Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 4 (2001) 121-138 05. 1 I. 2001
Biological aspects of an interesting fossil fish: Paramblypterus duvernoy i (Amblypteridae, Actinopterygii)
Kathrin Dietze’
With 10 figures
Abstract
Based on three-dimensional models of the skull and body of Pnrumhlyptenis dzivemoyi, function of the feeding apparatus and potential of locomotion are interpreted. Compared to most other lower actinopterygians, certain modified features regarding the suspensory apparatus, snout bones, gape, dermohyal and suborbital region. and palatoquadrate-maxillary chamber. are present in P dirvevrzyoi. These features suggest an increased versatility of the skull and/or enlargement of underlying muscles. thus improving the ability of food uptake. The weak, pin-like teeth present in P dirvemoyi suggest a main diet of small or soft-bodicd planktonic or benthic invertebrate organisms. Axial locomotion of P diivevmyi appears to lie within the range of moderate swimming speeds. k! drivernoyi probably had a flat belly indicating that this species lived close to the bottom.
Key words: Lower Permian. Southwest Germany, basal actinopterygians, functional morphology, feeding, locomotion
Zusammenfassung
Anhand drei-dimcnsionaler Modclle des Schadels und Kdrpers von Pczrrimhlyprenis hvernoyi werdcn Funktionswcisc clcs Ernahrungsapparates und M(iglichkeitcn der Fnrtbewegung interprctiert. Im Vergleich mit anderen basalen Actinopterygiei-ti crscheint die Schadclrekonstruktion von F1 duvernoyi hinsichtlich des Suspensoriums, der Schnauzenknochen. der Muncliifl- nung. des Dermohyal- und Suborbitalbereiches, sowie der Palatoquadratum-Maxillare-Kammer abgeleitet. Dies deutrt auf eine erhdhte Bcweglichkeit in diesen Bereichen undioder eine VergroOerung der darunter liegenden Muskeln hin. W~ISvorleil- haft fur die Nahrungsaufnahme ist. Die schmalen, stiftformigen Zahne von F! drivernoyi deuten auf eine ErnBhrung \on kleincrcn oder weichkdrperigen benthischen und planktischen Invertebraten hin. Vermutlich zeichnete sich die axiale Fortbe- wegungsweise von Purarnhlypteriis durch maBige mittlere Schwimmgeschwindigkeit aus. Der Bauch von P riiivev/ioyi war wahrscheinlich abgeflacht. was darauf hinweist, dass diese Art bodenbezogen gelebt hat.
Schliisselworter: Unter-Perm (Rotliegend), Sudwestdeutschland, basale Actinopterygier, Funktionsniorphologie. Erniihrung. Lo koino ti on
Introduction function of their feeding apparatus (Schaeffer & Rosen 1961, Lauder 1980~1,Gottfried 1992, Ver- Basal actinopterygians, often referred to as “pa- an 1988, 1996), and even less is known about leoniscids”, are abundant in both marine and la- their potential of locomotion (Di Canzio 198s). custrine deposits worldwide (e.g., Aldinger 1937, The present study attempts to clarify the likely Blot 1966, Boy 1976, Gardiner 1963, 1967, Low- diet and food uptake, and the likely locomotor ney 1980a, Kazantseva-Selezneva 1981, Long capabilities of the Lower Permian Pflranzhlyp- 1988, Esin 1997, Daeschler 2000). Scales of these teriis duvernoyi. P dztvernoyi is a member of the fishes appear as early as the Silurian (e.g., Gross family Amblypteridae and, together with the 1968), and skeletal remains are known since the other members of this family P gelbrrti, F! tieco- Devonian (e.g., Gardiner 1984). They are found rus, and Anzblypterus lotus, has been described wcll into the Triassic (e.g., Hutchinson 1975), recently (Dietze 1998, 1999, 2000). Their mor- even though they are less abundant than in Pa- phology and intra-specific variation has been ex- leozoic times. Still, their biology is understood amined in detail and were the basis for three-di- only poorly. Few studies have dealt with the mensional models of the skull and the body. One
’ Institut fur Palaontologie, Muscuin fiir Naturkunde, Humboldt-Universitat, Invalidenstr. 43, D-10115 Berlin. Germany. E-mail: [email protected] Received January 2000, accepted December 2000
( WILEY-VCH Verlag Berlin GmhH. 13086 Berlin. 2001 1435-1Y4~3/01/0411-0121$ l7.50+.5(1/0 122 Dietze. K.. Biological aspects of PnrLr/nhlypterus objcctivc of tk,e restoration in three dimensions Material and methods was to gain a certain understanding of the bio- logy of Pnrcin!h!\~prems diwerm!,i and its rela- All specimens of Prr,.o/iib!\lpr~'r~r.sdrivenioyi (Agassiz 1833) examined here are from lacustrine deposits from the Lower t ives. Studies of Pcr rtrri 1 hl~,preri 1.7 and A 17 1 b l~sp- Permian of southwest Germany (e.g.. Boy 1976. 1994, Dietx terii.7 are :onnected with research on 1099. 7000). For a complete list of catalogue numbers see paleoecosystel-is of lakes from the Lower Per- Diet7e (2000). Specinicns of ~trr.o/iib/~prc,r~~.sdi/vernoyi are preserved as mian of Centrid Europe (e.2.. Boy 1994. in press. coinpi-essions flattened during fossiliLalion. Surface structure, Clausing & Boy 2000. Boy et al.. Rotliegend-Pa- such as sculpturing of the skull roofing bones and scales, is Iaookologie, Unpublished report to the Deutsche present on many specimens. A Wild Mli microscope equipped with a camera lucida was used to draw the speci- Forschungsgenieinschaft [DFG]). Objectives are mens. Drauings of the best preserved specimens were used the reconstruction of environmental conditions. for threi-diinensioiinl i-cstoration. These drawings we]-e trans- paleocommunities. and food chains. To gain in- fei-I-ed oilto thin paper which was melted on thin plates of bees' \\ax. These piipei- and wax -bones" of the skull and sight in the intzractions of spccies. it is important palate \wre then cut out and assembled in a thi-ee-dimcn- to investigate their likely diet and locomotor sional model. Reconstruction of the postcranial part was un- abilities (e.g.. ( apacity to evade predators). Infor- der-taken in similar fashion and. including the restored Gns. fit onto the reconstructed skull and photographed. To obtain mation obtain :d from morphology and models thc like]! life form of I? drivcrnovi, line drawings of the serves to evalitatc the locomotory capabilities of photograpli~\sere niade. enlarged. redrawn with wax pencils Prrrrrtnhhytcw i diirertiojsi during feeding and lo- and ink and reduced to their original size. Trunk leiigtli (TL) was measured from the posterior