Mesozoic Fishes 4 – Homology and Phylogeny

E. O. WILEY: Homology, identity and transformation
[pp. 9-21, 2 figs.]

Part of the “problem of homology” lies in not making a clear distinction between individuals and kinds. Another part of the problem is not distinguishing between properties and parts. A character is one of the many parts of an organism. Relative to a particular organism; a character is one of the many properties of the organism. A character also has its own, intrinsic, properties that differentiate the character from the other character parts/properties of the organism. Two different organisms are said to share the same character property when the investigator asserts an identity between the characters that is based on the intrinsic properties of the characters themselves. The question is: what is the nature of this identity? Characters share an identity because they share common properties. These properties may be associated with nominal kinds, natural kinds, or individuals. The properties of nominal kinds are set by convention and are typical of the definitional properties of common vocabularies (e.g., criminal, motorcycle). The properties of natural kinds are set by scientific theories held to be true at the time (kinds such as hydrogen or monophyletic group). Interestingly, such kind properties are not historically bound and in most cases the individuals having the property gain it by what systematists would identify as convergence. Character properties of organisms and the intrinsic properties of these characters are contingencies of history and assert some relationship among the organisms sharing the characters. Character properties shared by individual organisms may be properties of monophyletic groups to which the individuals are parts (homology) or kind properties (homoplasies); properties of polyphyletic groups. Thus, at the level of identical characters, those characters with the same identity, homology is synapomorphy and synapomorphies constitute some of the properties of monophyletic groups (PATTERSON 1982). This is taxic homology. Homology is also asserted as a relationship between characters with different identities, as in fins and legs. This is transformational homology. Although there are no sufficient conditions for asserting that a relationship of transformational homology exists for any two or more organisms, there are necessary conditions that can be tested.

Hans-Peter SCHULTZE: Nomenclature and homologization of cranial bones in actinopterygians
[pp. 23-48, 9 figs., 2 tabs., 1 app.]

The homologization of cranial bones of actinopterygians with those of sarcopterygians based on the bone names established in human anatomy is favored in order to permit the building of phylogenetic relationship schemes beyond the taxonomic boundaries of osteichthyans (including tetrapods). The basic criterion of homology is that of evolutionary continuity which can best be accomplished by comparing closely related taxa within groups and basal taxa in sister groups. In actinopterygians, the terms parietal and postparietal bones have to replace the commonly used terms “frontal” and “parietal” bones for the two paired bones on the skull roof. The infraorbital bone 1 of actinopterygians is homologous with the lacrimal bone and the infraorbital bone 3 of advanced actinopterygians with the jugal bone of sarcopterygians. Infraorbital bone 6 of advanced actinopterygians is the dermosphenotic bone. Dermosphenotic and supratemporotabular bones are the two bones lateral to the parietal and postparietal bones in basal osteichthyans. In the lower jaw, the dentosplenial bone of actinopterygians represents the dentary plus splenial bones of sarcopterygians. Many bones appeared independently in actino­pterygians and sarcopterygians; they are not strictly homologous, this should be expressed either in the form of “. . .” (“premaxilla” = a neomorph in actinopterygians) or by prefix of the group where it appears (actinistian orbitosphenoid). Recognition of homologies can change with the discovery of new basal taxa or with new interpretations of bones and their relationships to each other.

Gloria ARRATIA: Actinopterygian postcranial skeleton with special reference to the diversity of fin ray elements, and the problem of identifying homologies
[pp. 49-101, 31 figs. (3 farbig)]

The actinopterygian postcranial skeleton is not as well known as its cranial counterpart, and consequently it is less represented in phylogenetic analyses. Due to this incomplete knowledge, it is often difficult to postulate hypotheses about homologous structures. Fin rays, scutes, fulcra, and spines have been traditionally interpreted as modified scales, but their diversity has been almost ignored. The present study reveals differences in the structure and role of procurrent rays, principal rays, rudimentary rays, and spines of unpaired fins in teleosteomorphs (including †‘pholidophoriforms’) versus “true” teleosts and other actinopterygians. Based on results presented here, revised definitions of these elements are provided.

