Ne\T Genus and Ne\T Species of Bakevelliidae (Pterioida, Bivalvia) from the Middle Permian of Chios (Greece)

$Ne\T Genus and Ne\T Species of Bakevelliidae (Pterioida, Bivalvia) from the Middle Permian of Chios (Greece)$

Rivista Italiana di Paleontologia e Stratigrafia volume I uó pagrne 359-368 Novembre 2002

MARM ARON I A AN G I O LIN II, NE\T GENUS AND NE\T SPECIES OF BAKEVELLIIDAE (PTERIOIDA, BIVALVIA) FROM THE MIDDLE PERMIAN OF CHIOS (GREECE)

CRISTIANO LARGHI

Receit,ed February 21, 20A2; accepted July 23,2002

Key-roords: Chios, Greece, Bivalvia, Bakevelliidae, Guadalupi- lntroduction an, Middle Permian. The study of Permian bivalves of the Tethyan Riasswnto. I "Calcari a Gymnocodiacee" guadalupiani (Permi- province was neglecred compared with other fossil ano Medio), affioranti nella parte nordorientale dell'isola Greca di Chio (Egeo orientale), sono tra i più fossiliferi della Tetide occidentale. groups such as foraminifers, conodonts and bra- Essi contengono ricche associazìoni a coralli, brachiopodi, molluschi, chiopods. The majority of the limited literature address- alghe calcaree, foraminiferi e ostracodi, tuttavia, mentre i brachiopodi es the Eastern Tethys (see Hayami 8t Kase 1977; e i foraminiferi sono stati oggetto di sistematici, studi scarsa atten- Nakazawa & Newell 1968; Wanner 1922, 1.940); Permi- zione è stata dedicata, sino ad ora, alle faune a molluschi. an bivalves in the western parr of the Tethyan Nel presente lavoro viene istituito il nuovo genere Marmaronia province con specie tipo Marmaronia angiolinii n. sp. per comprendere alcuni s-ere described by Gemmellaro (1892), Termier et al. bivalvi della famiglia delle Bakevelliidae King, 1 850, rinvenuti nelle suc- (1977), Boyd & Newell (1979) and recently by Dickins cessioni del Guadalupiano medio della località di Marmaro. Marmaro- (1999\. nia angiolinii n. gen. n. sp. é fortemente inequivalve, con valr.e clie dif- In the last few decades the importance of Permian feriscono per convessità, sviluppo degli umbonì e ornamenrazione. La bivalve faunas valva sinistra presenra un solco radiale che partendo dall'umbone in the fields of palaeoecology. palaeobio- giunge al margine ventrale ed é ornata da robuste coste radiali; la valva geography and biostratigraphy has been recognized. destra presenta rughe di crescita concentriche e debolissime coste radi- The discovery of a connecrion between the cold ali visibili nella parte posteriore della conchiglia dei primi stadi di water Eurydesma fauna and the late Paleozoic Gond- crescita di alcuni esemplari; entrambe le valve mostrano un'ala posteri- wanan glaciations, ore esPansa. for example, was useful for the inter- Nel presente lavoro vengono inoltre discusse brevemente due pretation of Permian climate changes, as well as for ipotesi riguardanti un possibile adattamento epi- o endobissa to di Mar- global correlations (Harrington 1955; Dickins L957, mdronLd,. 1978, t984). Moreover, the bivalve assemblases associared s/irh Abstract. The Guadalupian (Middle Permian) "Gymnocodi- acean Limestones" cropping out in rhe north-eastern part of the Greek the transgression on the mid-Permian unconformity, are island of Chios (eastern Aegean Sea) are amongst rhe most fossilifer- found in many parts of the world, including Australia, ous in the western Tethys. They contain rich assemblages of corals, New Zealand, the northern Russian Region, the central brachiopods, molluscs, calcareous algae, foramìnifers and osrracods. and southern United States and recently Oman (Dickins Scant attention was given till now to mollusc faunas compared with 1997, 1999). These faunas characrerised brachiopods and foraminifers. In rhe presenr paper the new genus are by the Marmaronia, with type-specìes M. angiolinil n. sp., is established to appearance of new pecrinacea and permophorids, and by distinguish some bivalves of the Bakevelliidae King, 1850, from the the development of multivincular pterioid forms such as middle Guadalupian successions of the Marmaro locality in Chios Babevellia (Dickins 1997). Island. From a biostratigraphic point of view, some gen- M. angiolinii n. gen. n. sp. is strongly inequivalve, with valves differing in convexity, umbo developmenr and ornamentation. The left era discovered for the first time in the Permian succes- valve shows a radial furrow running from the anterior part of the sions have acquired roday a grear imporrance nor only in umbonal region anreroventrally and is ornamented by strong radial the Permian, but also in the Lower Triassic. costae; the right valve is ornamented by concentric sculpture and by Some species atrribured to rhe genvs To,wdpterìa thin rugae in the first growth srages of the posterior part of the shell. Both valves have a *ide posrerior wing. Nakazawa & Newell, 1968, for example, have now a Two hypotheses concerning the epi- or endobyssate adaptation great biostratigraphic importance in the Tethyan of Marmaronia are also discussed briefly in the present paper. province. In particular T. schytica (Wirth) was men-