mar- comotion. gin of the supracleithrum to the center of the caudal fin (as In functional morphology function can be in- indicated b!, thc shadcd scale in Fig. 7A). Scale rows wcrc ferred from :ertain morphological structures. counted along the lateral line between supracleithrum and the inclination of the scales anterior to the caudal fin. Where However, there is not always a direct correlate possible. fin rays were counted at the base of the fins. Draw- (Lauder 19XOz. 1995). If extinct animals are in- ing' of the tails wcrc digitized in AUTOCAD 14 and areas volved function cannot be directly observed or \\ere calculated. Aspect ratio was calculated by dividing the span (we helolv Fig. 7A) squared by the area of the caudal experimentally tested. and interpretations need fin. Hypo- and hetcrocercal angles of thc tail were measui-ed to be cstablislied carefully (Webb 1982). More- at the "chondrostean hinge" indicated by the shaded scale in over. structural elements oftcn perform a rnulti- Fig. 7. Three dimensional profiles ol the body as illustrated in plicitv of func.ions and therefore should not be 15s. 7B \\ere obtained from the wax model of P tliivernuyi. evaluated sep: rately (Liem Bi Wake 1985). One Tc I- i 11 o I o g ! way to avoid nisleading lines of evidence when m dealing with fossils. is to find closely related. and Terminology follo\\~sArratia & Schultze (1991) and Arratia & Clouticr (1096). Other terminologies set off by quotation ideally sirnilai constructed Recent species of niarks. except for the -nasal". reler to earlier works (e.g.. which empiric.11 data is available to test the va- Blot lc)66. Hcylcr 1969) and employ the common tcrminol- lidity of interpretations of certain structures. An og! for pamniblypterid fishes. Different terminologies are currently being used for dermal cranial bones (e.g.. Arratia analysis of the functional anatomy of Recent b: Cloutier 19%. based on homologization: Poplin Sr Lund lower actinopt xygians can provide data for rnor- 1997. traditional nomenclature). For bone terminology phological ink rpretations of fossil lower actinop- adopted hcrcin differing from common usage. e.g. "nasal 1 derinosphenotic 1-2. jugal 1-2, see Dietze (2000). terygians. Sucl$observations may corroborate in-
ference of fuiiction from structures present in In\ t i t LI t i on a 1 a b b re vi ii t i ons fossil fishes. However. only few bass) actinopter- 'Ilie material examined belongs to the institutions listed be- ygians, the morphological traits of which may be 1015: CAS. California Academy of Science; GPIM, Geolo- used to interr ret those in Pcii.ariihl?,pro.iis Sau- ~isch-Pal~ontologischcsInstitut Mainz: KMMA, Koninklijk vage. 1888. exist today. Of these. Po!\*ptetxs (e.g.. Museum \ oor Midden-Afrika. Tervuren: ME. Museum fur Naturkunde der Humboldt-Universitat, Berlin; PMNB, Pfnlz- Bartsch 1997). Acipemcr (e.5.. Marinelli & Stren- muwum fur Naturkundc. Bad Diirkheim. See Dietze (2000) ger 1973). and Lepisosreiis (e.g.. Gemballa 1995) for a complele list of specimens. have been dealt with mostly. Even though Recent specic s are somewhat different from Plrvanzh/ypferiri, the information obtained from Constructional morphology their structure; and soft tissues not preserved in Prrrcrt7ihlyplerri i can be employcd to explain cer- Feeding apparatus tain traits of tlie feeding apparatus and potential of locomotion, especially since information on Suction feeding is the basic method of acquiring functions in b:ml fossil actinopterygian is scarce food in living actinopterygians (Lauder 19SOa) (Schaeffer & Rosen 1961. Lund 1967. Lauder and is probably the ancestral method of food ac- 1980a. 1989. Ci Canzio f985. Veran 1996). quisition in all groups of aquatic gnathostomes. Mitt. Mus. Nat.kd. Bcrl.. Geowiss. Reihe 4 (2iiOl) 123
The inertial suction strategy of prey capture re- condyle of the quadrate is oriented at almost quires the creation of a center of low pressure right angles with the jaw margin (Fig. 1A. F. G) within the buccal cavity by rapid mouth opening and corresponds to a similar shaped facet on the and expansion of the buccal floor (Lauder lower jaw. The anterodorsal portion of the quad- 1985a). The pressure differential between the rate contacts the posterior margin of the dermo- buccal and opercular cavities and the surround- metapterygoid (Fig. 1G). The dermopalatines are ing water results in a flow of water into the in series with the ectopterygoid (Fig. 1A) as in mouth. If the velocity of the flow is sufficiently Polypterus (Fig. 2C). The entopterygoid is similar great the prey will be sucked into the mouth. in shape tot he ectopterygoid and lies anterior to According to Lauder (1980a), two phases can be the dermo-metapterygoid. The dorsal margin of distinguished during suction feeding in lower ac- both dermo-metapterygoid and entopterygoid tinopterygians: an expansive and a compressive abut on the lateral margin of the parasphenoid phase. The expansive phase is defined as the (Fig. 1A). Vomer(s) are present in Polypterirs time from start of mouth opening to maximum (Fig.2C), but could not be observed in speci- gape, the compressive phase from peak gape un- mens of Paramblypterus examined here. til complete closure of the jaws (Lauder 1980a). The presence of a dermo-metapterygoid as a A preparatory phase precedes these in teleosts separate element in Polypterus and other basal (Lauder 198Sb), but is not performed in lower actinopterygians has been subject of ongoing de- actinopterygians. For teleosts, movements of the bate (e.g., Lehn 1918, Allis 1922, Jarvik, 1980. suspensorium and jaws have been predicted by Gardiner 1984, Arratia & Schultze 1991, Grande four-bar models concerning the anterior jaw link- & Bemis 1998, Clemen et al. 1999, Wacker et al. age (Westneat 1990) the opercular linkage (An- in press). Arratia & Schultze (1991) and Grande ker 1974), or the hyoid linkage (Muller 1987). In & Bemis (1998) considered the corresponding Polypterus, Lepisosteus, and Amia movements element a metapterygoid associated or fused might be predicted by using the mandibulo-hyoid with tooth plate(s) during ontogeny, whereas the coupling (Lauder 1980a, 1982). other authors described a plate-like dermo-me- tapterygoid, which is not