Presence of long, segmented-but-unbranched first and last principal rays forming the leading margins of the caudal fin is interpreted as a new synapomorphy of Teleostei. In contrast, leading margins of the caudal fin formed by more than one principal ray (mainly segmented-and-branched rays) are consistently present in teleosteomorphs, e.g., †pachycormiforms, †aspidorhynchiforms, and diverse †‘pholidophoriforms’. Similar patterns are found in both dorsal and anal fins where the main leading marginal ray is a segmented-and-branched principal ray in teleosteomorphs. This is in contrast to true teleosts, where the long, first (segmented but unbranched) principal ray has this role. A new structure, named complex ray, is described here for a lepidotrichium that fuses to elements like basal fulcra (e.g., †‘pholidophoriforms’) or bony splints (e.g., †Tharsis, elopiforms, albuliforms). The absence of a complex first pectoral ray is a synapomorphy of osteoglossomorphs plus more advanced teleosts and its presence is a symplesiomorphy shared by teleosteomorphs and basal teleosts including elopiforms and albuliforms. In contrast to a complex ray, a spine is the result of early fusion of two hemilepidotrichia into a strong, massive ray. Spines are found in phylogenetically unrelated actinopterygians (e.g., acipenserids, probably †pachycormiforms, and some teleosts) and are interpreted as independently acquired in those groups. Spines and complex rays are non-homologous structures. Basal fulcra are paired or unpaired elements, which can be present simultaneously in an individual; often the most anterior basal fulcra are unpaired whereas the most posterior fulcra are consistently paired. They are commonly present in unpaired fins of non-teleostean fishes. Among extant fishes they are absent in polypteriforms, Amia, and most teleosts. Because of their placement, structure, and phylogenetic occurrence, basal fulcra and procurrent rays are interpreted as homologous elements. Whereas “true” teleosts lack any fulcra on paired fins (a synapomorphy of the group), basal fulcra as well as fringing fulcra are described for ‘pholidophoriforms’ paired fins. Fringing fulcra are always paired. Three types of fringing fulcra series are described. Beyond the following, their distribution among actinopterygians remains unknown. The series of fringing fulcra in basal actinopterygians is formed by expanded terminal segments of marginal lepidotrichia. The series formed by a combination of expanded terminal segments of rays and independent spiny, small elements (more traditionally named as fringing fulcra) in teleosteomorphs. Only a series of spiny elements along the leading marginal fin ray(s) are found in some halecostomes. The origin and early structure of the spiny, independent fringing fulcra remain unknown.

Beyond the descriptions of new structures and reinterpretations of others, this survey has revealed new characters that support different actinopterygian groups.

Raoul J. MUTTER, Joan CARTANYÀ & Susan A. U. BASARABA. New evidence of Saurichthys from the Lower Triassic with an evaluation of early saurichthyid diversity
[pp. 103-127, 18 figs., 2 apps.]

A new Early Triassic species from the Vega-Phroso Siltstone Member of the Sulphur Mountain Formation of western Canada, Saurichthys toxolepis sp. nov., is described, and we confirm the presence of a second species, Saurichthys dayi, in the same formation. Another species from the Wordy Creek Formation of East Greenland, Saurichthys cf. S. ornatus, is introduced. Our review of the Early-Middle Triassic record of the genus Saurichthys reveals that species with striking differences in skull anatomy and squamation were already present in the Early Triassic. We briefly review saurichthyid evolution and Early-Middle Triassic paleobiogeography. Saurichthys was predominantly marine, and a significant taphonomic bias is identified in the Triassic record. The new evidence highlights the importance of often poorly dated Early Triassic saurichthyids and shows that evolutionary trends are more complex than previously believed.

Cristina LOMBARDO & Andrea TINTORI: A new semionotid fish (Actinopterygii) from the Upper Triassic of northern Italy
[pp. 129-142, 8 figs.]

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.

J. Ralph NURSALL & Luigi CAPASSO: Additional specimens from Lebanon reveal more of the structure of the pycnodont fish Trewavasia carinata (DAVIS, 1887)
[pp. 143-166, 15 figs., 4 tabs., 1 app.]

Specimens of Trewavasia carinata from private collections have revealed much more about the species. All specimens are from plattenkalk deposits near Haqel, Lebanon. T. carinata is distinguished by a horizontal frontal rostrum and a snout pointing vertically down. The snout is covered by elongated prefrontals and lateral ethmoids. Teeth are columnar in shape, with low conical crowns; the batteries of vomerine and prearticular teeth are arranged irregularly, not in orderly rows. Each premaxilla bears four teeth; each dentary bone bears five teeth. Hooked branchial teeth are well-developed. More than 30 vertebrae are present. Arcocentra extend on to the notochord, but do not surround it. Chordacentra can be seen in the precaudal vertebrae of one specimen. T. carinata is distinguished by its spiny appearance: the dermal skull is decorated sagittally with spines on its extrascapular extension and on prominent supraorbital ridges; the preoperculum bears a large spine; the cleithrum bears three large spines; many of the trunk scales, especially towards the lateral midline, bear a horizontal, median keel that terminates posteriorly in a spine. T. carinata is fully scaled except for a naked patch on the belly and an area above it bearing a series of postcleithral bones. Scales and dermal bones are densely ornamented with mammillae, which are often linearly arranged. On the basis of numerous demonstrable character differences between Coccodus and Trewavasia, the latter is removed from Coccodontidae and replaced in the family Trewavasiidae. Ichthyoceros is provisionally placed in Trewavasiidae.

