacre is already developed by the second sep_ 1985 LANDMAN AND BANDEL: MESOZOIC AMMONITES l5

protoconch Frcs.43-46. Querctedtoceras sp. 43. Quensledtocercs sp. (AMNH 42909).Inlerior ofthe prismatic *iih the caecum G), part ofthe pr;siphon (p), proseptum (l), and second septum (2) A ridge protocorch' «".ro,"i o""u." uttact of tL" proieptum 1o the wall of the 44 Quen§tedtoceru§ -".ri proseptum (l), (2) ip ierr,rNi 42910)."t'Ui" View of the caecum (c), prosiphon (p), flange (F), and second (C) prosiphon (p) of the ä'.d'tiriia (3) septa. +S. Quenstedtoceras sp. (eIraNg 42911) Caecum and ,päiÄ"" in hg"." +9. 46.-euenstedtoceras ip. (AMNH 429-lO). View of the doßal shell of the specimen ii ngrr" +a öeals the muicle scars adoral ofeach of the frrst three septa. The flrst set of muscle scars of the i".rJrr) o""r.t as a pair (onty one §howing) on either side of the o^pening on the adoral face itt" t"conä t"i or tcars also-occurs as a pair adoral of the second septum (2)' The third ;;ö; ait grows into the il;ä;;; ;; single ado.al of the third septum (3). Note how the second seplum ""ar op€ning of the proseptum.

from tum. Ther€fore, in agreement with Drush- the second septum is similarly distant lateral chits and Khiami (1970), we recommend that the proseptum except near the extreme aperture the terms primary septum and nacroseptum margins and is convex toward the The first two septa are also be replaced by the simpler lerms second and in median section. Euhoplites and Hy- third septa. moderately far apaft n and related gen- Finally, the spatial relationship between the pacanthoplites. ln Scaphiles separate from first two septa was studied in all ten genera' ira, the second septum is again proseplum in median section. con- In Kosmoceras, the second septum is a mod- the and. The frrst two septa erate distance from the proseptum and, as vex toward the aperture. lateral maryins. shown by Kuticki (1979), is convex toward only intersect on the extreme the second the aperture in median section. In Baculites, However, in Quenstedtoceras, r6 AMERICAN MUSEUM NOVITATES NO. 2823

FIcs. 47-48. Quenstedtoceras sp. (AMNH 42912). 47. Yiew of the caecum (C), siphuncle (S), prosiphon (p), proseptum (l), and second septum (2). The second septum grows dorsally inio the proseptum plane. toward the median 48. Another view of the specimen in figure 47 looking into the ca"cu- 1C; reveals parts ofthe siphuncle (S), prosiphon (p), proseptum (l), and second septum (2). The prismatic attachment deposits of the siphuncle and caecum (arrows) are associated with grooves.

k' I

49-52. Quenstedtoceras sp. (AMNH 42gll). 49. Interior of the protoconch with the (c),-Ftcs' prosiphon (p), proseptum caecum (l), flange (F), and- second septum 1i;. io rhe other narroltne specimen in frgure 49 shows the caecum (c), part of the siphuncle «o,'nangeib, p.or.ptu- (l), part of the second septum (2), and ventral traces of the third (3) änd ruuritr «+l räptä.'3i. Specimen in figure 50 stightly rotated to reveal the interior of the caecum (c), parts of ttre siptrun"r" tsl, p.or"ptrr* the second (2) iijln""g" «n, and third septa (3). s2. close-up'of figure 5l (Ää;t..i;hows ttre "rro (s), flange(F), proseptum (l), possible rudiment o-fthe second.";-il (2), andprismatic"".":räiöfsphuncle attachmenr deposits ofthe siphuncle and caecum (arrows). 1985 LANDMAN AND BANDEL: MESOZOIC AMMONITES t'7

protoconch wilh th€ proseplum Frcs.53-56. Quenstedtoceras sp. (AMNH 429 t 3). 53. Interior ofthe (C). view ofthe specimen in figur9 5.3-.fr91 ffl, ,"ptrÄ «2), and pan ofihe caecum 54. Magnihed """."ä;glrt rno*t th" piosept,rm (l), second seprum (2), part of the-caecum (C)' and siphuncle (S) 55' it (C) öil."Iup" of ng*" 54 revials the proseplum (t1, second septum (2), parts of the caecum and -and in figure 53 with siptruncie (S) ä'nd üreir prismatic attachment aeposils (arrowg' 56 The same view as distinct on the ä'" piot"ptu- (l) and iecond septum (2) leveled fla1 reveal§ that the flßt two sepla are venter.