fused to the palatoqua- drate and consequently, a metapterygoid is miss- Palatoquadrate and associated ing. The latter appears to apply for elements Paramblypterus. Thus, what has been considered A complete palatoquadrate could not be ob- a metapterygoid earlier for Pmimhlvpteriis served in any specimen of Pnramblypterus. Ossi- (Dietze 2000) is likely to represent a dermo-me- fications of the dermo-metapterygoid and quad- tapterygoid only. rate are preserved in P gelberti and f! duvernoyi (Fig. 1). These are the first to ossify in Poly- Parasphenoid pferus, and it appears that the palatoquadrate of Parm~blypterusalso arose from three ossification The parasphenoid is the most prominent element centers (pars quadrata, pars metapterygoidea, of the ventral part of the braincase in Prrrnni- and ?pars autopalatina) either without a bony blypteria (Figs lA, 3A-G). The corpus para- autopalatine, as is the case in almost all lower sphenoidis lies along the midline of the skull and actinopterygians (Arratia & Schultze 1991), or does not contact the premaxilla, but leaves a gap with an autopalatine that ossified only late in on- anteriorly which most likely was occupied by togeny. In contrast to Lepisosteus (Arratia & “vomeral platelets”. Laterally, about midway Schultze 1991), the dermo-metapterygoid does along the length of the corpus parasphenoidis. not have a dorsal process to articulate with the abuts the entopterygoid. Posterior to the entop- braincase, but is similar to the corresponding ele- terygoid lies the dernio-metapterygoid which ment in Polypterrcs (Figs lA, H, 2C, E). The der- barely contacts the parasphenoid. The parasphe- mo-metapterygoid (Fig. 1A, D-H) sutures to the noid has well developed ascending processes ectopterygoid laterally and slopes dorsomedially which point laterodorsally. However, no features towards the posterior end of the parasphenoid. of the neurocranium could be observed and their Anteriomedially, it sutures to the entopterygoid, articulation remains unknown. The corpus para- and contacts the quadrate posteroventrally. Its sphenoidis is somewhat bilaterally asymmetrical ventral face is covered with small rounded gran- and slightly variable in outline (Fig. 3C-G), ular teeth, except for a smooth margin poster- which could be the result of preservation. In dor- iorly and dorsally. The mandibular articulation sal view (Fig. 3A), a depression probably sur- 123 Dietze. K., Biological aspects of Pizn~rnhlypterus
C
E
H
Fig. 1. A. Rcst0rat.m of the palate of mr.rrriih/!,i,rer.rrs drri er.rioj,i and P gr~lherri.ventral view (GPIM-M2248 & GPIM-M2315). B. Left entopterygoicl in Lentral vie\\.: GPIM-M3972. C. Lel‘t entopt goid in dorsal view: GPIM-M4972. D. Right dermo- metapterygoid in \ entral view: GPIM-M3907/3. E. Right dermo-metapterygoid in dorsal view: GPIM-M2267. E Right dermo- metapterygoid. ec~opterygoiil. and quadrate in dorsal 1 ien: GPIM-M.5811. G. Right entopterygoid. dcrmo-metapterygoid, ectopterygoid. and quadrate in ventral viciv: GPIMM-M5?6-3.H. Right entoptcrygoid. clermopalatines. dcrmo-metapterygoid. and ectopkrygoid in ventral view: “nasal 1 .. (black shading) covering part of the dcrmopalatines: GPIM-M2291. R-D, F. P dzrLwrio!,i. E. G-11. P gdberri. Scale bar = 10 nim. a.1.j. cond!,lc for articulation with lower jaw: Dmtg. dermo-metapterygoid; Dpl. dermopalatin :s: Ect. ectopteryeoid: Ent. entopterygoid: m.h.1. mandibulo-hyoid ligament: Mx, maxilla: “Na l”, “Nasal 1”: Par. parasphen )id: Pmx. premaxilla: Q. quadrate. rounding the opening of the bucco-hypophysial parasphenoid (Fig. 3B). The tooth patch covers canal and two grooves. which correspond to the about one third of the bone anteriorly, and course of the 1)arabasal canal. can be observed. widens posteriorly towards the ascending pro- The ventral surface bears a tooth patch of granu- cesses where it covers Inore than half of the sur- lar teeth which covers thc middle portion of the face of the parasphenoid. Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 4 (2001) 12s
d.o I.Exc a.op ep
a.op a.hy
0.m hhs B A
Fig. 2. A. Pffrff~b~y~f~~~~duvermyi, tentative reconstruction of musculature. B. Pdypterus bichir, muscles involved in the feeding mechanism. medial view (modified from Lauder 1980a, Starck 1979). C. F hichir, palate in ventral vicw (modified from Starck 1979, Clemen et ul. 1998: palatal granular teeth based on specimens KMMA- RG8823P166 and CAS 68161). D. P. bichir, muscles involved in the feeding mechanism, lateral view (modified from Lauder 1980a, Starck 1979). E. Polyprerrrs bickir. palatoquadrate and associated elements in medial view, anterior facing left (modified from Allis 1922. Clemen er rrl. 1998). a.hy, musculus adductor hyomandibulae; a.m, musculus adductor mandibulae; Ang, angular; a.op, musculus adductor operculi; apa. autopalatine; Ch, ceratohyal; Cor.proc, ’coronoid’ process; D, dentary; Dmtg, dermo-metaptcrygoid; d.0. niuscu- lus dilatator operculi: Dpl. dermopalatine; Ect, ectopterygoid; Ent, entopterygoid; ep, epaxial rnusculaturc; Gu, gular: hh.s. musculus hyohyoideus supcrioris; Hym, hyomandibula; ih, musculus interhyoideus: I.a.p, musculus lcvator arcus palatini: I.Exc. latcral extrascapular; Mx, maxilla; obi, musculus obliquus inferioris: 0.m. operculo-gular membrane: Op, opercle: Pa, parietal bone; Par, parasphenoid; Pmx, premaxilla; Pop, preopercle; Ppa, postparietal; ‘LShn”, “suborbital”; Sop. subopercle; Spir. spracular plates; St. supratemporal; Q, quadrate: Vo. vomer. Dentition fairly fragile structures. Dentary, maxilla, and premaxilla bear teeth (Figs 4A, B, 5A-C). The In most specimens, teeth were preserved poorly teeth are closely set slender, pointed structures or not present at all indicating that they were bearing an acrodin cap (@wig 1978), which is 126 Dietze. K.. Biological aspects of Prrranzhlyptenrs
!.. .. I
i L
A
YR
Fif. -3. Parasphenoid of t-'i/i.o/,rA/~,pct.,.lr,.A Ilol-sal \ ien of P gc/hr,.ri: GPIM-M2267. B. Vcntral view of i? gelherti; GPIM- M224X. C-G. P ti rwr.rio>,i. C. PMNB-WOR66. D. GPI>l-M4973. E. GPIWM1972. E GPIM-M5813. G. GPIM-M4907. Scale har = 10 mm. asc.~iroc. ascending process: b.h.c. dcprcssion probably surrounding bucco-hypophysial canal: par.c, parahasal canal: spi.g. spiracL lar grocm L'.