Lúcio Paulo MACHADO: The braincase of Neoproscinetes penalvai (Pycnodontiformes, Pycnodontidae)
[pp. 167-180, 8 figs.]

Neoproscinetes penalvai exhibits the most well-preserved braincase among pycnodonts, however it has not yet been completely described. The braincase of N. penalvai is herein examined on the basis of new acid-prepared specimens. It is formed by a mesethmoid, orbitopterosphenoids, sphenotics, parasphenoid, prootics, supraotic, and exoccipitals, but lacks pterotics, opisthotics, intercalars, basioccipital, and epioccipitals, ossifications which are present in the other well-preserved pycnodont braincase, i.e. Mesturus sp. The remarkable preservation allowed the observation of most of the foramina for cranial nerves and blood vessels, the utricular and saccular recesses, and the grooves for the anterior and posterior semicircular canals.

Jeff LISTON: A review of the characters of the edentulous pachycormiforms Leedsichthys, Asthenocormus and Martillichthys nov. gen.
[pp. 181-198, 10 figs., 1 tab., 1 app.]

With their phyletic trend of non-ossification of their skeleton, the members of the Mesozoic neopterygian family Pachycormidae have long presented problems to systematists. Recent works on this family are revisited with additional data for Leedsichthys, Asthenocormus and Martillichthys (nov. gen.) from the Callovian Oxford Clay around Peterborough (UK). A revised diagnosis of the Family Pachycormidae is presented, along with an updated strict consensus tree for the Pachycormiformes, showing the edentulous pachycormiforms as a discrete clade.

Lionel CAVIN & Peter L. FOREY: A new tselfatiiform teleost from the Upper Cretaceous (Cenomanian) of the Kem Kem beds, Southern Morocco
[pp. 199-216, 11 figs.]

The freshwater detritic Cenomanian units of the Kem Kem beds, southern Morocco, yield a bony fish assemblage with remains of coelacanths, lungfishes, cladistia, gars, semionotids, halecomorphs and teleosts. We describe here new material comprising fragments of braincases and an almost complete skull of a new teleost. Concavotectum moroccensis gen. et sp. nov. is characterised by a deep, laterally compressed, head with a skull roof concave in lateral view and strongly arched in cross section. It shows features uncommon in teleosts, such as frontal bones wider anteriorly than posteriorly and no ascending process on the premaxilla. Other characters apomorphic for teleosts are: the antorbital is sutured to the first infraorbital, the upper jaw is edentulous (the lower jaw is incompletely known), minute teeth are found on a dentigerous plate borne by the parasphenoid. This combination of derived characters is shared in part with Bachea huilensis, from the Turonian of Colombia, and Enischnorhynchus dallasensis, from the Late Santonian-Early Campanian of the Austin Formation in Texas, USA. Both species have been referred recently to derived Tselfatiiformes. They differ from basal tselfatiiforms that have a broad skull roof composed of thick dermal bones, by a laterally compressed head and thin dermal skull roof bones. Paranogmius doederleini, from the Cenomanian Bahariya Formation in Egypt, is based on isolated cranial, vertebral and caudal elements originally housed in the Bayerische Staatssammlung für Paläontologie und Geologie, München but now lost. Because P. doederleini showed a well-preserved wide snout, it was thought to possess a wide skull roof, which was then distorted and flattened during fossilisation. This morphology would have been very different from C. moroccensis. Following the discovery of C. moroccensis, we suggest that the material of P. doederleini was not so flattened and both fishes had similar gross skull morphology. We suspect that both taxa are related, or possibly conspecific. However, on the basis of the published descriptions and figures, P. doederleini shows some differences, and because this material is now lost, the erection of a new taxon here is justified.

Yoshitaka YABUMOTO: A new Early Cretaceous osteoglossomorph fish from Japan, with comments on the origin of the Osteoglossiformes
[pp. 217-228, 11 figs., 3 apps.]

A new genus and species of osteoglossomorph fish, †Tetoriichthys kuwajimaensis is described from freshwater deposits of the Kuwajima Formation, Tetori Group, in Shiramine, Ishikawa Prefecture, Japan. This genus differs from other osteoglossomorphs by the combination of the following characters: anterior portion of frontal about 1.4 times as broad as posterior portion, anterior two-thirds of horizontal sensory canal of preopercle forming open groove and posterior one-third having four separated pores, and thick scales having almost horizontal grooves. The phylogenetic analysis using data matrices of previous cladistic studies on osteoglossomorphs suggested that †T. kuwajimaensis belongs to the Notopteridae, Osteoglossidae or basal Osteoglossiformes. This new taxon probably belongs to the Osteoglossiformes, because the parasphenoid has long teeth at the base of ascending processes, the sensory canal of the horizontal arm of the preopercle runs horizontally with its sensory canal forming an open groove, the frontal bone has a wide anterior and a narrow posterior portion, the infraorbitals are large and probably cover the cheek region, and the scales are large and thick. As the oldest record of this order, it places the origin of the Osteoglossiformes probably before the Early Cretaceous, because of the geographical and geological distribution of fossil and living species of the Osteoglossiformes.