Dipartimento di Scienze della Terra, via Mangiagallì 34,20133 Milano, Italy, e-mail: crì[email protected] 364

is located in the eastern Aegean Sea a few kilometres from the Turkish coast of the Karaburun peninsula (Fig. 1). According to many authors (Herget & Roth 1968, Besenecker et al. 1968, 1,971) two tectono-stratigraphical units can be distinguished on Chios Island: an autochthonous unit and an overthrust of an allochthonous unit. The lower unit consists of a thick Palaeozoíc succession, composed of terrigenous rocks, cherts, vol- canics and limestones (the last dated-from Silurian to Carboniferous), which is overiain by a Meso-Cenozoic succession. The allochthonous unit comprises an Upper Carboniferous to Upper Permian sequence, underlying a Liassic shallow-water carbonate platform. Red siltstones of uncertain age separate them (Kauffmann 1969; Bese- necker et al. 1968). The study area described in this paper belongs to the allocthonous unit. A Middle Permian carbonate sequence crops out specifically near Marmaro, Agrelias and Parpanda. These very fossiliferous limestones were called "Gymnocodi- acean limestones" (Gymnocodiaceen-Kalke) by Kauff- mann (1969) (Fig.2). Fossils consist of calcareous algae, corals, molluscs, echinoids, brachiopods, fusulinids, smaller foraminifers, ostracods and conodonts. -tP Flajs et al. (1,996a) provided a list of the most fre- 0 D quent algae which are Gymnocodium belleropbontis, Per- ou m o c a I c w I w s t e xa,n urrî., M i z z i a rt e I e b itan a an d P s e w d oo erm i - úQ porella sodalica, but until now no systematic study of these algae has been produced. On the contrary the systematics of the rich assemblage of silicified brachiopods Fig. 1 - Location map of Chios ìn the Aegean area. from some levels of the "Gymnocodiacean limestones" near Marmaro, was studied by Grant (1,993). An age for the "Gymnocodiacean limestones" was the Eastern Tethys deposits tioned for the first time in given by Kahler (1987) who studied foraminifers sam- the of western China (Wirth 1936) and later in pled by Kauffman during his doctoral thesis. FIe men- (Broglio Loriga 1983). Later this Dolomites et al. tioned the presence of the foraminifers Nankinella infla- was in the basal Lower Tri- species presence confirmed ta and Eoverbeehina intermedia, that correspond to the south-western (Chen 1980). Today Z assic of China Middle Permian, in the "Gymnocodiacean limestones" of schytica is considered an important index for Lower Tri- the Marmaro section. assic global correlations (Shen et al. 1995, Yin Er Tong According to Flajs et aI. (1996a) the "Gymnocodi- 1998; Kozur 1998). Today the knowledge on bivalves in some areas of the Tethys is almost non-existent and according to Yancey (19S5), a high degree of endemism shown by some Permian faunas could be only the result of lack of î knowledge. Perhaps new studies on bivalves will permit to discover new taxa useful for the correlations of Per- r\É, t mian benthonic faunas. R This work is part of wider investigations on the I rr<- Palaeozoic successions of Chios Island, involving many / researchers from the Dipartimento di Scienze della Terra I L:H orkì lt of the Università di Milano and from other Italian and I European lJniversities. )utcfops ol "Gy-'mnocodiaceau Lilresl nsu Besenecker el al. I 97 I ) ii"i

Previous works and geological setting. Ftg.2 - Simplified geological map of northeastern Chios (rectangle in fig. 1) showing the investigated area and the outcrops of "Gym- The island of Chios, one of the largest in Greece, nocodiacean limestones" (from Flajs et aL.7996a, modified). Marmaronia angiolinii 361

acean limestones" exposed in the Marmaro section belong either to the Verbeekina Zone or to the NeoschwagerinaZone, which correspond to the middle Guadalupian. No work was devoted to the mollusc faunas uo ro now: K The Marmaro section.