usually not prt served. Supposedly. the shafts of Contrary to Blot (19661, the teeth of Puvnm- the teeth were composed of a thin layer of den- /?/)bpfer~i5rlecoriiJ are similar to those of I? gel- tine surroundir g a wide pulp cavity which caved herti and I? diivernoyi. Specimen MNHN-PA in during fossilization. thus causing a secondary (Blot 1966: pl. 1x6) shows what has often bccn dorsoventral g-oove along the midline of thc referred to as tubular dentine (Blot & Heylcr teeth (Fig. SA) Only the anteriormost premaxil- 1963. Blot 1966. Heyler 1969, Poplin & Heyler lary teeth arc: inclined backwards (Fig. 5B). 1993). In my intcrpretation of this specimen, the whereas the fo lowing teeth in dentary and max- so-called tubular dentine are impressions of den- illa are sitting straight. Coronoid and prearticular tary and maxillary teeth, and the rough surface bear knobby tr eth (Fig. SC). Granular teeth are is not part of the maxilla, but is caused by the present on all fdatal bones. teeth of both sides having been pressed against Mitt. Mus. Nat.kd. Berl.. Geowiss. Reihe 4 (2001) 127
Br.r A B Fig. 4. Pcir-Lintblyptenis duvernoyi, restoration of the skull (GPIM-M5819 and GPIM-M4939). A. Lateral view. B. Anterior view. Scale bar = 10 mm. Ang, angular; a.no, anterior nostril; Btx, branchiostegal rays: CI, cleithrum; D, dentary: Dhy. dernio- hyal: Dph 1-2, dermosphenotic 1-2; Hym, hyomandibula; Ju 1-2, jugal 1-2; La, lacrimal; 1.Gu. lateral gular: m.Gu. median gular; Mx. maxilla; “Na 1-2”, “Nasal 1-2”, secondarily split up “nasal” (see Dietze 2000); Op. opercle: Pa. parietal bone: Pcl. postcleithrum; Pmx. premaxilla; p.no. posterior nostril; Pop, preopercle; Q, quadrate: Qj,quadratojugal: Ro. rostra1 bone: Sa. surangular; “Sbo”, “suborbital”: Scl, supracleithrum; Sop, subopercle; sorb.s.c, supraorbital sensory canal: “Spi”. ”spira- cular” bone: St, supratemporal. each other. Casts of this region show rows of clo- scribed for Carboniferous (Gottfried 1992). sely set teeth dislocated from the maxilla, but no Triassic (Veran 1996), and extant lower actinop- loose bony material in which the teeth were em- terygians, such as Polypterus (Fig. 2D) (e.g., Allis bedded. The same feature can be observed in 1922), Lepisosteus (e.g., Nelson 1973), and Amici specimens of Arnblypterus latus (e.g., MB. (e.g., Grande & Bemis 1998), but it is absent in f.3809~)that are preserved in nodules. Paramblypterus. The ‘coronoid’ process is corn- Granular teeth are present on palatal bones in posed of the surangular in the Carboniferous Pmarnhlypterus duvernoyi. Small, pointed teeth and Triassic taxa, of the prearticular in Poly- are present on the palate of Polypterus and are pterus, and of the dentary and surangular in Le- used for holding and manipulating prey (Clemen pisosteus and Amia (Nelson 1973). et al. 1998). Lepisosteus and Amia also have tiny The maxilla of Pararnblypterus is elongated teeth on the oral surface of the palate. In con- and narrow anteriorly, and greatly expanded pos- trast, the oral denticulate pavement is usually teriorly, thus covering most of the cheek region much reduced in favor of a complex of mobile (Fig. 4A, B). As can be seen in ventral view, the tooth plates on branchial arches in more ad- maxilla is attached to the premaxilla anteriorly. vanced actinopterygians (e.g., cyprinids, perco- to the dermopalatines medially, and to the ectop- morphs). terygoid medioposteriorly (Fig. 1A). No pro- cesses on the premaxillae could be observed by Jaw articulation, suspensorium, which they could have been fixed to the ethmoid and associated elements region. The ventral portion of the preopercle su- tures to the maxilla anteriorly and contacts the The lower jaw consists of a fairly narrow dentary subopercle posteriorly (Fig. 4A). Its anterodorsal and an angular which sutures at its posterior portion sutures with the “suborbital” series ante- margin (Figs 4A, B, 5C). Three small coronoid riorly, and dermohyal(s) and opercle posteriorly bones and a prearticular are present. A ‘coro- (Fig. 4A). Ventrally, the preopercle articulates noid’ process in the lower jaw has been de- with the quadratojugal (Fig. 4A). Thus, the cheek 128 Dietze. K.. Biological aspects of Pizrnmh/ypter.i~s
Fig. 5. A. Tccth ul Prrrrmiblypte- II/S d//L)fJrrfO>Ji (GPI M-MSX 1 9). B. Left premaxilla of I? rluvertzoyi in lateral view (CiPIM-MS8lh). C. Left lower jaw of P ,gelhem' in lateral view (GPIM-M2291). A. Scale bar = 1 mrn. R, C. Scale bar = 10 mm. Ang, angular: Cor. p.m.s.c D c coronoid bone: D. dentary; p.m.s.c. preoperculornandibular sensory canal; Prar. prcarticular. bones of Pr'rrr-arnb/yprc.i-~lsform a fairly tight ar- Mmdd be needed to prevent evasive prey from rangement. Th: preopercle is oriented less obli- escaping, ruling out predation on large animals. que than in o her fossil lower actinopterygiatis Thus. I assume that its diet consisted of small such as Mir77ia (Gardiner 1984) or Eloiiichrh!*s planktonic or benthic organisms which were ta- (Schindler 199:). ken in by suction feeding or grazing. Movements Since thc orimtation of the underlyin9 suspen- of the feeding apparatus during suction feeding sory apparatus is reflected by the position of the are mediated by musculoskeletal couplings preopercle (Lauder 1982). the suspensoriuin of (Laudei- l982), i.e. ligaments and muscles, and Prrrmib/yprer-i/s would have been oriented iiiore their associated bones. Unfortunately, none of vertically as \veil. A complete hyoniandibula these can be accounted for in Prrrarnblypterzts. could not be cbserved in any of the specimens In lower actinopterygians. such as Mimia examined, Par of it is preserved in specimen (Gardiner 1984) or Elonichthys (Schindler 1993), GPIM-5819 (Dretze 1999: fig. 2A) where its dor- lateral expansion of the buccal cavity was limited sal portion appears to be more upright than in by numerous immobile elements on the skull, .Preroiziscu/ils (Patterson 1982). The orientation the premaxilla and maxilla being firmly sutured of the hyomantlibula of specimen GPIM-5819 iic- to the other dermal skull bones, a not very mo- counts for a mlxe posterior articulation with the bile opercular series and branchiostegal rays, and neurocraniuni. thus suggesting an improved iiio- the oblique angle of the suspensory apparatus bility of the siispensory apparatus as was pro- resulting in a distiiictly postorbital jaw articula- posed for otht>r fishes by Schaeffer & Rosen tion (Lauder 1982). In advanced actinoptery- (1961). Features of the articulation Lvith the op- gians. force and velocity of mouth opening and ercIe could not be observed on either hyoniandi- dosing can be predicted using the distances of bula or medial face of the opercle. The opcrculo- joints to insertion sites of muscles and ligaments gular series is :omposed of opercle. subopercle. in relation to the distance of the joints to the tip about eight bi anchiostegal rays. paired lateral of the snout (Wcstneat 1994). In basal actinop- gulars and a single median gular (Fig. 4A. B). tei-ygians. such as Mitizia (Gardiner 1984) or Elo- No endoske1et;il elements of the ventral hyoid iiichrh~~s(Schindler 1993), the insertion site of arch are prcser ;ed in the specimens examined. the adductor musculature is very close to the joints. Thus. force of the bite was directly related Feeding - F econqtruction to mass and disposition of the adductor mandi- a n d coin pa r i so11 bulae inuscle (Schaeffer & Rosen 1961, Lauder 1982). The adductor inandibulae muscle of lower Teeth (Fis. SA) of Prrr.rtrizh!