Stephen L. CUMBAA & Alison M. MURRAY: New Late Cretaceous pachyrhizodontid and enchodontoid fishes and associated ichthyofauna from the Northwest Territories, Canada
[pp. 229-256, 21 figs., 2 tabs.]

Two new genera and species, Aquilopiscis wilsoni (Crossognathiformes: Pachyrhizodontidae) and Ornatipholis sahtu (Aulopiformes: Enchodontoidei), are described from upper Lower Turonian marine deposits at Lac des Bois, Northwest Territories, Canada. Associated with these new taxa is a diverse osteichthyan assemblage, including an unidentified caturid (Amiiformes) and several teleosts, Ichthyodectes ctenodon(Ichthyodectiformes), Osmeroides sp. (Elopiformes), Avitosmerus canadensis (Euteleostei incertae sedis), and three Aulopiformes, Enchodus gladiolus, E. petrosus, and Cimolichthys sp. These articulated vertebrates were associated with an invertebrate fauna of ammonites, inoceramid clams and squid, indicating a fully marine, open water paleoenvironment near the northern continental limits of the Western Interior Seaway. These new crossognathiform and aulopiform taxa, plus the euteleost Avitosmerus previously described from this locality, indicate that the northern portions of the Seaway were more than reasonable habitat for the evolution and diversification of teleosts in the early Late Cretaceous.

Jesús ALVARADO-ORTEGA, Ernesto OVALLES-DAMIÁN & Gloria ARRATIA. A review of the interrelationships of the order Ellimmichthyiformes (Teleostei: Clupeomorpha)
[pp. 257-278, 8 figs., 1 tab.]

A review of the interrelationships within the extinct order Ellimmichthyiformes is performed including data used by previous authors and species belonging to the genera Diplomystus, Ellimmichthys, Ellimma, Ezkutuberezi, Paraclupea, Sorbinichthys, Triplomystus, and Scutatuspinosus. Two new forms from El Espinal Quarry, Chiapas, Mexico, are included; one belongs to a new species of Triplomystus and the other has been named as Paraclupea-like. The phylogenetic hypothesis obtained involves two kinds of characters: discrete and continuous. The use of discrete characters is not sufficient to generate a completely resolved phylogenetic hypothesis. The present results support the monophyly of the order Ellimmichthyiformes with two families, the Paraclupeidae and Sorbinichthyidae fam. nov. The family Paraclupeidae includes Scutatuspinosus, Ellimma, Ezkutuberezi, Ellimmichthys, Diplomystus solignaci, Paraclupea, Paraclupea-like and Triplomystus, whereas the family Sorbinichthyidae includes Sorbinichthys and the nominal species of the genus Diplomystus, with the exception of D. solignaci. Based on this hypothesis and the paleogeographic and temporal distribution of the ellimmichthyiforms, it is suggested that the paraclupeids were an Early Cretaceous group distributed along the Megatethys, including the southeastern border of Asia, whereas the sorbinichthyids had a more eastern distribution, from Europe and the Middle East to Asia and North America, and reached their greatest diversity in the Late Cretaceous.

Paulo M. BRITO & Cesar R. L. AMARAL: An overview of the specific problems of Dastilbe JORDAN, 1910 (Gonorynchiformes: Chanidae) from the Lower Cretaceous of western Gondwana
[pp. 279-294, 8 figs.]

The gonorynchiform genus Dastilbe JORDAN, 1910 is one of the most common taxa within the Lower Cretaceous western Gondwanan fauna, being very abundant in Brazilian basins, where several nominal species had been described: D. crandalli (Sergipe-Alagoas and Araripe basins), D. elongatus (Araripe Basin), D. moraesi (Sanfranciscana Basin), and D. minor, a nomen nudum (Tucano Basin), although there is a single record for D. batai in Equatorial Guinea.

