Mesozoic Fishes 4 Homology and Phylogeny Proceedings of the international meeting Miraflores de la Sierra, 2005 Gloria Arratia, Hans-Peter Schultze and Mark V. H. Wilson (editors) Verlag Dr. Friedrich Pfeil • München Mesozoic Fishes 4 – Homology and Phylogeny, G. Arratia, H.-P. Schultze & M. V. H. Wilson (eds.): pp. 129-142, 8 figs. © 2008 by Verlag Dr. Friedrich Pfeil, München, Germany – ISBN 978-3-89937-080-5 A new semionotid fish (Actinopterygii) from the Upper Triassic of northern Italy Cristina LOMBARDO & Andrea TINTORI Abstract We describe a new genus of semionotiform on the basis of well-preserved specimens from the Calcare di Zorzino (Zorzino Limestone, Norian, Upper Triassic) of the Bergamo Prealps, northern Italy. Semiolepis brembanus gen. et sp. nov., is characterized by a moderately deep body, dorsal ridge scales showing well-developed spines, an incomplete circumorbital series, a single suborbital bone, and multiple extrascapulars. Semiolepis gen. nov. is peculiar among semionotids in having very deep infraorbital bones and a strong heterodont dentition. In addition, a new character of the caudal fin, an additional incomplete scale row on the posterior margin of the axial body lobe, is described. The new taxon shows intermediate characters between Semionotus and Lepidotes. The systematic assessment of this new taxon, owing to its peculiar combination of anatomical features, stresses once more the problems concerning the unsatisfactory diagnosis of the order Semionotiformes as well as the taxa currently interpreted as semionotiforms. Introduction The choice of the characters diagnosing the Semionotiformes, and the Semionotidae in particular, has been debated in the last years, following the description of new taxa or the revision of previously known ones. When WOODWARD (1890) erected the family Semionotidae he included the genera Acentrophorus, Semionotus, Aphnelepis, Serrolepis, Pristisomus, Sargodon, Colobodus (= Paralepidotus, in part), Lepidotus, Dapedius (= Dapedium), Cleithrolepis, Aetheolepis and Tetragonolepis. Recently, a new taxon, Sangiorgioichthys aldae, from the upper Ladinian of Monte San Giorgio, has been included in this family (TINTORI & LOMBARDO 2007). Some of those genera (e.g., Cleithrolepis and Serrolepis) have been moved to Perleidiformes (BROUGH 1931, LOMBARDO & TINTORI 2004); others, such as Dapedium, Tetragonolepis and Acentrophorus, have been deleted from the Semionotidae (BERG 1940, WENZ 1968, PATTERSON 1973, among others) and placed in the families Dapedidae and Acentrophoridae, with very different phylogenetic positions. For instance, Dapedium has been proposed as a potential sister group of teleosts (e.g., GARDINER et al. 1996). OLSEN & MCCUNE (1991) considered the Semionotidae as constituted by only two genera, Semionotus and Lepidotes, on the basis of two synapomorphies: the dorsal ridge scales and the presence of a large posteriorly directed process on the epiotic. As stressed by WENZ (1999), the first synapomorphy is not present in all semionotids and the identification of the second one is rarely possible, depending on the kind of preservation of the specimens. In fact, new genera have been recently added to the family: Paralepidotus (TINTORI 1996), Araripelepidotes (WENZ & BRITO 1996) and Pliodetes (WENZ 1999). The assignment of these taxa to the Semionotidae led WENZ (1999) to discriminate three groups within the family, according to the number of suborbitals: one (Semionotus and Paralepidotus), two to ten (Araripelepidotes, some species of Lepidotes), many to form a mosaic (Pliodetes, other species of Lepidotes). We think that subdividing the family in two groups (single/more than one suborbital, following MCCUNE 1986) should be preferred, at least until a revision of the genus Lepidotes is provided. The aims of this work are to describe a new Triassic semionotiform and contribute to the knowledge of this group and its complexity, even if we are aware that a complete systematic revision, especially of Lepidotes, is necessary to proceed in for deeper investigations (i.e. phylogenetic relationships). 