\.prrr-i/~are weak and actinopterygians consists of a posterolateral, a not inclined ba :kwards for the most part. which medial. and a suborbital component (Lauder Mitt. Mus. Nat.kd. Berl.. Geowiss. Reihe 4 (2001) 129
1980b), the latter being absent in Polypterus tion of the suborbital region accounts for an ex- (Fig. 2D). In contrast to species where the maxil- pansion of the underlying levator arcus palatini la is freed from the palatoquadrate, e.g., Amia muscle (Gardiner 1967) which mediates lateral calvu (Fig. 6B) and teleosts, the closed skull of movement of the suspensory apparatus, Frag- basal actinopterygians, such as Pteronisculus mentation of the dermohyal region indicates an (Schaeffer & Rosen 1961) or Muythomasia expansion of the dilatator operculi and / or ad- (Gardiner 1984), caused spatial constraints and ductor mandibulae. In Paramblyprerzrs, the dorsal did not allow for improvement of performance cheek region is not covered with dermal bones by expansion of muscles. The adductor mandibu- which might have contributed to additional mo- lae muscle was confined to the space between bility of the cheek and suspensory apparatus. palatoquadrate medially and maxilla laterally Since the size of the muscles depend on the pala- (Lauder 1982) as can be seen in the skull of toquadrate-maxillary chamber which in turn is Pteronisculus stensioei (Fig. 6A) (Schaeffer & reflected by the size of the maxillary plate Rosen 1961). In Pnramblypterus, teeth were pre- (Schaeffer & Rosen 1961), the size of the niaxil- sent along the complete margin of the maxilla lary plate suggests an expansion of the adductor indicating that all of the bone was exposed dur- mandibulae muscles in Paramhlypterus. In con- ing mouth opening. Therefore, a complex labial trast to other lower actinopterygians, such as Mi- fold system, as in Potypterus (Bartsch 1997), for mia or Moythomasia (Gardiner 1984), the bones creating a more effective suction funnel was of the snout region of Pammhlypterus are ar- probably not present in Paramhlypterus. Teeth ranged loosely (Fig. 4B) which allows a certain on the palate could have been used for manipu- mobility of that region and could be related to lating prey or grinding as in Potypterus. increased lateral versatility of the posterior In comparison to the basic pattern of lower cheek region. The mouth opening of Parrrmhlyp- actinopterygians, such as Mimia (Gardiner 1984) terus is more terminal, thus shortening the gape or Elonichthys (Schindler 1993), with a closed which would improve suction during mouth skull and oblique suspensorium, certain features opening (Liem 1993). (Fig. 2A) of Paramblypterus indicate a somewhat Two key features, i.e. neurocranial elevation derived situation. According to the orientation and mandibular depression, were suggested to of the hyomandibula (Dietze 1999: fig. 2A) and represent the basal method of mouth opening in preopercle (Fig. 4A), the suspensory apparatus actinopterygians (Lauder 1980a). Assuming that was less oblique than in other basal actinoptery- this general mechanisms occurred during feeding gians suggesting a greater lateral mobility. A of Pararnblypterus, a basal actinopterygian with a short maxilla reduces load of the upper jaws. closed skull, mandibular depression would have Furthermore, muscle insertion close to the joint been effected by retraction of the hyoid appara- accounts for a more rapid closing of the jaws tus mediated by contraction of the obliquus in- (Westneat 1994) in Paramhlypterus. Fragmenta- ferioris and sternohyoideus muscle via a mandi-
POP ,Sbo a.m Mx Pq a.m Pq D D A n Fig. 6. Cross scction through head. A. Pteroniscirlus stensioei. B. Anzia calvn. Adductor musculature shaded (modified after Schaeffer & Roscn 1961). am, musculus adductor mandibulae; D, dentary: Pop, preopercle; pq, palatoquadrate: Sho. suborbi- tals. 1.30 Dietzc. K.. Biological aspects of Prruariihlyptenis bulohyoid ligarient at the onset of the expansi1.e drate and cheek as in Amia (Grande & Bemis phase (Lauder 1980a. 1982). Contraction of the 1998) and therefore could not be moved inde- anterior epaxi 11 musculature would have ele- pendently. The adductor mandibulae muscle was vated the an:,erior vertebrae and the head still confined to thc palatoquadrate-maxillary (Tchernavin 1 147). Movement of the opercle chamber as in Pteroniscrdiis (Fig. 6A). Advanced and suboperclc would have been accomplished teleosts and Aniia can generate negative pres- by the dilatator and adductor operculi muscle, sures of 400 to 600cm H20 (Liem 1978) and allowing limited control over opercular move- 120 cm H20 (Osse 1976) within their buccal cav- ments during ft:eding (Lauder 1980a). Activity of ities. respectively. In contrast, negative pressures the levator arcus palatini muscle would have of fossil lower actinopterygians were probably mediated lateral movement of the suspensory small. about SO cm H20 (Lauder 1980a), and apparatus (Lailder 198Oa). According to the water tlow through the mouth cavity during so mew h a t deri ve d condition in Prr rar i I h l~sprer.z i.s feeding may have been primarily controlled by due to a possit le expanded mandibular muscula- body velocity in Paraniblyptenrs. ture and less oilique orientation. mobility of the suspensory apparatus should have been im- proved. Adduction of the opercle would have Locomotion occurred at the start of the buccal expansion and the final phase following closure of the jaws at Water is a dense. viscous medium that places se- the end of the compressive phase (Lauder vere constraints on the function and design of 1980a). Operciilar abduction which is mediated effective propulsive mechanisms (Lindsey 1978, by the dilatato:. operculi muscle would have oc- Keif 1982, Webb 1982. Lauder 1989, Videler curred at the onset of the compressive phase. 