outlining the early onto- seDtum rides dorsally on the proseptum. as A general model was pro- previously shown by Drushchits and Khiami genetic development of ammonites (tlz0;, (19?9), and Bandel (1982), posed by Bandel (1982) and is supported by rutctl to this ventrally the two septa are distinct' ieveral ofour observations. According although first ditrerentiated A similar construction has been observed in model, the visceral mass siphuncle and, sub- the closely related genus Cadoceras (Drush- to form the cells of the ammonite began conslruclion chits, Doguzhayeva, and Lominadze, 1971)' sequently. the The visceral mass with- These spatial relationships are also ex- ofits phragmocone. the protoconch but was still at- oressed in the spacing of the corresponding drew from retractor muscles and siphun- .,ltura, on steinkerns ofthe initial whorls' In rached to it by tissue. The retractor muscles were Kos moceras, Quenstedtoceras, B aculites' and cular probably attached to the inner side of the Scaphites and related genera the second su- and the siphuncular tissue to the wall ture is ventrally separate from the prosuture' ilange The Yisceral mass formed of a median lobe and lateral sad- ofthe protoconch. It consists a central opening to Dorsally, the first two sutures are dis- an organic sheet with dles. the siphuncle and muscles' tinct except in Quenstedtoceras. accommodate 18 AMERICAN MUSEUM NOVITATES NO. 2823

58 FIcs. 57-58. Quenstedto-c-eras sp. Diagrams of.serial sections prepared parallel to the median plane reproduced from Bandel (1982). 57. A lateral section through the prätoconch and first whorl proseptum (l), shows the second septum (2), and flange (F). 58. A median t""iion shows the.u."u- piosiptron (p), sipruncle (S), flange (F), proseptum «Ej, (i), second septum (z), anJ prismatic attachmen-t ä-eposits or the siphuncle and caecum (arrows). 198 5 LANDMAN AND BANDEL: MESOZOIC AMMONITES l9

This organic precursor ofthe proseptum was firmly attäched to the walls ofthe protoconch in a prismatic ridge as shown it Baculites, Scaphites, Quenstedtoceras, and Kosmocer- aJ. It later mineralized, wrinkles and all, to form the prismatic proseptum as shown, for example, in Baculiles. After formation of the proseptum, the retractor muscles reattached in two bundles to the adoral face of the proseptum on either side of the proseptal opening as shown in Euhoplites and QuenstedtoceraJ. Subse- quentty, the caecum and its prosiphonal attachment sheets formed. At this stage of de- Frc.59. Quenstedtoc"r4.! sp. (AMNH 42914). velopment, the ammonite hatched from its Ventral view of the prosuture (l), second suture (2), and third suture (3) on a steinkern ofthe early whorls.

I ffi c 'J S L.- - '.t 2 ra.. \ilri:.? I * EH proseptum Frcs. 60-63. Kosmoceras sp. (AMNH 42915). 60' Interior of the protoconch with the from a stightly different I I)- flanse {F). and part ofthe caecum (C) 61. Specimen in figure 60 viewed ;;;;;;;ü;;:eptum rlt, flange (i,.caecum (c), siphuncle (S), and §econd s€ptum (2)' 62 same ,it", pu.. of tf,e pioseptrrm (t) and caecum (C) have been removed reveals that spur (arrow) below "ij*second "i'ir'-ne;i"'O] sJptum (2) is distinctly separated from the pro§eptum Note-lhe adapical tfre that ür" ,ipf,"."1"'t§i Oi.'ipecimen in figures 6G-62 after most of the shell has been removed shows the fißt three septa are di§tinc1 on the venter' 20 AMERICAN MUSEUM NOVITATES NO. 2823

FIcs. 64-67. Kosmoceras sp. (AMNH 42916).64. Interior of part of the protoconch and first whorl with the proseptum (l), caecum (C), siphuncle (S), and second septum (2). A prismatic ridge (arrow) occurs at the attachment of the proseptum. 65. Specimen in figure 64 viewed at ä stghtly diffeient angle shows the proseptum (l), caecum (C), siphuncle (S), and second septum (2). Th; setond septum is distinctly separated from the proseptum. 66. Close-up of figure 64 (white box) reveals the proseptum (l), caecum (C), and prismatic attachment deposits of the caecum'and siphuncle (arrows)'and their associated groove. 67. Close-up of figure 66 plainly shows the proseptum (l), caecum (ö), and the prismatic attachment deposits of the caecum and siphuncle (arrows) u.ta tn"ii aisociated groo"".

egg capsule as a miniature adult with the ca- pability to control buoyancy. It could fully or partly pump out liquid from its protoconch and utilize the resultant lift.

ACI(NOWLEDGMENTS We thank Dr. Edwin Kemper who kindly identified the specimens of Hypacanthoplites and Drs. Tove Birkelund, Harry Mutvei, Cyprian Kulicki, Niles Eldredge, and John Maisey who critically reviewed the manu- script. Misses Joan Whelan and Eileen polk Frc. 68. Kosmoceras sp. (AMNH 42917). assisted in scanning electron microscopy, Mr. Ventral view of the prosuture (l), second suture Peter J. Harries in photography and plate (2), and, third (3) suture on a steinkern ofthe early preparation, and Miss Susan Klofak in spec- whorls. imen preparation. I 985 LANDMAN AND BANDEL: MESOZOIC AMMONITES 2l