One of the best exposed outcrops of the "Gy-- nocodiacean limestones" is located on rhe easrern side of the Marmaro beach (Fig. 2). The Marmaro secrion (Fig. 3), approximately 32 lJ nit meters thick, was divided into 5 Units by Flajs et al. (1,996a). The stratigraphy of the present paper is based on that work. Unit 1 reaches a thickness up to rhree meters. This unit is composed of dark grey to black or brown thin-bedded limesrones, which include mudstones, wackestones, packstones, floatstones and frame- lJnit stones. It consists of 30-60 cm thick individual layers of yellow-brown limestones with corals (Multithecopora sp.) and intercalations of brachiopods and black limestones with molluscs and foraminifers; the amount of corals decreases towards the top of the unit, while at the base corals form biostromes. Foraminifers, calcareous algae and a variety of encrusting micro-organisms form w the bulk of the microfossiliferous assemblage. Some coquina beds suggesr rempestite deposits and red and Iw green algae, which locally form algal packstones, indi- w cate moderate water depths (Flajs et aI. 1996b). Unit 2 consists mainly of grey to brown calcare- w ous marls up to 2 m thick. Abundant richtofeniid brachiopods, many bryozoans, echinoderms and kirkby- I*egg*d acean and bairdiacean ostracods, which are supposed to indicate calm warer conditions (Flajs et aI. 1996b), are I trpe scrics trtr Llmestone present locally. t hvcls Richthofeniids in the upper levels form a massive Marl ['lrrnrarrnia m reef limestone up ro 6 m thick, called Unit 3. K Calcareous marls with à yery high fossil conrenr ffi Coquinoid I e\'e i (Unit a) separaîe the richthofeniid bank from regularly bedded limestones containing calcareous algae and oncoids (Unit 5) which represent the end of the Mar- Fig. 3 - Stratigraphical section of "Gymnocodiacean Limestones" maro Permian sequence. outcropping in rhe Marmaro bay (from Flajs et al. 1996a, Many specimens of a single species of bivalve can modified). be collected in all the units of the "Gymnocodiacean limestones", except for Unit 3. Systematics analyses showed that these bivalves belong to a new genus and a stones and marls of Unit 1 (the Stratum Typicum o{ new species for which the name Marmaronia angiolinii ìs Marmaronia angiolinii n. gen. n. sp.) suggest calm waters introduced. The Types of Marmaronia angiolinii n. gen. and a lagoonal environmenr, but probably the coquinas n. sp. were collected in the upper part of Unit 1 (fig. 3). of this unit indicate that this environment was subjected Some specimens of Marmaronia angiolinii to periodically heary and deep-reaching storms. (MPUM8605A-D) were collected also by L. Angiolini Bivalved specimens of Marmaronia are present in the and L. Carabelli (Dipartimento di Scienze della Terra, mudstones of Unit 1, together with spines of large Università degli Studi di Milano) in the locality of sam- quasi-infaunal brachiopods. On the contrary, in the ple USMN9592 of section II, described by Grant (1993) coquinas valves are always disarticulated, often selected in the region of Agrelia (Parpanda). by transport (actua11y some fossil concentrarions are Faunal and sedimentoloeical features in the mud- composed exclusively of right valves). 362 C. Larghi