1993). For the propulsion in water, weight sup- Control over opercular movement. which is con- port is not a dominant factor (Webb 1994). Lo- trolled by the adductor and dilatator operculi comotion is affected by buoyancy, drag or fric- muscles. might have been improved given a pos- tion. stabilizing factors, and the power needed to sible expansioii of these muscles. Occlusion of generate the desired movement most efficiently the jaws shoultl have been more effective if the in dealing with these (Webb & Blake 1985). Fea- adductor mandibulae was enlarged. Suction tures such as shape and size of body and fins, could have betn improved based on a more ra- positioning and flexibility of the fins, squama- pid jaw closing and the mouth opening being or- tion. and the degree of ossification of the verteb- iented more ar teriorly. thus shortening the gape. ral column all interact to influence performance The mouth of lower actinopterygians. such as (Biiss 1982, Webb 1982, Webb & Blake 1985, Di Miriiirr (Gardir er 1984) or Eloriichrh~..~(Schind- Canzio 1985, Weihs 1989). ler 1993). opens in a grin. which allows Lvater to Axial mechanisms, i.c. body and / or caudal enter at the sides of the mouth. thus reducing fin. are associated with large muscle mass, thus sucking speed (Alexander 1970). However. a being able to convert more than 90% of muscle more vertical irticulation of the hyoniandibula energy into thrust energy (Webb & Blake 1985). with the neuro :ranium allows for anterior move- In contrast. the other median and paired fins are ments of the suspensorium (Schaeffer 8: Rosen associated with little muscle mass and can be 1961 ). In Purtr, nh1yprer.ri.s. this mechanism might used for slow swimming (Webb & Blake 1985). have served to fill in the corners of the open Performance of a heterocercal caudal fin de- mouth, which i i turn improves suction. pends on its aspect ratio, i.e. length of the span Essentially. t iis is thc mechanism described for divided by the length of the chord (Di Canzio fo1ypierii.s (Fig. 2B. D) and Lepisosreirs (Lauder 1985) or span of the fin squared divided by its 1980a). where inly a single musculoskeletal cou- area (Lighthill 1969, Videler 1993), and the size pling exists for mandibular depression. i.e. by the of the ventral lobe of the caudal fin (Thoinson & sternohyoideus muscle isin the niandibulohyoid Simanek 1977). Median fins serve primarily to ligament. In cc ntrast to Anzia. an interopercular reduce rolling action of the body during turns bone. which is the key element for transmitting (Di Canzio 1985). whereas paired fins, mostly thc pull of thl: levator operculi muscle to the the pectoral fin. function in attitude control, mandible. is i bse n t i n bas a1 act inopt e r y gi a n s. turning control, and braking (Keast & Webb such as Po1J~pl“crii.s.Lc1pisosreii.s (Lauder 1980a. 1966. Di Canzio 1985). 1982). or Prrrniirh1J.i’tc”zr.s. The maxilla of hrrrr- Body scaling. which has often been regarded tnhl~~prerrrswa ; not freed from the palatoqua- as protection from predators, scrves as a coun- Mitt. Mus. Nat.kd. Berl.. Geowiss. Reihe 4 (2001) 131
Fig. 7. A. Restoration of PnrnmD/ypferus drrverrznyi (GPIM-MS819 and GPIM-M5816). Teeth omitted. arrows indicate position of transverse sections below. Scale bar = 10 mm. B. Transverse sections of the three-dimensional model of P dtr~~niovi. teracting element during swimming (Starck Its body is laterally compressed and according to 1979). Scales arranged at an angle of about 45 to profiles of the three-dimensional model, lateral the longitudinal axis of the fish allows shearing compression of the body increases posteriorly between rows and prevents torsion of the body (Fig. 7B). Vertical and horizontal fineness ratios during locomotion (Pearson 1982). The size of (Blake 1983) are about 55 and 81, respectively. the scales (Aleev 1969) and their thickness affect The reconstruction of the whole fish shows a lateral movement (Boss 1982). Peg and socket fairly slender body with only a little hump pos- articulation affects flexibility of the skin (Pearson terior to the head. LH, i.e. the distance of the 1982), thus reducing the effectivity of propulsion nose to maximum depth of the body (Webb (Webb & Blake 1985), but also serves to main- 1988), divided by the length of the three dimen- tain architectural integrity of the scale rows by sional model is 0.23. preventing adjacent scales to slip during com- Pclranzhlypterus bears a cover of ganoid scales pression (Pearson 1981). Moreover, they in- (Fig. 7A) with peg and socket articulation crease the dead weight and density of the fish (Fig. 8s).The peg represents about 10% of the which in turn increase inertia (Webb 1982, 1996) overall height of the lateral scales. Along the if features to increase buoyancy, such as fat or lungs, are absent. The vertebral column is impor- tant in stabilizing muscle operation and resisting deformation and deflections caused by locomo- tion, which is related to the degree of ossifica- tion of the vertebrae (Boss 1982).
Body form, squamation, B and ossification of the vertebrae A Fig. 8. Pauan~hlyptenisdirveunoyi, detail of squamation. Ante- rior facing right. A. Ornamentation. B. Peg and socket articu- du- Trunk length of specimens of Paramblypterus lation, shaded area indicates articulation surface. Scale bar = vernoyi examined here ranges from 19-220 mm. S mm. 132 Dietze. K., Biological asuccts of Paranzhlviifrriis lateral line, 4; i 2 scale rows between supra- Contrary to Pearson (1982), a relationship of cleithrum and the inclination of the scales ante- scale rows to the number of vertebrae, and thus rior to the caudal fin are present. Below the lat- niyomeres. appears to be 1:l in almost all fossil eral line. the dxsoventral height of the scales on as well as living lower actinopterygians (e.g., Jes- the body decrt ases progressively in l? dii\,errioJli. sen 1968. Bartsch 1988, Gemballa 1995, Grande According to Breder (1926). this feature indi- & Bemis 1998). This pattern has also been de- cates a flat be1 y. Unlike other lower actinoptery- scribed in Seniionotiis (Olsen & McCune 1991). gians. such as Miniia (Gardiner 1984) or Elo- Outgroup comparison with the osteolepiform Fiidirhys (Schir dler 1993). scales of P dirvernoyi Eiisrheriopreroiz (Jarvik 1996) further corrobo- bear only veiy scarce ornamention (Fig. 8A). rates an earlier appearance of this relationship Moreover, not all the scales on the body are ser- than suggested by Pearson (1982). Cht.irolepis, rated. and the area on the body bearing orna- which has different scales than the remainder of mented scales appears to decrease during onto- the basal actinopterygians, has a higher number geny (Dietze 1998). As mentioned earlier. of scales per vertebra (Pearson 1982, Arratia & specimens of E! dir~.eriio1~3iwere flattened during Cloutier 1996). According to Gardinei- (1984: fossilization. Fratures of the axial skeleton could 366. 