A revision of morphological features previously used to designate nominal species of Dastilbe was made using specimens from all localities. This study shows the impossibility of definitely distinguishing between different species on the basis of diagnostic morphological characters previously considered, due to their great plasticity. Therefore, we consider the species D. elongatus, D. moraesi, and D. minor as synonyms of Dastilbe crandalliJORDAN, 1910. The species D. batai is very badly preserved and therefore it is difficult to permit any precise taxonomic identification. A revised diagnosis of Dastilbe is provided. Better knowledge of the localities from which Dastilbe is known, shows that the stratigraphical range of this taxon reaches from the upper Barremian- lower Aptian to the Aptian-Albian boundary.

Terry GRANDE & Lance GRANDE. Reevaluation of the gonorynchiform genera †Ramallichthys, †Judeichthys and †Notogoneus, with comments on the families †Charitosomidae and Gonorynchidae
[pp. 295-310, 8 figs. (3 farbig), 1 tab., 3 apps.]

The morphology of the gonorynchiform genera †Ramallichthys and †Judeichthys is reviewed based on newly acquired material. Results indicate that the genera †Ramallichthys, †Judeichthys and †Hakeliosomus should be synonymized, with the name †Ramallichthys taking priority. The monophyly of the families †Charitosomidae GAYET (1993a) and Gonorynchidae SCOPOLI (1777) are reexamined. Based on our cladistic analysis, using newly acquired character information for the genus †Notogoneus, a new hypothesis of relationships is proposed in which †Notogoneus, traditionally thought to be the sister group to Gonorynchus, forms the sister group to the Gonorynchinae. Within Gonorynchinae, Gonorynchus forms the sister group to the Middle Eastern forms (i.e., †Charitosomini: including †Ramallichthys and †Charitosomus + †Charitopsis). In the interest of preserving nomenclatorial stability the family name Gonorynchidae is retained for the group, and †Charitosomini is included within the family. The family †Charitosomidae is not recognized. Additional research is needed to clarify the interrelationships within the †Charitosomus + †Charitopsis clade.

Michael G. NEWBREY, Mark V. H. WILSON & Allan C. ASHWORTH: Climate change and evolution of growth in Late Cretaceous to Recent North American Esociformes
[pp. 311-350, 12 figs., 3 tabs., 4 apps.]

Relationships between climate change, growth characteristics (i.e., longevity, rate of growth, and maximum total length), and evolution are examined for Mesozoic, Cenozoic, and extant taxa of North American Esociformes. The proposition that temperature influenced speciation within Esocoidei, including the genus Esox, is supported by several findings: 1) Cretaceous esocoids have smaller centra and very different growth characteristics than Esox occurring after the K-T boundary; 2) a significant relationship exists between mean annual temperature and longevity for Tertiary Esox; 3) significant differences between growth characteristics of extinct and extant taxa indicate adaptations of fossil taxa for warmer climates; and 4) the latitudinal distribution of Tertiary Esox is positively correlated with temperature, except during the Early Eocene Thermal Maximum (EETM). The hypothesis that E. (Kenoza) evolved during the EETM is supported by: 1) early Eocene appearance of E. (Kenoza) osteology in E. kronneri; 2) similarity of the interaction of longevity and growth rate between E. (Kenoza) and some Paleocene and early Eocene fossils; 3) interpretation that early Eocene Esoxfrom the Green River and Coalmont Formations inhabited temperatures exceeding those recorded for extant E. (Esox); and 4) latitudinal discontinuity in the distribution of Esox at the EETM when E. kronneri appeared. The comparison of Cretaceous esocoids to extant umbrids suggests that the small size of umbrids is a primitive feature in Esocoidea. The larger size of extant E. (Esox) is interpreted as being derived for esocoids but a condition that is primitive for the genus.

Valéria GALLO & Pablo M. COELHO: First occurrence of an aulopiform fish in the Barremian of the Sergipe-Alagoas Basin, northeastern Brazil
[pp. 351-371, 12 figs.]

In this paper, we describe the first Brazilian aulopiform fossil fish, Atolvorator longipectoralis gen. et sp. nov., from the Coqueiro Seco Formation, Barremian of the Sergipe-Alagoas Basin, northeastern Brazil. It is a medium-sized fish reaching about 45 cm standard length. It exhibits among other characters: dermal bones of skull roof and opercular series smooth; lateroparietal skull roof; unroofed posttemporal fossa; absence of interopercle; premaxilla and maxilla included in mouth gape; large and extremely stout tooth near symphysis; flange on the anguloarticular; and fusion of first plus second and third plus fourth hypurals. The presence of parietal with an elliptical shape, dentary bearing rows of minute densely padded-teeth, vertebral column with 47 vertebrae, less than half being caudal, and dorsal fin remote were considered putative autapomorphies of the new taxon. It is superficially more similar to Cimolichthyidae and Serrilepidae, differing from those by relevant anatomical details.