129 Calcare di Zorzino – fauna and palaeoenvironment The Middle-Late Norian intraplatform basin facies (Calcare di Zorzino) in Lombardy preserve one of the richest fish faunas of the whole marine Mesozoic. A wide, Lower Norian carbonate platform (Dolomia Principale) was disrupted and parts of it foundered along faults. The intraplatform basins that developed as a consequence played a major role in both life environment and fossil preservation (JADOUL et al. 1994, TINTORI 1992, RENESTO & TINTORI 1995). In Lombardy, most of the fossil vertebrate faunas were recovered from strata deposited at the boundary between Middle and Upper Norian, which is here marked by a lithological shift from limestones to shales and marls (JADOUL et al. 1994, BERRA & CIRILLI 1997, TINTORI et al. 1985), clearly related to a change in environmental conditions (major transgression) in both superficial and bottom waters. The presence of echinoderms, brachiopods and corals in the Calcare di Zorzino (BLAKE et al. 2000, TINTORI 2003), indicate that basinal surface waters had normal salinity. The fossils found allow a reconstruction of nectonic and benthic life assemblages at the basin margins as well as continental life assemblages on nearby islands, where also several reptiles could live, with terrestrial (Langobardisaurus), arboreal (Megalancosaurus) or flying (Eudimorphodon) specializations (WILD 1978, RENESTO 1994, RENESTO & DALLA VECCHIA 2005). Some other reptiles possibly spent part of their life in water, especially for feeding: for example the thalattosaur Endennasaurus, the armoured placodont Psephoderma and the phytosaur Mystriosuchus (RENESTO 1992, RENESTO & TINTORI 1995, GOZZI & RENESTO 2003). The number of fish genera of the upper Calcare di Zorzino (probably around 50) greatly exceeds that of any other Triassic fish assemblage known so far: they generally count between 10 to 15 genera (TINTORI 1998). Some of the groups flourishing in the Norian, mainly palaeopterygians, became extinct by the end of the Triassic while several others among neopterygians (semionotiforms, pycnodonts, ‘pholidophoriforms’, etc.) survived the Triassic-Jurassic crisis and thrived through the Jurassic and the Early Cretaceous (with pycnodonts reaching the Eocene). The Calcare di Zorzino preserves evidence of a fundamental step in fish evolution, as basal paleopterygians and subholosteans began to be replaced by neopterygians (TINTORI 1998). However, the large palaeopterygian predators Saurichthys (TINTORI 1990, TINTORI & GOZZI 2005), Gabanellia (TINTORI & LOMBARDO 1996) and Birgeria (GOZZI & TINTORI 2005) still represented the highest trophic level of the fish fauna. The palaeopterygian flying fish Thoracopterus is another common predator yielded by the Calcare di Zorzino (TINTORI & SASSI 1992). Beyond the small so-called pholidophorids, usually representing about 70 % of the Calcare di Zorzino fish fauna, one of the most common neopterygians is Paralepidotus ornatus, a durophagous form that lived on shallow, oxic bottoms (TINTORI 1995). Actinopterygians had rarely achieved this trophic level before the Norian (TINTORI 1998), and grazer and nibblers are as yet almost unknown from beds older than the Late Triassic, apart from a few taxa from the Middle Triassic of Monte San Giorgio (for a summary, see LOMBARDO & TINTORI 2004) and from the new site in the Grigna Settentrionale (Lecco, N. Italy) (TINTORI & LOMBARDO 2005a,b). Adult Paralepidotus, about 50 cm long, had hemispherical teeth adapted to crash shells, as indicated by many coprolites consisting of Modiolus fragments (TINTORI 1995): the long inserted dorsal fin and the heavily armored body suggests high maneuverability but low speed. The small pycnodonts Eomesodon, Gibbodon, and Brembodus (< 12 cm long), and the semionotiform Sargodon (up to 1 m long: TINTORI 1981, 1983) possessed chisel-shaped teeth in the premaxilla, grinding teeth in the prearticular and vomer adapted to graze on hard surfaces or pick bissate bivalves and then crash them. These fishes had laterally compressed bodies and they probably moved at ease in a rugged bottom. All these fishes needed a rich benthic fauna made mainly by mollusks to feed on. Many other fish taxa of both basal (Endennia LOMBARDO & BRAMBILLASCA, 2005) and more advanced actinopterygians (this paper) show similar trophic and swimming specializations (LOMBARDO & TINTORI 2005), inferring a rich-of-life, complex bottom habitat along the basin