386). Miniia roonibsi has about 25 vertebrae not be observed in any of the disarticulated spe- and 75 scale rows. However, according to Gardi- cimens of eithc r P di11~crrzo~.ior l? grlherti. Thus. ner's figure 123, the overall number of vertebrae it is likely for these elements not to have been appears to have been higher than that. If the ossified or onl! weakly. general pattern of 1: 1 was present in Paranzblyp- In general. cata on the axial skeleton of lower rer~its vertebral column would have bcen com- actinopterygiar s. such as Eloriiclirlij~.~(Schindler posed of about 42 posteriorly in length decreas- 1993). is hard to come by. because their body is ing vertebrae, indicating the number of covered with ganoin scales. In species where mymeres present. these elements can be observed. they consist of dorsal and ver tral arches. vary in the fusion of Fins elements and 1he degree of ossification. and for the most part ;lo not form true centra (e.g.. Al- Pnrrrr1ib1yprerrr.c has a heteroccrcal tail with a dinger 1937. Lowney 19XOa. Kazantseva-Selezne- terminal flap on its dorsal lobe (Figs 7A, ZOA). va 1981. Gardi ier 1984). For the three dimensional model, the hetero- As yet. ossifi-d centra in lower actinopterygians and hypocercal angles of the lobes are 28 arid have been deslxibed for the Late Carboniferous 34. respectively. The aspect ratio, i.c. span species Microh rp lolepis ( sy n . Hoplolep is) o 1'0iden squared divided by the area of the fin (Lighthill (Baum & Lunc 1974. Lowney 1980b). the Middle 1969. Videler 1993), is about 2.4 (Fig. lOA), Permian to Triassic species Pygopteriis riielsrtii which is similar to that of other basal actinoptcr- (Aldinger 1937). the Early to Middle Triassic spe- ygians (Fig. 10B-H). The dorsal margin of the cies R~rsrralosc,niriskochi (Stensio 1932. Nielsen caudal fin is covered by four or five basal scutes 1949). the Middle to Late Triassic species Pelto- followed by a series of elongated scutes which pleirriis splerrd~m(Laerm 1979a). and the Late become progressively smaller caudally. The dor- Triassic genus ;iirsrodirs (Schaeffer 1967a). sal and anal fin are broad based, of triangular In these spezies. ccntra are either confined to shape. and positioned in the posterior part of the the region posterior to the head (ik'icrohaplole- body (Fig. 7A). The pectoral and pelvic fins are pis) or to the caudal region (P~gcjpterirsand Pel- small. rectangular in outline, and broad based. topleiirirs). wh xcas T~rrseotfiisand Airsrrnloso- The pectoral fin is inserted rather dorsally. The nilis have cen ra throughout the body (Laerm pelvic fin is inserted more ventrally, located 1979a). Centra of lower actinopterygians. which about midway along the body. Nothing is known have not been assigned to a certain species. have of the endoskeletal elements in Pararnhlypterus. also been found in Late Paleozoic deposits of However. Watson (1925) described the hinder North Americ: (Schultze & Chorn 1986). Even part of the pectoral girdle of Arnhlypterus, the though feature ; of the vertebral column of Parn- sister taxon of Pnmmhlypients. as being very si- iiil~l~~p1rriisarc not known. it is likely to have milar to. but less massive than lhat of Acipenwr. had a persistent notochord as in other lower acti- Apart from the lepidotrichia, the only detail ot nopterygians. such as Ptrloeonisairii or Birgerin. the pectoral fin is a drop shaped marginal fin ray probably sirnikir to that of Acipemer. (Remane (Fig. 9E. F). According to Jessen (1972), this ele- 1936. Schaeffer I967b) (Fig. 9A). ment is composed of fused lepidotrichia. In Pam- Mitt. Mus. Nat.kd. Berl.. Geowiss. Reihe 4 (2001) 133
nc r. a d.r
C D
M.r.b
M.r.b ,/” f‘ LeP / n I / /
I E F Fig. 9. A. Acipenser sturio, vertebral column, anterior facing left, cartilage black, bone hatched (modified after Goodrich 1930. Marinelli & Strenger 1973). B. A. siwio, endoskeleton of the pectoral fin, dorsal view (after Jessen 1972). C. A. sI/rlrio. delail of the caudal fin (modified after Bartsch 1988, Lauder 1989). D. A. srurio, endoskeleton of the pectoral fin. medial view (after Jesscn 1972). E, F. Pararnhlypterus dzivernoyi, detail of the pectoral fin (PMNB-WOR27 and GPIM-M2894). Scale bar = 5 mm. bd, basidorsal; bv, basiventral; d.I.1, dorsal longitudinal ligament; d.r, distal radial; id, interdorsal; fl.v, inusculus flexor ventralis: iv, interventral; Lep, lepidolrichia; I.s, subvertebral ligament; M.r.b, base of marginal fin ray: mtp, metapterygiuni: nc. neural chord: nch, notochord; propt, propterygium; r.a, rib attachment; sn, supraneural; r, radial. mblypterus, all of the fins are composed of clo- simple flexor ventralis muscle (Bartsch 1988). In sely packed fin rays and bear fringing fulcra on addition to a complex flexor ventralis muscle, a their leading edges. hypochordal longitudinalis muscle with lateralis Contrary to Lauder (1989), the heterocercal superficialis muscles inserting on the head of the tail of Acipenser (Fig. 9C) does not lack intrinsic fins has been described in Lepisosteus (Schmal- caudal muscles, but has a two-partite flexor ven- hausen 1912, Bartsch 1988), however see Gem- tralis muscle (Bartsch 1988). Polypterus has a balla (1995). The caudal musculature of Anzin is 133 Dietze. K.. Biological aspects of Pnvnrnh/.ypterus
Pectoral fins of Lepisosfeiis and Amia are simi- lar to those of Acipenser, but the lepidotrichia are thickened proximally (Jessen 1972). These thickened ends represent insertion sites for the pectoralis musculature allowing for a greater var- iation of pectoral movement (Jessen 1972). In the Late Triassic species Birgeria graenlan- dicrc, the parhypural bears a process, which re- sembles the hypurapophysis of certain teleost fishes. where the process is the insertion site of the hypochordal longitudinalis and the flexor \,entralis muscles (Niclsen 1949, Bartsch 1988, Lauder 1989). Features of the endoskeleton sug- gesting differentiation of musculature of the paired and median fins have not been described for Devonian to Lower Triassic lower actinopter- ygians. It appears likely that differentiated fea- E. F tures were absent in the skeleton of the fins of Pclr-ciiiih!\.ptrr-rrs and that the paired fins, as in Acipeiisrr-. lacked the thickened ends on the lepi- dotrichia. which arc the insertion sites for the pectoralis musculature. Thus, the construction of the fins probably allowed only restricted move- c; H ment of the lepidotrichia without being able to expand and collapse fin area. and closely packed fin rays reduced the active mobility of the indivi- dual rays in a11 fins.