Systematic Paleontology. imens in which the important internal characters are often not visible. Illustrated and described specimens are housed in the collec- tions of the Dipartimento di Scìenze della Terra, Università degli Studi di Milano, Museo di Paleontologia, via Mangiagalli 34, Milano, Italy Genus Marmaronia n. gen. (numbers with the prefix MPUM). Type species,4larmaronia angiolinii n. sp. Phylum Mollusca Etymology. Genus named from the locality of Marmaro Ciass Bivalvia Linné, 1758 (Buonanni, 1681) (Mcrppcrpo), island of Chios, Greece. of genus. At present the genus is composed Subclass Pteriomorph a Beurlen, 1.9 4 4 Composition the only by the type species Marmaronia angioLinii n. sp. Order Pterioida Newell, 1965 Diagnosis. Shell small, oblique, prosocline, from rhombic to Suborder Pteriina Newell, 1965 trapeziform, inequilateral and posteriorly alate, strongly inequivalve; shell sinuated for byssus in the antero-ventral margin. Superfamily Pteriacea Gray, 1.847 (1820) Left valve strongly convex, with prominent umbo ornamented radial furrow Family Bakevelliidae King, 1850 by strong radial costae, anterior not lobate but with a running from the anterior part of the umbonal region to the ventral margin. Right valve less convex, with prominent umbo, without a true anterior auricle, but with an anterior lobe depressed in comparison Preliminary remarks with the umbonal region; right valve ornamented by a concenrric and feq thin, filiform costae in the posterior part of the The important family of Bakevelliidae (King, sculpture by shell body, present only in the first growth stages; hinge consisting of 1995), which includes highly inequilateral Pterioida with two (or perhaps three in the right valve) cardinal teeth and one slen- a usually rhombic to trapezoidal outline, originated in der, long, posterior lateral tooth parallel to the hinge margin. Ligament the Permian and flourished in the Cretaceous. area straight and rather wide, ligament multivincular. According to Muster (1995) important diagnostic features of the family are the outline (defined by param- Discussion. The new genus is similar to the genus eters diagonal, maximum length of the body, length of Towapteria Nakazawa Er Neweil, 1968 established on the the posterior wing, and obliquity), shell ornamentation, basis of some specimens from the Japanese Middle Per- wing shape, position and shape of the umbones, hinge, mian associations of the Tenjinnoki and Kanokura For- and muscle scars. marions (Nakazawa 8r Newell, 1968), and later discov- Marmaronia n. gen., showing all the features of ered in other Permian and Lower Triassic localities of the this family, represents one of the most ancient members Western and Eastern Tethys. (1,995), his emended diagnosis of the ^f thi" b'-o"ntrn "r' Muster in Marmaronia n. gen. is similar to some genera of genss Torl)apteria, defined this genus as a Bakevellidae Cassianellidae Ichikawa, 1958, for the presence of a well- without radial ribs on the anterior wing. However, this developed radial furrow on the left valve; however, the is true only for the right valve because the holotype of internal septum, important character of the Cassianelli- the type species T. nipponica Nakazawa & Newell, 1968 dae, is absent. (P1.3 fig.8), which is a left valve, shows radial ribs in the The records of Cassianellidae in the Permian suc- anrerior part of the shell (which does not have a real cessions are still sporadic and based on incomplete sPec- anterior wing or lobe, also according to the original

PLATE 1

Fig. 1 - Litrle slab from the coquinoid levels (upper part of Unit i, Marmaro section) with valves of Marmaronia angiolinii n. gen. n. sp. (x 1). Fig.2 - Marrnaronia angiolinii n. gen. n. sp., left valves from Agrelia (x 1). Fig.3a,b -Marmaroniaangioliniin.gen.n.sp.,paratypeMPUMS6O3N, leftvalve; 3a:lateralview(x1.5);3b:frontalview(x2). Fig. 4- Marmaronia angioLinii n. gen. n. sp., paratype MPUM8604D, right valve, internal view (x 1.5). Fig. 5 - Little slab from the upper part of Unit 1, Marmaro section, on the right the paratype MPUM86O2 (the same specimen in fig. 6)(x 1.5). Fig. 6 - Marmaronia angiolinii n. gen. n. sp., paratype MPUM86O2, articulated specimen, lateral view of the right valve (x 3). Fig.7 - Marmaronia angiolinii n. gen. n. sp., paratype MPUM8603M, left valve, lateral view (x 1.5). Fig.8 - Marmaronia angiolinii n. gen. n. sp., pararype MPUM8604G, right valve, oblique view of the partially broken hinge (see arrow) (x 2). Fig. 9 - Little slab with right valves oÍ Marmaronia angiolinii n. gen. n. sp., the arrow indicates the paratype MPUM8604A (x 1.5). Fig. 1O-12, 16 - Marmaronia angíolinii n. gen. n. sp., holotype MPUM86O1, articulated specimen; 1O: lateral view of the left valve (x 2); 11: frontal view (x2'1;12: dorsal view (x 2); 16: ligament area showing the ligamental pits (marked by arrows) (x 8). Fig. 13 - Little slab from the coquinoid levels (upper part of Unit 1, Marmaro section), with valves oÍ Marmaronia angiolinii n' gen. n. sp., the arrow indicates the paratype MPUM8604G (see also fig. 8) (x 1). Fig. 14 - Marmaronia angiolinii n. gen. n. sp., paratype MPUM86O4G, left valve, hinge area with cardinal teeth marked by arrows (the tooth on the left is broken) (x 3). Fig. 15a, b - Marmaronia angìolinìi n. gen. n. sp., paratype MPUM86O3\( left valve; 15a: internal view with cardinal teeth marked by arrows (x 8,1r l5b: enlargement of rhe hinge tx 20) Pl. 1 JI arnt aronitt angìctltn ít i63 364 C. Largbi