rim. This clearly contrasts either with the disaerobicanoxic environment of the Calcare di Zorzino or with the poor assemblages known from the Dolomia Principale shallow waters (JADOUL et al. 1994). Well documented through the Mesozoic fossil record, from Middle Triassic to Late Cretaceous, Semionotiformes represent one of the most distinctive components of the Zorzino ichthyofauna, including wellknown genera such as Paralepidotus, Dandya and Sargodon, and the new genus described in this paper. Abbreviations used in figures: an, angular; ant, antorbital; br, branchiostegal rays; ch, ceratohyal; cl, cleithrum; de, dentary; dpt, dermopterotic; dsph, dermosphenotic; ect, ectopterygoid; exo, exoccipital; exsc, extrascapulars; fr, frontal bone (following the traditional terminology); hy, hyomandibula; io, infraorbital bones; iop, interoperculum; mx, maxilla; na, nasal bone; op, operculum; pa, parietal bone (following the traditional terminol- 130 ogy); dpcl, dorsal postcleithrum; pmx, premaxilla; pop, preoperculum; psph, parasphenoid; pt, posttemporal; q, quadrate; ro, rostral bone; sbo, suborbital bone; scl, supracleithrum; ser, serrated organ; smx, supramaxilla; so, supraorbital bones; sop, suboperculum; vo, vomer(s); vpcl, ventral postcleithrum. Institutional abbreviations: MBSN, Museo Brembano di Scienze Naturali, S. Pellegrino Terme (BG), Italy; MPUM, Museo Paleontologia dell’Università degli Studi di Milano; MVSLZ, Museo della Vicaria di San Lorenzo in Zogno, Zogno (BG), Italy. Systematic Paleontology Actinopterygii COPE, 1887 Neopterygii REGAN, 1925 Semionotiformes ARAMBOURG & BERTIN, 1958 Semionotidae WOODWARD, 1890 pro parte Semiolepis gen. nov. Diagnosis: As for the only known species. Type species: Semiolepis brembanus gen. et sp. nov. Etymology: From semio (to recall the relationship with Semionotidae) and lepis (scales, for the peculiar dorsal ridge). Semiolepis brembanus sp. nov. (Figs. 1-8) 1905 2005 Semionotus kapffi GORJANOVIC-KRAMBERGER: p. 196, fig. 1, pl. 18, fig. 2. New semionotid MILESI et al.: p. 191-195, figs. 1-3. Diagnosis: (based on a combination of characters): Semionotid up to 25 cm in SL, with a quite pronounced dorsal hump. Skull roof with long and narrow frontal bones. Seven extrascapulars: one median squarish and three longer than wide bones on each side of skull roof. Circumorbital series incomplete. Five to 7 infraorbital bones, very deep on ventral region of orbit, and gradually decreasing in size towards ethmoidal region. Single suborbital bone. Short dentigerous maxilla. Mouth with conical marginal teeth; crushing teeth present on upper and lower jaws. Operculum much deeper than broad, with well-developed antero-dorsal process; suboperculum about 1/5 as deep as the operculum. All dermal bones are ganoine depleted, except for sparse and minute tubercles arranged mainly on posterior part of skull roof and on infraorbital bones. Squamation covered by a smooth layer of ganoine. Dorsal fin with widely spaced rays. Strong basal and fringing fulcra on all fins. Dorsal ridge scales with well-developed spines, each as long as base of scale, except for anteriormost ones, broader than long, with a short posterior spine. Squamation consisting of seven scale rows between dorsal and anal fins and of 35 transversal scale rows; scales deeper than broad on anterior region of body and with weak posterior serrations; rhombic scales, as deep as broad, on ventral body region; no dorsal intercalated scale rows. Large preanal scute with a rounded posterior edge, bordered by several small spines. Posterior margin of axial body lobe with an additional incomplete row of 6 or 7 scales, placed dorsal to last lateral line scale. Etymology: From the name of Brembo river, in whose valley the specimens were found. Holotype: MPUM 9288, a well-preserved, complete and articulated specimen of 75 mm in SL, except for a slight displacement of the lower jaw and the loss of some dorsal ridge scales (Fig. 1A). Type-locality: Zogno2 (Poscante-Zogno, Bergamo, Italy). Paratypes: Specimens MBSN 67 (a fragment with skull), MBSN 68 (specimen lacking the caudal fin); MVSLZ ST 82916 (complete and articulated specimen of 120 mm in SL); all from Endenna (Zogno, Bergamo, Italy). Age and horizon: All the specimens come from the vertebrate level between the Calcare di Zorzino and the Argillite di Riva di Solto; this level is considered at the boundary between Middle and Late Norian (Late Triassic) on the basis of the palynological content. 