Locom o t o r capa b i 1 it y The body of Prrranihlypterus diivernoyi is com- pressed laterally (Fig. 7A, B) which reduces yaw. Its vertical fineness ratio is similar to that of differentiated further in having a large flexor cruising fishes, but higher than that of species ventralis musl:le and antagonistic interradialis designed for accclcration (Blake 1983, Webb and supracarir alis muscles to collapse or cspand 1988). A hump about 6OYO posterior to the snout the fin (Bartsc? 1988. Lauder 1989). and rapid reduction of cross section afterward
In Acipecise I. enlarged marginal rays embrace minimizes drag (Wcihs & Webb 1983), which is the paired lepidotrichia of the pectoral fin (Jes- not the case in P rluvernoyi. Presumably, about sen 1972). Towards the base of the fin. the lepi- 42 vertebrae were present along its body axis, dotrichia diverge and form a gap where the which is not suitable for an anguilliform mode of propterygium. the radials. and metapterygium lie propulsion. (Fig. 9B. D). One portion of the pectoralis nius- Scale rows of Paroniblypter~is duvernuyi are cle inserts on the ventral lepidotrichia. and the arranged at an angle of about 45 degrees to the other portion 3n the dorsal lepidotrichia (Jessen horizontal axis which allows shearing between 1972). Thus. alduction and abduction of the fin rows and reduces torsion of the body during lo- is mediated t-y contraction of the muscles at- comotion (Pearson 1982). Frequently, the squa- tached to the lorsal and ventral portion. respec- mation pattern in ganoid fishes has been consid- tively (Jessen 1972). The anterior portion of the ered to restrict the performance of lateral pectoralis mu: cle inserts ventrally and dorsally movement (e.g.. Boss 1982, Lund 1967). How- on the marginal ray. which is formed by fusion ever. this is not true for either Polypferirs or Le- of several a iteriormost lepidotrichia (Jessen pisnsfc~tis(Gcmballa 1995). Whereas scales are 1972). These musclcs are antagonistic to each more or less iinmovable against one another dor- other and me( iate vcntral and dorsal nio\mnent soventrally (Sewertzoff 1926), shearing ranges of the marginal ray (Jessen 1972). from 42% to 96% and 73% to 88% between Mitt. Mus. Nat.kd. Bcrl.. Geowiss. Reihe 4 (2001) 1.35 scale rows on the concave side in Polypterus and son & Simanek 1977). Caudal fins suitable for Lepisosteus, respectively (Bartsch & Gemballa cruising and sprinting, so-called lunate tails, have 1992, Gemballa 1995). Moreover, scales of Poly- aspects ratios of about 13 (Videler 1993). An as- ptercis have been supposed to be involved in en- pect ratio of 2.4 in P hvernoyi compares to ergy storage for respiration (Brainerd 1994) and those fishes that are specialized for acceleration represent a well-designed means for propulsion (Webb 1988). Posterior lateral compression im- (Sewertzoff 1926, Pearson 1981). proves hydromechanical efficiency and creates a For transient swimming at low to moderate large momentum as well (Lighthill 1970). Neck- speeds, drag becomes the dominant resistance ing anterior to the caudal fin reduces recoil component with body area as restraining feature (Lighthill 1969). Contrary to Pearson (1982), the (Webb & Blake 1985). Ganoine scales, which caudal scale inversion does not weaken the cau- cover all of the body in Paramblypterus, increase dal peduncle, but more likely served to prevent dead weight which in turn increases inertia, i.e. if torsion (Bartsch 198s). mechanisms to increase buoyancy are absent. Locomotor capability of Parnmblypterirs dii- Fulcra on the leading edges of the fins reduce vernoyi during swimming could have been one resistance. An incompletely ossified vertebral of moderate speeds, combined with sprints and column has been supposed to result in slow turns as means for escape, but without the ability speeds caused by low amplitude of axial move- of precise maneuvers. This agrees with its as- ment (Boss 1982). However, this does not seem sumed feeding habit. Since Pararnhlypteriis has true for Recent Dipnoi, Latimeria, or Acipenser, small and weak teeth, it could not prey on large all of which have a persisting notochord (Laerm animals. Therefore, a diet of small planktonic or 1979a, b). benthic invertebrate organisms is likely. Tn fishes The paired fins of Paramblypteriw are broad with few mobile elements on their skull, water based, fairly large, and muscle insertion on the flow is primarily controlled by velocity (Lauder lepidotrichia probably allowed for upward and 1982). Therefore, a fairly steady mode of loco- downward movements only. According to Keast motion would have been required for breathing & Webb (1966), this limits the performance of and feeding in Purumhlypteriis. A flat belly is turning, attitude control, and braking. Moreover, also present in Acipenser and Amia, but it is ab- fins that cannot be collapsed increase drag sent in forms that live in open waters, such as (Alexander 1970). The median fins appear to be salmon or trout. Apparently, a cambered body posterior to and not over the center of mass in reduces drag in close proximity to the ground Paramhlypteriis, the latter of which would be and represents and adaptation to bottom-dwell- needed for precise maneuvers (Webb & Blake ing (Morelli 1960, 1983). A tentative reconstruc- 1985). However, the median fins are positioned tion of the habitat of Paramblypterzis would be close to the caudal fin which adds to the area of the littoral or bottom zone of a lake or river. the caudal fin, thus improving acceleration for Intermittent excursions into deeper waters are spurts. Caudal fin ray stiffness and position were suggested by specimens found occasionally in se- probably not greatly alterable during locomotion diments corresponding to thc profundal facies of except as direct consequence of myotomal con- the lakes. traction (Lauder 19S9), but stiff caudal fins have been shown to increase thrust (Katz & Weihs 1978). Conclusions The position of the anal and dorsal fins in the posterior part of the body, and the large hyp- Based on a three-dimensional model of Porn- axial lobe on the caudal fin result in high fric- mblypterus and comparisons to other extant low- tional resistance in the posterior part of the body er actinopterygians, such as Polypteriis, Lepi- in PararnbIypterus. This is disadvantageous for sosteeus, Aripenser, or Amin and fossil lower covering longer distances effectively, but im- actinopterygians, such as Pteronisculus, Elo- proves the performance of turns and sudden nichthys, or Microhaplolepis, function of the spurts (Webb & Blake 1985). A terminal flap feeding apparatus and patterns of locomotion of has been considered to improve the performance Pararnhlypterus are interpreted. Certain modified of the caudal fin by preventing it from stalling features, such as a less inclined suspensory appa- (Di Canzio 1985). A reduced heterocercal angle ratus, loosely arranged snout bones, the mouth results in slower speeds, but is related to a opening being oriented further anteriorly, frag- powerful turning moment (Lighthill 1970, Thom- mentation of the dermohyal and “suborbital” re- 1-36 Dietre. K.. Biological aspects of PnrrrrnhlypreruA gion, and an :nlarged palatoquadratc-niasillar!, Xlewnder. R. Mc N. 1970. Functional Design in Fishes. 160 pp. Hutchinson University Library. London. chambcr. arc present in Prrrcrriihl~prer~iis.This Allis. E. P. 1922. The cranial anatomy of Po/yprerin with spe- may have improved suction feeding by allowing cial reference to Po!\prm,s bichir. - Journal of Anatomy for expansion of undcrlyinz muscles and/or in- 56: 180-294. Ankcr. G. f.1974. Mi)rphology and kinetics of the stickle- creasing the mability of the skull. The locomotor hack. Gt/s/[,ro,srcir5rrcirlwrirs. - Transactions of the Royal capability of P~i~(r~iibl~,i~t~r//.~appears to have Society of London 32: 31 1-416. been one of nioderate steady swimming speeds. Arratia. G. K: flouticr. R. 1996. Reassessment of the mor- phology of C'/ioiro/c/iis ctrnrrrlcrz.sis (Actinopterygii). In combined witl-, sprints and turns as means for Schultze. H.-P. 6 Cloutier. R. (4s). Devonian Fishes and escape. but wiih a limited ability of precise man- Plants of Xtiguasha. Quebec: 165- 197. Verlag Dr. Pleil. lunche en. euvers. Xri-atia. G. & Schultre. H.-P. 1991. Palatoquadrate and its The weak te-th present in P~r~nriibl~~ptrn/.ssuz- ossifications: Development and homology within os- gest a diet of ;mall or soft-bodied planktonic or teichtliyans. - Journal of Morphology 208: 1-81. Bartsch. P. 198s. Funktionelle Morpliologie und Evolution benthic organ siiis. 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