Review

COPEIA, 18 Feb. 1997 No. 1: 244-246

DEVONIAN FISHES AND PLANTS OF MIGUASHA, QUEBEC, CANADA,

By H.-P Schultze and R. Cloutier (eds.): Verlag Dr Friedrich Pfeil, München, 1996. 374 pp. $52.00 (hardback).

While the major part of this book addresses the fossil fauna of the Escuminac Formation at Miguasha, which includes 19 genera and 21 species, it probably should have included a subtitle referring to the thorny issue of the environmental setting of the formation; a topic first mentioned in the Preface (Chapter 1) and subsequently becoming a recurring theme. Many of the taxonomic chapters are updates of previously described specimens, reflecting the collection of new material and improved understanding of fossil vertebrates, which has developed from the dedicated work carried on at this site since it became a Provincial Park in 1985. The book is developed in part from the impetus resulting from an International Lower Vertebrate meeting held there in 1991, and organized in five parts: Historical Overview, Geology, Paleobotany, Paleozoology, Invertebrates, and Paleozoology, Vertebrates.

Part I (Chapter 2) provides a detailed historical overview. It includes the names of collectors at this locality and repositories of the material, as well as a comprehensive list of publications of Miguasha material. The latter is certainly helpful to a student interested in previous descriptions of the material. The list of now well known scientists involved in the studies at the Miguasha locality is an impressive one and attests to the continuing importance of this site.

Part II (Chapters 3-6) is of particular interest as an innovative approach to the problem of interpreting ancient environments through the use of interdisciplinary studies. In Chapter 3 (Prichonnet et al.), a detailed lithological and sedimentological description leads the authors to conclude that the Escuminac Formation is made up of turbidite sequences and laminated facies, which occur in at least four units, and are associated with deposition during warm and cold seasons. Among the invertebrates, they note the total absence of typical Devonian marine groups, a picture also mirrored by the vertebrates, suggesting to them that the environment of deposition could have been similar to that of the Battery Point Formation, which was deposited in an estuarine setting subject to periodic marine incursions (Pageau and Prichonnet, 1976).

A paleogeographical reconstruction of the eastern North American continent during Devonian time by means of paleomagnetic studies is attempted in Chapter 4 (Seguin). The author points out that paleomagnetic data for the Paleozoic is scarce and remagnetization, overprints, and insufficient data present problems. Despite these difficulties, an effort is made to provide implications for the presence (or absence) of a marine basin at this locality during the time of deposition of the Escuminac, concluding that around the Middle Devonian the Central Mobile Belt, which included the present day Miguasha locality, had accreted to the North American cratonic landmass. Although not stated, one has to presume that this annexation would have eliminated marine influences.

Chidiac (Chapter 5) uses geochemical analysis to show that while boron concentrations in the shales suggest a setting intermediate between fresh and salt-water, the isotopic composition of oxygen and carbon in the carbonates is similar to Devonian marine conditions. The author proposes that the Escuminac Formation is of marine or brackish rather than lacustrine origin.

Chapter 6 (Parent and Cloutier) includes a good overview of fossil occurrence and preservation, and it does answer some of the questions about fossil distribution within the formation, a problem that seems to have been ignored in some of the later chapters. A single temporal paleocommunity is proposed although community structure changed through time in an estuarine environment. Thus part II comes to no clear conclusions about the environment of deposition.

Part III addresses the paleobotany of the Escuminac Formation. Gensel and Barnett-Lawrence (Chapter 7) take particular note of the low diversity and abundance of the plant megafossils compared to the dispersed spore assemblage. The material is mostly abraded and weathered, but typical of the Late Devonian and unknown prior to the Frasnian. As these are land plants, they must have been transported to shoreline or brackish/marine environments. There are problems with the proper stratigraphic horizon assignments of earlier studies, a theme running through the book, due to the methods of collecting employed in the past. The two plant-bearing horizons contain a very different flora, suggesting that changes in plant composition occurred over time. McGregor (Chapter 8) also proposes that the spores were of terrestrial origin and were not carried far from land. The assemblage does not include marine palynomorphs. The spores are much more diverse than the megaflora, implying that they reflect a greater proportion of the Frasnian regional vegetation.