131 A B C 132 A exsc pa pt so dpt dsph scl fr sbo psph na op dpcl io pop io io sop ant mx q iop vpcl vo ect ro pmx an ch de br B Fig. 2. Skull of Semiolepis brembanus gen. et sp. nov. in lateral view. A, specimen MBSN 67. B, drawing of the same. Scale bar = 5 mm. Notes: One further specimen is ascribed to this new species: it was described as Semionotus kapffi by GORJANOVIC-KRAMBERGER (1905) from the Norian site of Hallein. Unfortunately the specimen is no longer in the collection of the University of Leoben (Austria), where the material should be stored (G. SCHARFE, pers. comm. 2005), so our identification is based on the illustration of GORJANOVIC-KRAMBERGER (1905). / Fig. 1. Semiolepis brembanus gen. et sp. nov. in lateral view. A, holotype MPUM 9288; 75 mm in SL. B, MVSLZ ST 82916; 20 mm in SL. C, MBSN 68. Scale bar = 10 mm. 133 exsc pa pt A dpt dsph fr so sbo op io pop exsc sop pt pa br scl q iop ch dpt ect an mx mx cl ser hy sbo io op io dpcl ? exo pop de fr io io ant ect sop iop vpcl q pmx smx mx cl an cor B de br Fig. 3. Semiolepis brembanus gen. et sp. nov. A, drawing of the skull of the holotype MPUM 9288. B, drawing of the skull of MBSN 68. Scale bar = 5 mm. Description All bones are smooth and devoid of ganoine covering, if not otherwise specified. Skull roof and braincase: The rostral bone is a small trapezoidal element with the ethmoidal commissure running along the ventral part (Figs. 2A,B, 4A,B). The nasal bone is drop-shaped, with the pointed dorsal ends fitting into the deep anterior notches of the frontal; the supraorbital sensory canal runs along the longitudinal axis of the nasal (Figs. 2A,B, 4A,B). The frontal bone (following the traditional terminology, not that based on homologization of bones) is a very long sub-rectangular element, elongated anteroposteriorly, tapering towards the ethmoidal region and showing an embayment at the level of the orbit. The median suture is almost straight, while the posterior margin shows a distinctive notch on the lateral corner of the bones. The supraorbital sensory canal runs parallel to the lateral margin of this bone. A few small tubercles are present only on the posterior part of the frontal bone (Figs. 2-4). The parietal bone (following the traditional terminology, not that based on homologization of bones) is squarish, with a strongly sinuous interparietal suture. A small projection, anteriorly directed, that fits into the lateral notch of the 134 exsc pt dsph pa dpt scl fr so sbo io op io io io io ect smx mx an q sop vpcl ro pmx ant pop dpcl na io iop de ch cl A br exsc op scl pt pop sbo io dsph so dpt pa ant na fr ro B Fig. 4. Semiolepis brembanus gen. et sp. nov. Restoration of the skull in (A) lateral and (B) dorsal views. frontal, is present on the antero-lateral corner of the parietal. Small tubercles are homogenously arranged on the surface of the parietal bones (Figs. 2-4). The dermopterotic is hourglass-shaped, developed antero-posteriorly, flanking the parietals for their entire length. Large pores of the sensory canal are detectable on the dorso-lateral part of the dermopterotic (Figs. 3A, 4A,B). There are several extrascapulars (Figs. 2-4): the series includes one median squarish bone, and three extrascapulars longer than deep on each side. All extrascapulars are covered by small tubercles. It is unclear whether one or two vomers are present. The preserved element (Figs. 2B, 3B) is dentigerous, with stout and strong teeth whose tips bear well-developed acrodine caps. Circumorbital bones: The dorsal margin of the orbit is bordered by a series of five supraorbital bones (Figs. 3A, 4A,B), slightly decreasing in size posteriorly. The dermosphenotic is dorso-ventrally elongated and slightly curved antero-dorsally. The ornamentation consists of sparse small tubercles (Figs. 2B, 3A, 4A,B). The series of infraorbitals includes 7 or 8 bones: one or two on the posterior part of the orbit are small and tube-like; the three bordering the ventral orbital region are very large and deep, the others becoming smaller and squarish towards the snout, so that the