LITERATURE CITED 1969. Die Frühontogenetische Entwicklung der Schalenstruktur ectocochleater Ce- Arkell, W. J. phalopoden. Palaeontogr. Abt' A, vol. 1957. /n Moore, R. C. (ed.), Introduction to 132, pp. l-54. Mesozoic Ammonoidea. Treatise on In- Grandjean, F. vertebrate Paleontology L. Geol. Soc. 1910. Le Siphon des ammonites et des be- Am. and Univ. of Kansas Press, Law- lemnites. Soc. G6ol. Fr. Bull., vol. 10, rence, Kansas, PP. 81-129. pp.496-519. Bandel, K. Hyatt, A. 1982. Morphologie und Bildung der Frühon- I 894. Phylogeny ofan acquired characteristic. togenetischen Gehause bei Conchiferen Proc. Amer. Phit' Soc., vol. 32(143), pp' Mollusken. Facies, vol. 7, 198 PP. 349447. Bandel, K., and S. V. BoletzkY Kulicki, C. 1979. A comparative study of the structure, 1979. The ammonite shell: its structure, de- development, and morphological rela- velopment and biological significance. tionship of chambered cePhaloPod Acta Paleontol. Polonica, vol. 39' pp. shells. Veliger, vol. 21, pp. 313-354. 97-142. Bandel, K., N. H. Landman, and K. M. Waage I-andman, N. H. 1982. Micro-ornament on early whorls of Me- 1982a. Ontogeny and evolution of I-ate Cre- sozoic ammonites: implications for ear- taceous (Turonian-Santonian) Sca- ly ontogeny. J. Paleontol., vol. 56' pp' phites. Unpublished Ph.D. dissertation, 386-39 l. Yale UniversitY, New Haven, Conn., Birkelund, T., and H' Hansen 341 PP. 1974. Shell ultrastructures of some Maastrich- 1982b. Embryonic shells of Baculites. J. Pa- tian Ammonoidea and Coleoidea and leontol., vol. 56(5), pp. 1235-1241- their taxonomic implications. Kong' Miller, A. K., and A. G. UnklesbaY Danske. Videnskab' Sel. Biol. Skn', vol' 1943. The siphuncle of I-ate Paleozoic am- 17, pp' 20(b), PP. 2-34. monoids. J. Paleontol., vol. l- Blind, W. 25. l9ig. The early ontogenetic development of Schindewolf, O. H. ammonoids by investigation of shell 1928. Zur Terminologie der Lobenlinie' Pa- pp' structures. Symp' on Ammonoidea, Syst' läontol. Zeitschr., vol. 9, 181-186' Assoc. York Abstracts, 32 PP. 1929. Vergleichende Studien zur Phylogenie' der Böhmers, J. C. A. Morphogenie und Terminologie preuss' geol' 1936. Bau und Struktur von Schale und Sipho Ammoneenlobenlinie. Abh' n. ser., vot. I 15, 102 pp' bei Permischen Ammonoidea' Diss' l.andesanst. Terminologie der Univ. Amsterdam, 125 PP' I 9 5 I . Zur Morphogenie und Paläontol' Dauphin, Y. Ammoneen-Lobenlinie' et des tours Zeitschr., vol. 25, PP. I 1-34, Pl' l' t§l S . Anatomie de la protoconque Beudanticeras beudanti 1954. On development, evolution and ter- initiaux de Bull' (Brongniart) et Desmoceras latidorsa' minology of ammonoid suture line' I I2(3)' pp' ium (Uicneln). Annls' Pal6ont' (Inver- Mus. Compat.Znology,vol' t6br6s), vol. 6l(l), PP' 3-16' 217-237. V., and L. A- Doguzhayeva Shimizu, S. Drushchits, V. . Upper Creta- - characteristics of 1929. On siphuncle in some lSlq. §ome morphogeneric Saitohoonkai Publ'' phylloceratids and lytoceratids ceous ammonites. -(Am- vol. 4, 9l-l l6' mönoidea). Paleontol. J', vol' 1, pp' PP. Tanabe, K., Y. Fukuda, and I' Obata 37-48. development and func- V. V', L. A. Doguzhayeva, and T' A' 1980. Ontogenetic Drushchits, tionaimorphology in the early groyh- Lominadze of three cretaceous ammonltes' Internal structural features of the shell stages 1977 . Bui. Natl. Sci. Mus., Ser' C (Geol'), vol' Middle Callovian ammonites' Pale- of 6(1), 9-26. ont. J.' vol. 3, PP' 271-284' PP' Tanabe, f., t-. bUata, Y. Fukuda, and M' Futa- Drushchits, V. V., and N. Khiami - of the septa, protoconch walls kami lgio §tructure Early shell growth in some Upper Cre- and initial whorls in Early Cretaceous lg7g. taceous ammonites and its implications ammonites. Paleontol. J., vol' 1, pp' 26- to majortaxonomy' Bull' Natl' Sci' Mus' 38. Ser. Ö (Geot.), vol' 5(6), pp' 153-176' Erben, H. K., G' Flajs, and A' Siehl