The invertebrates of the Escuminac Formation are described in Part IV. The chelicerates (Chapter 9, Jeram) include both scorpion and eurypterid material. Their presence adds to the importance of the Escuminac Formation, because of the scarcity of these invertebrates in the fossil record. Jeram points out that while chelicerates were initially marine, by the Late Carboniferous scorpions had made the transition onto land, while eurypterids moved into freshwater environments. In Chapter 10 Martens describes the Conchostraca, small phyllopod crustaceans, which are primarily known from temporary freshwater pools and somewhat brackish environments, such as ponds and lakes with fluctuating water levels. They ranged from the Lower Devonian through the Holocene.

Trace fossils are covered in Chapter 11 (Maples). The author proposes that the low diversity assemblage of ichnofossils may indicate stressed environmental conditions, such as an estuarine setting, where salinity and turbidity changes were not suitable for a diverse fauna. The trace fossils occur in plant-rich mudstone units, in which well preserved, articulated body fossils are rare or absent. Interestingly, much of the material previously referred to trace fossils is here re-interpreted as sedimentary structures. It is suggested that the basin was, at least during part of the deposition, connected to a somewhat distant open sea.

Part V is devoted to the vertebrates, the group for which the formation is best known. Chapter 12 (Schultze) is a brief review of the known vertebrates and their phylogenetic relationships, and is also a useful reference guide to the remaining chapters. The vertebrates are treated in taxonomic sequence with Janvier and Arsenault (Chapter 13) starting with the agnathans, represented by the Osteostraci. Although rare in the Escuminac Formation, the locality is an important one, since to date these are the latest known osteostracans. Originally assigned to four different species, the authors suggest that there may possibly be only three species (Alaspis rosamundae, Escuminaspis laticeps, Osteostraci, gen. et sp. indet.) of which one, Escuminaspis laticeps, may be a juvenile of A. rosamundae. The phylogenetic affinity is somewhat obscure, which may be due to the endemic nature of the fishes. In Chapter 14 Janvier addresses the Miguasha "Anaspida." Although two species Endeiolepis aneri and Euphanerops longaevus, have been traditionally assigned to the anaspids on the basis of the hypocercal tail, the author shows that they are probably not anaspids, suggesting instead that they may be more closely related to lampreys.

Only two placoderms are present in the Escuminac Formation (Chapter 15, Vezina); the antiarch Bothriolepis canadensis and the arthrodire Plourdosteus canadensis. The genus Bothriolepis occurs throughout the formation and it would have been helpful to provide information indicating if the species described here had been collected from more than one horizon. A redescription of three acanthodian species – Diplacanthus horridus, Triazeugacanthus affinis and Homalacanthus concinnus - is given in Chapter 16 (Gagnier) and a new species Diplacanthus ellsi is added. Only one actinopterigian – Cheirolepis canadensis – is known from the Escuminac Formation (Chapter 17, Arratia and Cloutier). Middle to Late Devonian actinopterigians are not diverse. They are known from only a few complete skeletons and have been reported mostly from scales found in micro assemblages. This paper extensively discusses problems with terminology, which is a useful addition.

The dipnoans (Chapter 18) and actinistans (Chapter 19) are both discussed by Cloutier. Two dipnoans, Scaumanacia curta and Fleurantia denticulata are described, based on new material, and it is concluded that previous reconstructions of the skull roof and cheek region were incorrect. Both genera are only known from the Escuminac Formation. Again intraspecific variations appear to be common. Although stratigraphic horizons are given for F. denticulata, they are absent for S. curta. While the phylogeny is discussed at length, a cladogram would have been helpful. Devonian actinistians are rare and not diverse and Miguashaia bureaui was originally described by Schultze (1984) from a juvenile specimen. Cloutier's redescription is based on adult specimens and highlights the description problem that can be caused by ontogenetic variations. Miguashaia bureaui differs from other actinistians on the basis of several characters, including the presence of an intertemporal and a heterocercal tail, and is considered by Cloutier to be one of the most primitive actinistians.