description by Nakazawa Er Newell 1968; p. 58). the commissure plane of valves, wider in the right valve The original diagnosis of Towapteria by Nakazawa than the left, even if the left is wider and more convex. & Newell f 1968) can be considered still valid. Ligament multivincular, with several weak, subrectangu- The new genus Marmaronia is distinguished from lar or rarely subtrigonal pits; on some specimens Towapteria in the less pteriiform outline (because of the (MPUM8601, MPUM8603N) the pits are at least five, presence of a more expanded posterior wing, with a less and one of them is located under the beaks. incised sinus), in a wider ligament area, in the prominent Hinge consisting of two cardinal teeth on the left umbo of the right valve (beak located above the hinge valve, (one under the beak and one strong anterior car- margin) and in the ornamentation of the right valve. dinal, Fig. 4) and one slender, long, posîerior lateral The radial costulation is very slight in the first tooth parallel to the hinge margin. On the right valve gros/th stages and absent in the adult stage. hinge consisting of two (or three) cardinal teeth and, Costigervillia Cox & Arkell, 1948 differs from like in the left valve, one slender, long, posterior lateral Marmaronia in the outline, in the more developed obliq- tooth parallel to the hinge margin. uity of the shell, in the presence of an anterior wing on Surface of left valve sculptured by radial costae of the left valve and of few but strong ribs on the right one or two orders and by concentric costae over shell valve. body and posterior wing, radials more or less scaly and Single valves of Marmaronia n. gen. are similar to sometimes nodose at intersections with concentric the valves of some genera such as Arcapicwla Cox, 1964 costae. On the larger specimens there are 6-9 costae near (right valve) or Oxytoma Meek, 1864 (left valve). the ventral margin, between the radial umbonal sulcus Occurence. "Gymnocodiacean limestones" sensu and the posterior margin of the shell body (which sepa- Kauffmann (1,969) of Chios Island (Greece). rates the body margin from the posterior wing). Before Age. Middle Guadalupian (Middle Permian). the sulcus there are 7-8 strong radial costae; the posteri- or wing has a reticulate ornamentation because of the the Marmaronia angiolinii n. sp. intersections between 7-8 weak radial costae and growth rugae. There are costae the first and second (Plate 1) of order, the latter nre and present only in specimens larg- Material. Total: 43 specimens. 39 specimens from Marmaro er than 7 mm. (MPUMS601, 2; MPUM8603A-Z, u, B; MPUM8604A-L) and 4 spec- Right valve ornamented by concentric growth imens From Agrelia (MPUM8605A-D). rugae and in some specimens, in the first growth stages, Type series (28 specimens). by few very thin costae near the posterior margin of the Hololype. A bivalved complete specimen: MPUM8601 (Pl. 1, present fig.10-12, 16). shell body (this radial costulation is perhaps Paratypes. Bivalved complete specimen: MPUM8602; left g, valves (16 specimens): MPUM8603A, D-F, J, K, M, N, O-Q, U, Y \l,Z; righr valves (10 specimens): MPUM8604A-L. Etymology. Species named in honour of Lucia Angiolini. Stratum Typicum and Locus Typicus. The locus typicus is the Marmaro section and the Stratum Typicum is the upper part of Unit 1 sensu Flajs et al. (1996a). Diagnosis. As for the Genus. Description. Shell small, oblique, prosocline, from rhombic to trapeziform, inequilateral and posteriorly alate. Ratio of height to length about 0.9. Strongiy inequivalve, left valve strongly convex, anterior not lobate, but with a radial furrow running from the anteri- or part of the umbonal region to the ventral margin; right valve less convex, without a true anterior auricle, but with an anterior lobe depressed in comparison with the umbonal region. Both umbones are narro.wly rounded, protruding and placed anteriorly. Dorsal margin long and straight, a little shorter than the length of the shell. Valves discordant, right valve smaller than the left. No subauricular notch, only faint traces of a sinuation in the antero-lateral margin. ' Posterior wing very wide separated from the body cardi- of the shell by a very shallow sinus. Fig. 4 - Reconstruction (from camera-lucida, shaded) of the nal teeth (marked by arrows) in two left valves, A: speci- Ligament area rarher developed, perpendicular to men 8603D. B: soecimen 8603\( Marmaronia angioltnii 365