circumorbital series is incomplete. The infraorbital sensory canal (Fig. 4B) runs along the mid-dorsal part of the infraorbital bones and branches in the middle region of each bone. The dorsal region of the bones, near the orbital margin, is ornamented with minute tubercles. The first element of the series is interpreted as the antorbital owing its position and shape. The antorbital is narrow, antero-posteriorly elongated and slightly bent-shaped. The infraorbital sensory canal passes through its middle region (Figs. 2B, 3B, 4A,B), but it is not possible to clearly detect the connection between the infraorbital, the supraorbital sensory canals and the rostral commissure. A single suborbital bone (Figs. 2A, 3A,B, 4A,B) is present. It is sub-rectangular in shape and dorsoventrally elongated. 135 Fig. 5. Semiolepis brembanus gen. et sp. nov. Detail of the pre-anal scute of the holotype MPUM 9288. Scale bar = 5 mm. Jaws: The triangular premaxilla is well developed and bears strong conical teeth; a stout ascending process is only partially visible, being covered by the surrounding bones. The sub-triangular maxillary bone shows a rounded posterior region, tapering towards the ethmoidal region of the skull. A few narrow and slightly backwardly bent teeth are visible on the oral margin. A supramaxilla (Figs. 4B) seems to be present on MBSN 67. The strong lower jaw shows a deep angular and an elongated dentary whose tip slightly bends downwards. Teeth are conical, slightly backwardly bent, on the oral margin of the dentary. The coronoids show several rows of teeth that are each characterized by a quite long base domed by a rounded crown. Near the ventral margin, the lower jaw shows large openings corresponding to the pores of the mandibular sensory canal (Figs. 2A,B, 3A,B, 4B). Hyoid arch and opercular bones: A large anterior ceratohyal (Figs. 2B, 3A) is visible in specimens MPUM 9288 and MBSN 68. About ten smooth branchiostegal rays are preserved (2A,B, 3B, 4A). The preoperculum is narrow and boomerang-like, bending at the level of the suture between the operculum and the suboperculum. Large openings on the ventral arm (Figs. 2A,B, 3A,B, 4A,B) indicate the passage of the preopercular sensory canal. Other opercular bones are the large subrectangular operculum, the suboperculum about 1/5 as deep as the operculum and provided with a well-developed antero-dorsal process, and the small triangular interoperculum (Figs. 2A,B, 3A,B, 4A,B). No gular plate is visible. Pectoral girdle and fin: The large and triangular posttemporal bones apparently meet in the midline. The pores of the supratemporal sensory canal (3B, 4A,B) are clearly detectable on the ventro-lateral part of the bone. The supracleithrum is subrectangular; two postcleithra are visible, the dorsal much deeper than the ventral one. Both elements are covered with ganoine on their exposed portion and show posterior serration. The cleithrum (Figs. 2B, 3A,B, 4A) is only partially visible, being covered by the operculum, dorsal postcleitrum and the branchiostegal rays. Three rows of minute denticles are visible when the bones are partially displaced or incomplete so that part of the cleithrum is exposed. Another bone bearing rows of denticles is visible on specimen MPUM 9288. It is interpreted here as a serrated organ (Fig. 3A). The pectoral fins have at least 17 lepidotrichia. Each ray consists of a long and flattened proximal 136 Fig. 6. Semiolepis brembanus gen. et sp. nov. Caudal fin of the holotype MPUM 9288. Scale bar = 5 mm. base followed by small and squarish distal segments. Each ray branches distally at least twice. Ganoine is present only on the exposed margins of the anteriormost rays. On the anterior margin of the fins of specimen MBSN 67 (Fig. 1A,C) two basal fulcra as well as long, well developed fringing fulcra are visible. Pelvic fins: The pelvic fins, placed at the level of the 9th and 10th transverse scale rows, have nine lepidotrichia that are similar in structure to the pectoral rays. The pelvic fins also bear basal and fringing fulcra (Figs. 1A,C, 5) that are similar in shape and number to those present on the pectoral fins. Unpaired fins: The dorsal fin lies at the level of the 24th and 25th transverse scale rows and comprises at least 13 lepidotrichia that are