The porolepiform fishes (Chapter 20, Cloutier and Schultze) of the Escuminac Formation include three species. Quebecius quebecensis is redescribed based on new skull material. Although Holoptychius sp. had been previously illustrated and partially described by numerous workers, it is re-diagnosed and named H. jarviki in this paper based on additional material. A second holoptychiid species has only recently been discovered and has not yet been prepared to the point where it could be described.

The most famous member of the fauna, Eusthenopteron foordi, is treated quite briefly in Chapter 21 (Cloutier) with a short morphological description and a systematic overview. However, an extensive literature survey is included, keying the interested researcher in to the enormous amount of work that has been carried out on this animal.

Chapter 22 (Jarvik) is essentially a memoir of the author's work with the Escuminac Formation together with that of many of the Swedish group of workers involved. It is in itself a rather fascinating description of the decades of work involved, including an account of the serial grinding of a specimen of Eusthenopteron foordi and the detailed reconstruction of internal morphological structures that this technique allowed. Apparently it took about 25 years to complete the grinding series. An abundance of illustrations accompanies the description. Although Jarvik's hypothesis of a diphyletic origin for amphibians based on morphological criteria is no longer accepted, one is hard-pressed to find fault with some of the reasoning. The paper is written in an anecdotal style, which is a refreshing contrast to the more terse style found throughout the rest of the book.

A redescription of the elpistostegid, Elpistostege watsoni, is given in Chapter 23 (Schultze). As the closest relative to tetrapods, found in the Escuminac Formation, this arguably the most important vertebrate in the fauna. Originally considered to be an amphibian (Romer, 1947, 1966; Camp and Allison, 1961), additional material has shown it to be a fish (Schultze and Arsenault, 1985). However, it should be noted that the description is still based on incomplete material and much of the interpretation is based on the better known Panderichthys, an elpistostegid from the Baltic. Comparison with Recent amphibious fishes and tetrapods is used to suggest an intertidal environment for the Escuminac.

Coprolitic (and cololitic) remains are discussed in Chapter 24 (McAllister). Although information on coprolitic material from the Escuminac Formation is limited, what is present is of extreme interest and the author uses it to determine interactions of the fossil fauna. Some interesting hypotheses are proposed regarding behavior of fishes, prey selection, variety of prey and relationship of coprolites to sediments, such as sediment consistency, postdepositional consolidation and clues to superposition. The author also addresses the problem of identifying coprolitic remains and the difficulty of finding modern analogs, which are not often observed. It is suggested that the external and internal morphology of Paleozoic fishes may have been different from those of modern fishes resulting in consolidation of pellets, a condition less frequent in Recent samples. Cololite examples include Denison's (1941) work on sectioned specimens of Bothriolepis canadensis used by him to reconstruct the internal anatomy of this antiarch, and a Homalacanthus specimen found inside Eusthenopteron (Arsenault, 1982). The final chapter of the book (Chapter 25, Schultze and Cloutier) deals with the comparison of the ichthyofauna from the Escuminac Formation with other late Givetian to early Frasnian faunas. Despite the fact that the Escuminac Formation fauna is highly endemic, it is an interesting and illuminating attempt to correlate taxa at the generic and familial level to depict the environment of deposition for the Escuminac Formation fauna. They conclude that based on 40 late Givetian to early-middle Frasnian localities, the Escuminac includes a coastal marine to brackish water faunal assemblage.