Fig 5 - Hypothetical endobyssate life habit of Marmaronia only in few specimens because it has been removed b) corals, brachiopods and calcareous algae, it lived in very abrasion or iÀ/eathering). shallow waters. A displacement of the radial ornaments visible on The morphology of Marmaronìa suggests two the MPUM86O3F specimen might indicate that the possible different strategies of byssal attachment: organism survived a trauma. epibyssate or endobyssate habit. Muscle scars and pallial line not observed. Following the model of Kauffman (1969) which correlates the shell shape with the exposure to currents, Dimensions (in cm). Marmaronia shows a rather hydrodinamically stream- lined shell. Perhaps Marmaronia lived as an epibyssate in Specimen Length Height Thickness the most exposed lagoonal environments or in coralline MPUM8601 patch reefs, attached to the biostromes made up of (Holotype, bivah.ed specimen) 1'.4 1.3 0.8 syringoporid corals (Mwlthitecopora sp.), brachiopods MPUM8602 and calcareous algae. Yet this epibyssate habit is most (paratype, bivrlved'pecimen; 0.9 suitable for bivalves which have, unlike Marmaronta, a MPUM86O3M developed anterior auricular sulcus and a byssal sinus (paratype, left valve) 1.9 1.7 (see also: Stanley 1972). MPUM86O3N The model proposed by Seilacher (1983) for the (paratype, left valve) 1.3 0.1 byssate Bakevelliidae seems most suitable for Marmaro- MPUM86O4D nia. According to this model Marmaronia was (paratype, right valve) 1.3 endobyssate, partly buried in mud. It would have lived reclined flatly in the sediment, and the strongly inequiv- Discussion. Apart for the generic characters, alved shell could be evidence of this way of hfe. Marma- Towapteria nipponica Nakazawa & Newell, 1968 differs ronia rested on the left valve, which is more convex and f rom Marmaronia angiolinii n. gen. n. sp. in having mor. bears stronger sculpture to increase adhesion to the sed- numerous and differentiated (to 3rd order) radial costat iment (Fig. 5). The ligament area of Marmaronia is more on the ieft valve. developed than in similar epibyssate forms because the There are some similarities between the first onto' ligament must ha\re acted against the sediment pressure. genetic stages of Geruillaria alaeformis (Sowerby' 1819) This way of life seems to be confirmed by tapho- and Marmaronia angiolinii n. gen. n. sp. but the left nomic analyses: the mud levels of the upper part of Unit valve of this species shows a distinct anterior wing. 1, in which bivalved specimens can be collected, could Marmaronia angiolinii n. gen. n. sp. is similar represent the levels in which the bivalves lived. externally to CassìanelLa decussata (Muenster, 1834), but the latter shows a developed anterior auricle. Acknou'ledgemen ts. I n.ish to acknowledge M. Balini for fruit- Only the right valve of Marmaronia angiolinii n. ful discussions and a preliminary rer.iew of the manuscript, G. Chiodi and A. Rizzi for providing the photographs, E. Gozzi and N. Manto- gen. n. sp. is similar to the right valve of Baleeoellia cer- vani for the computer assistance and technical suPport, C. Cortzzato atophaga (Schlotheim, 1816), but can be distinguished for rmproving rhe English 'ersion. by a more prominent umbo and a wider posterior wing. I am indebted to G. Kauffmann, who gave me useful informa- as genus. Occurrence and Age. The same the tion about the locality of Marmaro and bibliographic material, with L. Angiolini and L. Carabelli, for joint field-work and for providing the Palaeoecological remarks specimens from Agrelia. I heartly thank J. M. Dickins and K. Nakaza- -\\J . IUIf^. !lltlLal,)^-;,;^,11,, .-.li--l(dul.lÉ ,1". trl( mJnUSCflpt,

Like the others Bakevelliidae, Marmaronia Proba- A ver,v special thank you to mv mentor M. Gaetani, who bly lived fixed to the sea floor temporarily or Perma- encouraged me to study the Palaeozoic of Chios. nently by byssal attachment. In agreement with the Financial supporl provided by COFIN 2A0A/2001', pro;ect ot "Gymnocodiacean limestones" fossil asse-hl'o" ^{ Prof. M. Gaetani. 366 C. Larghi

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