widely spaced. Each ray has a short proximal base followed by tiny distal segments. Each ray branches at least twice. There are at least three basal fulcra and a series of long fringing fulcra (Fig. 1A). The anal fin is placed at the level of the 17th transverse scale row and is smaller than the dorsal fin. Both fins show similar structure. There are about eight lepidotrichia branching at least twice. A couple of basal fulcra and a series of long fringing fulcra are present (Fig. 1A-C). The caudal fin presents about 20 lepidotrichia (Figs. 1A,B, 6, 8). The dorsal margin of the fin shows 137 A pt C B Fig. 7. Semiolepis brembanus gen. et sp. nov. A, dorsal ridge scales in specimen MVSLZ ST 82916. B, drawing of the same. C, detail of the anterior scales of median ridge in the holotype MPUM 9288. Scale bar = 5 mm. six to eight basal fulcra. On the holotype MPUM 9288 the dorsal leading ray, bearing fringing fulcra, is segmented but not branched and it is followed by 15 segmented and branched lepidotrichia. Along the ventral margin of the fin there are two basal fulcra and a short segmented and unbranched ray, bearing few fringing fulcra, followed by the leading ray, segmented and not branched either, but bearing fringing fulcra. In specimen MVSLZ ST 82916 the tip of the dorsal lobe of the caudal fin is not preserved, so that it is impossible to state the number of segmented and unbranched rays; ventrally there are nine segmented and branched rays, followed by a single short segmented and unbranched ray bearing few fringing fulcra. In this specimen, the ventral leading ray, bearing fringing fulcra, is segmented and branched. Each ray is formed by a short proximal base followed by very small segments, and it branches at least three times. Distally, the rays appear very thin and delicate and the posterior outline of the fin is slightly concave. Fringing fulcra are narrow, elongated and of similar length. Additionally, the series is not complete, as the fringing fulcra do not reach the distal tips either of the dorsal and ventral lobes (Figs. 1A, 6). Squamation: The squamation consists of about 35 transverse scale rows and 20 to 22 horizontal ones. All scales show a smooth ganoine-covered free surface. The scales of the latero-ventral region of the flank are rectangular, deeper than broad, with a slightly rounded posterior margin; their depth decreases gradually towards the dorsal, ventral and caudal parts of the body. The scales of the dorsal region become smaller but they keep a rectangular shape, until the insertion of the dorsal fin; at the base of this fin and posterior to it, the scales become as deep as broad (Fig. 1A-C). Scales of the belly region are rhombic, as deep as broad, beginning from the region between the pectoral fins (Figs. 1A-C, 5). The circumanal series (Fig. 5) consists of a large pre-anal scute, with a semicircular posterior edge fringed by several small spines, followed by a smaller lateral scale that also bears small spines. On the caudal pedicle scales are broader than deep. The axial body lobe is covered by seven vertical, diamond-shaped, scale rows of typically “reversed squamation”; the longest scales are those bordering the posterior margin of the lobe (Fig. 6). The posterior margin of the axial body lobe is characterized by an additional incomplete row of 6 or 7 scales, beginning just above the last scale of the lateral line (Figs. 6, 8A) that is large and forked. The dorsal ridge scales show a well-developed spine (Fig. 7A,B); the most anterior scales are much broader than long and they have a very short spine (Fig. 7C). The length of the spines increases gradually all along the anterior half of the series, becoming as long as the scale bases. Each spine is dorsally convex and shows a marked thickening along its longitudinal axis. Ganoine covering is complete except for the lateral area of the scales (Fig. 7A,B). A weak serration is visible only on the first transversal scale rows. Some scales of the lateral line and of the ventral region show few larger serrations, even if most of the scales have a smooth posterior margin. 