One of the problems I encountered, especially in descriptions of species, was that no consideration was given to the time frame of sediment accumulation. The problem is of course aggravated by early indiscriminate collection methods. It is notable that recently collected specimens have horizon data, while the descriptions of Bothriolepis, Scaumenacia, and Eusthenopteron lack such stratigraphical data. The more precise methods of the Parc de Miguasha staff including stratigraphic level of collecting may eventually make it possible to address this problem.

Regarding the lack of agreement among various authors concerning the environment of deposition, the time factor may again be important. Environments can change or fluctuate over thousands of years and the Upper Devonian was a time of sea-level changes (Johnson et al., 1985; Johnson and Sandberg, 1988) especially considering the accretionary events described in Chapter 4. Therefore marine influences may have varied over time. A minor problem present in the book is the rather frequent occurrence of typographic errors, which detracts from the smooth reading of the text. However, since many of the authors use English as their second language and the book was typeset in Germany, this may be an understandable problem.

Once I started reading the book I became submerged in the topic and would recommend it not only to students of Paleozoic fossils but anybody attempting to reconstruct ancient environments. The chapters in part II (Geology) of the book are of particular interest. A number of authors interested in interpreting the environment of deposition use different approaches trying to solve the problem. Although the results differ, it still demonstrates the value of interdisciplinary studies. The Paleobotany (Part II) and Paleozoology (Parts IV and V) are important updates of a fauna which has been studied since the late 1800s. New discoveries and better methodologies have resulted in improved knowledge and several re-descriptions of species. Hopefully it is also an admonition to fossil collectors to obtain as much data as possible, especially regarding stratigraphic horizons during field work. Inadequate collecting methods are the bane of any scientist and regrettably many of us will have to deal with this problem for many years to come. I commend the staff at Parc de Miguasha for their efforts and certainly look forward to seeing the results of the ongoing work. On the whole the book is an integrated approach to look at all aspects of a faunal assemblage, rather than isolated components.

LITERATURE CITED

Arsenault, M. 1982. Eusthenopteron foordi, a predator on Homalacanthus concinnus from the Escuminac Formation, Miguasha, Quebec. Canadian Journal of Earth Sciences 19: 2214-2217.

Camp, C. L., and H. J. Allison. 1961. Bibliography of fossil vertebrates 1949-1953. Geological Society of America Memoir 84: 532 p.

Denison, R. H. 1941. The soft anatomy of Bothriolepis. Journal of Paleontology 15: 553-561.

Johnson, J. G., G. Klapper, and C. A. Sandberg. 1985. Devonian eustatic fluctuations in Euamerica. Geological Society of America Bulletin 96: 567-587.

- , and C. A. Sandberg. 1988. Devonian Eustatic Events in the Western United States and their Biostratigraphic Responses; pp. 171-178 in N. J. McMillan, A. F. Embry, and D. J. Glass (eds.), Devonian of the World, Vol. I. Regional Synthesis. Canadian Society of Petroleum Geologists, Memoir 14.

Pageau, Y., and G. Prichonnet. 1976. Interprétation de la paléontologie et de la sédimentologie d'une coupe géologique dans la Formation de Battery Point (Dévonien moyen), Gres de Gaspé National Canada, 103: 111-118.

Romer, A. S. 1947. Review of the Labyrinthodontia. Bulletin of the Museum of Comparative Zoology, Harvard College 99: 1-368.

- 1966. Vertebrate Paleontology, 3rd ed. University of Chicago Press, Chicago, Illinois, 468 pp.

Schultze, H.-P 1984. Juvenile specimens of Eusthenopteron foordi Whiteaves, 1881 (osteolepiform rhipidistian, Pisces) from the Late Devonian of Miguasha, Quebec, Canada. Journal of Vertebrate Paleontology 4: 1-16.

- , and M. Arsenault 1985. The panderichthyid fish Elpistostege: a close relative of tetrapods? Palaeontology 28: 293-309.

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