Christopher FIELITZ & Katia GONZÁLEZ RODRÍGUEZ: A new species of Ichthyotringa from the El Doctor Formation (Cretaceous), Hidalgo, Mexico
[pp. 373-388, 10 figs., 2 apps.]

A new species of Ichthyotringa (Teleostei: Aulopiformes), Ichthyotringa mexicana, from the Muhi quarry near the town of Zimapán, Hidalgo, México is described. Thirteen specimens were examined. Preservation of individuals is poor, however, there is one complete specimen. I. mexicana n. sp. exhibits ichthyotringid characters such as a long, tapering rostrum; unornamented dermal bones of the skull roof; long mandible with a low coronoid process; and vertebral centra that are longer than deep. It differs from other species of Ichthyotringa by having a head comprising over one-half standard length; minute, pebble-like teeth on the ectopterygoid and endopterygoid; repeating pattern of small and large teeth on the premaxilla and maxilla; a preopercle with a posterior spine; and the absence of scales. A phylogenetic analysis of I. mexicana n. sp., Apateodus striatus, Apateopholis laniatus, I. delicata, I. furcata, and Yabrudichthys striatus suggests that 1) the Ichthyotringoidei is a monophyletic group, 2) Yabrudichthys is included in the group, and 3) Ichthyotringa is not monophyletic if Apateodus is included in the phylogeny. Only larger specimens of I. mexicana n. sp. have been found. Other teleost species represented at the Muhi quarry include juvenile forms. It is possible that I. mexicana n. sp. fed on these juveniles.

Alberto BLANCO, Jesús ALVARADO-ORTEGA & Valéria GALLO: Robertichthys riograndensis from the Lower Turonian (Upper Cretaceous) Vallecillo Lagerstätte, NE-Mexico: Description and relationships
[pp. 389-397, 5 figs., 2 tabs.]

A complete description, as the preservation permits, as well as a discussion of the relationships of Robertichthys riograndensis BLANCO-PIÑÓN & ALVARADO-ORTEGA, 2005 from the Vallecillo Member (Agua Nueva Formation: Lower Turonian), at Vallecillo, Mexico are provided. The diagnostic character present in R. riograndensis, as the anteroposterior increasing of the crown height of the teeth on lower jaw, allows us to emend the diagnosis of the family Dercetidae. The cladistic analysis revealed that Robertichthys is an unquestionable member of the family, and it is located after Pelargorhynchus and Cyranichthys at the base of the phylogeny. Additionally, the occurrence of this dercetid fish expands the distribution and increases the diversity of the family in southern North America within the domain of the North Proto-Atlantic during the Turonian.

Katia GONZÁLEZ RODRÍGUEZ & Christopher FIELITZ: A new species of acanthomorph fish from the Upper Cretaceous Muhi Quarry, Hidalgo, Central Mexico
[pp. 399-411, 7 figs.]

A new species of acanthomorph fish, Muhichthys cordobai gen. et. sp. nov., from the Muhi quarry (Albian-Cenomanian), Hidalgo State, Mexico, is described. This is the first confirmed record of a fossil acanthomorph fish in Mexico. Four specimens were examined, including one adult specimen and three poorly preserved juveniles. It has a small, deep, compressed body with a high supraorbital crest originating behind the orbit; no developed mucus cavities; head without strong ornamentation; toothless palatine; one supramaxilla; pelvic fin without spine; dorsal fin covering almost the entire length of the body, predorsal formula /0/0/0/1 + 1 + 1/1/; and ventral ridge scales present. Due to the combination of plesiomorphic and derived characters that it shares with the Cretaceous polymixiids, trachichthyoids, and holocentrids, it is not possible to establish its phylogenetic position among acanthomorph taxa, therefore the fish is interpreted as an acanthomorph incertae sedis.

Guntupalli V. R. PRASAD, Kulwant SINGH, Varun PARMAR, Anjali GOSWAMI & Charan S. SUDAN: Hybodont shark teeth from the continental Upper Triassic deposits of India
[pp. 413-432, 5 figs., 2 tabs.]

The continental Upper Triassic Maleri and Tiki Formations of peninsular India were prospected for microvertebrate yielding-horizons. This led to the delineation of 10 microvertebrate-producing sites in the red clays of the Maleri Formation and one site in the Tiki Formation. Of these, one site each from the Maleri and Tiki Formations has yielded freshwater hybodont shark teeth. In the present paper, the hybodont fauna recovered from each of these sites is described. The fauna from the Tiki Formation includes four new species, Lonchidion estesi sp. nov., L. incumbens sp. nov., Lissodus duffini sp. nov., and Parvodus tikiensis sp. nov., while the Maleri Formation yielded Polyacrodus ?contrarius as well as a few unidentified taxa. This is the first report of hybodont sharks belonging to the Lonchidiidae and the Polyacrodontidae from the Triassic of India.