138 B A C D Fig. 8. Pattern of squamation of the axial body lobe in (A) Semiolepis brembanus gen. et sp. nov. (holotype MPUM 9288); (B) Semionotidae ind. (MPUM 9363); (C) Paralepidotus ornatus (MPUM uncatalogued); and (D) Semionotus elegans (after OLSEN & MCCUNE 1991: 272, fig. 1). In black the last scale of the lateral line; in dark grey the last additional scale row. Discussion and conclusions The new fish described in this paper is interpreted as a new member of the Semionotidae based on the arguments presented below. Semiolepis brembanus gen. et sp. nov. is considered here a representative of the family Semionotidae mainly on the basis of the presence of dorsal ridge scales with developed spines and of a series of lachrymals (= infraorbitals) anterior to the circumorbital ring (MILESI et al. 2005). According to WENZ (1999) the Semionotidae are also characterized by a combination of characters such as the presence of at least 139 one suborbital bone, premaxilla with a long ascending process, a complete opercular apparatus, loss of gular, and presence of ganoid scales and strong fulcra. In our opinion, these features are not unique to Semionotidae, because they are also found in other neopterygian groups. All previous authors agree that the presence of one, two or more suborbital bones is one of the major differences within the family. However, we will compare the new taxon described here with representatives of groups with “more than one suborbital” in order to show once more the complexity of the Semionotidae as currently understood. Among the genera with more than one suborbital bone (Araripelepidotes, Pliodetes and Lepidotes), Semiolepis brembanus gen. et sp. nov. shares with Araripelepidotes only the presence of large and deep infraorbitals bordering the ventral part of the orbit. These two taxa then differ in many skull features, such as the arrangement of the jaws, the size of dermosphenotic and frontal bones and the shape of preoperculum. Regarding the body, Araripelepidotes squamation consists of about 40 transversal scale rows, strong fringing fulcra all along the fins margin, and insertion of dorsal fin close to that of the anal fin (MAISEY 1991, THIES 1996). Apart from the number of suborbital bones, Pliodetes differs from Semiolepis brembanus gen. et sp. nov. in the skull roof pattern. For example, in proportions and shapes of bones (e.g. broad and short frontals, large supraorbitals). Moreover, in Pliodetes the circumorbital series is complete, the opercular region is made by an operculum and a suboperculum of similar size, while the preoperculum is L-shaped. All the dermal bones are strongly ornamented with tubercles and short ridges (WENZ 1999). If we consider the number of suborbital bones, the comparison between the new taxon here described and the genus Lepidotes is crystal clear: Lepidotes has from 2 to 20 suborbital bones. Currently, Lepidotes is something like a garbage basket genus, because its species show contradictory characters that have been pointed out by different authors. For instance: dorsal ridge scales with or without spines, circumorbital series complete or incomplete, suborbitals arranged in a single row or forming a mosaic, presence or absence of tritorial teeth, and multiple or single extrascapulars. A comparison of Semiolepis brembanus gen. et sp. nov. with several species of Lepidotes has evidenced only random similarities for some of the above mentioned characters, such as the incomplete circumorbital series (Lepidotes lennieri and L. tendaguruensis; JAIN 1983, ARRATIA & SCHULTZE 1999), multiple extrascapulars (L. laevis, L. maximus, L. pustolosus and L. mantelli; JAIN 1983), dorsal ridge scales with developed spines (L. maximus, L. minor and L. deccanensis; ARRATIA & SCHULTZE 1999), tritorial teeth (L. bernissartensis and L. latifrons; JAIN 1986). Among the semionotids with a single suborbital bone (Paralepidotus and Semionotus), Semiolepis brembanus gen. et sp. nov. shares with Paralepidotus ornatus the incomplete circumorbital series; nevertheless, the two genera are clearly different both in skull and body features. Paralepidotus has small infraorbital bones, a single extrascapular, only tritorial teeth, dorsal fin with a long base, and its squamation consists of about 40 transversal rows of scales which show a strong ornamentation in adult specimens (TINTORI 1996). Also the shape and the pattern of the axial body lobe covering looks different, with