Charlie J. UNDERWOOD & David J. WARD: A review of the Mesozoic Record of the Carcharhiniformes
[pp. 433-442, 2 figs.]

Although the Carcharhiniformes represent one of the most diverse and important groups of sharks alive today, their early history is very poorly known. Reinterpretation of previously figured Jurassic and Cretaceous fossils, along with collection of new specimens from the Cretaceous of the British Isles, has allowed the early record of this order to be reinterpreted. Whereas members of only one carcharhiniform family have been previously recorded from the Jurassic, and two from the Cretaceous, it is considered here that fossils of two families are known from Jurassic rocks, and at least five families from the Cretaceous. The relative timing of familial appearances is consistent with the predictions derived from cladistic analyses, although some of the cladogenic events can now be shown to have been earlier than previously recognised.

Jürgen KRIWET: A Late Jurassic carpetshark (Neoselachii, Orectolobiformes) from southern Germany
[pp. 443-454, 5 figs.]

A new carpetshark, †Palaeorectolobus agomphius gen. et sp. nov., is described from the Upper Jurassic lithographic limestones of southern Germany. The single specimen consists of an incompletely fossilized skeleton including portions of the head, dentition, branchial apparatus, and left pectoral fin. The shoulder girdle is imperfect and only the articular region for the pectoral radials is preserved. All skeletal elements are covered by prismatic calcifications obscuring most of the details. The most conspicuous feature is the presence of short and heavily branched dermal lobes along the lateral margin of the head. This is characteristic for orectolobid sharks. The dental pattern, conversely, is more similar to carcharhiniforms. A hemiaulacorhize root, typical for orectolobiforms, and a low stout, subtriangular crown characterises the teeth. Anterior teeth are devoid of lateral cusplets, and lateral teeth generally display a small and incipient distal cusplet. The crown ornamentation consists of occasional well-developed vertical folds which originate from a transversally oriented labial crest and do not reach the apex. The combination of dermal lobes and the peculiar dental morphology is autapomorphic for this taxon. The dermal lobes identify the specimen unambiguously as a member of the Orectolobiformes. A designation to any known orectolobiform family is, however, currently impossible due to the mosaic of anatomical features.

Stefanie KLUG, Jürgen KRIWET, Juan M. LIRIO & Hector J. NUÑEZ: Synechodontiform sharks (Chondrichthyes, Neoselachii) from the Upper Cretaceous of Antarctica
[pp. 455-467, 3 figs.]

The taxonomy of Upper Cretaceous synechodontiform sharks from the James Ross Basin, northern Antarctica, is reviewed. All material is from the Santa Marta Formation (late Coniacian – latest Campanian) of James Ross Island and contributes significantly to our knowledge of synechodontiform diversity and biogeographic patterns. Synechodontiforms are represented by two taxa, Sphenodus and Paraorthacodus. The teeth of the Antarctic Sphenodus species differ from most known species assigned to this genus. However, the imperfect preservation does not allow any specific identification of this Antarctic shark. The size of its teeth indicates that this shark probably measured at least 5 m in total length. A new species, Paraorthacodus antarcticus, is introduced. Paraorthacodus is confined to the Santa Marta Formation (Santonian to early Campanian Lachman Crags and late Campanian to early Maastrichtian Herbert Sound members), whereas Sphenodus occurs in the Herbert Sound Member and the Maastrichtian López de Bertodano Formation. The occurrence of synechodontiform sharks in the James Ross Basin correlates with an interval of enlargement of the trans-equatorial Tethyan seaway within the Coniacian-Maastrichtian interval. The absence of all synechodontiforms in Antarctica after the K/T boundary, conversely, concurs with a drop in surface water temperatures.

Marcelo R. de CARVALHO, Jürgen KRIWET & Detlev THIES: A systematic and anatomical revision of Late Jurassic angelsharks (Chondrichthyes: Squatinidae)
[pp. 469-502, 17 figs. (1 farbig), 1 app.]