very elongated scales (Fig. 8C) in the last row below the last scale of the lateral line and the additional scale row on the posterior margin beginning far from it (compare Fig. 8B and C). Semiolepis gen. nov. seems to be similar to Semionotus especially in the shape of the middle dorsal ridge scales, size, body shape, and in the lack of scales ornamentation. However, all species of Semionotus (MCCUNE 1986, 1987, OLSEN & MCCUNE 1991) have a complete circumorbital series, shallow infraorbital bones below the orbit (while they are higher anterior to it), non-heterodont dentition, strong basal and fringing fulcra either in paired or in median fins, and no additional scale row on the posterior margin of the body lobe. The last feature is absent, at least in the Semionotus elegans group (OLSEN & MCCUNE 1991) (Fig. 8D). This feature is also absent in some specimens of Late Jurassic Lepidotes sp. from Bavaria (pers. obs.). Owing to its peculiar combination of characters, we erect a new genus and species, Semiolepis brembanus, for the specimens here described. Acknowledgments The authors wish to thank to the Soprintendenza Archeologica della Lombardia, Museo della Vicaria di S. Lorenzo Martire (Zogno, Bg) and Museo di Scienze Naturali (San Pellegrino Terme, Bg) for the loan of specimens in their care. Comments by A. 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Authors’ addresses: Cristina LOMBARDO and Andrea TINTORI, Dipartimento di Scienze della Terra “A. Desio”, Università degli Studi di Milano, Via Mangiagalli 34, 20113 Milano, Italy; e-mail: cristina.lombardo@unimi.it, andrea.tintori@unimi.it 142 The Mesozoic was an important time in the evolution of chondrichthyan and actinopterygian fishes because it was then that most of the modern groups first entered the fossil record and began to radiate. By the end of the era, many archaic forms had disappeared and the foundation had been laid for the modern diversity of fishes. Despite this significant evolutionary change, before 1990 there had been little concerted research done on Mesozoic fishes and no synopsis or compilation of the systematics and paleoecology of Mesozoic fishes had been published, not even for single groups. To remedy this deficiency, Gloria ARRATIA organized the first symposium, “Mesozoic Fishes – Systematics and Paleoecology” in Eichstätt, Germany, from August 9 to 12, 1993 and, with G. VIOHL, edited the first volume in the Mesozoic Fishes series. Published in 1996, it included 36 papers about elasmobranchs, actinopterygians, sarcopterygians, and the paleoecology of certain important fossil localities. Gloria ARRATIA and Hans-Peter SCHULTZE organized the second symposium in Buckow, Germany, from July 6 to 10, 1997, and edited the resulting volume “Mesozoic Fishes 2 – Systematics and Fossil Record”, which included 31 papers. Andrea TINTORI, Markus FELBER, and Heinz FURRER organized the third Symposium in Serpiano, Monte San Giorgio, Switzerland, from August 26 to 31, 2001. The results of that symposium included 33 papers, edited by G. ARRATIA and A. TINTORI and published in “Mesozoic Fishes 3 – Systematics, Paleoenvironments and Biodiversity”. Francisco José POYATO-ARIZA organized the fourth and most recent Symposium on “Mesozoic Fishes – Systematics, Homology and Nomenclature” in Miraflores de la Sierra, Madrid, Spain, from August 8 to 14, 2005. The results of that meeting, as presented here in 24 research papers, reflect the current state of knowledge about Mesozoic fishes. This volume emphasizes the two major groups of fishes, actinopterygians (mainly represented by teleosts) and chondrichthyans, that lived during the Triassic, Jurassic, and Cretaceous periods, and includes studies on related fishes up to the present, as well as papers dealing with homology problems in fishes. New discoveries are presented about fishes from Africa, Antarctica, Asia, Europe, North America, and South America. As illustrated by this volume, there has been recently a flowering of studies on Cretaceous teleosts, in contrast to the more limited number of studies on chondrichthyans. The new discoveries and the critical evaluation of previous research presented here are an exciting invitation to further research on Mesozoic fishes. ISBN 978-3-89937-080-5 www.pfeil-verlag.de