The skeletal and dental anatomy of the Late Jurassic squatinoids of southern Germany are reviewed and their relationships with living angelsharks and other neoselachians are discussed in light of new anatomical data. Two Late Jurassic angelshark species, differing mainly in size, body proportions, and dental morphology, are recognized: †Squatina alifera (MÜNSTER, 1842) from Solnhofen and †Squatina acanthoderma (FRAAS, 1854) from Nusplingen. †Squatina speciosa (MEYER, 1856), also from Solnhofen and commonly regarded as valid, is considered a junior synonym of †S. alifera concurring with recent studies of their teeth. The available nominal genus †Pseudorhina JAEKEL, 1898 is resurrected for †S. alifera and †S. acanthoderma, and may include other Jurassic taxa based on isolated teeth. †Pseudorhina is hypothesized to be monophyletic based on its derived, conspicuously-shaped basihyal cartilage and dental root structure. Comparisons with the skeletal anatomy of extant angelsharks are provided, revealing that the Jurassic holomorphic fossils are markedly conservative and similar to living angelsharks, but that they differ in various respects (e.g. configuration of orbital roof and postorbital processes, positioning of foramina in the ethmoid region). †Pseudorhina shares with extant Squatinavarious derived features, including a marked groove in the cranial roof that accommodated the orbital process of the palatoquadrate, a distinctive quadrate process of the palatoquadrate having no suspensory function, basally triangular lower labial cartilages, expanded anterior basiventrals, slender and anteriorly concave puboischiadic bar, and triangular and anteriorly extending pectoral fin lobes; some of these features are independently derived in other neoselachian lineages. †Pseudorhina retains the basal hypnosqualean condition of low and tightly articulated platelike supraneurals, corroborating that the more slender, taller and widely spaced supraneurals of living Squatina species are derived. †Pseudorhina represents an extinct lineage of Jurassic angelsharks that may have survived until later in the Mesozoic as implied by the occurrence of †Pseudorhina-like teeth in strata younger than the Jurassic. This, in turn, implies that while one lineage of angelsharks underwent extinction sometime in the mid-Mesozoic, another and perhaps slightly younger angelshark lineage flourished and survives to the present.

As in the previous volumes of Mesozoic Fishes, we begin by stating that “The Mesozoic was an important time in the evolution of chondrichthyan and actinopterygian fishes because it was then that most modern groups first entered the fossil record and began to radiate.” Gloria ARRATIA initiated the international meeting “Mesozoic Fishes” in August of 1993 in Eichstätt, and the first book, “Mesozoic Fishes - Systematics and Paleoecology”, was published in 1996. The next meetings followed in 1997 in Buckow (organizers: Gloria ARRATIA and Hans-Peter SCHULTZE), 2001 in Serpiano (organizers: Andrea TINTORI, Markus FELBER, and Heinz FURRER), and 2005 in Miraflores de la Sierra (organizer: Francisco J. POYATO-ARIZA). Each of these meetings was followed by the publication of a book, so that “Mesozoic Fishes 2 - Systematics and the Fossil Record” was published in 1999, and “Mesozoic Fishes 3 - Systematics, Paleoenvironments and Biodiversity” was published in 2004. The editors of these books included the principal organizer of the meeting and Gloria ARRATIA.

The content of the first three books on Mesozoic fishes reveals some patterns in the research on Mesozoic fishes. Studies concerning the phylogenetic relationships of different fish groups often include both fossil and recent fishes so that the studies are not restricted only to Mesozoic forms. Almost all of these studies have been based on morphological evidence; however, papers dealing with specific morphological structures have also been welcomed in previous books. The majority of researchers are involved in work on Mesozoic actinopterygians, whereas fewer study Mesozoic chondrichthyans, and even fewer study sarcopterygians. Among the actinopterygians, subjects of studies vary from basal neopterygians to teleosts. Descriptions of new taxa, as well as new information concerning oldest records for different fish groups, are important components of “Mesozoic Fishes”.

The present book offers some major changes in comparison to previous volumes. Most contributors to Mesozoic Fishes prefer that the meetings and books be separate events and that the series of books be managed by permanent editors. The content of this and subsequent books will be mainly based on the papers presented at the meetings, but not exclusively, in that some colleagues may be invited by the editors to write specific chapters. Experience has shown that despite the title of the meetings (and of the books), most papers concern systematics. The titles of previous meetings included other subjects, such as paleoenvironment and paleoecology, that are important to develop within the framework of Mesozoic fishes, but yielded almost no response from the participants; such a deficiency created a conflict between the title of the earlier volumes and their contents. Therefore, the title of the Fourth International meeting, “Mesozoic Fishes 4 - Systematics, Homology, and Nomenclature”, has not been retained for the present book because most papers in this volume deal with fish systematics and take a conservative approach to the interpretations of structures and to the nomenclature employed. Apparently, the position of many colleagues is that tradition should be maintained regardless of the progress in understanding of homologies that is made in their science. However, despite this general preference, three papers in this book deal with the concepts of homology, philosophical principles, and their application.

“Mesozoic Fishes 4 - Homology and Phylogeny” captures the current state of knowledge on Mesozoic fishes and illustrates the trends among fish workers in their areas of study. Although the number of contributions on chondrichthyans and actinopterygians has risen steadily, no new information on sarcopterygians is included. More than 10 new taxa are described and a few others are revised. For the first time, descriptions of new fossil neoteleosts are presented.